Jetpack::verify_json_api_authorization_request PHP Method

    function verify_json_api_authorization_request()
    {
        require_once JETPACK__PLUGIN_DIR . 'class.jetpack-signature.php';
        $token = Jetpack_Data::get_access_token(JETPACK_MASTER_USER);
        if (!$token || empty($token->secret)) {
            wp_die(__('You must connect your Jetpack plugin to WordPress.com to use this feature.', 'jetpack'));
        }
        $die_error = __('Someone may be trying to trick you into giving them access to your site.  Or it could be you just encountered a bug :).  Either way, please close this window.', 'jetpack');
        $jetpack_signature = new Jetpack_Signature($token->secret, (int) Jetpack_Options::get_option('time_diff'));
        if (isset($_POST['jetpack_json_api_original_query'])) {
            $signature = $jetpack_signature->sign_request($_GET['token'], $_GET['timestamp'], $_GET['nonce'], '', 'GET', $_POST['jetpack_json_api_original_query'], null, true);
        } else {
            $signature = $jetpack_signature->sign_current_request(array('body' => null, 'method' => 'GET'));
        }
        if (!$signature) {
            wp_die($die_error);
        } else {
            if (is_wp_error($signature)) {
                wp_die($die_error);
            } else {
                if (!hash_equals($signature, $_GET['signature'])) {
                    if (is_ssl()) {
                        // If we signed an HTTP request on the Jetpack Servers, but got redirected to HTTPS by the local blog, check the HTTP signature as well
                        $signature = $jetpack_signature->sign_current_request(array('scheme' => 'http', 'body' => null, 'method' => 'GET'));
                        if (!$signature || is_wp_error($signature) || !hash_equals($signature, $_GET['signature'])) {
                            wp_die($die_error);
                        }
                    } else {
                        wp_die($die_error);
                    }
                }
            }
        }
        $timestamp = (int) $_GET['timestamp'];
        $nonce = stripslashes((string) $_GET['nonce']);
        if (!$this->add_nonce($timestamp, $nonce)) {
            // De-nonce the nonce, at least for 5 minutes.
            // We have to reuse this nonce at least once (used the first time when the initial request is made, used a second time when the login form is POSTed)
            $old_nonce_time = get_option("jetpack_nonce_{$timestamp}_{$nonce}");
            if ($old_nonce_time < time() - 300) {
                wp_die(__('The authorization process expired.  Please go back and try again.', 'jetpack'));
            }
        }
        $data = json_decode(base64_decode(stripslashes($_GET['data'])));
        $data_filters = array('state' => 'opaque', 'client_id' => 'int', 'client_title' => 'string', 'client_image' => 'url');
        foreach ($data_filters as $key => $sanitation) {
            if (!isset($data->{$key})) {
                wp_die($die_error);
            }
            switch ($sanitation) {
                case 'int':
                    $this->json_api_authorization_request[$key] = (int) $data->{$key};
                    break;
                case 'opaque':
                    $this->json_api_authorization_request[$key] = (string) $data->{$key};
                    break;
                case 'string':
                    $this->json_api_authorization_request[$key] = wp_kses((string) $data->{$key}, array());
                    break;
                case 'url':
                    $this->json_api_authorization_request[$key] = esc_url_raw((string) $data->{$key});
                    break;
            }
        }
        if (empty($this->json_api_authorization_request['client_id'])) {
            wp_die($die_error);
        }
    }