Subject: [pim] DoS protection for PIM-SSM

From: James Courtier-Dutton <[email-masked]>
Date: Mon, 11 Apr 2005 10:26:08 +0100

I have been considering a number of possible attacks on PIM-SM networks.
1) Sending (S,G) data to existing broadcast G.
2) Sending (S,G) data to many G for one S.
3) Sending (S,G) data to many different S for one or more G.
4) Sending Joins to many S for one or more G (or (*,G)).
5) Sending Joins to many G for one S.

1) to 5) all present a DoS on PIM-SM.
But only 5) presents a DoS on PIM-SSM (Source specific Multicast).

I consider PIM-SM (not source specific) to be a lost cause, so I won't
discuss that here.
Has there been any work done to tackle 5) Sending Joins to many G for one S?

I have been considering a possible extension to PIM-SSM to address this.
The PIM-SSM router at the source would multicast on a special
multicast address a list of multicast groups it produces. I will call
this multicast group D.
When an IGMPv3(S,G) request is made for that particular source, the DR
will make a PIM-SM Join (S,D). Once the DR receives the Special D
group listing valid Gs for this S, it filters the IGMPv3 request based
on these, and only if it is a valid source, will it start setting up
the SPT for the (S,G) requested in the IGMPv3 message.
This will therefore move the DoS filter out from the Source to the DR,
and therefore eliminate the DoS problem. The Source will periodically
transmit the D group info, so only the edge DRs would need to store
the contents of the (S,D) data.

Any comments?

James

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From: Pekka Savola <[email-masked]>
Date: Mon, 11 Apr 2005 17:11:11 +0300 (EEST)

> But only 5) presents a DoS on PIM-SSM (Source specific Multicast).

You might be interested in checking out:

draft-ietf-mboned-mroutesec-04.txt (in RFC-editor's queue) and
draft-savola-pim-lasthop-threats-01.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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From: Mark Handley <[email-masked]>
Date: Mon, 11 Apr 2005 11:00:21 +0100

>I consider PIM-SM (not source specific) to be a lost cause, so I won't

Agreed.

>Has there been any work done to tackle 5) Sending Joins to many G for one S?

Although it's not the main focus, there were a few ideas in here:
  http://www.cs.ucl.ac.uk/staff/M.Handley/papers/dos-arch.pdf

Cheers,
	Mark