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<?php
/**
* CryptUtil: A suite of wrapper utility functions for the OpenID
* library.
*
* PHP versions 4 and 5
*
* LICENSE: See the COPYING file included in this distribution.
*
* @access private
* @package OpenID
* @author JanRain, Inc. <openid@janrain.com>
* @copyright 2005-2008 Janrain, Inc.
* @license http://www.apache.org/licenses/LICENSE-2.0 Apache
*/
if (!defined('Auth_OpenID_RAND_SOURCE')) {
/**
* The filename for a source of random bytes. Define this yourself
* if you have a different source of randomness.
*/
define('Auth_OpenID_RAND_SOURCE', '/dev/urandom');
}
class Auth_OpenID_CryptUtil {
/**
* Get the specified number of random bytes.
*
* Attempts to use a cryptographically secure (not predictable)
* source of randomness if available. If there is no high-entropy
* randomness source available, it will fail. As a last resort,
* for non-critical systems, define
* <code>Auth_OpenID_RAND_SOURCE</code> as <code>null</code>, and
* the code will fall back on a pseudo-random number generator.
*
* @param int $num_bytes The length of the return value
* @return string $bytes random bytes
*/
static function getBytes($num_bytes)
{
static $f = null;
$bytes = '';
if ($f === null) {
if (Auth_OpenID_RAND_SOURCE === null) {
$f = false;
} else {
$f = @fopen(Auth_OpenID_RAND_SOURCE, "r");
if ($f === false) {
$msg = 'Define Auth_OpenID_RAND_SOURCE as null to ' .
' continue with an insecure random number generator.';
trigger_error($msg, E_USER_ERROR);
}
}
}
if ($f === false) {
// pseudorandom used
$bytes = '';
for ($i = 0; $i < $num_bytes; $i += 4) {
$bytes .= pack('L', mt_rand());
}
$bytes = substr($bytes, 0, $num_bytes);
} else {
$bytes = fread($f, $num_bytes);
}
return $bytes;
}
/**
* Produce a string of length random bytes, chosen from chrs. If
* $chrs is null, the resulting string may contain any characters.
*
* @param integer $length The length of the resulting
* randomly-generated string
* @param string $chrs A string of characters from which to choose
* to build the new string
* @return string $result A string of randomly-chosen characters
* from $chrs
*/
static function randomString($length, $population = null)
{
if ($population === null) {
return Auth_OpenID_CryptUtil::getBytes($length);
}
$popsize = strlen($population);
if ($popsize > 256) {
$msg = 'More than 256 characters supplied to ' . __FUNCTION__;
trigger_error($msg, E_USER_ERROR);
}
$duplicate = 256 % $popsize;
$str = "";
for ($i = 0; $i < $length; $i++) {
do {
$n = ord(Auth_OpenID_CryptUtil::getBytes(1));
} while ($n < $duplicate);
$n %= $popsize;
$str .= $population[$n];
}
return $str;
}
}
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