Re: [TLS] Negotiating with known_configuration

Martin Thomson <martin.thomson@gmail.com> Tue, 21 July 2015 11:30 UTC

Return-Path: <martin.thomson@gmail.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 6AF891A0100 for <tls@ietfa.amsl.com>; Tue, 21 Jul 2015 04:30:15 -0700 (PDT)
X-Virus-Scanned: amavisd-new at amsl.com
X-Spam-Flag: NO
X-Spam-Score: -2
X-Spam-Level:
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, FREEMAIL_FROM=0.001, SPF_PASS=-0.001] autolearn=ham
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 RU2CKhC5ssZ2 for <tls@ietfa.amsl.com>; Tue, 21 Jul 2015 04:30:13 -0700 (PDT)
Received: from mail-yk0-x231.google.com (mail-yk0-x231.google.com [IPv6:2607:f8b0:4002:c07::231]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by ietfa.amsl.com (Postfix) with ESMTPS id 8AE0B1A00B7 for <tls@ietf.org>; Tue, 21 Jul 2015 04:30:13 -0700 (PDT)
Received: by ykfw194 with SMTP id w194so82418134ykf.0 for <tls@ietf.org>; Tue, 21 Jul 2015 04:30:13 -0700 (PDT)
DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20120113; h=mime-version:in-reply-to:references:date:message-id:subject:from:to :cc:content-type; bh=zonGHEeUB1kC2Gmx42w59JP3qmsezDEeiwYp+tSlBPQ=; b=QMw5MhWOwyvr4kt7FODAALFY/apRoyGYNEFi85xCzfu2+xJJ5o4DbOEbd4ZGmt2ypy S9GHCTA3D6t32wz8PyfgDAZ9nNhQ1CiP4A5N4dan2KpmjplJxTZm1l0FZYbm5OgMV4vG mAkvi0y1plMe+scap5UeqT2yaPkaFaWOxqulJabEcNzLcb94QtjTZYS3L6sHL/1gQnG+ ZHELbE0IkF9cKhKjEKKPUyPfAZuIwz6F/IRJDLYVObojRfdRekMm95DQydcAOX8As/Qc wTS9USOB/TiY1uMspwTiVBwBRO/794lY8nH53rna8NNr8+D/7vcpCCHkOOuQiEtfQlME e9xQ==
MIME-Version: 1.0
X-Received: by 10.129.36.14 with SMTP id k14mr32305213ywk.64.1437478212952; Tue, 21 Jul 2015 04:30:12 -0700 (PDT)
Received: by 10.129.110.138 with HTTP; Tue, 21 Jul 2015 04:30:12 -0700 (PDT)
In-Reply-To: <CABcZeBP-2GudRXCHWBnWV7fnTuv-4nAzyxxY_FJx7UsPF_6KFg@mail.gmail.com>
References: <CABcZeBOEUuVKHYRs5+DY6h8vcQ9uLWW9SXzN=VH=ovHbnEK0AA@mail.gmail.com> <CABkgnnUn5_Wo9XDRe=KQKO64MWcBGw0Pk6aviyigR+H7yVBaUg@mail.gmail.com> <CABcZeBP-2GudRXCHWBnWV7fnTuv-4nAzyxxY_FJx7UsPF_6KFg@mail.gmail.com>
Date: Tue, 21 Jul 2015 04:30:12 -0700
Message-ID: <CABkgnnVswNWk-ZOD32EvfJ=ORQWTXBPAKs51k9tRq3vspzi3jQ@mail.gmail.com>
From: Martin Thomson <martin.thomson@gmail.com>
To: Eric Rescorla <ekr@rtfm.com>
Content-Type: text/plain; charset="UTF-8"
Archived-At: <http://mailarchive.ietf.org/arch/msg/tls/2TS-MoNB0klEvLe-XTEbxk8axjE>
Cc: "tls@ietf.org" <tls@ietf.org>
Subject: Re: [TLS] Negotiating with known_configuration
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: <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: Tue, 21 Jul 2015 11:30:15 -0000

On 21 July 2015 at 04:12, Eric Rescorla <ekr@rtfm.com> wrote:
>
> Yes, that's an issue. Not entirely sure what to do about other than
> have the server provide its negotiation preferences out of band
> in that case.

I think that we could handle that at the point we define an
out-of-band configuration priming mechanism.  I don't think we need a
full negotiation model for the server.  A simple option would list the
server's preference order for suites and so forth in its configuration
advertisement; the client would then pick from that.