netdev - Re: Fwd: RFC 6980 on Security Implications of IPv6 Fragmentation with IPv6 Neighbor Discovery

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Message-ID: <520C7519.1010000@gont.com.ar>
Date:	Thu, 15 Aug 2013 03:28:41 -0300
From:	Fernando Gont <fernando@...t.com.ar>
To:	hannes@...essinduktion.org
CC:	netdev <netdev@...r.kernel.org>
Subject: Re: Fwd: RFC 6980 on Security Implications of IPv6 Fragmentation
 with IPv6 Neighbor Discovery

Hi, Hannes,

Thanks so much for your timely response! -- Please find my comments
in-line...

On 08/14/2013 08:06 PM, Hannes Frederic Sowa wrote:
> On Wed, Aug 14, 2013 at 05:19:13AM -0300, Fernando Gont wrote:
>> Folks,
>>
>> FYI. -- this is an important piece when it comes to First Hop (i.e.,
>> "local link") Security.
> 
> Thanks for the heads-up, Fernando!
> 
> I sketched up a patch to protect the receiving side. I still don't know if I
> should make this behaviour default or configurable via a sysctl knob. I really
> don't want to break existing installations.

Make it the default behavior. If anything, provide a sysctl knob to
override it.

Note: In the specific case of NS/NA messages, it's impossible nowadays
to find them fragmented in a real network (we don't even have options
(other than padding) to make NS/NAs grow so large!).



> As an extra plus, we now discard packets with nested fragment headers at once.
> Those packets should never have been accepted.

Is that the "goto fail_hdr" part in your patch?

P.S.: What about RS/RA messages?

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



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