ALLO ALLO WS_FTP Server

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Advisory Name: ALLO ALLO WS_FTP Server
Impact : Arbitrary code execution as SYSTEM
Discovered by: Hugh Mann hughmann_at_hotmail.com
Tested progs : Ipswitch WS_FTP Server 4.0.2.EVAL
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Description
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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
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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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