Re: bidding down attach on NAT-T
Francis Dupont <Francis.Dupont@enst-bretagne.fr> Wed, 05 March 2003 18:33 UTC
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From: Francis Dupont <Francis.Dupont@enst-bretagne.fr>
To: Michael Richardson <mcr@sandelman.ottawa.on.ca>
cc: ipsec@lists.tislabs.com, Charlie_Kaufman@notesdev.ibm.com
Subject: Re: bidding down attach on NAT-T
In-reply-to: Your message of Tue, 04 Mar 2003 14:37:05 EST. <200303041937.h24Jb5gm001383@marajade.sandelman.ottawa.on.ca>
Date: Wed, 05 Mar 2003 16:54:18 +0100
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In your previous mail you wrote: -----BEGIN PGP SIGNED MESSAGE----- >>>>> "Francis" == Francis Dupont <Francis.Dupont@enst-bretagne.fr> writes: Francis> => the IKEv2 mechanism has to be revised because it is subject Francis> to a bidding down attack. Can we open a thread about this? As I understood things, this issue is not that a third party can force UDP encapsulation of the ESP packets by playing with the UDP headers of the IKE exchange. => there are two things, the bidding down attack and the attack using the NAT traversal. Your text is about the second: it is useful but it is not the bidding down attack, i.e., it is just an explaination of the "bidding down". The issue is that said attacker can force all transmissions from the gateway to the client to go via itself. => not itself but someone. It does this by pretending to be a NAT, and futzing with the source IP/port#. The gateway will use that address for the packets it sends. We can not, in general have the gateway refuse to change its notion of where to send things because: 1) the attacker could have started futzing at the beginning of the exchange anyway. 2) a NAT may legitimately assign new port numbers/IP addresses to the flow. So, what in the end is the effect of having the IKE/ESP flow sent via some malicious third party? Assuming that the third party does not drop any packets in the flow, we have: a) additional latency. b) traffic analysis. I assume that the crypto is good. If it isn't, and the attacker can break the crypto, all bets are off anyway. The most serious thing that the third party can do is to hijack the flow with the intent to disrupt the flow. This is a denial of service attack. I have a notion on how to deal with this, but before I get into it, I'd like be sure that we are solving the right problem. => yes, the main issue is the DoS attack. IKE itself is secure but it can be (ab)used to launch attacks. The problem is: is there a way for the client/gateway to agree that they have a functional UDP pipe between each other before committing to a change. => there is none. It seems we agree that the NAT traversal feature is less secure so: - it should be disabled when one knows there cannot be a NAT on the path. - the NAT detection should be safe, i.e., it should not give false positive. This is my "bidding down" argument against the current mechanism (which has many other problems but one is enough). Thanks Francis.Dupont@enst-bretagne.fr PS: the bidding down attack itself is obvious: the attacker has only to change a NAT-DETECTION-*-IP in the IKE_SA_INIT reply. PPS: the reference about attacks using IKE (not against IKE) is draft-dupont-transient-pseudonat-01.txt
- suites vs. a la carte and IPcomp in IKEv2-05 Dan Harkins
- Re: suites vs. a la carte and IPcomp in IKEv2-05 Derek Atkins
- RE: suites vs. a la carte and IPcomp in IKEv2-05 Stephane Beaulieu
- Re: suites vs. a la carte and IPcomp in IKEv2-05 Scott G. Kelly
- Re: suites vs. a la carte and IPcomp in IKEv2-05 Paul Koning
- Re: suites vs. a la carte and IPcomp in IKEv2-05 Lakshminath Dondeti
- Re: suites vs. a la carte and IPcomp in IKEv2-05 Bill Sommerfeld
- Re: suites vs. a la carte and IPcomp in IKEv2-05 Derrell Piper
- Re: suites vs. a la carte and IPcomp in IKEv2-05 Abraham Shacham
- Re: suites vs. a la carte and IPcomp in IKEv2-05 Andrew Krywaniuk
- Re: suites vs. a la carte and IPcomp in IKEv2-05 Dan Harkins
- Re: suites vs. a la carte and IPcomp in IKEv2-05 Henry Spencer
- Re: suites vs. a la carte and IPcomp in IKEv2-05 Paul Koning
- RE: suites vs. a la carte and IPcomp in IKEv2-05 Jayant Shukla
- RE: suites vs. a la carte and IPcomp in IKEv2-05 Jayant Shukla
- UI suites (was: suites vs. a la carte and IPcomp … Paul Hoffman / VPNC
- Re: suites vs. a la carte and IPcomp in IKEv2-05 Abraham Shacham
- Re: suites vs. a la carte and IPcomp in IKEv2-05 Derek Atkins
- RE: suites vs. a la carte and IPcomp in IKEv2-05 Andrew Krywaniuk
- RE: suites vs. a la carte and IPcomp in IKEv2-05 Henry Spencer
- RE: suites vs. a la carte and IPcomp in IKEv2-05 Paul Hoffman / VPNC
- RE: suites vs. a la carte and IPcomp in IKEv2-05 Paul Koning
- Re: suites vs. a la carte and IPcomp in IKEv2-05 Charlie_Kaufman
- Re: suites vs. a la carte and IPcomp in IKEv2-05 Francis Dupont
- Re: suites vs. a la carte and IPcomp in IKEv2-05 Henry Spencer
- Re: suites vs. a la carte and IPcomp in IKEv2-05 Abraham Shacham
- bidding down attach on NAT-T Michael Richardson
- Re: bidding down attach on NAT-T Francis Dupont
- Re: suites vs. a la carte and IPcomp in IKEv2-05 Charlie_Kaufman
- Re: bidding down attach on NAT-T Charlie_Kaufman
- Re: bidding down attach on NAT-T Michael Richardson
- Re: suites vs. a la carte and IPcomp in IKEv2-05 Henry Spencer
- Re: Re: bidding down attach on NAT-T Jayant Shukla
- Re: suites vs. a la carte and IPcomp in IKEv2-05 Abraham Shacham
- Re: bidding down attach on NAT-T Michael Richardson
- Re: bidding down attach on NAT-T Francis Dupont
- Re: bidding down attach on NAT-T Francis Dupont
- Re: suites vs. a la carte and IPcomp in IKEv2-05 Dan Harkins
- Re: bidding down attach on NAT-T Andrew Krywaniuk
- Re: bidding down attach on NAT-T Francis Dupont
- Re: bidding down attach on NAT-T Derek Atkins
- Re: bidding down attach on NAT-T Francis Dupont
- Re: bidding down attach on NAT-T Charlie_Kaufman
- Re: bidding down attach on NAT-T Ari Huttunen
- Re: bidding down attach on NAT-T Francis Dupont
- Re: bidding down attach on NAT-T Derek Atkins
- Re: suites vs. a la carte and IPcomp in IKEv2-05 Derek Atkins
- Re: suites vs. a la carte and IPcomp in IKEv2-05 Paul Koning
- Re: suites vs. a la carte and IPcomp in IKEv2-05 Eric Rescorla
- Re: suites vs. a la carte and IPcomp in IKEv2-05 Eric Rescorla
- Re: suites vs. a la carte and IPcomp in IKEv2-05 Paul Koning
- Re: suites vs. a la carte and IPcomp in IKEv2-05 Paul Hoffman / VPNC
- Re: suites vs. a la carte and IPcomp in IKEv2-05 Scott G. Kelly
- Re: suites vs. a la carte and IPcomp in IKEv2-05 Derek Atkins
- Re: bidding down attach on NAT-T Francis Dupont
- Re: suites vs. a la carte and IPcomp in IKEv2-05 Paul Koning
- Re: suites vs. a la carte and IPcomp in IKEv2-05 Eric Rescorla
- Re: bidding down attach on NAT-T Derek Atkins
- Re: bidding down attach on NAT-T Francis Dupont
- Re: suites vs. a la carte and IPcomp in IKEv2-05 Tylor Allison
- Re: bidding down attach on NAT-T jpickering@creeksidenet.com
- Re: suites vs. a la carte and IPcomp in IKEv2-05 Tero Kivinen
- Re: bidding down attach on NAT-T Derek Atkins
- Re: bidding down attach on NAT-T Steve Dispensa
- Re: bidding down attach on NAT-T Francis Dupont