[Emu] TEAP - RFC 7170 - Errata

[Oleg Pekar <[e-mail]>]

Hi Jouni,
You filed Errata ID: 5767, 5844, 5845 regarding sending of
Intermediate-Result TLV. Can we clarify a general scheme of
sending Intermediate-Result TLV and Crypto-Binding TLV in all cases? It is
not exactly clear what is "EAP authentication method" and what is its
different from "EAP method" (you referred to appendix C.3 as an example of
"EAP Method" but it is not clear why it is not an "EAP authentication
method" - could you please clarify).

Here's the list of cases with the current RFC instructions (please add if
something is missing):

1. A single inner EAP method is executed inside the tunnel.
*** RFC says ***
Section 4.2.11 "An Intermediate-Result TLV indicating success MUST be
accompanied by a Crypto-Binding TLV". Section 3.3 "Phase 2 MUST always end
with a Crypto-Binding TLV exchange"

2. Multiple inner EAP methods are executed inside the tunnel.
*** RFC says ***
Send Intermediate-Result TLV if more than one method is going to be
executed in the tunnel. Send Crypto-Binding TLV if Intermediate-Result TLV
indicates success.
Section 3.3.1 "If more than one method is going to be executed in the
tunnel, then upon method completion, the server MUST send an
Intermediate-Result TLV indicating the result" - wrong
Section 3.3.3 "The Crypto-Binding TLV and Intermediate-Result TLV MUST be
included to perform cryptographic binding after each successful EAP method
in a sequence of one or more EAP methods" - correct

3. Basic Password Authentication (using Basic-Password-Auth-Req/Response)
is executed inside the tunnel
*** RFC says ***
Send Intermediate-Result TLV.
Section 3.3.2 "Upon receiving the response, the server indicates the
success or failure of the exchange using an Intermediate-Result TLV" - thus
Crypto-Binding TLV MUST be also sent as quoted in #1.

4. No inner EAP method is executed inside the tunnel.
*** RFC says ***
Section 3.3.3 "A successful TEAP Phase 2 conversation MUST always end in a
successful Crypto-Binding TLV and Result TLV exchange.  A TEAP server may
initiate the Crypto-Binding TLV and Result TLV exchange without initiating
any EAP conversation in TEAP Phase 2"
Section 4.2.13 "The Crypto-Binding TLV MUST be exchanged and verified
before the final Result TLV exchange, regardless of whether there is an
inner EAP method authentication or not"

******
Jouni, you provided multiple suggestions for fixing this. Incorporating you
suggestions, the bottomline could be:
* Send Intermediate-Result TLV after each inner EAP method but not after Basic
Password Authentication TLV exchange
* Send Crypto-Binding TLV based on inner method MSK/EMSK after each inner
EAP method that exports MSK/EMSK and send Crypto-Binding TLV based on
Zero-MSK in case of no inner method was executed

And then it should be declared explicitly and all the places where these
TLV are mentioned can be fixed accordingly.

Please share your opinion.
~ Oleg