Hi Valery,

Thanks for your clarification.

As “support” is not equal to “is configured to use”, I suggest the following 
modifications to the paragraph below in section 3.1, because the responder 
supporting both specifications can choose none to use if it is configured not 
to use PPK.

OLD:
   Note, that this negotiation is independent from negotiation of using
   PPKs in the IKE_AUTH exchange.  The initiator that supports both use
   PPKS in IKE_AUTH [RFC8784] and use PPKS in IKE_INTERMEDIATE MAY
   include both the USE_PPK_INT (along with the
   INTERMEDIATE_EXCHANGE_SUPPORTED) and the USE_PPK notifications if it
   is configured to use either specification.  However, the responder
   supporting both specifications have to choose one to use, thus it
   MUST return either USE_PPK_INT or USE_PPK notification in the
   response, but not both.

NEW:
   Note, that this negotiation is independent from negotiation of using
   PPKs in the IKE_AUTH exchange.  The initiator that supports both use
   PPKS in IKE_AUTH [RFC8784] and use PPKS in IKE_INTERMEDIATE MAY
   include both the USE_PPK_INT (along with the
   INTERMEDIATE_EXCHANGE_SUPPORTED) and the USE_PPK notifications if it
   is configured to use either specification.  However, if the responder
   supports both specifications and is configured to use PPKs, it has to choose 
one to use, thus it
   MUST return either USE_PPK_INT or USE_PPK notification in the
   response, but not both.

Regards & Thanks!
Wei PAN (潘伟)

From: Valery Smyslov <smyslov.i...@gmail.com>
Sent: Thursday, November 14, 2024 3:34 PM
To: Panwei (William) <william.pan...@huawei.com>
Cc: ipsec@ietf.org
Subject: RE: Review of draft-ietf-ipsecme-ikev2-qr-alt-04

Hi William,

thank you for your review.

Hi Valery,

Previously, I’ve reviewed this draft before the working group adoption. I’ve 
reviewed the lasted version and I think it’s in the good shape.

Here I have only two questions for your confirmation.


  1.  If the initiator proposes USE_PPK_INT in the request but the responder 
doesn’t include it in the response, then the initiator still includes 
PPK_IDENTITY_KEY when creating the Child SA, how should the responder process 
at this time? The other similar situation

If the responder doesn’t include USE_PPK_INT, then it either doesn’t support 
this extension or is not configured to use it.
In both cases it will ignore PPK_IDENTITY_KEY as unknown status notification 
(in the second case – it is “unknown” notification in the current context).


  1.  is that the initiator doesn’t include USE_PPK_INT when creating the 
IKE_SA but includes PPK_IDENTITY_KEY when creating the Child SA. Should the 
responder reply with NO_PROPOSAL_CHOSEN, or ignore the PPK_IDENTITY_KEY and 
process as usual?

Using PPKs in CRETE_CHILD_SA is independent from using them in initial 
exchanges. Thus, it doesn’t matter for this case whether USE_PPK_INT was 
included in IKE_SA_INIT or not.
If the responder does not supports using PPKs in CREATE_CHILD_SA or is not 
configured to use them, it will ignore PPK_IDENTITY_KEY.
If the responder supports using PPKs in CREATE_CHILD_SA, but the initiator did 
not include any PPK_IDENTITY_KEY in the request (or included “wrong” PPKs),
then, in case using PPKs is mandatory for the responder, it replies with 
NO_PROPOSAL_CHOSEN.


  1.  Currently, PPK confirmation in the PPK_IDENTITY_KEY is only generated by 
the initiator and validated by the responder, is there a need to let the 
responder generate a new PPK confirmation in the response and validated by the 
initiator?

No, this asymmetry is intentional. The purpose of PPK confirmation is to avoid 
situations when due to PPK values mismatch (as result of misconfiguration)
the responder cannot even decrypt the following request and respond with an 
error notification. Thus, checking PPK confirmation assures the responder that
the protocol can always complete, even in case of errors. There is no point to 
send PPK confirmation in the opposite direction – it gives no new information
to initiator and only complicates protocol (e.g. – what to do if the responder 
sends back a different confirmation for the key – how proceed with this?).

One nit in the second paragraph in section 3.2: s/THe PPK Confirmation/The PPK 
Confirmation.

         Fixed, thank you.

         Regards,
         Valery.

Regards & Thanks!
Wei PAN (潘伟)

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