Re: [TLS] ESNIKeys over complex

Florian Weimer <fweimer@redhat.com> Wed, 21 November 2018 10:31 UTC

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From: Florian Weimer <fweimer@redhat.com>
To: Paul Wouters <paul@nohats.ca>
Cc: Stephen Farrell <stephen.farrell@cs.tcd.ie>, "\<tls\@ietf.org\>" <tls@ietf.org>
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Date: Wed, 21 Nov 2018 11:31:09 +0100
In-Reply-To: <alpine.LRH.2.21.1811210215540.4260@bofh.nohats.ca> (Paul Wouters's message of "Wed, 21 Nov 2018 02:28:45 -0500 (EST)")
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Subject: Re: [TLS] ESNIKeys over complex
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* Paul Wouters:

> On Wed, 21 Nov 2018, Stephen Farrell wrote:
>
>>> We currently permit >1 RR, but
>>> actually
>>> I suspect that it would be better to try to restrict this.
>>
>> Not sure we can and I suspect that'd raise DNS-folks' hackles,
>> but maybe I'm wrong.
>
> I think the SOA record is the only exception allowed (and there
> is an exception to that when doing AXFR I believe)
>
> Usually these things are defined as "pick the first DNS RRTYPE
> that satisfies you".

Not sure what you mean by that (RRTYPE?).

The DNAME algorithm (RFC 6672) only works if there is a single DNAME
record for an owner name.  RFC 1034 is also pretty clear that only CNAME
record is permitted per owner name.

To be honest, I don't expect much opposition from DNS people, as long as
there is no expectation that the DNS layer is expected to reject
multiple records.  If the higher-level protocol treats non-singleton
RRsets as a hard error, I expect that would be fine.

DNS treats RRsets as an atomic unit, so there is no risk here that a
zone file change ends up producing a multi-record RRset due to caching.

Thanks,
Florian