/**
 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.
 * The ASF licenses this file to You 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.apache.activemq.security;

import java.security.Principal;
import java.security.cert.X509Certificate;

import javax.security.auth.Subject;
import javax.security.auth.callback.CallbackHandler;
import javax.security.auth.login.LoginContext;

import org.apache.activemq.broker.Broker;
import org.apache.activemq.broker.BrokerFilter;
import org.apache.activemq.broker.ConnectionContext;
import org.apache.activemq.command.ConnectionInfo;
import org.apache.activemq.jaas.JaasCertificateCallbackHandler;
import org.apache.activemq.jaas.UserPrincipal;

/**
 * A JAAS Authentication Broker that uses SSL Certificates. This class will
 * provide the JAAS framework with a JaasCertificateCallbackHandler that will
 * grant JAAS access to incoming connections' SSL certificate chains. NOTE:
 * There is a chance that the incoming connection does not have a valid
 * certificate (has null).
 */
public class JaasCertificateAuthenticationBroker extends BrokerFilter implements AuthenticationBroker {
    private final String jaasConfiguration;

    /**
     * Simple constructor. Leaves everything to superclass.
     *
     * @param next The Broker that does the actual work for this Filter.
     * @param jaasConfiguration The JAAS domain configuration name (refere to
     *                JAAS documentation).
     */
    public JaasCertificateAuthenticationBroker(Broker next, String jaasConfiguration) {
        super(next);

        this.jaasConfiguration = jaasConfiguration;
    }

    /**
     * Overridden to allow for authentication based on client certificates.
     * Connections being added will be authenticated based on their certificate
     * chain and the JAAS module specified through the JAAS framework. NOTE: The
     * security context's username will be set to the first UserPrincipal
     * created by the login module.
     *
     * @param context The context for the incoming Connection.
     * @param info The ConnectionInfo Command representing the incoming
     *                connection.
     */
    @Override
    public void addConnection(ConnectionContext context, ConnectionInfo info) throws Exception {

        if (context.getSecurityContext() == null) {
            if (!(info.getTransportContext() instanceof X509Certificate[])) {
                throw new SecurityException("Unable to authenticate transport without SSL certificate.");
            }

            // Set the TCCL since it seems JAAS needs it to find the login
            // module classes.
            ClassLoader original = Thread.currentThread().getContextClassLoader();
            Thread.currentThread().setContextClassLoader(JaasAuthenticationBroker.class.getClassLoader());
            try {
                SecurityContext s = authenticate(info.getUserName(), info.getPassword(), (X509Certificate[]) info.getTransportContext());
                context.setSecurityContext(s);
            } finally {
                Thread.currentThread().setContextClassLoader(original);
            }
        }
        super.addConnection(context, info);
    }

    /**
     * Overriding removeConnection to make sure the security context is cleaned.
     */
    @Override
    public void removeConnection(ConnectionContext context, ConnectionInfo info, Throwable error) throws Exception {
        super.removeConnection(context, info, error);

        context.setSecurityContext(null);
    }

    @Override
    public SecurityContext authenticate(String username, String password, X509Certificate[] peerCertificates) throws SecurityException {
        try {
            CallbackHandler callback = new JaasCertificateCallbackHandler(peerCertificates);
            LoginContext lc = new LoginContext(jaasConfiguration, callback);
            lc.login();
            Subject subject = lc.getSubject();

            String dnName = "";

            for (Principal principal : subject.getPrincipals()) {
                if (principal instanceof UserPrincipal) {
                    dnName = ((UserPrincipal)principal).getName();
                    break;
                }
            }

            return new JaasCertificateSecurityContext(dnName, subject, peerCertificates);
        } catch (Exception e) {
            throw new SecurityException("User name [" + username + "] or password is invalid. " + e.getMessage(), e);
        }
    }
}