A maioria das operadoras esperaria que o registro órfão DS
fosse ignorado. Múltiplos DS
RRs, um ou mais dos quais podem não estar alinhados com o DNSKEY
RRset correspondente, podem ser encontrados e isso é bem documentado.
2.4. Including DS RRs in a Zone
The DS resource record establishes authentication chains between DNS
zones. A DS RRset SHOULD be present at a delegation point when the
child zone is signed. The DS RRset MAY contain multiple records,
each referencing a public key in the child zone used to verify the
RRSIGs in that zone. All DS RRsets in a zone MUST be signed, and DS
RRsets MUST NOT appear at a zone's apex.
A DS RR SHOULD point to a DNSKEY RR that is present in the child's
apex DNSKEY RRset, and the child's apex DNSKEY RRset SHOULD be signed
by the corresponding private key. DS RRs that fail to meet these
conditions are not useful for validation, but because the DS RR and
its corresponding DNSKEY RR are in different zones, and because the
DNS is only loosely consistent, temporary mismatches can occur.
Isso estabelece que vários DS
RRs são permitidos e que cada um desses RRs SHOULD
seja assinado por um DNSKEY
RR correspondente. Embora o comportamento exato ao encontrar um órfão DS
RR não seja explicitado, é estabelecido que as incompatibilidades podem acontecer e acontecem, e são esperadas.
DNS is only loosely consistent
RRset e os RRs assinados.
5.11. Mandatory Algorithm Rules
The last paragraph of Section 2.2 of [RFC4035] includes rules
describing which algorithms must be used to sign a zone. Since these
rules have been confusing, they are restated using different language
here:
The DS RRset and DNSKEY RRset are used to signal which algorithms
are used to sign a zone. The presence of an algorithm in either a
zone's DS or DNSKEY RRset signals that that algorithm is used to
sign the entire zone.
A signed zone MUST include a DNSKEY for each algorithm present in
the zone's DS RRset and expected trust anchors for the zone. The
zone MUST also be signed with each algorithm (though not each key)
present in the DNSKEY RRset. It is possible to add algorithms at
the DNSKEY that aren't in the DS record, but not vice versa. If
more than one key of the same algorithm is in the DNSKEY RRset, it
is sufficient to sign each RRset with any subset of these DNSKEYs.
It is acceptable to sign some RRsets with one subset of keys (or
key) and other RRsets with a different subset, so long as at least
one DNSKEY of each algorithm is used to sign each RRset.
Likewise, if there are DS records for multiple keys of the same
algorithm, any subset of those may appear in the DNSKEY RRset.
This requirement applies to servers, not validators. Validators
SHOULD accept any single valid path. They SHOULD NOT insist that all
algorithms signaled in the DS RRset work, and they MUST NOT insist
that all algorithms signaled in the DNSKEY RRset work. A validator
MAY have a configuration option to perform a signature completeness
test to support troubleshooting.
A imagem geral fica mais clara aqui; Os validadores não devem estar no negócio de policiar todas as permutações possíveis de DS
e DS
. O detalhe mais importante é se existe ou não um caminho válido.