Jetpack::verify_xml_rpc_signature PHP Method

    function verify_xml_rpc_signature()
    {
        if ($this->xmlrpc_verification) {
            return $this->xmlrpc_verification;
        }
        // It's not for us
        if (!isset($_GET['token']) || empty($_GET['signature'])) {
            return false;
        }
        @(list($token_key, $version, $user_id) = explode(':', $_GET['token']));
        if (empty($token_key) || empty($version) || strval(JETPACK__API_VERSION) !== $version) {
            return false;
        }
        if ('0' === $user_id) {
            $token_type = 'blog';
            $user_id = 0;
        } else {
            $token_type = 'user';
            if (empty($user_id) || !ctype_digit($user_id)) {
                return false;
            }
            $user_id = (int) $user_id;
            $user = new WP_User($user_id);
            if (!$user || !$user->exists()) {
                return false;
            }
        }
        $token = Jetpack_Data::get_access_token($user_id);
        if (!$token) {
            return false;
        }
        $token_check = "{$token_key}.";
        if (!hash_equals(substr($token->secret, 0, strlen($token_check)), $token_check)) {
            return false;
        }
        require_once JETPACK__PLUGIN_DIR . 'class.jetpack-signature.php';
        $jetpack_signature = new Jetpack_Signature($token->secret, (int) Jetpack_Options::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 false;
        } else {
            if (is_wp_error($signature)) {
                return $signature;
            } else {
                if (!hash_equals($signature, $_GET['signature'])) {
                    return false;
                }
            }
        }
        $timestamp = (int) $_GET['timestamp'];
        $nonce = stripslashes((string) $_GET['nonce']);
        if (!$this->add_nonce($timestamp, $nonce)) {
            return false;
        }
        $this->xmlrpc_verification = array('type' => $token_type, 'user_id' => $token->external_user_id);
        return $this->xmlrpc_verification;
    }