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

On Mon, Jun 1, 2020, at 10:06 PM, Christian Huitema wrote:
> 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?

Yep! I'd opt to remove this text entirely, but if others want to keep it I suppose we can update the text accordingly. 

> 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?

Indeed, that was the intent. Would you prefer a different way?

Best,
Chris

> 
> -- 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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