Function validateOutputPath

browse/src/path-security.ts:33–75

(filePath: string)

/** Validate a file path for writing (screenshot, pdf, download, scrape, archive). */
export function validateOutputPath(filePath: string): void {
  const resolved = path.resolve(filePath);

  // If the target already exists and is a symlink, resolve through it.
  // Without this, a symlink at /tmp/evil.png → /etc/crontab passes the
  // parent-directory check (parent is /tmp, which is safe) but the actual
  // write follows the symlink to /etc/crontab.
  try {
    const stat = fs.lstatSync(resolved);
    if (stat.isSymbolicLink()) {
      const realTarget = fs.realpathSync(resolved);
      const isSafe = SAFE_DIRECTORIES.some(dir => isPathWithin(realTarget, dir));
      if (!isSafe) {
        throw new Error(`Path must be within: ${SAFE_DIRECTORIES.join(', ')}`);
      }
      return; // symlink target verified, no need to check parent
    }
  } catch (e: any) {
    // ENOENT = file doesn't exist yet, fall through to parent-dir check
    if (e.code !== 'ENOENT') throw e;
  }

  // For new files (no existing symlink), verify the parent directory.
  // The file itself may not exist yet (e.g., screenshot output).
  // This also handles macOS /tmp → /private/tmp transparently.
  let dir = path.dirname(resolved);
  let realDir: string;
  try {
    realDir = fs.realpathSync(dir);
  } catch {
    try {
      realDir = fs.realpathSync(path.dirname(dir));
    } catch {
      throw new Error(`Path must be within: ${SAFE_DIRECTORIES.join(', ')}`);
    }
  }

  const realResolved = path.join(realDir, path.basename(resolved));
  const isSafe = SAFE_DIRECTORIES.some(dir => isPathWithin(realResolved, dir));
  if (!isSafe) {
    throw new Error(`Path must be within: ${SAFE_DIRECTORIES.join(', ')}`);
  }
}

/** Validate a file path for reading (eval command). */
export function validateReadPath(filePath: string): void {