/* PasswordFile.java -- 
   Copyright (C) 2003, 2006 Free Software Foundation, Inc.

This file is a part of GNU Classpath.

GNU Classpath is free software; you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation; either version 2 of the License, or (at
your option) any later version.

GNU Classpath 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 for more details.

You should have received a copy of the GNU General Public License
along with GNU Classpath; if not, write to the Free Software
Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301
USA

Linking this library statically or dynamically with other modules is
making a combined work based on this library.  Thus, the terms and
conditions of the GNU General Public License cover the whole
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As a special exception, the copyright holders of this library give you
permission to link this library with independent modules to produce an
executable, regardless of the license terms of these independent
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terms of your choice, provided that you also meet, for each linked
independent module, the terms and conditions of the license of that
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package gnu.javax.crypto.sasl.srp;

import gnu.java.security.Registry;
import gnu.java.security.util.Util;
import gnu.javax.crypto.key.srp6.SRPAlgorithm;
import gnu.javax.crypto.sasl.NoSuchUserException;
import gnu.javax.crypto.sasl.UserAlreadyExistsException;

import java.io.BufferedReader;
import java.io.File;
import java.io.FileInputStream;
import java.io.FileNotFoundException;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.io.PrintWriter;
import java.io.UnsupportedEncodingException;
import java.math.BigInteger;
import java.util.HashMap;
import java.util.Iterator;
import java.util.NoSuchElementException;
import java.util.StringTokenizer;

/**
 * The implementation of SRP password files.
 * <p>
 * For SRP, there are three (3) files:
 * <ol>
 * <li>The password configuration file: tpasswd.conf. It contains the pairs
 * &lt;N,g> indexed by a number for each pair used for a user. By default, this
 * file's pathname is constructed from the base password file pathname by
 * prepending it with the ".conf" suffix.</li>
 * <li>The base password file: tpasswd. It contains the related password
 * entries for all the users with values computed using SRP's default message
 * digest algorithm: SHA-1 (with 160-bit output block size).</li>
 * <li>The extended password file: tpasswd2. Its name, by default, is
 * constructed by adding the suffix "2" to the fully qualified pathname of the
 * base password file. It contains, in addition to the same fields as the base
 * password file, albeit with a different verifier value, an extra field
 * identifying the message digest algorithm used to compute this (verifier)
 * value.</li>
 * </ol>
 * <p>
 * This implementation assumes the following message digest algorithm codes:
 * <ul>
 * <li>0: the default hash algorithm, which is SHA-1 (or its alias SHA-160).</li>
 * <li>1: MD5.</li>
 * <li>2: RIPEMD-128.</li>
 * <li>3: RIPEMD-160.</li>
 * <li>4: SHA-256.</li>
 * <li>5: SHA-384.</li>
 * <li>6: SHA-512.</li>
 * </ul>
 * <p>
 * <b>IMPORTANT:</b> This method computes the verifiers as described in
 * RFC-2945, which differs from the description given on the web page for SRP-6.
 * <p>
 * Reference:
 * <ol>
 * <li><a href="http://srp.stanford.edu/design.html">SRP Protocol Design</a><br>
 * Thomas J. Wu.</li>
 * </ol>
 */
public class PasswordFile
{
  // names of property keys used in this class
  private static final String USER_FIELD = "user";
  private static final String VERIFIERS_FIELD = "verifier";
  private static final String SALT_FIELD = "salt";
  private static final String CONFIG_FIELD = "config";
  private static String DEFAULT_FILE;
  static
    {
      DEFAULT_FILE = System.getProperty(SRPRegistry.PASSWORD_FILE,
                                        SRPRegistry.DEFAULT_PASSWORD_FILE);
    }
  /** The SRP algorithm instances used by this object. */
  private static final HashMap srps;
  static
    {
      final HashMap map = new HashMap(SRPRegistry.SRP_ALGORITHMS.length);
      // The first entry MUST exist. The others are optional.
      map.put("0", SRP.instance(SRPRegistry.SRP_ALGORITHMS[0]));
      for (int i = 1; i < SRPRegistry.SRP_ALGORITHMS.length; i++)
        {
          try
            {
              map.put(String.valueOf(i),
                      SRP.instance(SRPRegistry.SRP_ALGORITHMS[i]));
            }
          catch (Exception x)
            {
              System.err.println("Ignored: " + x);
              x.printStackTrace(System.err);
            }
        }
      srps = map;
    }

  private String confName, pwName, pw2Name;
  private File configFile, passwdFile, passwd2File;
  private long lastmodPasswdFile, lastmodPasswd2File;
  private HashMap entries = new HashMap();
  private HashMap configurations = new HashMap();
  // default N values to use when creating a new password.conf file
  private static final BigInteger[] Nsrp = new BigInteger[] {
      SRPAlgorithm.N_2048,
      SRPAlgorithm.N_1536,
      SRPAlgorithm.N_1280,
      SRPAlgorithm.N_1024,
      SRPAlgorithm.N_768,
      SRPAlgorithm.N_640,
      SRPAlgorithm.N_512 };

  public PasswordFile() throws IOException
  {
    this(DEFAULT_FILE);
  }

  public PasswordFile(final File pwFile) throws IOException
  {
    this(pwFile.getAbsolutePath());
  }

  public PasswordFile(final String pwName) throws IOException
  {
    this(pwName, pwName + "2", pwName + ".conf");
  }

  public PasswordFile(final String pwName, final String confName)
      throws IOException
  {
    this(pwName, pwName + "2", confName);
  }

  public PasswordFile(final String pwName, final String pw2Name,
                      final String confName) throws IOException
  {
    super();

    this.pwName = pwName;
    this.pw2Name = pw2Name;
    this.confName = confName;

    readOrCreateConf();
    update();
  }

  /**
   * Returns a string representing the decimal value of an integer identifying
   * the message digest algorithm to use for the SRP computations.
   * 
   * @param mdName the canonical name of a message digest algorithm.
   * @return a string representing the decimal value of an ID for that
   *         algorithm.
   */
  private static final String nameToID(final String mdName)
  {
    if (Registry.SHA_HASH.equalsIgnoreCase(mdName)
        || Registry.SHA1_HASH.equalsIgnoreCase(mdName)
        || Registry.SHA160_HASH.equalsIgnoreCase(mdName))
      return "0";
    else if (Registry.MD5_HASH.equalsIgnoreCase(mdName))
      return "1";
    else if (Registry.RIPEMD128_HASH.equalsIgnoreCase(mdName))
      return "2";
    else if (Registry.RIPEMD160_HASH.equalsIgnoreCase(mdName))
      return "3";
    else if (Registry.SHA256_HASH.equalsIgnoreCase(mdName))
      return "4";
    else if (Registry.SHA384_HASH.equalsIgnoreCase(mdName))
      return "5";
    else if (Registry.SHA512_HASH.equalsIgnoreCase(mdName))
      return "6";
    return "0";
  }

  /**
   * Checks if the current configuration file contains the &lt;N, g> pair for
   * the designated <code>index</code>.
   * 
   * @param index a string representing 1-digit identification of an &lt;N, g>
   *          pair used.
   * @return <code>true</code> if the designated <code>index</code> is that
   *         of a known &lt;N, g> pair, and <code>false</code> otherwise.
   * @throws IOException if an exception occurs during the process.
   * @see SRPRegistry#N_2048_BITS
   * @see SRPRegistry#N_1536_BITS
   * @see SRPRegistry#N_1280_BITS
   * @see SRPRegistry#N_1024_BITS
   * @see SRPRegistry#N_768_BITS
   * @see SRPRegistry#N_640_BITS
   * @see SRPRegistry#N_512_BITS
   */
  public synchronized boolean containsConfig(final String index)
      throws IOException
  {
    checkCurrent();
    return configurations.containsKey(index);
  }

  /**
   * Returns a pair of strings representing the pair of <code>N</code> and
   * <code>g</code> MPIs for the designated <code>index</code>.
   * 
   * @param index a string representing 1-digit identification of an &lt;N, g>
   *          pair to look up.
   * @return a pair of strings, arranged in an array, where the first (at index
   *         position #0) is the repesentation of the MPI <code>N</code>, and
   *         the second (at index position #1) is the representation of the MPI
   *         <code>g</code>. If the <code>index</code> refers to an unknown
   *         pair, then an empty string array is returned.
   * @throws IOException if an exception occurs during the process.
   */
  public synchronized String[] lookupConfig(final String index)
      throws IOException
  {
    checkCurrent();
    String[] result = null;
    if (configurations.containsKey(index))
      result = (String[]) configurations.get(index);
    return result;
  }

  public synchronized boolean contains(final String user) throws IOException
  {
    checkCurrent();
    return entries.containsKey(user);
  }

  public synchronized void add(final String user, final String passwd,
                               final byte[] salt, final String index)
      throws IOException
  {
    checkCurrent();
    if (entries.containsKey(user))
      throw new UserAlreadyExistsException(user);
    final HashMap fields = new HashMap(4);
    fields.put(USER_FIELD, user); // 0
    fields.put(VERIFIERS_FIELD, newVerifiers(user, salt, passwd, index)); // 1
    fields.put(SALT_FIELD, Util.toBase64(salt)); // 2
    fields.put(CONFIG_FIELD, index); // 3
    entries.put(user, fields);
    savePasswd();
  }

  public synchronized void changePasswd(final String user, final String passwd)
      throws IOException
  {
    checkCurrent();
    if (! entries.containsKey(user))
      throw new NoSuchUserException(user);
    final HashMap fields = (HashMap) entries.get(user);
    final byte[] salt;
    try
      {
        salt = Util.fromBase64((String) fields.get(SALT_FIELD));
      }
    catch (NumberFormatException x)
      {
        throw new IOException("Password file corrupt");
      }
    final String index = (String) fields.get(CONFIG_FIELD);
    fields.put(VERIFIERS_FIELD, newVerifiers(user, salt, passwd, index));
    entries.put(user, fields);
    savePasswd();
  }

  public synchronized void savePasswd() throws IOException
  {
    final FileOutputStream f1 = new FileOutputStream(passwdFile);
    final FileOutputStream f2 = new FileOutputStream(passwd2File);
    PrintWriter pw1 = null;
    PrintWriter pw2 = null;
    try
      {
        pw1 = new PrintWriter(f1, true);
        pw2 = new PrintWriter(f2, true);
        this.writePasswd(pw1, pw2);
      }
    finally
      {
        if (pw1 != null)
          try
            {
              pw1.flush();
            }
          finally
            {
              pw1.close();
            }
        if (pw2 != null)
          try
            {
              pw2.flush();
            }
          finally
            {
              pw2.close();
            }
        try
          {
            f1.close();
          }
        catch (IOException ignored)
          {
          }
        try
          {
            f2.close();
          }
        catch (IOException ignored)
          {
          }
      }
    lastmodPasswdFile = passwdFile.lastModified();
    lastmodPasswd2File = passwd2File.lastModified();
  }

  /**
   * Returns the triplet: verifier, salt and configuration file index, of a
   * designated user, and a designated message digest algorithm name, as an
   * array of strings.
   * 
   * @param user the username.
   * @param mdName the canonical name of the SRP's message digest algorithm.
   * @return a string array containing, in this order, the BASE-64 encodings of
   *         the verifier, the salt and the index in the password configuration
   *         file of the MPIs N and g of the designated user.
   */
  public synchronized String[] lookup(final String user, final String mdName)
      throws IOException
  {
    checkCurrent();
    if (! entries.containsKey(user))
      throw new NoSuchUserException(user);
    final HashMap fields = (HashMap) entries.get(user);
    final HashMap verifiers = (HashMap) fields.get(VERIFIERS_FIELD);
    final String salt = (String) fields.get(SALT_FIELD);
    final String index = (String) fields.get(CONFIG_FIELD);
    final String verifier = (String) verifiers.get(nameToID(mdName));
    return new String[] { verifier, salt, index };
  }

  private synchronized void readOrCreateConf() throws IOException
  {
    configurations.clear();
    final FileInputStream fis;
    configFile = new File(confName);
    try
      {
        fis = new FileInputStream(configFile);
        readConf(fis);
      }
    catch (FileNotFoundException x)
      { // create a default one
        final String g = Util.toBase64(Util.trim(new BigInteger("2")));
        String index, N;
        for (int i = 0; i < Nsrp.length; i++)
          {
            index = String.valueOf(i + 1);
            N = Util.toBase64(Util.trim(Nsrp[i]));
            configurations.put(index, new String[] { N, g });
          }
        FileOutputStream f0 = null;
        PrintWriter pw0 = null;
        try
          {
            f0 = new FileOutputStream(configFile);
            pw0 = new PrintWriter(f0, true);
            this.writeConf(pw0);
          }
        finally
          {
            if (pw0 != null)
              pw0.close();
            else if (f0 != null)
              f0.close();
          }
      }
  }

  private void readConf(final InputStream in) throws IOException
  {
    final BufferedReader din = new BufferedReader(new InputStreamReader(in));
    String line, index, N, g;
    StringTokenizer st;
    while ((line = din.readLine()) != null)
      {
        st = new StringTokenizer(line, ":");
        try
          {
            index = st.nextToken();
            N = st.nextToken();
            g = st.nextToken();
          }
        catch (NoSuchElementException x)
          {
            throw new IOException("SRP password configuration file corrupt");
          }
        configurations.put(index, new String[] { N, g });
      }
  }

  private void writeConf(final PrintWriter pw)
  {
    String ndx;
    String[] mpi;
    StringBuffer sb;
    for (Iterator it = configurations.keySet().iterator(); it.hasNext();)
      {
        ndx = (String) it.next();
        mpi = (String[]) configurations.get(ndx);
        sb = new StringBuffer(ndx)
            .append(":").append(mpi[0])
            .append(":").append(mpi[1]);
        pw.println(sb.toString());
      }
  }

  /**
   * Compute the new verifiers for the designated username and password.
   * <p>
   * <b>IMPORTANT:</b> This method computes the verifiers as described in
   * RFC-2945, which differs from the description given on the web page for
   * SRP-6.
   * 
   * @param user the user's name.
   * @param s the user's salt.
   * @param password the user's password
   * @param index the index of the &lt;N, g> pair to use for this user.
   * @return a {@link java.util.Map} of user verifiers.
   * @throws UnsupportedEncodingException if the US-ASCII decoder is not
   *           available on this platform.
   */
  private HashMap newVerifiers(final String user, final byte[] s,
                               final String password, final String index)
      throws UnsupportedEncodingException
  {
    // to ensure inter-operability with non-java tools
    final String[] mpi = (String[]) configurations.get(index);
    final BigInteger N = new BigInteger(1, Util.fromBase64(mpi[0]));
    final BigInteger g = new BigInteger(1, Util.fromBase64(mpi[1]));
    final HashMap result = new HashMap(srps.size());
    BigInteger x, v;
    SRP srp;
    for (int i = 0; i < srps.size(); i++)
      {
        final String digestID = String.valueOf(i);
        srp = (SRP) srps.get(digestID);
        x = new BigInteger(1, srp.computeX(s, user, password));
        v = g.modPow(x, N);
        final String verifier = Util.toBase64(v.toByteArray());
        result.put(digestID, verifier);
      }
    return result;
  }

  private synchronized void update() throws IOException
  {
    entries.clear();
    FileInputStream fis;
    passwdFile = new File(pwName);
    lastmodPasswdFile = passwdFile.lastModified();
    try
      {
        fis = new FileInputStream(passwdFile);
        readPasswd(fis);
      }
    catch (FileNotFoundException ignored)
      {
      }
    passwd2File = new File(pw2Name);
    lastmodPasswd2File = passwd2File.lastModified();
    try
      {
        fis = new FileInputStream(passwd2File);
        readPasswd2(fis);
      }
    catch (FileNotFoundException ignored)
      {
      }
  }

  private void checkCurrent() throws IOException
  {
    if (passwdFile.lastModified() > lastmodPasswdFile
        || passwd2File.lastModified() > lastmodPasswd2File)
      update();
  }

  private void readPasswd(final InputStream in) throws IOException
  {
    final BufferedReader din = new BufferedReader(new InputStreamReader(in));
    String line, user, verifier, salt, index;
    StringTokenizer st;
    while ((line = din.readLine()) != null)
      {
        st = new StringTokenizer(line, ":");
        try
          {
            user = st.nextToken();
            verifier = st.nextToken();
            salt = st.nextToken();
            index = st.nextToken();
          }
        catch (NoSuchElementException x)
          {
            throw new IOException("SRP base password file corrupt");
          }
        final HashMap verifiers = new HashMap(6);
        verifiers.put("0", verifier);
        final HashMap fields = new HashMap(4);
        fields.put(USER_FIELD, user);
        fields.put(VERIFIERS_FIELD, verifiers);
        fields.put(SALT_FIELD, salt);
        fields.put(CONFIG_FIELD, index);
        entries.put(user, fields);
      }
  }

  private void readPasswd2(final InputStream in) throws IOException
  {
    final BufferedReader din = new BufferedReader(new InputStreamReader(in));
    String line, digestID, user, verifier;
    StringTokenizer st;
    HashMap fields, verifiers;
    while ((line = din.readLine()) != null)
      {
        st = new StringTokenizer(line, ":");
        try
          {
            digestID = st.nextToken();
            user = st.nextToken();
            verifier = st.nextToken();
          }
        catch (NoSuchElementException x)
          {
            throw new IOException("SRP extended password file corrupt");
          }
        fields = (HashMap) entries.get(user);
        if (fields != null)
          {
            verifiers = (HashMap) fields.get(VERIFIERS_FIELD);
            verifiers.put(digestID, verifier);
          }
      }
  }

  private void writePasswd(final PrintWriter pw1, final PrintWriter pw2)
      throws IOException
  {
    String user, digestID;
    HashMap fields, verifiers;
    StringBuffer sb1, sb2;
    Iterator j;
    final Iterator i = entries.keySet().iterator();
    while (i.hasNext())
      {
        user = (String) i.next();
        fields = (HashMap) entries.get(user);
        if (! user.equals(fields.get(USER_FIELD)))
          throw new IOException("Inconsistent SRP password data");
        verifiers = (HashMap) fields.get(VERIFIERS_FIELD);
        sb1 = new StringBuffer(user)
            .append(":").append((String) verifiers.get("0"))
            .append(":").append((String) fields.get(SALT_FIELD))
            .append(":").append((String) fields.get(CONFIG_FIELD));
        pw1.println(sb1.toString());
        // write extended information
        j = verifiers.keySet().iterator();
        while (j.hasNext())
          {
            digestID = (String) j.next();
            if (! "0".equals(digestID))
              {
                // #0 is the default digest, already present in tpasswd!
                sb2 = new StringBuffer(digestID)
                    .append(":").append(user)
                    .append(":").append((String) verifiers.get(digestID));
                pw2.println(sb2.toString());
              }
          }
      }
  }
}