Rework X.509 cert/csr/crl extension representation - #449
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28 commits is a bit much. 😄
Suggest we split off a separate PR for the first bunch of commits, prior to the version bump? I have reviewed those and will be able to approve that quickly.
Add an `Extension` trait (OID, criticality, DER value) and a single `write_extension()` serializer so each extension's encoding lives beside its presence logic as types are migrated. Extensions whose OID and criticality are fixed by the profile defining them implement the `StaticExtension` trait instead, receiving `Extension` through a blanket impl. Move authority key identifier writing into the module as the first static extension, replacing `write_x509_authority_key_identifier()` in the certificate and CRL paths.
Port the SAN extension into an `ext::SubjectAlternativeName` type whose `from_params` constructor owns the presence decision, replacing `write_subject_alt_names()` in the certificate and CSR paths. The RFC 5280 §4.1.2.6 criticality rule (critical if the subject DN is empty) is now unit tested.
Port the KeyUsage extension into an `ext::KeyUsage` static extension whose `from_params` constructor owns the presence decision, replacing `write_key_usage()` in the certificate and CSR paths. The minimal-length BIT STRING encoding (including the 9-bit `decipherOnly` case) remains covered by the existing certificate tests.
Port the EKU extension into an `ext::ExtendedKeyUsage` static extension whose `from_params` constructor owns the presence decision, replacing `write_extended_key_usage()` in the certificate and CSR paths.
Port the NameConstraints extension into an `ext::NameConstraints` static extension whose `from_params` constructor owns the presence decision (including omitting the extension when both subtrees are empty), replacing the inline writer and `write_general_subtrees()` in the certificate path.
Port the certificate CRLDistributionPoints extension into an `ext::CrlDistributionPoints` static extension whose `from_params` constructor owns the presence decision, replacing the inline writer in the certificate path. The empty-URIs rejection in `serialize_der_with_signer` is unchanged.
Port the SKI extension into an `ext::SubjectKeyIdentifier` static extension constructed from a `KeyIdMethod` and the subject public key info. The current behavior of only emitting SKI for `IsCa::Ca`/`ExplicitNoCa` certificates (and never for CSRs) is preserved.
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Done. I lifted everything after the version bump to a stacked follow-up PR #454 |
djc
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Sep 21, 2026
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This starts the extension rework from #446. Each extension is now its own type in a new ext module, with the presence decision living next to the encoding. Breaking changes are lifted to the follow-up #454