Penetration Testing mailing list archives
Controling Segment Contents in TCP Stream
From: "Crist J. Clark" <crist.clark () attbi com>
Date: Wed, 11 Jun 2003 10:52:04 -0700
I am looking for a simple tool that I can use to control how TCP data is split up among segments. I can't seem to figure out how to coax Netcat into doing this. What I am trying to do is mess with some firewall/proxy software by screwing with (unfounded) assumptions it makes about the contents of individual packets. For example, I am seeing some Widely Used Commercial Firewall Software choke when an FTP client sends a packet containing just, "USER " That is, U, S, E, R, and a space. The next segment carries the rest of the line, "anonymous\r\n" Now, since TCP is a stream-oriented protocol, this is actually perfectly acceptable behavior. The TCP stack of the server will handle this just fine, and the FTP server software will see the perfectly Standard-compliant input, "USER anonymous\r\n" At the other end. This is an old and well known problem with firewall/proxies, yet we see it all of the time. The problem I am having is finding a tool that lets me easily control the data in each segement of the TCP stream. I've manually crafted some packets with hping2 to do some testing, but it is a huge PITA to build the whole SYN/SYN-ACK/ACK handshake each time. Can anyone recommend a tool or show me how to get Netcat to do this? Or am I going to have to build something myself or hack Netcat code? Since this is a well known issue, I was hoping someone already had done the work and made it available. Thanks. -- Crist J. Clark | cjclark () alum mit edu | cjclark () jhu edu http://people.freebsd.org/~cjc/ | cjc () freebsd org --------------------------------------------------------------------------- ----------------------------------------------------------------------------
Current thread:
- Controling Segment Contents in TCP Stream Crist J. Clark (Jun 11)
- <Possible follow-ups>
- RE: Controling Segment Contents in TCP Stream Marc Sherman (Jun 11)
- Re: Controling Segment Contents in TCP Stream Bernd Jendrissek (Jun 13)
- Re: Controling Segment Contents in TCP Stream Crist J. Clark (Jun 13)