Re: [tcpm] question about TCP-AO and rekeying
Eric Rescorla <ekr@networkresonance.com> Wed, 17 June 2009 23:24 UTC
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Date: Wed, 17 Jun 2009 16:28:13 -0700
From: Eric Rescorla <ekr@networkresonance.com>
To: Joe Touch <touch@ISI.EDU>
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Subject: Re: [tcpm] question about TCP-AO and rekeying
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At Wed, 17 Jun 2009 09:20:07 -0700, Joe Touch wrote: > > -----BEGIN PGP SIGNED MESSAGE----- > Hash: SHA1 > > > > Eric Rescorla wrote: > > At Wed, 17 Jun 2009 08:41:52 -0700, > > Joe Touch wrote: > >> -----BEGIN PGP SIGNED MESSAGE----- > >> Hash: SHA1 > >> > >> > >> > >> Eric Rescorla wrote: > >>> At Tue, 16 Jun 2009 23:24:55 -0700, > >>> Joe Touch wrote: > >>>> Eric Rescorla wrote: > >>>> ... > >>>>>> However, the invariant is twofold: > >>>>>> > >>>>>> a) for a given packet, only one MKT applies > >>>>>> > >>>>>> b) for two endpoints with multiple MKTs, > >>>>>> the *same* MKT applies. > >>>>> I don't see that this is true. As I understand the current design > >>>>> there's no reason that both sides can't use different MKTs > >>>>> indefinitely. > >>>> Each side can use a different MKT to transmit. However, if side A uses > >>>> MKT X to transmit, then side B needs to know to use MKT X to receive. If > >>>> side A matches MKT X on transmit and side B matches MKT Y on receive, > >>>> then there's a problem for that connection. > >>>> > >>>> So let's rephrase, recognizing that there are two MKTs at any given time > >>>> (one for transmit on each side, and the same pair for receive on the > >>>> opposite side). > >>>> > >>>> b) for two endpoints, if a given packet matches MKT on one side during > >>>> transmit, it must match the corresponding MKT on the other side during > >>>> receive. > >>> Right, but this doesn't require ordering or non-overlapping, as far as > >>> I can tell. It merely requires that at any time there only be one MKT > >>> corresponding to any given socketpair/key-id. > >> That is only possible with either non-overlapping or ordering to resolve > >> overlaps. > > > > I don't see why this is true. Any time a new key is entered, you > > find all other keys that overlap with it and verify that they > > have distinct key-ids. > > That is a very expensive operation that I am hoping we can avoid. It's not a very expensive operation unless you have a truly fantastic number of keys, which can only happen if you have an automatic key management protocol which can be designed not to create this situation. > > If so, the entry fails. If that's what > > you mean by "prohibit overlaps", yes, I think we should > > prohibit overlaps. > > > > If what you mean is that two MKTs with different key-ids can't overlap > > the same socket pair space, I don't see a problem with that. > > That is a problem for outgoing SYNs. For those, either the connection > has to know a-priori which ID to use, or we need to make sure MKTs can't > overlap at all (ignoring keyIDs). I'm sorry, but I don't see why. -Ekr
- [tcpm] question about TCP-AO and rekeying Joe Touch
- Re: [tcpm] question about TCP-AO and rekeying Joe Touch
- Re: [tcpm] question about TCP-AO and rekeying Eric Rescorla
- Re: [tcpm] question about TCP-AO and rekeying Eric Rescorla
- Re: [tcpm] question about TCP-AO and rekeying Joe Touch
- Re: [tcpm] question about TCP-AO and rekeying Eric Rescorla
- Re: [tcpm] question about TCP-AO and rekeying Joe Touch
- Re: [tcpm] question about TCP-AO and rekeying Eric Rescorla
- Re: [tcpm] question about TCP-AO and rekeying Joe Touch
- Re: [tcpm] question about TCP-AO and rekeying Eric Rescorla
- Re: [tcpm] question about TCP-AO and rekeying Joe Touch
- Re: [tcpm] question about TCP-AO and rekeying Eric Rescorla
- Re: [tcpm] question about TCP-AO and rekeying Joe Touch
- Re: [tcpm] question about TCP-AO and rekeying Eric Rescorla
- Re: [tcpm] question about TCP-AO and rekeying Joe Touch
- Re: [tcpm] question about TCP-AO and rekeying Eric Rescorla
- Re: [tcpm] question about TCP-AO and rekeying Joe Touch
- Re: [tcpm] question about TCP-AO and rekeying Eric Rescorla
- Re: [tcpm] question about TCP-AO and rekeying Joe Touch
- Re: [tcpm] question about TCP-AO and rekeying Eric Rescorla
- Re: [tcpm] question about TCP-AO and rekeying Joe Touch
- Re: [tcpm] question about TCP-AO and rekeying Eric Rescorla
- Re: [tcpm] question about TCP-AO and rekeying Joe Touch
- Re: [tcpm] question about TCP-AO and rekeying Eric Rescorla
- Re: [tcpm] question about TCP-AO and rekeying Eddy, Wesley M. (GRC-MS00)[Verizon]
- Re: [tcpm] question about TCP-AO and rekeying Eric Rescorla
- Re: [tcpm] question about TCP-AO and rekeying Joe Touch
- Re: [tcpm] question about TCP-AO and rekeying Joe Touch