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(\phpseclib3\Crypt\Random::string(8));
14 * ?>
15 * </code>
16 *
17 * @author    Jim Wigginton <terrafrost@php.net>
18 * @copyright 2007 Jim Wigginton
19 * @license   http://www.opensource.org/licenses/mit-license.html  MIT License
20 * @link      http://phpseclib.sourceforge.net
21 */
22
23namespace phpseclib3\Crypt;
24
25/**
26 * Pure-PHP Random Number Generator
27 *
28 * @author  Jim Wigginton <terrafrost@php.net>
29 */
30abstract class Random
31{
32    /**
33     * Generate a random string.
34     *
35     * Although microoptimizations are generally discouraged as they impair readability this function is ripe with
36     * microoptimizations because this function has the potential of being called a huge number of times.
37     * eg. for RSA key generation.
38     *
39     * @param int $length
40     * @throws \RuntimeException if a symmetric cipher is needed but not loaded
41     * @return string
42     */
43    public static function string($length)
44    {
45        if (!$length) {
46            return '';
47        }
48
49        try {
50            return random_bytes($length);
51        } catch (\Exception $e) {
52            // random_compat will throw an Exception, which in PHP 5 does not implement Throwable
53        } catch (\Throwable $e) {
54            // If a sufficient source of randomness is unavailable, random_bytes() will throw an
55            // object that implements the Throwable interface (Exception, TypeError, Error).
56            // We don't actually need to do anything here. The string() method should just continue
57            // as normal. Note, however, that if we don't have a sufficient source of randomness for
58            // random_bytes(), most of the other calls here will fail too, so we'll end up using
59            // the PHP implementation.
60        }
61        // at this point we have no choice but to use a pure-PHP CSPRNG
62
63        // cascade entropy across multiple PHP instances by fixing the session and collecting all
64        // environmental variables, including the previous session data and the current session
65        // data.
66        //
67        // mt_rand seeds itself by looking at the PID and the time, both of which are (relatively)
68        // easy to guess at. linux uses mouse clicks, keyboard timings, etc, as entropy sources, but
69        // PHP isn't low level to be able to use those as sources and on a web server there's not likely
70        // going to be a ton of keyboard or mouse action. web servers do have one thing that we can use
71        // however, a ton of people visiting the website. obviously you don't want to base your seeding
72        // solely on parameters a potential attacker sends but (1) not everything in $_SERVER is controlled
73        // by the user and (2) this isn't just looking at the data sent by the current user - it's based
74        // on the data sent by all users. one user requests the page and a hash of their info is saved.
75        // another user visits the page and the serialization of their data is utilized along with the
76        // server environment stuff and a hash of the previous http request data (which itself utilizes
77        // a hash of the session data before that). certainly an attacker should be assumed to have
78        // full control over his own http requests. he, however, is not going to have control over
79        // everyone's http requests.
80        static $crypto = false, $v;
81        if ($crypto === false) {
82            // save old session data
83            $old_session_id = session_id();
84            $old_use_cookies = ini_get('session.use_cookies');
85            $old_session_cache_limiter = session_cache_limiter();
86            $_OLD_SESSION = isset($_SESSION) ? $_SESSION : false;
87            if ($old_session_id != '') {
88                session_write_close();
89            }
90
91            session_id(1);
92            ini_set('session.use_cookies', 0);
93            session_cache_limiter('');
94            session_start();
95
96            $v = (isset($_SERVER) ? self::safe_serialize($_SERVER) : '') .
97                 (isset($_POST) ? self::safe_serialize($_POST) : '') .
98                 (isset($_GET) ? self::safe_serialize($_GET) : '') .
99                 (isset($_COOKIE) ? self::safe_serialize($_COOKIE) : '') .
100                 // as of PHP 8.1 $GLOBALS can't be accessed by reference, which eliminates
101                 // the need for phpseclib_safe_serialize. see https://wiki.php.net/rfc/restrict_globals_usage
102                 // for more info
103                 (version_compare(PHP_VERSION, '8.1.0', '>=') ? serialize($GLOBALS) : self::safe_serialize($GLOBALS)) .
104                 self::safe_serialize($_SESSION) .
105                 self::safe_serialize($_OLD_SESSION);
106            $v = $seed = $_SESSION['seed'] = sha1($v, true);
107            if (!isset($_SESSION['count'])) {
108                $_SESSION['count'] = 0;
109            }
110            $_SESSION['count']++;
111
112            session_write_close();
113
114            // restore old session data
115            if ($old_session_id != '') {
116                session_id($old_session_id);
117                session_start();
118                ini_set('session.use_cookies', $old_use_cookies);
119                session_cache_limiter($old_session_cache_limiter);
120            } else {
121                if ($_OLD_SESSION !== false) {
122                    $_SESSION = $_OLD_SESSION;
123                    unset($_OLD_SESSION);
124                } else {
125                    unset($_SESSION);
126                }
127            }
128
129            // in SSH2 a shared secret and an exchange hash are generated through the key exchange process.
130            // the IV client to server is the hash of that "nonce" with the letter A and for the encryption key it's the letter C.
131            // if the hash doesn't produce enough a key or an IV that's long enough concat successive hashes of the
132            // original hash and the current hash. we'll be emulating that. for more info see the following URL:
133            //
134            // http://tools.ietf.org/html/rfc4253#section-7.2
135            //
136            // see the is_string($crypto) part for an example of how to expand the keys
137            $key = sha1($seed . 'A', true);
138            $iv = sha1($seed . 'C', true);
139
140            // ciphers are used as per the nist.gov link below. also, see this link:
141            //
142            // http://en.wikipedia.org/wiki/Cryptographically_secure_pseudorandom_number_generator#Designs_based_on_cryptographic_primitives
143            switch (true) {
144                case class_exists('\phpseclib3\Crypt\AES'):
145                    $crypto = new AES('ctr');
146                    break;
147                case class_exists('\phpseclib3\Crypt\Twofish'):
148                    $crypto = new Twofish('ctr');
149                    break;
150                case class_exists('\phpseclib3\Crypt\Blowfish'):
151                    $crypto = new Blowfish('ctr');
152                    break;
153                case class_exists('\phpseclib3\Crypt\TripleDES'):
154                    $crypto = new TripleDES('ctr');
155                    break;
156                case class_exists('\phpseclib3\Crypt\DES'):
157                    $crypto = new DES('ctr');
158                    break;
159                case class_exists('\phpseclib3\Crypt\RC4'):
160                    $crypto = new RC4();
161                    break;
162                default:
163                    throw new \RuntimeException(__CLASS__ . ' requires at least one symmetric cipher be loaded');
164            }
165
166            $crypto->setKey(substr($key, 0, $crypto->getKeyLength() >> 3));
167            $crypto->setIV(substr($iv, 0, $crypto->getBlockLength() >> 3));
168            $crypto->enableContinuousBuffer();
169        }
170
171        //return $crypto->encrypt(str_repeat("\0", $length));
172
173        // the following is based off of ANSI X9.31:
174        //
175        // http://csrc.nist.gov/groups/STM/cavp/documents/rng/931rngext.pdf
176        //
177        // OpenSSL uses that same standard for it's random numbers:
178        //
179        // http://www.opensource.apple.com/source/OpenSSL/OpenSSL-38/openssl/fips-1.0/rand/fips_rand.c
180        // (do a search for "ANS X9.31 A.2.4")
181        $result = '';
182        while (strlen($result) < $length) {
183            $i = $crypto->encrypt(microtime()); // strlen(microtime()) == 21
184            $r = $crypto->encrypt($i ^ $v); // strlen($v) == 20
185            $v = $crypto->encrypt($r ^ $i); // strlen($r) == 20
186            $result .= $r;
187        }
188
189        return substr($result, 0, $length);
190    }
191
192    /**
193     * Safely serialize variables
194     *
195     * If a class has a private __sleep() it'll emit a warning
196     * @return mixed
197     * @param mixed $arr
198     */
199    private static function safe_serialize(&$arr)
200    {
201        if (is_object($arr)) {
202            return '';
203        }
204        if (!is_array($arr)) {
205            return serialize($arr);
206        }
207        // prevent circular array recursion
208        if (isset($arr['__phpseclib_marker'])) {
209            return '';
210        }
211        $safearr = [];
212        $arr['__phpseclib_marker'] = true;
213        foreach (array_keys($arr) as $key) {
214            // do not recurse on the '__phpseclib_marker' key itself, for smaller memory usage
215            if ($key !== '__phpseclib_marker') {
216                $safearr[$key] = self::safe_serialize($arr[$key]);
217            }
218        }
219        unset($arr['__phpseclib_marker']);
220        return serialize($safearr);
221    }
222}
223