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fix(security,config): remove unimplemented JWT auth-type, close silent downgrade (G-1)

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The pre-G-1 config validator accepted CERTCTL_AUTH_TYPE=jwt and the
startup log faithfully echoed 'authentication enabled type=jwt'.
Reasonable people read that and concluded JWT auth was on. It wasn't.
The auth-middleware wiring at cmd/server/main.go unconditionally routed
every request through the api-key bearer middleware regardless of
cfg.Auth.Type. So CERTCTL_AUTH_TYPE=jwt quietly compared the incoming
'Authorization: Bearer <token>' against whatever string the operator put
in CERTCTL_AUTH_SECRET — real JWT clients got 401, and operators who
treated CERTCTL_AUTH_SECRET as a *signing* secret (because they thought
they were configuring JWT) had effectively handed an attacker an api-key.
A security finding masquerading as a config option.

We chose the audit-recommended structural fix: remove the option, fail
fast at startup, and add the gateway-fronting pattern as the documented
forward path. Implementing JWT middleware would have meant jwks vs
static-secret rotation, claim mapping, expiry enforcement, audience and
issuer validation, key rollover semantics, and regression coverage at the
same depth as the existing api-key path — a feature, not a fix. Operators
who genuinely need JWT/OIDC front certctl with an authenticating gateway
(oauth2-proxy / Envoy ext_authz / Traefik ForwardAuth / Pomerium /
Authelia) and run the upstream certctl with CERTCTL_AUTH_TYPE=none. Same
shape works on docker-compose and Helm.

The change is comprehensive across 7 phases — every surface that
mentioned 'jwt' as a certctl-auth-type is updated, plus structural
backstops (typed enum, runtime guard, helm template validation, CI grep
guard) so the lie can't reappear.

Files changed:

Phase 1 — production code (typed enum + jwt removal):
- internal/config/config.go: AuthType typed alias + AuthTypeAPIKey /
  AuthTypeNone constants + ValidAuthTypes() helper. Validate() routes
  literal 'jwt' through a dedicated multi-line diagnostic naming the
  authenticating-gateway pattern, then cross-checks against
  ValidAuthTypes(). Secret-required branch simplified to api-key-only.
  Field comment on AuthConfig.Type rewritten to drop jwt and point at
  the gateway pattern.
- internal/api/middleware/middleware.go: AuthConfig.Type field comment
  references the typed config.AuthType constants.
- internal/api/handler/health.go: same treatment for HealthHandler.AuthType.
- cmd/server/main.go: defense-in-depth runtime switch immediately after
  config.Load() — exits 1 on any unsupported auth-type that bypassed the
  validator. Auth-disabled startup log explicitly names the
  authenticating-gateway pattern.

Phase 2 — tests (Red→Green, contract pinning):
- internal/config/config_test.go: TestValidate_JWTAuth_RejectedDedicated
  (two table rows pinning the dedicated G-1 error fires regardless of
  whether Secret is set), TestValidAuthTypesDoesNotContainJWT (property
  guard against future re-introduction),
  TestValidAuthTypesIsExactly_APIKey_None (allowed-set contract),
  TestValidate_GenericInvalidAuthType (pins non-jwt invalid values still
  hit the generic invalid-auth-type error). Removed the prior
  TestValidate_JWTAuth_MissingSecret happy-path since its premise is
  inverted post-G-1.
- internal/api/handler/health_test.go: removed
  TestAuthInfo_ReturnsAuthType_JWT (which baked the silent-downgrade lie
  into the regression suite). Pre-existing _APIKey test continues to
  cover the api-key happy path.

Phase 3 — spec, docs, env templates:
- api/openapi.yaml: auth_type enum dropped to [api-key, none] with
  inline comment naming the G-1 closure.
- .env.example (root): CERTCTL_AUTH_TYPE comment block rewritten to drop
  jwt and point at the gateway pattern; secret-required conditional
  simplified to api-key-only.
- docs/architecture.md: middleware-stack bullet rewritten to drop the
  JWT mention; new H3 'Authenticating-gateway pattern (JWT, OIDC, mTLS)'
  section explaining the design rationale and listing oauth2-proxy /
  Envoy ext_authz / Traefik ForwardAuth / Pomerium / Authelia / Caddy
  forward_auth / Apache mod_auth_openidc / nginx auth_request as the
  standard fronting options.
- docs/upgrade-to-v2-jwt-removal.md (new ~125 lines): migration guide
  with preconditions, what-changes, both recovery paths, complete
  docker-compose oauth2-proxy walkthrough, Traefik ForwardAuth and Envoy
  ext_authz patterns, rollback posture.

Phase 4 — Helm chart (template validation + docs):
- deploy/helm/certctl/templates/_helpers.tpl: new certctl.validateAuthType
  helper mirroring the existing certctl.tls.required pattern. Fails
  template render on any server.auth.type outside {api-key, none} with
  a multi-line diagnostic.
- deploy/helm/certctl/templates/server-deployment.yaml,
  server-configmap.yaml, server-secret.yaml: invoke the helper at the
  top of each template that depends on .Values.server.auth.type.
- deploy/helm/certctl/values.yaml: auth: block comment expanded with the
  G-1 rationale and gateway-pattern cross-reference.
- deploy/helm/CHART_SUMMARY.md: server.auth.type table row now surfaces
  the allowed set and points at the upgrade doc.
- deploy/helm/certctl/README.md: new 'JWT / OIDC via authenticating
  gateway' section with a Kubernetes-flavored oauth2-proxy + certctl
  walkthrough.

Phase 5 — release surface:
- CHANGELOG.md: new [unreleased] top entry with Breaking / Removed /
  Added / Changed sections; explicit pointer at
  docs/upgrade-to-v2-jwt-removal.md from the Breaking subsection.

Phase 6 — CI guardrail:
- .github/workflows/ci.yml: new 'Forbidden auth-type literal regression
  guard (G-1)' step. Scoped patterns catch the actual regression shapes
  (map literal, slice literal, switch case, OpenAPI enum, env-file
  default, AuthType('jwt') cast). Comments and the dedicated rejection
  branch are intentionally exempt; connector-package JWT references
  (Google OAuth2 / step-ca) are exempt as out-of-scope external
  protocols. Verified locally: the guard passes on the actual tree and
  fires on all 4 synthetic regression patterns.

Out of scope (explicitly untouched):
- internal/connector/discovery/gcpsm/gcpsm.go — Google OAuth2 service-
  account JWT (external protocol).
- internal/connector/issuer/googlecas/googlecas.go — same.
- internal/connector/issuer/stepca/stepca.go — step-ca's provisioner
  one-time-token JWT for /sign API.
- docs/test-env.md, docs/connectors.md, docs/features.md — describe
  external CAs' use of JWT, not certctl's auth shape.
- Implementing actual JWT middleware. Feature, not a fix.

Verification (all gates pass):
- go build ./... — clean
- go vet ./... — clean
- go test -short ./... — every package green
- go test -short -race ./internal/config/... ./internal/api/... — clean
- govulncheck ./... — no vulnerabilities in our code
- helm lint deploy/helm/certctl/ — clean
- helm template with auth.type=api-key — renders OK
- helm template with auth.type=none — renders OK
- helm template with auth.type=jwt — fails with validateAuthType
  diagnostic (exit 1)
- python3 yaml.safe_load on api/openapi.yaml — parses
- CI guardrail mirror — clean on real tree, fires on all 4 synthetic
  regression patterns
- Smoke test: 'CERTCTL_AUTH_TYPE=jwt ./certctl-server' exits non-zero
  with: 'Failed to load configuration: CERTCTL_AUTH_TYPE=jwt is no
  longer accepted (G-1 silent auth downgrade): no JWT middleware ships
  with certctl. To use JWT/OIDC, run an authenticating gateway
  (oauth2-proxy / Envoy ext_authz / Traefik ForwardAuth / Pomerium) in
  front of certctl and set CERTCTL_AUTH_TYPE=none on the upstream.
  See docs/architecture.md "Authenticating-gateway pattern" and
  docs/upgrade-to-v2-jwt-removal.md for the migration walkthrough'

config pkg coverage: ValidAuthTypes 100%, Validate 94.7%, total 75.5%.

Refs: coverage-gap-audit-2026-04-24-v5/unified-audit.md
      §2 P1 cluster, cat-g-jwt_silent_auth_downgrade
      Audit recommendation followed verbatim: 'Remove jwt from
      validAuthTypes until middleware ships'.
This commit is contained in:
shankar0123
2026-04-25 00:22:23 +00:00
parent 3192cd15c5
commit 9c1d446e40
19 changed files with 629 additions and 65 deletions
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CHANGELOG.md
+35
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@@ -2,6 +2,41 @@
All notable changes to certctl are documented in this file. Dates use ISO 8601. Versions follow [Semantic Versioning](https://semver.org/).
## [unreleased] — 2026-04-24
### G-1: JWT silent auth downgrade — closed end-to-end
> Pre-G-1 the config validator accepted `CERTCTL_AUTH_TYPE=jwt` and the startup log faithfully echoed `"authentication enabled" "type"="jwt"`. Reasonable people read that and concluded JWT was on. It wasn't. The auth-middleware wiring at `cmd/server/main.go` unconditionally routed every request through the api-key bearer middleware regardless of `cfg.Auth.Type`. So `CERTCTL_AUTH_TYPE=jwt` quietly compared incoming `Authorization: Bearer <something>` against whatever string the operator put in `CERTCTL_AUTH_SECRET` — real JWT clients got 401, and operators who treated `CERTCTL_AUTH_SECRET` as a *signing* secret (because they thought they were configuring JWT) had effectively handed an attacker an api-key. A security finding masquerading as a config option. We chose to remove the option rather than ship JWT middleware — the audit-recommended structural fix that closes the hazard. Operators who actually need JWT/OIDC front certctl with an authenticating gateway (oauth2-proxy / Envoy `ext_authz` / Traefik `ForwardAuth` / Pomerium / Authelia) and run the upstream certctl with `CERTCTL_AUTH_TYPE=none`. The same pattern works on docker-compose and Helm.
### Breaking Changes
- **`CERTCTL_AUTH_TYPE=jwt` is no longer accepted.** Pre-G-1 the value was silently downgraded to api-key middleware. Post-G-1 the server fails at startup with a dedicated diagnostic naming the authenticating-gateway pattern. Operators with this in their env block must either switch to `api-key` (if they were de facto using api-key auth all along — same Bearer token continues to work) or switch to `none` and front certctl with an oauth2-proxy / Envoy / Traefik / Pomerium gateway. See [`docs/upgrade-to-v2-jwt-removal.md`](docs/upgrade-to-v2-jwt-removal.md).
- **Helm chart `server.auth.type=jwt` now fails at `helm install` / `helm upgrade` template time.** New `certctl.validateAuthType` template helper runs on every template that depends on `.Values.server.auth.type` (`server-deployment.yaml`, `server-configmap.yaml`, `server-secret.yaml`) and fails the render with a pointer at the gateway-fronting pattern.
- **OpenAPI spec `auth_type` enum no longer includes `jwt`.** API consumers checking `/api/v1/auth/info` against the spec will see a smaller enum.
### Removed
- Documented references to JWT in the certctl auth surface (config docblocks, middleware/health-handler comments, `.env.example`, `docs/architecture.md` middleware-stack bullet). Connector-level JWT references (Google OAuth2 service-account JWT in `internal/connector/discovery/gcpsm/`, `internal/connector/issuer/googlecas/`; step-ca's provisioner one-time-token JWT in `internal/connector/issuer/stepca/`) are unrelated and untouched — those are external-protocol uses, not certctl's own auth shape.
### Added
- **`config.AuthType` typed alias** with `AuthTypeAPIKey` / `AuthTypeNone` exported constants. Single source of truth for the allowed set across the validator, the runtime defense-in-depth switch in `main.go`, and the helm chart's `validateAuthType` helper.
- **`config.ValidAuthTypes()`** helper returning the complete allowed set; pinned by a property test (`TestValidAuthTypesDoesNotContainJWT`) that fails the build if `"jwt"` is ever re-added to the slice.
- **Defense-in-depth runtime guard** in `cmd/server/main.go` immediately after `config.Load()` — a `switch config.AuthType(cfg.Auth.Type)` that exits 1 if the validator was bypassed (test harness, alt config loader, env-var rebinding).
- **`certctl.validateAuthType` Helm template helper** mirroring the existing `certctl.tls.required` pattern. Fails template render on any `server.auth.type` outside `{api-key, none}`.
- **`docs/architecture.md` "Authenticating-gateway pattern (JWT, OIDC, mTLS)"** section explaining the design rationale for the narrow in-process auth surface and listing oauth2-proxy / Envoy `ext_authz` / Traefik `ForwardAuth` / Pomerium / Authelia / Caddy `forward_auth` / Apache `mod_auth_openidc` / nginx `auth_request` as the standard fronting options.
- **`docs/upgrade-to-v2-jwt-removal.md`** migration guide. Same shape as `docs/upgrade-to-tls.md`. Walks through the dedicated startup error, both recovery paths (`api-key` vs gateway-fronting), a complete docker-compose oauth2-proxy walkthrough, Traefik ForwardAuth and Envoy `ext_authz` patterns, and rollback posture.
- **`deploy/helm/certctl/README.md`** "JWT / OIDC via authenticating gateway" section with a Kubernetes-flavored oauth2-proxy + certctl walkthrough.
- **CI regression guardrail** in `.github/workflows/ci.yml` (`Forbidden auth-type literal regression guard (G-1)`) — grep-fails the build if `"jwt"` appears as an auth-type literal in production code or spec. Connector packages exempt (legitimate external-protocol uses).
- **Negative test coverage** in `internal/config/config_test.go`: `TestValidate_JWTAuth_RejectedDedicated` (two table rows pinning that the dedicated G-1 error fires regardless of whether `Secret` is set), `TestValidAuthTypesDoesNotContainJWT` (property-level guard), `TestValidAuthTypesIsExactly_APIKey_None` (allowed-set contract), `TestValidate_GenericInvalidAuthType` (pins that other invalid values still surface the generic invalid-auth-type error, so the dedicated G-1 path doesn't accidentally swallow non-jwt typos).
### Changed
- `internal/api/middleware/middleware.go::AuthConfig.Type` field comment now references the typed `config.AuthType` constants instead of an inline string enumeration.
- `internal/api/handler/health.go::HealthHandler.AuthType` field comment same treatment.
- `internal/api/handler/health_test.go` — the prior `TestAuthInfo_ReturnsAuthType_JWT` (which asserted the handler echoed `"jwt"`, baking the silent-downgrade lie into the regression suite) is removed; the pre-existing `TestAuthInfo_ReturnsAuthType_APIKey` continues to cover the api-key happy path.
- Auth-disabled startup log in `main.go` now points operators at the authenticating-gateway pattern explicitly.
## [2.2.0] — 2026-04-19
### HTTPS Everywhere — The Irony