Exercise 1: Using the JAAS API
Goal of This Exercise
The goal of this exercise is to learn how to use the Java Authentication and Authorization (JAAS) API to perform authentication.
Background for This Exercise
JAAS provides a standard pluggable authentication framework (PAM) for the Java platform. An application uses the JAAS API to perform authentication - the process of verifying the identity of the user who is using the application and gathering his identity information into a container called a subject. The application can then use the identity information in the subject along with the JAAS API to make authorization decisions, to decide whether the authenticated user is allowed to access protected resources or perform restricted actions. This exercise demonstrates JAAS Authentication. It does not demonstrate JAAS Authorization.
Resources for This Exercise
Steps to Follow
Jass.javasample code. The code performs the following tasks:
- Define a callback handler or use a predefined one.
- Create a LoginContext with a name that identifies which JAAS configuration entry to use.
- Perform the authentication.
- Define the task that the authenticated user is to perform.
- Perform the action as the authenticated user.
- Log out.
Subject.doAs will run the code defined in
MyActionas the authenticated user [lines 14-15]. This serves two purposes. First, code in
MyActionthat requires identity information for authentication to a service could get it from the subject. This exercise demonstrates this use. Second, if
MyActionaccesses any protected resources/operations, the identity information in the current subject would be used to make the corresponding access control decision. This second aspect is not covered in this exercise.
Make sure that the
%JAVA_HOME%/binis in the PATH environment variable.
Compile the modified sample code. You will run this code in subsequent exercises after doing some set up. That ends this exercise.
This exercise introduced the main classes of the JAAS APIs: LoginContext and Subject. You learned how to use LoginContext to authenticate a user and collect its identity information in a Subject. You then learned how to use the Subject to perform an action as the authenticated user.
Proceed to Exercise 2: Configuring JAAS for Kerberos Authentication to learn how to configure the sample application to use Kerberos for authentication.
Exercise 2: Configuring JAAS for Kerberos Authentication
Goal of This Exercise
The goal of this exercise is to learn how to configure a JAAS application to use Kerberos for authentication.
Kerberos Background for This Exercise
Kerberos is an Internet standard protocol for trusted-third party authentication defined in RFC 4120. It is available on most modern computing platforms today, including Solaris, Windows, and Linux.
The Kerberos architecture is centered around a trusted authentication service called the key distribution center, or KDC. Users and services in a Kerberos environment are referred to as principals; each principal shares a secret (such as a password) with the KDC. A principal authenticates to Kerberos by proving to the KDC that it knows the shared secret. If the authentication is successful, the KDC issues a ticket-granting-ticket (TGT) to the principal. When the principal subsequently wants to authenticate to a service on the network, such as a directory service or a file service, (thereby, acting as a "client" of the service), it gives the TGT to the KDC to obtain a service ticket to communicate with the service. Not only does the service ticket indicate the identities of the client and service principals, it also contains a session key that can be used by the client and service to subsequently establish secure communication. To authenticate to the service, the client sends the service ticket to the service. When the service receives the ticket, it decodes it using the secret it shares with the KDC.
In this architecture, a principal only authenticates directly (once) to the KDC. It authenticates indirectly to all other services via the use of service tickets. Service tickets are how the KDC vouches for the identity of a principal. The ability of a principal to access multiple secure services by performing explicit authentication only once is called single sign-on.
JAAS Background for This exercise
In JAAS, for a client principal, "logging into Kerberos" means acquiring the TGT and placing it in the Subject, so that it can be used for authentication with services that the client will access. For a service principal, "logging into Kerberos" means obtaining the secret keys that the service needs to decode incoming client authentication requests.
Resources for This Exercise
Steps to Follow
Examine the jaas-krb5.conf configuration file.
This file contains two entries, one named client and one named server. The client entry indicates that the LoginContext must use the com.sun.security.auth.module.Krb5LoginModule. The server entry indicates that the LoginContext must use the same login module, and use keys from the
sample.keytabfile for the principal host/machineName.
Determine the hostname of your machine by executing the hostname command.
Edit this file and change the entry for server principal to use the name of your machine. For example, if your machine name is j1hol-001, this line in the configuration file should look like this:
Perform client authentication by typing the following command:
% java -Djava.security.auth.login.config=jaas-krb5.conf Jaas client
You will be prompted for a password. You should see the following output. Replace password with a password that is secure.
Kerberos password for test: password Authenticated principal: [test@J1LABS.EXAMPLE.COM] Performing secure action...
Perform server authentication by typing the following command:
% java -Djava.security.auth.login.config=jaas-krb5.conf Jaas server
You should see the following output:
Authenticated principal: [host/j1hol-001@J1LABS.EXAMPLE.COM] Performing secure action...
In this exercise, you learned how to configure a JAAS application to use a Kerberos login module, both as a client principal who enters his/her username/password interactively, and as a service principal who gets its keys from a
Proceed to Part II : Secure Communications using the Java SE Security API to learn how to establish secure communication channels using Java security APIs.