Java Dynamic Management Kit 5.1 Tutorial

11.2.1 Secure RMI Connectors With Subject Delegation

You can find an example of a secure RMI connector that implements subject delegation in the directory examplesDir/current/Security/rmi/subject_delegation.

The Server class used in this example is identical to the one used in 11.1 Simple Security. However, unlike the simple security example, this example implements a java.policy file to grant permission to certain users to perform certain actions.

Example 11–5 A java.policy File

grant codeBase "file:installDir/lib/jmxremote.jar" {

grant codeBase "file:server" {

grant principal "username" {

The java.policy file grants a user named username a SubjectDelegationPermission so it can perform operations on behalf of the user delegate, an instance of JMXPrincipal created by the Client class. The java.policy file is required when launching the Server class. The creation of the JMXPrincipal instance by the Client is shown below.

Example 11–6 Creating a Delegation Subject


JMXConnector jmxc = JMXConnectorFactory.connect(url, env); 
Subject delegationSubject = 
            new Subject(true, 
                Collections.singleton(new JMXPrincipal("delegate")), 
MBeanServerConnection mbsc = 

The Client class is identical to the one used in the simple security example, except for the creation of the delegation subject shown in Example 11–6.

As before, the Client creates an environment map env that is populated with a user name username and a password password. These strings match the user name and password stored in the file that is held by the Server to authenticate users accessing the connector server.

A connector client jmxc is created in the same way as in the previous RMI connector examples, with the user name and password passed into the environment map env.

The Client then creates an instance of Subject, called delegationSubject, with a Principal that is an instance of JMXPrincipal, named delegate.

An MBean server connection, named mbsc, is created by calling the getMBeanServerConnection() method of JMXConnector, with delegationSubject passed in as a parameter. This MBean server connection therefore allows operations to be performed on the remote MBean server on behalf of the principals stored in the delegationSubject, which in this example is the JMXPrincipal named delegate.

The example continues by creating and registering the SimpleStandard MBean in the MBean server, and performing operations on it, in exactly the same way as in the previous examples.

To Run the Secure RMI Connector Example With Subject Delegation

Run this example from within the examplesDir/current/Security/rmi/subject_delegation directory.

  1. Compile the example classes.

    $ javac -classpath classpath \ 
      mbeans/ \ 
      mbeans/ \ 
      server/ \ 
      client/ \ 
  2. Start an RMI registry on port 9999 of the local host.

    $ export CLASSPATH=server:classpath ; rmiregistry 9999 &
  3. Create a java.policy file from the java.policy.template file in the config directory.

    You must replace @INSTALL_HOME_FOR_JDMK@ with your installDir.

  4. Start the Server.

    As was the case with the simple secure RMI connector example, you have to provide the SSL keystore and its password when you start the Server, as well as the a pointer to the java.policy that grants permission to the delegate subject.

    $ java -classpath server:mbeans:classpath \ \ \ Server &

    You will see confirmation of the creation of the MBean server, the initialization of the environment map, the creation of the RMI connector, and the registration of the connector in the MBean server.

  5. Start the Client.

    Again, the Client requires the SSL truststore and its password when it is launched.

    $ java -classpath client:server:mbeans:classpath \ \ \

    You will see confirmation of the creation of the connector client, the creation of the delegation subject, the connection to the MBean server and the various MBean operations followed by the closure of the connection.