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<?php
/*
* This file is part of the Symfony package.
*
* (c) Fabien Potencier <fabien@symfony.com>
*
* For the full copyright and license information, please view the LICENSE
* file that was distributed with this source code.
*/
namespace Symfony\Component\Security\Core\Util;
use Psr\Log\LoggerInterface;
/**
* A secure random number generator implementation.
*
* @author Fabien Potencier <fabien@symfony.com>
* @author Johannes M. Schmitt <schmittjoh@gmail.com>
*/
final class SecureRandom implements SecureRandomInterface
{
private $logger;
private $useOpenSsl;
private $seed;
private $seedUpdated;
private $seedLastUpdatedAt;
private $seedFile;
/**
* Constructor.
*
* Be aware that a guessable seed will severely compromise the PRNG
* algorithm that is employed.
*
* @param string $seedFile
* @param LoggerInterface $logger
*/
public function __construct($seedFile = null, LoggerInterface $logger = null)
{
$this->seedFile = $seedFile;
$this->logger = $logger;
// determine whether to use OpenSSL
if (!function_exists('openssl_random_pseudo_bytes')) {
if (null !== $this->logger) {
$this->logger->notice('It is recommended that you enable the "openssl" extension for random number generation.');
}
$this->useOpenSsl = false;
} else {
$this->useOpenSsl = true;
}
}
/**
* {@inheritdoc}
*/
public function nextBytes($nbBytes)
{
// try OpenSSL
if ($this->useOpenSsl) {
$bytes = openssl_random_pseudo_bytes($nbBytes, $strong);
if (false !== $bytes && true === $strong) {
return $bytes;
}
if (null !== $this->logger) {
$this->logger->info('OpenSSL did not produce a secure random number.');
}
}
// initialize seed
if (null === $this->seed) {
if (null === $this->seedFile) {
throw new \RuntimeException('You need to specify a file path to store the seed.');
}
if (is_file($this->seedFile)) {
list($this->seed, $this->seedLastUpdatedAt) = $this->readSeed();
} else {
$this->seed = uniqid(mt_rand(), true);
$this->updateSeed();
}
}
$bytes = '';
while (strlen($bytes) < $nbBytes) {
static $incr = 1;
$bytes .= hash('sha512', $incr++.$this->seed.uniqid(mt_rand(), true).$nbBytes, true);
$this->seed = base64_encode(hash('sha512', $this->seed.$bytes.$nbBytes, true));
$this->updateSeed();
}
return substr($bytes, 0, $nbBytes);
}
private function readSeed()
{
return json_decode(file_get_contents($this->seedFile));
}
private function updateSeed()
{
if (!$this->seedUpdated && $this->seedLastUpdatedAt < time() - mt_rand(1, 10)) {
file_put_contents($this->seedFile, json_encode(array($this->seed, microtime(true))));
}
$this->seedUpdated = true;
}
}
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