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                             Luigi Auriemma

Application:  Georgia SoftWorks SSH2 Server (GSW_SSHD)
              http://www.georgiasoftworks.com/prod_ssh2/ssh2_server.htm
Versions:     <= 7.01.0003
Platforms:    Windows
Bugs:         A] format string in the log function
              B] buffer-overflow in the log function
              C] buffer-overflow in the handling of the password
Exploitation: remote
Date:         02 Jan 2008
Author:       Luigi Auriemma
              e-mail: aluigi@autistici.org
              web:    aluigi.org


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1) Introduction
2) Bugs
3) The Code
4) Fix


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===============
1) Introduction
===============


GSW_SSHD is a well known commercial SSH server which acts as SSH tunnel
for the telnet server GS_Tnet.exe.


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2) Bugs
=======

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A] format string in the log function
------------------------------------

The logging function used by the server is affected by a format string
vulnerability caused by the usage of vsprintf for building the first
message (like "LoginPassword(%s(%s)[%u])") and the usage of another
vsprintf for building the final log entry.
The bug can be exploitable through the username field.


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B] buffer-overflow in the log function
--------------------------------------

A buffer-overflow vulnerability is located in the same logging
function.
It's enough to use an username longer than 10000 chars to exploit the
vulnerability.


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C] buffer-overflow in the handling of the password
--------------------------------------------------

The server is affected also by another buffer-overflow this time
located in the instructions which handle the password supplied by the
client exploitable through a string longer than 800 chars.


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3) The Code
===========


http://aluigi.org/poc/gswsshit.zip


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4) Fix
======


No fix


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--- 
Luigi Auriemma
http://aluigi.org