Hi Yaron,

Thanks for the comments, Ticket#205 create to track this.

On Thu, Nov 11, 2010 at 8:46 PM, Yaron Sheffer <[email protected]>wrote:

> Hi,
>
> it seems to me we have created an overly complicated solution for replay
> protection of the Msg ID = 0 messages. Specifically, I think both the
> failover counter and the nonce can be eliminated.
>
> Since the messages are protected under the IKE SA, we just need to ensure
> that in a correct run of the protocol, there is never any need to repeat
> previous messages. This can be done by including *both* Msg ID counters in
> each message, and specifying a few rules to make sure counters never go
> backwards.
>
> Cluster member to client:
> - The counter I plan to use next (based on a traffic/rekey rate estimate,
> must be higher than the last message that was actually sent, otherwise it
> might be rejected)
>

It will be better to jump this counter by IKEv2 Message Send Window size
rather than measuring or guessing traffic here.


> - The counter I think you will use next (the last known value, as received
> from the failed cluster member)
>
> Client to cluster:
> - The counter I really plan to use next (must be equal to or higher than
> the received value)
> - The counter you said you will use next
>
> And each side must accept incoming messages only if both values are equal
> to or larger than the corresponding one previously received from the same
> peer, and one of them is strictly larger than the previous value.
>
> Am I missing anything?
>
> Thanks,
>    Yaron
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