Re: [OAUTH-WG] Martin Duke's No Objection on draft-ietf-oauth-access-token-jwt-12: (with COMMENT)

Benjamin Kaduk <> Thu, 08 April 2021 19:12 UTC

Return-Path: <>
Received: from localhost (localhost []) by (Postfix) with ESMTP id F146F3A17EC; Thu, 8 Apr 2021 12:12:35 -0700 (PDT)
X-Virus-Scanned: amavisd-new at
X-Spam-Flag: NO
X-Spam-Score: -1.498
X-Spam-Status: No, score=-1.498 tagged_above=-999 required=5 tests=[BAYES_00=-1.9, KHOP_HELO_FCRDNS=0.399, SPF_HELO_NONE=0.001, SPF_NONE=0.001, URIBL_BLOCKED=0.001] autolearn=no autolearn_force=no
Received: from ([]) by localhost ( []) (amavisd-new, port 10024) with ESMTP id YgRtGOpxcB5x; Thu, 8 Apr 2021 12:12:31 -0700 (PDT)
Received: from ( []) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by (Postfix) with ESMTPS id 8C4B13A17AF; Thu, 8 Apr 2021 12:12:31 -0700 (PDT)
Received: from ([]) (authenticated bits=56) (User authenticated as kaduk@ATHENA.MIT.EDU) by (8.14.7/8.12.4) with ESMTP id 138JCNYG032272 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-GCM-SHA384 bits=256 verify=NOT); Thu, 8 Apr 2021 15:12:28 -0400
Date: Thu, 08 Apr 2021 12:12:23 -0700
From: Benjamin Kaduk <>
To: Martin Duke <>
Cc: The IESG <>,,,
Message-ID: <>
References: <>
MIME-Version: 1.0
Content-Type: text/plain; charset="us-ascii"
Content-Disposition: inline
In-Reply-To: <>
Archived-At: <>
Subject: Re: [OAUTH-WG] Martin Duke's No Objection on draft-ietf-oauth-access-token-jwt-12: (with COMMENT)
X-Mailman-Version: 2.1.29
Precedence: list
List-Id: OAUTH WG <>
List-Unsubscribe: <>, <>
List-Archive: <>
List-Post: <>
List-Help: <>
List-Subscribe: <>, <>
X-List-Received-Date: Thu, 08 Apr 2021 19:12:36 -0000

On Thu, Apr 01, 2021 at 01:32:08PM -0700, Martin Duke via Datatracker wrote:
> Martin Duke has entered the following ballot position for
> draft-ietf-oauth-access-token-jwt-12: No Objection
> When responding, please keep the subject line intact and reply to all
> email addresses included in the To and CC lines. (Feel free to cut this
> introductory paragraph, however.)
> Please refer to
> for more information about IESG DISCUSS and COMMENT positions.
> The document, along with other ballot positions, can be found here:
> ----------------------------------------------------------------------
> ----------------------------------------------------------------------
> (2.1) "...can use any signing algorithm." I presume there ought to be some
> qualifiers on allowed algorithms?
> (4) and (5) "This specification
>    does not provide a mechanism for identifying a specific key as the
>    one used to sign JWT access tokens."
> I don't understand; there's a key ID right there in the token header?

The concern here is about identifying keys authorized to sign JWS access
tokens.  The server-provided metadata that lists such keys has a single
bucket that covers keys used for signing different things, so you don't get
any security benefit from key isolation, and a compromise of any of the
(other) keys listed by the server would allow the attacker to sign JWT
access tokens that are accepted as valid.

So in a sense this is not about which key was actually used, but rather
which key is supposed to be used.

> (4) I presume it's important that any resouree server rejection of the token
> should be constant-time. Is this somewhere in the RFC tree, or do we need to
> explicitly say it here and/or in Security Considerations?

(A good question, but I don't actually have the answer handy in memory.)