Re: [TLS] draft-ietf-tls-esni feedback

Stephen Farrell <stephen.farrell@cs.tcd.ie> Tue, 22 October 2019 08:21 UTC

Return-Path: <stephen.farrell@cs.tcd.ie>
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 88D46120052 for <tls@ietfa.amsl.com>; Tue, 22 Oct 2019 01:21:17 -0700 (PDT)
X-Virus-Scanned: amavisd-new at amsl.com
X-Spam-Flag: NO
X-Spam-Score: -4.3
X-Spam-Level:
X-Spam-Status: No, score=-4.3 tagged_above=-999 required=5 tests=[BAYES_00=-1.9, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, RCVD_IN_DNSWL_MED=-2.3, SPF_HELO_NONE=0.001, SPF_PASS=-0.001] autolearn=ham autolearn_force=no
Authentication-Results: ietfa.amsl.com (amavisd-new); dkim=pass (1024-bit key) header.d=cs.tcd.ie
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 7cW9B_q2G_9q for <tls@ietfa.amsl.com>; Tue, 22 Oct 2019 01:21:15 -0700 (PDT)
Received: from mercury.scss.tcd.ie (mercury.scss.tcd.ie [134.226.56.6]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by ietfa.amsl.com (Postfix) with ESMTPS id 6554E120047 for <tls@ietf.org>; Tue, 22 Oct 2019 01:21:14 -0700 (PDT)
Received: from localhost (localhost [127.0.0.1]) by mercury.scss.tcd.ie (Postfix) with ESMTP id 1ADE9BE39; Tue, 22 Oct 2019 09:21:12 +0100 (IST)
X-Virus-Scanned: Debian amavisd-new at scss.tcd.ie
Received: from mercury.scss.tcd.ie ([127.0.0.1]) by localhost (mercury.scss.tcd.ie [127.0.0.1]) (amavisd-new, port 10024) with ESMTP id avbgC40AuO13; Tue, 22 Oct 2019 09:21:10 +0100 (IST)
Received: from [10.244.2.119] (95-45-153-252-dynamic.agg2.phb.bdt-fng.eircom.net [95.45.153.252]) by mercury.scss.tcd.ie (Postfix) with ESMTPSA id 5DF85BE2E; Tue, 22 Oct 2019 09:21:10 +0100 (IST)
DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=cs.tcd.ie; s=mail; t=1571732470; bh=vPx+z9byaz8i7BQJG3z3ch/yR9VdQjBsW/hyEevboCQ=; h=Subject:To:Cc:References:From:Date:In-Reply-To:From; b=Qx/SHTitoMybEaZ+gTH/EqsYlU4jyQ04MlRNiT5tw53x18xMD3qjNviUuX45pxT3R h1qT1Ej4fEjEY5BjQF+Ng945Gv+Q1z4nebyiOci5s/6+4DIqRkA6xakPn17OW23o5N RwSz2EQfYF8hsl1h9T8ylco5uuyJH/AzzBLK5R1o=
To: Ben Schwartz <bemasc@google.com>
Cc: Rob Sayre <sayrer@gmail.com>, "TLS@ietf.org" <tls@ietf.org>
References: <CAChr6Sw3f7du3JYxfcWSZje1zjDzsRBQyDjob-AvzjWeZzKW7g@mail.gmail.com> <CABcZeBPbw_KOo_ieSqkksYPeLtb9DufBz628oFPYc_Ue4S9iww@mail.gmail.com> <CAChr6SwB+7Jt2TLJSQh3q=Roizdt2=9jCBa9nq8KRxRo=86uZQ@mail.gmail.com> <CABcZeBNBtDK7q175tseEUiCVds=khj4xXYJZRf7GU9VGNDJ_Tg@mail.gmail.com> <CAChr6Sz6xHtFWjOKrLp3sp9MpC-SoU9Sx=vk22ditjShA7B=Kg@mail.gmail.com> <CABcZeBOnE+gyNu7GarAfO0bptoPfzQQ=VKeWLdpJBDM=E4yhzg@mail.gmail.com> <CAChr6SxWE66jPRbnBRtwNSn3L+uNFkoFBbYNOBAkKDN05qotoA@mail.gmail.com> <CABcZeBOy8ogJrmFajxX1pqjqgnE61gE=c3CWz+pp34NWHmGKbw@mail.gmail.com> <03e15760-dfce-cd7b-baea-56ac70d92192@cs.tcd.ie> <CAChr6SzmpSn3Q8tBi+Pdc+Bq7stiukbufbh-jDt+AEtrkV8XGg@mail.gmail.com> <f87c2916-d03d-2715-7b36-7b70fead8df4@cs.tcd.ie> <CAChr6SxfT0ed5J89siGX23A0G77BJQWxFRDoJ1w0v7=5O0KERw@mail.gmail.com> <8063bb12-8462-53fa-fa62-1e5abb1a652e@cs.tcd.ie> <CAHbrMsBPJqzaUSa42gGq45MfsTvCVW7t95q3feWEiSYeSN9ocw@mail.gmail.com>
From: Stephen Farrell <stephen.farrell@cs.tcd.ie>
Openpgp: id=5BB5A6EA5765D2C5863CAE275AB2FAF17B172BEA; url=
Autocrypt: addr=stephen.farrell@cs.tcd.ie; prefer-encrypt=mutual; keydata= mQINBFo9UDIBEADUH4ZPcUnX5WWRWO4kEkHea5Y5eEvZjSwe/YA+G0nrTuOU9nemCP5PMvmh 5Cg8gBTyWyN4Z2+O25p9Tja5zUb+vPMWYvOtokRrp46yhFZOmiS5b6kTq0IqYzsEv5HI58S+ QtaFq978CRa4xH9Gi9u4yzUmT03QNIGDXE37honcAM4MOEtEgvw4fVhVWJuyy3w//0F2tzKr EMjmL5VGuD/Q9+G/7abuXiYNNd9ZFjv4625AUWwy+pAh4EKzS1FE7BOZp9daMu9MUQmDqtZU bUv0Q+DnQAB/4tNncejJPz0p2z3MWCp5iSwHiQvytYgatMp34a50l6CWqa13n6vY8VcPlIqO Vz+7L+WiVfxLbeVqBwV+4uL9to9zLF9IyUvl94lCxpscR2kgRgpM6A5LylRDkR6E0oudFnJg b097ZaNyuY1ETghVB5Uir1GCYChs8NUNumTHXiOkuzk+Gs4DAHx/a78YxBolKHi+esLH8r2k 4LyM2lp5FmBKjG7cGcpBGmWavACYEa7rwAadg4uBx9SHMV5i33vDXQUZcmW0vslQ2Is02NMK 7uB7E7HlVE1IM1zNkVTYYGkKreU8DVQu8qNOtPVE/CdaCJ/pbXoYeHz2B1Nvbl9tlyWxn5Xi HzFPJleXc0ksb9SkJokAfwTSZzTxeQPER8la5lsEEPbU/cDTcwARAQABtDJTdGVwaGVuIEZh cnJlbGwgKDIwMTcpIDxzdGVwaGVuLmZhcnJlbGxAY3MudGNkLmllPokCQAQTAQgAKgIbAwUJ CZQmAAULCQgHAgYVCAkKCwIEFgIDAQIeAQIXgAUCWj6jdwIZAQAKCRBasvrxexcr6o7QD/9m x9DPJetmW794RXmNTrbTJ44zc/tJbcLdRBh0KBn9OW/EaAqjDmgNJeCMyJTKr1ywaps8HGUN hLEVkc14NUpgi4/Zkrbi3DmTp25OHj6wXBS5qVMyVynTMEIjOfeFFyxG+48od+Xn7qg6LT7G rHeNf+z/r0v9+8eZ1Ip63kshQDGhhpmRMKu4Ws9ZvTW2ACXkkTFaSGYJj3yIP4R6IgwBYGMz DXFX6nS4LA1s3pcPNxOgrvCyb60AiJZTLcOk/rRrpZtXB1XQc23ZZmrlTkl2HaThL6w3YKdi Ti1NbuMeOxZqtXcUshII45sANm4HuWNTiRh93Bn5bN6ddjgsaXEZBKUBuUaPBl7gQiQJcAlS 3MmGgVS4ZoX8+VaPGpXdQVFyBMRFlOKOC5XJESt7wY0RE2C8PFm+5eywSO/P1fkl9whkMgml 3OEuIQiP2ehRt/HVLMHkoM9CPQ7t6UwdrXrvX+vBZykav8x9U9M6KTgfsXytxUl6Vx5lPMLi 2/Jrsz6Mzh/IVZa3xjhq1OLFSI/tT2ji4FkJDQbO+yYUDhcuqfakDmtWLMxecZsY6O58A/95 8Qni6Xeq+Nh7zJ7wNcQOMoDGj+24di2TX1cKLzdDMWFaWzlNP5dB5VMwS9Wqj1Z6TzKjGjru q8soqohwb2CK9B3wzFg0Bs1iBI+2RuFnxLkCDQRaPVAyARAA+g3R0HzGr/Dl34Y07XqGqzq5 SU0nXIu9u8Ynsxj7gR5qb3HgUWYEWrHW2jHOByXnvkffucf5yzwrsvw8Q8iI8CFHiTYHPpey 4yPVn6R0w/FOMcY70eTIu/k6EEFDlDbs09DtKcrsT9bmN0XoRxITlXwWTufYqUnmS+YkAuk+ TLCtUin7OdaS2uU6Ata3PLQSeM2ZsUQMmYmHPwB9rmf+q2I005AJ9Q1SPQ2KNg/8xOGxo13S VuaSqYRQdpV93RuCOzg4vuXtR+gP0KQrus/P2ZCEPvU9cXF/2MIhXgOz207lv3iE2zGyNXld /n8spvWk+0bH5Zqd9Wcba/rGcBhmX9NKKDARZqjkv/zVEP1X97w1HsNYeUFNcg2lk9zQKb4v l1jx/Uz8ukzH2QNhU4R39dbF/4AwWuSVkGW6bTxHJqGs6YimbfdQqxTzmqFwz3JP0OtXX5q/ 6D4pHwcmJwEiDNzsBLl6skPSQ0Xyq3pua/qAP8MVm+YxCxJQITqZ8qjDLzoe7s9X6FLLC/DA L9kxl5saVSfDbuI3usH/emdtn0NA9/M7nfgih92zD92sl1yQXHT6BDa8xW1j+RU4P+E0wyd7 zgB2UeYgrp2IIcfG+xX2uFG5MJQ/nYfBoiALb0+dQHNHDtFnNGY3Oe8z1M9c5aDG3/s29QbJ +w7hEKKo9YMAEQEAAYkCJQQYAQgADwUCWj1QMgIbDAUJCZQmAAAKCRBasvrxexcr6qwvD/9b Rek3kfN8Q+jGrKl8qwY8HC5s4mhdDJZI/JP2FImf5J2+d5/e8UJ4fcsT79E0/FqX3Z9wZr6h sofPqLh1/YzDsYkZDHTYSGrlWGP/I5kXwUmFnBZHzM3WGrL3S7ZmCYMdudhykxXXjq7M6Do1 oxM8JofrXGtwBTLv5wfvvygJouVCVe87Ge7mCeY5vey1eUi4zSSF1zPpR6gg64w2g4TXM5qt SwkZVOv1g475LsGlYWRuJV8TA67yp1zJI7HkNqCo8KyHX0DPOh9c+Sd9ZX4aqKfqH9HIpnCL AYEgj7vofeix7gM3kQQmwynqq32bQGQBrKJEYp2vfeO30VsVx4dzuuiC5lyjUccVmw5D72J0 FlGrfEm0kw6D1qwyBg0SAMqamKN6XDdjhNAtXIaoA2UMZK/vZGGUKbqTgDdk0fnzOyb2zvXK CiPFKqIPAqKaDHg0JHdGI3KpQdRNLLzgx083EqEc6IAwWA6jSz+6lZDV6XDgF0lYqAYIkg3+ 6OUXUv6plMlwSHquiOc/MQXHfgUP5//Ra5JuiuyCj954FD+MBKIj8eWROfnzyEnBplVHGSDI ZLzL3pvV14dcsoajdeIH45i8DxnVm64BvEFHtLNlnliMrLOrk4shfmWyUqNlzilXN2BTFVFH 4MrnagFdcFnWYp1JPh96ZKjiqBwMv/H0kw==
Message-ID: <333fde42-76f9-1af3-0f0f-c70914b0222e@cs.tcd.ie>
Date: Tue, 22 Oct 2019 09:21:08 +0100
User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:60.0) Gecko/20100101 Thunderbird/60.9.0
MIME-Version: 1.0
In-Reply-To: <CAHbrMsBPJqzaUSa42gGq45MfsTvCVW7t95q3feWEiSYeSN9ocw@mail.gmail.com>
Content-Type: multipart/signed; micalg=pgp-sha512; protocol="application/pgp-signature"; boundary="uFSR4UigAmYphWxlso2atKcFVu4XF0CXg"
Archived-At: <https://mailarchive.ietf.org/arch/msg/tls/U-OciCt8_Aw4JVlqWF5yITBogXc>
Subject: Re: [TLS] draft-ietf-tls-esni feedback
X-BeenThere: tls@ietf.org
X-Mailman-Version: 2.1.29
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, 22 Oct 2019 08:21:18 -0000

Hiya,

On 22/10/2019 04:27, Ben Schwartz wrote:
> Note that the current text in the editors' draft says that when
> applying GREASE, "The padded_length value SHOULD be 260 or a multiple
> of 16 less than 260.".  We don't need GREASE to send 260 all the time,
> and the draft doesn't recommend it.

ISTM that GREASE needs to follow the kinds of lengths
used in practice to be most useful, so if 260 does get
widely used, then I guess that's what'd be most useful
to GREASE.

> Personally, I expect that 260 will be rare for real deployments,
> because most systems serve a fixed, known set of domains, and those
> that serve a large, dynamic set probably already impose a tighter
> length limit.

I don't know of any hoster or service with such a name
length limit. Do you have any example where a DNS name
that can be published and used as a TLS SNI would be
declined by a service provider?

> 
> One intriguing alternative would be to define some ESNI ciphersuites
> that encrypt a strong hash of the name.  Then a server with a large
> but finite name database can choose one of these ciphersuites,
> pre-compute hashes for names when entering them into the DB, and
> quickly invert incoming hashes with a DB lookup.  I wouldn't want to
> make this the only option because it can't support true wildcard
> servers, but I think it would cover most potential users while
> limiting the length to 32 octets or similar.

Yeah, that'd be nice but as you say doesn't work well
for wildcard certs, which I think is a showstopper. I
do think there are other algorithmic options we could
go with though, that would work.

Cheers,
S.