On Wed, 19 Dec 2001, Tony Hain wrote:
> Pekka Savola wrote:
> > All that is true, but nowhere it is said that decapsulating the packet
> > from IPv4 (or IPv6) should be interpreted as "forwarding".
> 
> The group keeps responding to you that the tunnel is an interface
> separate from the physical one it is encapsulated in, but that doesn't
> seem to stick. If you will accept that the tunnel is an independent
> interface and treat it as such, all the rules will start to make sense,
> and your continuous complaint about tunnel security will be resolved
> through the existing rules. If you can show that a node which follows
> the rules is insecure that would be helpful, but continuing to rehash
> tunneling as a security hole is not.

Please note that this is not an issue about forwarding packets with 
link-local addresses to local LAN or anything.  This is about an attack 
against the tunnel interface itself.

Undeniably, you can input packets with:

- link-local source (here: ff80::1)
- link-local destination (here: ff80::2)
- hop limit 255

in the tunnel interface.  They cannot be FORWARDED off the node though.

Now, if the router has 'ff80::2' configured as one of it's 
pseudo-interface addresses, that address can be reached via tunneling with 
hop limit 255 from anywhere.

See the potential problem here?

-- 
Pekka Savola                 "Tell me of difficulties surmounted,
Netcore Oy                   not those you stumble over and fall"
Systems. Networks. Security.  -- Robert Jordan: A Crown of Swords

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