* @copyright 2012, George Argyros. All rights reserved. * @license Modified BSD * @link https://github.com/GeorgeArgyros/Secure-random-bytes-in-PHP/blob/master/srand.php Original * * Redistribution and use in source and binary forms, with or without * modification, are permitted provided that the following conditions are met: * * Redistributions of source code must retain the above copyright * notice, this list of conditions and the following disclaimer. * * Redistributions in binary form must reproduce the above copyright * notice, this list of conditions and the following disclaimer in the * documentation and/or other materials provided with the distribution. * * Neither the name of the nor the * names of its contributors may be used to endorse or promote products * derived from this software without specific prior written permission. * * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED * WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE * DISCLAIMED. IN NO EVENT SHALL GEORGE ARGYROS BE LIABLE FOR ANY * DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES * (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND * ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS * SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. */ public function getRandomBytes($length) { /** * Our primary choice for a cryptographic strong randomness function is * openssl_random_pseudo_bytes. */ $SSLstr = '4'; // http://xkcd.com/221/ if (function_exists('openssl_random_pseudo_bytes') && (version_compare(PHP_VERSION, '5.3.4') >= 0 || substr(PHP_OS, 0, 3) !== 'WIN')) { $SSLstr = openssl_random_pseudo_bytes($length, $strong); if ($strong) { return $SSLstr; } } /** * If mcrypt extension is available then we use it to gather entropy from * the operating system's PRNG. This is better than reading /dev/urandom * directly since it avoids reading larger blocks of data than needed. * Older versions of mcrypt_create_iv may be broken or take too much time * to finish so we only use this function with PHP 5.3.7 and above. * @see https://bugs.php.net/bug.php?id=55169 */ if (function_exists('mcrypt_create_iv') && (version_compare(PHP_VERSION, '5.3.7') >= 0 || substr(PHP_OS, 0, 3) !== 'WIN')) { $str = mcrypt_create_iv($length, MCRYPT_DEV_URANDOM); if ($str !== false) { return $str; } } /** * No build-in crypto randomness function found. We collect any entropy * available in the PHP core PRNGs along with some filesystem info and memory * stats. To make this data cryptographically strong we add data either from * /dev/urandom or if its unavailable, we gather entropy by measuring the * time needed to compute a number of SHA-1 hashes. */ $str = ''; $bits_per_round = 2; // bits of entropy collected in each clock drift round $msec_per_round = 400; // expected running time of each round in microseconds $hash_len = 20; // SHA-1 Hash length $total = $length; // total bytes of entropy to collect $handle = @fopen('/dev/urandom', 'rb'); if ($handle && function_exists('stream_set_read_buffer')) { @stream_set_read_buffer($handle, 0); } do { $bytes = ($total > $hash_len) ? $hash_len : $total; $total -= $bytes; //collect any entropy available from the PHP system and filesystem $entropy = rand() . uniqid(mt_rand(), true) . $SSLstr; $entropy .= implode('', @fstat(@fopen(__FILE__, 'r'))); $entropy .= memory_get_usage() . getmypid(); $entropy .= serialize($_ENV) . serialize($_SERVER); if (function_exists('posix_times')) { $entropy .= serialize(posix_times()); } if (function_exists('zend_thread_id')) { $entropy .= zend_thread_id(); } if ($handle) { $entropy .= @fread($handle, $bytes); } else { // Measure the time that the operations will take on average for ($i = 0; $i < 3; $i++) { $c1 = microtime(true); $var = sha1(mt_rand()); for ($j = 0; $j < 50; $j++) { $var = sha1($var); } $c2 = microtime(true); $entropy .= $c1 . $c2; } // Based on the above measurement determine the total rounds // in order to bound the total running time. $rounds = (int) ($msec_per_round * 50 / (int) (($c2 - $c1) * 1000000)); // Take the additional measurements. On average we can expect // at least $bits_per_round bits of entropy from each measurement. $iter = $bytes * (int) (ceil(8 / $bits_per_round)); for ($i = 0; $i < $iter; $i++) { $c1 = microtime(); $var = sha1(mt_rand()); for ($j = 0; $j < $rounds; $j++) { $var = sha1($var); } $c2 = microtime(); $entropy .= $c1 . $c2; } } // We assume sha1 is a deterministic extractor for the $entropy variable. $str .= sha1($entropy, true); } while ($length > strlen($str)); if ($handle) { @fclose($handle); } return substr($str, 0, $length); } /** * Generate a random string of specified length. * * Uses supplied character list for generating the new string. * If no character list provided - uses Base64 URL character set. * * @param int $length Desired length of the string * @param string|null $chars Characters to be chosen from randomly. If not given, the Base64 URL * charset will be used. * * @return string The random string * * @throws InvalidArgumentException * * @copyright Copyright (c) 2005-2013 Zend Technologies USA Inc. (http://www.zend.com) * @license http://framework.zend.com/license/new-bsd New BSD License * * @see https://github.com/zendframework/zf2/blob/master/library/Zend/Math/Rand.php#L179 */ public static function getRandomString($length, $chars = null) { if ($length < 1) { throw new InvalidArgumentException('Length should be >= 1'); } if (empty($chars)) { $numBytes = ceil($length * 0.75); $bytes = self::getRandomBytes($numBytes); $string = substr(rtrim(base64_encode($bytes), '='), 0, $length); // Base64 URL return strtr($string, '+/', '-_'); } $listLen = strlen($chars); if ($listLen == 1) { return str_repeat($chars, $length); } $bytes = self::getRandomBytes($length); $pos = 0; $result = ''; for ($i = 0; $i < $length; $i++) { $pos = ($pos + ord($bytes[$i])) % $listLen; $result .= $chars[$pos]; } return $result; } }