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[waraxe-2008-SA#065] - Remote Shell Command Execution in Coppermine 1.4.14
===============================================================================
Author: Janek Vind "waraxe"
Date: 30. January 2008
Location: Estonia, Tartu
Web: http://www.waraxe.us/advisory-65.html
Target software description:
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Coppermine Photo Gallery is a multi-purpose fully-featured and integrated web
picture gallery script written in PHP using GD or ImageMagick as image library
with a MySQL backend.
Coppermine Photo Gallery has been tested working well on IIS, Apache 1.3.24
onwards to the latest Apache 2, on Linux, UNIX, OSX, and Win32 systems.
Vulnerabilities discovered
===============================================================================
1. Remote Shell Command Execution in "include/imageObjectIM.class.php"
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Preconditions:
===============
a) ImageMagick must be set as picture processing method.
Default Coppermine setting is GD, so many of the real-world Coppermine
installations are probably not affected with this security issue.
Impact
===============
An attacker is able to execute arbitrary shell commands with the privileges
of the web server process, such as user "nobody","apache" or "www".
Caused by:
===============
Unsanitized user-submitted POST variables "quality", "angle" and "clipval".
Explanation:
===============
Let's look at one of the ImageMagick wrapper functions:
--------------------------------------
function rotateImage(&$angle){
...
$imgFile = escapeshellarg("$this->directory$this->filename");
...
$cmd = "{$CONFIG['impath']}convert -quality {$this->quality}
{$CONFIG['im_options']} -rotate $angle $imgFile $imgFile";
exec ($cmd, $output, $retval);
-------------------------------------
As we can see, "$angle" variable is used in command line string without
sanitize. Now who is calling out this function?
"picEditor.php" ~ line 123:
-------------------------------------
...
$newimage = $_POST['newimage'];
...
if ($newimage){
$imgObj = new imageObject($img_dir,$newimage);
...
if ($imgObj->imgRes){
...
if ($_POST['angle']<>0){
$imgObj = $imgObj->rotateImage($_POST['angle']);
}
-------------------------------------
So if we deliver proper $_POST['newimage'] and ($_POST['angle'], then
shell command injection seems to be possible ...
And as it was not bad enough - this script is callable by anyone!
No proper permissions check! So anyone in world can exploit this security
hole and run arbitrary commands against webserver's operating system!!
There are still some mitigating factors, which will decrease danger level
of this security hole.
a) ImageMagic method is not default and most Coppermine real-word
installations are using GD. So this specific security hole has impact only,
if IM is used.
b) $_POST array goes through anti-XSS filter first and this makes exploiting
little bit harder. But this of course can't stop determined attacker.
Proof of concept? This simple html form:
[------------- PoC start --------------------------------------------------]