Subject: [IPsec] Issue #15: Message ID reset to 0 after IKE SA rekey

From: Yoav Nir <[email-masked]>
Date: Mon, 22 Sep 2008 17:57:52 +0300

I think this is one we can easily get out of the way.

Tero said:
>> 2.2.  Use of Sequence Numbers for Message ID
>>
>>    The Message ID is a 32-bit quantity, which is zero for the
>>    IKE_SA_INIT messages (including retries of the message due to
>>    responses such as COOKIE and INVALID_KE_PAYLOAD {{ Clarif-2.2 }}),
>>    and incremented for each subsequent exchange.
>
> Add text:
>
>    The Message ID is reset to zero also after IKE SA rekey for the new
>    IKE SA.
>

However, if you read section 2.2 to the end, it says:
>    Note that Message IDs are cryptographically protected and provide
>    protection against message replays.  In the unlikely event that
>    Message IDs grow too large to fit in 32 bits, the IKE_SA MUST be
>    closed.  Rekeying an IKE_SA resets the sequence numbers.

IMO the last sentence already says what Tero wants to add, so it's  
just a matter of phrasing.

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From: Tero Kivinen <[email-masked]>
Date: Tue, 23 Sep 2008 13:49:21 +0300

> just a matter of phrasing.

There were some implementors who missed the resetting message IDs
text. I can understand why they did so, as now it is hidden at the end
of section in the paragraph talking about very unlikely event of
message IDs wrapping. Most implementors will just see that this talks
about unlikely events, so they do not need to care about it, and don't
realize that the resetting of message IDs after rekeying an IKE SA is
something they do need to implement. So I want to move that text to
the main part of the message ID description not to the special case
description.
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From: Yoav Nir <[email-masked]>
Date: Tue, 23 Sep 2008 13:59:33 +0300

> the main part of the message ID description not to the special case

I think that's a good idea, although what would they use for the  
initial message ID for the new IKE SA.  A random value?  The MsgIDs  
from the old SA?

Paul, I think we can accept this and move that last sentence to the  
main part of the message ID description.
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From: Tero Kivinen <[email-masked]>
Date: Tue, 23 Sep 2008 17:21:08 +0300

> initial message ID for the new IKE SA.  A random value?  The MsgIDs  

They used the message id from old SA.

Some also misread the "The IKE_SA initial setup messages will always
be number 0 and 1." to mean that no other messages can be with message
id 0 or 1 than those IKE SA setup messages (i.e. they had special
handling for message id 0 packets).

---

From: Yaron Sheffer <[email-masked]>
Date: Tue, 23 Sep 2008 18:32:25 +0300

In case you were wondering, the ipsecme Issue Tracker is available at:
http://trac.tools.ietf.org/wg/ipsecme/trac/report

Right now all we have is Tero's comments on IKEv2-bis. But there are more
coming.

Thanks,

      Yaron

-----Original Message-----
From: [email-masked] [mailto:[email-masked]] On Behalf Of
Tero Kivinen
Sent: Tuesday, September 23, 2008 17:21
To: Yoav Nir
Cc: [email-masked]; Paul Hoffman
Subject: Re: [IPsec] Issue #15: Message ID reset to 0 after IKE SA rekey

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From: Paul Hoffman <[email-masked]>
Date: Tue, 23 Sep 2008 09:03:08 -0700

I'm fine with moving the current sentence up to the place where it is 
more useful.

--Paul Hoffman, Director
--VPN Consortium