The Java EE 6 Tutorial

Overview of Java EE Security

Enterprise tier and web tier applications are made up of components that are deployed into various containers. These components are combined to build a multitier enterprise application. Security for components is provided by their containers. A container provides two kinds of security: declarative and programmatic.

A Simple Security Example

The security behavior of a Java EE environment may be better understood by examining what happens in a simple application with a web client, a user interface, and enterprise bean business logic.

In the following example, which is taken from the Java EE 6 Specification, the web client relies on the web server to act as its authentication proxy by collecting user authentication data from the client and using it to establish an authenticated session.

Step 1: Initial Request

In the first step of this example, the web client requests the main application URL. This action is shown in Figure 24–1.

Figure 24–1 Initial Request

Diagram of initial request from web client to web server
for access to a protected resource

Since the client has not yet authenticated itself to the application environment, the server responsible for delivering the web portion of the application, hereafter referred to as the web server, detects this and invokes the appropriate authentication mechanism for this resource. For more information on these mechanisms, see Security Mechanisms.

Step 2: Initial Authentication

The web server returns a form that the web client uses to collect authentication data, such as user name and password, from the user. The web client forwards the authentication data to the web server, where it is validated by the web server, as shown in Figure 24–2. The validation mechanism may be local to a server or may leverage the underlying security services. On the basis of the validation, the web server sets a credential for the user.

Figure 24–2 Initial Authentication

Diagram of initial authentication: server sends form
to client, which sends authentication data to server for validation

Step 3: URL Authorization

The credential is used for future determinations of whether the user is authorized to access restricted resources it may request. The web server consults the security policy associated with the web resource to determine the security roles that are permitted access to the resource. The security policy is derived from annotations or from the deployment descriptor. The web container then tests the user’s credential against each role to determine whether it can map the user to the role. Figure 24–3 shows this process.

Figure 24–3 URL Authorization

Diagram of URL authorization

The web server’s evaluation stops with an “is authorized” outcome when the web server is able to map the user to a role. A “not authorized” outcome is reached if the web server is unable to map the user to any of the permitted roles.

Step 4: Fulfilling the Original Request

If the user is authorized, the web server returns the result of the original URL request, as shown in Figure 24–4.

Figure 24–4 Fulfilling the Original Request

Diagram of request fulfillment, showing server returning
result to client

In our example, the response URL of a web page is returned, enabling the user to post form data that needs to be handled by the business-logic component of the application. See Chapter 25, Getting Started Securing Web Applications for more information on protecting web applications.

Step 5: Invoking Enterprise Bean Business Methods

The web page performs the remote method call to the enterprise bean, using the user’s credential to establish a secure association between the web page and the enterprise bean, as shown in Figure 24–5. The association is implemented as two related security contexts: one in the web server and one in the EJB container.

Figure 24–5 Invoking an Enterprise Bean Business Method

Diagram of authorization process between web component
and enterprise bean

The EJB container is responsible for enforcing access control on the enterprise bean method. The container consults the security policy associated with the enterprise bean to determine the security roles that are permitted access to the method. The security policy is derived from annotations or from the deployment descriptor. For each role, the EJB container determines whether it can map the caller to the role by using the security context associated with the call.

The container’s evaluation stops with an “is authorized” outcome when the container is able to map the caller’s credential to a role. A “not authorized” outcome is reached if the container is unable to map the caller to any of the permitted roles. A “not authorized” result causes an exception to be thrown by the container and propagated back to the calling web page.

If the call is authorized, the container dispatches control to the enterprise bean method. The result of the bean’s execution of the call is returned to the web page and ultimately to the user by the web server and the web client.

Features of a Security Mechanism

A properly implemented security mechanism will provide the following functionality:

Ideally, properly implemented security mechanisms will also be

Characteristics of Application Security

Java EE applications consist of components that can contain both protected and unprotected resources. Often, you need to protect resources to ensure that only authorized users have access. Authorization provides controlled access to protected resources. Authorization is based on identification and authentication. Identification is a process that enables recognition of an entity by a system, and authentication is a process that verifies the identity of a user, device, or other entity in a computer system, usually as a prerequisite to allowing access to resources in a system.

Authorization and authentication are not required for an entity to access unprotected resources. Accessing a resource without authentication is referred to as unauthenticated, or anonymous, access.

The characteristics of application security that, when properly addressed, help to minimize the security threats faced by an enterprise include the following: