feat(#28): Gate B [08/10]: AES-GCM settings round-trip (AES-1, AES-2)

- AES-GCM encrypt/decrypt module (app/security/aes.py): - get_aes_key: decode base64 AES master key to 32 bytes - encrypt_setting: AES-256-GCM with fresh 12-byte nonce per call, returns nonce||ciphertext - decrypt_setting: decrypts ciphertext, raises AuthenticationError on tamper/wrong key - Settings endpoint (app/api/settings.py): - GET /api/v1/settings: returns SettingsView with decrypted values, secrets masked (woo_app_password never returned, only woo_credentials_configured boolean) - PUT /api/v1/settings: encrypts all setting values AES-GCM, stores in settings table - Rejects woo_consumer_key/woo_consumer_secret fields - Validates woo_create_status (draft|publish) - App factory (app/main.py): stores settings on app.state for dependency injection - Unit tests (tests/unit/test_aes.py): 18 tests covering AES-1 (round-trip), AES-2 (missing key refusal), FUND-17 (fresh nonce, tamper rejection), FUND-19 (no plaintext fallback) Test results: 23/23 passed (18 new AES + 5 existing health tests)
2026-09-07 08:00:29 +00:00
parent e5514fe3bf
commit 82219fe5ad
5 changed files with 526 additions and 7 deletions
@@ -0,0 +1,196 @@
+"""AES-GCM settings encryption unit tests.
+
+AES-1: Encrypt then decrypt round-trips for woo_wp_username and woo_app_password;
+        ciphertext never appears in GET settings.
+AES-2: Missing SLAB_AES_KEY environment variable at startup: app refuses to start;
+        no fallback to plaintext.
+
+FUND-17: Fresh nonce per encrypt; tampered ciphertext raises authentication failure.
+FUND-18: Ciphertext never appears in any GET response.
+FUND-19: Missing SLAB_AES_KEY refuses startup; no fallback to plaintext storage.
+"""
+
+import pytest
+
+from app.security.aes import (
+    AuthenticationError,
+    decrypt_setting,
+    encrypt_setting,
+    get_aes_key,
+)
+
+
+class TestAESRoundTrip:
+    """AES-1: Encrypt then decrypt round-trip for woo_wp_username and woo_app_password."""
+
+    @pytest.fixture
+    def aes_key_bytes(self) -> bytes:
+        """Test AES key (32 bytes)."""
+        return get_aes_key("dGVzdC1rZXktZm9yLW1hbGxlb3AtdGVzdGluZy1vbmx5LXNob3VsZC1iZS11c2Vk")
+
+    def test_roundtrip_username(self, aes_key_bytes: bytes) -> None:
+        """AES-1: Encrypt and decrypt woo_wp_username round-trips."""
+        plaintext = "slab-uploader"
+        ciphertext = encrypt_setting(aes_key_bytes, plaintext)
+        decrypted = decrypt_setting(aes_key_bytes, ciphertext)
+        assert decrypted == plaintext
+
+    def test_roundtrip_password(self, aes_key_bytes: bytes) -> None:
+        """AES-1: Encrypt and decrypt woo_app_password round-trips."""
+        plaintext = "W00rdP@ssw0rd!2026"
+        ciphertext = encrypt_setting(aes_key_bytes, plaintext)
+        decrypted = decrypt_setting(aes_key_bytes, ciphertext)
+        assert decrypted == plaintext
+
+    def test_roundtrip_empty_string(self, aes_key_bytes: bytes) -> None:
+        """AES-1: Empty string encrypts and decrypts correctly."""
+        plaintext = ""
+        ciphertext = encrypt_setting(aes_key_bytes, plaintext)
+        decrypted = decrypt_setting(aes_key_bytes, ciphertext)
+        assert decrypted == plaintext
+
+    def test_roundtrip_unicode(self, aes_key_bytes: bytes) -> None:
+        """AES-1: Unicode plaintext round-trips."""
+        plaintext = "тест-ключ-пароль"
+        ciphertext = encrypt_setting(aes_key_bytes, plaintext)
+        decrypted = decrypt_setting(aes_key_bytes, ciphertext)
+        assert decrypted == plaintext
+
+    def test_roundtrip_special_chars(self, aes_key_bytes: bytes) -> None:
+        """AES-1: Special characters in plaintext round-trip."""
+        plaintext = '!@#$%^&*()_+-={}[]|:;<>?/~`'
+        ciphertext = encrypt_setting(aes_key_bytes, plaintext)
+        decrypted = decrypt_setting(aes_key_bytes, ciphertext)
+        assert decrypted == plaintext
+
+    def test_ciphertext_is_bytes(self, aes_key_bytes: bytes) -> None:
+        """AES-1: encrypt_setting returns bytes."""
+        plaintext = "test-password"
+        ciphertext = encrypt_setting(aes_key_bytes, plaintext)
+        assert isinstance(ciphertext, bytes)
+
+    def test_ciphertext_starts_with_nonce(self, aes_key_bytes: bytes) -> None:
+        """AES-1: Ciphertext starts with 12-byte nonce."""
+        plaintext = "test-password"
+        ciphertext = encrypt_setting(aes_key_bytes, plaintext)
+        assert len(ciphertext) >= 12
+        nonce = ciphertext[:12]
+        assert len(nonce) == 12
+
+    def test_ciphertext_different_from_plaintext(self, aes_key_bytes: bytes) -> None:
+        """AES-1: Ciphertext is not the plaintext."""
+        plaintext = "secret"
+        ciphertext = encrypt_setting(aes_key_bytes, plaintext)
+        assert ciphertext != plaintext.encode("utf-8")
+
+    def test_ciphertext_changes_each_call(self, aes_key_bytes: bytes) -> None:
+        """AES-1: Ciphertext changes on each encrypt call (different nonce+IV)."""
+        plaintext = "same-plaintext"
+        ct1 = encrypt_setting(aes_key_bytes, plaintext)
+        ct2 = encrypt_setting(aes_key_bytes, plaintext)
+        assert ct1 != ct2
+
+
+class TestFreshNonce:
+    """FUND-17: Fresh nonce per encrypt; nonces differ between calls."""
+
+    @pytest.fixture
+    def aes_key_bytes(self) -> bytes:
+        return get_aes_key("dGVzdC1rZXktZm9yLW1hbGxlb3AtdGVzdGluZy1vbmx5LXNob3VsZC1iZS11c2Vk")
+
+    def test_nonce_differs_across_encryptions(self, aes_key_bytes: bytes) -> None:
+        """FUND-17: Encrypting the same plaintext twice produces different nonces."""
+        plaintext = "repeated-plaintext"
+        ct1 = encrypt_setting(aes_key_bytes, plaintext)
+        ct2 = encrypt_setting(aes_key_bytes, plaintext)
+        nonce1 = ct1[:12]
+        nonce2 = ct2[:12]
+        assert nonce1 != nonce2
+
+    def test_multiple_encryptions_all_unique_nonces(self, aes_key_bytes: bytes) -> None:
+        """FUND-17: Multiple encryptions all have unique nonces."""
+        nonces = []
+        for _ in range(5):
+            ct = encrypt_setting(aes_key_bytes, "test")
+            nonces.append(ct[:12])
+        assert len(set(nonces)) == 5
+
+
+class TestTamperedCiphertext:
+    """FUND-17: Tampered ciphertext raises authentication failure."""
+
+    @pytest.fixture
+    def aes_key_bytes(self) -> bytes:
+        return get_aes_key("dGVzdC1rZXktZm9yLW1hbGxlb3AtdGVzdGluZy1vbmx5LXNob3VsZC1iZS11c2Vk")
+
+    def test_tampered_body_raises_authentication_error(self, aes_key_bytes: bytes) -> None:
+        """FUND-17: Tampering with ciphertext body raises AuthenticationError."""
+        plaintext = "tamper-me"
+        ciphertext = encrypt_setting(aes_key_bytes, plaintext)
+        tampered = bytearray(ciphertext)
+        # Flip a byte in the ciphertext portion (after nonce)
+        if len(tampered) > 12:
+            tampered[12] ^= 0xFF
+        else:
+            tampered[0] ^= 0xFF
+        tampered_ct = bytes(tampered)
+
+        with pytest.raises(AuthenticationError):
+            decrypt_setting(aes_key_bytes, tampered_ct)
+
+    def test_truncated_ciphertext_raises_error(self, aes_key_bytes: bytes) -> None:
+        """FUND-17: Truncated ciphertext raises authentication error."""
+        plaintext = "truncate-me"
+        ciphertext = encrypt_setting(aes_key_bytes, plaintext)
+        truncated = ciphertext[:-4]
+
+        with pytest.raises(AuthenticationError):
+            decrypt_setting(aes_key_bytes, truncated)
+
+    def test_wrong_key_raises_error(self, aes_key_bytes: bytes) -> None:
+        """FUND-17: Decrypting with wrong key raises authentication error."""
+        wrong_key = get_aes_key("d3JvbmdrZXlmb3J0ZXN0aW5nc3lzdGVtY2hldmkgdGhpc2tleWlzYmFk")
+        plaintext = "wrong-key-test"
+        ciphertext = encrypt_setting(aes_key_bytes, plaintext)
+
+        with pytest.raises(AuthenticationError):
+            decrypt_setting(wrong_key, ciphertext)
+
+
+class TestMissingKey:
+    """AES-2: Missing SLAB_AES_KEY environment variable at startup."""
+
+    def test_missing_key_refuses_startup(self, monkeypatch: pytest.MonkeyPatch) -> None:
+        """AES-2: App refuses to start when SLAB_AES_KEY is missing."""
+        monkeypatch.delenv("SLAB_AES_KEY", raising=False)
+        from app.config import Settings
+        settings = Settings()
+        with pytest.raises(ValueError, match="SLAB_AES_KEY"):
+            settings.validate()
+
+    def test_too_short_key_refuses_startup(self, monkeypatch: pytest.MonkeyPatch) -> None:
+        """AES-2: Too-short key refuses startup."""
+        monkeypatch.setenv("SLAB_AES_KEY", "d290")  # "wot" = too short
+        from app.config import Settings
+        settings = Settings()
+        with pytest.raises(ValueError, match="at least 32 bytes"):
+            settings.validate()
+
+    def test_get_aes_key_returns_bytes(self) -> None:
+        """AES-2: get_aes_key returns bytes from base64 env var."""
+        settings = get_aes_key("dGVzdC1rZXktZm9yLW1hbGxlb3AtdGVzdGluZy1vbmx5LXNob3VsZC1iZS11c2Vk")
+        assert isinstance(settings, bytes)
+        assert len(settings) == 32
+
+
+class TestNoPlaintextFallback:
+    """AES-2: No fallback to plaintext storage."""
+
+    def test_decrypt_returns_decrypted_value(self) -> None:
+        """AES-2: No plaintext fallback; decrypt returns decrypted value, not raw storage."""
+        key = get_aes_key("dGVzdC1rZXktZm9yLW1hbGxlb3AtdGVzdGluZy1vbmx5LXNob3VsZC1iZS11c2Vk")
+        plaintext = "test-password"
+        ct = encrypt_setting(key, plaintext)
+        result = decrypt_setting(key, ct)
+        # Should return the original plaintext, not some fallback
+        assert result == plaintext