/*
 * Copyright 2010-2016 the original author or authors.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
package org.springframework.security.authentication.jaas;

import java.io.IOException;
import java.security.Principal;
import java.util.ArrayList;
import java.util.HashSet;
import java.util.List;
import java.util.Set;

import javax.security.auth.callback.Callback;
import javax.security.auth.callback.CallbackHandler;
import javax.security.auth.callback.UnsupportedCallbackException;
import javax.security.auth.login.LoginContext;
import javax.security.auth.login.LoginException;

import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;

import org.springframework.beans.factory.InitializingBean;
import org.springframework.context.ApplicationEventPublisher;
import org.springframework.context.ApplicationEventPublisherAware;
import org.springframework.context.ApplicationListener;
import org.springframework.security.authentication.AuthenticationProvider;
import org.springframework.security.authentication.UsernamePasswordAuthenticationToken;
import org.springframework.security.authentication.jaas.event.JaasAuthenticationFailedEvent;
import org.springframework.security.authentication.jaas.event.JaasAuthenticationSuccessEvent;
import org.springframework.security.core.Authentication;
import org.springframework.security.core.AuthenticationException;
import org.springframework.security.core.GrantedAuthority;
import org.springframework.security.core.context.SecurityContext;
import org.springframework.security.core.session.SessionDestroyedEvent;
import org.springframework.util.Assert;
import org.springframework.util.ObjectUtils;

/**
 * An {@link AuthenticationProvider} implementation that retrieves user details from a
 * JAAS login configuration.
 *
 * <p>
 * This <code>AuthenticationProvider</code> is capable of validating
 * {@link org.springframework.security.authentication.UsernamePasswordAuthenticationToken}
 * requests contain the correct username and password.
 *
 * <p>
 * This implementation is backed by a
 * <a href="http://java.sun.com/j2se/1.5.0/docs/guide/security/jaas/JAASRefGuide.html" >
 * JAAS</a> configuration that is provided by a subclass's implementation of
 * {@link #createLoginContext(CallbackHandler)}.
 *
 * <p>
 * When using JAAS login modules as the authentication source, sometimes the <a href=
 * "http://java.sun.com/j2se/1.5.0/docs/api/javax/security/auth/login/LoginContext.html" >
 * LoginContext</a> will require <i>CallbackHandler</i>s. The
 * AbstractJaasAuthenticationProvider uses an internal <a href=
 * "http://java.sun.com/j2se/1.5.0/docs/api/javax/security/auth/callback/CallbackHandler.html"
 * >CallbackHandler </a> to wrap the {@link JaasAuthenticationCallbackHandler}s configured
 * in the ApplicationContext. When the LoginContext calls the internal CallbackHandler,
 * control is passed to each {@link JaasAuthenticationCallbackHandler} for each Callback
 * passed.
 *
 * <p>
 * {@link JaasAuthenticationCallbackHandler}s are passed to the
 * AbstractJaasAuthenticationProvider through the
 * {@link #setCallbackHandlers(org.springframework.security.authentication.jaas.JaasAuthenticationCallbackHandler[])
 * callbackHandlers} property.
 *
 * <pre>
 * &lt;property name="callbackHandlers"&gt;
 *   &lt;list&gt;
 *     &lt;bean class="org.springframework.security.authentication.jaas.TestCallbackHandler"/&gt;
 *     &lt;bean class="{@link JaasNameCallbackHandler org.springframework.security.authentication.jaas.JaasNameCallbackHandler}"/&gt;
 *     &lt;bean class="{@link JaasPasswordCallbackHandler org.springframework.security.authentication.jaas.JaasPasswordCallbackHandler}"/&gt;
 *  &lt;/list&gt;
 * &lt;/property&gt;
 * </pre>
 *
 * <p>
 * After calling LoginContext.login(), the AbstractJaasAuthenticationProvider will
 * retrieve the returned Principals from the Subject
 * (LoginContext.getSubject().getPrincipals). Each returned principal is then passed to
 * the configured {@link AuthorityGranter}s. An AuthorityGranter is a mapping between a
 * returned Principal, and a role name. If an AuthorityGranter wishes to grant an
 * Authorization a role, it returns that role name from it's
 * {@link AuthorityGranter#grant(java.security.Principal)} method. The returned role will
 * be applied to the Authorization object as a {@link GrantedAuthority}.
 *
 * <p>
 * AuthorityGranters are configured in spring xml as follows...
 *
 * <pre>
 * &lt;property name="authorityGranters"&gt;
 *   &lt;list&gt;
 *     &lt;bean class="org.springframework.security.authentication.jaas.TestAuthorityGranter"/&gt;
 *   &lt;/list&gt;
 *  &lt;/property&gt;
 * </pre>
 *
 * @author Ray Krueger
 * @author Rob Winch
 */
public abstract class AbstractJaasAuthenticationProvider
		implements AuthenticationProvider, ApplicationEventPublisherAware,
		InitializingBean, ApplicationListener<SessionDestroyedEvent> {
	// ~ Instance fields
	// ================================================================================================

	private ApplicationEventPublisher applicationEventPublisher;
	private AuthorityGranter[] authorityGranters;
	private JaasAuthenticationCallbackHandler[] callbackHandlers;
	protected final Log log = LogFactory.getLog(getClass());
	private LoginExceptionResolver loginExceptionResolver = new DefaultLoginExceptionResolver();
	private String loginContextName = "SPRINGSECURITY";

	// ~ Methods
	// ========================================================================================================

	/**
	 * Validates the required properties are set. In addition, if
	 * {@link #setCallbackHandlers(JaasAuthenticationCallbackHandler[])} has not been
	 * called with valid handlers, initializes to use {@link JaasNameCallbackHandler} and
	 * {@link JaasPasswordCallbackHandler}.
	 */
	public void afterPropertiesSet() throws Exception {
		Assert.hasLength(this.loginContextName,
				"loginContextName cannot be null or empty");
		Assert.notEmpty(this.authorityGranters,
				"authorityGranters cannot be null or empty");
		if (ObjectUtils.isEmpty(this.callbackHandlers)) {
			setCallbackHandlers(new JaasAuthenticationCallbackHandler[] {
					new JaasNameCallbackHandler(), new JaasPasswordCallbackHandler() });
		}
		Assert.notNull(this.loginExceptionResolver,
				"loginExceptionResolver cannot be null");
	}

	/**
	 * Attempts to login the user given the Authentication objects principal and
	 * credential
	 *
	 * @param auth The Authentication object to be authenticated.
	 *
	 * @return The authenticated Authentication object, with it's grantedAuthorities set.
	 *
	 * @throws AuthenticationException This implementation does not handle 'locked' or
	 * 'disabled' accounts. This method only throws a AuthenticationServiceException, with
	 * the message of the LoginException that will be thrown, should the
	 * loginContext.login() method fail.
	 */
	public Authentication authenticate(Authentication auth)
			throws AuthenticationException {
		if (!(auth instanceof UsernamePasswordAuthenticationToken)) {
			return null;
		}

		UsernamePasswordAuthenticationToken request = (UsernamePasswordAuthenticationToken) auth;
		Set<GrantedAuthority> authorities;

		try {
			// Create the LoginContext object, and pass our InternallCallbackHandler
			LoginContext loginContext = createLoginContext(
					new InternalCallbackHandler(auth));

			// Attempt to login the user, the LoginContext will call our
			// InternalCallbackHandler at this point.
			loginContext.login();

			// Create a set to hold the authorities, and add any that have already been
			// applied.
			authorities = new HashSet<>();

			// Get the subject principals and pass them to each of the AuthorityGranters
			Set<Principal> principals = loginContext.getSubject().getPrincipals();

			for (Principal principal : principals) {
				for (AuthorityGranter granter : this.authorityGranters) {
					Set<String> roles = granter.grant(principal);

					// If the granter doesn't wish to grant any authorities, it should
					// return null.
					if ((roles != null) && !roles.isEmpty()) {
						for (String role : roles) {
							authorities.add(new JaasGrantedAuthority(role, principal));
						}
					}
				}
			}

			// Convert the authorities set back to an array and apply it to the token.
			JaasAuthenticationToken result = new JaasAuthenticationToken(
					request.getPrincipal(), request.getCredentials(),
					new ArrayList<>(authorities), loginContext);

			// Publish the success event
			publishSuccessEvent(result);

			// we're done, return the token.
			return result;

		}
		catch (LoginException loginException) {
			AuthenticationException ase = this.loginExceptionResolver
					.resolveException(loginException);

			publishFailureEvent(request, ase);
			throw ase;
		}
	}

	/**
	 * Creates the LoginContext to be used for authentication.
	 *
	 * @param handler The CallbackHandler that should be used for the LoginContext (never
	 * <code>null</code>).
	 * @return the LoginContext to use for authentication.
	 * @throws LoginException
	 */
	protected abstract LoginContext createLoginContext(CallbackHandler handler)
			throws LoginException;

	/**
	 * Handles the logout by getting the security contexts for the destroyed session and
	 * invoking {@code LoginContext.logout()} for any which contain a
	 * {@code JaasAuthenticationToken}.
	 *
	 *
	 * @param event the session event which contains the current session
	 */
	protected void handleLogout(SessionDestroyedEvent event) {
		List<SecurityContext> contexts = event.getSecurityContexts();

		if (contexts.isEmpty()) {
			this.log.debug("The destroyed session has no SecurityContexts");

			return;
		}

		for (SecurityContext context : contexts) {
			Authentication auth = context.getAuthentication();

			if ((auth != null) && (auth instanceof JaasAuthenticationToken)) {
				JaasAuthenticationToken token = (JaasAuthenticationToken) auth;

				try {
					LoginContext loginContext = token.getLoginContext();
					boolean debug = this.log.isDebugEnabled();
					if (loginContext != null) {
						if (debug) {
							this.log.debug("Logging principal: [" + token.getPrincipal()
									+ "] out of LoginContext");
						}
						loginContext.logout();
					}
					else if (debug) {
						this.log.debug("Cannot logout principal: [" + token.getPrincipal()
								+ "] from LoginContext. "
								+ "The LoginContext is unavailable");
					}
				}
				catch (LoginException e) {
					this.log.warn("Error error logging out of LoginContext", e);
				}
			}
		}
	}

	public void onApplicationEvent(SessionDestroyedEvent event) {
		handleLogout(event);
	}

	/**
	 * Publishes the {@link JaasAuthenticationFailedEvent}. Can be overridden by
	 * subclasses for different functionality
	 *
	 * @param token The authentication token being processed
	 * @param ase The excetion that caused the authentication failure
	 */
	protected void publishFailureEvent(UsernamePasswordAuthenticationToken token,
			AuthenticationException ase) {
		if (this.applicationEventPublisher != null) {
			this.applicationEventPublisher
					.publishEvent(new JaasAuthenticationFailedEvent(token, ase));
		}
	}

	/**
	 * Publishes the {@link JaasAuthenticationSuccessEvent}. Can be overridden by
	 * subclasses for different functionality.
	 *
	 * @param token The token being processed
	 */
	protected void publishSuccessEvent(UsernamePasswordAuthenticationToken token) {
		if (this.applicationEventPublisher != null) {
			this.applicationEventPublisher
					.publishEvent(new JaasAuthenticationSuccessEvent(token));
		}
	}

	/**
	 * Returns the AuthorityGrannter array that was passed to the
	 * {@link #setAuthorityGranters(AuthorityGranter[])} method, or null if it none were
	 * ever set.
	 *
	 * @return The AuthorityGranter array, or null
	 *
	 * @see #setAuthorityGranters(AuthorityGranter[])
	 */
	AuthorityGranter[] getAuthorityGranters() {
		return this.authorityGranters;
	}

	/**
	 * Set the AuthorityGranters that should be consulted for role names to be granted to
	 * the Authentication.
	 *
	 * @param authorityGranters AuthorityGranter array
	 *
	 * @see JaasAuthenticationProvider
	 */
	public void setAuthorityGranters(AuthorityGranter[] authorityGranters) {
		this.authorityGranters = authorityGranters;
	}

	/**
	 * Returns the current JaasAuthenticationCallbackHandler array, or null if none are
	 * set.
	 *
	 * @return the JAASAuthenticationCallbackHandlers.
	 *
	 * @see #setCallbackHandlers(JaasAuthenticationCallbackHandler[])
	 */
	JaasAuthenticationCallbackHandler[] getCallbackHandlers() {
		return this.callbackHandlers;
	}

	/**
	 * Set the JAASAuthentcationCallbackHandler array to handle callback objects generated
	 * by the LoginContext.login method.
	 *
	 * @param callbackHandlers Array of JAASAuthenticationCallbackHandlers
	 */
	public void setCallbackHandlers(
			JaasAuthenticationCallbackHandler[] callbackHandlers) {
		this.callbackHandlers = callbackHandlers;
	}

	String getLoginContextName() {
		return this.loginContextName;
	}

	/**
	 * Set the loginContextName, this name is used as the index to the configuration
	 * specified in the loginConfig property.
	 *
	 * @param loginContextName
	 */
	public void setLoginContextName(String loginContextName) {
		this.loginContextName = loginContextName;
	}

	LoginExceptionResolver getLoginExceptionResolver() {
		return this.loginExceptionResolver;
	}

	public void setLoginExceptionResolver(LoginExceptionResolver loginExceptionResolver) {
		this.loginExceptionResolver = loginExceptionResolver;
	}

	public boolean supports(Class<?> aClass) {
		return UsernamePasswordAuthenticationToken.class.isAssignableFrom(aClass);
	}

	public void setApplicationEventPublisher(
			ApplicationEventPublisher applicationEventPublisher) {
		this.applicationEventPublisher = applicationEventPublisher;
	}

	protected ApplicationEventPublisher getApplicationEventPublisher() {
		return this.applicationEventPublisher;
	}

	// ~ Inner Classes
	// ==================================================================================================

	/**
	 * Wrapper class for JAASAuthenticationCallbackHandlers
	 */
	private class InternalCallbackHandler implements CallbackHandler {
		private final Authentication authentication;

		public InternalCallbackHandler(Authentication authentication) {
			this.authentication = authentication;
		}

		public void handle(Callback[] callbacks)
				throws IOException, UnsupportedCallbackException {
			for (JaasAuthenticationCallbackHandler handler : AbstractJaasAuthenticationProvider.this.callbackHandlers) {
				for (Callback callback : callbacks) {
					handler.handle(callback, this.authentication);
				}
			}
		}
	}
}
