Make RR::CDS (resp RR::CDNSKEY) subclass of RR::DS (resp RR::DNSKEY)

[ghost]

Purpose

Instead of implementing specific methods, reuse the one from Zonemaster::LDNS::RR::DS and Zonemaster::LDNS::RR::DNSKEY since a CDS (resp CDNSKEY) record is identical to a DS (DNSKEY) record, see RFC 7344 section 3.1 and 3.2.

Context

#114

Changes

• make Zonemaster::LDNS::RR::CDS a subclass of Zonemaster::LDNS::RR::DS
• make Zonemaster::LDNS::RR::CDNSKEY a subclass of Zonemaster::LDNS::RR::DNSKEY

How to test this PR

Unit tests are provided.

[ghost]

It seems the keytag method can't be used for CDNSKEY because it relies on ldns_calc_keytag() that does not accept CDNSKEY type (see https://github.com/NLnetLabs/ldns/blob/1.8.3/dnssec.c#L287-L291)

uint16_t
ldns_calc_keytag(const ldns_rr *key)
{
        ...
	if (ldns_rr_get_type(key) != LDNS_RR_TYPE_DNSKEY &&
	    ldns_rr_get_type(key) != LDNS_RR_TYPE_KEY
	    ) {
		return 0;
	}
        ...
}

Applying this patch in libldns would fix the issue:

diff --git a/dnssec.c b/dnssec.c
index fbaa518a..63bdab09 100644
--- a/dnssec.c
+++ b/dnssec.c
@@ -285,7 +285,8 @@ ldns_calc_keytag(const ldns_rr *key)
        }
 
        if (ldns_rr_get_type(key) != LDNS_RR_TYPE_DNSKEY &&
-           ldns_rr_get_type(key) != LDNS_RR_TYPE_KEY
+           ldns_rr_get_type(key) != LDNS_RR_TYPE_KEY &&
+           ldns_rr_get_type(key) != LDNS_RR_TYPE_CDNSKEY
            ) {
                return 0;
        }

[matsduf]

It seems the keytag method can't be used for CDNSKEY because it relies on ldns_calc_keytag() that does not accept CDNSKEY type (see https://github.com/NLnetLabs/ldns/blob/1.8.3/dnssec.c#L287-L291)
(...)

Applying this patch in libldns would fix the issue:
(...)

Do you see any work-around, or must LDNS be fixed first? Have you created an issue or a PR there?

[ghost]

I've opened NLnetLabs/ldns#187