# The Java EE 7 Tutorial

# 50.5 Securing Application Clients

The Java EE authentication requirements for application clients are the same as for other Java EE components, and the same authentication techniques can be used as for other Java EE application components. No authentication is necessary when accessing unprotected web resources.

When accessing protected web resources, the usual varieties of authentication can be used: HTTP basic authentication, HTTP login-form authentication, or SSL client authentication. Specifying an Authentication Mechanism in the Deployment Descriptor describes how to specify HTTP basic authentication and HTTP login-form authentication. Client Authentication describes how to specify SSL client authentication.

Authentication is required when accessing protected enterprise beans. The authentication mechanisms for enterprise beans are discussed in Securing Enterprise Beans.

An application client makes use of an authentication service provided by the application client container for authenticating its users. The container's service can be integrated with the native platform's authentication system so that a single sign-on capability is used. The container can authenticate the user either when the application is started or when a protected resource is accessed.

An application client can provide a class, called a login module, to gather authentication data. If so, the `javax.security.auth.callback.CallbackHandler` interface must be implemented, and the class name must be specified in its deployment descriptor. The application's callback handler must fully support `Callback` objects specified in the `javax.security.auth.callback` package.

## 50.5.1 Using Login Modules

An application client can use the Java Authentication and Authorization Service (JAAS) to create login modules for authentication. A JAAS-based application implements the `javax.security.auth.callback.CallbackHandler` interface so that it can interact with users to enter specific authentication data, such as user names or passwords, or to display error and warning messages.

Applications implement the `CallbackHandler` interface and pass it to the login context, which forwards it directly to the underlying login modules. A login module uses the callback handler both to gather input, such as a password or smart card PIN, from users and to supply information, such as status information, to users. Because the application specifies the callback handler, an underlying login module can remain independent of the various ways applications interact with users.

For example, the implementation of a callback handler for a GUI application might display a window to solicit user input, or the implementation of a callback handler for a command-line tool might simply prompt the user for input directly from the command line.

The login module passes an array of appropriate callbacks to the callback handler's `handle` method, such as a `NameCallback` for the user name and a `PasswordCallback` for the password; the callback handler performs the requested user interaction and sets appropriate values in the callbacks. For example, to process a `NameCallback`, the `CallbackHandler` might prompt for a name, retrieve the value from the user, and call the `setName` method of the `NameCallback` to store the name.

For more information on using JAAS for authentication in login modules, refer to the documentation listed in Further Information about Advanced Security Topics.

## 50.5.2 Using Programmatic Login

Programmatic login enables the client code to supply user credentials. If you are using an EJB client, you can use the `com.sun.appserv.security.ProgrammaticLogin` class with its convenient `login` and `logout` methods. Programmatic login is specific to a server.