fix: harden token pools and CPA export

cpa_xai/writer.py

@@ -8,13 +8,24 @@ from pathlib import Path
 from .schema import credential_file_name
 
 
+def _is_relative_to(path, root):
+    try:
+        path.relative_to(root)
+        return True
+    except ValueError:
+        return False
+
+
 def write_cpa_xai_auth(auth_dir, payload, filename=None):
     root = Path(auth_dir).expanduser().resolve()
     root.mkdir(parents=True, exist_ok=True)
     target_name = filename or credential_file_name(payload.get("email", ""), payload.get("sub", ""))
+    target_name = Path(str(target_name)).name
     if not str(target_name).endswith(".json"):
         target_name = str(target_name) + ".json"
-    destination = root / str(target_name)
+    destination = (root / str(target_name)).resolve()
+    if not _is_relative_to(destination, root):
+        raise ValueError("CPA auth filename must stay inside auth_dir")
     data = json.dumps(payload, indent=2, ensure_ascii=False) + "\n"
     file_descriptor, temp_name = tempfile.mkstemp(prefix=".xai-", suffix=".tmp", dir=str(root))
     try: