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CAPEC-250: XML Injection

 
XML Injection
Definition in a New Window Definition in a New Window
Attack Pattern ID: 250
Abstraction: Standard
Status: Draft
Completeness: Complete
Presentation Filter:
+ Summary

An attacker utilizes crafted XML user-controllable input to probe, attack, and inject data into the XML database, using techniques similar to SQL injection. The user-controllable input can allow for unauthorized viewing of data, bypassing authentication or the front-end application for direct XML database access, and possibly altering database information.

+ Attack Execution Flow
Explore
  1. Survey Application:

    Attack Step Techniques

    IDAttack Step Technique DescriptionEnvironments
    1

    Spider web sites for all available links.

    env-Web
    2

    Gather results for analysis via responses or network sniffing.

    env-ClientServer env-Peer2Peer env-CommProtocol

    Outcomes

    IDTypeOutcome Description
    1Success
    At least one data input to application identified.
    2Failure
    No inputs to application identified, although this does not mean the application will not accept any.
Experiment
  1. Test user-controllable inputs for injection:

    Attack Step Techniques

    IDAttack Step Technique DescriptionEnvironments
    1

    Use XML reserved characters or words, possibly with other input data to attempt to cause unexpected results

    env-Web

    Indicators

    IDTypeIndicator DescriptionEnvironments
    1Negative

    Attacker receives normal response from server.

    env-Web env-ClientServer env-Peer2Peer env-CommProtocol
    2Positive

    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
    3Negative

    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

    Outcomes

    IDTypeOutcome Description
    1Success
    At least one user-controllable input susceptible to injection found.
    2Failure
    No user-controllable input susceptible to injection found.
+ Attack Prerequisites
  • XML queries used to process user input and retrieve information stored in XML documents

  • User-controllable input not properly sanitized

+ Typical Likelihood of Exploit

Likelihood: High

+ Methods of Attack
  • Injection
+ Examples-Instances

Description

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.

+ Attacker Skills or Knowledge Required

Skill or Knowledge Level: Low

An attacker must have knowledge of XML syntax and constructs in order to successfully leverage XML Injection

+ Resources Required

None

+ Probing Techniques

The attacker tries to inject characters that can cause an error, such as single-quote (') or equal sign (=), or content that may cause a malformed XML 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.

+ Indicators-Warnings of Attack

Too many exceptions generated by the application as a result of malformed queries

+ Solutions and Mitigations

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 XML data or a query.

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.

+ Attack Motivation-Consequences
ScopeTechnical ImpactNote
Confidentiality
Access_Control
Authorization
Gain privileges / assume identity
Confidentiality
Read application data
+ Injection Vector

User-controllable input used as part of XML queries

+ Payload

XML expressions intended to reveal information or bypass authentication

+ Activation Zone

XML database

+ Payload Activation Impact

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.

+ Relevant Security Requirements

Special characters in user-controllable input must be escaped before use by the application.

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.

+ Purposes
  • Penetration
  • Exploitation
+ CIA Impact
Confidentiality Impact: HighIntegrity Impact: HighAvailability Impact: Medium
+ Technical Context
Architectural Paradigms
Client-Server
SOA
Frameworks
All
Platforms
All
Languages
All
+ References
[R.250.1] [REF-3] "Common Weakness Enumeration (CWE)". CWE-91 - XML Injection. Draft. The MITRE Corporation. 2007. <http://cwe.mitre.org/data/definitions/91.html>.
[R.250.2] [REF-3] "Common Weakness Enumeration (CWE)". CWE-20 - Input Validation. Draft. The MITRE Corporation. 2007. <http://cwe.mitre.org/data/definitions/20.html>.
[R.250.3] [REF-3] "Common Weakness Enumeration (CWE)". CWE-390 - Improper Error Handling. Draft. The MITRE Corporation. 2007. <http://cwe.mitre.org/data/definitions/390.html>.
+ Content History
Submissions
SubmitterOrganizationDateSource
CAPEC Content TeamThe MITRE Corporation2014-06-23Internal_CAPEC_Team
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Page Last Updated or Reviewed: May 01, 2017