Re: [TLS] drop obsolete SSL 2 backwards compatibility from TLS 1.3 draft

Yuhong Bao <yuhongbao_386@hotmail.com> Thu, 12 February 2015 23:48 UTC

Return-Path: <yuhongbao_386@hotmail.com>
X-Original-To: tls@ietfa.amsl.com
Delivered-To: tls@ietfa.amsl.com
Received: from localhost (ietfa.amsl.com [127.0.0.1]) by ietfa.amsl.com (Postfix) with ESMTP id A137D1A01D5 for <tls@ietfa.amsl.com>; Thu, 12 Feb 2015 15:48:25 -0800 (PST)
X-Virus-Scanned: amavisd-new at amsl.com
X-Spam-Flag: NO
X-Spam-Score: 1.04
X-Spam-Level: *
X-Spam-Status: No, score=1.04 tagged_above=-999 required=5 tests=[BAYES_50=0.8, FREEMAIL_ENVFROM_END_DIGIT=0.25, FREEMAIL_FROM=0.001, RCVD_IN_DNSWL_NONE=-0.0001, SPF_PASS=-0.001, T_RP_MATCHES_RCVD=-0.01] 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 enA2qwcaIJ9G for <tls@ietfa.amsl.com>; Thu, 12 Feb 2015 15:48:24 -0800 (PST)
Received: from BLU004-OMC2S34.hotmail.com (blu004-omc2s34.hotmail.com [65.55.111.109]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-SHA384 (256/256 bits)) (No client certificate requested) by ietfa.amsl.com (Postfix) with ESMTPS id E627B1A0127 for <tls@ietf.org>; Thu, 12 Feb 2015 15:48:23 -0800 (PST)
Received: from BLU177-W21 ([65.55.111.73]) by BLU004-OMC2S34.hotmail.com over TLS secured channel with Microsoft SMTPSVC(7.5.7601.22751); Thu, 12 Feb 2015 15:48:23 -0800
X-TMN: [4z+NQAdFX+FrT5ES4Pp2O7R42mbmQMW3]
X-Originating-Email: [yuhongbao_386@hotmail.com]
Message-ID: <BLU177-W21BE1BB9BC3F129D6421CEC3220@phx.gbl>
From: Yuhong Bao <yuhongbao_386@hotmail.com>
To: Florian Weimer <fweimer@redhat.com>, "tls@ietf.org" <tls@ietf.org>
Date: Thu, 12 Feb 2015 15:48:22 -0800
Importance: Normal
In-Reply-To: <54DB5555.6070207@redhat.com>
References: <201412221945.35644.davemgarrett@gmail.com>, , <F07340BA-F182-470C-AF90-C85A973075B9@gmail.com>, <BLU177-W5178CCC10BAEA4CE3A78FBC3540@phx.gbl>, <54DB5555.6070207@redhat.com>
Content-Type: text/plain; charset="Windows-1252"
Content-Transfer-Encoding: quoted-printable
MIME-Version: 1.0
X-OriginalArrivalTime: 12 Feb 2015 23:48:23.0179 (UTC) FILETIME=[63264DB0:01D0471E]
Archived-At: <http://mailarchive.ietf.org/arch/msg/tls/ykEFDT2huffYFeRIYOAIKJ1WNlo>
Subject: Re: [TLS] drop obsolete SSL 2 backwards compatibility from TLS 1.3 draft
X-BeenThere: tls@ietf.org
X-Mailman-Version: 2.1.15
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: <http://www.ietf.org/mail-archive/web/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, 12 Feb 2015 23:48:26 -0000

> On 12/24/2014 08:02 AM, Yuhong Bao wrote:
>>>>
>>>> There's no reason to maintain any backwards support here just for Internet
>>>> Explorer 2.0 on Windows 3.1.
>>>>
>>>
>>> I’m not objecting to the change, but I am objecting to the hyperbole. The issue is with Internet Explorer 6 on Windows XP, which still exists, but more importantly, a lot of web service clients running on top of Windows XP use the same SCHANNEL library as IE would use, so they issue a SSLv2 ClientHello. Despite Microsoft’s best efforts, there is still a substantial but diminishing install base of XP.
>>>
>>> It’s fine for us to break compatibility with these clients, but let’s not pretend it’s some ancient technology that doesn’t exist in the market anymore.
>>>
>> If needed, one suggestion would be to cap the old SSLv2 ClientHello to TLS 1.2.
>
> At least make it TLS 1.1 instead. With TLS 1.2, the SSLv2 ClientHello
> cannot include the signature algorithms extension, so SHA-1 is used
> instead of the concatenation of MD5 and SHA-1, and this usually not what
> is wanted.

Just confirmed that IE on Win7 even when misconfigured to enable SSLv2 doesn't send a SSLv2 ClientHello with TLS 1.2 on it which means that SChannel probably can't do it at all. Andrei Popov should be able to confirm this.