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<?php
/*
* The RandomLib library for securely generating random numbers and strings in PHP
*
* @author Anthony Ferrara <ircmaxell@ircmaxell.com>
* @copyright 2011 The Authors
* @license http://www.opensource.org/licenses/mit-license.html MIT License
* @version Build @@version@@
*/
/**
* The Microtime Random Number Source
*
* This uses the current micro-second (looped several times) for a **very** weak
* random number source. This is only useful when combined with several other
* stronger sources
*
* PHP version 5.3
*
* @category PHPCryptLib
* @package Random
* @subpackage Source
*
* @author Anthony Ferrara <ircmaxell@ircmaxell.com>
* @copyright 2011 The Authors
* @license http://www.opensource.org/licenses/mit-license.html MIT License
*
* @version Build @@version@@
*/
namespace RandomLib\Source;
use SecurityLib\Strength;
use SecurityLib\Util;
/**
* The Microtime Random Number Source
*
* This uses the current micro-second (looped several times) for a **very** weak
* random number source. This is only useful when combined with several other
* stronger sources
*
* @category PHPCryptLib
* @package Random
* @subpackage Source
*
* @author Anthony Ferrara <ircmaxell@ircmaxell.com>
* @codeCoverageIgnore
*/
final class MicroTime extends \RandomLib\AbstractSource
{
/**
* A static counter to ensure unique hashes and prevent state collisions
*
* @var int A counter
*/
private static $counter = null;
/**
* The current state of the random number generator.
*
* @var string The state of the PRNG
*/
private static $state = '';
public function __construct()
{
$state = self::$state;
if (function_exists('posix_times')) {
$state .= serialize(posix_times());
}
if (!defined('HHVM_VERSION') && function_exists('zend_thread_id')) {
$state .= zend_thread_id();
}
if (function_exists('hphp_get_thread_id')) {
$state .= hphp_get_thread_id();
}
$state .= getmypid() . memory_get_usage();
$state .= serialize($_ENV);
$state .= serialize($_SERVER);
$state .= count(debug_backtrace(false));
self::$state = hash('sha512', $state, true);
if (is_null(self::$counter)) {
list(, self::$counter) = unpack("i", Util::safeSubstr(self::$state, 0, 4));
$seed = $this->generate(Util::safeStrlen(dechex(PHP_INT_MAX)));
list(, self::$counter) = unpack("i", $seed);
}
}
/**
* Generate a random string of the specified size
*
* @param int $size The size of the requested random string
*
* @return string A string of the requested size
*/
public function generate($size)
{
$result = '';
$seed = microtime() . memory_get_usage();
self::$state = hash('sha512', self::$state . $seed, true);
/**
* Make the generated randomness a bit better by forcing a GC run which
* should complete in a indeterminate amount of time, hence improving
* the strength of the randomness a bit. It's still not crypto-safe,
* but at least it's more difficult to predict.
*/
gc_collect_cycles();
for ($i = 0; $i < $size; $i += 8) {
$seed = self::$state .
microtime() .
pack('Ni', $i, self::counter());
self::$state = hash('sha512', $seed, true);
/**
* We only use the first 8 bytes here to prevent exposing the state
* in its entirety, which could potentially expose other random
* generations in the future (in the same process)...
*/
$result .= Util::safeSubstr(self::$state, 0, 8);
}
return Util::safeSubstr($result, 0, $size);
}
private static function counter()
{
if (self::$counter >= PHP_INT_MAX) {
self::$counter = -1 * PHP_INT_MAX - 1;
} else {
self::$counter++;
}
return self::$counter;
}
}
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