Subject: RE: [Ipsec] REKEY_SA Notify clarification wanted

From: [email-masked]
Date: Tue, 2 Aug 2005 15:31:50 +0300

Tero Kivinen wrote:
> Fukumoto Atsushi writes:
> > draft-ietf-ipsec-ikev2-17.txt says:
> > in section 1.3:
> >    If this CREATE_CHILD_SA exchange is rekeying an existing 
> >    SA other than the IKE_SA, the leading N payload of type 
> >    REKEY_SA MUST identify the SA being rekeyed. If this 
> >    CREATE_CHILD_SA exchange is not rekeying an existing SA, 
> >    the N payload MUST be omitted.
> > 
> > and in section 3.10.1:
> >         REKEY_SA                                 16393
> > 
> >             This notification MUST be included in a CREATE_CHILD_SA
> >             exchange if the purpose of the exchange is to replace
> >             an existing ESP or AH SA. The SPI field identifies 
> >             the SA being rekeyed. There is no data.
> > 
> > These are the only mentions of REKEY_SA, and I found it hard to
> > figure out what to do when rekeying IKE SA.  The above
> > descriptions strongly suggests (to me) that the REKEY_SA is not
> > used in IKE SA rekeying.
> 
> When you are rekeying IKE SA you do not include N(REKEY_SA) at
> all. It is only included when you are rekeying ESP or AH SA (as the
> section 3.10.1 and 1.3 say).

I think the text could be interpreted both ways. Since it says
"REKEY_SA is not included when you're not rekeying an existing SA",
that could imply that it is included when you are rekeying.
But it's not really needed, since the fact you're rekeying the 
IKE_SA is anyway obvious from the SA payload.

Is there any information how existing implementations have
interpreted this? (e.g. from the Santa Clara bakeoff?)

(The one implementation I know of did not send REKEY_SA in this case.)

Best regards,
Pasi

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From: Tero Kivinen <[email-masked]>
Date: Tue, 2 Aug 2005 16:52:40 +0300

> I think the text could be interpreted both ways. Since it says

If it says "rekeying an existing SA other than the IKE_SA", I do not
know how it can be interpreted to include also rekeying IKE_SA?

> that could imply that it is included when you are rekeying.

But the text who said to add it had "other than the IKE_SA".

> interpreted this? (e.g. from the Santa Clara bakeoff?)

I do not remember anybody using REKEY_SA on IKE_SA rekeys in the
bakeoff, but I might be wrong...

-- 
[email-masked]

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From: Fukumoto Atsushi <[email-masked]>
Date: Wed, 03 Aug 2005 13:11:01 +0900

> interpreted this? (e.g. from the Santa Clara bakeoff?)

I had no problem of interpreting the IKEv2 draft that way.  The only
reason I was confused is due to the clarification draft appendix A.5
which has N(REKEY) for rekeying IKE_SA, since I considered the
clarification draft is supposed to be clarifying the protocol.  This
appendix was included from draft-03, dated June 1 2005, so the
implementation prior to that should have had no influence from this.

					FUKUMOTO Atsushi
					[email-masked]