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TUCoPS :: Windows Net Apps :: bt1178.txt

SpeakFreely for Win <= 7.6a remote crash through malformed GIF






This should probably be added to the CD.

----- Original Message ----- 
From: "Luigi Auriemma" <aluigi@altervista.org>
To: <bugtraq@securityfocus.com>
Cc: <vulnwatch@vulnwatch.org>; <list@dshield.org>; <list@securiteam.com>
Sent: Monday, September 22, 2003 11:03 AM
Subject: SpeakFreely for Win <= 7.6a remote crash through malformed GIF


> #######################################################################
> 
>                              Luigi Auriemma
> 
> Application: SpeakFreely
>              http://www.fourmilab.ch/speakfree/
>              http://speak-freely.sourceforge.net
> Versions:    <= 7.6a
> Platforms:   Windows (Unix versions are NOT vulnerable)
> Bug:         Remote crash caused by malformed GIF image
> Risk:        Low/Medium
> Author:      Luigi Auriemma
>              e-mail: aluigi@altervista.org
>              web:    http://aluigi.altervista.org
> 
> 
> #######################################################################
> 
> 
> 1) Introduction
> 2) Bug
> 3) The Code
> 4) Fix
> 
> 
> #######################################################################
> 
> ===============
> 1) Introduction
> ===============
> 
> 
> SpeakFreely is a very interesting real-time voice application with
> cryptographic support developed by John Walker and now the project will
> be continued on Sourceforge by a group of programmers and fans.
> The program is multiplatform, opensource and is also used as add-on of
> ICQ.
> 
> 
> 
> #######################################################################
> 
> ======
> 2) Bug
> ======
> 
> 
> SpeakFreely for Windows has a nice feature called "Show your face" that
> lets users to send an image (bmp and gif) to the others and it is
> enabled by default.
> 
> Unfortunally in the program there is a "forgotten check", so if the
> function GlobalAlloc() fails there are no instruction to check its
> return value.
> 
> The problem happens with GIF files that have a content (only the values
> "Image width" and "Image height" in the header, not the real content)
> too big or equal to zero and so they are unallocable in memory.
> The crash will happen when the program will try to use the pointer
> returned by the unchecked function.
> 
> The following are 2 examples:
> 
> 
> A] 0000.gif
> 
> 0000000: 4749 4638 3961 0000 0000 0000 002c 0000  GIF89a.......,..
> 0000010: 0000 0000 0000 00                        .......
>               |    |
> Crash:
> :00416227 8A0439                  mov al, byte ptr [ecx+edi]
> (ecx+edi is an unreacheable location)
> 
> 
> 
> 
> B] ffff.gif
> 
> 0000000: 4749 4638 3961 0000 0000 0000 002c 0000  GIF89a.......,..
> 0000010: 0000 ffff ffff 00                        .......
>               |    |
> Crash:
> 00415CF8 668910                  mov word ptr [eax], dx
> (eax is 0)
> 
> 
> 
> 
> #######################################################################
> 
> 
> ===========
> 3) The Code
> ===========
> 
> 
> Step by step:
> 
> A] You must create a custom GIF file manually (with a hex editor) or
>    you can also use my small tool ("gifbug file.gif" or "gifbug -iw 0
>    -ih 0 file.gif"):
> 
>    http://aluigi.altervista.org/testz/gifbug.zip
> 
> B] Then you must select the malformed GIF from your SpeakFreely client
>    (Options -> Show your face -> Browse)
> 
> C] You must connect to the victim (Connection -> New)
> 
> D] And then you need to talk or just to press the left mouse button on
>    the dialog box appeared
> 
> E] The victim should be crashed
> 
> 
> 
> (NOTE: you can also wait an incoming connection and passively crashing
> the client)
> 
> 
> 
> #######################################################################
> 
> ======
> 4) Fix
> ======
> 
> 
> Disable the option "Show faces of other users" from the menu
> Options -> Show your face
> 
> 
> 
> #######################################################################
> 
> 
> 
> --- 
> Luigi Auriemma
> http://aluigi.altervista.org


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