Jetpack_Signature::sign_current_request PHP Method

    function sign_current_request($override = array())
    {
        if (isset($override['scheme'])) {
            $scheme = $override['scheme'];
            if (!in_array($scheme, array('http', 'https'))) {
                return new Jetpack_Error('invalid_sheme', 'Invalid URL scheme');
            }
        } else {
            if (is_ssl()) {
                $scheme = 'https';
            } else {
                $scheme = 'http';
            }
        }
        $host_port = isset($_SERVER['HTTP_X_FORWARDED_PORT']) ? $_SERVER['HTTP_X_FORWARDED_PORT'] : $_SERVER['SERVER_PORT'];
        if (is_ssl()) {
            // 443: Standard Port
            // 80: Assume we're behind a proxy without X-Forwarded-Port. Hardcoding "80" here means most sites
            //     with SSL termination proxies (self-served, Cloudflare, etc.) don't need to fiddle with
            //     the JETPACK_SIGNATURE__HTTPS_PORT constant. The code also implies we can't talk to a
            //     site at https://example.com:80/ (which would be a strange configuration).
            // JETPACK_SIGNATURE__HTTPS_PORT: Set this constant in wp-config.php to the back end webserver's port
            //                                if the site is behind a proxy running on port 443 without
            //                                X-Forwarded-Port and the back end's port is *not* 80. It's better,
            //                                though, to configure the proxy to send X-Forwarded-Port.
            $port = in_array($host_port, array(443, 80, JETPACK_SIGNATURE__HTTPS_PORT)) ? '' : $host_port;
        } else {
            // 80: Standard Port
            // JETPACK_SIGNATURE__HTTPS_PORT: Set this constant in wp-config.php to the back end webserver's port
            //                                if the site is behind a proxy running on port 80 without
            //                                X-Forwarded-Port. It's better, though, to configure the proxy to
            //                                send X-Forwarded-Port.
            $port = in_array($host_port, array(80, JETPACK_SIGNATURE__HTTP_PORT)) ? '' : $host_port;
        }
        $url = "{$scheme}://{$_SERVER['HTTP_HOST']}:{$port}" . stripslashes($_SERVER['REQUEST_URI']);
        if (array_key_exists('body', $override) && !is_null($override['body'])) {
            $body = $override['body'];
        } else {
            if ('POST' == strtoupper($_SERVER['REQUEST_METHOD'])) {
                $body = isset($GLOBALS['HTTP_RAW_POST_DATA']) ? $GLOBALS['HTTP_RAW_POST_DATA'] : null;
                // Convert the $_POST to the body, if the body was empty. This is how arrays are hashed
                // and encoded on the Jetpack side.
                if (defined('IS_WPCOM') && IS_WPCOM) {
                    if (empty($body) && is_array($_POST) && count($_POST) > 0) {
                        $body = $_POST;
                    }
                }
            } else {
                $body = null;
            }
        }
        $a = array();
        foreach (array('token', 'timestamp', 'nonce', 'body-hash') as $parameter) {
            if (isset($override[$parameter])) {
                $a[$parameter] = $override[$parameter];
            } else {
                $a[$parameter] = isset($_GET[$parameter]) ? stripslashes($_GET[$parameter]) : '';
            }
        }
        $method = isset($override['method']) ? $override['method'] : $_SERVER['REQUEST_METHOD'];
        return $this->sign_request($a['token'], $a['timestamp'], $a['nonce'], $a['body-hash'], $method, $url, $body, true);
    }

 /**
  * Authenticates XML-RPC and other requests from the Jetpack Server
  */
 function authenticate_jetpack($user, $username, $password)
 {
     if (is_a($user, 'WP_User')) {
         return $user;
     }
     // It's not for us
     if (!isset($_GET['token']) || empty($_GET['signature'])) {
         return $user;
     }
     @(list($token_key, $version, $user_id) = explode(':', $_GET['token']));
     if (empty($token_key) || empty($version) || strval(JETPACK__API_VERSION) !== $version || empty($user_id) || !ctype_digit($user_id) || !get_userdata($user_id)) {
         return $user;
     }
     $token = Jetpack_Data::get_access_token($user_id);
     if (!$token) {
         return $user;
     }
     if (0 !== strpos($token->secret, "{$token_key}.")) {
         return $user;
     }
     require_once dirname(__FILE__) . '/class.jetpack-signature.php';
     $jetpack_signature = new Jetpack_Signature($token->secret, (int) Jetpack::get_option('time_diff'));
     if (isset($_POST['_jetpack_is_multipart'])) {
         $post_data = $_POST;
         $file_hashes = array();
         foreach ($post_data as $post_data_key => $post_data_value) {
             if (0 !== strpos($post_data_key, '_jetpack_file_hmac_')) {
                 continue;
             }
             $post_data_key = substr($post_data_key, strlen('_jetpack_file_hmac_'));
             $file_hashes[$post_data_key] = $post_data_value;
         }
         foreach ($file_hashes as $post_data_key => $post_data_value) {
             unset($post_data["_jetpack_file_hmac_{$post_data_key}"]);
             $post_data[$post_data_key] = $post_data_value;
         }
         ksort($post_data);
         $body = http_build_query(stripslashes_deep($post_data));
     } elseif (is_null($this->HTTP_RAW_POST_DATA)) {
         $body = file_get_contents('php://input');
     } else {
         $body = null;
     }
     $signature = $jetpack_signature->sign_current_request(array('body' => is_null($body) ? $this->HTTP_RAW_POST_DATA : $body));
     if (!$signature) {
         return $user;
     } else {
         if (is_wp_error($signature)) {
             return $signature;
         } else {
             if ($signature !== $_GET['signature']) {
                 return $user;
             }
         }
     }
     $timestamp = (int) $_GET['timestamp'];
     $nonce = stripslashes((string) $_GET['nonce']);
     if (!$this->add_nonce($timestamp, $nonce)) {
         return $user;
     }
     nocache_headers();
     return new WP_User($token->external_user_id);
 }