feat: import F95 covers using personal encrypted sessions

backend/app/f95_session.py

@@ -0,0 +1,29 @@
+"""Encrypted, user-bound storage for third-party credentials."""
+import base64
+import hashlib
+import json
+
+from cryptography.fernet import Fernet, InvalidToken
+
+from app.config import get_settings
+
+
+def _cipher() -> Fernet:
+    key = hashlib.sha256(("f95-session:" + get_settings().secret_key).encode()).digest()
+    return Fernet(base64.urlsafe_b64encode(key))
+
+
+def seal(user_id: int, cookie: str, user_agent: str) -> str:
+    data = json.dumps({"user_id": user_id, "cookie": cookie, "user_agent": user_agent})
+    return _cipher().encrypt(data.encode()).decode()
+
+
+def open_session(user_id: int, token: str | None) -> tuple[str, str]:
+    if token:
+        try:
+            data = json.loads(_cipher().decrypt(token.encode()))
+            if data["user_id"] == user_id:
+                return data["cookie"], data["user_agent"]
+        except (InvalidToken, ValueError, KeyError, TypeError):
+            pass
+    return "", ""