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/* PBKDF2.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

combination.

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

modules, and to copy and distribute the resulting executable under

terms of your choice, provided that you also meet, for each linked

independent module, the terms and conditions of the license of that

module.  An independent module is a module which is not derived from

or based on this library.  If you modify this library, you may extend

this exception to your version of the library, but you are not

obligated to do so.  If you do not wish to do so, delete this

exception statement from your version.  */

package gnu.javax.crypto.prng;

import gnu.java.security.prng.BasePRNG;

import gnu.java.security.prng.LimitReachedException;

import gnu.javax.crypto.mac.HMac;

import gnu.javax.crypto.mac.IMac;

import java.io.UnsupportedEncodingException;

import java.util.Arrays;

import java.util.HashMap;

import java.util.Map;

/**

 * An implementation of the <i>key derivation function</i> KDF2 from PKCS #5:

 * Password-Based Cryptography (<b>PBE</b>). This KDF is essentially a way to

 * transform a password and a salt into a stream of random bytes, which may then

 * be used to initialize a cipher or a MAC.

 * <p>

 * This version uses a MAC as its pseudo-random function, and the password is

 * used as the key.

 * <p>

 * References:

 * <ol>

 * <li>B. Kaliski, <a href="http://www.ietf.org/rfc/rfc2898.txt">RFC 2898:

 * Password-Based Cryptography Specification, Version 2.0</a></li>

 * </ol>

 */

public class PBKDF2

    extends BasePRNG

    implements Cloneable

{

  /**

   * The bytes fed into the MAC. This is initially the concatenation of the salt

   * and the block number.

   */

  private byte[] in;

  /** The iteration count. */

  private int iterationCount;

  /** The salt. */

  private byte[] salt;

  /** The MAC (the pseudo-random function we use). */

  private IMac mac;

  /** The number of hLen-sized blocks generated. */

  private long count;

  /**

   * Creates a new PBKDF2 object. The argument is the MAC that will serve as the

   * pseudo-random function. The MAC does not need to be initialized.

   *

   * @param mac The pseudo-random function.

   */

  public PBKDF2(IMac mac)

  {

    super("PBKDF2-" + mac.name());

    this.mac = mac;

    iterationCount = -1;

  }

  public void setup(Map attributes)

  {

    Map macAttrib = new HashMap();

    macAttrib.put(HMac.USE_WITH_PKCS5_V2, Boolean.TRUE);

    byte[] s = (byte[]) attributes.get(IPBE.SALT);

    if (s == null)

      {

        if (salt == null)

          throw new IllegalArgumentException("no salt specified");

        // Otherwise re-use.

      }

    else

      salt = s;

    byte[] macKeyMaterial;

    char[] password = (char[]) attributes.get(IPBE.PASSWORD);

    if (password != null)

      {

        String encoding = (String) attributes.get(IPBE.PASSWORD_ENCODING);

        if (encoding == null || encoding.trim().length() == 0)

          encoding = IPBE.DEFAULT_PASSWORD_ENCODING;

        else

          encoding = encoding.trim();

        try

          {

            macKeyMaterial = new String(password).getBytes(encoding);

          }

        catch (UnsupportedEncodingException uee)

          {

            throw new IllegalArgumentException("Unknown or unsupported encoding: "

                                               + encoding, uee);

          }

      }

    else

      macKeyMaterial = (byte[]) attributes.get(IMac.MAC_KEY_MATERIAL);

    if (macKeyMaterial != null)

      macAttrib.put(IMac.MAC_KEY_MATERIAL, macKeyMaterial);

    else if (! initialised)

      throw new IllegalArgumentException(

          "Neither password nor key-material were specified");

    // otherwise re-use previous password/key-material

    try

      {

        mac.init(macAttrib);

      }

    catch (Exception x)

      {

        throw new IllegalArgumentException(x.getMessage());

      }

    Integer ic = (Integer) attributes.get(IPBE.ITERATION_COUNT);

    if (ic != null)

      iterationCount = ic.intValue();

    if (iterationCount <= 0)

      throw new IllegalArgumentException("bad iteration count");

    count = 0L;

    buffer = new byte[mac.macSize()];

    try

      {

        fillBlock();

      }

    catch (LimitReachedException x)

      {

        throw new Error(x.getMessage());

      }

  }

  public void fillBlock() throws LimitReachedException

  {

    if (++count > ((1L << 32) - 1))

      throw new LimitReachedException();

    Arrays.fill(buffer, (byte) 0x00);

    int limit = salt.length;

    in = new byte[limit + 4];

    System.arraycopy(salt, 0, in, 0, salt.length);

    in[limit++] = (byte)(count >>> 24);

    in[limit++] = (byte)(count >>> 16);

    in[limit++] = (byte)(count >>> 8);

    in[limit  ] = (byte) count;

    for (int i = 0; i < iterationCount; i++)

      {

        mac.reset();

        mac.update(in, 0, in.length);

        in = mac.digest();

        for (int j = 0; j < buffer.length; j++)

          buffer[j] ^= in[j];

      }

  }

}