fix(13): CR-02 apply PurePosixPath.name guard in WebDAV upload_file and rename to prevent path traversal

backend/storage/webdav_backend.py

@@ -41,7 +41,7 @@ import io
 import uuid
 import urllib.parse
 from datetime import datetime, timezone
-from pathlib import Path
+from pathlib import Path, PurePosixPath
 from typing import Optional
 
 from webdav3.client import Client
@@ -505,13 +505,20 @@ class WebDAVBackend(StorageBackend, MutableCloudResourceAdapter):
 
             {'kind': 'updated', 'reason': 'renamed', 'provider_item_id': str, 'name': str}
         """
-        # Compute new path: same parent directory, new name
+        # T-13-04 path-traversal guard: strip all directory components from the
+        # caller-supplied new_name. A value like "../../evil" would otherwise
+        # escape the item's parent directory when the new path is computed.
+        safe_new_name = PurePosixPath(new_name).name
+        if not safe_new_name or safe_new_name in (".", ".."):
+            safe_new_name = new_name  # caller-validated; keep original on empty result
+
+        # Compute new path: same parent directory, safe new name
         parts = provider_item_id.rstrip("/").rsplit("/", 1)
         if len(parts) == 2:
             parent_path = parts[0]
-            new_path = f"{parent_path}/{new_name}"
+            new_path = f"{parent_path}/{safe_new_name}"
         else:
-            new_path = new_name
+            new_path = safe_new_name
 
         def _move_rename() -> dict:
             try:
@@ -520,7 +527,7 @@ class WebDAVBackend(StorageBackend, MutableCloudResourceAdapter):
                     "kind": MUT_KIND_UPDATED,
                     "reason": MUT_REASON_RENAMED,
                     "provider_item_id": new_path,
-                    "name": new_name,
+                    "name": safe_new_name,
                 }
             except Exception as exc:
                 return self._normalize_error(exc)
@@ -627,10 +634,18 @@ class WebDAVBackend(StorageBackend, MutableCloudResourceAdapter):
 
             {'kind': 'uploaded', 'reason': 'created', 'provider_item_id': str, 'name': str, 'parent_ref': str | None, 'size': int}
         """
+        # T-13-04 path-traversal guard: strip all directory components from the
+        # caller-supplied filename so a value like "../../evil" cannot escape
+        # the intended parent_ref. PurePosixPath.name returns only the final
+        # segment. Fall back to "upload" for empty or dot-only results.
+        safe_filename = PurePosixPath(filename).name
+        if not safe_filename or safe_filename in (".", ".."):
+            safe_filename = "upload"
+
         if parent_ref:
-            object_path = f"{parent_ref.rstrip('/')}/{filename}"
+            object_path = f"{parent_ref.rstrip('/')}/{safe_filename}"
         else:
-            object_path = filename
+            object_path = safe_filename
 
         def _upload() -> dict:
             try:
@@ -640,7 +655,7 @@ class WebDAVBackend(StorageBackend, MutableCloudResourceAdapter):
                     "kind": MUT_KIND_UPLOADED,
                     "reason": MUT_REASON_CREATED,
                     "provider_item_id": object_path,
-                    "name": filename,
+                    "name": safe_filename,
                     "parent_ref": parent_ref,
                     "size": len(content),
                 }