Re: [TLS] Finished stuffing/PSK Binders

Ilari Liusvaara <ilariliusvaara@welho.com> Wed, 12 October 2016 14:28 UTC

Return-Path: <ilariliusvaara@welho.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 759FD1295D8 for <tls@ietfa.amsl.com>; Wed, 12 Oct 2016 07:28:22 -0700 (PDT)
X-Virus-Scanned: amavisd-new at amsl.com
X-Spam-Flag: NO
X-Spam-Score: -4.896
X-Spam-Level:
X-Spam-Status: No, score=-4.896 tagged_above=-999 required=5 tests=[BAYES_00=-1.9, RCVD_IN_DNSWL_NONE=-0.0001, RP_MATCHES_RCVD=-2.996] 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 HwQ9HFnHRbwg for <tls@ietfa.amsl.com>; Wed, 12 Oct 2016 07:28:20 -0700 (PDT)
Received: from welho-filter4.welho.com (welho-filter4.welho.com [83.102.41.26]) by ietfa.amsl.com (Postfix) with ESMTP id F1E111297A5 for <tls@ietf.org>; Wed, 12 Oct 2016 07:27:56 -0700 (PDT)
Received: from localhost (localhost [127.0.0.1]) by welho-filter4.welho.com (Postfix) with ESMTP id 7239516BA5; Wed, 12 Oct 2016 17:27:55 +0300 (EEST)
X-Virus-Scanned: Debian amavisd-new at pp.htv.fi
Received: from welho-smtp1.welho.com ([IPv6:::ffff:83.102.41.84]) by localhost (welho-filter4.welho.com [::ffff:83.102.41.26]) (amavisd-new, port 10024) with ESMTP id RakTp6PXeVdh; Wed, 12 Oct 2016 17:27:55 +0300 (EEST)
Received: from LK-Perkele-V2 (87-100-237-87.bb.dnainternet.fi [87.100.237.87]) (using TLSv1 with cipher ECDHE-RSA-AES256-SHA (256/256 bits)) (No client certificate requested) by welho-smtp1.welho.com (Postfix) with ESMTPSA id 1D8F8C4; Wed, 12 Oct 2016 17:27:55 +0300 (EEST)
Date: Wed, 12 Oct 2016 17:27:48 +0300
From: Ilari Liusvaara <ilariliusvaara@welho.com>
To: Martin Thomson <martin.thomson@gmail.com>
Message-ID: <20161012142748.GA17137@LK-Perkele-V2.elisa-laajakaista.fi>
References: <CABcZeBOJPz8DY92LE6531xbRYLU-Wvkqeb-vTX59gU5rYcp+Ww@mail.gmail.com> <20161009135817.GA13000@LK-Perkele-V2.elisa-laajakaista.fi> <CABcZeBNjVbFinq8oH5UrQRSa6FpGBiOXj8WB_X0PncZvz49zDA@mail.gmail.com> <CABcZeBNJokdTHJLkWWx22AtW+4qWRjZtzh5JuviVuJcwbcmnTA@mail.gmail.com> <CABkgnnWC18Q+wxERnEgKLF_tjjYAmJB__32ci-hbHPuGUq162A@mail.gmail.com> <CABcZeBMtYyL9+8=qD-rJo5tigx6qQZGorVS0fvGMmAttG5j=Zw@mail.gmail.com> <20161012085047.GD16436@LK-Perkele-V2.elisa-laajakaista.fi> <CABkgnnUBu2eUHNd5xkQxRxA=mckhUVaif4Mbi6kXNpMcgd8vcQ@mail.gmail.com>
MIME-Version: 1.0
Content-Type: text/plain; charset=utf-8
Content-Disposition: inline
In-Reply-To: <CABkgnnUBu2eUHNd5xkQxRxA=mckhUVaif4Mbi6kXNpMcgd8vcQ@mail.gmail.com>
User-Agent: Mutt/1.5.23 (2014-03-12)
Sender: ilariliusvaara@welho.com
Archived-At: <https://mailarchive.ietf.org/arch/msg/tls/g6pTmpvzdlKTkJ4aIL6YLOa_M-Q>
Cc: "tls@ietf.org" <tls@ietf.org>
Subject: Re: [TLS] Finished stuffing/PSK Binders
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: Wed, 12 Oct 2016 14:28:22 -0000

On Wed, Oct 12, 2016 at 09:43:05PM +1100, Martin Thomson wrote:
> On 12 October 2016 at 19:50, Ilari Liusvaara <ilariliusvaara@welho.com>; wrote:
> > I also noticed another edge case: What is to prevent server from
> > omitting key share group (emitting a cookie, so the restart is
> > not spurious), presumably causing the client to blank its key_share
> > and then proceed to accept DH versus client's previously sent share?
> 
> How about: If key_share isn't in the HRR, the client should replay
> it's old key_share verbatim.  Though I agree that the text should say
> as much.

Yeah, would work.

> Maybe we should require text for every extension that can appear in
> the HRR: what to do if the extension is in the HRR, and what to do if
> it isn't.

Or have every extension be "no change" if not present, and do the
specified thing to CH if prsent and known, abort if present and
unknown.

That would waste a bit of space with extensions signaling support
for some rewrites if the server doesn't use those but retries the
handshake.


-Ilari