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

"Salz, Rich" <rsalz@akamai.com> Wed, 08 February 2017 02:49 UTC

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From: "Salz, Rich" <rsalz@akamai.com>
To: Ben Schwartz <bemasc@google.com>
Thread-Topic: [TLS] New Draft: Using DNS to set the SNI explicitly
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Date: Wed, 08 Feb 2017 02:49:22 +0000
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Subject: Re: [TLS] New Draft: Using DNS to set the SNI explicitly
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>The examples section says
>   A host that serves many subdomains with a single wildcard certificate
>   could set the SNI of all subdomains to the same fixed subdomain, in
>   order to prevent a passive adversary from learning which subdomain a
>   user is accessing.

> I think that's a worthwhile benefit that would help real users today.

And then the server trusts the Host header?  That probably works if the server has a definitive list of the hosts it serves.  But do not that there can be issues with "just trusting" the Host header.  For example, in a CDN you need to make sure that you don't become an open proxy.  

But I do think that this might be the most likely privacy benefit -- aggregation into a larger anonymity set -- and should be up earlier in the document, or at least telegraphed :)

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