P13-T03 — Google/Apple verification (sliced: T03A / T03B / T03C)

Status: T03A LOCAL_DONE on codex/phase-13-free-accounts (phase PR #27, draft). Issue: #24. The task spans protocol, persistence and transport, so it ships in three letter-suffixed slices with explicit acceptance below. One slice per atomic commit; issue #24 stays open until the phase PR merges.

Slice acceptance (frozen before coding)

• T03A — OIDC verifier core + JWKS sources + stub issuers + memory nonces (this commit): RS256/ES256 verification from stdlib crypto, frozen issuer allowlist, exact audience, expiry inside 120s skew, single-use nonces, unknown-kid rotation refusal, tamper/malformed refusal, outage fails closed, Apple relay binds the opaque subject, JWKS cache honors the 1h TTL, HTTPS-only fetch. Pure unit tests with stub-minted tokens.
• T03B — migration 000021 (provider_links, oidc_nonces) + link/ unlink application + pg stores + real-DB integration: happy link both providers, cross-account refusal, last-method unlink refusal, nonce replay across processes, JWKS rotation against DB-backed nonces.
• T03C — link/unlink transport with session auth + OpenAPI paths + sandbox evidence (stub-issuer protocol runs; live-provider contact stays deferred to P13-T05/G13 device evidence, recorded, never mocked green).

T03A what changed

• account/adapters/oidc/oidc.go — Verifier implementing the T01 domain.ProviderVerifier port: allowlist → token split → JWKS fetch → kid select → RS256/ES256 verify → iss/aud/expiry/nonce/sub checks → nonce consume. Stable ErrOIDC* codes incl. new oidc-nonce-mismatch (token bound to another login, not a replay).
• account/adapters/oidc/stub.go — StubIssuer minting RS256/ES256 keys and tokens for tests/local runs, with JWKS JSON rendering.
• account/adapters/oidc/jwks.go — CachedKeys (frozen 1h TTL), HTTPKeys (HTTPS-only, 5s timeout, 64 KiB cap), MemKeys, FailingKeys, ProductionJWKS endpoints, MemNonces.
• account/domain/ports.go — ErrOIDCNonceMismatch + verdict mapping.
• Tests: 8 suites (valid both algs, wrong iss/aud/exp + skew edge, nonce single-use + mismatch, unknown-kid rotation + tamper + malformed, outage closed, Apple relay subject, cache TTL, HTTPS fetch + refusals).

Validation (exact commands, this host)

cd backend && gofmt -l ./... && go vet ./internal/modules/account/... \
  && go test -count=1 ./internal/modules/account/...
make quick-verify
git diff --check

Outcome: 8/8 OIDC suites plus all account packages green; gofmt/vet clean; quick-verify ok; diff --check clean; secrets scan clean.

Limits (not claimed)

• No link/unlink persistence or endpoints (T03B/T03C); no live Google/ Apple contact anywhere — sandbox evidence lands in T03C against stubs, live-provider runs stay outstanding to device acceptance.
• Email remains display/relay only; merge-by-email stays refused by construction (no code path accepts it — enforced in T03B).

Rollback

Pure addition: deleting adapters/oidc/ restores prior behavior. No migration, no flag, no data.

Next

P13-T03B provider links + nonces persistence + real-DB integration (#24, same branch).