public function generateRandomKey($length = 32)
{
if (!is_int($length)) {
throw new InvalidParamException('First parameter ($length) must be an integer');
}
if ($length < 1) {
throw new InvalidParamException('First parameter ($length) must be greater than 0');
}
// always use random_bytes() if it is available
if (function_exists('random_bytes')) {
return random_bytes($length);
}
// The recent LibreSSL RNGs are faster and likely better than /dev/urandom.
// Parse OPENSSL_VERSION_TEXT because OPENSSL_VERSION_NUMBER is no use for LibreSSL.
// https://bugs.php.net/bug.php?id=71143
if ($this->_useLibreSSL === null) {
$this->_useLibreSSL = defined('OPENSSL_VERSION_TEXT') && preg_match('{^LibreSSL (\\d\\d?)\\.(\\d\\d?)\\.(\\d\\d?)$}', OPENSSL_VERSION_TEXT, $matches) && 10000 * $matches[1] + 100 * $matches[2] + $matches[3] >= 20105;
}
// Since 5.4.0, openssl_random_pseudo_bytes() reads from CryptGenRandom on Windows instead
// of using OpenSSL library. LibreSSL is OK everywhere but don't use OpenSSL on non-Windows.
if ($this->_useLibreSSL || DIRECTORY_SEPARATOR !== '/' && substr_compare(PHP_OS, 'win', 0, 3, true) === 0 && function_exists('openssl_random_pseudo_bytes')) {
$key = openssl_random_pseudo_bytes($length, $cryptoStrong);
if ($cryptoStrong === false) {
throw new Exception('openssl_random_pseudo_bytes() set $crypto_strong false. Your PHP setup is insecure.');
}
if ($key !== false && StringHelper::byteLength($key) === $length) {
return $key;
}
}
// mcrypt_create_iv() does not use libmcrypt. Since PHP 5.3.7 it directly reads
// CryptGenRandom on Windows. Elsewhere it directly reads /dev/urandom.
if (function_exists('mcrypt_create_iv')) {
$key = mcrypt_create_iv($length, MCRYPT_DEV_URANDOM);
if (StringHelper::byteLength($key) === $length) {
return $key;
}
}
// If not on Windows, try to open a random device.
if ($this->_randomFile === null && DIRECTORY_SEPARATOR === '/') {
// urandom is a symlink to random on FreeBSD.
$device = PHP_OS === 'FreeBSD' ? '/dev/random' : '/dev/urandom';
// Check random device for special character device protection mode. Use lstat()
// instead of stat() in case an attacker arranges a symlink to a fake device.
$lstat = @lstat($device);
if ($lstat !== false && ($lstat['mode'] & 0170000) === 020000) {
$this->_randomFile = fopen($device, 'rb') ?: null;
if (is_resource($this->_randomFile)) {
// Reduce PHP stream buffer from default 8192 bytes to optimize data
// transfer from the random device for smaller values of $length.
// This also helps to keep future randoms out of user memory space.
$bufferSize = 8;
if (function_exists('stream_set_read_buffer')) {
stream_set_read_buffer($this->_randomFile, $bufferSize);
}
// stream_set_read_buffer() isn't implemented on HHVM
if (function_exists('stream_set_chunk_size')) {
stream_set_chunk_size($this->_randomFile, $bufferSize);
}
}
}
}
if (is_resource($this->_randomFile)) {
$buffer = '';
$stillNeed = $length;
while ($stillNeed > 0) {
$someBytes = fread($this->_randomFile, $stillNeed);
if ($someBytes === false) {
break;
}
$buffer .= $someBytes;
$stillNeed -= StringHelper::byteLength($someBytes);
if ($stillNeed === 0) {
// Leaving file pointer open in order to make next generation faster by reusing it.
return $buffer;
}
}
fclose($this->_randomFile);
$this->_randomFile = null;
}
throw new Exception('Unable to generate a random key');
}