class ReverseProxyMiddleware

class ReverseProxyMiddleware implements HttpKernelInterface {
    
    /**
     * The decorated kernel.
     *
     * @var \Symfony\Component\HttpKernel\HttpKernelInterface
     */
    protected $httpKernel;
    
    /**
     * The site settings.
     *
     * @var \Drupal\Core\Site\Settings
     */
    protected $settings;
    
    /**
     * Constructs a ReverseProxyMiddleware object.
     *
     * @param \Symfony\Component\HttpKernel\HttpKernelInterface $http_kernel
     *   The decorated kernel.
     * @param \Drupal\Core\Site\Settings $settings
     *   The site settings.
     */
    public function __construct(HttpKernelInterface $http_kernel, Settings $settings) {
        $this->httpKernel = $http_kernel;
        $this->settings = $settings;
    }
    
    /**
     * {@inheritdoc}
     */
    public function handle(Request $request, $type = self::MASTER_REQUEST, $catch = TRUE) {
        // Initialize proxy settings.
        static::setSettingsOnRequest($request, $this->settings);
        return $this->httpKernel
            ->handle($request, $type, $catch);
    }
    
    /**
     * Sets reverse proxy settings on Request object.
     *
     * @param \Symfony\Component\HttpFoundation\Request $request
     *   A Request instance.
     * @param \Drupal\Core\Site\Settings $settings
     *   The site settings.
     */
    public static function setSettingsOnRequest(Request $request, Settings $settings) {
        // Initialize proxy settings.
        if ($settings->get('reverse_proxy', FALSE)) {
            $proxies = $settings->get('reverse_proxy_addresses', []);
            if (count($proxies) > 0) {
                $deprecated_settings = [
                    'reverse_proxy_header' => Request::HEADER_X_FORWARDED_FOR,
                    'reverse_proxy_proto_header' => Request::HEADER_X_FORWARDED_PROTO,
                    'reverse_proxy_host_header' => Request::HEADER_X_FORWARDED_HOST,
                    'reverse_proxy_port_header' => Request::HEADER_X_FORWARDED_PORT,
                    'reverse_proxy_forwarded_header' => Request::HEADER_FORWARDED,
                ];
                $all = $settings->getAll();
                // Set the default value. This is the most relaxed setting possible and
                // not recommended for production.
                $trusted_header_set = Request::HEADER_X_FORWARDED_ALL | Request::HEADER_FORWARDED;
                foreach ($deprecated_settings as $deprecated_setting => $bit_value) {
                    if (array_key_exists($deprecated_setting, $all)) {
                        @trigger_error(sprintf("The '%s' setting in settings.php is deprecated in Drupal 8.7.0 and will be removed before Drupal 9.0.0. Use the 'reverse_proxy_trusted_headers' setting instead. See https://www.drupal.org/node/3030558", $deprecated_setting), E_USER_DEPRECATED);
                        $request::setTrustedHeaderName($bit_value, $all[$deprecated_setting]);
                        if ($all[$deprecated_setting] === NULL) {
                            // If the value is NULL do not trust the header.
                            $trusted_header_set &= ~$bit_value;
                        }
                    }
                }
                $request::setTrustedProxies($proxies, $settings->get('reverse_proxy_trusted_headers', $trusted_header_set));
            }
        }
    }

}