netdev - Re: [PATCH] ipv6: add anti-spoofing checks for 6to4 and 6rd

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Message-ID: <20130120033711.GA19482@order.stressinduktion.org>
Date:	Sun, 20 Jan 2013 04:37:11 +0100
From:	Hannes Frederic Sowa <hannes@...essinduktion.org>
To:	YOSHIFUJI Hideaki <yoshfuji@...ux-ipv6.org>
Cc:	netdev@...r.kernel.org, davem@...emloft.net
Subject: Re: [PATCH] ipv6: add anti-spoofing checks for 6to4 and 6rd

On Sat, Jan 19, 2013 at 10:35:49AM +0900, YOSHIFUJI Hideaki wrote:
> (2013年01月19日 05:04), Hannes Frederic Sowa wrote:
> > This patch adds anti-spoofing checks in sit.c as specified in RFC3964
> > section 5.2 for 6to4 and RFC5969 section 12 for 6rd. I left out the
> > checks which could easily be implemented with netfilter.
> > 
> > Specifically this patch adds following logic (based loosely on the
> > pseudocode in RFC3964 section 5.2):
> > 
> > if prefix (inner_src_v6) == rd6_prefix (2002::/16 is the default)
> >         and outer_src_v4 != embedded_ipv4 (inner_src_v6)
> >                 drop
> > if prefix (inner_dst_v6) == rd6_prefix (or 2002::/16 is the default)
> >         and outer_dst_v4 != embedded_ipv4 (inner_dst_v6)
> >                 drop
> > accept
> > 
> > To accomplish the specified security checks proposed by above RFCs,
> > it is still necessary to employ uRPF filters with netfilter. These new
> > checks only kick in if the employed addresses are within the 2002::/16 or
> > another range specified by the 6rd-prefix (which defaults to 2002::/16).
> 
> It seems this breaks 6rd receiving rules:
> 
> BR:
> 	if (outer src ip4 != embedded src ip4)
> 		drop();
> CE:
> 	if (outer src ip4 != embedded src ip4 ||
> 	    inner dest ip6 != configured ip6 prefix)
> 		drop();
> 
> No?

Could you give me a concrete example? I have tested this patch on BR
and CE with different 6rd prefixes (and lengths) and have not seen
any breakage. Perhaps I am missing something.

Thanks,

  Hannes

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