Common Attack Pattern Enumeration and Classification

Common Attack Pattern Enumeration and Classification

6

High

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

• Injection

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.

• Never Use Input as Part of a Directive to any Internal Component

Penetration

G. Hoglund and G. McGraw. Exploiting Software: How to Break Code. Addison-Wesley, February 2004.