/*

 * 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.internal.ktab;

import sun.security.krb5.*;

import sun.security.krb5.internal.*;

import sun.security.krb5.internal.crypto.*;

import java.util.ArrayList;

import java.util.Arrays;

import java.io.IOException;

import java.io.FileInputStream;

import java.io.FileOutputStream;

import java.io.File;

import java.util.Comparator;

import java.util.HashMap;

import java.util.Map;

import java.util.StringTokenizer;

import java.util.Vector;

/**

 * This class represents key table. The key table functions deal with storing

 * and retrieving service keys for use in authentication exchanges.

 *

 * @author Yanni Zhang

 */

public class KeyTab implements KeyTabConstants {

    int kt_vno;

    private static KeyTab singleton = null;

    private static final boolean DEBUG = Krb5.DEBUG;

    private static String name;

    private Vector<KeyTabEntry> entries = new Vector<>();

    private KeyTab(String filename) throws IOException, RealmException {

        init(filename);

    }

    public static KeyTab getInstance(String s) {

        name = parse(s);

        if (name == null) {

            return getInstance();

        }

        return getInstance(new File(name));

    }

    /**

     * Gets the single instance of KeyTab class.

     * @param file the key tab file.

     * @return single instance of KeyTab;

     *  return null if error occurs while reading data out of the file.

     */

    public static KeyTab getInstance(File file) {

        try {

            if (!(file.exists())) {

                singleton = null;

            } else {

                String fname = file.getAbsolutePath();

                // Since this class deals with file I/O operations,

                // we want only one class instance existing.

                if (singleton != null) {

                    File kfile = new File(singleton.name);

                    String kname = kfile.getAbsolutePath();

                    if (kname.equalsIgnoreCase(fname)) {

                       if (DEBUG) {

                          System.out.println("KeyTab instance already exists");

                       }

                    }

                } else {

                    singleton = new KeyTab(fname);

                }

            }

        } catch (Exception e) {

            singleton = null;

            if (DEBUG) {

                System.out.println("Could not obtain an instance of KeyTab" +

                                   e.getMessage());

            }

        }

        return singleton;

    }

    /**

     * Gets the single instance of KeyTab class.

     * @return single instance of KeyTab; return null if default keytab file

     *  does not exist, or error occurs while reading data from the file.

     */

    public static KeyTab getInstance() {

        try {

            name = getDefaultKeyTab();

            if (name != null) {

                singleton = getInstance(new File(name));

            }

        } catch (Exception e) {

            singleton = null;

            if (DEBUG) {

                System.out.println("Could not obtain an instance of KeyTab" +

                                   e.getMessage());

            }

        }

        return singleton;

    }

    /**

     * The location of keytab file will be read from the configuration file

     * If it is not specified, consider user.home as the keytab file's

     * default location.

     */

    private static String getDefaultKeyTab() {

        if (name != null) {

            return name;

        } else {

            String kname = null;

            try {

                String keytab_names = Config.getInstance().getDefault

                    ("default_keytab_name", "libdefaults");

                if (keytab_names != null) {

                    StringTokenizer st = new StringTokenizer(keytab_names, " ");

                    while (st.hasMoreTokens()) {

                        kname = parse(st.nextToken());

                        if (kname != null) {

                            break;

                        }

                    }

                }

            } catch (KrbException e) {

                kname = null;

            }

            if (kname == null) {

                String user_home =

                        java.security.AccessController.doPrivileged(

                        new sun.security.action.GetPropertyAction("user.home"));

                if (user_home == null) {

                    user_home =

                        java.security.AccessController.doPrivileged(

                        new sun.security.action.GetPropertyAction("user.dir"));

                }

                if (user_home != null) {

                    kname = user_home + File.separator  + "krb5.keytab";

                }

            }

            return kname;

        }

    }

    private static String parse(String name) {

        String kname = null;

        if (name == null) {

            return null;

        }

        if ((name.length() >= 5) &&

            (name.substring(0, 5).equalsIgnoreCase("FILE:"))) {

            kname = name.substring(5);

        } else if ((name.length() >= 9) &&

                (name.substring(0, 9).equalsIgnoreCase("ANY:FILE:"))) {

            // this format found in MIT's krb5.ini.

            kname = name.substring(9);

        } else if ((name.length() >= 7) &&

                (name.substring(0, 7).equalsIgnoreCase("SRVTAB:"))) {

            // this format found in MIT's krb5.ini.

            kname = name.substring(7);

        } else

            kname = name;

        return kname;

    }

    private synchronized void init(String filename)

        throws IOException, RealmException {

        if (filename != null) {

            KeyTabInputStream kis =

                new KeyTabInputStream(new FileInputStream(filename));

            load(kis);

            kis.close();

            name = filename;

        }

    }

    private void load(KeyTabInputStream kis)

        throws IOException, RealmException {

        entries.clear();

        kt_vno = kis.readVersion();

        if (kt_vno == KRB5_KT_VNO_1) {

            kis.setNativeByteOrder();

        }

        int entryLength = 0;

        KeyTabEntry entry;

        while (kis.available() > 0) {

            entryLength = kis.readEntryLength();

            entry = kis.readEntry(entryLength, kt_vno);

            if (DEBUG) {

                System.out.println(">>> KeyTab: load() entry length: " +

                        entryLength + "; type: " +

                        (entry != null? entry.keyType : 0));

            }

            if (entry != null)

                entries.addElement(entry);

        }

    }

    /**

     * Reads all keys for a service from the keytab file that have

     * etypes that have been configured for use. If there are multiple

     * keys with same etype, the one with the highest kvno is returned.

     * @param service the PrincipalName of the requested service

     * @return an array containing all the service keys

     */

    public EncryptionKey[] readServiceKeys(PrincipalName service) {

        KeyTabEntry entry;

        EncryptionKey key;

        int size = entries.size();

        ArrayList<EncryptionKey> keys = new ArrayList<>(size);

        for (int i = size-1; i >= 0; i--) {

            entry = entries.elementAt(i);

            if (entry.service.match(service)) {

                if (EType.isSupported(entry.keyType)) {

                    key = new EncryptionKey(entry.keyblock,

                                        entry.keyType,

                                        new Integer(entry.keyVersion));

                    keys.add(key);

                    if (DEBUG) {

                        System.out.println("Added key: " + entry.keyType +

                            "version: " + entry.keyVersion);

                    }

                } else if (DEBUG) {

                    System.out.println("Found unsupported keytype (" +

                        entry.keyType + ") for " + service);

                }

            }

        }

        size = keys.size();

        if (size == 0)

            return null;

        EncryptionKey[] retVal = keys.toArray(new EncryptionKey[size]);

        // Sort keys according to default_tkt_enctypes

        if (DEBUG) {

            System.out.println("Ordering keys wrt default_tkt_enctypes list");

        }

        final int[] etypes = EType.getDefaults("default_tkt_enctypes");

        // Sort the keys, k1 is preferred than k2 if:

        // 1. k1's etype appears earlier in etypes than k2's

        // 2. If same, k1's KVNO is higher

        Arrays.sort(retVal, new Comparator<EncryptionKey>() {

            @Override

            public int compare(EncryptionKey o1, EncryptionKey o2) {

                if (etypes != null) {

                    int o1EType = o1.getEType();

                    int o2EType = o2.getEType();

                    if (o1EType != o2EType) {

                        for (int i=0; i<etypes.length; i++) {

                            if (etypes[i] == o1EType) {

                                return -1;

                            } else if (etypes[i] == o2EType) {

                                return 1;

                            }

                        }

                        // Neither o1EType nor o2EType in default_tkt_enctypes,

                        // therefore won't be used in AS-REQ. We do not care

                        // about their order, use kvno is OK.

                    }

                }

                return o2.getKeyVersionNumber().intValue()

                        - o1.getKeyVersionNumber().intValue();

            }

        });

        return retVal;

    }

    /**

     * Searches for the service entry in the keytab file.

     * The etype of the key must be one that has been configured

     * to be used.

     * @param service the PrincipalName of the requested service.

     * @return true if the entry is found, otherwise, return false.

     */

    public boolean findServiceEntry(PrincipalName service) {

        KeyTabEntry entry;

        for (int i = 0; i < entries.size(); i++) {

            entry = entries.elementAt(i);

            if (entry.service.match(service)) {

                if (EType.isSupported(entry.keyType)) {

                    return true;

                } else if (DEBUG) {

                    System.out.println("Found unsupported keytype (" +

                        entry.keyType + ") for " + service);

                }

            }

        }

        return false;

    }

    public static String tabName() {

        return name;

    }

    /**

     * Adds a new entry in the key table.

     * @param service the service which will have a new entry in the key table.

     * @param psswd the password which generates the key.

     * @param kvno the kvno to use, -1 means automatic increasing

     * @param append false if entries with old kvno would be removed.

     * Note: if kvno is not -1, entries with the same kvno are always removed

     */

    public void addEntry(PrincipalName service, char[] psswd,

            int kvno, boolean append) throws KrbException {

        EncryptionKey[] encKeys = EncryptionKey.acquireSecretKeys(

            psswd, service.getSalt());

        // There should be only one maximum KVNO value for all etypes, so that

        // all added keys can have the same KVNO.

        int maxKvno = 0;    // only useful when kvno == -1

        for (int i = entries.size()-1; i >= 0; i--) {

            KeyTabEntry e = entries.get(i);

            if (e.service.match(service)) {

                if (e.keyVersion > maxKvno) {

                    maxKvno = e.keyVersion;

                }

                if (!append || e.keyVersion == kvno) {

                    entries.removeElementAt(i);

                }

            }

        }

        if (kvno == -1) {

            kvno = maxKvno + 1;

        }

        for (int i = 0; encKeys != null && i < encKeys.length; i++) {

            int keyType = encKeys[i].getEType();

            byte[] keyValue = encKeys[i].getBytes();

            KeyTabEntry newEntry = new KeyTabEntry(service,

                            service.getRealm(),

                            new KerberosTime(System.currentTimeMillis()),

                                               kvno, keyType, keyValue);

            entries.addElement(newEntry);

        }

    }

    /**

     * Gets the list of service entries in key table.

     * @return array of <code>KeyTabEntry</code>.

     */

    public KeyTabEntry[] getEntries() {

        KeyTabEntry[] kentries = new KeyTabEntry[entries.size()];

        for (int i = 0; i < kentries.length; i++) {

            kentries[i] = entries.elementAt(i);

        }

        return kentries;

    }

    /**

     * Creates a new default key table.

     */

    public synchronized static KeyTab create()

        throws IOException, RealmException {

        String dname = getDefaultKeyTab();

        return create(dname);

    }

    /**

     * Creates a new default key table.

     */

    public synchronized static KeyTab create(String name)

        throws IOException, RealmException {

        KeyTabOutputStream kos =

                new KeyTabOutputStream(new FileOutputStream(name));

        kos.writeVersion(KRB5_KT_VNO);

        kos.close();

        singleton = new KeyTab(name);

        return singleton;

    }

    /**

     * Saves the file at the directory.

     */

    public synchronized void save() throws IOException {

        KeyTabOutputStream kos =

                new KeyTabOutputStream(new FileOutputStream(name));

        kos.writeVersion(kt_vno);

        for (int i = 0; i < entries.size(); i++) {

            kos.writeEntry(entries.elementAt(i));

        }

        kos.close();

    }

    /**

     * Removes entries from the key table.

     * @param service the service <code>PrincipalName</code>.

     * @param etype the etype to match, remove all if -1

     * @param kvno what kvno to remove, -1 for all, -2 for old

     * @return the number of entries deleted

     */

    public int deleteEntries(PrincipalName service, int etype, int kvno) {

        int count = 0;

        // Remember the highest KVNO for each etype. Used for kvno == -2

        Map<Integer,Integer> highest = new HashMap<>();

        for (int i = entries.size()-1; i >= 0; i--) {

            KeyTabEntry e = entries.get(i);

            if (service.match(e.getService())) {

                if (etype == -1 || e.keyType == etype) {

                    if (kvno == -2) {

                        // Two rounds for kvno == -2. In the first round (here),

                        // only find out highest KVNO for each etype

                        if (highest.containsKey(e.keyType)) {

                            int n = highest.get(e.keyType);

                            if (e.keyVersion > n) {

                                highest.put(e.keyType, e.keyVersion);

                            }

                        } else {

                            highest.put(e.keyType, e.keyVersion);

                        }

                    } else if (kvno == -1 || e.keyVersion == kvno) {

                        entries.removeElementAt(i);

                        count++;

                    }

                }

            }

        }

        // Second round for kvno == -2, remove old entries

        if (kvno == -2) {

            for (int i = entries.size()-1; i >= 0; i--) {

                KeyTabEntry e = entries.get(i);

                if (service.match(e.getService())) {

                    if (etype == -1 || e.keyType == etype) {

                        int n = highest.get(e.keyType);

                        if (e.keyVersion != n) {

                            entries.removeElementAt(i);

                            count++;

                        }

                    }

                }

            }

        }

        return count;

    }

    /**

     * Creates key table file version.

     * @param file the key table file.

     * @exception IOException.

     */

    public synchronized void createVersion(File file) throws IOException {

        KeyTabOutputStream kos =

                new KeyTabOutputStream(new FileOutputStream(file));

        kos.write16(KRB5_KT_VNO);

        kos.close();

    }

    public static void refresh() {

        if (singleton != null) {

            if (DEBUG) {

                System.out.println("Refreshing Keytab");

            }

            singleton = null;

        }

    }

}