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Re: [Emu] Finishing draft-ietf-emu-eap-tls13 - Commitment Message handling

Jim Schaad <ietf@augustcellars.com> Mon, 13 July 2020 18:31 UTC

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From: Jim Schaad <ietf@augustcellars.com>
To: 'Mohit Sethi M' <mohit.m.sethi@ericsson.com>, emu@ietf.org
CC: 'Alan DeKok' <aland@deployingradius.com>, j@w1.fi, 'Roman Danyliw' <rdd@cert.org>, 'Hannes Tschofenig' <Hannes.Tschofenig@arm.com>
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Date: Mon, 13 Jul 2020 11:30:49 -0700
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Subject: Re: [Emu] Finishing draft-ietf-emu-eap-tls13 - Commitment Message handling
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My expectation would be that the third option from Hannes is what should be done.  The commit message should be encrypted and not a plain text message.

 

Jim

 

 

From: Mohit Sethi M <mohit.m.sethi@ericsson.com> 
Sent: Monday, July 13, 2020 10:44 AM
To: emu@ietf.org
Cc: Jim Schaad <ietf@augustcellars.com>; Alan DeKok <aland@deployingradius.com>; j@w1.fi; Roman Danyliw <rdd@cert.org>; Hannes Tschofenig <Hannes.Tschofenig@arm.com>
Subject: Finishing draft-ietf-emu-eap-tls13 - Commitment Message handling

 

Dear all,

draft-ietf-emu-eap-tls13 is currently in the state "AD Evaluation::AD Followup". Our AD (Roman) had done an excellent review (https://mailarchive.ietf.org/arch/msg/emu/k6K98OhuOQmbzSAgGWCtSIVv3Qk/), which I addressed in version 10 (https://mailarchive.ietf.org/arch/msg/emu/IopJTjefyVVKpObzyFc0CAJ-Pig/). 

The only outstanding issue is the handling of the commitment message. The current text in the draft says the following:

   When an EAP server has sent its last handshake message (Finished or a
   Post-Handshake), it commits to not sending any more handshake
   messages by sending a Commitment Message.  The Commitment Message is
   a TLS record with application data 0x00 (i.e. a TLS record with
   TLSPlaintext.type = application_data, TLSPlaintext.length = 1, and
   TLSPlaintext.fragment = 0x00).  Note that the length of the plaintext
   is greater than the corresponding TLSPlaintext.length due to the
   inclusion of TLSInnerPlaintext.type and any padding supplied by the
   sender.  EAP server implementations MUST set TLSPlaintext.fragment to
   0x00, but EAP peer implementations MUST accept any application data
   as a Commitment Message from the EAP server to not send any more
   handshake messages.  The Commitment Message may be sent in the same
   EAP-Request as the last handshake record or in a separate EAP-
   Request.  Sending the Commitment Message in a separate EAP-Request
   adds an additional round-trip, but may be necessary in TLS
   implementations that only implement a subset of TLS 1.3.


Hannes says that this is not ideal and cannot be achieved with mbed TLS 1.3 implementation. He made 3 alternative suggestions for achieving the functionality of the commitment message (https://mailarchive.ietf.org/arch/msg/emu/eM-14QdDQjg7DvhAVJMzpvPz5wg/).  

I would like to close this issue and would like to receive feedback from others who have commented before or are working on implementations: Jim, Alan, Jouni; please let us know what do you think about the change? 

--Mohit

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