T09 · Insecure Skill Coding Practices
- Location
download_organizer.py:31- Finding
Untrusted Backup Mappings Allow Arbitrary File Copy and Deletion
- Content
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Vulnerability Details
File Location:
download_organizer.py:31-34, 95-108
Vulnerability Type: Unvalidated file paths from a writable backup file
Risk Level: MediumVulnerable Code
python def load_backup(self): if self.backup_file.exists(): with open(self.backup_file, 'r', encoding='utf-8') as f: self.backup_data = json.load(f) return self.backup_datapython reverse_mappings = {v: k for k, v in backup.items()} count = 0 for new_str, old_str in reverse_mappings.items(): new_path = Path(new_str) old_path = Path(old_str) if new_path.exists() and not old_path.exists(): copy2(new_path, old_path) new_path.unlink() print(f"撤销: {new_path.name} -> {old_path.name}") count += 1Technical Analysis
The
undooperation treats every source and destination path in.download-organizer-backup.jsonas trusted. The code does not validate the JSON schema, canonicalize and constrain paths to approved directories, reject symbolic links, or verify that each mapping was created by a previous legitimate organization operation.During undo, the JSON mapping is reversed. An attacker-controlled mapping can therefore select any existing path as
new_pathand any absent path asold_path. If the process has sufficient permissions,copy2(new_path, old_path)copies the selected source to the attacker-chosen destination, after whichnew_path.unlink()deletes the source.The
old_path.exists()check limits straightforward replacement of an existing destination but does not prevent creation at an arbitrary absent path. It also introduces a time-of-check/time-of-use window because the destination is checked separately from the subsequent copy operation.Attack Path
- The attacker gains write access to the output directory or plants/modifies
.download-organizer-backup.json. - The attacker inserts a JSON mapping whose key is an arbitrary desired restoration destina ...[truncated 1144 chars]
- The attacker gains write access to the output directory or plants/modifies
- Remediation
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Remediation Suggestions
- Store only normalized relative paths in the backup rather than unrestricted absolute paths.
- Resolve every source and destination using
Path.resolve()and require them to remain under explicitly configured input and output roots. - Reject mappings containing traversal components, unexpected value types, or paths outside the authorized roots.
- Define and enforce a strict JSON schema before processing any mappings.
- Reject symbolic links in the backup path, source paths, destination paths, and relevant parent directories.
- Protect the backup file with restrictive permissions and refuse to load files owned by an unexpected user.
- Revalidate containment and file type immediately before every copy and deletion.
- Avoid check-then-act destination handling. Use filesystem operations that fail atomically if the destination already exists.
- Delete a source only after confirming that it is an expected organized copy and that the restoration completed successfully.
- Consider authenticating backup contents or storing operation state in a user-private application data directory.