web/Zend/OpenId.php
changeset 0 4eba9c11703f
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/web/Zend/OpenId.php	Mon Dec 13 18:29:26 2010 +0100
@@ -0,0 +1,753 @@
+<?php
+
+/**
+ * Zend Framework
+ *
+ * LICENSE
+ *
+ * This source file is subject to the new BSD license that is bundled
+ * with this package in the file LICENSE.txt.
+ * It is also available through the world-wide-web at this URL:
+ * http://framework.zend.com/license/new-bsd
+ * If you did not receive a copy of the license and are unable to
+ * obtain it through the world-wide-web, please send an email
+ * to license@zend.com so we can send you a copy immediately.
+ *
+ * @category   Zend
+ * @package    Zend_OpenId
+ * @copyright  Copyright (c) 2005-2010 Zend Technologies USA Inc. (http://www.zend.com)
+ * @license    http://framework.zend.com/license/new-bsd     New BSD License
+ * @version    $Id: OpenId.php 22653 2010-07-22 18:41:39Z mabe $
+ */
+
+/**
+ * @see Zend_Controller_Response_Abstract
+ */
+require_once "Zend/Controller/Response/Abstract.php";
+
+/**
+ * Static class that contains common utility functions for
+ * {@link Zend_OpenId_Consumer} and {@link Zend_OpenId_Provider}.
+ *
+ * This class implements common utility functions that are used by both
+ * Consumer and Provider. They include functions for Diffie-Hellman keys
+ * generation and exchange, URL normalization, HTTP redirection and some others.
+ *
+ * @category   Zend
+ * @package    Zend_OpenId
+ * @copyright  Copyright (c) 2005-2010 Zend Technologies USA Inc. (http://www.zend.com)
+ * @license    http://framework.zend.com/license/new-bsd     New BSD License
+ */
+class Zend_OpenId
+{
+    /**
+     * Default Diffie-Hellman key generator (1024 bit)
+     */
+    const DH_P   = 'dcf93a0b883972ec0e19989ac5a2ce310e1d37717e8d9571bb7623731866e61ef75a2e27898b057f9891c2e27a639c3f29b60814581cd3b2ca3986d2683705577d45c2e7e52dc81c7a171876e5cea74b1448bfdfaf18828efd2519f14e45e3826634af1949e5b535cc829a483b8a76223e5d490a257f05bdff16f2fb22c583ab';
+
+    /**
+     * Default Diffie-Hellman prime number (should be 2 or 5)
+     */
+    const DH_G   = '02';
+
+    /**
+     * OpenID 2.0 namespace. All OpenID 2.0 messages MUST contain variable
+     * openid.ns with its value.
+     */
+    const NS_2_0 = 'http://specs.openid.net/auth/2.0';
+
+    /**
+     * Allows enable/disable stoping execution of PHP script after redirect()
+     */
+    static public $exitOnRedirect = true;
+
+    /**
+     * Alternative request URL that can be used to override the default
+     * selfUrl() response
+     */
+    static public $selfUrl = null;
+
+    /**
+     * Sets alternative request URL that can be used to override the default
+     * selfUrl() response
+     *
+     * @param string $selfUrl the URL to be set
+     * @return string the old value of overriding URL
+     */
+    static public function setSelfUrl($selfUrl = null)
+    {
+        $ret = self::$selfUrl;
+        self::$selfUrl = $selfUrl;
+        return $ret;
+    }
+
+    /**
+     * Returns a full URL that was requested on current HTTP request.
+     *
+     * @return string
+     */
+    static public function selfUrl()
+    {
+        if (self::$selfUrl !== null) {
+            return self::$selfUrl;
+        } if (isset($_SERVER['SCRIPT_URI'])) {
+            return $_SERVER['SCRIPT_URI'];
+        }
+        $url = '';
+        $port = '';
+        if (isset($_SERVER['HTTP_HOST'])) {
+            if (($pos = strpos($_SERVER['HTTP_HOST'], ':')) === false) {
+                if (isset($_SERVER['SERVER_PORT'])) {
+                    $port = ':' . $_SERVER['SERVER_PORT'];
+                }
+                $url = $_SERVER['HTTP_HOST'];
+            } else {
+                $url = substr($_SERVER['HTTP_HOST'], 0, $pos);
+                $port = substr($_SERVER['HTTP_HOST'], $pos);
+            }
+        } else if (isset($_SERVER['SERVER_NAME'])) {
+            $url = $_SERVER['SERVER_NAME'];
+            if (isset($_SERVER['SERVER_PORT'])) {
+                $port = ':' . $_SERVER['SERVER_PORT'];
+            }
+        }
+        if (isset($_SERVER['HTTPS']) && $_SERVER['HTTPS'] == 'on') {
+            $url = 'https://' . $url;
+            if ($port == ':443') {
+                $port = '';
+            }
+        } else {
+            $url = 'http://' . $url;
+            if ($port == ':80') {
+                $port = '';
+            }
+        }
+
+        $url .= $port;
+        if (isset($_SERVER['HTTP_X_REWRITE_URL'])) {
+            $url .= $_SERVER['HTTP_X_REWRITE_URL'];
+        } elseif (isset($_SERVER['REQUEST_URI'])) {
+            $query = strpos($_SERVER['REQUEST_URI'], '?');
+            if ($query === false) {
+                $url .= $_SERVER['REQUEST_URI'];
+            } else {
+                $url .= substr($_SERVER['REQUEST_URI'], 0, $query);
+            }
+        } else if (isset($_SERVER['SCRIPT_URL'])) {
+            $url .= $_SERVER['SCRIPT_URL'];
+        } else if (isset($_SERVER['REDIRECT_URL'])) {
+            $url .= $_SERVER['REDIRECT_URL'];
+        } else if (isset($_SERVER['PHP_SELF'])) {
+            $url .= $_SERVER['PHP_SELF'];
+        } else if (isset($_SERVER['SCRIPT_NAME'])) {
+            $url .= $_SERVER['SCRIPT_NAME'];
+            if (isset($_SERVER['PATH_INFO'])) {
+                $url .= $_SERVER['PATH_INFO'];
+            }
+        }
+        return $url;
+    }
+
+    /**
+     * Returns an absolute URL for the given one
+     *
+     * @param string $url absilute or relative URL
+     * @return string
+     */
+    static public function absoluteUrl($url)
+    {
+        if (empty($url)) {
+            return Zend_OpenId::selfUrl();
+        } else if (!preg_match('|^([^:]+)://|', $url)) {
+            if (preg_match('|^([^:]+)://([^:@]*(?:[:][^@]*)?@)?([^/:@?#]*)(?:[:]([^/?#]*))?(/[^?]*)?((?:[?](?:[^#]*))?(?:#.*)?)$|', Zend_OpenId::selfUrl(), $reg)) {
+                $scheme = $reg[1];
+                $auth = $reg[2];
+                $host = $reg[3];
+                $port = $reg[4];
+                $path = $reg[5];
+                $query = $reg[6];
+                if ($url[0] == '/') {
+                    return $scheme
+                        . '://'
+                        . $auth
+                        . $host
+                        . (empty($port) ? '' : (':' . $port))
+                        . $url;
+                } else {
+                    $dir = dirname($path);
+                    return $scheme
+                        . '://'
+                        . $auth
+                        . $host
+                        . (empty($port) ? '' : (':' . $port))
+                        . (strlen($dir) > 1 ? $dir : '')
+                        . '/'
+                        . $url;
+                }
+            }
+        }
+        return $url;
+    }
+
+    /**
+     * Converts variable/value pairs into URL encoded query string
+     *
+     * @param array $params variable/value pairs
+     * @return string URL encoded query string
+     */
+    static public function paramsToQuery($params)
+    {
+        foreach($params as $key => $value) {
+            if (isset($query)) {
+                $query .= '&' . $key . '=' . urlencode($value);
+            } else {
+                $query = $key . '=' . urlencode($value);
+            }
+        }
+        return isset($query) ? $query : '';
+    }
+
+    /**
+     * Normalizes URL according to RFC 3986 to use it in comparison operations.
+     * The function gets URL argument by reference and modifies it.
+     * It returns true on success and false of failure.
+     *
+     * @param string &$id url to be normalized
+     * @return bool
+     */
+    static public function normalizeUrl(&$id)
+    {
+        // RFC 3986, 6.2.2.  Syntax-Based Normalization
+
+        // RFC 3986, 6.2.2.2 Percent-Encoding Normalization
+        $i = 0;
+        $n = strlen($id);
+        $res = '';
+        while ($i < $n) {
+            if ($id[$i] == '%') {
+                if ($i + 2 >= $n) {
+                    return false;
+                }
+                ++$i;
+                if ($id[$i] >= '0' && $id[$i] <= '9') {
+                    $c = ord($id[$i]) - ord('0');
+                } else if ($id[$i] >= 'A' && $id[$i] <= 'F') {
+                    $c = ord($id[$i]) - ord('A') + 10;
+                } else if ($id[$i] >= 'a' && $id[$i] <= 'f') {
+                    $c = ord($id[$i]) - ord('a') + 10;
+                } else {
+                    return false;
+                }
+                ++$i;
+                if ($id[$i] >= '0' && $id[$i] <= '9') {
+                    $c = ($c << 4) | (ord($id[$i]) - ord('0'));
+                } else if ($id[$i] >= 'A' && $id[$i] <= 'F') {
+                    $c = ($c << 4) | (ord($id[$i]) - ord('A') + 10);
+                } else if ($id[$i] >= 'a' && $id[$i] <= 'f') {
+                    $c = ($c << 4) | (ord($id[$i]) - ord('a') + 10);
+                } else {
+                    return false;
+                }
+                ++$i;
+                $ch = chr($c);
+                if (($ch >= 'A' && $ch <= 'Z') ||
+                    ($ch >= 'a' && $ch <= 'z') ||
+                    $ch == '-' ||
+                    $ch == '.' ||
+                    $ch == '_' ||
+                    $ch == '~') {
+                    $res .= $ch;
+                } else {
+                    $res .= '%';
+                    if (($c >> 4) < 10) {
+                        $res .= chr(($c >> 4) + ord('0'));
+                    } else {
+                        $res .= chr(($c >> 4) - 10 + ord('A'));
+                    }
+                    $c = $c & 0xf;
+                    if ($c < 10) {
+                        $res .= chr($c + ord('0'));
+                    } else {
+                        $res .= chr($c - 10 + ord('A'));
+                    }
+                }
+            } else {
+                $res .= $id[$i++];
+            }
+        }
+
+        if (!preg_match('|^([^:]+)://([^:@]*(?:[:][^@]*)?@)?([^/:@?#]*)(?:[:]([^/?#]*))?(/[^?#]*)?((?:[?](?:[^#]*))?)((?:#.*)?)$|', $res, $reg)) {
+            return false;
+        }
+        $scheme = $reg[1];
+        $auth = $reg[2];
+        $host = $reg[3];
+        $port = $reg[4];
+        $path = $reg[5];
+        $query = $reg[6];
+        $fragment = $reg[7]; /* strip it */
+
+        if (empty($scheme) || empty($host)) {
+            return false;
+        }
+
+        // RFC 3986, 6.2.2.1.  Case Normalization
+        $scheme = strtolower($scheme);
+        $host = strtolower($host);
+
+        // RFC 3986, 6.2.2.3.  Path Segment Normalization
+        if (!empty($path)) {
+            $i = 0;
+            $n = strlen($path);
+            $res = "";
+            while ($i < $n) {
+                if ($path[$i] == '/') {
+                    ++$i;
+                    while ($i < $n && $path[$i] == '/') {
+                        ++$i;
+                    }
+                    if ($i < $n && $path[$i] == '.') {
+                        ++$i;
+                        if ($i < $n && $path[$i] == '.') {
+                            ++$i;
+                            if ($i == $n || $path[$i] == '/') {
+                                if (($pos = strrpos($res, '/')) !== false) {
+                                    $res = substr($res, 0, $pos);
+                                }
+                            } else {
+                                    $res .= '/..';
+                            }
+                        } else if ($i != $n && $path[$i] != '/') {
+                            $res .= '/.';
+                        }
+                    } else {
+                        $res .= '/';
+                    }
+                } else {
+                    $res .= $path[$i++];
+                }
+            }
+            $path = $res;
+        }
+
+        // RFC 3986,6.2.3.  Scheme-Based Normalization
+        if ($scheme == 'http') {
+            if ($port == 80) {
+                $port = '';
+            }
+        } else if ($scheme == 'https') {
+            if ($port == 443) {
+                $port = '';
+            }
+        }
+        if (empty($path)) {
+            $path = '/';
+        }
+
+        $id = $scheme
+            . '://'
+            . $auth
+            . $host
+            . (empty($port) ? '' : (':' . $port))
+            . $path
+            . $query;
+        return true;
+    }
+
+    /**
+     * Normalizes OpenID identifier that can be URL or XRI name.
+     * Returns true on success and false of failure.
+     *
+     * Normalization is performed according to the following rules:
+     * 1. If the user's input starts with one of the "xri://", "xri://$ip*",
+     *    or "xri://$dns*" prefixes, they MUST be stripped off, so that XRIs
+     *    are used in the canonical form, and URI-authority XRIs are further
+     *    considered URL identifiers.
+     * 2. If the first character of the resulting string is an XRI Global
+     *    Context Symbol ("=", "@", "+", "$", "!"), then the input SHOULD be
+     *    treated as an XRI.
+     * 3. Otherwise, the input SHOULD be treated as an http URL; if it does
+     *    not include a "http" or "https" scheme, the Identifier MUST be
+     *    prefixed with the string "http://".
+     * 4. URL identifiers MUST then be further normalized by both following
+     *    redirects when retrieving their content and finally applying the
+     *    rules in Section 6 of [RFC3986] to the final destination URL.
+     * @param string &$id identifier to be normalized
+     * @return bool
+     */
+    static public function normalize(&$id)
+    {
+        $id = trim($id);
+        if (strlen($id) === 0) {
+            return true;
+        }
+
+        // 7.2.1
+        if (strpos($id, 'xri://$ip*') === 0) {
+            $id = substr($id, strlen('xri://$ip*'));
+        } else if (strpos($id, 'xri://$dns*') === 0) {
+            $id = substr($id, strlen('xri://$dns*'));
+        } else if (strpos($id, 'xri://') === 0) {
+            $id = substr($id, strlen('xri://'));
+        }
+
+        // 7.2.2
+        if ($id[0] == '=' ||
+            $id[0] == '@' ||
+            $id[0] == '+' ||
+            $id[0] == '$' ||
+            $id[0] == '!') {
+            return true;
+        }
+
+        // 7.2.3
+        if (strpos($id, "://") === false) {
+            $id = 'http://' . $id;
+        }
+
+        // 7.2.4
+        return self::normalizeURL($id);
+    }
+
+    /**
+     * Performs a HTTP redirection to specified URL with additional data.
+     * It may generate redirected request using GET or POST HTTP method.
+     * The function never returns.
+     *
+     * @param string $url URL to redirect to
+     * @param array $params additional variable/value pairs to send
+     * @param Zend_Controller_Response_Abstract $response
+     * @param string $method redirection method ('GET' or 'POST')
+     */
+    static public function redirect($url, $params = null,
+        Zend_Controller_Response_Abstract $response = null, $method = 'GET')
+    {
+        $url = Zend_OpenId::absoluteUrl($url);
+        $body = "";
+        if (null === $response) {
+            require_once "Zend/Controller/Response/Http.php";
+            $response = new Zend_Controller_Response_Http();
+        }
+
+        if ($method == 'POST') {
+            $body = "<html><body onLoad=\"document.forms[0].submit();\">\n";
+            $body .= "<form method=\"POST\" action=\"$url\">\n";
+            if (is_array($params) && count($params) > 0) {
+                foreach($params as $key => $value) {
+                    $body .= '<input type="hidden" name="' . $key . '" value="' . $value . "\">\n";
+                }
+            }
+            $body .= "<input type=\"submit\" value=\"Continue OpenID transaction\">\n";
+            $body .= "</form></body></html>\n";
+        } else if (is_array($params) && count($params) > 0) {
+            if (strpos($url, '?') === false) {
+                $url .= '?' . self::paramsToQuery($params);
+            } else {
+                $url .= '&' . self::paramsToQuery($params);
+            }
+        }
+        if (!empty($body)) {
+            $response->setBody($body);
+        } else if (!$response->canSendHeaders()) {
+            $response->setBody("<script language=\"JavaScript\"" .
+                 " type=\"text/javascript\">window.location='$url';" .
+                 "</script>");
+        } else {
+            $response->setRedirect($url);
+        }
+        $response->sendResponse();
+        if (self::$exitOnRedirect) {
+            exit();
+        }
+    }
+
+    /**
+     * Produces string of random byte of given length.
+     *
+     * @param integer $len length of requested string
+     * @return string RAW random binary string
+     */
+    static public function randomBytes($len)
+    {
+        $key = '';
+        for($i=0; $i < $len; $i++) {
+            $key .= chr(mt_rand(0, 255));
+        }
+        return $key;
+    }
+
+    /**
+     * Generates a hash value (message digest) according to given algorithm.
+     * It returns RAW binary string.
+     *
+     * This is a wrapper function that uses one of available internal function
+     * dependent on given PHP configuration. It may use various functions from
+     *  ext/openssl, ext/hash, ext/mhash or ext/standard.
+     *
+     * @param string $func digest algorithm
+     * @param string $data data to sign
+     * @return string RAW digital signature
+     * @throws Zend_OpenId_Exception
+     */
+    static public function digest($func, $data)
+    {
+        if (function_exists('openssl_digest')) {
+            return openssl_digest($data, $func, true);
+        } else if (function_exists('hash')) {
+            return hash($func, $data, true);
+        } else if ($func === 'sha1') {
+            return sha1($data, true);
+        } else if ($func === 'sha256') {
+            if (function_exists('mhash')) {
+                return mhash(MHASH_SHA256 , $data);
+            }
+        }
+        require_once "Zend/OpenId/Exception.php";
+        throw new Zend_OpenId_Exception(
+            'Unsupported digest algorithm "' . $func . '".',
+            Zend_OpenId_Exception::UNSUPPORTED_DIGEST);
+    }
+
+    /**
+     * Generates a keyed hash value using the HMAC method. It uses ext/hash
+     * if available or user-level PHP implementation, that is not significantly
+     * slower.
+     *
+     * @param string $macFunc name of selected hashing algorithm (sha1, sha256)
+     * @param string $data data to sign
+     * @param string $secret shared secret key used for generating the HMAC
+     *  variant of the message digest
+     * @return string RAW HMAC value
+     */
+    static public function hashHmac($macFunc, $data, $secret)
+    {
+//        require_once "Zend/Crypt/Hmac.php";
+//        return Zend_Crypt_Hmac::compute($secret, $macFunc, $data, Zend_Crypt_Hmac::BINARY);
+        if (function_exists('hash_hmac')) {
+            return hash_hmac($macFunc, $data, $secret, 1);
+        } else {
+            if (Zend_OpenId::strlen($secret) > 64) {
+                $secret = self::digest($macFunc, $secret);
+            }
+            $secret = str_pad($secret, 64, chr(0x00));
+            $ipad = str_repeat(chr(0x36), 64);
+            $opad = str_repeat(chr(0x5c), 64);
+            $hash1 = self::digest($macFunc, ($secret ^ $ipad) . $data);
+            return self::digest($macFunc, ($secret ^ $opad) . $hash1);
+        }
+    }
+
+    /**
+     * Converts binary representation into ext/gmp or ext/bcmath big integer
+     * representation.
+     *
+     * @param string $bin binary representation of big number
+     * @return mixed
+     * @throws Zend_OpenId_Exception
+     */
+    static protected function binToBigNum($bin)
+    {
+        if (extension_loaded('gmp')) {
+            return gmp_init(bin2hex($bin), 16);
+        } else if (extension_loaded('bcmath')) {
+            $bn = 0;
+            $len = Zend_OpenId::strlen($bin);
+            for ($i = 0; $i < $len; $i++) {
+                $bn = bcmul($bn, 256);
+                $bn = bcadd($bn, ord($bin[$i]));
+            }
+            return $bn;
+        }
+        require_once "Zend/OpenId/Exception.php";
+        throw new Zend_OpenId_Exception(
+            'The system doesn\'t have proper big integer extension',
+            Zend_OpenId_Exception::UNSUPPORTED_LONG_MATH);
+    }
+
+    /**
+     * Converts internal ext/gmp or ext/bcmath big integer representation into
+     * binary string.
+     *
+     * @param mixed $bn big number
+     * @return string
+     * @throws Zend_OpenId_Exception
+     */
+    static protected function bigNumToBin($bn)
+    {
+        if (extension_loaded('gmp')) {
+            $s = gmp_strval($bn, 16);
+            if (strlen($s) % 2 != 0) {
+                $s = '0' . $s;
+            } else if ($s[0] > '7') {
+                $s = '00' . $s;
+            }
+            return pack("H*", $s);
+        } else if (extension_loaded('bcmath')) {
+            $cmp = bccomp($bn, 0);
+            if ($cmp == 0) {
+                return "\0";
+            } else if ($cmp < 0) {
+                require_once "Zend/OpenId/Exception.php";
+                throw new Zend_OpenId_Exception(
+                    'Big integer arithmetic error',
+                    Zend_OpenId_Exception::ERROR_LONG_MATH);
+            }
+            $bin = "";
+            while (bccomp($bn, 0) > 0) {
+                $bin = chr(bcmod($bn, 256)) . $bin;
+                $bn = bcdiv($bn, 256);
+            }
+            if (ord($bin[0]) > 127) {
+                $bin = "\0" . $bin;
+            }
+            return $bin;
+        }
+        require_once "Zend/OpenId/Exception.php";
+        throw new Zend_OpenId_Exception(
+            'The system doesn\'t have proper big integer extension',
+            Zend_OpenId_Exception::UNSUPPORTED_LONG_MATH);
+    }
+
+    /**
+     * Performs the first step of a Diffie-Hellman key exchange by generating
+     * private and public DH values based on given prime number $p and
+     * generator $g. Both sides of key exchange MUST have the same prime number
+     * and generator. In this case they will able to create a random shared
+     * secret that is never send from one to the other.
+     *
+     * @param string $p prime number in binary representation
+     * @param string $g generator in binary representation
+     * @param string $priv_key private key in binary representation
+     * @return mixed
+     */
+    static public function createDhKey($p, $g, $priv_key = null)
+    {
+        if (function_exists('openssl_dh_compute_key')) {
+            $dh_details = array(
+                    'p' => $p,
+                    'g' => $g
+                );
+            if ($priv_key !== null) {
+                $dh_details['priv_key'] = $priv_key;
+            }
+            return openssl_pkey_new(array('dh'=>$dh_details));
+        } else {
+            $bn_p        = self::binToBigNum($p);
+            $bn_g        = self::binToBigNum($g);
+            if ($priv_key === null) {
+                $priv_key    = self::randomBytes(Zend_OpenId::strlen($p));
+            }
+            $bn_priv_key = self::binToBigNum($priv_key);
+            if (extension_loaded('gmp')) {
+                $bn_pub_key  = gmp_powm($bn_g, $bn_priv_key, $bn_p);
+            } else if (extension_loaded('bcmath')) {
+                $bn_pub_key  = bcpowmod($bn_g, $bn_priv_key, $bn_p);
+            }
+            $pub_key     = self::bigNumToBin($bn_pub_key);
+
+            return array(
+                'p'        => $bn_p,
+                'g'        => $bn_g,
+                'priv_key' => $bn_priv_key,
+                'pub_key'  => $bn_pub_key,
+                'details'  => array(
+                    'p'        => $p,
+                    'g'        => $g,
+                    'priv_key' => $priv_key,
+                    'pub_key'  => $pub_key));
+        }
+    }
+
+    /**
+     * Returns an associative array with Diffie-Hellman key components in
+     * binary representation. The array includes original prime number 'p' and
+     * generator 'g', random private key 'priv_key' and corresponding public
+     * key 'pub_key'.
+     *
+     * @param mixed $dh Diffie-Hellman key
+     * @return array
+     */
+    static public function getDhKeyDetails($dh)
+    {
+        if (function_exists('openssl_dh_compute_key')) {
+            $details = openssl_pkey_get_details($dh);
+            if (isset($details['dh'])) {
+                return $details['dh'];
+            }
+        } else {
+            return $dh['details'];
+        }
+    }
+
+    /**
+     * Computes the shared secret from the private DH value $dh and the other
+     * party's public value in $pub_key
+     *
+     * @param string $pub_key other party's public value
+     * @param mixed $dh Diffie-Hellman key
+     * @return string
+     * @throws Zend_OpenId_Exception
+     */
+    static public function computeDhSecret($pub_key, $dh)
+    {
+        if (function_exists('openssl_dh_compute_key')) {
+            $ret = openssl_dh_compute_key($pub_key, $dh);
+            if (ord($ret[0]) > 127) {
+                $ret = "\0" . $ret;
+            }
+            return $ret;
+        } else if (extension_loaded('gmp')) {
+            $bn_pub_key = self::binToBigNum($pub_key);
+            $bn_secret  = gmp_powm($bn_pub_key, $dh['priv_key'], $dh['p']);
+            return self::bigNumToBin($bn_secret);
+        } else if (extension_loaded('bcmath')) {
+            $bn_pub_key = self::binToBigNum($pub_key);
+            $bn_secret  = bcpowmod($bn_pub_key, $dh['priv_key'], $dh['p']);
+            return self::bigNumToBin($bn_secret);
+        }
+        require_once "Zend/OpenId/Exception.php";
+        throw new Zend_OpenId_Exception(
+            'The system doesn\'t have proper big integer extension',
+            Zend_OpenId_Exception::UNSUPPORTED_LONG_MATH);
+    }
+
+    /**
+     * Takes an arbitrary precision integer and returns its shortest big-endian
+     * two's complement representation.
+     *
+     * Arbitrary precision integers MUST be encoded as big-endian signed two's
+     * complement binary strings. Henceforth, "btwoc" is a function that takes
+     * an arbitrary precision integer and returns its shortest big-endian two's
+     * complement representation. All integers that are used with
+     * Diffie-Hellman Key Exchange are positive. This means that the left-most
+     * bit of the two's complement representation MUST be zero. If it is not,
+     * implementations MUST add a zero byte at the front of the string.
+     *
+     * @param string $str binary representation of arbitrary precision integer
+     * @return string big-endian signed representation
+     */
+    static public function btwoc($str)
+    {
+        if (ord($str[0]) > 127) {
+            return "\0" . $str;
+        }
+        return $str;
+    }
+
+    /**
+     * Returns lenght of binary string in bytes
+     *
+     * @param string $str
+     * @return int the string lenght
+     */
+    static public function strlen($str)
+    {
+        if (extension_loaded('mbstring') &&
+            (((int)ini_get('mbstring.func_overload')) & 2)) {
+            return mb_strlen($str, 'latin1');
+        } else {
+            return strlen($str);
+        }
+    }
+
+}