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<?php
/**
* Random Number Generator
*
* PHP version 5
*
* Here's a short example of how to use this library:
* <code>
* <?php
* include 'vendor/autoload.php';
*
* echo bin2hex(\phpseclib3\Crypt\Random::string(8));
* ?>
* </code>
*
* @author Jim Wigginton <terrafrost@php.net>
* @copyright 2007 Jim Wigginton
* @license http://www.opensource.org/licenses/mit-license.html MIT License
* @link http://phpseclib.sourceforge.net
*/
namespace phpseclib3\Crypt;
/**
* Pure-PHP Random Number Generator
*
* @author Jim Wigginton <terrafrost@php.net>
*/
abstract class Random
{
/**
* Generate a random string.
*
* Although microoptimizations are generally discouraged as they impair readability this function is ripe with
* microoptimizations because this function has the potential of being called a huge number of times.
* eg. for RSA key generation.
*
* @param int $length
* @throws \RuntimeException if a symmetric cipher is needed but not loaded
* @return string
*/
public static function string($length)
{
if (!$length) {
return '';
}
try {
return random_bytes($length);
} catch (\Exception $e) {
// random_compat will throw an Exception, which in PHP 5 does not implement Throwable
} catch (\Throwable $e) {
// If a sufficient source of randomness is unavailable, random_bytes() will throw an
// object that implements the Throwable interface (Exception, TypeError, Error).
// We don't actually need to do anything here. The string() method should just continue
// as normal. Note, however, that if we don't have a sufficient source of randomness for
// random_bytes(), most of the other calls here will fail too, so we'll end up using
// the PHP implementation.
}
// at this point we have no choice but to use a pure-PHP CSPRNG
// cascade entropy across multiple PHP instances by fixing the session and collecting all
// environmental variables, including the previous session data and the current session
// data.
//
// mt_rand seeds itself by looking at the PID and the time, both of which are (relatively)
// easy to guess at. linux uses mouse clicks, keyboard timings, etc, as entropy sources, but
// PHP isn't low level to be able to use those as sources and on a web server there's not likely
// going to be a ton of keyboard or mouse action. web servers do have one thing that we can use
// however, a ton of people visiting the website. obviously you don't want to base your seeding
// solely on parameters a potential attacker sends but (1) not everything in $_SERVER is controlled
// by the user and (2) this isn't just looking at the data sent by the current user - it's based
// on the data sent by all users. one user requests the page and a hash of their info is saved.
// another user visits the page and the serialization of their data is utilized along with the
// server environment stuff and a hash of the previous http request data (which itself utilizes
// a hash of the session data before that). certainly an attacker should be assumed to have
// full control over his own http requests. he, however, is not going to have control over
// everyone's http requests.
static $crypto = false, $v;
if ($crypto === false) {
// save old session data
$old_session_id = session_id();
$old_use_cookies = ini_get('session.use_cookies');
$old_session_cache_limiter = session_cache_limiter();
$_OLD_SESSION = isset($_SESSION) ? $_SESSION : false;
if ($old_session_id != '') {
session_write_close();
}
session_id(1);
ini_set('session.use_cookies', 0);
session_cache_limiter('');
session_start();
$v = (isset($_SERVER) ? self::safe_serialize($_SERVER) : '') .
(isset($_POST) ? self::safe_serialize($_POST) : '') .
(isset($_GET) ? self::safe_serialize($_GET) : '') .
(isset($_COOKIE) ? self::safe_serialize($_COOKIE) : '') .
// as of PHP 8.1 $GLOBALS can't be accessed by reference, which eliminates
// the need for phpseclib_safe_serialize. see https://wiki.php.net/rfc/restrict_globals_usage
// for more info
(version_compare(PHP_VERSION, '8.1.0', '>=') ? serialize($GLOBALS) : self::safe_serialize($GLOBALS)) .
self::safe_serialize($_SESSION) .
self::safe_serialize($_OLD_SESSION);
$v = $seed = $_SESSION['seed'] = sha1($v, true);
if (!isset($_SESSION['count'])) {
$_SESSION['count'] = 0;
}
$_SESSION['count']++;
session_write_close();
// restore old session data
if ($old_session_id != '') {
session_id($old_session_id);
session_start();
ini_set('session.use_cookies', $old_use_cookies);
session_cache_limiter($old_session_cache_limiter);
} else {
if ($_OLD_SESSION !== false) {
$_SESSION = $_OLD_SESSION;
unset($_OLD_SESSION);
} else {
unset($_SESSION);
}
}
// in SSH2 a shared secret and an exchange hash are generated through the key exchange process.
// the IV client to server is the hash of that "nonce" with the letter A and for the encryption key it's the letter C.
// if the hash doesn't produce enough a key or an IV that's long enough concat successive hashes of the
// original hash and the current hash. we'll be emulating that. for more info see the following URL:
//
// http://tools.ietf.org/html/rfc4253#section-7.2
//
// see the is_string($crypto) part for an example of how to expand the keys
$key = sha1($seed . 'A', true);
$iv = sha1($seed . 'C', true);
// ciphers are used as per the nist.gov link below. also, see this link:
//
// http://en.wikipedia.org/wiki/Cryptographically_secure_pseudorandom_number_generator#Designs_based_on_cryptographic_primitives
switch (true) {
case class_exists('\phpseclib3\Crypt\AES'):
$crypto = new AES('ctr');
break;
case class_exists('\phpseclib3\Crypt\Twofish'):
$crypto = new Twofish('ctr');
break;
case class_exists('\phpseclib3\Crypt\Blowfish'):
$crypto = new Blowfish('ctr');
break;
case class_exists('\phpseclib3\Crypt\TripleDES'):
$crypto = new TripleDES('ctr');
break;
case class_exists('\phpseclib3\Crypt\DES'):
$crypto = new DES('ctr');
break;
case class_exists('\phpseclib3\Crypt\RC4'):
$crypto = new RC4();
break;
default:
throw new \RuntimeException(__CLASS__ . ' requires at least one symmetric cipher be loaded');
}
$crypto->setKey(substr($key, 0, $crypto->getKeyLength() >> 3));
$crypto->setIV(substr($iv, 0, $crypto->getBlockLength() >> 3));
$crypto->enableContinuousBuffer();
}
//return $crypto->encrypt(str_repeat("\0", $length));
// the following is based off of ANSI X9.31:
//
// http://csrc.nist.gov/groups/STM/cavp/documents/rng/931rngext.pdf
//
// OpenSSL uses that same standard for it's random numbers:
//
// http://www.opensource.apple.com/source/OpenSSL/OpenSSL-38/openssl/fips-1.0/rand/fips_rand.c
// (do a search for "ANS X9.31 A.2.4")
$result = '';
while (strlen($result) < $length) {
$i = $crypto->encrypt(microtime()); // strlen(microtime()) == 21
$r = $crypto->encrypt($i ^ $v); // strlen($v) == 20
$v = $crypto->encrypt($r ^ $i); // strlen($r) == 20
$result .= $r;
}
return substr($result, 0, $length);
}
/**
* Safely serialize variables
*
* If a class has a private __sleep() it'll emit a warning
* @return mixed
* @param mixed $arr
*/
private static function safe_serialize(&$arr)
{
if (is_object($arr)) {
return '';
}
if (!is_array($arr)) {
return serialize($arr);
}
// prevent circular array recursion
if (isset($arr['__phpseclib_marker'])) {
return '';
}
$safearr = [];
$arr['__phpseclib_marker'] = true;
foreach (array_keys($arr) as $key) {
// do not recurse on the '__phpseclib_marker' key itself, for smaller memory usage
if ($key !== '__phpseclib_marker') {
$safearr[$key] = self::safe_serialize($arr[$key]);
}
}
unset($arr['__phpseclib_marker']);
return serialize($safearr);
}
}
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