Re: [DNSOP] extension of DoH to authoritative servers

Bjørn Mork <bjorn@mork.no> Thu, 14 February 2019 12:12 UTC

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Subject: Re: [DNSOP] extension of DoH to authoritative servers
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Vladimír Čunát <vladimir.cunat+ietf@nic.cz>; writes:

> You can still multiplex based on SNI sent by the client.  HTTPS clients
> surely send it commonly.  DoT clients perhaps not so often, but that's
> just an implementation detail (which I was fixing in the past few weeks
> in knot-resolver, incidentally).

My understanding of the reference to BCP195 from
https://tools.ietf.org/html/rfc7858#section-3.2
is that SNI support is required for all DoT implementations.

> I'm not sure how easy SNI-based multiplexing is to configure with
> nowadays software, but I believe I've heard of some such setup with
> nginx.  And I don't have any idea whether SNI encryption would interfere
> with that, but I hope not.  ESNI will be a key part of DNS privacy,
> though mainly for the non-DNS traffic.

It's simple to do with haproxy at least:
https://www.haproxy.com/blog/enhanced-ssl-load-balancing-with-server-name-indication-sni-tls-extension/

...which incidentally also can be used to support DoT with *any* DNS
server as backend.



Bjørn