gistfile1.php

<?php

use Symfony\Component\HttpFoundation\Request;
use Symfony\Component\HttpKernel\HttpKernelInterface;

class Csp implements HttpKernelInterface
{
    private $app;
    private $options;

    public function __construct(HttpKernelInterface $app, array $options)
    {
        $this->app = $app;
        $this->options = $options;
    }

    public function handle(Request $request, $type = HttpKernelInterface::MASTER_REQUEST, $catch = true)
    {
        // validate incoming headers on $request
        ...
      
        $response = $this->app->handle($request, $type, $catch);
        
        // set correct headers on $response
        ...
        
        return $response
    }
}