eap Mailing List: Re: Keying lifetimes (WG LC "Keying Fwk")

[Bernard Aboba (bernard_aboba]

> Alper: We shall not present this (a) as if it is a complete mechanism that
> can manage key lifetimes on all relevant parties (peer, authenticator,
> authentication server). This only provides the MSK lifetime to the
> authenticator. Only when coupled with how peer learns the key lifetime for
> MSK and EMSK we'd have a complete solution.

Right.

> Alper: I think what I'm suggesting is to enumerate these alternatives, such
> that (a) appears under "how authenticator dynamically learns the MSK
> lifetime."

This makes sense.

> Alper: Secure Association Protocol is a "consumer" of MSK. For that, I 
> don't
> expect it to set the any attributes of the MSK it is "using." Doing
> otherwise is a hack, IMHO. I recommend we remove the current text from this
> option.

In practice the SAP handles this in a number of cases, including IKEv2, 
802.16e, and 11r.   So I don't think we can leave it out.

> Alper: But, we shall retain the option. IMO, the technically correct way of
> doing this is not via the "secure association" protocol, but via the "eap
> transport". The lifetime learned from the authentication server via AAA
> protocols can be conveyed to the EAP peer via such protocols. If people
> agree, I can propose text.

We should probably describe this as another option.

> [d]  Method specific negotiation within EAP.  While EAP itself does not
>      support lifetime negotiation, it would be possible to specify
>      methods that do.  However, systems that rely on such negotiation
>      for exported keys would only function with these methods.  In the
>      interest of method independence, key management of exported or
>      derived keys SHOULD NOT be provided within EAP methods.
>
> Alper: again, this is all about how peer and authentication server agrees 
> on
> the MSK and EMSK lifetimes. It does not help the authenticator. We shall
> categorize this mechanism as such.

Yes.  In fact, it might create problems if *both* the method and 
SAP/transport are trying to negotiate the lifetime.  Do you have text to 
suggest?

> Alper: Besides, what is the interaction between the lifetimes known and
> delivered by the EAP methods and the AAA protocols?  My understanding is, 
> EAP
> methods may export lifetimes, and the AAA protocol has the last say whether
> the lifetime should be same as reported by the EAP method, or something
> less. This is all about the "authorization" aspect.

Right.  Another potential conflict.