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Hi Magnus,
FWIW, an updated version that implements the changes that were discussed in this thread is now online: https://author-tools.ietf.org/iddiff?url2=draft-ietf-lisp-pubsub-11 Cheers, Med De : BOUCADAIR Mohamed INNOV/NET
Hi Magnus,
Thanks for the follow-up. Please see inline.
Cheers, Med De : Magnus Westerlund <magnus.westerlund@xxxxxxxxxxxx>
Hi Med, Thanks, so that at least you can have a clear notification of the removal unless the packet loss rate is to high. What, is less ideal is the number of total messages
that is going to be sent here towards the source address that sent a Map-Register? [Med] I guess you meant Map-Request. Yes, there is a balance between the chattiness vs. reverse-routeablity checks and also the constraints
imposed by the base spec for retransmission Map-Notifies. Having an explicit indication is superior as it allows an xTR to reinstall the state, otherwise it will be out of sync. It would be good to have understanding of the amplification factor here that an attacker gets out it.
[Med] Such attacks assume that a Map-Request passes the authentication checks. This is typically the case of replayed Map-Requests. As
you can see in
https://datatracker.ietf.org/doc/draft-boucadair-lisp-pubsub-flow-examples/, a check based on the nonce would be sufficient to detect replayed messages: the nonce has to be greater than the local one. The message will be then silently ignored. We will be
adding more details about nonce checks to the draft. Also beyond rate limiting, is there a possibility here to reject the MAP-requests from a source address, without causing
a denial of service attack possibility? My shallow review seem to indicate that there exist such a risk. What I am considering is that there is a legit xTR (B) with IP (IP-B). If the attacker sends a MAP-Request with nonce-A, with IP source address IP-B.
[Med] If the nonce checks are in place, this request will be silently discarded. The Map-Notify will go to B. B can’t map this to a request it made as no Nonce matches what it sends and discards the
message. Thus, the map server getting a mix of legit and spoofed requests may decide to band IP-B from asking things, thus enabling a denial of service on B.
The above worries me a bit as some mitigation may have really unwanted effects here. Cheers Magnus
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