Advisory 02/2004: Trillian remote overflows

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Date: Tue, 24 Feb 2004 19:52:23 +0100
To: full-disclosure@lists.netsys.com, bugtraq@securityfocus.com

                           e-matters GmbH
                          www.e-matters.de

                      -= Security Advisory =-

     Advisory: Trillian remote overflows
 Release Date: 2004/02/24
Last Modified: 2004/02/24
       Author: Stefan Esser [s.esser@e-matters.de]

  Application: Trillian 0.71-0.74 w/ patch f
               Trillian Pro 1.0, 2.0, 2.01
     Severity: 2 vulnerabilities were found in the instant
               messenger Trillian that allow remote compromise
         Risk: Critical
Vendor Status: Vendor has fixed and released patches
    Reference: http://security.e-matters.de/advisories/022004.html

Overview:

   Quote from http://www.trillian.cc
   
   "What is Trillian?
   
    Trillian is a skinnable, interoperable instant messaging client.
    Grab the best IM client available on the Internet today!
    Trillian .74 is completely free, with no spyware and no ads.
    Over 10 million downloads can't be wrong!"
    
   While playing around with the recently found Gaim vulnerabilities
   it was discovered that two of them also affect Trillian and allow
   remote compromise.
   
      
Details:
   
   While testing the developed exploits against other instant
   messaging clients it was discovered that Trillian as one of the
   most popular 3rd party instant client for the windows operating
   system is indeed vulnerable to the bugs discovered in the GAIM
   sourcecode
   
   The bugs in question are
   
   [01 - AIM/Oscar DirectIM Integer Overflow]
   
   When Trillian receives a DirectIM packet with a size above 8kb
   it spawns a thread to receive the complete packet. This thread
   allocates a buffer for the incoming packet and one extra byte.
   This procedure suffers from an integer overflow when the size
   is UINT_MAX and will only allocate a buffer of minimum size
   in that case. This buffer is then filled with multiple calls to
   recv() which will result in an arbitrary size heap overflow.

   [02 - Yahoo Packet Parser Overflow]
   
   A Yahoo Messenger packet consist of a header and a list of keys
   with their associated values. When reading an oversized keyname
   a standard stackoverflow can be triggered.
   
   The code below is part of Trillian since version 0.71 which was
   released on the 18th december 2001. It was manually decompiled.
   The variable names were taken from the GAIM source code. If you
   compare the decompiled code with the code in yahoo.c (revision
   1.12 from 15th nov 2001) you will realise that it is more or
   less identical. It is up to the reader to find an explanation
   how this GPL licensed codesnippet ended up in Trillian.
   
   
      int pos = 0;

      while (pos + 1 < len) {

         char key[64], *value = NULL;
         int x = 0, accept;

         struct yahoo *YAHOO = malloc(12);

         while (pos + 1 < len) {
            if (data[pos] == 0xc0 && data[pos + 1] == 0x80)
               break;
            key[x++] = data[pos++];
         }
         key[x] = 0;
         pos += 2;
         YAHOO->key = atoi(key);
         accept = x;
        
         if (accept) {
            value = malloc(len - pos + 1);
         }

         while (pos + 1 < len) {
            if (data[pos] == 0xc0 && data[pos + 1] == 0x80)
               break;
            if (accept) {
               value[x++] = data[pos++];
            }
         }

         if (accept) {
            value[x] = 0;
         }
         pos += 2;
         if (accept) {
            YAHOO->value = strdup(value);
            free(value);
         }

         return YAHOO;

      }
   
   Finally it has to be mentioned, that it is no longer possible
   to exploit the second vulnerability through the Yahoo! servers.
   It is not known what and why Yahoo! has changed, but they
   do not longer transport unknown keys. We were only able to
   exploit the vulnerability with man in the middle attacks.
   This can be considered good news because this will make it
   impossible to write a widespread worm.
   
   Although Trillian Pro is compiled with the Visual Studio
   stackoverflow protection it is possible to exploit this
   vulnerability by simply overflowing up to the stack top and
   abusing the power of structured exception handlers.
   

Proof of Concept:

   e-matters is not going to release an exploit for any of these
   vulnerabilities to the public.
  

Disclosure Timeline:

   18. February 2004 - Cerulean Studios were contacted over their
                       forum and a mail was sent to the domain
                       owner because mails to security@trillian.org
                       simply bounce back and there is no other way
                       to contact them
   19. February 2004 - Cerulean Studios acknowledged the mail
   20. February 2004 - Cerulean Studios gave us the patches to test
                       Patches were verified and we were notified
                       that they plan to release them on Monday
   23. February 2004 - Nothing happened...
   24. February 2004 - Cerulean Studios have released the patched
                       versions

Recommendation:

   As usual it is recommend to download the update from the Trillian
   homepage at
   
   http://www.trillian.cc
   
   We are not aware of any public exploit for these vulnerabilities,
   but anyone who has developed an exploit for the GAIM vulnerabilities
   could change it easily to work against Trillian, too.
   
   
GPG-Key:

   http://security.e-matters.de/gpg_key.asc
    
   pub 1024D/75E7AAD6 2002-02-26 e-matters GmbH - Securityteam
   Key fingerprint = 43DD 843C FAB9 832A E5AB CAEB 81F2 8110 75E7 AAD6

Copyright 2004 Stefan Esser. All rights reserved.

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