function filter_xss_bad_protocol in JS Callback Handler 5.2

l() calls check_url(), which needs to check for XSS attacks.

File

./js.php, line 130

Callback page that serves custom JavaScript requests on a Drupal installation.

Code

function filter_xss_bad_protocol($string, $decode = TRUE) {
  static $allowed_protocols;
  if (!isset($allowed_protocols)) {
    $allowed_protocols = array_flip(variable_get('filter_allowed_protocols', array(
      'http',
      'https',
      'ftp',
      'news',
      'nntp',
      'telnet',
      'mailto',
      'irc',
      'ssh',
      'sftp',
      'webcal',
    )));
  }

  // Get the plain text representation of the attribute value (i.e. its meaning).
  if ($decode) {
    $string = decode_entities($string);
  }

  // Iteratively remove any invalid protocol found.
  do {
    $before = $string;
    $colonpos = strpos($string, ':');
    if ($colonpos > 0) {

      // We found a colon, possibly a protocol. Verify.
      $protocol = substr($string, 0, $colonpos);

      // If a colon is preceded by a slash, question mark or hash, it cannot
      // possibly be part of the URL scheme. This must be a relative URL,
      // which inherits the (safe) protocol of the base document.
      if (preg_match('![/?#]!', $protocol)) {
        break;
      }

      // Per RFC2616, section 3.2.3 (URI Comparison) scheme comparison must be case-insensitive.
      // Check if this is a disallowed protocol.
      if (!isset($allowed_protocols[strtolower($protocol)])) {
        $string = substr($string, $colonpos + 1);
      }
    }
  } while ($before != $string);
  return check_plain($string);
}