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

Ben Schwartz <bemasc@google.com> Wed, 23 October 2019 16:14 UTC

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From: Ben Schwartz <bemasc@google.com>
Date: Wed, 23 Oct 2019 12:13:39 -0400
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To: Watson Ladd <watsonbladd@gmail.com>
Cc: Bill Frantz <frantz@pwpconsult.com>, TLS List <tls@ietf.org>
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Subject: Re: [TLS] draft-ietf-tls-esni feedback
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On the topic of radical suggestions, here's another one:
https://github.com/tlswg/draft-ietf-tls-esni/pull/186

In brief, this replaces the variable-length name with a fixed-length
hash, plus some accommodations to allow *.example.com,
*.*.example.com, etc.

My hope is that this design would work in the architecture described
by Watson, while saving ~220 bytes in each ClientHello.

One interesting feature of this design is that it doesn't require each
wildcard domain to publish any unique DNS record.  Instead, all
third-level wildcard customers can share a configuration, all
fourth-level wildcard customers can share a configuration, etc.  This
distinction is not visible in the TLS handshake, so the anonymity set
is not reduced.

On Wed, Oct 23, 2019 at 10:53 AM Watson Ladd <watsonbladd@gmail.com>; wrote:
>
> On Wed, Oct 23, 2019 at 7:35 AM Bill Frantz <frantz@pwpconsult.com>; wrote:
> >
> > A perhaps radical suggestion:
> >
> > Make the server name field fixed length e.g. 256 bytes. Longer
> > server names are not supported and clients MUST NOT send them.
> > (Both client and server can't use them because they won't fit in
> > the fixed length field.)
>
> The limit of server name in DNS is 260 bytes, so that limit already
> exists. No reason to shorten it elsewhere!
> --
> "Man is born free, but everywhere he is in chains".
> --Rousseau.
>
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