/Ip/Lib/phpseclib/Crypt/Random.php

<?php

/* vim: set expandtab tabstop=4 shiftwidth=4 softtabstop=4: */



/**

 * Random Number Generator

 *

 * PHP versions 4 and 5

 *

 * Here's a short example of how to use this library:

 * <code>

 * <?php

 *    include('Crypt/Random.php');

 *

 *    echo bin2hex(crypt_random_string(8));

 * ?>

 * </code>

 *

 * LICENSE: Permission is hereby granted, free of charge, to any person obtaining a copy

 * of this software and associated documentation files (the "Software"), to deal

 * in the Software without restriction, including without limitation the rights

 * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell

 * copies of the Software, and to permit persons to whom the Software is

 * furnished to do so, subject to the following conditions:

 * 

 * The above copyright notice and this permission notice shall be included in

 * all copies or substantial portions of the Software.

 * 

 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR

 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,

 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE

 * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER

 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,

 * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN

 * THE SOFTWARE.

 *

 * @category   Crypt

 * @package    Crypt_Random

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

 * @copyright  MMVII Jim Wigginton

 * @license    http://www.opensource.org/licenses/mit-license.html  MIT License

 * @link       http://phpseclib.sourceforge.net

 */



/**

 * "Is Windows" test

 *

 * @access private

 */

define('CRYPT_RANDOM_IS_WINDOWS', strtoupper(substr(PHP_OS, 0, 3)) === 'WIN');



/**

 * 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 Integer $length

 * @return String

 * @access public

 */

function crypt_random_string($length)

{

    if (CRYPT_RANDOM_IS_WINDOWS) {

        // 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 (function_exists('mcrypt_create_iv') && 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 (function_exists('openssl_random_pseudo_bytes') && version_compare(PHP_VERSION, '5.3.4', '>=')) {

            return openssl_random_pseudo_bytes($length);

        }

    } else {

        // method 1. the fastest

        if (function_exists('openssl_random_pseudo_bytes')) {

            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 (function_exists('mcrypt_create_iv')) {

            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();

        if (isset($_SESSION)) {

            $_OLD_SESSION = $_SESSION;

        }

        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(

            serialize($_SERVER) .

            serialize($_POST) .

            serialize($_GET) .

            serialize($_COOKIE) .

            serialize($GLOBALS) .

            serialize($_SESSION) .

            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 (isset($_OLD_SESSION)) {

               $_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('Crypt_AES'):

                $crypto = new Crypt_AES(CRYPT_AES_MODE_CTR);

                break;

            case class_exists('Crypt_TripleDES'):

                $crypto = new Crypt_TripleDES(CRYPT_DES_MODE_CTR);

                break;

            case class_exists('Crypt_DES'):

                $crypto = new Crypt_DES(CRYPT_DES_MODE_CTR);

                break;

            case class_exists('Crypt_RC4'):

                $crypto = new Crypt_RC4();

                break;

            default:

                $crypto = $seed;

                return crypt_random_string($length);

        }



        $crypto->setKey($key);

        $crypto->setIV($iv);

        $crypto->enableContinuousBuffer();

    }



    if (is_string($crypto)) {

        // 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")

        //

        // ANSI X9.31 recommends ciphers be used and phpseclib does use them if they're available (see

        // later on in the code) but if they're not we'll use sha1

        $result = '';

        while (strlen($result) < $length) { // each loop adds 20 bytes

            // microtime() isn't packed as "densely" as it could be but then neither is that the idea.

            // the idea is simply to ensure that each "block" has a unique element to it.

            $i = pack('H*', sha1(microtime()));

            $r = pack('H*', sha1($i ^ $v));

            $v = pack('H*', sha1($r ^ $i));

            $result.= $r;

        }

        return substr($result, 0, $length);

    }



    //return $crypto->encrypt(str_repeat("\0", $length));



    $result = '';

    while (strlen($result) < $length) {

        $i = $crypto->encrypt(microtime());

        $r = $crypto->encrypt($i ^ $v);

        $v = $crypto->encrypt($r ^ $i);

        $result.= $r;

    }

    return substr($result, 0, $length);

}