Re: [TLS] I-D Action: draft-ietf-tls-esni-07.txt

Christian Huitema <huitema@huitema.net> Tue, 02 June 2020 05:16 UTC

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From: Christian Huitema <huitema@huitema.net>
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Date: Mon, 01 Jun 2020 22:06:27 -0700
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Subject: Re: [TLS] I-D Action: draft-ietf-tls-esni-07.txt
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This draft looks really good. I just have two questions of clarification.

I am not sure that I understand the point made in appendix B, Total
Client Hello Encryption. The text in that appendix explains that "The
design described here only provides encryption for the SNI, but not for
other extensions, such as ALPN." This seems to contradict the design
description in the introduction, "The design in this document introduces
a new extension, called Encrypted Client Hello (ECH), which allows
clients to encrypt the entirety of their ClientHello to a supporting
server." Am I correct to assume that the text in appendix B is a
leftover from the previous version of the draft?

I am also not sure on how we could implement the "Optional Record
Digests and Trial Decryption" methods described in section 10.3. The
syntax description in section 5 specifies the record digest as "opaque
record_digest<0..2^16-1>", and defines that field as containing "A
cryptographic hash of the ECHConfig structure from which the ECH key was
obtained". Would it be correct to implement the "optional record digest"
method by just encoding a zero length field?

-- Christian Huitema

On 6/1/2020 12:41 PM, internet-drafts@ietf.org wrote:
> A New Internet-Draft is available from the on-line Internet-Drafts directories.
> This draft is a work item of the Transport Layer Security WG of the IETF.
>
>         Title           : TLS Encrypted Client Hello
>         Authors         : Eric Rescorla
>                           Kazuho Oku
>                           Nick Sullivan
>                           Christopher A. Wood
> 	Filename        : draft-ietf-tls-esni-07.txt
> 	Pages           : 31
> 	Date            : 2020-06-01
>
> Abstract:
>    This document describes a mechanism in Transport Layer Security (TLS)
>    for encrypting a ClientHello message under a server public key.
>
>
> The IETF datatracker status page for this draft is:
> https://datatracker.ietf.org/doc/draft-ietf-tls-esni/
>
> There are also htmlized versions available at:
> https://tools.ietf.org/html/draft-ietf-tls-esni-07
> https://datatracker.ietf.org/doc/html/draft-ietf-tls-esni-07
>
> A diff from the previous version is available at:
> https://www.ietf.org/rfcdiff?url2=draft-ietf-tls-esni-07
>
>
> Please note that it may take a couple of minutes from the time of submission
> until the htmlized version and diff are available at tools.ietf.org.
>
> Internet-Drafts are also available by anonymous FTP at:
> ftp://ftp.ietf.org/internet-drafts/
>
>
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