package gnu.crypto.sasl.srp;
// ----------------------------------------------------------------------------
// $Id: KDF.java,v 1.4 2005/10/06 04:24:18 rsdio Exp $
//
// Copyright (C) 2003 Free Software Foundation, Inc.
//
// This file is part of GNU Crypto.
//
// GNU Crypto 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, or (at your option)
// any later version.
//
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// 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 this program; see the file COPYING. If not, write to the
//
// Free Software Foundation Inc.,
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// 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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// you permission to link this library with independent modules to
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// ----------------------------------------------------------------------------
import gnu.crypto.Registry;
import gnu.crypto.cipher.IBlockCipher;
import gnu.crypto.prng.LimitReachedException;
import gnu.crypto.prng.UMacGenerator;
import gnu.crypto.util.PRNG;
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>
*
* @version $Revision: 1.4 $
*/
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];
/** 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;
}
}