IETF Logo Mail Archive

Re: [TLS] Last Call: <draft-ietf-tls-downgrade-scsv-03.txt> (TLS Fallback Signaling Cipher Suite Value (SCSV) for Preventing Protocol Downgrade Attacks) to Proposed Standard

Hanno Böck <hanno@hboeck.de> Fri, 16 January 2015 20:03 UTC

Return-Path: <hanno@hboeck.de>
X-Original-To: ietf@ietfa.amsl.com
Delivered-To: ietf@ietfa.amsl.com
Received: from localhost (ietfa.amsl.com [127.0.0.1]) by ietfa.amsl.com (Postfix) with ESMTP id 3D34C1ACEA5; Fri, 16 Jan 2015 12:03:33 -0800 (PST)
X-Virus-Scanned: amavisd-new at amsl.com
X-Spam-Flag: NO
X-Spam-Score: 1.399
X-Spam-Level: *
X-Spam-Status: No, score=1.399 tagged_above=-999 required=5 tests=[BAYES_05=-0.5, MANGLED_BACK=2.3, MIME_8BIT_HEADER=0.3, RCVD_IN_DNSWL_LOW=-0.7, SPF_PASS=-0.001] autolearn=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 UtsfW0UsZ31S; Fri, 16 Jan 2015 12:03:31 -0800 (PST)
Received: from zucker2.schokokeks.org (zucker2.schokokeks.org [178.63.68.90]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-SHA (256/256 bits)) (No client certificate requested) by ietfa.amsl.com (Postfix) with ESMTPS id 2D3191B2B06; Fri, 16 Jan 2015 12:03:31 -0800 (PST)
Received: from pc (ip5b40005c.dynamic.kabel-deutschland.de [::ffff:91.64.0.92]) (AUTH: LOGIN hanno-default@schokokeks.org, TLS: TLSv1/SSLv3, 128bits, ECDHE-RSA-AES128-GCM-SHA256) by zucker.schokokeks.org with ESMTPSA; Fri, 16 Jan 2015 21:03:28 +0100 id 0000000000000034.0000000054B96E90.0000684E
Date: Fri, 16 Jan 2015 21:03:27 +0100
From: Hanno Böck <hanno@hboeck.de>
To: tls@ietf.org
Subject: Re: [TLS] Last Call: <draft-ietf-tls-downgrade-scsv-03.txt> (TLS Fallback Signaling Cipher Suite Value (SCSV) for Preventing Protocol Downgrade Attacks) to Proposed Standard
Message-ID: <20150116210327.61046788@pc>
In-Reply-To: <20150109180539.22231.7270.idtracker@ietfa.amsl.com>
References: <20150109180539.22231.7270.idtracker@ietfa.amsl.com>
X-Mailer: Claws Mail 3.11.1 (GTK+ 2.24.25; x86_64-pc-linux-gnu)
Mime-Version: 1.0
Content-Type: multipart/signed; micalg="pgp-sha512"; protocol="application/pgp-signature"; boundary="=_zucker.schokokeks.org-26702-1421438608-0001-2"
Archived-At: <http://mailarchive.ietf.org/arch/msg/ietf/Y6cNuBNcV09ncYey7I2wJ4btZAY>
X-Mailman-Approved-At: Tue, 20 Jan 2015 07:58:50 -0800
Cc: ietf@ietf.org
X-BeenThere: ietf@ietf.org
X-Mailman-Version: 2.1.15
Precedence: list
List-Id: IETF-Discussion <ietf.ietf.org>
List-Unsubscribe: <https://www.ietf.org/mailman/options/ietf>, <mailto:ietf-request@ietf.org?subject=unsubscribe>
List-Archive: <http://www.ietf.org/mail-archive/web/ietf/>
List-Post: <mailto:ietf@ietf.org>
List-Help: <mailto:ietf-request@ietf.org?subject=help>
List-Subscribe: <https://www.ietf.org/mailman/listinfo/ietf>, <mailto:ietf-request@ietf.org?subject=subscribe>
X-List-Received-Date: Fri, 16 Jan 2015 20:03:33 -0000

Recently Mozilla has disabled the now so-called protocol dance, which
makes adding another workaround (SCSV) pretty much obsolete:
https://bugzilla.mozilla.org/show_bug.cgi?id=1084025#c7

And a few days ago mozilla dev Brian Smith tweetet this:
"Fx experiment to disable non-secure TLS version fallback is going even
better than expected. Starting to feel silly for delaying it so long."
https://twitter.com/BRIAN_____/status/555138042428526593

I think this adds further evidence that adding another workaround layer
(SCSV) is the wrong thing to do. Instead browsers should just stop
doing weird things with protocols that compromise security and drop
the protocol dance completely.

(By the way: Has anyone thought what happens when people implement TLS
hardware that is version intolerant to versions > 1.2 and at the same
time send SCSV in the handshake? I'm pretty sure that at some point
some hardware will appear that does exactly that. Will we need another
SCSV standard for every TLS version then?)

-- 
Hanno Böck
http://hboeck.de/

mail/jabber: hanno@hboeck.de
GPG: BBB51E42

v2.23.0 | Report a Bug | By Email