/*
 * Copyright (c) 2000, 2021, 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
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/*
 *
 *  (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.
/**
 * 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)
/**
     * 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
/**
     * timeout requesting a ticket from KDC, in millisec, default 30 sec
     */
    private static int defaultKdcTimeout;
    
max UDP packet size, default unlimited (-1)
/**
     * 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.
/**
     * 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
/**
     * 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
/**
     * 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.
Params:
s – the time string
Returns:
the integer value in milliseconds, or -1 if input is null or
has an invalid format/**
     * 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 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 
Params:
realm – the given realm in which the setting is requested. Returns
the global setting if null
key – the key for the setting
defValue – default value
Returns:
a value for the key/**
     * 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
secondary KDC list. When a KDC in the secondary list is available,
it is removed from there. No insertion order in the secondary KDC list.
There are two methods to deal with KDCs in the secondary KDC list.
1. Only try them when they are the only known KDCs.
2. Still try them, but with fewer retries and a smaller timeout value.
/**
     * Maintains a KDC accessible list. Unavailable KDCs are put into a
     * secondary KDC list. When a KDC in the secondary list is available,
     * it is removed from there. No insertion order in the secondary KDC list.
     *
     * There are two methods to deal with KDCs in the secondary KDC list.
     * 1. Only try them when they are the only known KDCs.
     * 2. Still try them, but with fewer retries and a smaller timeout value.
     */
    static class KdcAccessibility {
        // Known bad KDCs
        private static Set<String> bads = new HashSet<>();

        private static synchronized void addBad(String kdc) {
            if (DEBUG) {
                System.out.println(">>> KdcAccessibility: add " + kdc);
            }
            bads.add(kdc);
        }

        private static synchronized void removeBad(String kdc) {
            if (DEBUG) {
                System.out.println(">>> KdcAccessibility: remove " + kdc);
            }
            bads.remove(kdc);
        }

        private static synchronized boolean isBad(String kdc) {
            return bads.contains(kdc);
        }

        private static synchronized void reset() {
            if (DEBUG) {
                System.out.println(">>> KdcAccessibility: reset");
            }
            bads.clear();
        }

        // Returns a preferred KDC list by putting the bad ones at the end
        private static synchronized List<String> list(String kdcList) {
            StringTokenizer st = new StringTokenizer(kdcList);
            List<String> list = new ArrayList<>();
            if (badPolicy == BpType.TRY_LAST) {
                List<String> badkdcs = new ArrayList<>();
                while (st.hasMoreTokens()) {
                    String t = st.nextToken();
                    if (bads.contains(t)) badkdcs.add(t);
                    else list.add(t);
                }
                // Bad KDCs are put at last
                list.addAll(badkdcs);
            } else {
                // All KDCs are returned in their original order,
                // This include TRY_LESS and NONE
                while (st.hasMoreTokens()) {
                    list.add(st.nextToken());
                }
            }
            return list;
        }
    }
}