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Re: [TLS] Final nail in the coffin for cleartext SNI/ALPN in TLS 1.3

Seth David Schoen <schoen@eff.org> Thu, 07 November 2013 19:54 UTC

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Date: Thu, 07 Nov 2013 11:54:46 -0800
From: Seth David Schoen <schoen@eff.org>
To: Daniel Kahn Gillmor <dkg@fifthhorseman.net>
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Subject: Re: [TLS] Final nail in the coffin for cleartext SNI/ALPN in TLS 1.3
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Daniel Kahn Gillmor writes:

> Sure, but that is a bug in DNS, not a bug in TLS, and there are
> proposals (however farfetched) to work around that, like DNSCurve
> [0]. But fixing DNS leakage is out-of-scope for this working group.
> 
> Fixing TLS is in-scope, though, and TLS shouldn't leak information
> just because other related protocols also leak information.

And there might actually be some passive attackers who are on-path
with respect to the TLS session and not with respect to the DNS lookup
(for example, the DNS query might have been satisified by a recursive
resolver that's closer to the client than the eavesdropper is).

With CDNs, you sometimes get some pretty strange bedfellows on a single
server IP address, so the marginal information leak from SNI could be
pretty high!

-- 
Seth Schoen  <schoen@eff.org>
Senior Staff Technologist                       https://www.eff.org/
Electronic Frontier Foundation                  https://www.eff.org/join
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