Re: [TLS] no fallbacks please [was: Downgrade protection, fallbacks, and server time]

Hubert Kario <hkario@redhat.com> Thu, 02 June 2016 10:43 UTC

Return-Path: <hkario@redhat.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 CA4A512D6A8 for <tls@ietfa.amsl.com>; Thu, 2 Jun 2016 03:43:51 -0700 (PDT)
X-Virus-Scanned: amavisd-new at amsl.com
X-Spam-Flag: NO
X-Spam-Score: -8.348
X-Spam-Level:
X-Spam-Status: No, score=-8.348 tagged_above=-999 required=5 tests=[BAYES_00=-1.9, RCVD_IN_DNSWL_HI=-5, RCVD_IN_MSPIKE_H3=-0.01, RCVD_IN_MSPIKE_WL=-0.01, RP_MATCHES_RCVD=-1.426, SPF_HELO_PASS=-0.001, SPF_PASS=-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 XxehJFDufM_h for <tls@ietfa.amsl.com>; Thu, 2 Jun 2016 03:43:50 -0700 (PDT)
Received: from mx1.redhat.com (mx1.redhat.com [209.132.183.28]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by ietfa.amsl.com (Postfix) with ESMTPS id 515E812D681 for <tls@ietf.org>; Thu, 2 Jun 2016 03:43:50 -0700 (PDT)
Received: from int-mx10.intmail.prod.int.phx2.redhat.com (int-mx10.intmail.prod.int.phx2.redhat.com [10.5.11.23]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mx1.redhat.com (Postfix) with ESMTPS id 162AD7F084; Thu, 2 Jun 2016 10:43:50 +0000 (UTC)
Received: from pintsize.usersys.redhat.com (dhcp-0-138.brq.redhat.com [10.34.0.138]) by int-mx10.intmail.prod.int.phx2.redhat.com (8.14.4/8.14.4) with ESMTP id u52AhmJH015925 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-SHA bits=256 verify=NO); Thu, 2 Jun 2016 06:43:49 -0400
From: Hubert Kario <hkario@redhat.com>
To: tls@ietf.org
Date: Thu, 02 Jun 2016 12:43:48 +0200
Message-ID: <3713097.ExV049UdFl@pintsize.usersys.redhat.com>
User-Agent: KMail/4.14.10 (Linux/4.4.10-200.fc22.x86_64; KDE/4.14.17; x86_64; ; )
In-Reply-To: <DBDC810F-B93F-4294-AB43-87B04DFE88D1@gmail.com>
References: <CAF8qwaDuGyHOu_4kpWN+c+vJKXyERPJu-2xR+nu=sPzG5vZ+ag@mail.gmail.com> <1464852691.5804.1.camel@redhat.com> <DBDC810F-B93F-4294-AB43-87B04DFE88D1@gmail.com>
MIME-Version: 1.0
Content-Type: multipart/signed; boundary="nextPart2732446.AWuzS6Lrkc"; micalg="pgp-sha512"; protocol="application/pgp-signature"
X-Scanned-By: MIMEDefang 2.68 on 10.5.11.23
X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.5.110.26]); Thu, 02 Jun 2016 10:43:50 +0000 (UTC)
Archived-At: <http://mailarchive.ietf.org/arch/msg/tls/YMM3o__g_T_o2jx5uLHeCH1sFQ0>
Subject: Re: [TLS] no fallbacks please [was: Downgrade protection, fallbacks, and server time]
X-BeenThere: tls@ietf.org
X-Mailman-Version: 2.1.17
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, 02 Jun 2016 10:43:52 -0000

On Thursday 02 June 2016 11:39:20 Yoav Nir wrote:
> > On 2 Jun 2016, at 10:31 AM, Nikos Mavrogiannopoulos
> > <nmav@redhat.com>; wrote:> 
> > On Wed, 2016-06-01 at 15:43 -0700, Eric Rescorla wrote:
> >> 2% is actually pretty good, but I agree that we're going to need
> >> fallback.
> > 
> > Please not. Lets let these fallbacks die. Not every client is a
> > browser. TLS 1.3 must be a protocol which doesn't require hacks to
> > operate. CBC was removed, lets do the same for insecure fallbacks.
> 
> Not every client is a browser, but some are. So what does the browser
> do when a server resets the connection after seeing the ClientHello?
> 
> Blank screen with a failure message?

fallback to check if the connection failure is caused by TLSv1.3, and if 
it is, display error message and put the blame squarely on the server

-- 
Regards,
Hubert Kario
Senior Quality Engineer, QE BaseOS Security team
Web: www.cz.redhat.com
Red Hat Czech s.r.o., Purky┼łova 99/71, 612 45, Brno, Czech Republic