Subject: RE: [Ipsec] certificate payloads/requests in IKEv2

From: [email-masked]
Date: Tue, 27 Sep 2005 10:23:07 +0300

Paul Hoffman wrote:
> At 5:48 PM +0300 9/26/05, [email-masked] wrote:
> >About CERT, it seems that it's not allowed: Section 1.2 says that
> >"If any CERT payloads are included, the first certificate
> >provided MUST contain the public key used to verify the AUTH
> >field" (which it can't contain if the AUTH field is shared secret
> >based). And it wouldn't make any sense anyway (at least with
> >X.509/raw RSA key CERT types)...
> 
> That sentence from the spec can be read sensibly in two fashions:
> 
> - If any CERT payloads are included and public keys are being used 
> for authentication, then the first certificate provided is the one 
> that contains the public key used to verify the AUTH field.
> 
> - If any CERT payloads are included, that means that public keys are 
> being used for authentication, and that the first certificate 
> provided is the one that contains the public key used to verify the 
> AUTH field.
> 
> I read the sentence the first way, definitely. I cannot find anything 
> on the mailing list that says that we intended the existence of a 
> CERT payload to be a MUST-level signal that we were using public key 
> authentication.

True, both ways seem sensible. And of course following the "be liberal 
in what you accept" principle would mean that if you receive CERT 
payloads when doing shared secret authentication, you should just
ignore the CERTs (instead of failing the exchange).

However, if an implementation sends CERTs when it's using shared
secret authentication, and actually expects the peer to do something
with the certificates, then those expectations are IMHO not justified
by the IKEv2 spec... (which means that sending the CERTs is not
necessary)

Best regards,
Pasi

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---

From: Paul Hoffman <[email-masked]>
Date: Tue, 27 Sep 2005 08:00:37 -0700

>ignore the CERTs (instead of failing the exchange).

Right.

>by the IKEv2 spec... (which means that sending the CERTs is not

Of course it is not necessary, but it might happen due to some 
mis-implementation. As you said above, the certs should just be 
ignored.

--Paul Hoffman, Director
--VPN Consortium