security: harden data auth and deployment

backend/app/secret_storage.py

@@ -0,0 +1,74 @@
+import base64
+import hashlib
+from typing import Optional
+
+from cryptography.fernet import Fernet, InvalidToken
+
+from .config import settings
+
+
+ENCRYPTED_PREFIX = "enc:v1:"
+SENSITIVE_SETTING_KEYS = frozenset(
+    {
+        "jellystat_api_key", "magent_ssl_certificate_pem", "magent_ssl_private_key_pem",
+        "magent_notify_email_smtp_password", "magent_notify_discord_webhook_url",
+        "magent_notify_telegram_bot_token", "magent_notify_push_token",
+        "magent_notify_push_user_key", "magent_notify_webhook_url", "jellyseerr_api_key",
+        "jellyfin_api_key", "sonarr_api_key", "radarr_api_key", "bazarr_api_key",
+        "prowlarr_api_key", "qbittorrent_password",
+    }
+)
+
+
+def _fernet_key() -> bytes:
+    configured = str(settings.settings_encryption_key or "").strip()
+    if configured:
+        try:
+            decoded = base64.urlsafe_b64decode(configured.encode("ascii"))
+        except Exception as exc:
+            raise RuntimeError("SETTINGS_ENCRYPTION_KEY must be a valid Fernet key") from exc
+        if len(decoded) != 32:
+            raise RuntimeError("SETTINGS_ENCRYPTION_KEY must decode to exactly 32 bytes")
+        return configured.encode("ascii")
+    jwt_secret = str(settings.jwt_secret or "").strip()
+    if len(jwt_secret) < 32 or jwt_secret == "change-me":
+        raise RuntimeError(
+            "SETTINGS_ENCRYPTION_KEY is required when JWT_SECRET is not a strong migration key"
+        )
+    derived = hashlib.sha256(("magent-settings-v1:" + jwt_secret).encode("utf-8")).digest()
+    return base64.urlsafe_b64encode(derived)
+
+
+def is_sensitive_setting(key: str) -> bool:
+    return str(key or "").strip().lower() in SENSITIVE_SETTING_KEYS
+
+
+def validate_secret_storage_configuration() -> None:
+    """Validate the configured or JWT-derived Fernet key without touching stored data."""
+    Fernet(_fernet_key())
+
+
+def encrypt_setting_value(key: str, value: Optional[str]) -> Optional[str]:
+    if value is None or not is_sensitive_setting(key):
+        return value
+    text = str(value)
+    if text.startswith(ENCRYPTED_PREFIX):
+        return text
+    token = Fernet(_fernet_key()).encrypt(text.encode("utf-8")).decode("ascii")
+    return ENCRYPTED_PREFIX + token
+
+
+def decrypt_setting_value(key: str, value: Optional[str]) -> Optional[str]:
+    if value is None or not is_sensitive_setting(key):
+        return value
+    text = str(value)
+    if not text.startswith(ENCRYPTED_PREFIX):
+        return text
+    try:
+        return Fernet(_fernet_key()).decrypt(
+            text[len(ENCRYPTED_PREFIX) :].encode("ascii")
+        ).decode("utf-8")
+    except InvalidToken as exc:
+        raise RuntimeError(
+            f"Stored secret '{key}' cannot be decrypted with the configured key"
+        ) from exc