[chrismorgan]

> The dns-01 challenge type will not be available because the DNS is not involved in validating IP addresses. Additionally, there is no mechanism to check CAA records for IP addresses.

Is in-addr.arpa. not usable for these purposes? Given how you can do PTR records to map IP address to domain name, I had just assumed it would be at least theoretically usable for more, even if few or no hosts exposed it so at present.

[baby_souffle]

That just proves you have a way to manipulate DNS.

Doesn’t prove you own the thing the IP routes to.

[mixdup]

I mean that applies to DNS authentication for non-IP certificates, too

[baby_souffle]

> I mean that applies to DNS authentication for non-IP certificates, too

Right, but "show me you own foo.com" is a pretty reasonable bar to clear for issuing a certificate with a CN of "foo.com".

Show me you own `1.1.1.1` by manipulating the DNS for "foo.com" is ... not quite the same.

[chrismorgan]

You seem to be misunderstanding. We're taking about https://en.m.wikipedia.org/wiki/Reverse_DNS_lookup. Either putting records directly on the in-addr.arpa. domain (what I originally had in mind), or if that's not possible, on the domain it points to (which seems a pretty watertight proof method).