AOL Nullsoft Winamp IT Module "IN_MOD.DLL" Remote Heap Memory Corruption
  by Piotr Bania <bania.piotr@gmail.com>
  http://www.piotrbania.com


  Severity:     Important - Potencial remote code execution.

  Software affected:   Tested on AOL Nullsoft Winamp v5.33 (x86) Feb 13 2007
        (on Windows XP SP1/SP2).


  Orginal url:    http://www.piotrbania.com/all/adv/nullsoft-winamp-it_module-in_mod-adv.txt




  0.   DISCLAIMER

  Author takes no responsibility for any actions with provided informations or 
  codes. The copyright for any material created by the author is reserved. Any 
  duplication of codes or texts provided here in electronic or printed 
  publications is not permitted without the author's agreement. 
  

  I.  BACKGROUND


  AOL Nullsoft is the most popular multimedia player in the world.
  in_mod.dll is a one of Winamp plugins.


  II. DESCRIPTION


  The problem takes place when Winamp is trying to play specially
  crafted .IT file.

  IT is the proprietary module format used by Impulse Tracker, featuring 
  support for more advanced features than MOD or S3M before it. These include 
  a larger limit for lines in a pattern, higher quality samples, and other 
  effects.


  Take a look a this code snipet:

  ----// SNIP SNIP //-------------------------------------------------  
  .text:00E97BCA write_looop:                            ; CODE XREF: sub_E97976+29Dj
  .text:00E97BCA                 mov     edx, [ebp+6Ch+arg_0]
  .text:00E97BCD                 mov     ecx, [ebx+18h]
  .text:00E97BD0                 mov     dx, [eax+edx*2]
  .text:00E97BD4                 mov     [eax+ecx*2], dx
  .text:00E97BD8                 mov     eax, [ebx+370h]
  .text:00E97BDE                 mov     ecx, [ebx+18h]
  .text:00E97BE1                 mov     cx, [eax+ecx*2]
  .text:00E97BE5                 cmp     cx, [esi+6Eh]
  .text:00E97BE9                 jnb     short loc_E97C09
  .text:00E97BEB                 mov     al, [ebx+18h]
  .text:00E97BEE                 mov     ecx, [ebp+6Ch+arg_0]
  .text:00E97BF1                 mov     [ecx+esi+148h], al     ; BANG 
  .text:00E97BF8                 mov     eax, [ebx+370h]
  .text:00E97BFE                 cmp     word ptr [eax+ecx*2], 0FEh
  .text:00E97C04                 jnb     short loc_E97C09
  .text:00E97C06                 inc     dword ptr [ebx+18h]
  .text:00E97C09
  .text:00E97C09 loc_E97C09:                             ; CODE XREF: sub_E97976+273j
  .text:00E97C09                                         ; sub_E97976+28Ej
  .text:00E97C09                 movzx   ecx, word ptr [esi+68h] ; ecx=controlled value (from offset 0x20)
  .text:00E97C0D                 inc     [ebp+6Ch+arg_0]
  .text:00E97C10                 cmp     [ebp+6Ch+arg_0], ecx
  .text:00E97C13                 jb      short write_looop
  ----// SNIP SNIP //-------------------------------------------------  
  

  The memory is overwritten at 0x00E97BF1. The description of this disassembly
  listing is pretty similiar to the one written in s3m module files advisory.
  Due to my lazyness i will not repeat it again, whatsoever.


  
  III. IMPACT

  Successful exploitation may allow the attacker to run arbitrary code in 
  context of user running AOL Nullsoft Winamp.


  IV. VENDOR RESPONSE

  Due to the fact i was looking for a AOL NULLSOFT contact for over 30 minutes with
  no effect, i got finally bored and i haven't notified them at all.