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Turns out DNSSEC-signed CAA records provide cryptographic proof that can be archived and used for auditing purposes that a particular issuer of certificates was
by alwillis 7y ago
Turns out DNSSEC-signed CAA records provide cryptographic proof that can be archived and used for auditing purposes that a particular issuer of certificates was indeed authorized to do so for a particular domain.
DNSSEC also enables them to verify whether empty CAA records are intentional or the result of something malicious.
From https://tools.ietf.org/html/rfc6844#section-4.1 https://tools.ietf.org/html/rfc6844#section-4.1
Use of DNSSEC to authenticate CAA RRs is strongly RECOMMENDED but not required. An issuer MUST NOT issue certificates if doing so would conflict with the relevant CAA Resource Record set, irrespective of whether the corresponding DNS records are signed.
DNSSEC provides a proof of non-existence for both DNS domains and RR set within domains. DNSSEC verification thus enables an issuer to determine if the answer to a CAA record query is empty because the RR set is empty or if it is non-empty but the response has been suppressed.
Use of DNSSEC allows an issuer to acquire and archive a proof that they were authorized to issue certificates for the domain.
Verification of such archives MAY be an audit requirement to verify CAA record processing compliance. Publication of such archives MAY be a transparency requirement to verify CAA record processing compliance.
- tptacek 7y agoEveryone in this thread knows what a CAA record is. Once again, it is my claim that Lets Encrypt does not operationally rely on DNSSEC. Nick Lamb disagreed, and suggested that ISRG staff would stick up for DNSSEC but for my presence on the thread. I reply with a quote from a Lets Encrypt developer: "I think DNSSEC is rubbish and so does the whole Boulder development team". I think you should take this up with them.
- alwillis 7y agoEveryone in this thread knows what a CAA record is. That’s not the point, although I doubt most people on this thread knew that the use of DNSSEC is strongly recommended for issuers of certificates. I’m pretty sure Lets Encrypt doesn’t operationally depend on DNSSEC, but if they’re issuing certificates to a zone with DNSSEC-signed CAA resource records, that’s irrefutable proof of the intent of the zone operator, something that Lets Encrypt and other issuers of certificates should probably pay attention to, regardless of the personal feelings of their engineers about any particular standard. Without DNSSEC, there’s no way to know if the CAA records have been tampered with when using something like ACME.