Exploring Apache Shiro

I was looking at some implementations for "RememberMe" or persistent login functionality and came across Apache Shiro. From the project website:

"Apache Shiro is a powerful and easy-to-use Java security framework that performs authentication, authorization, cryptography, and session management. With Shiro’s easy-to-understand API, you can quickly and easily secure any application – from the smallest mobile applications to the largest web and enterprise applications."

It was an interesting find. For the first time, I saw a session management implementation that is simple and works outside a web container. Indeed the APIs were simple enough to use in an application. While the documentation is reasonably good, I could not find an end-to-end sample with a configuration. So here is something I wrote to play with the APIs.

This code is implements a standalone Username and Password based authentication module. The dummy realm implementation simply returns an empty credential (User Info) pair. So if you plan to use database backed authentication, substitute the dummy implementation with say JDBC code or use JdbcRealm.

1. Create shiro.ini that will be used to initialize Shiro's SecurityManager.

[main]
sessionManager = org.apache.shiro.session.mgt.DefaultSessionManager

# ensure the securityManager uses our native SessionManager
securityManager.sessionManager = $sessionManager

#set the sessionManager to use an enterprise cache for backing storage:
sessionDAO = org.apache.shiro.session.mgt.eis.EnterpriseCacheSessionDAO
securityManager.sessionManager.sessionDAO = $sessionDAO

cacheManager = org.apache.shiro.cache.ehcache.EhCacheManager
securityManager.cacheManager = $cacheManager

# Session validation
sessionValidationScheduler = org.apache.shiro.session.mgt.ExecutorServiceSessionValidationScheduler

# Session timeout  
securityManager.sessionManager.globalSessionTimeout = 3600000

# Default is 3,600,000 millis = 1 hour:
sessionValidationScheduler.interval = 3600000

sessionValidationScheduler.sessionManager = $sessionManager

# Auth
myRealm = com.session.security.shiro.auth.CustomRealm
myRealmCredentialsMatcher = org.apache.shiro.authc.credential.AllowAllCredentialsMatcher
myRealm.credentialsMatcher = $myRealmCredentialsMatcher

#Remember Me
rememberMe = org.apache.shiro.web.mgt.CookieRememberMeManager
securityManager.rememberMeManager = $rememberMe

[users]

[roles]

[urls]

Note: We are using  AllowAllCredentialsMatcher that always returns true while matching credentials. The configuration also uses EhCache for storing sessions. Also note that  DefaultSessionManager does not have a default implementation for "RememberMe". Take a look at DefaultWebSecurityManager. It uses CookieRememberMeManager as a default implementation which is useful in a webapp.

2. Custom Realm

public class CustomRealm extends AuthenticatingRealm {

 private CredentialsMatcher credentialsMatcher;
 
 public String getName() {
  return "CustomRealm";
 }

 public boolean supports(AuthenticationToken token) {
  return true;
 }

    public CredentialsMatcher getCredentialsMatcher() {
        return credentialsMatcher;
    }
    
    public void setCredentialsMatcher(CredentialsMatcher credentialsMatcher) {
        this.credentialsMatcher = credentialsMatcher;
    }

 @Override
 protected AuthenticationInfo doGetAuthenticationInfo(
   AuthenticationToken token) throws AuthenticationException {
  return new SimpleAuthenticationInfo("", "".toCharArray(), getName());
 }
}

3. Auth Code:

import java.io.Serializable;

import org.apache.shiro.SecurityUtils;
import org.apache.shiro.authc.UsernamePasswordToken;
import org.apache.shiro.config.IniSecurityManagerFactory;
import org.apache.shiro.mgt.SecurityManager;
import org.apache.shiro.session.Session;
import org.apache.shiro.subject.Subject;
import org.apache.shiro.util.Factory;

public class ShiroAuthService {

 public ShiroAuthService() {
  Factory factory = new IniSecurityManagerFactory(
    "classpath:shiro.ini");
  SecurityManager securityManager = factory.getInstance();
  // Make the SecurityManager instance available to the entire application
  // via static memory:
  SecurityUtils.setSecurityManager(securityManager);
 }

 public void testAuth() {

  // simulate a username/password (plaintext) token created in response to
  // a login attempt:
  UsernamePasswordToken token = new UsernamePasswordToken("user", "secret");
  token.setRememberMe(true);

  boolean loggedIn = false;
  Session session = null;
  Subject currentUser = SecurityUtils.getSubject();

  try {
   currentUser.login(token);
   session = currentUser.getSession();
   System.out.println("Session Id: " + session.getId());
   loggedIn = true;
  } catch (Exception ex) {
   loggedIn = false;
  }

  Serializable sessionId = session.getId();
  if (loggedIn) {
   Subject requestSubject = new Subject.Builder().sessionId(sessionId)
     .buildSubject();
   System.out.println("Is Authenticated = "
     + requestSubject.isAuthenticated());//Should return true
   System.out.println("Is Remembered = "
     + requestSubject.isRemembered());
  } else {
   System.out.println("Not logged in.");
  }

  System.exit(0);
 }

 public static void main(String[] args) {
  new ShiroAuthService().testAuth();
 }
}

There are some other interesting features. It has a nice pluggable architecture wherein you can provide custom implementations of SessionManager, Realm, Caching, CredentialMatching, SessionDAO and "RememberMe".

For implementing a custom matcher, go with "public class CustomMatcher extends CodecSupport implements CredentialsMatcher". Similary, for a custom Realm implementation, use: "public class CustomRealm extends AuthenticatingRealm" as the base class provides some useful functionality. Of-course you can provide an implementation from scratch.

For more samples, see http://svn.apache.org/repos/asf/shiro/tags/shiro-root-1.2.1/samples/.