feat(auth): JWT verification + OAuth CSRF + PKCE + secret redaction
Group B — auth-crate security hardening (post-audit Sonnet test-retest 2026-05-02).
kei-auth-apple:
- jwt.rs: full ES256 JWKS signature verification (jsonwebtoken crate);
validates iss == https://appleid.apple.com, aud == client_id, exp, iat;
decode_id_token_unverified is now cfg(test)-only.
Module docstring promised this since v0.1 — now actually implemented.
- claims.rs (new): IdTokenClaims + AudClaim extracted from jwt.rs.
- error.rs: JwtVerify, JwtDecode, MissingClaim variants.
- client.rs: client_secret_jwt: SecretString (was String); exchange_code accepts
code_verifier: Option<&str> for PKCE.
- provider.rs: verify() does CSRF expected_state ConstantTimeEq + JWT verification;
build_auth_url accepts state + verifier and emits PKCE code_challenge.
- tests/apple_smoke.rs + helpers/: 6 tests including malformed-JWT + non-Apple OAuth +
400-mapping + provider_verify_csrf_mismatch_rejected.
kei-auth-google:
- pkce.rs (new): pkce_challenge + url_encode (RFC 7636 §B.1 test vector covered).
- client.rs: client_secret: SecretString; exchange_code accepts code_verifier.
- provider.rs: verify() rejects on state mismatch; build_auth_url emits S256 challenge.
- tests/google_smoke.rs: 7 tests including CSRF mismatch.
kei-auth:
- main.rs: resolve_token() supports stdin (-) and KEI_AUTH_TOKEN env. Token positional
arg leaked via /proc/<pid>/cmdline + shell history; same fix that v0.14.1
applied to --key.
- main.rs::key(): hard fail if KEI_AUTH_KEY len < 32 bytes (mirror of magiclink).
- tokens.rs::verify(): query_row(...).optional()? instead of .ok() — DB errors now
propagate instead of being swallowed as "token unknown".
kei-runtime-core:
- secrets.rs (new, 81 LOC): SecretString newtype with redacted Debug + zeroize-on-Drop.
Required by every auth crate that holds secret material.
- traits/auth.rs: AuthChallenge::Password.password is now SecretString;
OAuthCode { state, expected_state }.
- error.rs: CsrfStateMismatch variant.
Test results: 48 passed; 0 failed across kei-auth, kei-auth-apple, kei-auth-google,
kei-auth-magiclink, kei-runtime-core. cargo check --workspace clean.
Findings consensus: Apple JWT unverified + OAuth state CSRF appeared in all 3
audit waves (Wave-1 + Wave-A + Wave-B); PKCE absence + secret-derive-Debug appeared
only in Wave-A retest, would have been missed by single-pass audit.
Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
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