< @license http://www.opensource.org/licenses/mit-license.html MIT License * @link http://phpseclib.sourceforge.net */ n * * 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 (!$length) { return ''; } i // If a sufficient source of randomness is unavailable, random_bytes() will throw an // object that implements the Throwable interface (Exception, TypeError, Error). // We don't actually need to do anything here. The string() method should just continue // as normal. Note, however, that if we don't have a sufficient source of randomness for // random_bytes(), most of the other calls here will fail too, so we'll end up using // the PHP implementation. } } if (strtoupper(substr(PHP_OS, 0, 3)) === 'WIN') { // method 1. prior to PHP 5.3 this would call rand() on windows hence the function_exists('class_alias') call. // ie. class_alias is a function that was introduced in PHP 5.3 if (extension_loaded('mcrypt') && function_exists('class_alias')) { return @mcrypt_create_iv($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 , "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); } // 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'); 1 // 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 // // 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; // // 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')) { * * 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) { // 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]);