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   1  <?php
   2  
   3  /**
   4   * Random Number Generator
   5   *
   6   * PHP version 5
   7   *
   8   * Here's a short example of how to use this library:
   9   * <code>
  10   * <?php
  11   *    include 'vendor/autoload.php';
  12   *
  13   *    echo bin2hex(\phpseclib3\Crypt\Random::string(8));
  14   * ?>
  15   * </code>
  16   *
  17   * @category  Crypt
  18   * @package   Random
  19   * @author    Jim Wigginton <[email protected]>
  20   * @copyright 2007 Jim Wigginton
  21   * @license   http://www.opensource.org/licenses/mit-license.html  MIT License
  22   * @link      http://phpseclib.sourceforge.net
  23   */
  24  
  25  namespace phpseclib3\Crypt;
  26  
  27  /**
  28   * Pure-PHP Random Number Generator
  29   *
  30   * @package Random
  31   * @author  Jim Wigginton <[email protected]>
  32   * @access  public
  33   */
  34  abstract class Random
  35  {
  36      /**
  37       * Generate a random string.
  38       *
  39       * Although microoptimizations are generally discouraged as they impair readability this function is ripe with
  40       * microoptimizations because this function has the potential of being called a huge number of times.
  41       * eg. for RSA key generation.
  42       *
  43       * @param int $length
  44       * @throws \RuntimeException if a symmetric cipher is needed but not loaded
  45       * @return string
  46       */
  47      public static function string($length)
  48      {
  49          if (!$length) {
  50              return '';
  51          }
  52  
  53          try {
  54              return random_bytes($length);
  55          } catch (\Exception $e) {
  56              // random_compat will throw an Exception, which in PHP 5 does not implement Throwable
  57          } catch (\Throwable $e) {
  58              // If a sufficient source of randomness is unavailable, random_bytes() will throw an
  59              // object that implements the Throwable interface (Exception, TypeError, Error).
  60              // We don't actually need to do anything here. The string() method should just continue
  61              // as normal. Note, however, that if we don't have a sufficient source of randomness for
  62              // random_bytes(), most of the other calls here will fail too, so we'll end up using
  63              // the PHP implementation.
  64          }
  65          // at this point we have no choice but to use a pure-PHP CSPRNG
  66  
  67          // cascade entropy across multiple PHP instances by fixing the session and collecting all
  68          // environmental variables, including the previous session data and the current session
  69          // data.
  70          //
  71          // mt_rand seeds itself by looking at the PID and the time, both of which are (relatively)
  72          // easy to guess at. linux uses mouse clicks, keyboard timings, etc, as entropy sources, but
  73          // PHP isn't low level to be able to use those as sources and on a web server there's not likely
  74          // going to be a ton of keyboard or mouse action. web servers do have one thing that we can use
  75          // however, a ton of people visiting the website. obviously you don't want to base your seeding
  76          // solely on parameters a potential attacker sends but (1) not everything in $_SERVER is controlled
  77          // by the user and (2) this isn't just looking at the data sent by the current user - it's based
  78          // on the data sent by all users. one user requests the page and a hash of their info is saved.
  79          // another user visits the page and the serialization of their data is utilized along with the
  80          // server environment stuff and a hash of the previous http request data (which itself utilizes
  81          // a hash of the session data before that). certainly an attacker should be assumed to have
  82          // full control over his own http requests. he, however, is not going to have control over
  83          // everyone's http requests.
  84          static $crypto = false, $v;
  85          if ($crypto === false) {
  86              // save old session data
  87              $old_session_id = session_id();
  88              $old_use_cookies = ini_get('session.use_cookies');
  89              $old_session_cache_limiter = session_cache_limiter();
  90              $_OLD_SESSION = isset($_SESSION) ? $_SESSION : false;
  91              if ($old_session_id != '') {
  92                  session_write_close();
  93              }
  94  
  95              session_id(1);
  96              ini_set('session.use_cookies', 0);
  97              session_cache_limiter('');
  98              session_start();
  99  
 100              $v = (isset($_SERVER) ? self::safe_serialize($_SERVER) : '') .
 101                   (isset($_POST) ? self::safe_serialize($_POST) : '') .
 102                   (isset($_GET) ? self::safe_serialize($_GET) : '') .
 103                   (isset($_COOKIE) ? self::safe_serialize($_COOKIE) : '') .
 104                   self::safe_serialize($GLOBALS) .
 105                   self::safe_serialize($_SESSION) .
 106                   self::safe_serialize($_OLD_SESSION);
 107              $v = $seed = $_SESSION['seed'] = sha1($v, true);
 108              if (!isset($_SESSION['count'])) {
 109                  $_SESSION['count'] = 0;
 110              }
 111              $_SESSION['count']++;
 112  
 113              session_write_close();
 114  
 115              // restore old session data
 116              if ($old_session_id != '') {
 117                  session_id($old_session_id);
 118                  session_start();
 119                  ini_set('session.use_cookies', $old_use_cookies);
 120                  session_cache_limiter($old_session_cache_limiter);
 121              } else {
 122                  if ($_OLD_SESSION !== false) {
 123                      $_SESSION = $_OLD_SESSION;
 124                      unset($_OLD_SESSION);
 125                  } else {
 126                      unset($_SESSION);
 127                  }
 128              }
 129  
 130              // in SSH2 a shared secret and an exchange hash are generated through the key exchange process.
 131              // the IV client to server is the hash of that "nonce" with the letter A and for the encryption key it's the letter C.
 132              // if the hash doesn't produce enough a key or an IV that's long enough concat successive hashes of the
 133              // original hash and the current hash. we'll be emulating that. for more info see the following URL:
 134              //
 135              // http://tools.ietf.org/html/rfc4253#section-7.2
 136              //
 137              // see the is_string($crypto) part for an example of how to expand the keys
 138              $key = sha1($seed . 'A', true);
 139              $iv = sha1($seed . 'C', true);
 140  
 141              // ciphers are used as per the nist.gov link below. also, see this link:
 142              //
 143              // http://en.wikipedia.org/wiki/Cryptographically_secure_pseudorandom_number_generator#Designs_based_on_cryptographic_primitives
 144              switch (true) {
 145                  case class_exists('\phpseclib3\Crypt\AES'):
 146                      $crypto = new AES('ctr');
 147                      break;
 148                  case class_exists('\phpseclib3\Crypt\Twofish'):
 149                      $crypto = new Twofish('ctr');
 150                      break;
 151                  case class_exists('\phpseclib3\Crypt\Blowfish'):
 152                      $crypto = new Blowfish('ctr');
 153                      break;
 154                  case class_exists('\phpseclib3\Crypt\TripleDES'):
 155                      $crypto = new TripleDES('ctr');
 156                      break;
 157                  case class_exists('\phpseclib3\Crypt\DES'):
 158                      $crypto = new DES('ctr');
 159                      break;
 160                  case class_exists('\phpseclib3\Crypt\RC4'):
 161                      $crypto = new RC4();
 162                      break;
 163                  default:
 164                      throw new \RuntimeException(__CLASS__ . ' requires at least one symmetric cipher be loaded');
 165              }
 166  
 167              $crypto->setKey(substr($key, 0, $crypto->getKeyLength() >> 3));
 168              $crypto->setIV(substr($iv, 0, $crypto->getBlockLength() >> 3));
 169              $crypto->enableContinuousBuffer();
 170          }
 171  
 172          //return $crypto->encrypt(str_repeat("\0", $length));
 173  
 174          // the following is based off of ANSI X9.31:
 175          //
 176          // http://csrc.nist.gov/groups/STM/cavp/documents/rng/931rngext.pdf
 177          //
 178          // OpenSSL uses that same standard for it's random numbers:
 179          //
 180          // http://www.opensource.apple.com/source/OpenSSL/OpenSSL-38/openssl/fips-1.0/rand/fips_rand.c
 181          // (do a search for "ANS X9.31 A.2.4")
 182          $result = '';
 183          while (strlen($result) < $length) {
 184              $i = $crypto->encrypt(microtime()); // strlen(microtime()) == 21
 185              $r = $crypto->encrypt($i ^ $v); // strlen($v) == 20
 186              $v = $crypto->encrypt($r ^ $i); // strlen($r) == 20
 187              $result .= $r;
 188          }
 189  
 190          return substr($result, 0, $length);
 191      }
 192  
 193      /**
 194       * Safely serialize variables
 195       *
 196       * If a class has a private __sleep() it'll emit a warning
 197       * @return mixed
 198       * @param mixed $arr
 199       */
 200      private static function safe_serialize(&$arr)
 201      {
 202          if (is_object($arr)) {
 203              return '';
 204          }
 205          if (!is_array($arr)) {
 206              return serialize($arr);
 207          }
 208          // prevent circular array recursion
 209          if (isset($arr['__phpseclib_marker'])) {
 210              return '';
 211          }
 212          $safearr = [];
 213          $arr['__phpseclib_marker'] = true;
 214          foreach (array_keys($arr) as $key) {
 215              // do not recurse on the '__phpseclib_marker' key itself, for smaller memory usage
 216              if ($key !== '__phpseclib_marker') {
 217                  $safearr[$key] = self::safe_serialize($arr[$key]);
 218              }
 219          }
 220          unset($arr['__phpseclib_marker']);
 221          return serialize($safearr);
 222      }
 223  }