runtime-guard

Implementation Reference

• src/tools/file_tools.py:196-251 (handler)

  The core implementation of the list_directory tool, which includes policy checks, path validation, and directory listing logic.

  def list_directory(path: str, ctx: Context | None = None) -> str:
      context_tokens = activate_runtime_context(ctx)
      path = str(pathlib.Path(WORKSPACE_ROOT) / path) if not os.path.isabs(path) else path
  
      try:
          path_check = check_path_policy(path, tool="list_directory")
          if path_check:
              result = PolicyResult(allowed=False, reason=path_check[0], decision_tier="blocked", matched_rule=path_check[1])
          else:
              result = PolicyResult(allowed=True, reason="allowed", decision_tier="allowed", matched_rule=None)
  
          if result.allowed:
              if not os.path.exists(path):
                  append_log_entry(build_log_entry("list_directory", result, path=path, error="path not found"))
                  return f"Error: path not found: {path}"
  
              if not os.path.isdir(path):
                  append_log_entry(build_log_entry("list_directory", result, path=path, error="not a directory"))
                  return f"Error: '{path}' is a file, not a directory"
  
              depth = relative_depth(path)
              max_depth = POLICY.get("allowed", {}).get("max_directory_depth", 5)
              if depth > max_depth:
                  result = PolicyResult(
                      allowed=False,
                      reason=f"Directory depth {depth} exceeds the policy limit of {max_depth} (allowed.max_directory_depth): '{path}'",
                      decision_tier="blocked",
                      matched_rule="allowed.max_directory_depth",
                  )
  
          append_log_entry(build_log_entry("list_directory", result, path=path))
          if not result.allowed:
              return f"[POLICY BLOCK] {result.reason}"
  
          lines = [f"Contents of {path}:"]
          try:
              entries = sorted(os.scandir(path), key=lambda e: (e.is_file(), e.name))
          except OSError as e:
              return f"Error reading directory: {e}"
  
          for entry in entries:
              try:
                  stat = entry.stat(follow_symlinks=False)
                  mtime = datetime.datetime.fromtimestamp(stat.st_mtime, datetime.UTC).isoformat().replace("+00:00", "Z")
                  kind = "file" if entry.is_file(follow_symlinks=False) else "directory"
                  size = f"{stat.st_size} bytes" if kind == "file" else "-"
                  lines.append(f"  {entry.name}  [{kind}]  size={size}  modified={mtime}")
              except OSError:
                  lines.append(f"  {entry.name}  [unreadable]")
  
          if len(lines) == 1:
              lines.append("  (empty)")
  
          return "\n".join(lines)
      finally:
          reset_runtime_context(context_tokens)

• src/server.py:20-29 (registration)

  Tool registration for the list_directory function in the MCP server.

  for tool in [
      server_info,
      restore_backup,
      execute_command,
      read_file,
      write_file,
      delete_file,
      list_directory,
  ]:
      mcp.tool()(tool)