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Re: HTTP Inspect and packet reassembly
From: Yun Zheng Hu <yunzheng.hu () gmail com>
Date: Thu, 28 Oct 2010 15:56:06 +0200

I've also ran intro problems when there are small fragmented tcp
packets and using stream5 reassembly, I have posted a question about
this earlier on the list: http://seclists.org/snort/2010/q1/587

I've gotten a reply that the developers have a bug open to evaluate this.

- Yun

On Thu, Oct 28, 2010 at 15:40, L0rd Ch0de1m0rt <l0rdch0de1m0rt () gmail com> wrote:
Hello.  I am investigating a situation where TCP streams are being
fragmented quite small at the IP layer for some reason (load
balancer?) and it seems to be causing problems for some of my rules
that leverage HTTP Inspect.  From the manual I read this:

"The current version of HTTP Inspect only handles stateless
processing. This means that HTTP Inspect looks for HTTP
fields on a packet-by-packet basis, and will be fooled if packets are
not reassembled. This works fine when there is
another module handling the reassembly, but there are limitations in
analyzing the protocol. Future versions will have
a stateful processing mode which will hook into various reassembly modules."

OK, so HTTP Inspect is stateless and doesn't reassemble packets.  But
then there is the sentence, "This works fine when there is another
module handling the reassembly, but there are limitations in analyzing
the protocol."  So my question is, if I also have Stream5 enabled for
TCP, is that a sufficient "another module" or are there still
"limitations" with the HTTP protocol?

Specifically, I have problems with rules that use uricontent and
content and need to match across more than one packet.

Thanks!

-L0rd C.

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------------------------------------------------------------------------------
Nokia and AT&T present the 2010 Calling All Innovators-North America contest
Create new apps & games for the Nokia N8 for consumers in  U.S. and Canada
$10 million total in prizes - $4M cash, 500 devices, nearly $6M in marketing
Develop with Nokia Qt SDK, Web Runtime, or Java and Publish to Ovi Store 
http://p.sf.net/sfu/nokia-dev2dev
_______________________________________________
Snort-devel mailing list
Snort-devel () lists sourceforge net
https://lists.sourceforge.net/lists/listinfo/snort-devel


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