PHP: Autentication and Access Control in a modular web application

Hello,

This example is about the access control and authentication on a modular web application, developed in Symfony2 using the EventDispatcher, the logic of implementation can be used in different projects, that don’t necessarily use these tools. The basis of this access control is the usage of a main event dispatcher and listener (EventDriven) to detect destination request address and intercept it before it reaches that destination (controller + method ).

I first became aware of the idea of using Events to control access, I believe it was by on his blog a long time ago.

Anyway here I describe the usage of a Symfony2  custom EventListener to listen to a onKernelRequest

This usually happens this way:

Client -[call]-> Webserver -[dispatch event request]-> triggers onKernelRequest witch does validation -[Validates]-> if passes code continues normally inside symfony2  … Get the idea? I hope so.

First I implemented the interface in the AccessControl Class no other code will interact with this that’s the beauty of using a event for access control, you can have the event manage the control access of all modules without having to interact directly with them. The code is commented for easier reading…

Class AccessControl implements EventSubscriberInterface

public function __construct($em, $dispatcher, $security, $router)
{
$this->em = $em; // the EntityManager not used in this demo
$this->dispatcher = $dispatcher; // The SF2 EventDispatcher
$this->security = $security; // security.context
$this->router = $router; // router to know where the request is going to
}

And of course I will be listening to onKernelRequest events

public static function getSubscribedEvents()
{
return array(
KernelEvents::REQUEST => [‘onKernelRequest’, 0],
);
}

Here follows an example on access control without any dynamic database support

This is a basic decision path based on the destination route using the symfony name and the request from the client.

public function onKernelRequest($event)
{
if ($event->getRequestType() != HttpKernelInterface::MASTER_REQUEST) {
return null; // will only be handled if it’s from a external request else returns null
}

$user = $this->security->getToken()->getUser();  // get the current user information
$request = $event->getRequest(); // get the current request
$requested_uri = $request->getRequestUri(); // get the requested URI
$internal_route = $request->get(‘_route’); // this what is used to validate access

// $internal_route has the route name used by symfony witch I use to compare since it’s simpler

if ($internal_route == ‘fos_user_registration_register’) {
return true; // by default I allow the call to the registering of a new user
}

if ($user == ‘anon.’) {
$mainrequest = $event->getRequest();
// Matched route
$_route = $mainrequest->attributes->get(‘_route’);
// Matched controller
$_controller = $mainrequest->attributes->get(‘_controller’);
// All route parameters including the `_controller`
$params = $mainrequest->attributes->get(‘_route_params’);

if ($_route != ‘fos_user_security_login’) {

// if anonymous is not trying to login
// send him to login
$url = $this->router->generate(‘fos_user_security_login’);
$response = new RedirectResponse($url);
$event->setResponse($response);
}
return;
}

if ($user->hasGroup(“Admin”)) {
return true; // if the user has a group admin allow him to everywhere
}

$request = $event->getRequest();
$requested_uri = $request->getRequestUri();
$internal_route = $request->get(‘_route’); // this is what is used to validate access

if (mb_substr($internal_route, 0, mb_strlen(“lab_”)) == “lab_”) {
if ($user->hasGroup(“Laboratorio”)) {

// allow user to space _lab if he’s from the Group Laboratorio
return true;
} else {
// monolog here
throw new \Exception(“Unauthorized access. $internal_route”);
}
}

if (mb_substr($internal_route, 0, mb_strlen(“stock”)) == “stock”) {
if ($user->hasGroup(“Stock”)) {

// allow the user to access stock route names if he his in the stock Group
return true;
} else {
// monolog here
throw new \Exception(“Unauthorized access. $internal_route”);
}
}

if (mb_substr($internal_route, 0, mb_strlen(“user”)) == “user”) {
if ($user->hasGroup(“Admin”)) {

  // if the user is admin allow him to manage users
return true;
} else {
// monolog here
throw new \Exception(“Unauthorized access. $internal_route”);
}
}

}

After this, configure the services.xml file in Resources/config/  this will allow for the dependencies to be loaded in the object.

security.context provides information about the user logged (or not), router allow’s to generate a different destination route for the Event

In this gist you can see all the code used.

Best regards,

Sobre Fernando André
SysAdmin, Website and Application Developer

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