Difference between revisions of "Direct Static Code Injection"

Revision as of 01:19, 14 September 2008

This is an Attack. To view all attacks, please see the Attack Category page.

Last revision: 09/14/2008

Description

A Direct Static Code Injection attack consists of injecting code directly onto the resource used by application while processing a user request. This is normally performed by tampering libraries and template files which are created based on user input without proper data sanitization. Upon a user request to the modified resource, the actions defined in it will be executed at server side in the context of web server process.

Server Side Includes is considered a type of direct static code injection. It should not be confused with other types of code injection, like XSS (“Cross-site scripting” or “HTML injection”) where the code is executed on the client side.

Risk Factors

TBD

Examples

Example 1

This is a simple example of exploitation of a CGISCRIPT.NET csSearch 2.3 vulnerability, published on Bugtraq ID: 4368. By requesting the following URL to the server, it’s possible to execute commands defined on the ‘’’’setup’’’ variable.

csSearch.cgi?command=savesetup&setup=PERL_CODE_HERE

For the classical example, the following command can be used to remove all files from “/” folder: csSearch.cgi?command=savesetup&setup=`rm%20-rf%20/`

Note that the above command must be encoded in order to be accepted.

Example 2

This example exploits a vulnerability on Ultimate PHP Board (UPB) 1.9 (CVE-2003-0395), which allows an attacker to execute random php code. This happens because some user variables, like IP address and User-Agent, are stored in a file that is used by the admin_iplog.php page to show user statistics. When an administrator browses this page, the previously injected code by a malicious request is executed. The following example stores a malicious PHP code that will deface the index.html page when an administrator browses admin_iplog.php.

GET /board/index.php HTTP/1.0
User-Agent: <? system( "echo \'hacked\' > ../index.html" ); ?>

Related Threat Agents

• Internal software developer

Related Attacks

• Server Side Includes
• Direct Dynamic Code Evaluation ('Eval Injection')

Related Vulnerabilities

• Category:Input Validation Vulnerability

Related Controls

• Category:Input Validation

References

• http://www.seclab.tuwien.ac.at/advisories/TUVSA-0510-001.txt
• http://marc.info/?l=bugtraq&m=105379741528925&w=2
• http://archives.neohapsis.com/archives/bugtraq/2005-06/0002.html