How to implement a new realm in Tomcat

How to implement a new realm in Tomcat

Posted bySiddhartha De on June 20, 2017 June 19, 2017

Tomcat by default ships with a couple of Realm implementations like, JDBCRealm , DataSourceRealm , and JNDIRealm etc. But sometimes it is not sufficient for your organization’s requirements and you are required to apply your own implementations.

How to implement a custom realm in Tomcat?

You can create your own realm by extending RealmBase class; here I am going to show an example of implementing a new Realm in Tomcat.

Here is a sample code snip for implementing a new Realm by extending RealmBase class:

package com.sid.realm;
import java.security.Principal;
import java.util.ArrayList;
import java.util.List;
import org.apache.catalina.realm.RealmBase;
import org.apache.catalina.realm.GenericPrincipal;
import org.jboss.logging.Logger;
 /*
 * @author siddhartha
 */
public class NewRealm extends RealmBase {
 
 private String username;
 private String password;
 protected static Logger log = Logger.getLogger(NewRealm.class);

 @Override
 public Principal authenticate(String username, String credentials) {

 this.username = username;
 this.password = credentials;
 log.info("Authentication is taking place with userid: "+username);
 /* authentication just check the username and password is same*/
 if (this.username.equals(this.password)) {
   return getPrincipal(username);
  }else{
   return null;
  }
 }
 @Override
 protected String getName() {
  return username;
 }

 @Override
 protected String getPassword(String username) {
  return password;
 }

 @Override
 protected Principal getPrincipal(String string) {
  List roles = new ArrayList();
  roles.add("TomcatAdmin");  // Adding role "TomcatAdmin" role to the user
  log.info("Realm: "+this);
  Principal principal = new GenericPrincipal(username, password,roles);
  log.info("Principal: "+principal);
  return principal;
 }
}

This code can be compiled using maven by executing following instructions:

  1. Create a project using maven by executing the below command.
    mvn archetype:generate -DgroupId=com.sid.realm -DartifactId=realm -DarchetypeArtifactId=maven-archetype-quickstart -DinteractiveMode=false
  2. Place NewRealm.java at src/main/java/com/sid/realm .
  3. Edit pom.xml and add the following dependencies.
      
       org.apache.tomcat
       tomcat-catalina
       7.0.27
       jar
      
     
  4. Execute the command below to build the package.
    mvn clean package
  5. If the build is successful, it will generate realm-1.0-SNAPSHOT.jar at target directory, place this jar at $CATALINA_HOME/lib .
  6. Now make the following changes in $CATALINA_HOME/conf/server.xml , if you want to enable this realm for all the application deployed in Tomcat. If you want to enable this realm for a specific application, make the following changes in context.xml placed at application’s META-INF folder.
  7. Start tomcat and test your application now.

Note:In the code, role is set as TomcatAdmin , make sure the same role is implemented in web.xml in your application, or you may get a 403 error.

POC is available at GitHub

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