Using Symfony2's AccessDeniedHandlerInterface - security

Question

I am trying to get my security stuff setup for symfony2 and I have it working so far, but now I need to do some more fancy things. I am currently using everything dealing with PreAuthentication (I use a third party component for logging in and session management). That part is working great in tandem with the JMS security bundle.
Now I am to the point when I want to catch the users that are throwing 403s so I can just forward them to the login page of the third party component that I am using. I think my best bet is to add an exception handler to the exception listener. I am looking at the AccessDeniedHandlerInterface.
Is this the right direction for me to be going?
How do I add this handler to the exception listener?
EDIT:
I ended up doing something similar. I created a service that is prompted on the kernel.exception event. services.yml looks like this:
services:
kernel.listener.accessDenied:
class: Fully\Qualified\Namespace\Path\To\Class
tags:
- { name: kernel.event_listener, event: kernel.exception, method: onAccessDeniedException }
and the class it self:
<?php
namespace Fully\Qualified\Namespace\Path\To;
use Symfony\Component\HttpKernel\Event\GetResponseForExceptionEvent,
Symfony\Component\HttpFoundation\Response,
Symfony\Component\Security\Core\Exception\AccessDeniedException;
class Class
{
public function onAccessDeniedException(GetResponseForExceptionEvent $event)
{
$exception = $event->getException();
//Get the root cause of the exception.
while (null !== $exception->getPrevious()) {
$exception = $exception->getPrevious();
}
if ($exception instanceof AccessDeniedException) {
//Forward to third-party.
}
}
}

Answer 1

This sounds about right.
Or, if you're specifically interested in AccessDeniedException you could also define access_denied_handler within your firewall in security.yml:
security:
firewalls:
my_firewall:
# ...
access_denied_handler: kernel.listener.access_denied.handler
# ...
Then define your service in your services.xml or equivalent:
<parameters>
<parameter key="kernel.listener.security.class">Path\To\Your\Class</parameter>
</parameters>
<service id="kernel.listener.access_denied.handler" class="%kernel.listener.security.class%">
<tag name="kernel.event_listener" event="security.kernel_response" method="handle" />
</service>
The handler class:
use \Symfony\Component\Security\Http\Authorization\AccessDeniedHandlerInterface;
class MyAccessDeniedHandler implements AccessDeniedHandlerInterface
{
public function handle(Request $request, AccessDeniedException $accessDeniedException)
{
// do something with your exception and return Response object (plain message of rendered template)
}
}
You can find complete Security reference of Symfony2 here: http://symfony.com/doc/2.8/reference/configuration/security.html