Custom providers

Serverpod's authentication module makes it easy to implement custom authentication providers. This allows you to leverage all the existing providers supplied by the module along with the specific providers your project requires.

Server setup

After successfully authenticating a user through a customer provider, an auth token can be created and connected to the user to preserve the authenticated user's permissions. This token is used to identify the user and facilitate endpoint authorization validation. The token can be removed when the user signs out to prevent further access.

Connect user

The authentication module provides methods to find or create users. This ensures that all authentication tokens from the same user are connected.

Users can be identified either by their email through the Users.findUserByEmail(...) method or by a unique identifier through the Users.findUserByIdentifier(...) method.

If no user is found, a new user can be created through the Users.createUser(...) method.

UserInfo? userInfo;
userInfo = await Users.findUserByEmail(session, email);
userInfo ??= await Users.findUserByIdentifier(session, userIdentifier);
if (userInfo == null) {
  userInfo = UserInfo(
    userIdentifier: userIdentifier,
    userName: name,
    email: email,
    blocked: false,
    created: DateTime.now().toUtc(),
    scopeNames: [],
  );
  userInfo = await Users.createUser(session, userInfo, _authMethod);
}

The example above tries to find a user by email and user identifier. If no user is found, a new user is created with the provided information. The methods that you must implement yourself is authenticateUser and findOrCreateUser, keep in mind that they possibly take different parameters than in this simplified example.

note

For many authentication platforms the userIdentifier is the user's email, but it can also be another unique identifier such as a phone number or a social security number.

Custom identification methods

If other identification methods are required you can easly implement them by accessing the database directly. The UserInfo model can be interacted with in the same way as any other model with a database in Serverpod.

var userInfo = await UserInfo.db.findFirstRow(
  session,
  where: (t) => t.fullName.equals(name),
);

The example above shows how to find a user by name using the UserInfo model.

Create auth token

When a user has been found or created, an auth token that is connected to the user should be created.

To create an auth token, call the signInUser method in the UserAuthentication class, accessible through the session.auth field on the session object.

The signInUser method takes three arguments: the first is the user ID, the second is information about the method of authentication, and the third is a set of scopes granted to the auth token.

var authToken = await session.auth.signInUser(userInfo.id, 'myAuthMethod', scopes: {
    Scope('delete'),
    Scope('create'),
});

The example above creates an auth token for a user with the unique identifier taken from the userInfo. The auth token preserves that it was created using the method myAuthMethod and has the scopes delete and create.

Send auth token to client

Once the auth token is created, it should be sent to the client. We recommend doing this using an AuthenticationResponse. This ensures compatibility with the client-side authentication module.

class MyAuthenticationEndpoint extends Endpoint {
  Future<AuthenticationResponse> login(
    Session session,
    String username,
    String password,
  ) async {
    // Authenticates a user with email and password.
    if (!authenticateUser(session, username, password)) {
      return AuthenticationResponse(success: false);
    }

    // Finds or creates a user in the database using the User methods.
    var userInfo = findOrCreateUser(session, username);

    // Creates an authentication key for the user.
    var authToken = await session.auth.signInUser(
      userInfo.id!,
      'myAuth',
      scopes: {},
    );

    // Returns the authentication response.
    return AuthenticationResponse(
      success: true,
      keyId: authToken.id,
      key: authToken.key,
      userInfo: userInfo,
    );
  }
}

The example above shows how to create an AuthenticationResponse with the auth token and user information.

Client setup

The client must store and include the auth token in communication with the server. Luckily, the client-side authentication module handles this for you through the SessionManager.

The session manager is responsible for storing the auth token and user information. It is initialized on client startup and will restore any existing user session from local storage.

After a successful authentication where an authentication response is returned from the server, the user should be registered in the session manager through the sessionManager.registerSignedInUser(...) method. The session manager singleton is accessible by calling SessionManager.instance.

var serverResponse = await caller.myAuthentication.login(username, password);

if (serverResponse.success) {
    // Store the user info in the session manager.
    SessionManager sessionManager = await SessionManager.instance;
    await sessionManager.registerSignedInUser(
        serverResponse.userInfo!,
        serverResponse.keyId!,
        serverResponse.key!,
    );
}

The example above shows how to register a signed-in user in the session manager.