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Date: Tue, 2 Mar 2004 11:18:01 -0600 (CST)
From: Mike Silbersack <silby@silby.com>
To: Darren Reed <avalon@caligula.anu.edu.au>
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cc: freebsd-security@freebsd.org
cc: Stefan Bethke <stb@lassitu.de>
Subject: Re: mbuf vulnerability
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On Wed, 3 Mar 2004, Darren Reed wrote:

> IPFilter v4 can prevent this attack with:
>
> pass in .. proto tcp ... keep state(strict)

Nope, I just tested this.  Well, I should say that it doesn't provide any
protection with "keep state"... what does (strict) mean?  The ipf in
FreeBSD doesn't seem to support it.

> > OpenBSD's pf scrubbing should be helpful here. From the FAQ:
> > > The scrub directive also reassembles fragmented packets, protecting
> > > some operating systems from some forms of attack.
> > <http://www.openbsd.org/faq/pf/scrub.html>
>
> Uh, no, "scrub" dosn't protect against this attack at all (or at least
> not according to that web page.)
>
> Darren

Also true, as this has nothing to do with ip fragments.

Mike "Silby" Silbersack