1<?php
2
3/**
4 * Random Number Generator
5 *
6 * PHP version 5
7 *
8 * Here's a short example of how to use this library:
9 * <code>
10 * <?php
11 *    include 'vendor/autoload.php';
12 *
13 *    echo bin2hex(\phpseclib\Crypt\Random::string(8));
14 * ?>
15 * </code>
16 *
17 * @category  Crypt
18 * @package   Random
19 * @author    Jim Wigginton <terrafrost@php.net>
20 * @copyright 2007 Jim Wigginton
21 * @license   http://www.opensource.org/licenses/mit-license.html  MIT License
22 * @link      http://phpseclib.sourceforge.net
23 */
24
25namespace phpseclib\Crypt;
26
27/**
28 * Pure-PHP Random Number Generator
29 *
30 * @package Random
31 * @author  Jim Wigginton <terrafrost@php.net>
32 * @access  public
33 */
34class Random
35{
36    /**
37     * Generate a random string.
38     *
39     * Although microoptimizations are generally discouraged as they impair readability this function is ripe with
40     * microoptimizations because this function has the potential of being called a huge number of times.
41     * eg. for RSA key generation.
42     *
43     * @param int $length
44     * @return string
45     */
46    static function string($length)
47    {
48        if (!$length) {
49            return '';
50        }
51
52        if (version_compare(PHP_VERSION, '7.0.0', '>=')) {
53            try {
54                return \random_bytes($length);
55            } catch (\Throwable $e) {
56                // If a sufficient source of randomness is unavailable, random_bytes() will throw an
57                // object that implements the Throwable interface (Exception, TypeError, Error).
58                // We don't actually need to do anything here. The string() method should just continue
59                // as normal. Note, however, that if we don't have a sufficient source of randomness for
60                // random_bytes(), most of the other calls here will fail too, so we'll end up using
61                // the PHP implementation.
62            }
63        }
64
65        if (strtoupper(substr(PHP_OS, 0, 3)) === 'WIN') {
66            // method 1. prior to PHP 5.3 this would call rand() on windows hence the function_exists('class_alias') call.
67            // ie. class_alias is a function that was introduced in PHP 5.3
68            if (extension_loaded('mcrypt') && function_exists('class_alias')) {
69                return @mcrypt_create_iv($length);
70            }
71            // method 2. openssl_random_pseudo_bytes was introduced in PHP 5.3.0 but prior to PHP 5.3.4 there was,
72            // to quote <http://php.net/ChangeLog-5.php#5.3.4>, "possible blocking behavior". as of 5.3.4
73            // openssl_random_pseudo_bytes and mcrypt_create_iv do the exact same thing on Windows. ie. they both
74            // call php_win32_get_random_bytes():
75            //
76            // https://github.com/php/php-src/blob/7014a0eb6d1611151a286c0ff4f2238f92c120d6/ext/openssl/openssl.c#L5008
77            // https://github.com/php/php-src/blob/7014a0eb6d1611151a286c0ff4f2238f92c120d6/ext/mcrypt/mcrypt.c#L1392
78            //
79            // php_win32_get_random_bytes() is defined thusly:
80            //
81            // https://github.com/php/php-src/blob/7014a0eb6d1611151a286c0ff4f2238f92c120d6/win32/winutil.c#L80
82            //
83            // we're calling it, all the same, in the off chance that the mcrypt extension is not available
84            if (extension_loaded('openssl') && version_compare(PHP_VERSION, '5.3.4', '>=')) {
85                return openssl_random_pseudo_bytes($length);
86            }
87        } else {
88            // method 1. the fastest
89            if (extension_loaded('openssl')) {
90                return openssl_random_pseudo_bytes($length);
91            }
92            // method 2
93            static $fp = true;
94            if ($fp === true) {
95                // warning's will be output unles the error suppression operator is used. errors such as
96                // "open_basedir restriction in effect", "Permission denied", "No such file or directory", etc.
97                $fp = @fopen('/dev/urandom', 'rb');
98            }
99            if ($fp !== true && $fp !== false) { // surprisingly faster than !is_bool() or is_resource()
100                $temp = fread($fp, $length);
101                if (strlen($temp) == $length) {
102                    return $temp;
103                }
104            }
105            // method 3. pretty much does the same thing as method 2 per the following url:
106            // https://github.com/php/php-src/blob/7014a0eb6d1611151a286c0ff4f2238f92c120d6/ext/mcrypt/mcrypt.c#L1391
107            // surprisingly slower than method 2. maybe that's because mcrypt_create_iv does a bunch of error checking that we're
108            // not doing. regardless, this'll only be called if this PHP script couldn't open /dev/urandom due to open_basedir
109            // restrictions or some such
110            if (extension_loaded('mcrypt')) {
111                return @mcrypt_create_iv($length, MCRYPT_DEV_URANDOM);
112            }
113        }
114        // at this point we have no choice but to use a pure-PHP CSPRNG
115
116        // cascade entropy across multiple PHP instances by fixing the session and collecting all
117        // environmental variables, including the previous session data and the current session
118        // data.
119        //
120        // mt_rand seeds itself by looking at the PID and the time, both of which are (relatively)
121        // easy to guess at. linux uses mouse clicks, keyboard timings, etc, as entropy sources, but
122        // PHP isn't low level to be able to use those as sources and on a web server there's not likely
123        // going to be a ton of keyboard or mouse action. web servers do have one thing that we can use
124        // however, a ton of people visiting the website. obviously you don't want to base your seeding
125        // soley on parameters a potential attacker sends but (1) not everything in $_SERVER is controlled
126        // by the user and (2) this isn't just looking at the data sent by the current user - it's based
127        // on the data sent by all users. one user requests the page and a hash of their info is saved.
128        // another user visits the page and the serialization of their data is utilized along with the
129        // server envirnment stuff and a hash of the previous http request data (which itself utilizes
130        // a hash of the session data before that). certainly an attacker should be assumed to have
131        // full control over his own http requests. he, however, is not going to have control over
132        // everyone's http requests.
133        static $crypto = false, $v;
134        if ($crypto === false) {
135            // save old session data
136            $old_session_id = session_id();
137            $old_use_cookies = ini_get('session.use_cookies');
138            $old_session_cache_limiter = session_cache_limiter();
139            $_OLD_SESSION = isset($_SESSION) ? $_SESSION : false;
140            if ($old_session_id != '') {
141                session_write_close();
142            }
143
144            session_id(1);
145            ini_set('session.use_cookies', 0);
146            session_cache_limiter('');
147            session_start();
148
149            $v = $seed = $_SESSION['seed'] = pack('H*', sha1(
150                (isset($_SERVER) ? phpseclib_safe_serialize($_SERVER) : '') .
151                (isset($_POST) ? phpseclib_safe_serialize($_POST) : '') .
152                (isset($_GET) ? phpseclib_safe_serialize($_GET) : '') .
153                (isset($_COOKIE) ? phpseclib_safe_serialize($_COOKIE) : '') .
154                // as of PHP 8.1 $GLOBALS can't be accessed by reference, which eliminates
155                // the need for phpseclib_safe_serialize. see https://wiki.php.net/rfc/restrict_globals_usage
156                // for more info
157                (version_compare(PHP_VERSION, '8.1.0', '>=') ? serialize($GLOBALS) : phpseclib_safe_serialize($GLOBALS)) .
158                phpseclib_safe_serialize($_SESSION) .
159                phpseclib_safe_serialize($_OLD_SESSION)
160            ));
161            if (!isset($_SESSION['count'])) {
162                $_SESSION['count'] = 0;
163            }
164            $_SESSION['count']++;
165
166            session_write_close();
167
168            // restore old session data
169            if ($old_session_id != '') {
170                session_id($old_session_id);
171                session_start();
172                ini_set('session.use_cookies', $old_use_cookies);
173                session_cache_limiter($old_session_cache_limiter);
174            } else {
175                if ($_OLD_SESSION !== false) {
176                    $_SESSION = $_OLD_SESSION;
177                    unset($_OLD_SESSION);
178                } else {
179                    unset($_SESSION);
180                }
181            }
182
183            // in SSH2 a shared secret and an exchange hash are generated through the key exchange process.
184            // the IV client to server is the hash of that "nonce" with the letter A and for the encryption key it's the letter C.
185            // if the hash doesn't produce enough a key or an IV that's long enough concat successive hashes of the
186            // original hash and the current hash. we'll be emulating that. for more info see the following URL:
187            //
188            // http://tools.ietf.org/html/rfc4253#section-7.2
189            //
190            // see the is_string($crypto) part for an example of how to expand the keys
191            $key = pack('H*', sha1($seed . 'A'));
192            $iv = pack('H*', sha1($seed . 'C'));
193
194            // ciphers are used as per the nist.gov link below. also, see this link:
195            //
196            // http://en.wikipedia.org/wiki/Cryptographically_secure_pseudorandom_number_generator#Designs_based_on_cryptographic_primitives
197            switch (true) {
198                case class_exists('\phpseclib\Crypt\AES'):
199                    $crypto = new AES(Base::MODE_CTR);
200                    break;
201                case class_exists('\phpseclib\Crypt\Twofish'):
202                    $crypto = new Twofish(Base::MODE_CTR);
203                    break;
204                case class_exists('\phpseclib\Crypt\Blowfish'):
205                    $crypto = new Blowfish(Base::MODE_CTR);
206                    break;
207                case class_exists('\phpseclib\Crypt\TripleDES'):
208                    $crypto = new TripleDES(Base::MODE_CTR);
209                    break;
210                case class_exists('\phpseclib\Crypt\DES'):
211                    $crypto = new DES(Base::MODE_CTR);
212                    break;
213                case class_exists('\phpseclib\Crypt\RC4'):
214                    $crypto = new RC4();
215                    break;
216                default:
217                    user_error(__CLASS__ . ' requires at least one symmetric cipher be loaded');
218                    return false;
219            }
220
221            $crypto->setKey($key);
222            $crypto->setIV($iv);
223            $crypto->enableContinuousBuffer();
224        }
225
226        //return $crypto->encrypt(str_repeat("\0", $length));
227
228        // the following is based off of ANSI X9.31:
229        //
230        // http://csrc.nist.gov/groups/STM/cavp/documents/rng/931rngext.pdf
231        //
232        // OpenSSL uses that same standard for it's random numbers:
233        //
234        // http://www.opensource.apple.com/source/OpenSSL/OpenSSL-38/openssl/fips-1.0/rand/fips_rand.c
235        // (do a search for "ANS X9.31 A.2.4")
236        $result = '';
237        while (strlen($result) < $length) {
238            $i = $crypto->encrypt(microtime()); // strlen(microtime()) == 21
239            $r = $crypto->encrypt($i ^ $v); // strlen($v) == 20
240            $v = $crypto->encrypt($r ^ $i); // strlen($r) == 20
241            $result.= $r;
242        }
243        return substr($result, 0, $length);
244    }
245}
246
247if (!function_exists('phpseclib_safe_serialize')) {
248    /**
249     * Safely serialize variables
250     *
251     * If a class has a private __sleep() method it'll give a fatal error on PHP 5.2 and earlier.
252     * PHP 5.3 will emit a warning.
253     *
254     * @param mixed $arr
255     * @access public
256     */
257    function phpseclib_safe_serialize(&$arr)
258    {
259        if (is_object($arr)) {
260            return '';
261        }
262        if (!is_array($arr)) {
263            return serialize($arr);
264        }
265        // prevent circular array recursion
266        if (isset($arr['__phpseclib_marker'])) {
267            return '';
268        }
269        $safearr = array();
270        $arr['__phpseclib_marker'] = true;
271        foreach (array_keys($arr) as $key) {
272            // do not recurse on the '__phpseclib_marker' key itself, for smaller memory usage
273            if ($key !== '__phpseclib_marker') {
274                $safearr[$key] = phpseclib_safe_serialize($arr[$key]);
275            }
276        }
277        unset($arr['__phpseclib_marker']);
278        return serialize($safearr);
279    }
280}
281