How to Create and Enable Custom User Checkers

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How to Create and Enable Custom User Checkers

During the authentication of a user, additional checks might be required to verify if the identified user is allowed to log in. By defining a custom user checker, you can define per firewall which checker should be used.

Creating a Custom User Checker

User checkers are classes that must implement the UserCheckerInterface. This interface defines two methods called checkPreAuth() and checkPostAuth() to perform checks before and after user authentication. If one or more conditions are not met, throw an exception which extends the AccountStatusException class. Consider using CustomUserMessageAccountStatusException, which extends AccountStatusException and allows to customize the error message displayed to the user:

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namespace App\Security;

use App\Entity\User as AppUser;
use Symfony\Component\Security\Core\Exception\AccountExpiredException;
use Symfony\Component\Security\Core\Exception\CustomUserMessageAccountStatusException;
use Symfony\Component\Security\Core\User\UserCheckerInterface;
use Symfony\Component\Security\Core\User\UserInterface;

class UserChecker implements UserCheckerInterface
{
    public function checkPreAuth(UserInterface $user): void
    {
        if (!$user instanceof AppUser) {
            return;
        }

        if ($user->isDeleted()) {
            // the message passed to this exception is meant to be displayed to the user
            throw new CustomUserMessageAccountStatusException('Your user account no longer exists.');
        }
    }

    public function checkPostAuth(UserInterface $user): void
    {
        if (!$user instanceof AppUser) {
            return;
        }

        // user account is expired, the user may be notified
        if ($user->isExpired()) {
            throw new AccountExpiredException('...');
        }
    }
}

Enabling the Custom User Checker

Next, make sure your user checker is registered as a service. If you're using the default services.yaml configuration, the service is registered automatically.

All that's left to do is add the checker to the desired firewall where the value is the service id of your user checker:

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# config/packages/security.yaml

# ...
security:
    firewalls:
        main:
            pattern: ^/
            user_checker: App\Security\UserChecker
            # ...

Using Multiple User Checkers

6.2

The ChainUserChecker class was added in Symfony 6.2.

It is common for applications to have multiple authentication entry points (such as traditional form based login and an API) which may have unique checker rules for each entry point as well as common rules for all entry points. To allow using multiple user checkers on a firewall, a service for the ChainUserChecker class is created for each firewall.

To use the chain user checker, first you will need to tag your user checker services with the security.user_checker.<firewall> tag (where <firewall> is the name of the firewall in your security configuration). The service tag also supports the priority attribute, allowing you to define the order in which user checkers are called:

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# config/services.yaml

# ...
services:
    App\Security\AccountEnabledUserChecker:
        tags:
            - { name: security.user_checker.api, priority: 10 }
            - { name: security.user_checker.main, priority: 10 }

    App\Security\APIAccessAllowedUserChecker:
        tags:
            - { name: security.user_checker.api, priority: 5 }

Once your checker services are tagged, next you will need configure your firewalls to use the security.user_checker.chain.<firewall> service:

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# config/packages/security.yaml

# ...
security:
    firewalls:
        api:
            pattern: ^/api
            user_checker: security.user_checker.chain.api
            # ...
        main:
            pattern: ^/
            user_checker: security.user_checker.chain.main
            # ...
This work, including the code samples, is licensed under a Creative Commons BY-SA 3.0 license.
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