> Symfony 5 > Symfony 5 Security: Authenticators
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08.

Authentication Success & Refreshing the User

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Let's do a quick review of how our authenticator works. After activating it in security.yaml:

34 lines | config/packages/security.yaml
security:
// ... lines 2 - 13
firewalls:
// ... lines 15 - 17
main:
// ... lines 19 - 20
custom_authenticator: App\Security\LoginFormAuthenticator
// ... lines 22 - 34

Symfony calls our supports() method on every request before the controller:

75 lines | src/Security/LoginFormAuthenticator.php
// ... lines 1 - 17
class LoginFormAuthenticator extends AbstractAuthenticator
{
// ... lines 20 - 26
public function supports(Request $request): ?bool
{
return ($request->getPathInfo() === '/login' && $request->isMethod('POST'));
}
// ... lines 31 - 73
}

Since our authenticator knows how to handle the login form submit, we return true if the current request is a POST to /login. Once we return true, Symfony then calls authenticate() and basically asks:

Okay, tell me who is trying to log in and what proof they have.

We answer these questions by returning a Passport:

75 lines | src/Security/LoginFormAuthenticator.php
// ... lines 1 - 17
class LoginFormAuthenticator extends AbstractAuthenticator
{
// ... lines 20 - 31
public function authenticate(Request $request): PassportInterface
{
// ... lines 34 - 36
return new Passport(
new UserBadge($email, function($userIdentifier) {
// optionally pass a callback to load the User manually
$user = $this->userRepository->findOneBy(['email' => $userIdentifier]);
if (!$user) {
throw new UserNotFoundException();
}
return $user;
}),
new CustomCredentials(function($credentials, User $user) {
return $credentials === 'tada';
}, $password)
);
}
// ... lines 53 - 73
}

The first argument identifies the user and the second argument identifies some proof... in this case, just a callback that checks that the submitted password is tada. If we are able to find a user and the credentials are correct... then we are authenticated!

We saw this at the end of the last video! When we logged in using the email of a real user in our database and password tada... we hit this dd() statement:

75 lines | src/Security/LoginFormAuthenticator.php
// ... lines 1 - 17
class LoginFormAuthenticator extends AbstractAuthenticator
{
// ... lines 20 - 53
public function onAuthenticationSuccess(Request $request, TokenInterface $token, string $firewallName): ?Response
{
dd('success');
}
// ... lines 58 - 73
}

onAuthenticationSuccess

Yep! If authentication is successful Symfony calls onAuthenticationSuccess() and asks:

Congrats on authenticating! We're super proud! But... what should we do now?

In our situation, after success, we probably want to redirect the user to some other page. But for other types of authentication you might do something different. For example, if you're authenticating via an API token, you would return null from this method to allow the request to continue to the normal controller.

Anyways, that's our job here: to decide what to do "next"... which will either be "do nothing" - null - or return some sort of Response object. We're going to redirect.

Head up to the top of this class. Add a second argument - RouterInterface $router - use the Alt+Enter trick and select "Initialize properties" to create that property and set it:

81 lines | src/Security/LoginFormAuthenticator.php
// ... lines 1 - 9
use Symfony\Component\Routing\RouterInterface;
// ... lines 11 - 19
class LoginFormAuthenticator extends AbstractAuthenticator
{
// ... line 22
private RouterInterface $router;
public function __construct(UserRepository $userRepository, RouterInterface $router)
{
// ... line 27
$this->router = $router;
}
// ... lines 30 - 79
}

Back down in onAuthenticationSuccess(), we need to return null or a Response. Return a new RedirectResponse() and, for the URL, say $this->router->generate() and pass app_homepage:

81 lines | src/Security/LoginFormAuthenticator.php
// ... lines 1 - 6
use Symfony\Component\HttpFoundation\RedirectResponse;
// ... lines 8 - 19
class LoginFormAuthenticator extends AbstractAuthenticator
{
// ... lines 22 - 57
public function onAuthenticationSuccess(Request $request, TokenInterface $token, string $firewallName): ?Response
{
return new RedirectResponse(
$this->router->generate('app_homepage')
);
}
// ... lines 64 - 79
}

Let me go... double-check that route name.... it should be inside of QuestionController. Yup! app_homepage is correct:

88 lines | src/Controller/QuestionController.php
// ... lines 1 - 17
class QuestionController extends AbstractController
{
// ... lines 20 - 29
/**
* @Route("/{page<\d+>}", name="app_homepage")
*/
public function homepage(QuestionRepository $repository, int $page = 1)
{
// ... lines 35 - 43
}
// ... lines 45 - 86
}

I'm not sure why PhpStorm thinks this route is missing... it's definitely there.

Anyways, let's log in from scratch. Go directly to /login, enter abraca_admin@example.com - because that's a real email in our database - and password "tada". When we submit... it works! We're redirected! And we're logged in! I know because of the web debug toolbar: logged in as abraca_admin@example.com, authenticated: Yes.

If you click this icon to jump into the profiler, there is a ton of juicy info about security. We're going to talk about the most important parts of this as we go along.

Authentication Info & The Session

Click back to the homepage. Notice that, if we surf around the site, we stay logged in... which is what we want. This works because Symfony firewalls are, by default, "stateful". That's a fancy way of saying that, at the end of each request, the User object is saved to the session. Then at the start of the next request, that User object is loaded from the session... and we stay logged in.

Refreshing the User

This works great! But... there is one potential problem. Imagine we log in at our work computer. Then, we go home, log in on a totally different computer, and change some of our user data - like maybe we change our firstName in the database via an "edit profile" section. When we come back to work the next day and refresh the site, Symfony will, of course, load the User object from the session. But... that User object will now have the wrong firstName! Its data will no longer match what's in the database... because we're reloading a "stale" object from the session.

Fortunately... this is not a real problem. Why? Because at the beginning of every request, Symfony also refreshes the user. Well, actually our "user provider" does this. Back in security.yaml, remember that user provider thingy?

34 lines | config/packages/security.yaml
security:
// ... lines 2 - 7
providers:
# used to reload user from session & other features (e.g. switch_user)
app_user_provider:
entity:
class: App\Entity\User
property: email
firewalls:
// ... lines 15 - 17
main:
// ... line 19
provider: app_user_provider
// ... lines 21 - 34

Yep it has two jobs. First, if we give it an email, it knows how to find that user. If we only pass a single argument to UserBadge then the user provider does the hard work of loading the User from the database:

81 lines | src/Security/LoginFormAuthenticator.php
// ... lines 1 - 19
class LoginFormAuthenticator extends AbstractAuthenticator
{
// ... lines 22 - 35
public function authenticate(Request $request): PassportInterface
{
// ... lines 38 - 40
return new Passport(
new UserBadge($email, function($userIdentifier) {
// ... lines 43 - 50
}),
// ... lines 52 - 54
);
}
// ... lines 57 - 79
}

But the user provider also has a second job. At the start of every request, it refreshes the User by querying the database for fresh data. This all happens automatically in the background.... which is great! It's a boring, but critical process that you, at least, should be aware of.

User Changed === Logged Out

Oh, and by the way: after querying for the fresh User data, if some important data on the user changed - like the email, password or roles - you'll actually get logged out. This is a security feature: it allows a user to, for example, change their password and cause any "bad" users who may have gotten access to their account to get logged out. If you want to learn more about this, search for EquatableInterface: that's an interface that allows you to control this process.

Let's find out what happens when we fail authentication. Where does the user go? How are errors displayed? How will we deal with the emotional burden of failure? Most of that is next.