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Date:      Sat, 05 Jan 2002 03:09:10 -0000
From:      Matthew Whelan <muttley@gotadsl.co.uk>
To:        freebsd-security@FreeBSD.ORG, msch@snafu.de
Cc:        freebsd-stable@FreeBSD.ORG, Peter.Sauerland@siemens.com, iss@cert.siemens.de
Subject:   Re: TCP Sequence-Prediction (4.5-PRE)
Message-ID:  <GF97DA05OIA832C9IF3X2105PZWQOR.3c366e56@VicNBob>
In-Reply-To: <E16MExc-0003MK-00@clever.eusc.inter.net>

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03/01/2002 20:59:35, Matthias Schuendehuette <msch@snafu.de> wrote:

>Hello,
>
>my machine at work was scanned with the ISS Scanner, Vers. 6.2.1 and it 
>complained about TCP Sequence Prediction:
>
>'The TCP sequence was found to be predictable.'
>
>I was advised to install FreeBSD 4.1.1-STABLE after 2000-09-28 or later 
>:-) as listed in FreBSD-SA-00:52.
>
>I looked at the published Patch in FreBSD-SA-00:52 but couldn't find 
>the Sourcecode Sequence to be patched any more (I wasn't wondering).
>
>But so, what shall I do, who's to blame? Is the ISS lying? Is there any 
>advice from the FreeBSD Security Officer or the developers how to 
>proceed further?

If you've CVSup'd within the last 3 weeks (I suspect you must have done to 
have 4.5-PRE ;p), you should have:

 * $FreeBSD: src/sys/netinet/tcp_subr.c,v 1.73.2.23 2001/12/14 20:21:12 
jlemon Exp $

which appears now to have all the code for ISN generation (start looking at 
line 1112 - does playing with the two sysctl's mentioned make any difference 
to what ISS says? Looks like the isn_reseed_interval is only used if 
strict_rfc1948 is not set)

Matthew



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