bugtraq - Re: New Snort Bypass - Patch

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Message-ID: <20060602231638.GE846@nfr.net>
Date: Fri, 2 Jun 2006 19:16:38 -0400
From: "M. Dodge Mumford" <dodge@....net>
To: Sigint Consulting <info@...int-consulting.com>
Cc: dailydave@...ts.immunitysec.com, bugtraq@...urityfocus.com
Subject: Re: New Snort Bypass - Patch - Bypass of Patch

Sigint Consulting said:
> However we can once again bypass this by including our CR character
> before our string like so:
> 
> perl -e 'print "GET \x0d/index.php\x90\x90 HTTP/1.0\n\r\n"'|nc
> 192.168.1.3 80
> 
> No alert is generated from the string above.

[...]

> We are not sure how much this may buy an attacker as the CR character
> may mess up any requests to the webserver, further research is needed
> on this.

I performed this research while developing NFR's web signatures, and found
that all web servers I tested (several years ago) handled end-of-lines using
"\x0d\x0a" and "\x0a" interchangeably. If you find a web server that
interprets "index.php" in the example above as an actual filename, I for one
would be very interested in knowing about it.

-- 

Dodge

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