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List:       bugtraq
Subject:    ALLO ALLO WS_FTP Server
From:       "Hugh Mann" <hughmann () hotmail ! com>
Date:       2004-03-23 7:13:29
Message-ID: BAY1-F48yZR4XAQU7mA00006eeb () hotmail ! com
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~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Advisory Name: ALLO ALLO WS_FTP Server
Impact       : Arbitrary code execution as SYSTEM
Discovered by: Hugh Mann hughmann@hotmail.com
Tested progs : Ipswitch WS_FTP Server 4.0.2.EVAL
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

Description
~~~~~~~~~~~
A user who can upload files, and also has a max number of files limit or max 
total file size limit, can read any memory address the WS_FTP Server can 
read. With the right address, the user can cause a buffer overflow and 
execute arbitrary code as SYSTEM.

Details
~~~~~~~
There's a vulnerability in the ALLO handler when it sends an error string to 
the client. Instead of pushing an ASCIIZ string, it pushes a 64-bit value 
equal to total size of all files in user's dir and any sub-dirs. This is a 
value we can easily control if we exploit the WS_FTP Server REST 
vulnerability. If we change this value to a string of size equal to ~256 
bytes, we can overwrite the return address and execute arbitrary code as 
SYSTEM.

Exploit
~~~~~~~
See the attached source code.

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["xp_ws_ftp_server2.zip" (application/x-zip-compressed)]

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