Harden local secrets and backup restore

nouri/backup.py

@@ -77,6 +77,7 @@ def export_backup_archive(
 
 def _extract_uploads_to_temp(archive: zipfile.ZipFile) -> Path:
     temp_dir = Path(tempfile.mkdtemp(prefix="nouri-restore-uploads-"))
+    temp_root = temp_dir.resolve()
     for member in archive.infolist():
         if not member.filename.startswith("uploads/") or member.is_dir():
             continue
@@ -84,8 +85,11 @@ def _extract_uploads_to_temp(archive: zipfile.ZipFile) -> Path:
         if not relative_target:
             continue
         target_path = temp_dir / relative_target
+        resolved_target = target_path.resolve()
+        if not resolved_target.is_relative_to(temp_root):
+            raise ValueError("Das Backup enthält einen ungültigen Upload-Pfad.")
         target_path.parent.mkdir(parents=True, exist_ok=True)
-        with archive.open(member, "r") as source, target_path.open("wb") as destination:
+        with archive.open(member, "r") as source, resolved_target.open("wb") as destination:
             shutil.copyfileobj(source, destination)
     return temp_dir