Multiple Vendor ImageMagick .psd Image File Decode Heap Overflow
Vulnerability

iDEFENSE Security Advisory 01.17.05
www.idefense.com/application/poi/display?id=184&type=vulnerabilities
January 17, 2005

I. BACKGROUND

ImageMagick provides a variety of graphics image-handling libraries and 
capabilities. These libraries are widely used and are shipped by default

on most Unix and Linux distributions. These libraries are commonly 
installed by default on computers where any other graphical image viewer
or X Desktop environment is installed (such as Gnome or KDE).

More information is available at the following site:

   http://www.imagemagick.org

II. DESCRIPTION

Remote exploitation of a buffer overflow vulnerability in The 
ImageMagick's Project's ImageMagick PSD image-decoding module could 
allow an attacker to execute arbitrary code. 

A heap overflow exists within ImageMagick, specifically in the decoding 
of Photoshop Document (PSD) files. The vulnerable code follows:

ImageMagick-6.1.0/coders/psd.c

for (j=0; j < (long) layer_info[i].channels; j++) 
{ 
  layer_info[i].channel_info[j].type=(short)ReadBlobMSBShort(image);
  layer_info[i].channel_info[j].size=ReadBlobMSBLong(image);
  [...]
} 

The array channel_info is only 24 elements large, and the loop variable,

"j", is bounded by a user-supplied value from the image file, thus 
allowing a heap overflow to occur when more than 24 layers are 
specified. If heap structures are overflowed in a controlled way, 
execution of arbitrary code is possible.

III. ANALYSIS

Exploitation may allow attackers to run arbitrary code on a victim's 
computer if the victim opens a specially formatted image. Such images 
could be delivered by e-mail or HTML, in some cases, and would likely 
not raise suspicion on the victim's part. Exploitation is also possible 
when a web-based application uses ImageMagick to process user-uploaded 
image files.

IV. DETECTION

iDEFENSE has confirmed this vulnerability in ImageMagick 6.1.0 and 
ImageMagick 6.1.7. Earlier versions are also suspected vulnerable.

The following vendors may include vulnerable ImageMagick packages: 
  
   The Debian Project 
   MandrakeSoft 
   Red Hat, Inc. 

V. WORKAROUND

Do not open files from untrusted sources. Do not allow untrusted sources

to process images using your web application.

VI. VENDOR RESPONSE

This vulnerability is addressed in ImageMagick 6.1.8-8, available for
download at:

   http://www.imagemagick.org/www/download.html

VII. CVE INFORMATION

The Common Vulnerabilities and Exposures (CVE) project has assigned the
names CAN-2005-0005 to these issues. This is a candidate for inclusion
in the CVE list (http://cve.mitre.org), which standardizes names for
security problems.

A Mitre Corp. Common Vulnerabilities and Exposures (CVE) number has not
been assigned yet.

VIII. DISCLOSURE TIMELINE

12/21/2004  Initial vendor notification
01/14/2004  Initial vendor response
01/17/2005  Public disclosure

IX. CREDIT

Andrei Nigmatulin is credited with this discovery.

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X. LEGAL NOTICES

Copyright (c) 2004 iDEFENSE, Inc.

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Disclaimer: The information in the advisory is believed to be accurate
at the time of publishing based on currently available information. Use
of the information constitutes acceptance for use in an AS IS condition.
There are no warranties with regard to this information. Neither the
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or consequential loss or damage arising from use of, or reliance on,
this information.