/* KDF.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 modifyit under the terms of the GNU General Public License as published bythe Free Software Foundation; either version 2 of the License, or (atyour option) any later version.GNU Classpath is distributed in the hope that it will be useful, butWITHOUT ANY WARRANTY; without even the implied warranty ofMERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNUGeneral Public License for more details.You should have received a copy of the GNU General Public Licensealong with GNU Classpath; if not, write to the Free SoftwareFoundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301USALinking this library statically or dynamically with other modules ismaking a combined work based on this library.  Thus, the terms andconditions of the GNU General Public License cover the wholecombination.As a special exception, the copyright holders of this library give youpermission to link this library with independent modules to produce anexecutable, regardless of the license terms of these independentmodules, and to copy and distribute the resulting executable underterms of your choice, provided that you also meet, for each linkedindependent module, the terms and conditions of the license of thatmodule.  An independent module is a module which is not derived fromor based on this library.  If you modify this library, you may extendthis exception to your version of the library, but you are notobligated to do so.  If you do not wish to do so, delete thisexception statement from your version.  */package gnu.javax.crypto.sasl.srp;import gnu.java.security.Registry;import gnu.java.security.prng.LimitReachedException;import gnu.java.security.util.PRNG;import gnu.javax.crypto.cipher.IBlockCipher;import gnu.javax.crypto.prng.UMacGenerator;import java.util.HashMap;/** * <p>The SASL-SRP KDF implementation, which is also used, depending on how it * was instantiated, as a secure Pseudo Random Number Generator.</p> */public class KDF{  // Constants and variables  // -------------------------------------------------------------------------  private static final int AES_BLOCK_SIZE = 16; // default block size for the AES  private static final int AES_KEY_SIZE = 16; // default key size for the AES  private static final byte[] buffer = new byte[1];  /** Our default source of randomness. */  private static final PRNG prng = PRNG.getInstance();  /** The shared secret K to use. */  //   private byte[] keyMaterial;  /** The underlying UMAC Generator instance. */  private UMacGenerator umac = null;  // Constructor(s)  // -------------------------------------------------------------------------  /**   * <p>Constructs an instance of the <code>KDF</code> initialised with the   * designated shared secret bytes.</p>   *   * @param keyMaterial the SASL SRP shared secret (K) bytes.   */  private KDF(final byte[] keyMaterial, final int ndx)  {    super();    //      if (ndx != 0) {    //         this.keyMaterial = (byte[]) keyMaterial.clone();    //      }    final HashMap map = new HashMap();    map.put(UMacGenerator.CIPHER, Registry.AES_CIPHER);    map.put(UMacGenerator.INDEX, new Integer(ndx));    map.put(IBlockCipher.CIPHER_BLOCK_SIZE, new Integer(AES_BLOCK_SIZE));    final byte[] key = new byte[AES_KEY_SIZE];    System.arraycopy(keyMaterial, 0, key, 0, AES_KEY_SIZE);    map.put(IBlockCipher.KEY_MATERIAL, key);    umac = new UMacGenerator();    umac.init(map);    //System.out.println("**** Initialised KDF with: "+gnu.crypto.util.Util.dumpString(key));  }  // Class methods  // -------------------------------------------------------------------------  /**   * <p>A Factory mehod that returns an instance of a <code>KDF</code> based on   * supplied seed data.</p>   *   * @param K the SASL SRP shared secret for a <code>KDF</code> to be used for   * <i>CALG</i> and <i>IALG</i> setup. <code>null</code> otherwise.   * @return an instance of a <code>KDF</code>.   */  static final KDF getInstance(final byte[] K)  {    int ndx = -1;    final byte[] keyMaterial;    if (K != null)      {        keyMaterial = K;        ndx = 0;      }    else      {        keyMaterial = new byte[AES_BLOCK_SIZE];        while (ndx < 1 || ndx > 255)          ndx = (byte) nextByte();      }    return new KDF(keyMaterial, ndx);  }  private static synchronized final int nextByte()  {    prng.nextBytes(buffer);    return (buffer[0] & 0xFF);  }  // Instance methods  // -------------------------------------------------------------------------  /**   * <p>Returns a designated number of bytes suitable for use in the SASL SRP   * mechanism.</p>   *   * @param length the number of bytes needed.   * @return a byte array containing the generated/selected bytes.   */  public synchronized byte[] derive(final int length)  {    final byte[] result = new byte[length];    //      if (keyMaterial == null || length > keyMaterial.length) {    try      {        umac.nextBytes(result, 0, length);      }    catch (IllegalStateException x)      { // should not happen        x.printStackTrace(System.err);      }    catch (LimitReachedException x)      { // idem        x.printStackTrace(System.err);      }    //      } else {    //         System.arraycopy(keyMaterial, 0, result, 0, length);    //      }    return result;  }}