/*
 * 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.karaf.shell.ssh;

import java.io.IOException;
import java.security.Principal;

import javax.security.auth.Subject;
import javax.security.auth.callback.Callback;
import javax.security.auth.callback.CallbackHandler;
import javax.security.auth.callback.NameCallback;
import javax.security.auth.callback.PasswordCallback;
import javax.security.auth.callback.UnsupportedCallbackException;
import javax.security.auth.login.FailedLoginException;
import javax.security.auth.login.LoginContext;

import org.apache.sshd.common.Session;
import org.apache.sshd.server.PasswordAuthenticator;
import org.apache.sshd.server.session.ServerSession;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

/**
 * TODO Add javadoc
 *
 * @author <a href="mailto:dev@mina.apache.org">Apache MINA SSHD Project</a>
 */
public class KarafJaasPasswordAuthenticator implements PasswordAuthenticator {

    public static final Session.AttributeKey<Subject> SUBJECT_ATTRIBUTE_KEY = new Session.AttributeKey<Subject>();
    private final Logger LOGGER = LoggerFactory.getLogger(KarafJaasPasswordAuthenticator.class);

    private String realm;
    private String role;

    public String getRealm() {
        return realm;
    }

    public void setRealm(String realm) {
        this.realm = realm;
    }

    public String getRole() {
        return role;
    }

    public void setRole(String role) {
        this.role = role;
    }

    public boolean authenticate(final String username, final String password, final ServerSession session) {
        try {
            Subject subject = new Subject();
            LoginContext loginContext = new LoginContext(realm, subject, new CallbackHandler() {
                public void handle(Callback[] callbacks) throws IOException, UnsupportedCallbackException {
                    for (Callback callback : callbacks) {
                        if (callback instanceof NameCallback) {
                            ((NameCallback) callback).setName(username);
                        } else if (callback instanceof PasswordCallback) {
                            ((PasswordCallback) callback).setPassword(password.toCharArray());
                        } else {
                            throw new UnsupportedCallbackException(callback);
                        }
                    }
                }
            });
            loginContext.login();
            if (role != null && role.length() > 0) {
                String clazz = "org.apache.karaf.jaas.modules.RolePrincipal";
                String name = role;
                int idx = role.indexOf(':');
                if (idx > 0) {
                    clazz = role.substring(0, idx);
                    name = role.substring(idx + 1);
                }
                boolean found = false;
                for (Principal p : subject.getPrincipals()) {
                    if (p.getClass().getName().equals(clazz)
                            && p.getName().equals(name)) {
                        found = true;
                        break;
                    }
                }
                if (!found) {
                    throw new FailedLoginException("User does not have the required role " + role);
                }
            }
            session.setAttribute(SUBJECT_ATTRIBUTE_KEY, subject);
            return true;
        } catch (Exception e) {
            LOGGER.debug("User authentication failed with " + e.getMessage(), e);
            return false;
        }
    }

}
