Re: [tcpm] tcp-auth-opt issue: support for NATs
Joe Touch <touch@ISI.EDU> Thu, 07 August 2008 19:11 UTC
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Date: Thu, 07 Aug 2008 12:09:49 -0700
From: Joe Touch <touch@ISI.EDU>
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To: Eric Rescorla <ekr@networkresonance.com>
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Cc: Adam Langley <agl@imperialviolet.org>, tcpm@ietf.org
Subject: Re: [tcpm] tcp-auth-opt issue: support for NATs
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-----BEGIN PGP SIGNED MESSAGE----- Hash: SHA1 Hi, Eric, <indiv hat on> Eric Rescorla wrote: |> <indiv hat on> |> If we ignore source IP addresses, we probably end up needing to go |> through a set of possible keys when a SYN arrives. | | Well, not if you use unique key-ids. I've noted before that I don't think it's a good idea to assume cryptographic properties of fields in the header or option except for the MAC. Also, the size of the keyID space is fairly small as it is, and others have suggested it be even smaller (the few bits actually needed to rotate keys during a connection). |> This seems like it |> amplifies the impact of a SYN attack - the more keys we have, the more |> each falsly-encrypted SYN costs. | | Well, that's certainly true at some level, but if you use any | randomness at all in key-id assignment, you would expect to have | about N/256 key-ids where N is the number of keys. Unless N is | very large, the number of duplicate key-ids is likely to be high | enough that this doesn't seem like a very impressive attack, | especially since the attacker can force you to compute a MAC with | *every* packet he sends, not just SYNs. N could easily be fairly large, e.g., in peer-to-peer hubs. Note that this should be an issue only for SYNs; once a connection is made, the socket pair is already static (by TCP rules), so the appropriate key for that socket pair (thus determined during the SYN handling) can be installed - e.g., by a link. |> Alternately, a good KMS could figure out when these IP addresses |> changed, and update the TSAD accordingly. I would prefer this latter |> solution... | | Yeah, but what does that say about manual key management, which is what | we're going to have for the foreseeable future. It says that renumbering has consequences. Either you need to increase the burden on your key manager, or weaken your security (by increasing DOS impact, e.g.). If I have to pick one, I'd pick increasing the burden on the key manager in that case for *this* protocol. (where key manager could be a person). Joe -----BEGIN PGP SIGNATURE----- Version: GnuPG v1.4.9 (MingW32) Comment: Using GnuPG with Mozilla - http://enigmail.mozdev.org iEYEARECAAYFAkibSH0ACgkQE5f5cImnZrs6wgCgxP+U0CK3E7vA9HAZDRjlQ5Oj rOQAoLqK5jf4FgmtP4a1ogla28JAMLNW =jjVL -----END PGP SIGNATURE----- _______________________________________________ tcpm mailing list tcpm@ietf.org https://www.ietf.org/mailman/listinfo/tcpm
- [tcpm] tcp-auth-opt issue: support for NATs Joe Touch
- Re: [tcpm] tcp-auth-opt issue: support for NATs Adam Langley
- Re: [tcpm] tcp-auth-opt issue: support for NATs Joe Touch
- Re: [tcpm] tcp-auth-opt issue: support for NATs Adam Langley
- Re: [tcpm] tcp-auth-opt issue: support for NATs Joe Touch
- Re: [tcpm] tcp-auth-opt issue: support for NATs Adam Langley
- Re: [tcpm] tcp-auth-opt issue: support for NATs Eric Rescorla
- Re: [tcpm] tcp-auth-opt issue: support for NATs Adam Langley
- Re: [tcpm] tcp-auth-opt issue: support for NATs Eric Rescorla
- Re: [tcpm] tcp-auth-opt issue: support for NATs Adam Langley
- Re: [tcpm] tcp-auth-opt issue: support for NATs Eric Rescorla
- Re: [tcpm] tcp-auth-opt issue: support for NATs Adam Langley
- Re: [tcpm] tcp-auth-opt issue: support for NATs Joe Touch
- Re: [tcpm] tcp-auth-opt issue: support for NATs Eric Rescorla
- Re: [tcpm] tcp-auth-opt issue: support for NATs Eric Rescorla
- Re: [tcpm] tcp-auth-opt issue: support for NATs Joe Touch
- Re: [tcpm] tcp-auth-opt issue: support for NATs Eric Rescorla
- Re: [tcpm] tcp-auth-opt issue: support for NATs Joe Touch
- Re: [tcpm] tcp-auth-opt issue: support for NATs Eric Rescorla
- Re: [tcpm] tcp-auth-opt issue: support for NATs Joe Touch
- Re: [tcpm] tcp-auth-opt issue: support for NATs Adam Langley
- Re: [tcpm] tcp-auth-opt issue: support for NATs Eric Rescorla
- Re: [tcpm] tcp-auth-opt issue: support for NATs Eric Rescorla
- Re: [tcpm] tcp-auth-opt issue: support for NATs Anantha Ramaiah (ananth)
- Re: [tcpm] tcp-auth-opt issue: support for NATs Dan Wing
- Re: [tcpm] tcp-auth-opt issue: support for NATs Dan Wing
- Re: [tcpm] tcp-auth-opt issue: support for NATs Ron Bonica
- Re: [tcpm] tcp-auth-opt issue: support for NATs Eric Rescorla
- Re: [tcpm] tcp-auth-opt issue: support for NATs Dan Wing
- Re: [tcpm] tcp-auth-opt issue: support for NATs Ted Faber
- Re: [tcpm] tcp-auth-opt issue: support for NATs Dan Wing
- Re: [tcpm] tcp-auth-opt issue: support for NATs Joe Touch