pkcs11-bridge

Layer-3 backend of the openssl-provider-wit stack. Exposes a real PKCS#11 token through the narrow tegmentum:key-backend contract, so the same simple-provider-adapter that drives the stub key in Phase 3 can drive a SoftHSM2 / YubiHSM / Luna / CloudHSM key here.

simple-provider-adapter (Layer 2) ↓ tegmentum:key-backend pkcs11-bridge (this component, Layer 3) ↓ pkcs11:host (slot-manager + session + object + crypto + util) pkcs11-wasm-host (Rust wasmtime adapter, ~/git/pkcs11-wasm-host) ↓ libpkcs11.so (libsofthsm2 / Yubico / Luna / ...)

URI format (RFC 7512 subset)

pkcs11:slot-id=0;object=my-tls-key;pin-value=1234

Supported attributes: slot-id, object (CKA_LABEL), id (CKA_ID, may be percent-encoded), pin-value. Tolerated but ignored: token, manufacturer, model, library-version, library-manufacturer, library-description, serial, type, module-path, module-name. The broader RFC 7512 surface (library version filters, pin-source=, etc.) lands in Phase 8 when concrete deployments hit cases the simpler form misses.

slot-id is required in Phase 4 -- token-label-only lookup needs an extra slot-enumeration pass that's pure boilerplate to add but not yet wired.

Mechanism mapping

The adapter passes a typed signature-mechanism to the bridge; this table translates it to a PKCS#11 CKM_*:

Ecdsa(Sha256) -> CKM_ECDSA_SHA256 (token hashes) Ecdsa(Sha384) -> CKM_ECDSA_SHA384 Ecdsa(Sha512) -> CKM_ECDSA_SHA512 Ecdsa(Raw) -> CKM_ECDSA (caller pre-hashed) RsaPkcs1(Sha256) -> CKM_SHA256_RSA_PKCS (token hashes) RsaPkcs1(Sha384) -> CKM_SHA384_RSA_PKCS RsaPkcs1(Sha512) -> CKM_SHA512_RSA_PKCS RsaPkcs1(Raw) -> CKM_RSA_PKCS (caller pre-wrapped DigestInfo) RsaPss({d, m, s}) -> CKM_SHA{256,384,512}_RSA_PKCS_PSS Eddsa -> CKM_EDDSA RsaRaw -> CKM_RSA_X_509

Cipher mechanisms (used for key.decrypt):

RsaPkcs1 -> CKM_RSA_PKCS RsaOaep(_) -> CKM_RSA_PKCS_OAEP (params NOT yet marshalled) RsaRaw -> CKM_RSA_X_509

Status

Phase 4.5 complete (code + composition). The bridge:

• Parses pkcs11: URIs (RFC 7512 subset).
• Opens a PKCS#11 session, logs in with the URI's pin-value.
• Resolves the URI to a private-key CK_OBJECT_HANDLE.
• key.algorithm returns Ec or Rsa derived from CKA_KEY_TYPE.
• key.sign translates the mech and calls C_SignInit + C_Sign in one shot through session.sign.
• key.public_key_info finds the matching public-key object, pulls CKA_EC_PARAMS + CKA_EC_POINT (or CKA_MODULUS + CKA_PUBLIC_EXPONENT), and assembles SubjectPublicKeyInfo DER by hand in src/spki.rs (no der / spki crate dep).
• key.verify / key.decrypt wired analogously.
• key.derive returns MechanismNotSupported (ECDH wiring is Phase 8 work).

Built artifact: ~110 KB wasm. wasm-tools validate clean.

Composes cleanly with simple-provider-adapter (wac plug):

wac plug \
  ~/git/simple-provider-adapter/target/wasm32-wasip2/release/simple_provider_adapter.wasm \
  --plug target/wasm32-wasip2/release/pkcs11_bridge.wasm \
  -o adapter-with-pkcs11.wasm

The composed component exports the full openssl:provider-abi and imports just the unsatisfied pkcs11:host interfaces (6 packages), which a host like ~/git/pkcs11-wasm-host provides through wasmtime::component::Linker::add_to_linker.

Phase 4.6 (SoftHSM smoke) -- DEFERRED. Requires:

• SoftHSM2 installed locally (brew install softhsm).
• An initialized token (use ~/git/pkcs11-wasm-host/scripts/softhsm-setup.sh).
• A wasmtime test harness that loads adapter-with-pkcs11.wasm, satisfies the pkcs11:host imports via pkcs11-wasm-host, calls tegmentum:key-backend.key.sign, and verifies the returned signature against the token's known SPKI via openssl-rs.

The bridge IS structurally complete -- the smoke is the environment-setup-heavy verification step.

Pinned toolchain

wit-bindgen 0.44. Same caveats as simple-provider-adapter:

• avoid identifiers like sha2-256 (use sha256),
• skip the pkcs11:constants WIT package (it uses const declarations that 0.44 doesn't parse) -- the constants we need are duplicated inline in src/lib.rs::ck.