Re: [tcpm] WG Last Call for ICMP Attacks
Joe Touch <touch@ISI.EDU> Wed, 09 September 2009 16:03 UTC
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Date: Wed, 09 Sep 2009 09:04:07 -0700
From: Joe Touch <touch@ISI.EDU>
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To: "Anantha Ramaiah (ananth)" <ananth@cisco.com>
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Cc: "Smith, Donald" <Donald.Smith@qwest.com>, "Carlos Pignataro (cpignata)" <cpignata@cisco.com>, tcpm Extensions WG <tcpm@ietf.org>, David Borman <david.borman@windriver.com>, Fernando Gont <fernando@gont.com.ar>
Subject: Re: [tcpm] WG Last Call for ICMP Attacks
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-----BEGIN PGP SIGNED MESSAGE----- Hash: SHA1 Hi, Anantha, Anantha Ramaiah (ananth) wrote: > Jumping in to this thread since I had mentioned it many times earlier > that delayed ICMP's causing issues for seq # check is impractical today. > On the client side validation we can have the following scenarios :- > > #1 - ICMP comes in and doesn't match the current segments (or in some > implementations packets) sitting in the retransmission queue, thus the > ICMP is silently dropped. No harm. > #2 - ICMP arrives and it matches the sequence #, this is the usual case. > No harm if false positives are handled correctly. > > > The cause for concern is the case where the ICMP packet gets delayed for > a long time and the sequence number has wrapped around and the seq # no. > exactly falls in the window of packets sitting in the retransmit queue. > This cam happen only when the data is sent at a very fast rate and such > cases extra checks are necessary. OTOH, if the ICMP packet seq# falls > outiside (> SNDNXT) in such cases this is for something not yet sent, > discard it. No harm > > IMO, this is not an issue at all, these false positives can be handled > with appropriate checks in the code. Please just put this in the doc. This issue comes up. It may not affect this solution, but it is important to include it - to say that it isn't an impact. I have asked for similar language in the long-delays doc, but I'm not sure what the impact there is. ... > My proposal would be to add some text to what Joe is concerned about, > highlight the fact that it is mostly theoritical and hence should not be > a concern. If needed some quantification can be done, but I really don't > see the point. No quantification. A version of what's above is what I'm seeking, though if we're considering everything we never see in the wild theoretical, we can gut a lot of complexity out of TCP. IMO, this isn't theoretical - it's *compliant*, and you can make the case that you do no harm when it happens. That's the point, and that's what needs to be in the doc, IMO. Joe -----BEGIN PGP SIGNATURE----- Version: GnuPG v1.4.9 (MingW32) Comment: Using GnuPG with Mozilla - http://enigmail.mozdev.org/ iEYEARECAAYFAkqn0fcACgkQE5f5cImnZruF0QCg8YKWBuLtDuwNTiTxYjRtgK0X KJQAoJV+FzgzeQ7ZwxfaoBgkkET7TIBh =pyWu -----END PGP SIGNATURE-----
- [tcpm] WG Last Call for ICMP Attacks David Borman
- Re: [tcpm] WG Last Call for ICMP Attacks Smith, Donald
- Re: [tcpm] WG Last Call for ICMP Attacks Joe Touch
- Re: [tcpm] WG Last Call for ICMP Attacks Smith, Donald
- Re: [tcpm] WG Last Call for ICMP Attacks Joe Touch
- Re: [tcpm] WG Last Call for ICMP Attacks Fernando Gont
- Re: [tcpm] WG Last Call for ICMP Attacks toby.moncaster
- Re: [tcpm] WG Last Call for ICMP Attacks Fernando Gont
- Re: [tcpm] WG Last Call for ICMP Attacks Smith, Donald
- Re: [tcpm] WG Last Call for ICMP Attacks Fernando Gont
- Re: [tcpm] WG Last Call for ICMP Attacks Smith, Donald
- Re: [tcpm] WG Last Call for ICMP Attacks Joe Touch
- Re: [tcpm] WG Last Call for ICMP Attacks Fernando Gont
- Re: [tcpm] WG Last Call for ICMP Attacks Lars Eggert
- Re: [tcpm] WG Last Call for ICMP Attacks Joe Touch
- Re: [tcpm] WG Last Call for ICMP Attacks Carlos Pignataro
- Re: [tcpm] WG Last Call for ICMP Attacks Joe Touch
- Re: [tcpm] WG Last Call for ICMP Attacks Carlos Pignataro
- Re: [tcpm] WG Last Call for ICMP Attacks Joe Touch
- Re: [tcpm] WG Last Call for ICMP Attacks Carlos Pignataro
- Re: [tcpm] WG Last Call for ICMP Attacks Joe Touch
- Re: [tcpm] WG Last Call for ICMP Attacks Anantha Ramaiah (ananth)
- Re: [tcpm] WG Last Call for ICMP Attacks Joe Touch
- Re: [tcpm] WG Last Call for ICMP Attacks Fernando Gont