[TLS] DPRIV has the downgrade too (Re: Consensus Call on draft-ietf-tls-dnssec-chain-extension)

Nico Williams <nico@cryptonector.com> Fri, 06 April 2018 19:26 UTC

Return-Path: <nico@cryptonector.com>
X-Original-To: tls@ietfa.amsl.com
Delivered-To: tls@ietfa.amsl.com
Received: from localhost (localhost []) by ietfa.amsl.com (Postfix) with ESMTP id F250B126BF6 for <tls@ietfa.amsl.com>; Fri, 6 Apr 2018 12:26:28 -0700 (PDT)
X-Virus-Scanned: amavisd-new at amsl.com
X-Spam-Flag: NO
X-Spam-Score: -2
X-Spam-Status: No, score=-2 tagged_above=-999 required=5 tests=[BAYES_00=-1.9, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, RCVD_IN_DNSWL_NONE=-0.0001] autolearn=ham autolearn_force=no
Authentication-Results: ietfa.amsl.com (amavisd-new); dkim=pass (1024-bit key) header.d=cryptonector.com
Received: from mail.ietf.org ([]) by localhost (ietfa.amsl.com []) (amavisd-new, port 10024) with ESMTP id egOMOnbSMQYJ for <tls@ietfa.amsl.com>; Fri, 6 Apr 2018 12:26:27 -0700 (PDT)
Received: from homiemail-a26.g.dreamhost.com (sub4.mail.dreamhost.com []) (using TLSv1.1 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by ietfa.amsl.com (Postfix) with ESMTPS id 97552124D68 for <tls@ietf.org>; Fri, 6 Apr 2018 12:26:27 -0700 (PDT)
Received: from homiemail-a26.g.dreamhost.com (localhost []) by homiemail-a26.g.dreamhost.com (Postfix) with ESMTP id D4878A00C541; Fri, 6 Apr 2018 12:26:26 -0700 (PDT)
DKIM-Signature: v=1; a=rsa-sha1; c=relaxed; d=cryptonector.com; h=date :from:to:subject:message-id:references:mime-version:content-type :in-reply-to; s=cryptonector.com; bh=A8WPjD7Oj6scpQ6qUKxf8iU8Isk =; b=wcVjySKkoDTsHVKDsNiYgvzn5MiRFyauahAkH0w/IlUAGYR/G+kh4ZR4aM2 QLXyh7FQX3wLsKzm9u3RjtE1eGutReVdyUYHHHek0oXvn6v5DRqx0qWsUrNQ+0LQ MQeMcsvjycftFBAh3p6dZ3BJ3vWNskY5kZG+5fIMFSCzOGNs=
Received: from localhost (cpe-70-123-158-140.austin.res.rr.com []) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) (Authenticated sender: nico@cryptonector.com) by homiemail-a26.g.dreamhost.com (Postfix) with ESMTPSA id 8D3ECA00C540; Fri, 6 Apr 2018 12:26:26 -0700 (PDT)
Date: Fri, 06 Apr 2018 14:21:02 -0500
From: Nico Williams <nico@cryptonector.com>
To: TLS WG <tls@ietf.org>
Message-ID: <20180406192101.GQ25259@localhost>
References: <CAOgPGoAhzEtxpW5mzmkf2kv3AcugNy0dAzhvpaqrTSuMSqWqfw@mail.gmail.com> <D04D5EAA-8A05-4D4E-97F8-36CE2DD9F3EE@dukhovni.org>
MIME-Version: 1.0
Content-Type: text/plain; charset="us-ascii"
Content-Disposition: inline
In-Reply-To: <D04D5EAA-8A05-4D4E-97F8-36CE2DD9F3EE@dukhovni.org>
User-Agent: Mutt/1.5.24 (2015-08-30)
Archived-At: <https://mailarchive.ietf.org/arch/msg/tls/d26dfw88l7ZytkejKgW7s8hiT1o>
Subject: [TLS] DPRIV has the downgrade too (Re: 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: Fri, 06 Apr 2018 19:26:29 -0000

On Thu, Apr 05, 2018 at 02:46:12AM -0400, Viktor Dukhovni wrote:
> So I rather suspect that even the DPRIV use-case, which supposedly does not need
> the proposed changes, actually does need them for meaningful security from using
> DANE, and we've not just not looked at the details closely enough yet.  It may
> well turn out not substantially different from the browser use-case that is not
> adequately met by the current draft.
> Can someone explain briefly how DPRIV avoids the same downgrade issues, and
> negative adoption incentives (cost-benfit comparison)?  If it turns out that
> no adequate explanation is possible, and indeed the same issues are present,
> then the proposed changes (which are still needed elsewhere) are all the
> more pressing.

Oh, right, DPRIV isn't a work-in-progress.  It's already here.  Thus it
cannot be an application that makes draft-ietf-tls-dnssec-chain-extension
mandatory.  Therefore it's subject to the downgrade attack we want to
address with (C).

I think now the WG should really want this LC to succeed and get this
change made.