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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   * @author    Jim Wigginton <terrafrost@php.net>
  18   * @copyright 2007 Jim Wigginton
  19   * @license   http://www.opensource.org/licenses/mit-license.html  MIT License
  20   * @link      http://phpseclib.sourceforge.net
  21   */
  22  
  23  namespace phpseclib3\Crypt;
  24  
  25  /**
  26   * Pure-PHP Random Number Generator
  27   *
  28   * @author  Jim Wigginton <terrafrost@php.net>
  29   */
  30  abstract class Random
  31  {
  32      /**
  33       * Generate a random string.
  34       *
  35       * Although microoptimizations are generally discouraged as they impair readability this function is ripe with
  36       * microoptimizations because this function has the potential of being called a huge number of times.
  37       * eg. for RSA key generation.
  38       *
  39       * @param int $length
  40       * @throws \RuntimeException if a symmetric cipher is needed but not loaded
  41       * @return string
  42       */
  43      public static function string($length)
  44      {
  45          if (!$length) {
  46              return '';
  47          }
  48  
  49          try {
  50              return random_bytes($length);
  51          } catch (\Exception $e) {
  52              // random_compat will throw an Exception, which in PHP 5 does not implement Throwable
  53          } catch (\Throwable $e) {
  54              // If a sufficient source of randomness is unavailable, random_bytes() will throw an
  55              // object that implements the Throwable interface (Exception, TypeError, Error).
  56              // We don't actually need to do anything here. The string() method should just continue
  57              // as normal. Note, however, that if we don't have a sufficient source of randomness for
  58              // random_bytes(), most of the other calls here will fail too, so we'll end up using
  59              // the PHP implementation.
  60          }
  61          // at this point we have no choice but to use a pure-PHP CSPRNG
  62  
  63          // cascade entropy across multiple PHP instances by fixing the session and collecting all
  64          // environmental variables, including the previous session data and the current session
  65          // data.
  66          //
  67          // mt_rand seeds itself by looking at the PID and the time, both of which are (relatively)
  68          // easy to guess at. linux uses mouse clicks, keyboard timings, etc, as entropy sources, but
  69          // PHP isn't low level to be able to use those as sources and on a web server there's not likely
  70          // going to be a ton of keyboard or mouse action. web servers do have one thing that we can use
  71          // however, a ton of people visiting the website. obviously you don't want to base your seeding
  72          // solely on parameters a potential attacker sends but (1) not everything in $_SERVER is controlled
  73          // by the user and (2) this isn't just looking at the data sent by the current user - it's based
  74          // on the data sent by all users. one user requests the page and a hash of their info is saved.
  75          // another user visits the page and the serialization of their data is utilized along with the
  76          // server environment stuff and a hash of the previous http request data (which itself utilizes
  77          // a hash of the session data before that). certainly an attacker should be assumed to have
  78          // full control over his own http requests. he, however, is not going to have control over
  79          // everyone's http requests.
  80          static $crypto = false, $v;
  81          if ($crypto === false) {
  82              // save old session data
  83              $old_session_id = session_id();
  84              $old_use_cookies = ini_get('session.use_cookies');
  85              $old_session_cache_limiter = session_cache_limiter();
  86              $_OLD_SESSION = isset($_SESSION) ? $_SESSION : false;
  87              if ($old_session_id != '') {
  88                  session_write_close();
  89              }
  90  
  91              session_id(1);
  92              ini_set('session.use_cookies', 0);
  93              session_cache_limiter('');
  94              session_start();
  95  
  96              $v = (isset($_SERVER) ? self::safe_serialize($_SERVER) : '') .
  97                   (isset($_POST) ? self::safe_serialize($_POST) : '') .
  98                   (isset($_GET) ? self::safe_serialize($_GET) : '') .
  99                   (isset($_COOKIE) ? self::safe_serialize($_COOKIE) : '') .
 100                   // as of PHP 8.1 $GLOBALS can't be accessed by reference, which eliminates
 101                   // the need for phpseclib_safe_serialize. see https://wiki.php.net/rfc/restrict_globals_usage
 102                   // for more info
 103                   (version_compare(PHP_VERSION, '8.1.0', '>=') ? serialize($GLOBALS) : self::safe_serialize($GLOBALS)) .
 104                   self::safe_serialize($_SESSION) .
 105                   self::safe_serialize($_OLD_SESSION);
 106              $v = $seed = $_SESSION['seed'] = sha1($v, true);
 107              if (!isset($_SESSION['count'])) {
 108                  $_SESSION['count'] = 0;
 109              }
 110              $_SESSION['count']++;
 111  
 112              session_write_close();
 113  
 114              // restore old session data
 115              if ($old_session_id != '') {
 116                  session_id($old_session_id);
 117                  session_start();
 118                  ini_set('session.use_cookies', $old_use_cookies);
 119                  session_cache_limiter($old_session_cache_limiter);
 120              } else {
 121                  if ($_OLD_SESSION !== false) {
 122                      $_SESSION = $_OLD_SESSION;
 123                      unset($_OLD_SESSION);
 124                  } else {
 125                      unset($_SESSION);
 126                  }
 127              }
 128  
 129              // in SSH2 a shared secret and an exchange hash are generated through the key exchange process.
 130              // the IV client to server is the hash of that "nonce" with the letter A and for the encryption key it's the letter C.
 131              // if the hash doesn't produce enough a key or an IV that's long enough concat successive hashes of the
 132              // original hash and the current hash. we'll be emulating that. for more info see the following URL:
 133              //
 134              // http://tools.ietf.org/html/rfc4253#section-7.2
 135              //
 136              // see the is_string($crypto) part for an example of how to expand the keys
 137              $key = sha1($seed . 'A', true);
 138              $iv = sha1($seed . 'C', true);
 139  
 140              // ciphers are used as per the nist.gov link below. also, see this link:
 141              //
 142              // http://en.wikipedia.org/wiki/Cryptographically_secure_pseudorandom_number_generator#Designs_based_on_cryptographic_primitives
 143              switch (true) {
 144                  case class_exists('\phpseclib3\Crypt\AES'):
 145                      $crypto = new AES('ctr');
 146                      break;
 147                  case class_exists('\phpseclib3\Crypt\Twofish'):
 148                      $crypto = new Twofish('ctr');
 149                      break;
 150                  case class_exists('\phpseclib3\Crypt\Blowfish'):
 151                      $crypto = new Blowfish('ctr');
 152                      break;
 153                  case class_exists('\phpseclib3\Crypt\TripleDES'):
 154                      $crypto = new TripleDES('ctr');
 155                      break;
 156                  case class_exists('\phpseclib3\Crypt\DES'):
 157                      $crypto = new DES('ctr');
 158                      break;
 159                  case class_exists('\phpseclib3\Crypt\RC4'):
 160                      $crypto = new RC4();
 161                      break;
 162                  default:
 163                      throw new \RuntimeException(__CLASS__ . ' requires at least one symmetric cipher be loaded');
 164              }
 165  
 166              $crypto->setKey(substr($key, 0, $crypto->getKeyLength() >> 3));
 167              $crypto->setIV(substr($iv, 0, $crypto->getBlockLength() >> 3));
 168              $crypto->enableContinuousBuffer();
 169          }
 170  
 171          //return $crypto->encrypt(str_repeat("\0", $length));
 172  
 173          // the following is based off of ANSI X9.31:
 174          //
 175          // http://csrc.nist.gov/groups/STM/cavp/documents/rng/931rngext.pdf
 176          //
 177          // OpenSSL uses that same standard for it's random numbers:
 178          //
 179          // http://www.opensource.apple.com/source/OpenSSL/OpenSSL-38/openssl/fips-1.0/rand/fips_rand.c
 180          // (do a search for "ANS X9.31 A.2.4")
 181          $result = '';
 182          while (strlen($result) < $length) {
 183              $i = $crypto->encrypt(microtime()); // strlen(microtime()) == 21
 184              $r = $crypto->encrypt($i ^ $v); // strlen($v) == 20
 185              $v = $crypto->encrypt($r ^ $i); // strlen($r) == 20
 186              $result .= $r;
 187          }
 188  
 189          return substr($result, 0, $length);
 190      }
 191  
 192      /**
 193       * Safely serialize variables
 194       *
 195       * If a class has a private __sleep() it'll emit a warning
 196       * @return mixed
 197       * @param mixed $arr
 198       */
 199      private static function safe_serialize(&$arr)
 200      {
 201          if (is_object($arr)) {
 202              return '';
 203          }
 204          if (!is_array($arr)) {
 205              return serialize($arr);
 206          }
 207          // prevent circular array recursion
 208          if (isset($arr['__phpseclib_marker'])) {
 209              return '';
 210          }
 211          $safearr = [];
 212          $arr['__phpseclib_marker'] = true;
 213          foreach (array_keys($arr) as $key) {
 214              // do not recurse on the '__phpseclib_marker' key itself, for smaller memory usage
 215              if ($key !== '__phpseclib_marker') {
 216                  $safearr[$key] = self::safe_serialize($arr[$key]);
 217              }
 218          }
 219          unset($arr['__phpseclib_marker']);
 220          return serialize($safearr);
 221      }
 222  }