/*

 * Copyright (c) 2000, 2018, Oracle and/or its affiliates. All rights reserved.

 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.

 *

 * This code is free software; you can redistribute it and/or modify it

 * under the terms of the GNU General Public License version 2 only, as

 * published by the Free Software Foundation.  Oracle designates this

 * particular file as subject to the "Classpath" exception as provided

 * by Oracle in the LICENSE file that accompanied this code.

 *

 * This code is distributed in the hope that it will be useful, but WITHOUT

 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or

 * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License

 * version 2 for more details (a copy is included in the LICENSE file that

 * accompanied this code).

 *

 * You should have received a copy of the GNU General Public License version

 * 2 along with this work; if not, write to the Free Software Foundation,

 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.

 *

 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA

 * or visit www.oracle.com if you need additional information or have any

 * questions.

 */

/*

 *

 *  (C) Copyright IBM Corp. 1999 All Rights Reserved.

 *  Copyright 1997 The Open Group Research Institute.  All rights reserved.

 */

package sun.security.krb5;

import java.security.PrivilegedAction;

import java.security.Security;

import java.util.Locale;

import sun.security.krb5.internal.Krb5;

import sun.security.krb5.internal.NetClient;

import java.io.IOException;

import java.net.SocketTimeoutException;

import java.util.StringTokenizer;

import java.security.AccessController;

import java.security.PrivilegedExceptionAction;

import java.security.PrivilegedActionException;

import java.util.ArrayList;

import java.util.List;

import java.util.Set;

import java.util.HashSet;

import java.util.Iterator;

import sun.security.krb5.internal.KRBError;

/**

 * KDC-REQ/KDC-REP communication. No more base class for KrbAsReq and

 * KrbTgsReq. This class is now communication only.

 */

public final class KdcComm {

    // The following settings can be configured in [libdefaults]

    // section of krb5.conf, which are global for all realms. Each of

    // them can also be defined in a realm, which overrides value here.

    /**

     * max retry time for a single KDC, default Krb5.KDC_RETRY_LIMIT (3)

     */

    private static int defaultKdcRetryLimit;

    /**

     * timeout requesting a ticket from KDC, in millisec, default 30 sec

     */

    private static int defaultKdcTimeout;

    /**

     * max UDP packet size, default unlimited (-1)

     */

    private static int defaultUdpPrefLimit;

    private static final boolean DEBUG = Krb5.DEBUG;

    /**

     * What to do when a KDC is unavailable, specified in the

     * java.security file with key krb5.kdc.bad.policy.

     * Possible values can be TRY_LAST or TRY_LESS. Reloaded when refreshed.

     */

    private enum BpType {

        NONE, TRY_LAST, TRY_LESS

    }

    private static int tryLessMaxRetries = 1;

    private static int tryLessTimeout = 5000;

    private static BpType badPolicy;

    static {

        initStatic();

    }

    /**

     * Read global settings

     */

    public static void initStatic() {

        String value = AccessController.doPrivileged(

        new PrivilegedAction<String>() {

            public String run() {

                return Security.getProperty("krb5.kdc.bad.policy");

            }

        });

        if (value != null) {

            value = value.toLowerCase(Locale.ENGLISH);

            String[] ss = value.split(":");

            if ("tryless".equals(ss[0])) {

                if (ss.length > 1) {

                    String[] params = ss[1].split(",");

                    try {

                        int tmp0 = Integer.parseInt(params[0]);

                        if (params.length > 1) {

                            tryLessTimeout = Integer.parseInt(params[1]);

                        }

                        // Assign here in case of exception at params[1]

                        tryLessMaxRetries = tmp0;

                    } catch (NumberFormatException nfe) {

                        // Ignored. Please note that tryLess is recognized and

                        // used, parameters using default values

                        if (DEBUG) {

                            System.out.println("Invalid krb5.kdc.bad.policy" +

                                    " parameter for tryLess: " +

                                    value + ", use default");

                        }

                    }

                }

                badPolicy = BpType.TRY_LESS;

            } else if ("trylast".equals(ss[0])) {

                badPolicy = BpType.TRY_LAST;

            } else {

                badPolicy = BpType.NONE;

            }

        } else {

            badPolicy = BpType.NONE;

        }

        int timeout = -1;

        int max_retries = -1;

        int udp_pref_limit = -1;

        try {

            Config cfg = Config.getInstance();

            String temp = cfg.get("libdefaults", "kdc_timeout");

            timeout = parseTimeString(temp);

            temp = cfg.get("libdefaults", "max_retries");

            max_retries = parsePositiveIntString(temp);

            temp = cfg.get("libdefaults", "udp_preference_limit");

            udp_pref_limit = parsePositiveIntString(temp);

        } catch (Exception exc) {

           // ignore any exceptions; use default values

           if (DEBUG) {

                System.out.println ("Exception in getting KDC communication " +

                                    "settings, using default value " +

                                    exc.getMessage());

           }

        }

        defaultKdcTimeout = timeout > 0 ? timeout : 30*1000; // 30 seconds

        defaultKdcRetryLimit =

                max_retries > 0 ? max_retries : Krb5.KDC_RETRY_LIMIT;

        if (udp_pref_limit < 0) {

            defaultUdpPrefLimit = Krb5.KDC_DEFAULT_UDP_PREF_LIMIT;

        } else if (udp_pref_limit > Krb5.KDC_HARD_UDP_LIMIT) {

            defaultUdpPrefLimit = Krb5.KDC_HARD_UDP_LIMIT;

        } else {

            defaultUdpPrefLimit = udp_pref_limit;

        }

        KdcAccessibility.reset();

    }

    /**

     * The instance fields

     */

    private String realm;

    public KdcComm(String realm) throws KrbException {

        if (realm == null) {

           realm = Config.getInstance().getDefaultRealm();

            if (realm == null) {

                throw new KrbException(Krb5.KRB_ERR_GENERIC,

                                       "Cannot find default realm");

            }

        }

        this.realm = realm;

    }

    public byte[] send(byte[] obuf)

        throws IOException, KrbException {

        int udpPrefLimit = getRealmSpecificValue(

                realm, "udp_preference_limit", defaultUdpPrefLimit);

        boolean useTCP = (udpPrefLimit > 0 &&

             (obuf != null && obuf.length > udpPrefLimit));

        return send(obuf, useTCP);

    }

    private byte[] send(byte[] obuf, boolean useTCP)

        throws IOException, KrbException {

        if (obuf == null)

            return null;

        Config cfg = Config.getInstance();

        if (realm == null) {

            realm = cfg.getDefaultRealm();

            if (realm == null) {

                throw new KrbException(Krb5.KRB_ERR_GENERIC,

                                       "Cannot find default realm");

            }

        }

        String kdcList = cfg.getKDCList(realm);

        if (kdcList == null) {

            throw new KrbException("Cannot get kdc for realm " + realm);

        }

        // tempKdc may include the port number also

        Iterator<String> tempKdc = KdcAccessibility.list(kdcList).iterator();

        if (!tempKdc.hasNext()) {

            throw new KrbException("Cannot get kdc for realm " + realm);

        }

        byte[] ibuf = null;

        try {

            ibuf = sendIfPossible(obuf, tempKdc.next(), useTCP);

        } catch(Exception first) {

            boolean ok = false;

            while(tempKdc.hasNext()) {

                try {

                    ibuf = sendIfPossible(obuf, tempKdc.next(), useTCP);

                    ok = true;

                    break;

                } catch(Exception ignore) {}

            }

            if (!ok) throw first;

        }

        if (ibuf == null) {

            throw new IOException("Cannot get a KDC reply");

        }

        return ibuf;

    }

    // send the AS Request to the specified KDC

    // failover to using TCP if useTCP is not set and response is too big

    private byte[] sendIfPossible(byte[] obuf, String tempKdc, boolean useTCP)

        throws IOException, KrbException {

        try {

            byte[] ibuf = send(obuf, tempKdc, useTCP);

            KRBError ke = null;

            try {

                ke = new KRBError(ibuf);

            } catch (Exception e) {

                // OK

            }

            if (ke != null && ke.getErrorCode() ==

                    Krb5.KRB_ERR_RESPONSE_TOO_BIG) {

                ibuf = send(obuf, tempKdc, true);

            }

            KdcAccessibility.removeBad(tempKdc);

            return ibuf;

        } catch(Exception e) {

            if (DEBUG) {

                System.out.println(">>> KrbKdcReq send: error trying " +

                        tempKdc);

                e.printStackTrace(System.out);

            }

            KdcAccessibility.addBad(tempKdc);

            throw e;

        }

    }

    // send the AS Request to the specified KDC

    private byte[] send(byte[] obuf, String tempKdc, boolean useTCP)

        throws IOException, KrbException {

        if (obuf == null)

            return null;

        int port = Krb5.KDC_INET_DEFAULT_PORT;

        int retries = getRealmSpecificValue(

                realm, "max_retries", defaultKdcRetryLimit);

        int timeout = getRealmSpecificValue(

                realm, "kdc_timeout", defaultKdcTimeout);

        if (badPolicy == BpType.TRY_LESS &&

                KdcAccessibility.isBad(tempKdc)) {

            if (retries > tryLessMaxRetries) {

                retries = tryLessMaxRetries; // less retries

            }

            if (timeout > tryLessTimeout) {

                timeout = tryLessTimeout; // less time

            }

        }

        String kdc = null;

        String portStr = null;

        if (tempKdc.charAt(0) == '[') {     // Explicit IPv6 in []

            int pos = tempKdc.indexOf(']', 1);

            if (pos == -1) {

                throw new IOException("Illegal KDC: " + tempKdc);

            }

            kdc = tempKdc.substring(1, pos);

            if (pos != tempKdc.length() - 1) {  // with port number

                if (tempKdc.charAt(pos+1) != ':') {

                    throw new IOException("Illegal KDC: " + tempKdc);

                }

                portStr = tempKdc.substring(pos+2);

            }

        } else {

            int colon = tempKdc.indexOf(':');

            if (colon == -1) {      // Hostname or IPv4 host only

                kdc = tempKdc;

            } else {

                int nextColon = tempKdc.indexOf(':', colon+1);

                if (nextColon > 0) {    // >=2 ":", IPv6 with no port

                    kdc = tempKdc;

                } else {                // 1 ":", hostname or IPv4 with port

                    kdc = tempKdc.substring(0, colon);

                    portStr = tempKdc.substring(colon+1);

                }

            }

        }

        if (portStr != null) {

            int tempPort = parsePositiveIntString(portStr);

            if (tempPort > 0)

                port = tempPort;

        }

        if (DEBUG) {

            System.out.println(">>> KrbKdcReq send: kdc=" + kdc

                               + (useTCP ? " TCP:":" UDP:")

                               +  port +  ", timeout="

                               + timeout

                               + ", number of retries ="

                               + retries

                               + ", #bytes=" + obuf.length);

        }

        KdcCommunication kdcCommunication =

            new KdcCommunication(kdc, port, useTCP, timeout, retries, obuf);

        try {

            byte[] ibuf = AccessController.doPrivileged(kdcCommunication);

            if (DEBUG) {

                System.out.println(">>> KrbKdcReq send: #bytes read="

                        + (ibuf != null ? ibuf.length : 0));

            }

            return ibuf;

        } catch (PrivilegedActionException e) {

            Exception wrappedException = e.getException();

            if (wrappedException instanceof IOException) {

                throw (IOException) wrappedException;

            } else {

                throw (KrbException) wrappedException;

            }

        }

    }

    private static class KdcCommunication

        implements PrivilegedExceptionAction<byte[]> {

        private String kdc;

        private int port;

        private boolean useTCP;

        private int timeout;

        private int retries;

        private byte[] obuf;

        public KdcCommunication(String kdc, int port, boolean useTCP,

                                int timeout, int retries, byte[] obuf) {

            this.kdc = kdc;

            this.port = port;

            this.useTCP = useTCP;

            this.timeout = timeout;

            this.retries = retries;

            this.obuf = obuf;

        }

        // The caller only casts IOException and KrbException so don't

        // add any new ones!

        public byte[] run() throws IOException, KrbException {

            byte[] ibuf = null;

            for (int i=1; i <= retries; i++) {

                String proto = useTCP?"TCP":"UDP";

                if (DEBUG) {

                    System.out.println(">>> KDCCommunication: kdc=" + kdc

                            + " " + proto + ":"

                            +  port +  ", timeout="

                            + timeout

                            + ",Attempt =" + i

                            + ", #bytes=" + obuf.length);

                }

                try (NetClient kdcClient = NetClient.getInstance(

                        proto, kdc, port, timeout)) {

                    kdcClient.send(obuf);

                    ibuf = kdcClient.receive();

                    break;

                } catch (SocketTimeoutException se) {

                    if (DEBUG) {

                        System.out.println ("SocketTimeOutException with " +

                                "attempt: " + i);

                    }

                    if (i == retries) {

                        ibuf = null;

                        throw se;

                    }

                }

            }

            return ibuf;

        }

    }

    /**

     * Parses a time value string. If it ends with "s", parses as seconds.

     * Otherwise, parses as milliseconds.

     * @param s the time string

     * @return the integer value in milliseconds, or -1 if input is null or

     * has an invalid format

     */

    private static int parseTimeString(String s) {

        if (s == null) {

            return -1;

        }

        if (s.endsWith("s")) {

            int seconds = parsePositiveIntString(s.substring(0, s.length()-1));

            return (seconds < 0) ? -1 : (seconds*1000);

        } else {

            return parsePositiveIntString(s);

        }

    }

    /**

     * Returns krb5.conf setting of {@code key} for a specific realm,

     * which can be:

     * 1. defined in the sub-stanza for the given realm inside [realms], or

     * 2. defined in [libdefaults], or

     * 3. defValue

     * @param realm the given realm in which the setting is requested. Returns

     * the global setting if null

     * @param key the key for the setting

     * @param defValue default value

     * @return a value for the key

     */

    private int getRealmSpecificValue(String realm, String key, int defValue) {

        int v = defValue;

        if (realm == null) return v;

        int temp = -1;

        try {

            String value =

               Config.getInstance().get("realms", realm, key);

            if (key.equals("kdc_timeout")) {

                temp = parseTimeString(value);

            } else {

                temp = parsePositiveIntString(value);

            }

        } catch (Exception exc) {

            // Ignored, defValue will be picked up

        }

        if (temp > 0) v = temp;

        return v;

    }

    private static int parsePositiveIntString(String intString) {

        if (intString == null)

            return -1;

        int ret = -1;

        try {

            ret = Integer.parseInt(intString);

        } catch (Exception exc) {

            return -1;

        }

        if (ret >= 0)

            return ret;

        return -1;

    }

    /**

     * Maintains a KDC accessible list. Unavailable KDCs are put into a

     * blacklist, when a KDC in the blacklist is available, it's removed

     * from there. No insertion order in the blacklist.

     *

     * There are two methods to deal with KDCs in the blacklist. 1. Only try

     * them when there's no KDC not on the blacklist. 2. Still try them, but

     * with lesser number of retries and smaller timeout value.