Hi Tero,
Thank you very much for your feedback. I'm glad to see that your thoughts
concur with mine. It really helps.
Regards & Thanks！
Wei PAN (潘伟)
> -----Original Message-----
> From: Tero Kivinen <[email protected]>
> Sent: Tuesday, February 6, 2024 2:52 AM
> To: Panwei (William) <[email protected]>
> Cc: [email protected]
> Subject: [IPsec] What's the most reasonable way for the responder to
> handle the request containing unknown Key Exchange methods
>
> Panwei \(William\) writes:
> > The handling I suggest is as follows:
> >
> > 1) if all KE methods proposed by the initiator are unknown to the
> > responder, i.e., no KE method is acceptable, then the responder
> > replies NO_PROPOSAL_CHOSEN, no matter what KE method is used in the
> KE payload.
> >
> > 2) if at least one acceptable KE method is included in the
> > initiator’s proposals, the responder can select one acceptable KE
> > method, ignore the unknown KE methods, and perform the next step of
> KE Payload processing.
> >
> > 2.1) if the KE method used in the KE payload happens to be the
> > same as this selected KE method, then the responder normally replies
> > with this selected KE method and the corresponding KE payload.
> >
> > 2.2) if the KE method used in the KE payload is different from
> > this selected KE method, then the responder replies
> INVALID_KE_PAYLOAD
> > with this selected KE method, regardless of whether the KE method used
> > in the KE payload is known or unknown to the responder.
>
> This is correct processing.
>
> Note, that any unknown KE method cannot be accaptable for the policy,
> thus they are not allowed by the policy, and if there are any KE methods
> which are acceptable to policy we use that, and if the KE payload is not
> using that you send INVALID_KE_PAYLOAD and indicate the KE method you
> want to use.
>
> This processing is same for the known and unknown KE methods, there is
> no difference there.
>
> Of course the initiator will include the exactly same SA payload listing
all
> those unknown KE methods when it retries with the KE method listed in the
> INVALID_KE_PAYLOAD.
>
> > However, others suggest that the responder should terminate the IKE
> > exchange without reply, when the KE method used in the KE payload is
> > unknown to the responder, even if there are other acceptable KE
> > methods proposed in the SA payload.
>
> If there is anything in the RFC7296 that would suggest that kind of
> processing is valid, we need to fix that. The RFC7296 tries to be
extendable,
> thus it tries to ignore unknown values, and process things without them.
>
> For example in implementation I was familiar with there were not unknown
> algorithms, all values for algorithms or methods were valid from IKEv2
> point of view, and those values were then matched against policy, but of
> course policy only allowed values that implementation actually
> recognized...
>
> > Because they feel the unknown KE method in the KE payload means that
> > the whole packet is an invalid packet, and discarding this packet is
> > the thing to do.
>
> I have no idea where they think RFC7296 says anything like that.
> --
> [email protected]
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