Re: [DNSOP] WG review of draft-ietf-homenet-dot-03

Paul Wouters <paul@nohats.ca> Tue, 21 March 2017 03:08 UTC

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Date: Mon, 20 Mar 2017 23:08:11 -0400 (EDT)
From: Paul Wouters <paul@nohats.ca>
To: Andrew Sullivan <ajs@anvilwalrusden.com>
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Subject: Re: [DNSOP] WG review of draft-ietf-homenet-dot-03
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On Mon, 20 Mar 2017, Andrew Sullivan wrote:

> On Mon, Mar 20, 2017 at 06:19:45PM -0400, Paul Wouters wrote:
>> I am assuming that if stubs are validating, then they must also support
>> excluding special queries from validation, such as mDNS, .onion and
>> .homenet.
>
> What possible basis do you have for this?  This is in effect a
> requirement that every validating stub (or resolver?  I dunno) be
> upgraded to support homenet.

https://tools.ietf.org/html/rfc7686 dated October 2015 did this too:

    3.  Name Resolution APIs and Libraries: Resolvers MUST either respond
        to requests for .onion names by resolving them according to
        [tor-rendezvous] or by responding with NXDOMAIN [RFC1035].

    4.  Caching DNS Servers: Caching servers, where not explicitly
        adapted to interoperate with Tor, SHOULD NOT attempt to look up
        records for .onion names.  They MUST generate NXDOMAIN for all
        such queries.

    5.  Authoritative DNS Servers: Authoritative servers MUST respond to
        queries for .onion with NXDOMAIN.

>> The .homenet queries should never reach real DNS servers
>
> But they're going to.

Of course. I was just saying that when they do, there is no good answer
for them.

>> not think an insecure delegation in the root is required. If the DNS
>> resolver doesn't know how to handle .homenet, it is already as wrong
>> as it can be, regardless of the type of answer.
>
> This doesn't follow.  If the resolver gets it wrong in the case of a
> provably-unsigned answer, it can just continue its resolution as it
> ever wanted.  It won't be able to validate, since it does not have a
> local trust anchor.  But it'll work.

But any answer it gets makes no sense anyway, as it doesn't have the
actual required data of the real local .homenet zone. So whether you
give a NXDOMAIN or SERVFAIL or return an A record with 127.0.53.53
doesn't really matter, whether you are 8.8.8.8 or 216.146.35.35.

I guess the only possible exception to this is if the device in the
.homenet got multiple DNS servers from DHCP, and only one of them
and not the first one handles .homenet properly. Of course that's
a pretty broken setup to begin with, so I'm not too worried about
breaking that more.

Paul