How to Write a Custom Authenticator

Security Passports

A passport is an object that contains the user that will be authenticated as well as other pieces of information, like whether a password should be checked or if "remember me" functionality should be enabled.

The default Passport requires a user and some sort of "credentials" (e.g. a password).

Use the UserBadge to attach the user to the passport. The UserBadge requires a user identifier (e.g. the username or email), which is used to load the user using the user provider:

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use Symfony\Component\Security\Http\Authenticator\Passport\Badge\UserBadge;

// ...
$passport = new Passport(new UserBadge($email), $credentials);

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// src/Security/CustomAuthenticator.php
namespace App\Security;

use App\Repository\UserRepository;
// ...

class CustomAuthenticator extends AbstractAuthenticator
{
    public function __construct(
        private UserRepository $userRepository,
    ) {
    }

    public function authenticate(Request $request): Passport
    {
        // ...

        return new Passport(
            new UserBadge($email, function (string $userIdentifier): ?UserInterface {
                return $this->userRepository->findOneBy(['email' => $userIdentifier]);
            }),
            $credentials
        );
    }
}

The following credential classes are supported by default:

PasswordCredentials

This requires a plaintext $password, which is validated using the password encoder configured for the user:

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use Symfony\Component\Security\Http\Authenticator\Passport\Credentials\PasswordCredentials;

// ...
return new Passport(new UserBadge($email), new PasswordCredentials($plaintextPassword));

CustomCredentials

Allows a custom closure to check credentials:

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use Symfony\Component\Security\Core\User\UserInterface;
use Symfony\Component\Security\Http\Authenticator\Passport\Credentials\CustomCredentials;

// ...
return new Passport(new UserBadge($email), new CustomCredentials(
    // If this function returns anything else than `true`, the credentials
    // are marked as invalid.
    // The $credentials parameter is equal to the next argument of this class
    function (string $credentials, UserInterface $user): bool {
        return $user->getApiToken() === $credentials;
    },

    // The custom credentials
    $apiToken
));

Passport Badges

The Passport also optionally allows you to add security badges. Badges attach more data to the passport (to extend security). By default, the following badges are supported:

RememberMeBadge

When this badge is added to the passport, the authenticator indicates remember me is supported. Whether remember me is actually used depends on special remember_me configuration. Read How to Add "Remember Me" Login Functionality for more information.

PasswordUpgradeBadge

This is used to automatically upgrade the password to a new hash upon successful login (if needed). This badge requires the plaintext password and a password upgrader (e.g. the user repository). See Password Hashing and Verification.

CsrfTokenBadge

Automatically validates CSRF tokens for this authenticator during authentication. The constructor requires a token ID (unique per form) and CSRF token (unique per request). See How to Implement CSRF Protection.

PreAuthenticatedUserBadge

Indicates that this user was pre-authenticated (i.e. before Symfony was initiated). This skips the pre-authentication user checker.

For instance, if you want to add CSRF to your custom authenticator, you would initialize the passport like this:

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// src/Service/LoginAuthenticator.php
namespace App\Service;

// ...
use Symfony\Component\Security\Http\Authenticator\AbstractAuthenticator;
use Symfony\Component\Security\Http\Authenticator\Passport\Badge\CsrfTokenBadge;
use Symfony\Component\Security\Http\Authenticator\Passport\Badge\UserBadge;
use Symfony\Component\Security\Http\Authenticator\Passport\Passport;

class LoginAuthenticator extends AbstractAuthenticator
{
    public function authenticate(Request $request): Passport
    {
        $password = $request->request->get('password');
        $username = $request->request->get('username');
        $csrfToken = $request->request->get('csrf_token');

        // ... validate no parameter is empty

        return new Passport(
            new UserBadge($username),
            new PasswordCredentials($password),
            [new CsrfTokenBadge('login', $csrfToken)]
        );
    }
}

Passport Attributes

Besides badges, passports can define attributes, which allows the authenticate() method to store arbitrary information in the passport to access it from other authenticator methods (e.g. createToken()):

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// ...
use Symfony\Component\Security\Http\Authenticator\Passport\Badge\UserBadge;

class LoginAuthenticator extends AbstractAuthenticator
{
    // ...

    public function authenticate(Request $request): Passport
    {
        // ... process the request

        $passport = new SelfValidatingPassport(new UserBadge($username), []);

        // set a custom attribute (e.g. scope)
        $passport->setAttribute('scope', $oauthScope);

        return $passport;
    }

    public function createToken(Passport $passport, string $firewallName): TokenInterface
    {
        // read the attribute value
        return new CustomOauthToken($passport->getUser(), $passport->getAttribute('scope'));
    }
}