Vijay Devarapalli writes:
> > In section 6 it should be:
> >
> > (IP_R:500 -> IP_I:500)
> > <-- HDR(A,B), SK {IDr, [CERT,] AUTH,
> > N(REDIRECT, New_GW_ID,)}
>
> Fixed all of the above.
>
> > (Again changed the N[] to N()). This section does not say whether the
> > Ni is included in the response, but I assume it is omitted as there is
> > no need for it. This section should make it clear whether it is
> > included or omitted.
>
> It is included only in the IKE_SA_INIT response. Section 7.2 says
>
> The 'Nonce Data' field
> is present in the REDIRECT payload only when the REDIRECT payload is
> sent in the IKE_SA_INIT response message. It MUST NOT be included in
> the REDIRECT payload if sent in an IKE_AUTH response or in a gateway-
> initiated redirect message.
>
> I hope this is sufficient.
I found that later, but when I was reading the protocol description in
section 6 I was wondering whether the nonce is included or not. It
might be enough to explain that in the description of the payload
itself, especially now if the N(REDIRECT, New_GW_ID,) in example
clearly indicates nonce is empty.
>
> > In section 6 the text:
> >
> > In such cases, the gateway should send the REDIRECT notification
> > payload in the final IKE_AUTH response message that carries the AUTH
> > payload and the traffic selectors. The gateway MUST NOT send and the
> > client MUST NOT accept a redirect in an earlier IKE_AUTH message.
> >
> > is bit confusing. First it says the gateway (lowercase) should send
> > REDIRECT in final IKE_AUTH response that carries the AUTH payload and
> > traffic selectors. Then it says that gateway MUST NOT send redirect in
> > earlier messages.
> >
> > Firstly the final IKE_AUTH response willnot include the traffic
> > selectors, as they are omitted if client is redirected. Thus it is
> > misleading to say "that carries the AUTH payload and traffic
> > selectors".
>
> Please see my response to Pasi's email. This text has been updated. Redirect
> during the first IKE_AUTH response is always allowed even when EAP or
> multiple authentication is used.
The text was not very clear about this. I will wait to see next
version to see if that is clearer.
> > Secondly, it is not clear whether the "In such cases" only refers to
> > the cases wher gateway decides to do something (interact with AAA
> > server/ use external authentication server), or in all cases where EAP
> > or multiple authentication is used. If it is in all cases where EAP or
> > multiple authentication is used, then that means gateway cannot
> > redirect in first IKE_AUTH (which is fine for me, but I am not sure if
> > that was meant). If it is only when gateway needs AAA/external
> > authentication server, then how can client enforce the "MUST NOT
> > accept redirect in an earlier IKE_AUTH message", if it does not know
> > whether gateway needs to consult external authentication server or AAA
> > server...
> >
> > In general the text is so confusing that I am not sure what is meant.
> > One easy way to solve this problem is to say things clearly, i.e.
> > either add one of the following texts:
> >
> > If multiple IKE_AUTH exchanges are used the REDIRECT notification
> > payload MUST be in the IKE_AUTH response from gateway to the client,
> > which also includes the gateways AUTH payload. With EAP, there is
> > two possible places (first IKE_AUTH and last IKE_AUTH). With
> > multiple authentication support there are AUTH payload after each
> > authentication finished, thus server can redirect after each
> > authentication step is finished. REDIRECT notification MUST NOT be
> > sent or accepted in any other messages than those having AUTH
> > payload.
> >
> > or
> >
> > If multiple IKE_AUTH exchanges are used the REDIRECT notification
> > payload MUST be in the final IKE_AUTH response from the gateway to
> > the client, i.e the one that contains the AUTH payload, and that
> > would also contain the Child SA SA payload and traffic selectors,
> > if connection would not have redirected. REDIRECT notification MUST
> > NOT be sent or accepted in any of the earlier IKE_AUTH messages.
>
> If the gateway decides to redirect after the first authentication,
> it would be the same as the exchange in section 6. The second
> authentication would not even happen.
If initiator decides to use EAP, then the exchange is not same as in
section 6, as the initiator has not proven his identity yet. The first
authentication only authenticates the identity of the server.
If Shared secret or certificates are used then both ends identities
are authenticated during the first IKE_AUTH exchange.
With multiple authentications the server can at any point decided that
it has had enough authentication and ignore the ANOTHER_AUTH_FOLLOWS
wish from client (as far as I understand the rfc4739), thus it can at
any point when authentication is finished decided to finish the whole
IKE_SA creation and send final AUTH.
I think we need bit more text there explaining how this is supposed to
work.
> If the redirect is as a result of interaction with an external
> authentication server, then the redirect happens in the final
> IKE_AUTH message.
How is the client supposed to know whether server decides to redirect
as a result of interaction with an external authentication server, and
make sure server cannot redirect during first IKE_AUTH exchange.
The MUST in draft says that client MUST NOT accept redirect in any
earlier message.
As there is no way for client to know for this, there is no point of
putting such requirement there.
> I think we should use the same IANA registry for both.
...
> I added the following text to the IANA section.
>
> This document creates a new namespace called the "Gateway Identity
> Type". This is used to indicate the type of information regarding
> the VPN gateway that is carried in the REDIRECT Section 7.2 and
> REDIRECTED_FROM Section 7.3 Notification payloads. The following
> values are assigned.
>
> 1 - IPv4 address of the new VPN gateway
> 2 - IPv6 address of the new VPN gateway
> 3 - FQDN of the new VPN gateway
>
> Values '0', and 4-255 are reserved. New values can be allocated by
> expert review.
So FQDN is allowed in the REDIRECTED_FROM payload too?
It is bad idea to share the registries if they can have different
values. We already had this problem in the IKEv2, as the encryption
algorithms registry was shared with both IKEv2 and ESP, and not all of
the algorithms could be used in IKEv2 (combined mode ciphers), and the
registry didn't indicate this in any way.
So either use two registries, or specify explicitly which values are
usable in which payload.
--
kivi...@iki.fi
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