security/krb5/Config.java

/*
 * Copyright (c) 2000, 2012, 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.io.File;
import java.io.FileInputStream;
import java.util.Hashtable;
import java.util.Vector;
import java.util.ArrayList;
import java.io.BufferedReader;
import java.io.InputStreamReader;
import java.io.IOException;
import java.util.Enumeration;
import java.util.StringTokenizer;
import java.net.InetAddress;
import java.net.UnknownHostException;
import java.util.List;
import sun.net.dns.ResolverConfiguration;
import sun.security.krb5.internal.crypto.EType;
import sun.security.krb5.internal.ktab.*;
import sun.security.krb5.internal.Krb5;

/**
 * This class maintains key-value pairs of Kerberos configurable constants
 * from configuration file or from user specified system properties.
 */

public class Config {

    /*
     * Only allow a single instance of Config.
     */
    private static Config singleton = null;

    /*
     * Hashtable used to store configuration infomation.
     */
    private Hashtable<String,Object> stanzaTable;

    private static boolean DEBUG = sun.security.krb5.internal.Krb5.DEBUG;

    // these are used for hexdecimal calculation.
    private static final int BASE16_0 = 1;
    private static final int BASE16_1 = 16;
    private static final int BASE16_2 = 16 * 16;
    private static final int BASE16_3 = 16 * 16 * 16;

    /**
     * Specified by system properties. Must be both null or non-null.
     */
    private final String defaultRealm;
    private final String defaultKDC;

    // used for native interface
    private static native String getWindowsDirectory(boolean isSystem);


    /**
     * Gets an instance of Config class. One and only one instance (the
     * singleton) is returned.
     *
     * @exception KrbException if error occurs when constructing a Config
     * instance. Possible causes would be either of java.security.krb5.realm or
     * java.security.krb5.kdc not specified, error reading configuration file.
     */
    public static synchronized Config getInstance() throws KrbException {
        if (singleton == null) {
            singleton = new Config();
        }
        return singleton;
    }

    /**
     * Refresh and reload the Configuration. This could involve,
     * for example reading the Configuration file again or getting
     * the java.security.krb5.* system properties again.
     *
     * @exception KrbException if error occurs when constructing a Config
     * instance. Possible causes would be either of java.security.krb5.realm or
     * java.security.krb5.kdc not specified, error reading configuration file.
     */

    public static synchronized void refresh() throws KrbException {
        singleton = new Config();
        KdcComm.initStatic();
    }


    private static boolean isMacosLionOrBetter() {
        // split the "10.x.y" version number
        String osname = getProperty("os.name");
        if (!osname.contains("OS X")) {
            return false;
        }

        String osVersion = getProperty("os.version");
        String[] fragments = osVersion.split("\\.");

        // sanity check the "10." part of the version
        if (!fragments[0].equals("10")) return false;
        if (fragments.length < 2) return false;

        // check if Mac OS X 10.7(.y)
        try {
            int minorVers = Integer.parseInt(fragments[1]);
            if (minorVers >= 7) return true;
        } catch (NumberFormatException e) {
            // was not an integer
        }

        return false;
    }

    /**
     * Private constructor - can not be instantiated externally.
     */
    private Config() throws KrbException {
        /*
         * If either one system property is specified, we throw exception.
         */
        String tmp = getProperty("java.security.krb5.kdc");
        if (tmp != null) {
            // The user can specify a list of kdc hosts separated by ":"
            defaultKDC = tmp.replace(':', ' ');
        } else {
            defaultKDC = null;
        }
        defaultRealm = getProperty("java.security.krb5.realm");
        if ((defaultKDC == null && defaultRealm != null) ||
            (defaultRealm == null && defaultKDC != null)) {
            throw new KrbException
                ("System property java.security.krb5.kdc and " +
                 "java.security.krb5.realm both must be set or " +
                 "neither must be set.");
        }

        // Always read the Kerberos configuration file
        try {
            Vector<String> configFile;
            String fileName = getJavaFileName();
            if (fileName != null) {
                configFile = loadConfigFile(fileName);
                stanzaTable = parseStanzaTable(configFile);
                if (DEBUG) {
                    System.out.println("Loaded from Java config");
                }
            } else {
                boolean found = false;
                if (isMacosLionOrBetter()) {
                    try {
                        stanzaTable = SCDynamicStoreConfig.getConfig();
                        if (DEBUG) {
                            System.out.println("Loaded from SCDynamicStoreConfig");
                        }
                        found = true;
                    } catch (IOException ioe) {
                        // OK. Will go on with file
                    }
                }
                if (!found) {
                    fileName = getNativeFileName();
                    configFile = loadConfigFile(fileName);
                    stanzaTable = parseStanzaTable(configFile);
                    if (DEBUG) {
                        System.out.println("Loaded from native config");
                    }
                }
            }
        } catch (IOException ioe) {
            // No krb5.conf, no problem. We'll use DNS or system property etc.
        }
    }

    /**
     * Gets the default int value for the specified name.
     * @param name the name.
     * @return the default Integer, null is returned if no such name and
     * value are found in configuration file, or error occurs when parsing
     * string to integer.
     */
    public int getDefaultIntValue(String name) {
        String result = null;
        int value = Integer.MIN_VALUE;
        result = getDefault(name);
        if (result != null) {
            try {
                value = parseIntValue(result);
            } catch (NumberFormatException e) {
                if (DEBUG) {
                    System.out.println("Exception in getting value of " +
                                       name + " " +
                                       e.getMessage());
                    System.out.println("Setting " + name +
                                       " to minimum value");
                }
                value = Integer.MIN_VALUE;
            }
        }
        return value;
    }

    /**
     * Gets the default int value for the specified name in the specified
     * section. <br>This method is quicker by using section name as the
     * search key.
     * @param name the name.
     * @param sectio the name string of the section.
     * @return the default Integer, null is returned if no such name and
     * value are found in configuration file, or error occurs when parsing
     * string to integer.
     */
    public int getDefaultIntValue(String name, String section) {
        String result = null;
        int value = Integer.MIN_VALUE;
        result = getDefault(name, section);
        if (result != null) {
            try {
                value = parseIntValue(result);
            } catch (NumberFormatException e) {
                if (DEBUG) {
                    System.out.println("Exception in getting value of " +
                                       name +" in section " +
                                       section + " "  + e.getMessage());
                    System.out.println("Setting " + name +
                                       " to minimum value");
                }
                value = Integer.MIN_VALUE;
            }
        }
        return value;
    }

    /**
     * Gets the default string value for the specified name.
     * @param name the name.
     * @return the default value, null is returned if it cannot be found.
     */
    public String getDefault(String name) {
        if (stanzaTable == null) {
            return null;
        } else {
            return getDefault(name, stanzaTable);
        }
    }

    /**
     * This method does the real job to recursively search through the
     * stanzaTable.
     * @param k the key string.
     * @param t stanzaTable or sub hashtable within it.
     * @return the value found in config file, returns null if no value
     * matched with the key is found.
     */
    private String getDefault(String k, Hashtable t) {
        String result = null;
        String key;
        if (stanzaTable != null) {
            for (Enumeration e = t.keys(); e.hasMoreElements(); ) {
                key = (String)e.nextElement();
                Object ob = t.get(key);
                if (ob instanceof Hashtable) {
                    result = getDefault(k, (Hashtable)ob);
                    if (result != null) {
                        return result;
                    }
                } else if (key.equalsIgnoreCase(k)) {
                    if (ob instanceof String) {
                        return (String)(t.get(key));
                    } else if (ob instanceof Vector) {
                        result = "";
                        int length = ((Vector)ob).size();
                        for (int i = 0; i < length; i++) {
                            if (i == length -1) {
                                result +=
                                    (String)(((Vector)ob).elementAt(i));
                            } else {
                                result +=
                                    (String)(((Vector)ob).elementAt(i)) + " ";
                            }
                        }
                        return result;
                    }
                }
            }
        }
        return result;
    }

    /**
     * Gets the default string value for the specified name in the
     * specified section.
     * <br>This method is quicker by using the section name as the search key.
     * @param name the name.
     * @param section the name of the section.
     * @return the default value, null is returned if it cannot be found.
     */
    public String getDefault(String name, String section) {
        String stanzaName;
        String result = null;
        Hashtable subTable;

        if (stanzaTable != null) {
            for (Enumeration e = stanzaTable.keys(); e.hasMoreElements(); ) {
                stanzaName = (String)e.nextElement();
                subTable = (Hashtable)stanzaTable.get(stanzaName);
                if (stanzaName.equalsIgnoreCase(section)) {
                    if (subTable.containsKey(name)) {
                        return (String)(subTable.get(name));
                    }
                } else if (subTable.containsKey(section)) {
                    Object ob = subTable.get(section);
                    if (ob instanceof Hashtable) {
                        Hashtable temp = (Hashtable)ob;
                        if (temp.containsKey(name)) {
                            Object object = temp.get(name);
                            if (object instanceof Vector) {
                                result = "";
                                int length = ((Vector)object).size();
                                for (int i = 0; i < length; i++) {
                                    if (i == length - 1)  {
                                        result +=
                                        (String)(((Vector)object).elementAt(i));
                                    } else {
                                        result +=
                                        (String)(((Vector)object).elementAt(i))
                                                + " ";
                                    }
                                }
                            } else {
                                result = (String)object;
                            }
                        }
                    }
                }
            }
        }
        return result;
    }

    /**
     * Gets the default boolean value for the specified name.
     * @param name the name.
     * @return the default boolean value, false is returned if it cannot be
     * found.
     */
    public boolean getDefaultBooleanValue(String name) {
        String val = null;
        if (stanzaTable == null) {
            val = null;
        } else {
            val = getDefault(name, stanzaTable);
        }
        if (val != null && val.equalsIgnoreCase("true")) {
            return true;
        } else {
            return false;
        }
    }

    /**
     * Gets the default boolean value for the specified name in the
     * specified section.
     * <br>This method is quicker by using the section name as the search key.
     * @param name the name.
     * @param section the name of the section.
     * @return the default boolean value, false is returned if it cannot be
     * found.
     */
    public boolean getDefaultBooleanValue(String name, String section) {
        String val = getDefault(name, section);
        if (val != null && val.equalsIgnoreCase("true")) {
            return true;
        } else {
            return false;
        }
    }

    /**
     * Parses a string to an integer. The convertible strings include the
     * string representations of positive integers, negative integers, and
     * hex decimal integers.  Valid inputs are, e.g., -1234, +1234,
     * 0x40000.
     *
     * @param input the String to be converted to an Integer.
     * @return an numeric value represented by the string
     * @exception NumberFormationException if the String does not contain a
     * parsable integer.
     */
    private int parseIntValue(String input) throws NumberFormatException {
        int value = 0;
        if (input.startsWith("+")) {
            String temp = input.substring(1);
            return Integer.parseInt(temp);
        } else if (input.startsWith("0x")) {
            String temp = input.substring(2);
            char[] chars = temp.toCharArray();
            if (chars.length > 8) {
                throw new NumberFormatException();
            } else {
                for (int i = 0; i < chars.length; i++) {
                    int index = chars.length - i - 1;
                    switch (chars[i]) {
                    case '0':
                        value += 0;
                        break;
                    case '1':
                        value += 1 * getBase(index);
                        break;
                    case '2':
                        value += 2 * getBase(index);
                        break;
                    case '3':
                        value += 3 * getBase(index);
                        break;
                    case '4':
                        value += 4 * getBase(index);
                        break;
                    case '5':
                        value += 5 * getBase(index);
                        break;
                    case '6':
                        value += 6 * getBase(index);
                        break;
                    case '7':
                        value += 7 * getBase(index);
                        break;
                    case '8':
                        value += 8 * getBase(index);
                        break;
                    case '9':
                        value += 9 * getBase(index);
                        break;
                    case 'a':
                    case 'A':
                        value += 10 * getBase(index);
                        break;
                    case 'b':
                    case 'B':
                        value += 11 * getBase(index);
                        break;
                    case 'c':
                    case 'C':
                        value += 12 * getBase(index);
                        break;
                    case 'd':
                    case 'D':
                        value += 13 * getBase(index);
                        break;
                    case 'e':
                    case 'E':
                        value += 14 * getBase(index);
                        break;
                    case 'f':
                    case 'F':
                        value += 15 * getBase(index);
                        break;
                    default:
                        throw new NumberFormatException("Invalid numerical format");
                    }
                }
            }
            if (value < 0) {
                throw new NumberFormatException("Data overflow.");
            }
        } else {
            value = Integer.parseInt(input);
        }
        return value;
    }

    private int getBase(int i) {
        int result = 16;
        switch (i) {
        case 0:
            result = BASE16_0;
            break;
        case 1:
            result = BASE16_1;
            break;
        case 2:
            result = BASE16_2;
            break;
        case 3:
            result = BASE16_3;
            break;
        default:
            for (int j = 1; j < i; j++) {
                result *= 16;
            }
        }
        return result;
    }

    /**
     * Finds the matching value in the hashtable.
     */
    private String find(String key1, String key2) {
        String result;
        if ((stanzaTable != null) &&
            ((result = (String)
                (((Hashtable)(stanzaTable.get(key1))).get(key2))) != null)) {
            return result;
        } else {
            return "";
        }
    }

    /**
     * Reads name/value pairs to the memory from the configuration
     * file. The default location of the configuration file is in java home
     * directory.
     *
     * Configuration file contains information about the default realm,
     * ticket parameters, location of the KDC and the admin server for
     * known realms, etc. The file is divided into sections. Each section
     * contains one or more name/value pairs with one pair per line. A
     * typical file would be:
     * [libdefaults]
     *          default_realm = EXAMPLE.COM
     *          default_tgs_enctypes = des-cbc-md5
     *          default_tkt_enctypes = des-cbc-md5
     * [realms]
     *          EXAMPLE.COM = {
     *                  kdc = kerberos.example.com
     *                  kdc = kerberos-1.example.com
     *                  admin_server = kerberos.example.com
     *                  }
     *          SAMPLE_COM = {
     *                  kdc = orange.sample.com
     *                  admin_server = orange.sample.com
     *                  }
     * [domain_realm]
     *          blue.sample.com = TEST.SAMPLE.COM
     *          .backup.com     = EXAMPLE.COM
     *
     * @params fileName the conf file, cannot be null
     * @return the content, null if fileName is empty
     * @throws IOException if there is an I/O or format error
     */
    private Vector<String> loadConfigFile(final String fileName) throws IOException {
        try {
            if (!fileName.equals("")) {
                BufferedReader br = new BufferedReader(new InputStreamReader(
                java.security.AccessController.doPrivileged(
                new java.security.PrivilegedExceptionAction<FileInputStream> () {
                public FileInputStream run() throws IOException {
                    return new FileInputStream(fileName);
                }
                })));
                String Line;
                Vector<String> v = new Vector<>();
                String previous = null;
                while ((Line = br.readLine()) != null) {
                    // ignore comments and blank line in the configuration file.
                    // Comments start with #.
                    if (!(Line.startsWith("#") || Line.trim().isEmpty())) {
                        String current = Line.trim();
                        // In practice, a subsection might look like:
                        //      EXAMPLE.COM =
                        //      {
                        //              kdc = kerberos.example.com
                        //              ...
                        //      }
                        // Before parsed into stanza table, it needs to be
                        // converted into formal style:
                        //      EXAMPLE.COM = {
                        //              kdc = kerberos.example.com
                        //              ...
                        //      }
                        //
                        // So, if a line is "{", adhere to the previous line.
                        if (current.equals("{")) {
                            if (previous == null) {
                                throw new IOException(
                                    "Config file should not start with \"{\"");
                            }
                            previous += " " + current;
                        } else {
                            if (previous != null) {
                                v.addElement(previous);
                            }
                            previous = current;
                        }
                    }
                }
                if (previous != null) {
                    v.addElement(previous);
                }

                br.close();
                return v;
            }
            return null;
        } catch (java.security.PrivilegedActionException pe) {
            throw (IOException)pe.getException();
        }
    }


    /**
     * Parses stanza names and values from configuration file to
     * stanzaTable (Hashtable). Hashtable key would be stanza names,
     * (libdefaults, realms, domain_realms, etc), and the hashtable value
     * would be another hashtable which contains the key-value pairs under
     * a stanza name.
     */
    private Hashtable<String,Object> parseStanzaTable(Vector<String> v) throws KrbException {
        if (v == null) {
            throw new KrbException("I/O error while reading" +
                        " configuration file.");
        }
        Hashtable<String,Object> table = new Hashtable<>();
        for (int i = 0; i < v.size(); i++) {
            String line = v.elementAt(i).trim();
            if (line.equalsIgnoreCase("[realms]")) {
                for (int count = i + 1; count < v.size() + 1; count++) {
                    // find the next stanza name
                    if ((count == v.size()) ||
                        (v.elementAt(count).startsWith("["))) {
                        Hashtable<String,Hashtable<String,Vector<String>>> temp =
                            new Hashtable<>();
                        temp = parseRealmField(v, i + 1, count);
                        table.put("realms", temp);
                        i = count - 1;
                        break;
                    }
                }
            } else if (line.equalsIgnoreCase("[capaths]")) {
                for (int count = i + 1; count < v.size() + 1; count++) {
                    // find the next stanza name
                    if ((count == v.size()) ||
                        (v.elementAt(count).startsWith("["))) {
                        Hashtable<String,Hashtable<String,Vector<String>>> temp =
                            new Hashtable<>();
                        temp = parseRealmField(v, i + 1, count);
                        table.put("capaths", temp);
                        i = count - 1;
                        break;
                    }
                }
            } else if (line.startsWith("[") && line.endsWith("]")) {
                String key = line.substring(1, line.length() - 1);
                for (int count = i + 1; count < v.size() + 1; count++) {
                    // find the next stanza name
                    if ((count == v.size()) ||
                        (v.elementAt(count).startsWith("["))) {
                        Hashtable<String,String> temp =
                            parseField(v, i + 1, count);
                        table.put(key, temp);
                        i = count - 1;
                        break;
                    }
                }
            }
        }
        return table;
    }

    /**
     * Gets the default Java configuration file name.
     *
     * If the system property "java.security.krb5.conf" is defined, we'll
     * use its value, no matter if the file exists or not. Otherwise, we
     * will look at $JAVA_HOME/lib/security directory with "krb5.conf" name,
     * and return it if the file exists.
     *
     * The method returns null if it cannot find a Java config file.
     */
    private String getJavaFileName() {
        String name = getProperty("java.security.krb5.conf");
        if (name == null) {
            name = getProperty("java.home") + File.separator +
                                "lib" + File.separator + "security" +
                                File.separator + "krb5.conf";
            if (!fileExists(name)) {
                name = null;
            }
        }
        if (DEBUG) {
            System.out.println("Java config name: " + name);
        }
        return name;
    }

    /**
     * Gets the default native configuration file name.
     *
     * Depending on the OS type, the method returns the default native
     * kerberos config file name, which is at windows directory with
     * the name of "krb5.ini" for Windows, /etc/krb5/krb5.conf for Solaris,
     * /etc/krb5.conf otherwise. Mac OSX X has a different file name.
     *
     * Note: When the Terminal Service is started in Windows (from 2003),
     * there are two kinds of Windows directories: A system one (say,
     * C:\Windows), and a user-private one (say, C:\Users\Me\Windows).
     * We will first look for krb5.ini in the user-private one. If not
     * found, try the system one instead.
     *
     * This method will always return a non-null non-empty file name,
     * even if that file does not exist.
     */
    private String getNativeFileName() {
        String name = null;
        String osname = getProperty("os.name");
        if (osname.startsWith("Windows")) {
            try {
                Credentials.ensureLoaded();
            } catch (Exception e) {
                // ignore exceptions
            }
            if (Credentials.alreadyLoaded) {
                String path = getWindowsDirectory(false);
                if (path != null) {
                    if (path.endsWith("\\")) {
                        path = path + "krb5.ini";
                    } else {
                        path = path + "\\krb5.ini";
                    }
                    if (fileExists(path)) {
                        name = path;
                    }
                }
                if (name == null) {
                    path = getWindowsDirectory(true);
                    if (path != null) {
                        if (path.endsWith("\\")) {
                            path = path + "krb5.ini";
                        } else {
                            path = path + "\\krb5.ini";
                        }
                        name = path;
                    }
                }
            }
            if (name == null) {
                name = "c:\\winnt\\krb5.ini";
            }
        } else if (osname.startsWith("SunOS")) {
            name =  "/etc/krb5/krb5.conf";
        } else if (osname.contains("OS X")) {
            name = findMacosConfigFile();
        } else {
            name =  "/etc/krb5.conf";
        }
        if (DEBUG) {
            System.out.println("Native config name: " + name);
        }
        return name;
    }

    private static String getProperty(String property) {
        return java.security.AccessController.doPrivileged(
                new sun.security.action.GetPropertyAction(property));
    }

    private String findMacosConfigFile() {
        String userHome = getProperty("user.home");
        final String PREF_FILE = "/Library/Preferences/edu.mit.Kerberos";
        String userPrefs = userHome + PREF_FILE;

        if (fileExists(userPrefs)) {
            return userPrefs;
        }

        if (fileExists(PREF_FILE)) {
            return PREF_FILE;
        }

        return "/etc/krb5.conf";
    }

    private static String trimmed(String s) {
        s = s.trim();
        if (s.charAt(0) == '"' && s.charAt(s.length()-1) == '"' ||
                s.charAt(0) == '\'' && s.charAt(s.length()-1) == '\'') {
            s = s.substring(1, s.length()-1).trim();
        }
        return s;
    }
    /**
     * Parses key-value pairs under a stanza name.
     */
    private Hashtable<String,String>  parseField(Vector<String> v, int start, int end) {
        Hashtable<String,String> table = new Hashtable<>();
        String line;
        for (int i = start; i < end; i++) {
            line = v.elementAt(i);
            for (int j = 0; j < line.length(); j++) {
                if (line.charAt(j) == '=') {
                    String key = (line.substring(0, j)).trim();
                    String value = trimmed(line.substring(j + 1));
                    table.put(key, value);
                    break;
                }
            }
        }
        return table;
    }

    /**
     * Parses key-value pairs under [realms].  The key would be the realm
     * name, the value would be another hashtable which contains
     * information for the realm given within a pair of braces.
     */
    private Hashtable<String,Hashtable<String,Vector<String>>> parseRealmField(Vector<String> v, int start, int end) {
        Hashtable<String,Hashtable<String,Vector<String>>> table = new Hashtable<>();
        String line;
        for (int i = start; i < end; i++) {
            line = v.elementAt(i).trim();
            if (line.endsWith("{")) {
                String key = "";
                for (int j = 0; j < line.length(); j++) {
                    if (line.charAt(j) == '=') {
                        key = line.substring(0, j).trim();
                        // get the key
                        break;
                    }
                }
                for (int k = i + 1; k < end; k++) {
                    boolean found = false;
                    line = v.elementAt(k).trim();
                    for (int l = 0; l < line.length(); l++) {
                        if (line.charAt(l) == '}') {
                            found = true;
                            break;
                        }
                    }
                    if (found == true) {
                        Hashtable<String,Vector<String>> temp = parseRealmFieldEx(v, i + 1, k);
                        table.put(key, temp);
                        i = k;
                        found = false;
                        break;
                    }

                }
            }
        }
        return table;
    }

    /**
     * Parses key-value pairs within each braces under [realms].
     */
    private Hashtable<String,Vector<String>> parseRealmFieldEx(Vector<String> v, int start, int end) {
        Hashtable<String,Vector<String>> table = new Hashtable<>();
        Vector<String> keyVector = new Vector<>();
        Vector<String> nameVector = new Vector<>();
        String line = "";
        String key;
        for (int i = start; i < end; i++) {
            line = v.elementAt(i);
            for (int j = 0; j < line.length(); j++) {
                if (line.charAt(j) == '=') {
                    int index;
                    key = line.substring(0, j).trim();
                    if (! exists(key, keyVector)) {
                        keyVector.addElement(key);
                        nameVector = new Vector<String> ();
                    } else {
                        nameVector = table.get(key);
                    }
                    nameVector.addElement(trimmed(line.substring(j + 1)));
                    table.put(key, nameVector);
                    break;
                }
            }
        }
        return table;
    }

    /**
     * Compares the key with the known keys to see if it exists.
     */
    private boolean exists(String key, Vector v) {
        boolean exists = false;
        for (int i = 0; i < v.size(); i++) {
            if (((String)(v.elementAt(i))).equals(key)) {
                exists = true;
            }
        }
        return exists;
    }

    /**
     * For testing purpose. This method lists all information being parsed from
     * the configuration file to the hashtable.
     */
    public void listTable() {
        listTable(stanzaTable);
    }

    private void listTable(Hashtable table) {
        Vector v = new Vector();
        String key;
        if (stanzaTable != null) {
            for (Enumeration e = table.keys(); e.hasMoreElements(); ) {
                key = (String)e.nextElement();
                Object object = table.get(key);
                if (table == stanzaTable) {
                    System.out.println("[" + key + "]");
                }
                if (object instanceof Hashtable) {
                    if (table != stanzaTable)
                        System.out.println("\t" + key + " = {");
                    listTable((Hashtable)object);
                    if (table != stanzaTable)
                        System.out.println("\t}");

                } else if (object instanceof String) {
                    System.out.println("\t" + key + " = " +
                                (String)table.get(key));
                } else if (object instanceof Vector) {
                    v = (Vector)object;
                    for (int i = 0; i < v.size(); i++) {
                        System.out.println("\t" + key + " = " +
                                (String)v.elementAt(i));
                    }
                }
            }
        } else {
            System.out.println("Configuration file not found.");
        }
    }

    /**
     * Returns the default encryption types.
     *
     */
    public int[] defaultEtype(String enctypes) {
        String default_enctypes;
        default_enctypes = getDefault(enctypes, "libdefaults");
        String delim = " ";
        StringTokenizer st;
        int[] etype;
        if (default_enctypes == null) {
            if (DEBUG) {
                System.out.println("Using builtin default etypes for " +
                    enctypes);
            }
            etype = EType.getBuiltInDefaults();
        } else {
            for (int j = 0; j < default_enctypes.length(); j++) {
                if (default_enctypes.substring(j, j + 1).equals(",")) {
                    // only two delimiters are allowed to use
                    // according to Kerberos DCE doc.
                    delim = ",";
                    break;
                }
            }
            st = new StringTokenizer(default_enctypes, delim);
            int len = st.countTokens();
            ArrayList<Integer> ls = new ArrayList<>(len);
            int type;
            for (int i = 0; i < len; i++) {
                type = getType(st.nextToken());
                if ((type != -1) &&
                    (EType.isSupported(type))) {
                    ls.add(type);
                }
            }
            if (ls.size() == 0) {
                if (DEBUG) {
                    System.out.println(
                        "no supported default etypes for " + enctypes);
                }
                return null;
            } else {
                etype = new int[ls.size()];
                for (int i = 0; i < etype.length; i++) {
                    etype[i] = ls.get(i);
                }
            }
        }

        if (DEBUG) {
            System.out.print("default etypes for " + enctypes + ":");
            for (int i = 0; i < etype.length; i++) {
                System.out.print(" " + etype[i]);
            }
            System.out.println(".");
        }
        return etype;
    }


    /**
     * Get the etype and checksum value for the specified encryption and
     * checksum type.
     *
     */
    /*
     * This method converts the string representation of encryption type and
     * checksum type to int value that can be later used by EType and
     * Checksum classes.
     */
    public int getType(String input) {
        int result = -1;
        if (input == null) {
            return result;
        }
        if (input.startsWith("d") || (input.startsWith("D"))) {
            if (input.equalsIgnoreCase("des-cbc-crc")) {
                result = EncryptedData.ETYPE_DES_CBC_CRC;
            } else if (input.equalsIgnoreCase("des-cbc-md5")) {
                result = EncryptedData.ETYPE_DES_CBC_MD5;
            } else if (input.equalsIgnoreCase("des-mac")) {
                result = Checksum.CKSUMTYPE_DES_MAC;
            } else if (input.equalsIgnoreCase("des-mac-k")) {
                result = Checksum.CKSUMTYPE_DES_MAC_K;
            } else if (input.equalsIgnoreCase("des-cbc-md4")) {
                result = EncryptedData.ETYPE_DES_CBC_MD4;
            } else if (input.equalsIgnoreCase("des3-cbc-sha1") ||
                input.equalsIgnoreCase("des3-hmac-sha1") ||
                input.equalsIgnoreCase("des3-cbc-sha1-kd") ||
                input.equalsIgnoreCase("des3-cbc-hmac-sha1-kd")) {
                result = EncryptedData.ETYPE_DES3_CBC_HMAC_SHA1_KD;
            }
        } else if (input.startsWith("a") || (input.startsWith("A"))) {
            // AES
            if (input.equalsIgnoreCase("aes128-cts") ||
                input.equalsIgnoreCase("aes128-cts-hmac-sha1-96")) {
                result = EncryptedData.ETYPE_AES128_CTS_HMAC_SHA1_96;
            } else if (input.equalsIgnoreCase("aes256-cts") ||
                input.equalsIgnoreCase("aes256-cts-hmac-sha1-96")) {
                result = EncryptedData.ETYPE_AES256_CTS_HMAC_SHA1_96;
            // ARCFOUR-HMAC
            } else if (input.equalsIgnoreCase("arcfour-hmac") ||
                   input.equalsIgnoreCase("arcfour-hmac-md5")) {
                result = EncryptedData.ETYPE_ARCFOUR_HMAC;
            }
        // RC4-HMAC
        } else if (input.equalsIgnoreCase("rc4-hmac")) {
            result = EncryptedData.ETYPE_ARCFOUR_HMAC;
        } else if (input.equalsIgnoreCase("CRC32")) {
            result = Checksum.CKSUMTYPE_CRC32;
        } else if (input.startsWith("r") || (input.startsWith("R"))) {
            if (input.equalsIgnoreCase("rsa-md5")) {
                result = Checksum.CKSUMTYPE_RSA_MD5;
            } else if (input.equalsIgnoreCase("rsa-md5-des")) {
                result = Checksum.CKSUMTYPE_RSA_MD5_DES;
            }
        } else if (input.equalsIgnoreCase("hmac-sha1-des3-kd")) {
            result = Checksum.CKSUMTYPE_HMAC_SHA1_DES3_KD;
        } else if (input.equalsIgnoreCase("hmac-sha1-96-aes128")) {
            result = Checksum.CKSUMTYPE_HMAC_SHA1_96_AES128;
        } else if (input.equalsIgnoreCase("hmac-sha1-96-aes256")) {
            result = Checksum.CKSUMTYPE_HMAC_SHA1_96_AES256;
        } else if (input.equalsIgnoreCase("hmac-md5-rc4") ||
                input.equalsIgnoreCase("hmac-md5-arcfour") ||
                input.equalsIgnoreCase("hmac-md5-enc")) {
            result = Checksum.CKSUMTYPE_HMAC_MD5_ARCFOUR;
        } else if (input.equalsIgnoreCase("NULL")) {
            result = EncryptedData.ETYPE_NULL;
        }

        return result;
    }

    /**
     * Resets the default kdc realm.
     * We do not need to synchronize these methods since assignments are atomic
     *
     * This method was useless. Kept here in case some class still calls it.
     */
    public void resetDefaultRealm(String realm) {
        if (DEBUG) {
            System.out.println(">>> Config try resetting default kdc " + realm);
        }
    }

    /**
     * Check to use addresses in tickets
     * use addresses if "no_addresses" or "noaddresses" is set to false
     */
    public boolean useAddresses() {
        boolean useAddr = false;
        // use addresses if "no_addresses" is set to false
        String value = getDefault("no_addresses", "libdefaults");
        useAddr = (value != null && value.equalsIgnoreCase("false"));
        if (useAddr == false) {
            // use addresses if "noaddresses" is set to false
            value = getDefault("noaddresses", "libdefaults");
            useAddr = (value != null && value.equalsIgnoreCase("false"));
        }
        return useAddr;
    }

    /**
     * Check if need to use DNS to locate Kerberos services
     */
    public boolean useDNS(String name) {
        String value = getDefault(name, "libdefaults");
        if (value == null) {
            value = getDefault("dns_fallback", "libdefaults");
            if ("false".equalsIgnoreCase(value)) {
                return false;
            } else {
                return true;
            }
        } else {
            return value.equalsIgnoreCase("true");
        }
    }

    /**
     * Check if need to use DNS to locate the KDC
     */
    public boolean useDNS_KDC() {
        return useDNS("dns_lookup_kdc");
    }

    /*
     * Check if need to use DNS to locate the Realm
     */
    public boolean useDNS_Realm() {
        return useDNS("dns_lookup_realm");
    }

    /**
     * Gets default realm.
     * @throws KrbException where no realm can be located
     * @return the default realm, always non null
     */
    public String getDefaultRealm() throws KrbException {
        if (defaultRealm != null) {
            return defaultRealm;
        }
        Exception cause = null;
        String realm = getDefault("default_realm", "libdefaults");
        if ((realm == null) && useDNS_Realm()) {
            // use DNS to locate Kerberos realm
            try {
                realm = getRealmFromDNS();
            } catch (KrbException ke) {
                cause = ke;
            }
        }
        if (realm == null) {
            realm = java.security.AccessController.doPrivileged(
                    new java.security.PrivilegedAction<String>() {
                @Override
                public String run() {
                    String osname = System.getProperty("os.name");
                    if (osname.startsWith("Windows")) {
                        return System.getenv("USERDNSDOMAIN");
                    }
                    return null;
                }
            });
        }
        if (realm == null) {
            KrbException ke = new KrbException("Cannot locate default realm");
            if (cause != null) {
                ke.initCause(cause);
            }
            throw ke;
        }
        return realm;
    }

    /**
     * Returns a list of KDC's with each KDC separated by a space
     *
     * @param realm the realm for which the KDC list is desired
     * @throws KrbException if there's no way to find KDC for the realm
     * @return the list of KDCs separated by a space, always non null
     */
    public String getKDCList(String realm) throws KrbException {
        if (realm == null) {
            realm = getDefaultRealm();
        }
        if (realm.equalsIgnoreCase(defaultRealm)) {
            return defaultKDC;
        }
        Exception cause = null;
        String kdcs = getDefault("kdc", realm);
        if ((kdcs == null) && useDNS_KDC()) {
            // use DNS to locate KDC
            try {
                kdcs = getKDCFromDNS(realm);
            } catch (KrbException ke) {
                cause = ke;
            }
        }
        if (kdcs == null) {
            kdcs = java.security.AccessController.doPrivileged(
                    new java.security.PrivilegedAction<String>() {
                @Override
                public String run() {
                    String osname = System.getProperty("os.name");
                    if (osname.startsWith("Windows")) {
                        String logonServer = System.getenv("LOGONSERVER");
                        if (logonServer != null
                                && logonServer.startsWith("\\\\")) {
                            logonServer = logonServer.substring(2);
                        }
                        return logonServer;
                    }
                    return null;
                }
            });
        }
        if (kdcs == null) {
            if (defaultKDC != null) {
                return defaultKDC;
            }
            KrbException ke = new KrbException("Cannot locate KDC");
            if (cause != null) {
                ke.initCause(cause);
            }
            throw ke;
        }
        return kdcs;
    }

    /**
     * Locate Kerberos realm using DNS
     *
     * @return the Kerberos realm
     */
    private String getRealmFromDNS() throws KrbException {
        // use DNS to locate Kerberos realm
        String realm = null;
        String hostName = null;
        try {
            hostName = InetAddress.getLocalHost().getCanonicalHostName();
        } catch (UnknownHostException e) {
            KrbException ke = new KrbException(Krb5.KRB_ERR_GENERIC,
                "Unable to locate Kerberos realm: " + e.getMessage());
            ke.initCause(e);
            throw (ke);
        }
        // get the domain realm mapping from the configuration
        String mapRealm = PrincipalName.mapHostToRealm(hostName);
        if (mapRealm == null) {
            // No match. Try search and/or domain in /etc/resolv.conf
            List<String> srchlist = ResolverConfiguration.open().searchlist();
            for (String domain: srchlist) {
                realm = checkRealm(domain);
                if (realm != null) {
                    break;
                }
            }
        } else {
            realm = checkRealm(mapRealm);
        }
        if (realm == null) {
            throw new KrbException(Krb5.KRB_ERR_GENERIC,
                                "Unable to locate Kerberos realm");
        }
        return realm;
    }

    /**
     * Check if the provided realm is the correct realm
     * @return the realm if correct, or null otherwise
     */
    private static String checkRealm(String mapRealm) {
        if (DEBUG) {
            System.out.println("getRealmFromDNS: trying " + mapRealm);
        }
        String[] records = null;
        String newRealm = mapRealm;
        while ((records == null) && (newRealm != null)) {
            // locate DNS TXT record
            records = KrbServiceLocator.getKerberosService(newRealm);
            newRealm = Realm.parseRealmComponent(newRealm);
            // if no DNS TXT records found, try again using sub-realm
        }
        if (records != null) {
            for (int i = 0; i < records.length; i++) {
                if (records[i].equalsIgnoreCase(mapRealm)) {
                    return records[i];
                }
            }
        }
        return null;
    }

    /**
     * Locate KDC using DNS
     *
     * @param realm the realm for which the master KDC is desired
     * @return the KDC
     */
    private String getKDCFromDNS(String realm) throws KrbException {
        // use DNS to locate KDC
        String kdcs = "";
        String[] srvs = null;
        // locate DNS SRV record using UDP
        if (DEBUG) {
            System.out.println("getKDCFromDNS using UDP");
        }
        srvs = KrbServiceLocator.getKerberosService(realm, "_udp");
        if (srvs == null) {
            // locate DNS SRV record using TCP
            if (DEBUG) {
                System.out.println("getKDCFromDNS using TCP");
            }
            srvs = KrbServiceLocator.getKerberosService(realm, "_tcp");
        }
        if (srvs == null) {
            // no DNS SRV records
            throw new KrbException(Krb5.KRB_ERR_GENERIC,
                "Unable to locate KDC for realm " + realm);
        }
        if (srvs.length == 0) {
            return null;
        }
        for (int i = 0; i < srvs.length; i++) {
            kdcs += srvs[i].trim() + " ";
        }
        kdcs = kdcs.trim();
        if (kdcs.equals("")) {
            return null;
        }
        return kdcs;
    }

    private boolean fileExists(String name) {
        return java.security.AccessController.doPrivileged(
                                new FileExistsAction(name));
    }

    static class FileExistsAction
        implements java.security.PrivilegedAction<Boolean> {

        private String fileName;

        public FileExistsAction(String fileName) {
            this.fileName = fileName;
        }

        public Boolean run() {
            return new File(fileName).exists();
        }
    }

    // Shows the content of the Config object for debug purpose.
    //
    // {
    //      libdefaults = {
    //          default_realm = R
    //      }
    //      realms = {
    //          R = {
    //              kdc = [k1,k2]
    //          }
    //      }
    // }

    @Override
    public String toString() {
        StringBuffer sb = new StringBuffer();
        toStringInternal("", stanzaTable, sb);
        return sb.toString();
    }
    private static void toStringInternal(String prefix, Object obj,
            StringBuffer sb) {
        if (obj instanceof String) {
            // A string value, just print it
            sb.append(obj).append('\n');
        } else if (obj instanceof Hashtable) {
            // A table, start a new sub-section...
            Hashtable<?, ?> tab = (Hashtable<?, ?>)obj;
            sb.append("{\n");
            for (Object o: tab.keySet()) {
                // ...indent, print "key = ", and
                sb.append(prefix).append("    ").append(o).append(" = ");
                // ...go recursively into value
                toStringInternal(prefix + "    ", tab.get(o), sb);
            }
            sb.append(prefix).append("}\n");
        } else if (obj instanceof Vector) {
            // A vector of strings, print them inside [ and ]
            Vector<?> v = (Vector<?>)obj;
            sb.append("[");
            boolean first = true;
            for (Object o: v.toArray()) {
                if (!first) sb.append(",");
                sb.append(o);
                first = false;
            }
            sb.append("]\n");
        }
    }
}