Re: [DNSOP] Proposal for a new record type: SNI

"John Levine" <> Fri, 17 February 2017 22:03 UTC

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Subject: Re: [DNSOP] Proposal for a new record type: SNI
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In article <> you write:
>I know this approach is controversial, so I'm also very curious to hear any
>suggestions of other ways that we could fix this privacy leak without
>slowing down everyone's connections.

I have problems with the word "other".  This approach depends for its
security on the assumption that it is hard to reverse SNI record
lookups, that is, to find the qname(s) that have SNI records with
given contents.

That is a poor assumption.  There are many large passive DNS
databases, and a lot of people have access to them.  My working
assumption is that anyone sophisticated enough to peek at TLS
handshake packets is sophisticated enough to find a passive DNS

So to me the question is whether the small speculative incremental
increase in user security is worth the investment to define a new
record type, add it to DNS servers and provisioning systems, add it to
web server configuration languages, and set up whatever infrastructure
is needed to coordinate the published SNI records and what the web
servers expect.

I'd also note that if the assumption is that people will publish SNI
records through the usual registrar and dns hosting operators managed
through web consoles, there is no chance that the webware will support
SNI records.  We know this because they don't support any other
RRTYPEs defined in the past decade, either.