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Re: MD5 for TCP/BGP Sessions

  • From: Pekka Savola
  • Date: Wed Mar 30 16:40:50 2005

On Wed, 30 Mar 2005, John Kristoff wrote:
[on bgp/md5 and acl's]
ACLs are often used, but vary widely depending on organization.
It can be difficult to manage ACLs on a box with a large number
of peers that uses many local BGP peering addresses.  I'm sure
some organizations reviewed and updated their ACLs as a result
of the last scare, but that is a local, private decision and it
would probably be hard to get good sample of who and what changed.
I would be double careful here, just to make sure everybody understands what you're protecting.

iBGP sessions? ACLs are trivial if you have your borders secured.

eBGP sessions? GTSM is your friend (if supported). Practically, if you know your peer and you also protect your borders, ACLs are rather trivial as well.

What you seem to be saying is using ACLs to enumerate the valid endpoints for eBGP sessions. That goes further than the above but indeed is also a pain to set up and maintain.

There are other attacks you can make against TCP sessions (protected by MD5 or not) using ICMP, though. (see draft-gont-tcpm-icmp-attacks-03.txt).

Pekka Savola "You each name yourselves king, yet the
Netcore Oy kingdom bleeds."
Systems. Networks. Security. -- George R.R. Martin: A Clash of Kings

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