Re: [TLS] draft-ietf-tls-curve25519-01: Is public key validation necessary or helpful?

Jeffrey Walton <noloader@gmail.com> Thu, 31 December 2015 06:51 UTC

Return-Path: <noloader@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 41BA71A86FB for <tls@ietfa.amsl.com>; Wed, 30 Dec 2015 22:51:04 -0800 (PST)
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 x9gOcwEcmGQf for <tls@ietfa.amsl.com>; Wed, 30 Dec 2015 22:51:03 -0800 (PST)
Received: from mail-ig0-x22f.google.com (mail-ig0-x22f.google.com [IPv6:2607:f8b0:4001:c05::22f]) (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 D466E1A86FA for <tls@ietf.org>; Wed, 30 Dec 2015 22:51:02 -0800 (PST)
Received: by mail-ig0-x22f.google.com with SMTP id mv3so156552699igc.0 for <tls@ietf.org>; Wed, 30 Dec 2015 22:51:02 -0800 (PST)
DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20120113; h=mime-version:reply-to:in-reply-to:references:date:message-id :subject:from:to:cc:content-type:content-transfer-encoding; bh=CH8srKuTjF2SxO/wAB30v2m+8U9oDb89BmbM2BOv/y4=; b=h6hKe+4vJWOhRjC6JiInVMRlhYqgSioSIjk+JdZ/E5yh749vL9U7FbXARaeJ7o0v7y 9QUr5znwsexAtzDw3knx5cCfdPv1baGIOvkD+EI9/hU7yeCQK18+rIlwYmoTVCz/HVBv no+bHWX0nBSjOuoprs/Xsr8p2Jurogd3TMSmHnWJaIlhXb6TVqNn7fnKoKtyXJCm9Vno Lpr9lZWhFfYqEufoO9PPofR7ZnxhTWrM4DOJCMwgbQOf7R80Gb/UCVYXhJVbU9nEajV9 Upqu+smKPFuPnmwW0cykGpTd3DKJ2eCQC+Q9IR6Gz0pnavXf3+5Teuys1Ekps4ITtqcE ceEQ==
MIME-Version: 1.0
X-Received: by 10.50.30.134 with SMTP id s6mr61730162igh.36.1451544662226; Wed, 30 Dec 2015 22:51:02 -0800 (PST)
Received: by 10.36.31.66 with HTTP; Wed, 30 Dec 2015 22:51:02 -0800 (PST)
In-Reply-To: <5684C9CC.2080703@akr.io>
References: <CAFewVt4Midtq7X6px4=A4hGkspQuJdzZQ907U=SJox0SdgfAJg@mail.gmail.com> <CACsn0cng1o-5hm=zuL6puOGJ8A2bjB=fFsaFsBCmmVofNSuumg@mail.gmail.com> <CABkgnnXQS3Ek6jDjx0aSQmaf+=EjfGWa8MG1AO4QwhJbK50VQg@mail.gmail.com> <CAFewVt4NSGDP_At8XsX4OsxSUaj_2kRyFP_keDQhfnR0=mBhrg@mail.gmail.com> <CABkgnnUq0_28U6VqE=ZPpwutOBUkTGwhxqHQOEvQve5JYfSVRA@mail.gmail.com> <CAFewVt6fyqbOZfQkWY=9SM20WcrP0UhfH+3wvXjiYoTjPm2pgA@mail.gmail.com> <CAFewVt5U9awAg4FbdWtXiCATd-kWttdsAwe3eWwcD5SXsKvyWQ@mail.gmail.com> <6F6EDAA8-15F2-4949-B927-4D0BD0E8FFE3@inria.fr> <20151230105207.GB6140@roeckx.be> <CAFewVt4+eysHvxnP=q-Gn-0DgQWLkoTs5OSc8v_t6qRtsk7TWg@mail.gmail.com> <CAMfhd9VYAaioMJqsk1M=sEQ-tJ_GJpDk5LsYcydK0Dwv-jQG1g@mail.gmail.com> <5684C9CC.2080703@akr.io>
Date: Thu, 31 Dec 2015 01:51:02 -0500
Message-ID: <CAH8yC8=cA1O4o_OQZvu=w8RU7ACKC2gp4tKLaw7ZmJk=Ei7zWg@mail.gmail.com>
From: Jeffrey Walton <noloader@gmail.com>
To: Alyssa Rowan <akr@akr.io>
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: quoted-printable
Archived-At: <http://mailarchive.ietf.org/arch/msg/tls/P2MHe9wCIYihGApGDiRoT9Di2tw>
Cc: "tls@ietf.org" <tls@ietf.org>
Subject: Re: [TLS] draft-ietf-tls-curve25519-01: Is public key validation necessary or helpful?
X-BeenThere: tls@ietf.org
X-Mailman-Version: 2.1.15
Precedence: list
Reply-To: noloader@gmail.com
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: Thu, 31 Dec 2015 06:51:04 -0000

On Thu, Dec 31, 2015 at 1:23 AM, Alyssa Rowan <akr@akr.io> wrote:
> -----BEGIN PGP SIGNED MESSAGE-----
> Hash: SHA512
>
> On 2015-12-31 03:30, Adam Langley wrote:
>
>> I don't mind if the integration of curve25519 in TLS requires a
>> zero-check or not, but what property are people hoping to gain? If
>> one wants to avoid triple-handshake like issues then session-hash
>> is the answer.
>
> (I have a terrible cold, so apologies if I am less than coherent!)
>
> I think I prefer this, of the available options. Specify that:
>
> • Both client and server MUST abort if X25519 and/or X448 are
>   offered/chosen but session_hash is not;
> • Explain why in Security Considerations;
> • Test as part of interop/unit tests?

I think the above sets up a situation where the safer curves are tied
to 0-RTT and friends. I'm pretty sure any configuration under my
purview will *not* have 0-RTT enabled. My servers will *not* be
consuming data before it has been authenticated.

I can only say I'm "pretty sure". I won't know for certain until I
actually step the code under a debugger and see what is being consumed
in the negative cases.

My apologies if I am parsing it incorrectly or going against the grain.

Jeff