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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(\phpseclib\Crypt\Random::string(8));

 * ?>

 * </code>

 *

 * @category  Crypt

 * @package   Random

 * @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 phpseclib\Crypt;

/**

 * Pure-PHP Random Number Generator

 *

 * @package Random

 * @author  Jim Wigginton <terrafrost@php.net>

 * @access  public

 */

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

     * @return string

     */

    static function string($length)

    {

        if (version_compare(PHP_VERSION, '7.0.0', '>=')) {

            try {

                return \random_bytes($length);

            } 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.

            }

        }

        if (strtoupper(substr(PHP_OS, 0, 3)) === 'WIN') {

            // method 1. prior to PHP 5.3 this would call rand() on windows hence the function_exists('class_alias') call.

            // ie. class_alias is a function that was introduced in PHP 5.3

            if (extension_loaded('mcrypt') && function_exists('class_alias')) {

                return mcrypt_create_iv($length);

            }

            // method 2. openssl_random_pseudo_bytes was introduced in PHP 5.3.0 but prior to PHP 5.3.4 there was,

            // to quote <http://php.net/ChangeLog-5.php#5.3.4>, "possible blocking behavior". as of 5.3.4

            // openssl_random_pseudo_bytes and mcrypt_create_iv do the exact same thing on Windows. ie. they both

            // call php_win32_get_random_bytes():

            //

            // https://github.com/php/php-src/blob/7014a0eb6d1611151a286c0ff4f2238f92c120d6/ext/openssl/openssl.c#L5008

            // https://github.com/php/php-src/blob/7014a0eb6d1611151a286c0ff4f2238f92c120d6/ext/mcrypt/mcrypt.c#L1392

            //

            // php_win32_get_random_bytes() is defined thusly:

            //

            // https://github.com/php/php-src/blob/7014a0eb6d1611151a286c0ff4f2238f92c120d6/win32/winutil.c#L80

            //

            // we're calling it, all the same, in the off chance that the mcrypt extension is not available

            if (extension_loaded('openssl') && version_compare(PHP_VERSION, '5.3.4', '>=')) {

                return openssl_random_pseudo_bytes($length);

            }

        } else {

            // method 1. the fastest

            if (extension_loaded('openssl')) {

                return openssl_random_pseudo_bytes($length);

            }

            // method 2

            static $fp = true;

            if ($fp === true) {

                // warning's will be output unles the error suppression operator is used. errors such as

                // "open_basedir restriction in effect", "Permission denied", "No such file or directory", etc.

                $fp = @fopen('/dev/urandom', 'rb');

            }

            if ($fp !== true && $fp !== false) { // surprisingly faster than !is_bool() or is_resource()

                return fread($fp, $length);

            }

            // method 3. pretty much does the same thing as method 2 per the following url:

            // https://github.com/php/php-src/blob/7014a0eb6d1611151a286c0ff4f2238f92c120d6/ext/mcrypt/mcrypt.c#L1391

            // surprisingly slower than method 2. maybe that's because mcrypt_create_iv does a bunch of error checking that we're

            // not doing. regardless, this'll only be called if this PHP script couldn't open /dev/urandom due to open_basedir

            // restrictions or some such

            if (extension_loaded('mcrypt')) {

                return mcrypt_create_iv($length, MCRYPT_DEV_URANDOM);

            }

        }

        // 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

        // soley 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 envirnment 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 = $seed = $_SESSION['seed'] = pack('H*', sha1(

                (isset($_SERVER) ? phpseclib_safe_serialize($_SERVER) : '') .

                (isset($_POST) ? phpseclib_safe_serialize($_POST) : '') .

                (isset($_GET) ? phpseclib_safe_serialize($_GET) : '') .

                (isset($_COOKIE) ? phpseclib_safe_serialize($_COOKIE) : '') .

                phpseclib_safe_serialize($GLOBALS) .

                phpseclib_safe_serialize($_SESSION) .

                phpseclib_safe_serialize($_OLD_SESSION)

            ));

            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

            $key = pack('H*', sha1($seed . 'A'));

            $iv = pack('H*', sha1($seed . 'C'));

            // 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('\phpseclib\Crypt\AES'):

                    $crypto = new AES(Base::MODE_CTR);

                    break;

                case class_exists('\phpseclib\Crypt\Twofish'):

                    $crypto = new Twofish(Base::MODE_CTR);

                    break;

                case class_exists('\phpseclib\Crypt\Blowfish'):

                    $crypto = new Blowfish(Base::MODE_CTR);

                    break;

                case class_exists('\phpseclib\Crypt\TripleDES'):

                    $crypto = new TripleDES(Base::MODE_CTR);

                    break;

                case class_exists('\phpseclib\Crypt\DES'):

                    $crypto = new DES(Base::MODE_CTR);

                    break;

                case class_exists('\phpseclib\Crypt\RC4'):

                    $crypto = new RC4();

                    break;

                default:

                    user_error(__CLASS__ . ' requires at least one symmetric cipher be loaded');

                    return false;

            }

            $crypto->setKey($key);

            $crypto->setIV($iv);

            $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);

    }

}

if (!function_exists('phpseclib_safe_serialize')) {

    /**

     * Safely serialize variables

     *

     * If a class has a private __sleep() method it'll give a fatal error on PHP 5.2 and earlier.

     * PHP 5.3 will emit a warning.

     *

     * @param mixed $arr

     * @access public

     */

    function phpseclib_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 = array();

        $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] = phpseclib_safe_serialize($arr[$key]);

            }

        }

        unset($arr['__phpseclib_marker']);

        return serialize($safearr);

    }

}