[Full-Disclosure] ALLO ALLO WS_FTP Server

["Hugh Mann" <hughmann@xxxxxxxxxxx>]

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Advisory Name: ALLO ALLO WS_FTP Server
Impact       : Arbitrary code execution as SYSTEM
Discovered by: Hugh Mann hughmann@xxxxxxxxxxx
Tested progs : Ipswitch WS_FTP Server 4.0.2.EVAL
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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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