TCP RST attack (the cause of all that MD5-o-rama)

Dan Hollis goemon at anime.net
Tue Apr 20 21:11:02 UTC 2004


On Tue, 20 Apr 2004, Crist Clark wrote:
> But it has limited effectiveness for multi-hop sessions. There is the
> appeal of a solution that does not depend of the physical layout of the
> BGP peers.

Does MD5 open the door to cpu DOS attacks on routers though? Eg can 
someone craft a DOS attack to take out the CPU on a router by forcing it 
to MD5 authenticate torrents of junk packets, using less bandwidth than 
it would take to DOS the links themselves?

As has been pointed out, blind attacker needs to guess the source port as 
well, which would seem to multiply the search space blind attackers need 
to hit (the tcpsecure paper states as much - "assuming the attacker can
accurately guess both ports")

Are such attacks still practical in that light?

-Dan




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