Create a hash_pbkdf2 function if it doesn't exist yet

includes/misc.inc.php

@@ -176,4 +176,90 @@ function user_template_names() {
     return $templatenames;
 }
 
+
+
+/* This function was taken from https://gist.github.com/rsky/5104756 to make
+it available on older php versions. Thanks! */
+
+if (!function_exists(hash_pbkdf2)) {
+    function hash_pbkdf2($algo, $password, $salt, $iterations, $length = 0, $rawOutput = false) {
+        // check for hashing algorithm
+        if (!in_array(strtolower($algo), hash_algos())) {
+            trigger_error(sprintf(
+                '%s(): Unknown hashing algorithm: %s',
+                __FUNCTION__, $algo
+            ), E_USER_WARNING);
+            return false;
+        }
+
+        // check for type of iterations and length
+        foreach (array(4 => $iterations, 5 => $length) as $index => $value) {
+            if (!is_numeric($value)) {
+                trigger_error(sprintf(
+                    '%s() expects parameter %d to be long, %s given',
+                    __FUNCTION__, $index, gettype($value)
+                ), E_USER_WARNING);
+                return null;
+            }
+        }
+
+        // check iterations
+        $iterations = (int)$iterations;
+        if ($iterations <= 0) {
+            trigger_error(sprintf(
+                '%s(): Iterations must be a positive integer: %d',
+                __FUNCTION__, $iterations
+            ), E_USER_WARNING);
+            return false;
+        }
+
+        // check length
+        $length = (int)$length;
+        if ($length < 0) {
+            trigger_error(sprintf(
+                '%s(): Iterations must be greater than or equal to 0: %d',
+                __FUNCTION__, $length
+            ), E_USER_WARNING);
+            return false;
+        }
+
+        // check salt
+        if (strlen($salt) > PHP_INT_MAX - 4) {
+            trigger_error(sprintf(
+                '%s(): Supplied salt is too long, max of INT_MAX - 4 bytes: %d supplied',
+                __FUNCTION__, strlen($salt)
+            ), E_USER_WARNING);
+            return false;
+        }
+
+        // initialize
+        $derivedKey = '';
+        $loops = 1;
+        if ($length > 0) {
+            $loops = (int)ceil($length / strlen(hash($algo, '', $rawOutput)));
+        }
+
+        // hash for each blocks
+        for ($i = 1; $i <= $loops; $i++) {
+            $digest = hash_hmac($algo, $salt . pack('N', $i), $password, true);
+            $block = $digest;
+            for ($j = 1; $j < $iterations; $j++) {
+                $digest = hash_hmac($algo, $digest, $password, true);
+                $block ^= $digest;
+            }
+            $derivedKey .= $block;
+        }
+
+        if (!$rawOutput) {
+            $derivedKey = bin2hex($derivedKey);
+        }
+
+        if ($length > 0) {
+            return substr($derivedKey, 0, $length);
+        }
+
+        return $derivedKey;
+    }
+}
+
 ?>