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Re: reliable notify question
Brian,
If you considering chances for generating the same message IDs on both ends -
this will break lots of things in IKE - not just reliable notifies.
"Brian Swander (Exchange)" wrote:
> There is a small problem with this. It is perhaps so small as to be
> irrelevant, but I'll let you decide.
>
> Say both peers (A and B) decide send a reliable delete on the same SA at
> approx. the same time. By a fluke, both generate the same random mess_id
> for the message. Now, each sends delete expecting an ACK. When B gets A's
> message, he will expect it to be an ACK, since the mess_id is the same as
> the message he sent. B will therefore try to verify the hash, and fail,
> since it was in reality a new notify, not an ACK, from A. Similarily for A
> processing B's notify.
>
> Again, I don't know if we care, since the odds of this occurring are slim.
> However, it will break processing of these notifies. A fix is to
> distinguish in the payload the difference between an new notify and an ACK,
> perhaps as a flag in the header. However, adding such a flag makes
> backwards compatibility much harder. Is there any other good solution that
> still preserves the relatively simple backwards compatability?
>
> bs
>
> -----Original Message-----
> From: Dan Harkins [mailto:dharkins@network-alchemy.com]
> Sent: Monday, October 04, 1999 5:39 PM
> To: Brian Swander (Exchange)
> Cc: 'ipsec@lists.tislabs.com'
> Subject: Re: reliable notify question
>
> They have to be the same, just like all the other exchanges. Otherwise
> there would be no way to distinguish a response to your notify from a
> newly initiated notify from the peer.
>
> Dan.
>
> On Mon, 04 Oct 1999 13:11:23 PDT you wrote
> > Also, MUST the message_id in the responders ACK be the same as the
> > message_id in the initiator's N/D, or MUST the message_ids be different?
> >
> > I'd argue for the former, since it will allow easier lookups, and I doubt
> > there are any security issues with the duplicate mess_id.
> >
> > bs
> >
> > -----Original Message-----
> > From: Brian Swander (Exchange)
> > Sent: Monday, October 04, 1999 10:11 AM
> > To: 'Dan Harkins'
> > Cc: ipsec@lists.tislabs.com
> > Subject: reliable notify question
> >
> >
> > Pardon me if this has been asked before.
> >
> > In section 6.4.2 of the new IKE draft on reliable notifies, it says we
> need
> > to use the initiator and responder nonces in constructing the messages.
> >
> > Initiator Responder
> > ----------- -----------
> > HDR*, HASH(1), Ni, N/D -->
> > <-- HDR*, HASH(2), Nr, N/D
> >
> > First, are these values the nonces that were already exchanged, or are
> they
> > newly generated for each reliable notify? I presume the former.
> >
> > If I am right so far, which nonce do we use, the MM nonces, or the QM
> > nonces? I assume that we always use the MM nonce, since notifies are only
> > really bound to the MM, and not to any particular QM.
> >
> > Is this correct?
> >
> > bs
> >
> >
References: