| /* 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 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.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; |
| |
| /** |
| * The SASL-SRP KDF implementation, which is also used, depending on how it was |
| * instantiated, as a secure Pseudo Random Number Generator. |
| */ |
| public class KDF |
| { |
| private static final int AES_BLOCK_SIZE = 16; // default block size for 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 underlying UMAC Generator instance. */ |
| private UMacGenerator umac = null; |
| |
| /** |
| * Constructs an instance of the <code>KDF</code> initialised with the |
| * designated shared secret bytes. |
| * |
| * @param keyMaterial the SASL SRP shared secret (K) bytes. |
| */ |
| private KDF(final byte[] keyMaterial, final int ndx) |
| { |
| super(); |
| |
| final HashMap map = new HashMap(); |
| map.put(UMacGenerator.CIPHER, Registry.AES_CIPHER); |
| map.put(UMacGenerator.INDEX, Integer.valueOf(ndx)); |
| map.put(IBlockCipher.CIPHER_BLOCK_SIZE, Integer.valueOf(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); |
| } |
| |
| /** |
| * A Factory mehod that returns an instance of a <code>KDF</code> based on |
| * supplied seed data. |
| * |
| * @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); |
| } |
| |
| /** |
| * Returns a designated number of bytes suitable for use in the SASL SRP |
| * mechanism. |
| * |
| * @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]; |
| try |
| { |
| umac.nextBytes(result, 0, length); |
| } |
| catch (IllegalStateException x) // should not happen |
| { |
| x.printStackTrace(System.err); |
| } |
| catch (LimitReachedException x) // idem |
| { |
| x.printStackTrace(System.err); |
| } |
| return result; |
| } |
| } |