Re: Fwd: PROBLEM: IPv6 Duplicate Address Detection with non RFC-conform ICMPv6 packets

[Eric Dumazet <eric.dumazet@gmail.com>]

Le samedi 07 mai 2011 à 14:55 +0200, Jan Ceuleers a écrit :
> The networking folks are on netdev
> 
> -------- Original Message --------
> Subject: PROBLEM: IPv6 Duplicate Address Detection with non RFC-conform 
> ICMPv6 packets
> Date: Thu, 05 May 2011 11:52:05 +0200
> From: Gervais Arthur <arthur.gervais@insa-lyon.fr>
> To: <linux-kernel@vger.kernel.org>
> CC: <arthur.gervais@insa-lyon.fr>
> 
> [1.] One line summary of the problem:
> 
> A specially crafted Ethernet ICMPv6 packet which is not conform to the
> RFC can perform a IPv6 Duplicate Address Detection Failure.
> 
> [2.] Full description of the problem/report:
> 
> If a new IPv6 node joins the local area network, the new node sends an
> ICMPv6 Neighbor Solicitation packet in order to check if the
> self-generated local-link IPv6 address already occupied is.
> 
> An attacker can answer to this Neighbor Solicitation packet with an
> ICMPv6 Neighbor Advertisement packet, so that the new IPv6 node is not
> able to associate the just generated IPv6 address.
> -- This problem is well known and IPv6 related.
> 
> The new problem is that the attacker can modify the Ethernet Neighbor
> Advertisement packets, so that they are not RFC conform and so that it
> is even more difficult to detect the attacker.
> 
> If an attacker sends the following packet, duplicate address detection
> fails on Linux:
> 
> Ethernet Layer: 	Victim MAC --> Victim MAC
> IPv6 Layer:		fe80::200:edff:feXX:XXXX --> ff02::1
> 			ICMPv6
> 			  Type 136 (Neighbor Advertisement)
> 			  Target: fe80::200:edff:feXX:XXXX
> 			ICMPv6 Option
> 			  Type 2 (Target link-layer address) Victim MAC
> 
> Please find attached a drawing and a proof of concept.
> 
> [3.] Keywords (i.e., modules, networking, kernel):
> 
> Network, IPv6, Duplicate Address Detection
> 
> [4.] Kernel version (from /proc/version):
> 
> Latest tested:
> Linux version 2.6.35-22-generic (buildd@rothera) (gcc version 4.4.5
> (Ubuntu/Linaro 4.4.4-14ubuntu4) ) #33-Ubuntu SMP Sun Sep 19 20:34:50 UTC
> 2010
> (and before most probably)
> 
> [6.] A small shell script or example program which triggers the
>        problem (if possible)
> 
> Please find attached a python script demonstrating the problem.
> 
> [X.] Other notes, patches, fixes, workarounds:
> 
> The Linux Kernel should not accept incoming Ethernet packets originating
> from an internal Ethernet card (identified by the MAC address)
> 

I fail to understand the problem.

The attacker might use any kind of source MAC address to fool 'Victim'
or 'network admins'

Why one particular address should be avoided ?