Re: [Doh] Authentication in draft-ietf-doh-resolver-associated-doh-03.txt

Ben Schwartz <bemasc@google.com> Mon, 25 March 2019 16:10 UTC

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References: <155341529409.18062.10657099011172813446@ietfa.amsl.com> <20190325110136.GA23793@laperouse.bortzmeyer.org> <08BD5718-CD1F-47B3-A4FB-4040F8E9FC4B@icann.org>
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From: Ben Schwartz <bemasc@google.com>
Date: Mon, 25 Mar 2019 12:10:29 -0400
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To: Paul Hoffman <paul.hoffman@icann.org>
Cc: DoH WG <doh@ietf.org>
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Subject: Re: [Doh] Authentication in draft-ietf-doh-resolver-associated-doh-03.txt
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On Mon, Mar 25, 2019 at 7:37 AM Paul Hoffman <paul.hoffman@icann.org> wrote:

> On Mar 25, 2019, at 12:01 PM, Stéphane Bortzmeyer <bortzmeyer@nic.fr>
> wrote:
> > Otherwise, even after reading the whole thread "Reviewing
> > Resolver-Associated DOH", I don't understand why https is required in
> > section 2. We don't require DNSSEC in section 3, so why having
> > stronger requirments for HTTP? Since having certificates for IP
> > addresses will be difficult in practice, why not just accepting http
> > as well as https? (Or, <horror>https without cert. checking</horror>.)
>
> The reason I didn't drop down to http: is that doing so evokes the
> <horror> response, even though you are quite correct that the other two
> methods given in this document do not offer any authentication. So, let me
> ask the WG:
>
> Would this document be better off with all three methods being equally
> unauthenticated? Doing so would remove the "but you can't get IP address
> certificates!" argument that keeps coming up (even though that is
> overstated). Doing so would simplify the security considerations by making
> all three protocols have the same obvious weakness.
>
> An alternative is to have two URI, one with https: and one with http:, and
> explain that trying the first might be a good idea but to fall back to the
> second if authentication fails.
>
> Thoughts?
>

Given that the protocol is called "DNS over HTTPS", running it over
unencrypted HTTP seems like a contradiction.  It also complicates any
security status indication by introducing a mode that no longer offers any
confidentiality benefit over standard DNS.

Apart from security issues, insecure HTTP is generally restricted to
HTTP/1.1.  DoH implementations are strongly encouraged to use HTTP/2,
because HTTP/1.1 requires in-order responses.  Running DoH over HTTP/1.1
increases the likelihood of performance problems.

--Paul Hoffman
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