Re: [TLS] New Draft: Using DNS to set the SNI explicitly

mrex@sap.com (Martin Rex) Thu, 09 March 2017 10:52 UTC

In-Reply-To: <CAHbrMsCpCH2qSG=cZjMMuWbpzCn8dQhvaTDaRc1riwnYiKGjsg@mail.gmail.com>
To: Ben Schwartz <bemasc@google.com>
Date: Thu, 09 Mar 2017 11:52:07 +0100
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From: mrex@sap.com
Archived-At: <https://mailarchive.ietf.org/arch/msg/tls/BoJAL7R-tdVWcgYZTRPO13ibres>
Cc: tls@ietf.org
Subject: Re: [TLS] New Draft: Using DNS to set the SNI explicitly
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Reply-To: mrex@sap.com

Ben Schwartz wrote:
> 
> Like a lot of people here, I'm very interested in ways to reduce the
> leakage of users' destinations in the ClientHello's cleartext SNI.  It
> seems like the past and current proposals to fix the leak are pretty
> difficult, involving a lot of careful cryptography and changes to clients
> and servers.

It is formally provable that there is no solution to the problem
that you're describing.

While you can come up with all kinds of fancy and complicated schemes
that are sufficient to provide you the illusion that you're looking for,
the best you can come up with, will *be* an illusion.  But some of
those illusions will cause lots of pain for implementors and make
the whole thing fragile and cause interop problems.

The situation is pretty similar for the hiding of the ContentType
in TLSv1.3 records.  It is formally provable that this can not provide
value, but it make implementations harder and reliably break some
existing stuff.

-Martin

[TLS] New Draft: Using DNS to set the SNI explici… Ben Schwartz
Re: [TLS] New Draft: Using DNS to set the SNI exp… Ilari Liusvaara
Re: [TLS] New Draft: Using DNS to set the SNI exp… Salz, Rich
Re: [TLS] New Draft: Using DNS to set the SNI exp… Ben Schwartz
Re: [TLS] New Draft: Using DNS to set the SNI exp… Ben Schwartz
Re: [TLS] New Draft: Using DNS to set the SNI exp… Christian Huitema
Re: [TLS] New Draft: Using DNS to set the SNI exp… Salz, Rich
Re: [TLS] New Draft: Using DNS to set the SNI exp… Ben Schwartz
Re: [TLS] New Draft: Using DNS to set the SNI exp… Yoav Nir
Re: [TLS] New Draft: Using DNS to set the SNI exp… Richard Barnes
Re: [TLS] New Draft: Using DNS to set the SNI exp… Ben Schwartz
Re: [TLS] New Draft: Using DNS to set the SNI exp… Ben Schwartz
Re: [TLS] New Draft: Using DNS to set the SNI exp… Ben Schwartz
Re: [TLS] New Draft: Using DNS to set the SNI exp… Martin Rex
Re: [TLS] New Draft: Using DNS to set the SNI exp… Ben Schwartz
Re: [TLS] New Draft: Using DNS to set the SNI exp… Martin Rex
Re: [TLS] New Draft: Using DNS to set the SNI exp… Ilari Liusvaara
Re: [TLS] New Draft: Using DNS to set the SNI exp… Martin Rex
Re: [TLS] New Draft: Using DNS to set the SNI exp… Ryan Sleevi
Re: [TLS] New Draft: Using DNS to set the SNI exp… Ilari Liusvaara
Re: [TLS] New Draft: Using DNS to set the SNI exp… Viktor Dukhovni
Re: [TLS] New Draft: Using DNS to set the SNI exp… Dave Garrett