Skip to main content

POST /api/crypto/hmac

The keyed data hash -- HMAC-SHA384 under a key the key server holds.

Computes HMAC-SHA384 (RFC 2104 over SHA-384) of data, keyed with the raw bytes of the symmetric key hiddenLink names. The key server computes it in one request; the key never leaves the key server. The caller needs a role granting HMAC Data and an entry on the key's access control list, exactly as a decrypt does.

Each refusal of the key server is its own answer, and each is audited with its cause (GET /api/audit?reason=...):

  • the hidden link names no key -- 404 KEY_NOT_FOUND (audit reason objectNotFound);
  • the key's access control list refuses the caller -- 403 ACL_DENIED (aclDenied);
  • no role grants the caller HMAC Data -- 403 ACCESS_DENIED (roleDenied).

A missing, empty or non-canonical hiddenLink, a missing or non-canonical data, and a message over 16777216 bytes (one wire field) are refused with 400 before anything is sent.

Authentication​

Send the session id as Authorization: Bearer <session id>, and an RFC 9449 DPoP proof in the DPoP header if your session is bound to a key. The two are required together, not as alternatives — see Authenticating and Proving you hold your key.

This surface sets no cookie

There is no session cookie on any response and none is read on any request. Do not set credentials: "include" on a browser fetch.

Request​

FieldTypeRequiredDescription
hiddenLinkstringyesCanonical base64 of the key's hidden link (its ttag). Must not be empty.
datastringyesCanonical base64 of the message. The empty string is the empty message.

Example

{
  "hiddenLink": "...",
  "data": "..."
}

Responses​

200​

The MAC.

FieldTypeRequiredDescription
algorithmstring (HMAC-SHA384)yes
macstringyesCanonical base64 of the 48-byte MAC.
macBytesinteger (48)yes

Example

{
  "algorithm": "HMAC-SHA384",
  "mac": "...",
  "macBytes": 48
}

400​

The request was refused before anything was sent to the key server.

Most 400s on this surface carry code: BAD_REQUEST and a detail naming the field and saying what the key server would otherwise have done with it. A large share of them exist because the value would have been ACCEPTED downstream and quietly meant something else -- an empty string that reaches the wire as "mint a new key", a zero-length identifier that names no object, a numeric flag word that clears bits the caller did not name.

INVALID_ARGUMENT is the one 400 that DID reach the key server: the key server itself refused the argument (ERR_INVALID_ARGUMENT), and detail is its own sentence. On POST /api/certificates/enroll that is a certificate that cannot authenticate -- certificate not permitted for authentication: keyUsage is present without digitalSignature (...), ... extendedKeyUsage is present without clientAuth (...), or certificate expired at enrolment: notAfter <UTC> ... -- and a multi-certificate body that carries one such leaf persists nothing.

401​

No live session, a DPoP proof that did not verify, or a certificate session whose certificate the key server now refuses.

SESSION_NOT_FOUND -- the credential names no session this Gateway holds. SESSION_EXPIRED -- it aged out. Both carry reauth: true; obtain a new credential rather than retrying.

PROOF_* -- the sender constraint refused. See the DPoP section of this document for the full table; PROOF_MALFORMED is a 400 and PROOF_REPLAY_CACHE_FULL a 503, and the rest are here.

SCOPED_CREDENTIAL_EXPIRED -- a scoped browser credential passed its fixed lifetime. Use does not extend it: an idle timeout would be refreshed by exactly the traffic a stolen handle produces.

CERTIFICATE_REVOKED -- on a session established by certificate login, the key server re-checks the certificate that session was established with on its operations, and it is now named by revocation evidence (ADR 0115). detail is the key server's sentence. Every later operation of the session is refused the same way; log in with a different certificate.

403​

ACL_DENIED (the key's access control list), ACCESS_DENIED (no role grants HMAC Data), or OBJECT_NOT_IN_CREDENTIAL_SCOPE.

404​

KEY_NOT_FOUND -- the hidden link names no key.

500​

A fault rather than a refusal.

OP_FAILED is the catch-all: the key server refused in words that match no classified pattern, so the Gateway cannot say more than that the operation did not happen. Some key server refusals that are conceptually a caller error arrive here rather than as a 4xx, because the wire carries no distinguishing code -- where a route can recognise one from its message it maps it, and each such mapping is documented on the operation.

503​

A capacity ceiling or a missing deployment prerequisite. retryable says which.

A scope of session or process names the ceiling that was hit, and the response carries Retry-After.

BUILD_NOT_ADMITTED (scope: process, retryable: true, Retry-After): the key server does not admit this Gateway's client build. Every key-server connection the Gateway opens attests the signed release it runs (TE_RELEASE_MANIFEST) right after it authenticates; while that attestation is refused -- the release is not registered at the key server's code-signing level, the level was raised under it, or the installed files no longer match the signed manifest -- every route but GET /api/health and GET /api/ready answers this, and detail names the cause. It is never a 401 or a 403: no credential or role of the caller's is at fault. The Gateway re-attempts on a timer and recovers without a restart once the key server admits it; GET /api/ready says when.

Error handling​

Every failure answers JSON carrying at least code and detail. Match on code — detail is written for a human debugging the call and its wording is not part of the contract. See the error model.

StatusMeaning
400The request was refused before anything was sent to the key server. Most 400s on this surface carry code: BAD_REQUEST and a detail naming the field and saying what the key server would otherwise have done with it. A large share of them exist because the value would have been ACCEPTED downstream and quietly meant something else -- an empty string that reaches the wire as "mint a new key", a zero-length identifier that names no object, a numeric flag word that clears bits the caller did not name. INVALID_ARGUMENT is the one 400 that DID reach the key server: the key server itself refused the argument (ERR_INVALID_ARGUMENT), and detail is its own sentence. On POST /api/certificates/enroll that is a certificate that cannot authenticate -- certificate not permitted for authentication: keyUsage is present without digitalSignature (...), ... extendedKeyUsage is present without clientAuth (...), or certificate expired at enrolment: notAfter <UTC> ... -- and a multi-certificate body that carries one such leaf persists nothing.
401No live session, a DPoP proof that did not verify, or a certificate session whose certificate the key server now refuses. SESSION_NOT_FOUND -- the credential names no session this Gateway holds. SESSION_EXPIRED -- it aged out. Both carry reauth: true; obtain a new credential rather than retrying. PROOF_* -- the sender constraint refused. See the DPoP section of this document for the full table; PROOF_MALFORMED is a 400 and PROOF_REPLAY_CACHE_FULL a 503, and the rest are here. SCOPED_CREDENTIAL_EXPIRED -- a scoped browser credential passed its fixed lifetime. Use does not extend it: an idle timeout would be refreshed by exactly the traffic a stolen handle produces. CERTIFICATE_REVOKED -- on a session established by certificate login, the key server re-checks the certificate that session was established with on its operations, and it is now named by revocation evidence (ADR 0115). detail is the key server's sentence. Every later operation of the session is refused the same way; log in with a different certificate.
403ACL_DENIED (the key's access control list), ACCESS_DENIED (no role grants HMAC Data), or OBJECT_NOT_IN_CREDENTIAL_SCOPE.
404KEY_NOT_FOUND -- the hidden link names no key.
500A fault rather than a refusal. OP_FAILED is the catch-all: the key server refused in words that match no classified pattern, so the Gateway cannot say more than that the operation did not happen. Some key server refusals that are conceptually a caller error arrive here rather than as a 4xx, because the wire carries no distinguishing code -- where a route can recognise one from its message it maps it, and each such mapping is documented on the operation.
503A capacity ceiling or a missing deployment prerequisite. retryable says which. A scope of session or process names the ceiling that was hit, and the response carries Retry-After. BUILD_NOT_ADMITTED (scope: process, retryable: true, Retry-After): the key server does not admit this Gateway's client build. Every key-server connection the Gateway opens attests the signed release it runs (TE_RELEASE_MANIFEST) right after it authenticates; while that attestation is refused -- the release is not registered at the key server's code-signing level, the level was raised under it, or the installed files no longer match the signed manifest -- every route but GET /api/health and GET /api/ready answers this, and detail names the cause. It is never a 401 or a 403: no credential or role of the caller's is at fault. The Gateway re-attempts on a timer and recovers without a restart once the key server admits it; GET /api/ready says when.