*Advisory Information*

Title: Astaro Security Gateway - bypass using whitelist domain pattern
weakness

upSploit Ref: UPS-2011-0041



*Advisory Summary*

Astaro Security Gateway's default Web Filtering Exceptions allow
specially-named domains to bypass security features of the firewall.

*Vendor*

Astaro


*Affected Software*

Astaro Security Gateway

"Astaro Security Gateway hardware, software, and virtual appliances provide
full Unified Threat Management protection. All platforms include the
complete feature set and the same ease-of-use." - http://www.astaro.com/


*Description of Issue*

Astaro Security Gateway - Home edition was used, other versions may be
affected.

In the ASG WebAdmin console, choose Web Security, Web Filtering,
Exceptions. The following regular expressions form a default whitelist that
allow bypassing of the firewall's features at varying levels to achieve
compatibility (one would assume):

^https?://[A-Za-z0-9.-]*adobe.com/
^https?://[A-Za-z0-9.-]*apple.com/
^https?://[A-Za-z0-9.-]*windowsupdate.com/
^https?://[A-Za-z0-9.-]*microsoft.com/

However, a savvy attacker need only serve malware from a drive-by web site
named www.exampleadobe.com (which would match the first regular expression
above) and the features of the firewall that would be bypassed include:
Antivirus / Extension blocking / Content Removal / Authentication / URL
Filter.

The regular expressions need to be fixed to ensure the domain cannot be
prefixed with other letters.


*PoC*

Use of a domain name such as www.exampleadobe.com to serve up EICAR virus
(untested).

*Fix*

Update to the latest version


*Credits*

Timeless Prototype


*References*

http://www.astaro.com/