[cabfpub] DNSSEC validation for CAA record lookup failure

[Geoff Keating]

At the moment the BRs say:

CAs are permitted to treat a record lookup failure as permission to issue if:

the failure is outside the CA's infrastructure;

the lookup has been retried at least once; and

the domain's zone does not have a DNSSEC validation chain to the ICANN root. 

I suggest replacing the last item with “the record being looked up is classified as ‘Insecure’ under RFC 4035 section 4.3, as amended.”

The most common case of this will be that the record being looked up is a CAA record for, say, example.com <http://example.com/>; the .com servers have been contacted successfully, producing authenticated NS records for example.com <http://example.com/>, but the example.com <http://example.com/> name servers cannot be contacted; and the .com servers have provided authenticated denial of existence for a DS record for example.com <http://example.com/>.  This is covered in RFC 4035 section 5.2, “If the validator authenticates an NSEC RRset that proves that no DS RRset is present for this zone, then there is no authentication path leading from the parent to the child."
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