Re: [TLS] Proposed text for removing renegotiation

Martin Thomson <martin.thomson@gmail.com> Wed, 28 May 2014 17:02 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 39B371A04A6 for <tls@ietfa.amsl.com>; Wed, 28 May 2014 10:02:10 -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 NXW6y-yonqwU for <tls@ietfa.amsl.com>; Wed, 28 May 2014 10:02:09 -0700 (PDT)
Received: from mail-wi0-x22d.google.com (mail-wi0-x22d.google.com [IPv6:2a00:1450:400c:c05::22d]) (using TLSv1 with cipher ECDHE-RSA-RC4-SHA (128/128 bits)) (No client certificate requested) by ietfa.amsl.com (Postfix) with ESMTPS id 61CFF1A6ED9 for <tls@ietf.org>; Wed, 28 May 2014 10:02:05 -0700 (PDT)
Received: by mail-wi0-f173.google.com with SMTP id bs8so4221687wib.12 for <tls@ietf.org>; Wed, 28 May 2014 10:02:00 -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=OC8XxAZdXxnTYHGcx9VUcp7VoDyx5QuUvCgBYM9BfCM=; b=SUu2E+nFZKeWe08C6LXJqOVjIykphRmpATp3uOFz1KJCOzLoJwZwSk+sQzXD/YEpSQ u+LE9wbPj7VrZ0MHqq+Yjl0p8NaXMomIiftKGhn6QZbRhVOfENuCnjzAAhfXbPw2V+4O tVUPw2mCQkREuRnY0TFIk91e2lorQO3X5fEbXiJJ7M0SdOMXsvZCRXGbNEMEVvEdJhzH aney+qhxOIvVM3FxZp4nr/9P2B9/RgxPpWNzFDoq5Ot0rH4RA7oLJ+u+tv6g1UNnse9q jwrMh8X3PfjcyBPnDNZ9khBvjcaGtasnCQtGhUDUylozFBoah0KdtX84LUgS2ecKXOFN 18Xw==
MIME-Version: 1.0
X-Received: by 10.180.96.6 with SMTP id do6mr2713573wib.44.1401296520800; Wed, 28 May 2014 10:02:00 -0700 (PDT)
Received: by 10.194.235.163 with HTTP; Wed, 28 May 2014 10:02:00 -0700 (PDT)
In-Reply-To: <20140528004408.D184F1AD1D@ld9781.wdf.sap.corp>
References: <CABkgnnXaLKmxXL01hQEdxHSNGt3nZQQNBLDD5H2LqBzTo3vK4g@mail.gmail.com> <20140528004408.D184F1AD1D@ld9781.wdf.sap.corp>
Date: Wed, 28 May 2014 10:02:00 -0700
Message-ID: <CABkgnnUrMpmUH7DBgoZUAofe4J6PqNfYn9ORcmwu4385VAUX5g@mail.gmail.com>
From: Martin Thomson <martin.thomson@gmail.com>
To: mrex@sap.com
Content-Type: text/plain; charset=UTF-8
Archived-At: http://mailarchive.ietf.org/arch/msg/tls/BbRfEWhZvoldfff5oDlYVtgzEeI
Cc: "tls@ietf.org" <tls@ietf.org>
Subject: Re: [TLS] Proposed text for removing renegotiation
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: Wed, 28 May 2014 17:02:10 -0000

On 27 May 2014 17:44, Martin Rex <mrex@sap.com> wrote:
> Conceptually, the TLS session cache is readonly after an entry
> is created, and that is GOOD, i.e. full TLS handshakes create new,
> distict session cache entries, and abbreviated TLS handshakes resume
> existing session cache entries and *NEVER* modify them.

That's a good point.  Something that I missed.  A resumption handshake
would have to include an epoch from the previous session.  That number
would need to be incremented with each update of the master secret.

Alternatively, and I think preferably, we could allow (or require)
servers to send the NewSessionTicket message when they update the
master secret, so that there isn't a master secret lying around
anywhere.

Of course, if you want to argue for unmodifiable state, then maybe you
can provide stronger justification than that.