Re: [TLS] What would make TLS cryptographically better for TLS 1.3

Ralf Skyper Kaiser <skyper@thc.org> Sun, 03 November 2013 23:23 UTC

Return-Path: <skyper@thc.org>
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 E8C7E11E8105 for <tls@ietfa.amsl.com>; Sun, 3 Nov 2013 15:23:20 -0800 (PST)
X-Virus-Scanned: amavisd-new at amsl.com
X-Spam-Flag: NO
X-Spam-Score: -0.425
X-Spam-Level:
X-Spam-Status: No, score=-0.425 tagged_above=-999 required=5 tests=[BAYES_00=-2.599, FH_RELAY_NODNS=1.451, FM_FORGED_GMAIL=0.622, HTML_MESSAGE=0.001, RDNS_NONE=0.1]
Received: from mail.ietf.org ([12.22.58.30]) by localhost (ietfa.amsl.com [127.0.0.1]) (amavisd-new, port 10024) with ESMTP id 0NOArxrdOMZ9 for <tls@ietfa.amsl.com>; Sun, 3 Nov 2013 15:23:16 -0800 (PST)
Received: from mail-ie0-x22b.google.com (mail-ie0-x22b.google.com [IPv6:2607:f8b0:4001:c03::22b]) by ietfa.amsl.com (Postfix) with ESMTP id 49D4F11E824E for <tls@ietf.org>; Sun, 3 Nov 2013 15:23:11 -0800 (PST)
Received: by mail-ie0-f171.google.com with SMTP id tp5so10937377ieb.2 for <tls@ietf.org>; Sun, 03 Nov 2013 15:23:10 -0800 (PST)
DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=thc.org; s=google; h=mime-version:in-reply-to:references:date:message-id:subject:from:to :cc:content-type; bh=7XpyPNEqTY03svTYk34Y5wUjyzmaPdO8nb9SQYST1Qw=; b=EvL0/ss3Lh+tmpqC8zwzojwgU8C78PbLVybpH1PiaGGq+DDOH5IZc452m+UTq/uOSO Ijj90t0wHKpQkNQst1a0gZRz3pvA2lPfKGQn6IqMOl/v+e6NVCIx/Dn4jWpSrbpBjd3D 02Fc+RDVLcnFbZgP5gjxsKg7rQDHtHS7FUzhs=
X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20130820; h=x-gm-message-state:mime-version:in-reply-to:references:date :message-id:subject:from:to:cc:content-type; bh=7XpyPNEqTY03svTYk34Y5wUjyzmaPdO8nb9SQYST1Qw=; b=Nq0gKMq0rTkQvQM40XK+4OvTplYLA0JASRfN6YHzuszHumBRzOqDUMGoAKWow0wZl8 cr5l9wGvE0m/GZYYrtIWd8VrbXL9mlJP8+wA7cGbsEHZk8qnsP0htnxLqQr5nbemkiX/ zQdx2twL5X29wUc/r0QV3n8zHVVDUBDlkJaI9fvwocoAMyqxd6F8dQlBdpDJAS9dxzLG yDhWgakTHE32o+OMMevJr9oiwRRHEh/gmcndTruNhDyebLNEkSXOByDWiSCZQlu2ehYr w3YObm+AqIZLmgY5Rmg7NFn17nEjKXnxQdUN8R/E7gVh8bCt6/jLgPHjhTdKfkQMv2lP S8OQ==
X-Gm-Message-State: ALoCoQnDHyB9rNiB7eeKvFjT7PZNRIZWVdJE/hAHQoF819GQg3tBhuMGup7hMqoVCSFKyi5FzmdW
MIME-Version: 1.0
X-Received: by 10.50.128.137 with SMTP id no9mr9845622igb.36.1383520990815; Sun, 03 Nov 2013 15:23:10 -0800 (PST)
Received: by 10.64.231.100 with HTTP; Sun, 3 Nov 2013 15:23:10 -0800 (PST)
X-Originating-IP: [87.106.82.87]
In-Reply-To: <4A91BFED-6C57-47AC-8815-ACAC50E23491@checkpoint.com>
References: <CACsn0cnS7LWo+AN1maw-KYGhWXY1BLNPNOjiL-Y3UU3zG-Je_Q@mail.gmail.com> <20131031230955.GB32733@gmail.com> <5273FC73.8010303@gnutls.org> <CA+BZK2pZ=AFs5qw8dTbiV+s0KdSeFJH1-Z+UbaJZnQwHNgdXuA@mail.gmail.com> <4A91BFED-6C57-47AC-8815-ACAC50E23491@checkpoint.com>
Date: Sun, 3 Nov 2013 23:23:10 +0000
Message-ID: <CA+BZK2omT6pB05gM-dYvM__pJpqmMQBCVpLyFpVV7heLfnD18w@mail.gmail.com>
From: Ralf Skyper Kaiser <skyper@thc.org>
To: Yoav Nir <ynir@checkpoint.com>
Content-Type: multipart/alternative; boundary=047d7b10cf0d3291cb04ea4e1542
Cc: "tls@ietf.org" <tls@ietf.org>
Subject: Re: [TLS] What would make TLS cryptographically better for TLS 1.3
X-BeenThere: tls@ietf.org
X-Mailman-Version: 2.1.12
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: Sun, 03 Nov 2013 23:23:21 -0000

Hi Yoav,

i agree with the UI issue. That's the only use that I can see where
renegotiation is useful.

I would guess here that 99% of all TLS users (if not 99.99%) do not need
this feature.

The 99.99% of all users would have to carry the risk of complexity to
satisfy the need of the 0.01% of users.

There are hopefully other ways to satisfy the need of the 0.01% without the
99.99% of us having to take an extra risk (complexity). (Anyone? Ideas are
welcome...).

(ps when i'm speaking about complexity i do not mean the working hours it
would take to write the code [earlier replies by somebody indicated this]
but rather the security complexity [making mistakes and auditing a
process/procedures/... that is rarely used]).

regards,

ralf




On Sun, Nov 3, 2013 at 7:18 PM, Yoav Nir <ynir@checkpoint.com> wrote:

>
> On Nov 3, 2013, at 9:03 AM, Ralf Skyper Kaiser <skyper@thc.org> wrote:
>
> > Hi,
> >
> > avoid renegotiation. It serves no purpose and only adds complexity. It
> is so much more secure to kill and re-establish the TLS if the counters run
> out instead of renegotiating.
> >
>
> Hi, Ralf
>
> The one use of renegotiation that I'm aware of, is for overcoming a UI
> issue in browsers. If you do a TLS handshake with mutual authentication (so
> the server sends a CertReq), the browser pops up a dialog box with all the
> certificates you might have. Website designers with to avoid that,
> especially on the welcome screen, so the web server does not send a
> CertReq. Instead, they present a welcome screen with a button or link that
> says "Login with certificates" Clicking that performs a regular SSL
> handshake (or does nothing at all if the connection is already
> established), but when the request comes in ("GET /login_with_certs
> HTTP/1.1"), the web server sends a HELLO_REQUEST, and in the resulting
> handshake it sends the CertReq, so the pop-up appears when the user *is*
> expecting it.
>
> I totally agree that renegotiation for rekeying is useless for people who
> are not doing DES-CBC and 3DES-CBC. It's even superfluous for them in most
> cases (you're pretty save doing 500,000,000 blocks, and that's 4 GB in
> 3DES. How many sites do you browse with 4 GB?  Maybe downloading stuff…)
>
> But before we can drop renegotiation from the standards, or recommend that
> implementors don't implement it, we need an alternate mechanism to upgrade
> from server-authenticated to mutually-authenticated within the same
> session. That is a real market need. How about allowing a CertReq sent from
> the server to the client in the middle of a connection, followed by the
> client sending a Certificate and Certificate Verify. For simplicity, we
> could always do that after the Finished, so that it's always
> Server-authenticated session when the Finished is sent.
>
> Yoav
>
>