Re: Pseudorandom Flow Labels

Fernando Gont <fernando@gont.com.ar> Wed, 06 April 2011 21:20 UTC

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Sender: Fernando Gont <fernando.gont.netbook.win@gmail.com>
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Date: Wed, 06 Apr 2011 18:22:05 -0300
From: Fernando Gont <fernando@gont.com.ar>
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To: John Leslie <john@jlc.net>
Subject: Re: Pseudorandom Flow Labels
References: <BD901061-96AC-4915-B7CE-2BC1F70861A5@castlepoint.net> <201104052036.p35KaoHV019253@cichlid.raleigh.ibm.com> <4D9CAF52.9050805@gont.com.ar> <20110406204424.GG24474@verdi>
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John,

On 06/04/2011 05:44 p.m., John Leslie wrote:
> Fernando Gont <fernando@gont.com.ar>; wrote:
>> * We want Flow Labels that unpredictable by off-path attackers (history
>>   has taught us that this is a good proactive measure)
> 
>    I'm afraid I don't follow: what sort of attack could an off-path
> attacker mount by correctly guessing the Flow Label?

Play with ECMP/LAG. And, it's clear you could never implement something
like draft-blake-ipv6-flow-label-nonce-02 if FLs are predictable.

Thanks,
-- 
Fernando Gont
e-mail: fernando@gont.com.ar || fgont@acm.org
PGP Fingerprint: 7809 84F5 322E 45C7 F1C9 3945 96EE A9EF D076 FFF1