Re: [stir] Benjamin Kaduk's Discuss on draft-ietf-stir-enhance-rfc8226-03: (with DISCUSS and COMMENT)

Russ Housley <housley@vigilsec.com> Sat, 03 July 2021 18:27 UTC

Return-Path: <housley@vigilsec.com>
X-Original-To: stir@ietfa.amsl.com
Delivered-To: stir@ietfa.amsl.com
Received: from localhost (localhost [127.0.0.1]) by ietfa.amsl.com (Postfix) with ESMTP id 9F03E3A1F6D for <stir@ietfa.amsl.com>; Sat, 3 Jul 2021 11:27:46 -0700 (PDT)
X-Virus-Scanned: amavisd-new at amsl.com
X-Spam-Flag: NO
X-Spam-Score: -1.898
X-Spam-Level:
X-Spam-Status: No, score=-1.898 tagged_above=-999 required=5 tests=[BAYES_00=-1.9, SPF_HELO_NONE=0.001, SPF_NONE=0.001] autolearn=unavailable autolearn_force=no
Received: from mail.ietf.org ([4.31.198.44]) by localhost (ietfa.amsl.com [127.0.0.1]) (amavisd-new, port 10024) with ESMTP id i7UadJzNTXMw for <stir@ietfa.amsl.com>; Sat, 3 Jul 2021 11:27:44 -0700 (PDT)
Received: from mail.smeinc.net (mail.smeinc.net [209.135.209.11]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by ietfa.amsl.com (Postfix) with ESMTPS id A393E3A1F6E for <stir@ietf.org>; Sat, 3 Jul 2021 11:27:44 -0700 (PDT)
Received: from localhost (localhost [127.0.0.1]) by mail.smeinc.net (Postfix) with ESMTP id 1D3C6300BF0 for <stir@ietf.org>; Sat, 3 Jul 2021 14:27:44 -0400 (EDT)
X-Virus-Scanned: amavisd-new at mail.smeinc.net
Received: from mail.smeinc.net ([127.0.0.1]) by localhost (mail.smeinc.net [127.0.0.1]) (amavisd-new, port 10026) with ESMTP id yVCzYSYNTvzW for <stir@ietf.org>; Sat, 3 Jul 2021 14:27:38 -0400 (EDT)
Received: from a860b60074bd.fios-router.home (pool-141-156-161-153.washdc.fios.verizon.net [141.156.161.153]) by mail.smeinc.net (Postfix) with ESMTPSA id D0D18300512; Sat, 3 Jul 2021 14:27:37 -0400 (EDT)
Content-Type: text/plain; charset=us-ascii
Mime-Version: 1.0 (Mac OS X Mail 12.4 \(3445.104.21\))
From: Russ Housley <housley@vigilsec.com>
In-Reply-To: <20210703175454.GY17170@mit.edu>
Date: Sat, 3 Jul 2021 14:27:37 -0400
Cc: IETF STIR Mail List <stir@ietf.org>, Ben Campbell <ben@nostrum.com>, IESG <iesg@ietf.org>, Robert Sparks <rjsparks@nostrum.com>
Content-Transfer-Encoding: quoted-printable
Message-Id: <2C4680EE-B72E-4263-A3EA-C81595130CFD@vigilsec.com>
References: <162491913776.24561.10295832590740387025@ietfa.amsl.com> <17CC8994-103E-4EA6-BF43-624F0A08FD5B@vigilsec.com> <20210629050839.GC17170@kduck.mit.edu> <A46901E1-E0B6-45FB-B70A-70771643BC5B@vigilsec.com> <20210629140724.GE17170@kduck.mit.edu> <43571C73-38E6-4B58-9BE6-536B83C35CCF@vigilsec.com> <20210703175454.GY17170@mit.edu>
To: Ben Kaduk <kaduk@mit.edu>
X-Mailer: Apple Mail (2.3445.104.21)
Archived-At: <https://mailarchive.ietf.org/arch/msg/stir/LRae_kqYyuhovxjqmAdFhDooiOI>
Subject: Re: [stir] Benjamin Kaduk's Discuss on draft-ietf-stir-enhance-rfc8226-03: (with DISCUSS and COMMENT)
X-BeenThere: stir@ietf.org
X-Mailman-Version: 2.1.29
Precedence: list
List-Id: Secure Telephone Identity Revisited <stir.ietf.org>
List-Unsubscribe: <https://www.ietf.org/mailman/options/stir>, <mailto:stir-request@ietf.org?subject=unsubscribe>
List-Archive: <https://mailarchive.ietf.org/arch/browse/stir/>
List-Post: <mailto:stir@ietf.org>
List-Help: <mailto:stir-request@ietf.org?subject=help>
List-Subscribe: <https://www.ietf.org/mailman/listinfo/stir>, <mailto:stir-request@ietf.org?subject=subscribe>
X-List-Received-Date: Sat, 03 Jul 2021 18:27:47 -0000

Ben:

>>>>>> 
>>>>>>> ----------------------------------------------------------------------
>>>>>>> DISCUSS:
>>>>>>> ----------------------------------------------------------------------
>>>>>>> 
>>>>>>> Let's discuss whether we should have content in this document discussing
>>>>>>> the relationship between this new certificate extension and the
>>>>>>> extension defined by RFC 8226.  In paticular, whether it is
>>>>>>> permitted/expected for both extensions to appear in the same
>>>>>>> certificate, and whether any specific processing is required in that
>>>>>>> case.  (If no such processing is specified, we could end up with
>>>>>>> interesting edge cases where a given PASSporT is handled differently
>>>>>>> depending on which extension(s) are supported by the recipient.)
>>>>>> 
>>>>>> I see no reason why both extensions would ever appear in the same certificate.
>>>>> 
>>>>> There was an open question for me about backwards compatibility...
>>>>> 
>>>>>> If there is a mustExclude, then the constraints cannot be expressed in the extension defined in RFC 8226, so I would only expect the on in this document to be present.
>>>>> 
>>>>> ... specifically, if the desired constraints include both mustExclude and
>>>>> one of the preexisting restrictions, does "something is better than
>>>>> nothing" apply when the recipient might not implement the new extension,
>>>>> prompting a desire to include both extensions so that the recipient will
>>>>> apply those constraints it does know about?
>>>> 
>>>> No.  It is important that all of the constraints are met for the use cases where mustExclude come into play.
>>> 
>>> It seems like that might be worth mentioning as the intended use, as well.
>> 
>> I think that the text in Section 1 does that:
>> 
>>   The Enhanced JWT Claim Constraints certificate extension is needed to
>>   limit the authority when a parent STIR certificate delegates to a
>>   subordinate STIR certificate.  For example,
>>   [I-D.ietf-stir-cert-delegation] describes the situation where service
>>   providers issue a STIR certificate to enterprises or other customers
>>   to sign PASSporTs, and the Enhanced JWT Claim Constraints certificate
>>   extension can be used to prevent specific claims from being included
>>   in PASSporTs and accepted as valid by the PASSporT recipient.
>> 
>> What do you think needs to be added?
> 
> It has become much less important now that the two extensions MUST NOT
> both appear in the same certificate, since that has implicitly made a value
> judgement on the importance of supporting all of the constraints
> simultaneously.
> 
> But the quoted text from Section 1 seems to only say that there is a need
> to use this extension for the delegation case (for the new behavior); it
> seems indifferent on whether it's important to have all the constraints
> together so that either all the constraints are applied or none are.  Just
> based on this description, it would be just as effective to put the new
> constraint in the new extension and put the other constraints in the
> preexisting extension.  Obviously that's not possible given the "MUST NOT
> both appear", so I'm not going to push for additional text on this point.

Delegation is the use case that caused this to be written now, but it is unclear whether other situations will make use of this capability.

Since this thread started, Chris Wendt shared with the STIR WG that an ATIS document is mandating implementation of The Enhanced JWT Claim Constraints certificate extension, so I think we will be in a good place.

Russ