public static function Crypt::randomBytes in Service Container 7

Same name and namespace in other branches

7.2 lib/Drupal/Component/Utility/Crypt.php \Drupal\Component\Utility\Crypt::randomBytes()

Returns a string of highly randomized bytes (over the full 8-bit range).

This function is better than simply calling mt_rand() or any other built-in PHP function because it can return a long string of bytes (compared to < 4 bytes normally from mt_rand()) and uses the best available pseudo-random source.

Parameters

int $count: The number of characters (bytes) to return in the string.

Return value

string A randomly generated string.

2 calls to Crypt::randomBytes()

Crypt::randomBytesBase64 in lib/Drupal/Component/Utility/Crypt.php: Returns a URL-safe, base64 encoded string of highly randomized bytes.
Php::generate in lib/Drupal/Component/Uuid/Php.php: Generates a Universally Unique IDentifier (UUID).

File

lib/Drupal/Component/Utility/Crypt.php, line 31: Contains \Drupal\Component\Utility\Crypt.

Class

Crypt: Utility class for cryptographically-secure string handling routines.

Namespace

Drupal\Component\Utility

Code

public static function randomBytes($count) {

  // $random_state does not use drupal_static as it stores random bytes.
  static $random_state, $bytes;
  $missing_bytes = $count - strlen($bytes);
  if ($missing_bytes > 0) {

    // openssl_random_pseudo_bytes() will find entropy in a system-dependent
    // way.
    if (function_exists('openssl_random_pseudo_bytes')) {
      $bytes .= openssl_random_pseudo_bytes($missing_bytes);
    }
    elseif (function_exists('mcrypt_create_iv') && defined('MCRYPT_DEV_URANDOM')) {
      $bytes .= mcrypt_create_iv($count, MCRYPT_DEV_URANDOM);
    }
    elseif ($fh = @fopen('/dev/urandom', 'rb')) {

      // PHP only performs buffered reads, so in reality it will always read
      // at least 4096 bytes. Thus, it costs nothing extra to read and store
      // that much so as to speed any additional invocations.
      $bytes .= fread($fh, max(4096, $missing_bytes));
      fclose($fh);
    }

    // If we couldn't get enough entropy, this simple hash-based PRNG will
    // generate a good set of pseudo-random bytes on any system.
    // Note that it may be important that our $random_state is passed
    // through hash() prior to being rolled into $output, that the two hash()
    // invocations are different, and that the extra input into the first one -
    // the microtime() - is prepended rather than appended. This is to avoid
    // directly leaking $random_state via the $output stream, which could
    // allow for trivial prediction of further "random" numbers.
    if (strlen($bytes) < $count) {

      // Initialize on the first call. The contents of $_SERVER includes a mix
      // of user-specific and system information that varies a little with
      // each page.
      if (!isset($random_state)) {
        $random_state = print_r($_SERVER, TRUE);
        if (function_exists('getmypid')) {

          // Further initialize with the somewhat random PHP process ID.
          $random_state .= getmypid();
        }
        $bytes = '';
      }
      do {
        $random_state = hash('sha256', microtime() . mt_rand() . $random_state);
        $bytes .= hash('sha256', mt_rand() . $random_state, TRUE);
      } while (strlen($bytes) < $count);
    }
  }
  $output = substr($bytes, 0, $count);
  $bytes = substr($bytes, $count);
  return $output;
}

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