This is a load-bearing internal refactor with no user-visible behavior
change. The new internal/crypto/signer package abstracts CA private-key
signing behind a Signer interface (embeds stdlib crypto.Signer + adds
Algorithm()). The local issuer now consumes this interface; the
historical c.caKey crypto.Signer field is renamed c.caSigner signer.Signer.
What landed:
* internal/crypto/signer/ — new stdlib-only package
- Signer interface: crypto.Signer + Algorithm()
- Algorithm enum: RSA-2048, RSA-3072, RSA-4096, ECDSA-P256, ECDSA-P384
- Driver interface: Load / Generate / Name
- FileDriver: production driver, wraps file-on-disk PEM, hooks for
DirHardener + Marshaler so the local package can inject Bundle 9
keystore.ensureKeyDirSecure + keymem.marshalPrivateKeyAndZeroize
- MemoryDriver: in-memory test driver; safe for concurrent use
- parse.go: ParsePrivateKey moved here from local.go (PKCS#1, SEC 1, PKCS#8)
- 91.6% coverage (gate ≥85)
* internal/connector/issuer/local/local.go — refactor
- Rename c.caKey crypto.Signer → c.caSigner signer.Signer
- Rewire 4 signing call sites: leaf cert (line ~613), CRL (~849),
OCSP response (~887), CA bootstrap (~482) — all access the
interface; the bootstrap also switches to interface-level
Public() + Signer
- Wrap freshly-generated and freshly-loaded keys; reject Ed25519
and other unsupported algorithms at load time (was silently
accepted before, would have failed at first sign)
- Delete the duplicated parsePrivateKey helper (single source of
truth now lives in the signer package)
- Update the L-014 threat-model comment block (lines 1-29) with a
forward-reference paragraph: file-on-disk caveats apply only to
FileDriver-backed signers; alternative drivers close that leg
- Coverage 86.7 → 86.5 (above CI floor of 86); the 0.2pp drop is
mechanical from deleting parsePrivateKey, partially recovered by
a new test pinning the Wrap error path
* internal/crypto/signer/equivalence_test.go — Phase 3 safety net
- RSA byte-strict equality for leaf certs / CRLs / OCSP responses
(PKCS#1 v1.5 is deterministic)
- ECDSA TBS-strict equality (signature differs because of random k)
- Both signatures independently validate against the CA
- Negative sentinel proves the equivalence checker isn't trivially-
passing
* docs/architecture.md — new 'CA Signing Abstraction' section under
Security Model, with ASCII diagram of FileDriver / MemoryDriver /
future PKCS11Driver / future CloudKMSDriver
* Test file mechanical edits (only):
- bundle9_coverage_test.go: parsePrivateKey → signer.ParsePrivateKey
(function moved, not behavior changed)
- local_test.go: append one targeted test
(TestSubCA_LoadCAFromDisk_RejectsUnsupportedKeyAlgorithm) that
pins the new Wrap error path I introduced — recovers coverage
cost of the deletion above
What did NOT change (verified empty diffs):
* api/openapi.yaml
* migrations/
* internal/connector/issuer/interface.go
* go.mod / go.sum (no new dependencies; stdlib only)
This refactor is the prerequisite for three downstream items:
- PKCS#11/HSM driver (V3-Pro)
- CRL/OCSP responder (V2)
- SSH CA lifecycle (V2)
Each of those adds a new signing call site. Doing the abstraction now
costs once; deferring would cost three times.
shankar0123