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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 $bytes random bytes
+ */
+ function getBytes($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 $chrs
+ */
+ function randomString($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;
+ }
+}
+
+?> \ No newline at end of file