certctl/docs/acme-server.md

certctl ACME Server (Built-in)

certctl ships an RFC 8555 + RFC 9773 ARI ACME server endpoint at /acme/profile/<profile-id>/*. Any RFC 8555 client (cert-manager 1.15+, Caddy, Traefik, win-acme, certbot, Posh-ACME) can integrate with certctl as an ACME issuer with no certctl-side modification — closing the "deploy a certctl agent on every K8s node" friction that costs deals to external PKI vendors today.

Phase status (2026-05-03): Phase 3 — Phase 2's surface plus challenge validation: HTTP-01 (RFC 8555 §8.3), DNS-01 (§8.4), and TLS-ALPN-01 (RFC 8737). Profiles in challenge mode now resolve end-to-end: client POSTs to /challenge/<id>, the server dispatches a bounded-concurrency worker pool to fetch the proof out-of-band, the validator updates the challenge → authz → order status chain on completion. Profiles in trust_authenticated mode are unchanged. Track shipped phases via git log --grep='acme-server:'.

Configuration

All ACME-server config uses the CERTCTL_ACME_SERVER_* env-var prefix (distinct from CERTCTL_ACME_* which configures the consumer-side issuer connector). The struct definition lives in internal/config/config.go::ACMEServerConfig.

Env var	Default	Phase	Description
CERTCTL_ACME_SERVER_ENABLED	false	1a	Master enable flag. Phase 1a's handler is constructed unconditionally so the registry shape stays stable; routes are registered in internal/api/router/router.go::RegisterHandlers regardless. Operators flip this on after configuring per-profile auth_mode.
CERTCTL_ACME_SERVER_DEFAULT_AUTH_MODE	trust_authenticated	1a	Default value for certificate_profiles.acme_auth_mode on newly-created profiles. Existing profiles retain their stored value. Per-profile column is the source of truth at request time.
CERTCTL_ACME_SERVER_DEFAULT_PROFILE_ID	""	1a	When set, /acme/* shorthand mirrors /acme/profile/<DefaultProfileID>/* for single-profile deployments. When empty, requests to the shorthand return RFC 7807 + RFC 8555 §6.7 userActionRequired.
CERTCTL_ACME_SERVER_NONCE_TTL	5m	1a	How long an issued ACME nonce remains valid before the JWS verifier (Phase 1b) returns urn:ietf:params:acme:error:badNonce per RFC 8555 §6.5.1. Tune up if cert-manager + certctl clocks frequently skew.
CERTCTL_ACME_SERVER_TOS_URL	""	1a	Optional meta.termsOfService URL in the directory document.
CERTCTL_ACME_SERVER_WEBSITE	""	1a	Optional meta.website URL in the directory document.
CERTCTL_ACME_SERVER_CAA_IDENTITIES	(empty)	1a	Comma-separated meta.caaIdentities list.
CERTCTL_ACME_SERVER_EAB_REQUIRED	false	1a	meta.externalAccountRequired advertisement. EAB enforcement is a follow-up; Phase 1a only advertises.
CERTCTL_ACME_SERVER_ORDER_TTL	24h	2	Reserved field, parsed in Phase 1a so operators can set it ahead of Phase 2's order endpoints.
CERTCTL_ACME_SERVER_AUTHZ_TTL	24h	2	Reserved.
CERTCTL_ACME_SERVER_HTTP01_CONCURRENCY	10	3	Reserved.
CERTCTL_ACME_SERVER_DNS01_RESOLVER	8.8.8.8:53	3	Reserved.
CERTCTL_ACME_SERVER_DNS01_CONCURRENCY	10	3	Reserved.
CERTCTL_ACME_SERVER_TLSALPN01_CONCURRENCY	10	3	Reserved.

Per-profile auth mode

Two modes per certificate_profiles.acme_auth_mode:

• trust_authenticated (default for internal PKI). The JWS- authenticated ACME account is trusted to issue certs for any identifier the profile policy allows; there is no per-identifier ownership proof. The most common certctl use case.
• challenge. Full HTTP-01 + DNS-01 + TLS-ALPN-01 validation per RFC 8555 §8. Required when certctl is exposing public-trust-style PKI.

A single certctl-server can serve both modes simultaneously — the mode is read from the bound profile's column at request time, not cached at server start. Operators can flip a profile's mode via SQL and the next order picks up the new mode without restart.

The CERTCTL_ACME_SERVER_DEFAULT_AUTH_MODE env var sets the default value for newly-created profiles (e.g. via the certctl API). Existing profile rows retain whatever value they were created with.

TLS trust bootstrap (read this before configuring cert-manager)

When certctl-server uses a self-signed TLS bootstrap cert (deploy/test/certs/server.crt is the demo default; see docs/tls.md), cert-manager 1.15+ will refuse to talk to the directory URL unless the certctl root is trusted. The fix lives in ClusterIssuer.spec.acme.caBundle:

apiVersion: cert-manager.io/v1
kind: ClusterIssuer
metadata:
  name: certctl-test
spec:
  acme:
    server: https://certctl.example.com:8443/acme/profile/prof-corp/directory
    email: ops@example.com
    caBundle: |
      LS0tLS1CRUdJTi...   # base64-encoded PEM of certctl's self-signed root
    privateKeySecretRef:
      name: certctl-test-account-key
    solvers:
      - http01:
          ingress:
            class: nginx

The caBundle value is the base64-encoded PEM of the root that signed your certctl-server's TLS certificate. Extract it from your operator bootstrap (e.g. cat deploy/test/certs/ca.crt | base64 -w0).

This is the single biggest first-time-deploy footgun on the cert-manager integration path. The full cert-manager walkthrough lands in Phase 6; the caBundle requirement is flagged here in Phase 1a's docs because operators hit it the moment they try to point a real ACME client at certctl.

Endpoints (Phase 2)

Routes registered in internal/api/router/router.go::RegisterHandlers:

Method	Path	RFC ref	Auth	Description
GET	/acme/profile/{id}/directory	RFC 8555 §7.1.1	unauth	Per-profile directory document.
HEAD	/acme/profile/{id}/new-nonce	RFC 8555 §7.2	unauth	Returns 200 + Replay-Nonce header.
GET	/acme/profile/{id}/new-nonce	RFC 8555 §7.2	unauth	Returns 204 + Replay-Nonce header.
POST	/acme/profile/{id}/new-account	RFC 8555 §7.3	JWS jwk	Register a new account; idempotent re-registration of an existing JWK returns the existing row.
POST	/acme/profile/{id}/account/{acc_id}	RFC 8555 §7.3.2 + §7.3.6	JWS kid	Update contact list, deactivate, or POST-as-GET (RFC 8555 §6.3) to fetch the account.
POST	/acme/profile/{id}/new-order	RFC 8555 §7.4	JWS kid	Submit an order; identifier validation runs before order creation.
POST	/acme/profile/{id}/order/{ord_id}	RFC 8555 §7.4	JWS kid	POST-as-GET fetch of an order's current state.
POST	/acme/profile/{id}/order/{ord_id}/finalize	RFC 8555 §7.4	JWS kid	Submit the CSR + finalize. Issues + persists managed cert row + version.
POST	/acme/profile/{id}/authz/{authz_id}	RFC 8555 §7.5	JWS kid	POST-as-GET fetch of an authorization.
POST	/acme/profile/{id}/challenge/{chall_id}	RFC 8555 §7.5.1	JWS kid	Submit a challenge for validation. Dispatches to a bounded-concurrency worker pool; clients poll authz for the eventual result.
POST	/acme/profile/{id}/cert/{cert_id}	RFC 8555 §7.4.2	JWS kid	POST-as-GET cert chain download (PEM).
GET	/acme/directory	RFC 8555 §7.1.1	unauth	Shorthand path; mirrors per-profile when CERTCTL_ACME_SERVER_DEFAULT_PROFILE_ID is set.
HEAD	/acme/new-nonce	RFC 8555 §7.2	unauth	Shorthand.
GET	/acme/new-nonce	RFC 8555 §7.2	unauth	Shorthand.
POST	/acme/new-account	RFC 8555 §7.3	JWS jwk	Shorthand.
POST	/acme/account/{acc_id}	RFC 8555 §7.3.2 + §7.3.6	JWS kid	Shorthand.
POST	/acme/new-order	RFC 8555 §7.4	JWS kid	Shorthand.
POST	/acme/order/{ord_id}	RFC 8555 §7.4	JWS kid	Shorthand.
POST	/acme/order/{ord_id}/finalize	RFC 8555 §7.4	JWS kid	Shorthand.
POST	/acme/authz/{authz_id}	RFC 8555 §7.5	JWS kid	Shorthand.
POST	/acme/cert/{cert_id}	RFC 8555 §7.4.2	JWS kid	Shorthand.

The remaining RFC 8555 endpoints (challenge/{id}, key-change, revoke-cert, renewal-info) are advertised in the directory document but not yet served — clients hitting them get a 404 until subsequent phases land. The directory document includes their URLs because RFC 8555 doesn't permit a partial directory.

Finalize routing through CertificateService.Create (Phase 2 architecture)

The finalize path mirrors how every other certctl issuance surface (EST, SCEP, agent, REST API) routes through the canonical pipeline:

1. JWS-verify the request (internal/api/acme/jws.go).
2. Validate the CSR's DNS-name set equals the order's identifier set exactly (case-folded). Mismatches return RFC 8555 urn:ietf:params:acme:error:badCSR.
3. Update the order row to status=processing (s.tx.WithinTx + auditService.RecordEventWithTx — atomic with audit row).
4. Issue the cert via the bound profile's IssuerConnector adapter (same IssueCertificate(ctx, commonName, sans, csrPEM, ekus, maxTTLSeconds, mustStaple) call EST/SCEP/agent take).
5. Insert the managed_certificates row via service.CertificateService.Create(ctx, *ManagedCertificate, actor). Source is stamped domain.CertificateSourceACME so operators can bulk-revoke ACME-issued certs by filtering on Source=ACME.
6. Insert the certificate_versions row + transition the order to status=valid with certificate_id set (one final WithinTx covering both writes + the audit row).

This means RenewalPolicy, CertificateProfile, per-issuer-type Prometheus metrics, audit rows, and revocation-pipeline integration all apply uniformly to ACME-issued certs via the same code path that already serves EST/SCEP/agent/REST issuance.

The atomicity boundary: there is a brief window between step 5 (cert exists) and step 6 (order shows valid) where the order row still says processing. Phase 5's GC scheduler reconciles. The actor string on audit rows is acme:<account-id>.

JWS verification (Phase 1b)

Every JWS-authenticated POST runs through the verifier at internal/api/acme/jws.go::VerifyJWS. The verifier enforces:

1. The JWS parses as a flattened single-signature object (multi-sig is rejected per RFC 8555 §6.2).
2. The signature algorithm is in the closed allow-list {RS256, ES256, EdDSA} per RFC 8555 §6.2 — none, HS256, and every other alg are refused at parse time.
3. The protected header carries exactly one of kid (registered account) or jwk (new-account flow); endpoints declare which they require.
4. The protected header url matches the inbound request URL exactly.
5. The protected header nonce is consumed against the acme_nonces store; missing / replayed / expired nonces return urn:ietf:params:acme:error:badNonce per RFC 8555 §6.5.1.
6. On the kid path: the kid URL round-trips against the canonical per-profile shape, the referenced account exists, and its status is valid. Deactivated / revoked accounts cannot authenticate.
7. The signature verifies against the resolved key (registered account's stored JWK on the kid path; embedded jwk on the jwk path).

Every state-mutating account operation (create, contact update, deactivate) writes its acme_accounts row and an audit_events row inside one repository.Transactor.WithinTx call — the canonical certctl atomicity contract (matches service.CertificateService.Create at internal/service/certificate.go:131).

Phases (cross-reference)

Phase	Status	Surface
1a	live	directory + new-nonce + per-profile routing
1b	live	new-account + account/{id} + JWS verifier (RFC 7515 + go-jose v4)
2	live	orders + authzs + finalize + cert download (trust_authenticated mode end-to-end)
3	live	HTTP-01 + DNS-01 + TLS-ALPN-01 challenge validation (challenge mode end-to-end)
4	not yet	key rollover + revocation + ARI (RFC 9773)
5	not yet	cert-manager integration test + production hardening
6	not yet	full operator-facing reference + walkthroughs + threat model

Track shipped phases via git log --grep='acme-server:' --oneline.

Operational notes (Phase 1a)

• Schema: migrations/000025_acme_server.up.sql adds 5 ACME tables

  • the certificate_profiles.acme_auth_mode column. Phase 1a actively uses only acme_nonces. The full schema ships now so the migration is stable and Phases 1b-4 don't need additional CREATE TABLE migrations.

• Replay protection: nonces are persisted in acme_nonces (NOT in-memory). They survive server restart, which is required for the RFC 8555 §6.5 replay defense to hold against a multi-replica certctl-server fleet behind a load balancer.

• Metrics: the service layer exposes per-op atomic counters via service.ACMEService.Metrics().Snapshot():

  • certctl_acme_directory_total
  • certctl_acme_directory_failures_total
  • certctl_acme_new_nonce_total
  • certctl_acme_new_nonce_failures_total

  Phase 1b will extend with new_account counters; Phase 2 with order / finalize / cert; Phase 3 with per-challenge-type counters.

• Audit: Phase 1a is read-mostly (directory + nonce). Phase 1b's account-creation path will route through the canonical s.tx.WithinTx(...) + auditService.RecordEventWithTx(...) pattern so every account state mutation is paired with an audit_events row.