7.6.4. Change the Security Context Identity

Procedure 7.12. Change the Identity of the Security Context

1. Create the client side interceptor

   The client side interceptor must implement the org.jboss.ejb.client.EJBClientInterceptor interface. The interceptor must pass the requested identity through the context data map, which can be obtained via a call to EJBClientInvocationContext.getContextData(). The following is an example of client side interceptor code:

   public class ClientSecurityInterceptor implements EJBClientInterceptor {
   
       public void handleInvocation(EJBClientInvocationContext context) throws Exception {
           Principal currentPrincipal = SecurityActions.securityContextGetPrincipal();
   
           if (currentPrincipal != null) {
               Map<String, Object> contextData = context.getContextData();
               contextData.put(ServerSecurityInterceptor.DELEGATED_USER_KEY, currentPrincipal.getName());
           }
           context.sendRequest();
       }
   
       public Object handleInvocationResult(EJBClientInvocationContext context) throws Exception {
           return context.getResult();
       }
   }
   

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   User applications can insert the interceptor into the interceptor chain in the EJBClientContext in one of the following ways:

   • Programmatically

     With this approach, you call the org.jboss.ejb.client.EJBClientContext.registerInterceptor(int order, EJBClientInterceptor interceptor) method and pass the order and the interceptor instance. The order determines where this client interceptor is placed in the interceptor chain.

   • ServiceLoader Mechanism

     With this approach, you create a META-INF/services/org.jboss.ejb.client.EJBClientInterceptor file and place or package it in the classpath of the client application. The rules for the file are dictated by the Java ServiceLoader Mechanism. This file is expected to contain a separate line for each fully qualified class name of the EJB client interceptor implementation. The EJB client interceptor classes must be available in the classpath. EJB client interceptors added using the ServiceLoader mechanism are added to the end of the client interceptor chain, in the order they are found in the classpath. The ejb-security-interceptors quickstart uses this approach.

2. Create and configure the server side container interceptor

   Container interceptor classes are simple Plain Old Java Objects (POJOs). They use the @javax.annotation.AroundInvoke to mark the method that will be invoked during the invocation on the bean. For more information about container interceptors, refer to: Section 7.6.1, “About Container Interceptors”.

   1. Create the container interceptor

      This interceptor receives the InvocationContext with the identity and requests the switch to that new identity. The following is an abridged version of the actual code example:

          public class ServerSecurityInterceptor {
      
          private static final Logger logger = Logger.getLogger(ServerSecurityInterceptor.class);
      
          static final String DELEGATED_USER_KEY = ServerSecurityInterceptor.class.getName() + ".DelegationUser";
      
          @AroundInvoke
          public Object aroundInvoke(final InvocationContext invocationContext) throws Exception {
              Principal desiredUser = null;
              UserPrincipal connectionUser = null;
      
              Map<String, Object> contextData = invocationContext.getContextData();
              if (contextData.containsKey(DELEGATED_USER_KEY)) {
                  desiredUser = new SimplePrincipal((String) contextData.get(DELEGATED_USER_KEY));
      
                  Collection<Principal> connectionPrincipals = SecurityActions.getConnectionPrincipals();
      
                  if (connectionPrincipals != null) {
                      for (Principal current : connectionPrincipals) {
                          if (current instanceof UserPrincipal) {
                              connectionUser = (UserPrincipal) current;
                              break;
                          }
                      }
      
                  } else {
                      throw new IllegalStateException("Delegation user requested but no user on connection found.");
                  }
              }
      
      
              ContextStateCache stateCache = null;
              try {
                  if (desiredUser != null && connectionUser != null
                      && (desiredUser.getName().equals(connectionUser.getName()) == false)) {
                      // The final part of this check is to verify that the change does actually indicate a change in user.
                      try {
                          // We have been requested to use an authentication token
                          // so now we attempt the switch.
                          stateCache = SecurityActions.pushIdentity(desiredUser, new OuterUserCredential(connectionUser));
                      } catch (Exception e) {
                          logger.error("Failed to switch security context for user", e);
                          // Don't propagate the exception stacktrace back to the client for security reasons
                          throw new EJBAccessException("Unable to attempt switching of user.");
                      }
                  }
      
                  return invocationContext.proceed();
              } finally {
                  // switch back to original context
                  if (stateCache != null) {
                      SecurityActions.popIdentity(stateCache);;
                  }
              }
          }
      

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   2. Configure the container interceptor

      For information on how to configure server side container interceptors, refer to: Section 7.6.3, “Configure a Container Interceptor”.

3. Create the JAAS LoginModule

   This component is responsible for verifying that user is allowed to execute requests as the requested identity. The following abridged code examples show the methods that peform the login and validation:

       @SuppressWarnings("unchecked")
       @Override
       public boolean login() throws LoginException {
           if (super.login() == true) {
               log.debug("super.login()==true");
               return true;
           }
   
           // Time to see if this is a delegation request.
           NameCallback ncb = new NameCallback("Username:");
           ObjectCallback ocb = new ObjectCallback("Password:");
   
           try {
               callbackHandler.handle(new Callback[] { ncb, ocb });
           } catch (Exception e) {
               if (e instanceof RuntimeException) {
                   throw (RuntimeException) e;
               }
               return false; // If the CallbackHandler can not handle the required callbacks then no chance.
           }
   
           String name = ncb.getName();
           Object credential = ocb.getCredential();
   
           if (credential instanceof OuterUserCredential) {
               // This credential type will only be seen for a delegation request, if not seen then the request is not for us.
   
               if (delegationAcceptable(name, (OuterUserCredential) credential)) {
   
                   identity = new SimplePrincipal(name);
                   if (getUseFirstPass()) {
                       String userName = identity.getName();
                       if (log.isDebugEnabled())
                           log.debug("Storing username '" + userName + "' and empty password");
                       // Add the username and an empty password to the shared state map
                       sharedState.put("javax.security.auth.login.name", identity);
                       sharedState.put("javax.security.auth.login.password", "");
                   }
                   loginOk = true;
                   return true;
               }
           }
   
           return false; // Attempted login but not successful.
       }
   
       protected boolean delegationAcceptable(String requestedUser, OuterUserCredential connectionUser) {
       if (delegationMappings == null) {
           return false;
       }
   
       String[] allowedMappings = loadPropertyValue(connectionUser.getName(), connectionUser.getRealm());
       if (allowedMappings.length == 1 && "*".equals(allowedMappings[1])) {
           // A wild card mapping was found.
           return true;
       }
       for (String current : allowedMappings) {
           if (requestedUser.equals(current)) {
               return true;
           }
       }
       return false;
   }
   

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