How to Write a Custom Authenticator
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How to Write a Custom Authenticator
Symfony comes with many authenticators and third party bundles also implement more complex cases like JWT and oAuth 2.0. However, sometimes you need to implement a custom authentication mechanism that doesn't exist yet or you need to customize one. In such cases, you must create and use your own authenticator.
Authenticators should implement the
AuthenticatorInterface.
You can also extend
AbstractAuthenticator,
which has a default implementation for the createToken()
method that fits most use-cases:
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// src/Security/ApiKeyAuthenticator.php
namespace App\Security;
use Symfony\Component\HttpFoundation\JsonResponse;
use Symfony\Component\HttpFoundation\Request;
use Symfony\Component\HttpFoundation\Response;
use Symfony\Component\Security\Core\Authentication\Token\TokenInterface;
use Symfony\Component\Security\Core\Exception\AuthenticationException;
use Symfony\Component\Security\Core\Exception\CustomUserMessageAuthenticationException;
use Symfony\Component\Security\Http\Authenticator\AbstractAuthenticator;
use Symfony\Component\Security\Http\Authenticator\Passport\Badge\UserBadge;
use Symfony\Component\Security\Http\Authenticator\Passport\Passport;
use Symfony\Component\Security\Http\Authenticator\Passport\SelfValidatingPassport;
class ApiKeyAuthenticator extends AbstractAuthenticator
{
/**
* Called on every request to decide if this authenticator should be
* used for the request. Returning `false` will cause this authenticator
* to be skipped.
*/
public function supports(Request $request): ?bool
{
return $request->headers->has('X-AUTH-TOKEN');
}
public function authenticate(Request $request): Passport
{
$apiToken = $request->headers->get('X-AUTH-TOKEN');
if (null === $apiToken) {
// The token header was empty, authentication fails with HTTP Status
// Code 401 "Unauthorized"
throw new CustomUserMessageAuthenticationException('No API token provided');
}
return new SelfValidatingPassport(new UserBadge($apiToken));
}
public function onAuthenticationSuccess(Request $request, TokenInterface $token, string $firewallName): ?Response
{
// on success, let the request continue
return null;
}
public function onAuthenticationFailure(Request $request, AuthenticationException $exception): ?Response
{
$data = [
// you may want to customize or obfuscate the message first
'message' => strtr($exception->getMessageKey(), $exception->getMessageData())
// or to translate this message
// $this->translator->trans($exception->getMessageKey(), $exception->getMessageData())
];
return new JsonResponse($data, Response::HTTP_UNAUTHORIZED);
}
}
Tip
If your custom authenticator is a login form, you can extend from the AbstractLoginFormAuthenticator class instead to make your job easier.
The authenticator can be enabled using the custom_authenticators
setting:
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# config/packages/security.yaml
security:
# ...
firewalls:
main:
custom_authenticators:
- App\Security\ApiKeyAuthenticator
Tip
You may want your authenticator to implement
AuthenticationEntryPointInterface
. This defines the response sent
to users to start authentication (e.g. when they visit a protected
page). Read more about it in The Entry Point: Helping Users Start Authentication.
The authenticate()
method is the most important method of the
authenticator. Its job is to extract credentials (e.g. username &
password, or API tokens) from the Request
object and transform these
into a security
Passport
(security passports are explained later in this article).
After the authentication process finished, the user is either authenticated or there was something wrong (e.g. incorrect password). The authenticator can define what happens in these cases:
onAuthenticationSuccess(Request $request, TokenInterface $token, string $firewallName): ?Response
-
If the user is authenticated, this method is called with the authenticated
$token
. This method can return a response (e.g. redirect the user to the homepage).If
null
is returned, the request continues like normal (i.e. the controller matching the login route is called). This is useful for API routes where each route is protected by an API key header. onAuthenticationFailure(Request $request, AuthenticationException $exception): ?Response
-
If an
AuthenticationException
is thrown during authentication, the process fails and this method is called. This method can return a response (e.g. to return a 401 Unauthorized response in API routes).If
null
is returned, the request continues like normal. This is useful for e.g. login forms, where the login controller is run again with the login errors.If you're using login throttling, you can check if
$exception
is an instance of TooManyLoginAttemptsAuthenticationException (e.g. to display an appropriate message).Caution: Never use
$exception->getMessage()
forAuthenticationException
instances. This message might contain sensitive information that you don't want to be publicly exposed. Instead, use$exception->getMessageKey()
and$exception->getMessageData()
like shown in the full example above. Use CustomUserMessageAuthenticationException if you want to set custom error messages.
Tip
If your login method is interactive, which means that the user actively logged into your application, you may want your authenticator to implement the InteractiveAuthenticatorInterface so that it dispatches an InteractiveLoginEvent
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);
Note
You can optionally pass a user loader as second argument to the
UserBadge
. This callable receives the $userIdentifier
and must return a UserInterface
object (otherwise a
UserNotFoundException
is thrown):
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// src/Security/CustomAuthenticator.php
namespace App\Security;
use App\Repository\UserRepository;
// ...
class CustomAuthenticator extends AbstractAuthenticator
{
private $userRepository;
public function __construct(UserRepository $userRepository)
{
$this->userRepository = $userRepository;
}
public function authenticate(Request $request): Passport
{
// ...
return new Passport(
new UserBadge($email, function (string $userIdentifier) {
return $this->userRepository->findOneBy(['email' => $userIdentifier]);
}),
$credentials
);
}
}
The following credential classes are supported by default:
- PasswordCredentials
-
This requires a plaintext
$password
, which is validated using the password encoder configured for the user:1 2 3 4
use Symfony\Component\Security\Http\Authenticator\Passport\Credentials\PasswordCredentials; // ... return new Passport(new UserBadge($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 $credentials parameter is equal to the next argument of this class function ($credentials, UserInterface $user) { return $user->getApiToken() === $credentials; }, // The custom credentials $apiToken ));
Self Validating Passport
If you don't need any credentials to be checked (e.g. when using API
tokens), you can use the
SelfValidatingPassport.
This class only requires a UserBadge
object and optionally Passport Badges.
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.
Note
The PasswordUpgradeBadge
is automatically added to the passport if the
passport has PasswordCredentials
.
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'));
}
}