Re: [TLS] Consensus Call on draft-ietf-tls-dnssec-chain-extension

Nico Williams <nico@cryptonector.com> Thu, 05 April 2018 02:34 UTC

Return-Path: <nico@cryptonector.com>
X-Original-To: tls@ietfa.amsl.com
Delivered-To: tls@ietfa.amsl.com
Received: from localhost (localhost [127.0.0.1]) by ietfa.amsl.com (Postfix) with ESMTP id 0ACDD12D947 for <tls@ietfa.amsl.com>; Wed, 4 Apr 2018 19:34:31 -0700 (PDT)
X-Virus-Scanned: amavisd-new at amsl.com
X-Spam-Flag: NO
X-Spam-Score: -1.901
X-Spam-Level:
X-Spam-Status: No, score=-1.901 tagged_above=-999 required=5 tests=[BAYES_00=-1.9, RCVD_IN_DNSWL_NONE=-0.0001, RCVD_IN_MSPIKE_H2=-0.001] autolearn=ham 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 qz1Eh0mt2H4l for <tls@ietfa.amsl.com>; Wed, 4 Apr 2018 19:34:29 -0700 (PDT)
Received: from homiemail-a77.g.dreamhost.com (sub4.mail.dreamhost.com [69.163.253.135]) (using TLSv1.1 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by ietfa.amsl.com (Postfix) with ESMTPS id 97CC812DA29 for <tls@ietf.org>; Wed, 4 Apr 2018 19:34:29 -0700 (PDT)
Received: from homiemail-a77.g.dreamhost.com (localhost [127.0.0.1]) by homiemail-a77.g.dreamhost.com (Postfix) with ESMTP id 161E3A00400F; Wed, 4 Apr 2018 19:34:29 -0700 (PDT)
Received: from localhost (cpe-70-123-158-140.austin.res.rr.com [70.123.158.140]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) (Authenticated sender: nico@cryptonector.com) by homiemail-a77.g.dreamhost.com (Postfix) with ESMTPSA id 442D2A000B3C; Wed, 4 Apr 2018 19:34:28 -0700 (PDT)
Date: Wed, 04 Apr 2018 21:20:07 -0500
From: Nico Williams <nico@cryptonector.com>
To: Eric Rescorla <ekr@rtfm.com>
Cc: TLS WG <tls@ietf.org>
Message-ID: <20180405022007.GG25259@localhost>
References: <CAOgPGoAhzEtxpW5mzmkf2kv3AcugNy0dAzhvpaqrTSuMSqWqfw@mail.gmail.com> <EDB0F480-1272-4364-9A3D-23F9E1A02141@dukhovni.org> <CABkgnnWBdp=KtmBVDcrR9-5tdVPfhWG7pWR0FE57H=iWS37dWw@mail.gmail.com> <C52564E1-ABCD-4E1A-8517-19743BD2180B@dukhovni.org> <CABcZeBMcvtQ6Ko-2Rmoq3BSVBOqdQwJ65vVrPK0cpSJ9nQCS3w@mail.gmail.com>
MIME-Version: 1.0
Content-Type: text/plain; charset="us-ascii"
Content-Disposition: inline
In-Reply-To: <CABcZeBMcvtQ6Ko-2Rmoq3BSVBOqdQwJ65vVrPK0cpSJ9nQCS3w@mail.gmail.com>
User-Agent: Mutt/1.5.24 (2015-08-30)
Archived-At: <https://mailarchive.ietf.org/arch/msg/tls/3VUjMYzyzZvcggayoa-1A_bEHiI>
Subject: Re: [TLS] Consensus Call on draft-ietf-tls-dnssec-chain-extension
X-BeenThere: tls@ietf.org
X-Mailman-Version: 2.1.22
Precedence: list
List-Id: "This is the mailing list for the Transport Layer Security working group of the IETF." <tls.ietf.org>
List-Unsubscribe: <https://www.ietf.org/mailman/options/tls>, <mailto:tls-request@ietf.org?subject=unsubscribe>
List-Archive: <https://mailarchive.ietf.org/arch/browse/tls/>
List-Post: <mailto:tls@ietf.org>
List-Help: <mailto:tls-request@ietf.org?subject=help>
List-Subscribe: <https://www.ietf.org/mailman/listinfo/tls>, <mailto:tls-request@ietf.org?subject=subscribe>
X-List-Received-Date: Thu, 05 Apr 2018 02:34:33 -0000

On Wed, Apr 04, 2018 at 07:22:38PM -0700, Eric Rescorla wrote:
> I don't think that this comparison is particularly apt.The
> representation in HSTS is simply "I support HSTS". The representation
> in HPKP is "I will use either consistent keying material *or* a
> consistent set of CAs". The representation here is "I will continue to
> have DNSSEC-signed DANE records". That is a significantly more risky
> proposition than continuing to support TLS (and I'm ignoring the risk
> of hijacking attacks that people were concerned with with HPKP), and
> so this seems rather more like HPKP to me.

Without a TTL (with zero meaning "clear the pin to DANE") this extension
can only really be used with mandatory-to-use-with-DANE protocols, where
the commitment to "continue to have DNSSEC-signed DANE records" is
implied.

The TTL allows one to put a bound on that commitment, thus alleviating
the risk.

That's the whole point: to alleviate the risk of commitment to DANE in
order to not discourage opportunistic deployment.

Nico
--