/*
 * 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.zookeeper.server.quorum.auth;

import java.io.File;
import java.io.FileInputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.nio.charset.StandardCharsets;
import java.util.Arrays;
import java.util.HashSet;
import java.util.Locale;
import java.util.Map;
import java.util.Properties;
import java.util.Set;
import org.apache.kerby.kerberos.kerb.KrbException;
import org.apache.kerby.kerberos.kerb.server.KdcConfigKey;
import org.apache.kerby.kerberos.kerb.server.SimpleKdcServer;
import org.apache.kerby.util.IOUtil;
import org.apache.kerby.util.NetworkUtil;
import org.apache.zookeeper.server.ExitCode;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

/**
 * Mini KDC based on Apache Directory Server that can be embedded in testcases
 * or used from command line as a standalone KDC.
 * <p>
 * <b>From within testcases:</b>
 * <p>
 * MiniKdc sets one System property when started and un-set when stopped:
 * <ul>
 *   <li>sun.security.krb5.debug: set to the debug value provided in the
 *   configuration</li>
 * </ul>
 * Because of this, multiple MiniKdc instances cannot be started in parallel.
 * For example, running testcases in parallel that start a KDC each. To
 * accomplish this a single MiniKdc should be used for all testcases running
 * in parallel.
 * <p>
 * MiniKdc default configuration values are:
 * <ul>
 *   <li>org.name=EXAMPLE (used to create the REALM)</li>
 *   <li>org.domain=COM (used to create the REALM)</li>
 *   <li>kdc.bind.address=localhost</li>
 *   <li>kdc.port=0 (ephemeral port)</li>
 *   <li>instance=DefaultKrbServer</li>
 *   <li>max.ticket.lifetime=86400000 (1 day)</li>
 *   <li>max.renewable.lifetime=604800000 (7 days)</li>
 *   <li>transport=TCP</li>
 *   <li>debug=false</li>
 * </ul>
 * The generated krb5.conf forces TCP connections.
 */
/*
 * This code is originally from HDFS, see the file name MiniKdc there
 * in case of bug fixing, history, etc.
 *
 * Branch : trunk
 * Github Revision: 916140604ffef59466ba30832478311d3e6249bd
 */
public class MiniKdc {

    public static final String JAVA_SECURITY_KRB5_CONF = "java.security.krb5.conf";
    public static final String SUN_SECURITY_KRB5_DEBUG = "sun.security.krb5.debug";

    public static void main(String[] args) throws Exception {
        if (args.length < 4) {
            System.out.println("Arguments: <WORKDIR> <MINIKDCPROPERTIES> " + "<KEYTABFILE> [<PRINCIPALS>]+");
            System.exit(ExitCode.UNEXPECTED_ERROR.getValue());
        }
        File workDir = new File(args[0]);
        if (!workDir.exists()) {
            throw new RuntimeException("Specified work directory does not exists: " + workDir.getAbsolutePath());
        }
        Properties conf = createConf();
        File file = new File(args[1]);
        if (!file.exists()) {
            throw new RuntimeException("Specified configuration does not exists: " + file.getAbsolutePath());
        }
        Properties userConf = new Properties();
        InputStreamReader r = null;
        try {
            r = new InputStreamReader(new FileInputStream(file), StandardCharsets.UTF_8);
            userConf.load(r);
        } finally {
            if (r != null) {
                r.close();
            }
        }
        for (Map.Entry<?, ?> entry : userConf.entrySet()) {
            conf.put(entry.getKey(), entry.getValue());
        }
        final MiniKdc miniKdc = new MiniKdc(conf, workDir);
        miniKdc.start();
        File krb5conf = new File(workDir, "krb5.conf");
        if (miniKdc.getKrb5conf().renameTo(krb5conf)) {
            File keytabFile = new File(args[2]).getAbsoluteFile();
            String[] principals = new String[args.length - 3];
            System.arraycopy(args, 3, principals, 0, args.length - 3);
            miniKdc.createPrincipal(keytabFile, principals);
            System.out.println();
            System.out.println("Standalone MiniKdc Running");
            System.out.println("---------------------------------------------------");
            System.out.println("  Realm           : " + miniKdc.getRealm());
            System.out.println("  Running at      : " + miniKdc.getHost() + ":" + miniKdc.getHost());
            System.out.println("  krb5conf        : " + krb5conf);
            System.out.println();
            System.out.println("  created keytab  : " + keytabFile);
            System.out.println("  with principals : " + Arrays.asList(principals));
            System.out.println();
            System.out.println(" Do <CTRL-C> or kill <PID> to stop it");
            System.out.println("---------------------------------------------------");
            System.out.println();
            Runtime.getRuntime().addShutdownHook(new Thread() {
                @Override
                public void run() {
                    miniKdc.stop();
                }
            });
        } else {
            throw new RuntimeException("Cannot rename KDC's krb5conf to " + krb5conf.getAbsolutePath());
        }
    }

    private static final Logger LOG = LoggerFactory.getLogger(MiniKdc.class);

    public static final String ORG_NAME = "org.name";
    public static final String ORG_DOMAIN = "org.domain";
    public static final String KDC_BIND_ADDRESS = "kdc.bind.address";
    public static final String KDC_PORT = "kdc.port";
    public static final String INSTANCE = "instance";
    public static final String MAX_TICKET_LIFETIME = "max.ticket.lifetime";
    public static final String MAX_RENEWABLE_LIFETIME = "max.renewable.lifetime";
    public static final String TRANSPORT = "transport";
    public static final String DEBUG = "debug";

    private static final Set<String> PROPERTIES = new HashSet<String>();
    private static final Properties DEFAULT_CONFIG = new Properties();

    static {
        PROPERTIES.add(ORG_NAME);
        PROPERTIES.add(ORG_DOMAIN);
        PROPERTIES.add(KDC_BIND_ADDRESS);
        PROPERTIES.add(KDC_BIND_ADDRESS);
        PROPERTIES.add(KDC_PORT);
        PROPERTIES.add(INSTANCE);
        PROPERTIES.add(TRANSPORT);
        PROPERTIES.add(MAX_TICKET_LIFETIME);
        PROPERTIES.add(MAX_RENEWABLE_LIFETIME);

        DEFAULT_CONFIG.setProperty(KDC_BIND_ADDRESS, "localhost");
        DEFAULT_CONFIG.setProperty(KDC_PORT, "0");
        DEFAULT_CONFIG.setProperty(INSTANCE, "DefaultKrbServer");
        DEFAULT_CONFIG.setProperty(ORG_NAME, "EXAMPLE");
        DEFAULT_CONFIG.setProperty(ORG_DOMAIN, "COM");
        DEFAULT_CONFIG.setProperty(TRANSPORT, "TCP");
        DEFAULT_CONFIG.setProperty(MAX_TICKET_LIFETIME, "86400000");
        DEFAULT_CONFIG.setProperty(MAX_RENEWABLE_LIFETIME, "604800000");
        DEFAULT_CONFIG.setProperty(DEBUG, "false");
    }

    /**
     * Convenience method that returns MiniKdc default configuration.
     * <p>
     * The returned configuration is a copy, it can be customized before using
     * it to create a MiniKdc.
     * @return a MiniKdc default configuration.
     */
    public static Properties createConf() {
        return (Properties) DEFAULT_CONFIG.clone();
    }

    private Properties conf;
    private SimpleKdcServer simpleKdc;
    private int port;
    private String realm;
    private File workDir;
    private File krb5conf;
    private String transport;
    private boolean krb5Debug;

    public void setTransport(String transport) {
        this.transport = transport;
    }
    /**
     * Creates a MiniKdc.
     *
     * @param conf MiniKdc configuration.
     * @param workDir working directory, it should be the build directory. Under
     * this directory an ApacheDS working directory will be created, this
     * directory will be deleted when the MiniKdc stops.
     * @throws Exception thrown if the MiniKdc could not be created.
     */
    public MiniKdc(Properties conf, File workDir) throws Exception {
        if (!conf.keySet().containsAll(PROPERTIES)) {
            Set<String> missingProperties = new HashSet<String>(PROPERTIES);
            missingProperties.removeAll(conf.keySet());
            throw new IllegalArgumentException("Missing configuration properties: " + missingProperties);
        }
        this.workDir = new File(workDir, Long.toString(System.currentTimeMillis()));
        if (!this.workDir.exists() && !this.workDir.mkdirs()) {
            throw new RuntimeException("Cannot create directory " + this.workDir);
        }
        LOG.info("Configuration:");
        LOG.info("---------------------------------------------------------------");
        for (Map.Entry<?, ?> entry : conf.entrySet()) {
            LOG.info("  {}: {}", entry.getKey(), entry.getValue());
        }
        LOG.info("---------------------------------------------------------------");
        this.conf = conf;
        port = Integer.parseInt(conf.getProperty(KDC_PORT));
        String orgName = conf.getProperty(ORG_NAME);
        String orgDomain = conf.getProperty(ORG_DOMAIN);
        realm = orgName.toUpperCase(Locale.ENGLISH) + "." + orgDomain.toUpperCase(Locale.ENGLISH);
    }

    /**
     * Returns the port of the MiniKdc.
     *
     * @return the port of the MiniKdc.
     */
    public int getPort() {
        return port;
    }

    /**
     * Returns the host of the MiniKdc.
     *
     * @return the host of the MiniKdc.
     */
    public String getHost() {
        return conf.getProperty(KDC_BIND_ADDRESS);
    }

    /**
     * Returns the realm of the MiniKdc.
     *
     * @return the realm of the MiniKdc.
     */
    public String getRealm() {
        return realm;
    }

    public File getKrb5conf() {
        krb5conf = new File(System.getProperty(JAVA_SECURITY_KRB5_CONF));
        return krb5conf;
    }

    /**
     * Starts the MiniKdc.
     *
     * @throws Exception thrown if the MiniKdc could not be started.
     */
    public synchronized void start() throws Exception {
        if (simpleKdc != null) {
            throw new RuntimeException("Already started");
        }
        simpleKdc = new SimpleKdcServer();
        prepareKdcServer();
        simpleKdc.init();
        resetDefaultRealm();
        simpleKdc.start();
        LOG.info("MiniKdc stated.");
    }

    private void resetDefaultRealm() throws IOException {
        InputStream templateResource = new FileInputStream(getKrb5conf().getAbsolutePath());
        String content = IOUtil.readInput(templateResource);
        content = content.replaceAll("default_realm = .*\n", "default_realm = " + getRealm() + "\n");
        IOUtil.writeFile(content, getKrb5conf());
    }

    private void prepareKdcServer() throws Exception {
        // transport
        simpleKdc.setWorkDir(workDir);
        simpleKdc.setKdcHost(getHost());
        simpleKdc.setKdcRealm(realm);
        if (transport == null) {
            transport = conf.getProperty(TRANSPORT);
        }
        if (port == 0) {
            port = NetworkUtil.getServerPort();
        }
        if (transport != null) {
            if (transport.trim().equals("TCP")) {
                simpleKdc.setKdcTcpPort(port);
                simpleKdc.setAllowUdp(false);
            } else if (transport.trim().equals("UDP")) {
                simpleKdc.setKdcUdpPort(port);
                simpleKdc.setAllowTcp(false);
            } else {
                throw new IllegalArgumentException("Invalid transport: " + transport);
            }
        } else {
            throw new IllegalArgumentException("Need to set transport!");
        }
        simpleKdc.getKdcConfig().setString(KdcConfigKey.KDC_SERVICE_NAME, conf.getProperty(INSTANCE));
        if (conf.getProperty(DEBUG) != null) {
            krb5Debug = getAndSet(SUN_SECURITY_KRB5_DEBUG, conf.getProperty(DEBUG));
        }
    }

    /**
     * Stops the MiniKdc
     */
    public synchronized void stop() {
        if (simpleKdc != null) {
            try {
                simpleKdc.stop();
            } catch (KrbException e) {
                e.printStackTrace();
            } finally {
                if (conf.getProperty(DEBUG) != null) {
                    System.setProperty(SUN_SECURITY_KRB5_DEBUG, Boolean.toString(krb5Debug));
                }
            }
        }
        delete(workDir);
        try {
            // Will be fixed in next Kerby version.
            Thread.sleep(1000);
        } catch (InterruptedException e) {
            e.printStackTrace();
        }
        LOG.info("MiniKdc stopped.");
    }

    private void delete(File f) {
        if (f.isFile()) {
            if (!f.delete()) {
                LOG.warn("WARNING: cannot delete file {}", f.getAbsolutePath());
            }
        } else {
            for (File c : f.listFiles()) {
                delete(c);
            }
            if (!f.delete()) {
                LOG.warn("WARNING: cannot delete directory {}", f.getAbsolutePath());
            }
        }
    }

    /**
     * Creates a principal in the KDC with the specified user and password.
     *
     * @param principal principal name, do not include the domain.
     * @param password password.
     * @throws Exception thrown if the principal could not be created.
     */
    public synchronized void createPrincipal(String principal, String password) throws Exception {
        simpleKdc.createPrincipal(principal, password);
    }

    /**
     * Creates multiple principals in the KDC and adds them to a keytab file.
     *
     * @param keytabFile keytab file to add the created principals.
     * @param principals principals to add to the KDC, do not include the domain.
     * @throws Exception thrown if the principals or the keytab file could not be
     * created.
     */
    public synchronized void createPrincipal(File keytabFile, String... principals) throws Exception {
        simpleKdc.createPrincipals(principals);
        if (keytabFile.exists() && !keytabFile.delete()) {
            LOG.error("Failed to delete keytab file: {}", keytabFile);
        }
        for (String principal : principals) {
            simpleKdc.getKadmin().exportKeytab(keytabFile, principal);
        }
    }

    /**
     * Set the System property; return the old value for caching.
     *
     * @param sysprop property
     * @param debug true or false
     * @return the previous value
     */
    private boolean getAndSet(String sysprop, String debug) {
        boolean old = Boolean.getBoolean(sysprop);
        System.setProperty(sysprop, debug);
        return old;
    }

}
