libjava/classpath/gnu/javax/crypto/jce/prng/UMacRandomSpi.java

   1 /* UMacRandomSpi.java --
   2    Copyright (C) 2001, 2002, 2006  Free Software Foundation, Inc.
   3
   4 This file is a part of GNU Classpath.
   5
   6 GNU Classpath is free software; you can redistribute it and/or modify
   7 it under the terms of the GNU General Public License as published by
   8 the Free Software Foundation; either version 2 of the License, or (at
   9 your option) any later version.
  10
  11 GNU Classpath is distributed in the hope that it will be useful, but
  12 WITHOUT ANY WARRANTY; without even the implied warranty of
  13 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  14 General Public License for more details.
  15
  16 You should have received a copy of the GNU General Public License
  17 along with GNU Classpath; if not, write to the Free Software
  18 Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301
  19 USA
  20
  21 Linking this library statically or dynamically with other modules is
  22 making a combined work based on this library.  Thus, the terms and
  23 conditions of the GNU General Public License cover the whole
  24 combination.
  25
  26 As a special exception, the copyright holders of this library give you
  27 permission to link this library with independent modules to produce an
  28 executable, regardless of the license terms of these independent
  29 modules, and to copy and distribute the resulting executable under
  30 terms of your choice, provided that you also meet, for each linked
  31 independent module, the terms and conditions of the license of that
  32 module.  An independent module is a module which is not derived from
  33 or based on this library.  If you modify this library, you may extend
  34 this exception to your version of the library, but you are not
  35 obligated to do so.  If you do not wish to do so, delete this
  36 exception statement from your version.  */
  37
  38
  39 package gnu.javax.crypto.jce.prng;
  40
  41 import gnu.java.security.Configuration;
  42 import gnu.java.security.Registry;
  43 import gnu.java.security.prng.LimitReachedException;
  44 import gnu.java.security.jce.prng.SecureRandomAdapter;
  45 import gnu.javax.crypto.cipher.IBlockCipher;
  46 import gnu.javax.crypto.prng.UMacGenerator;
  47
  48 import java.security.SecureRandomSpi;
  49 import java.util.HashMap;
  50 import java.util.Random;
  51 import java.util.logging.Logger;
  52
  53 /**
  54  * An <em>Adapter</em> class around {@link UMacGenerator} to allow using this
  55  * algorithm as a JCE {@link java.security.SecureRandom}.
  56  */
  57 public class UMacRandomSpi
  58     extends SecureRandomSpi
  59 {
  60   private static final Logger log = Logger.getLogger(UMacRandomSpi.class.getName());
  61
  62   /** Class-wide prng to generate random material for the underlying prng. */
  63   private static final UMacGenerator prng; // blank final
  64   static
  65     {
  66       prng = new UMacGenerator();
  67       resetLocalPRNG();
  68     }
  69   // error messages
  70   private static final String MSG = "Exception while setting up a "
  71                                     + Registry.UMAC_PRNG + " SPI: ";
  72   private static final String RETRY = "Retry...";
  73   /** Our underlying prng instance. */
  74   private UMacGenerator adaptee = new UMacGenerator();
  75
  76   // default 0-arguments constructor
  77
  78   private static void resetLocalPRNG()
  79   {
  80     HashMap attributes = new HashMap();
  81     attributes.put(UMacGenerator.CIPHER, Registry.AES_CIPHER);
  82     byte[] key = new byte[128 / 8]; // AES default key size
  83     Random rand = new Random(System.currentTimeMillis());
  84     rand.nextBytes(key);
  85     attributes.put(IBlockCipher.KEY_MATERIAL, key);
  86     int index = rand.nextInt() & 0xFF;
  87     attributes.put(UMacGenerator.INDEX, Integer.valueOf(index));
  88     prng.setup(attributes);
  89   }
  90
  91   public byte[] engineGenerateSeed(int numBytes)
  92   {
  93     return SecureRandomAdapter.getSeed(numBytes);
  94   }
  95
  96   public void engineNextBytes(byte[] bytes)
  97   {
  98     if (! adaptee.isInitialised())
  99       engineSetSeed(engineGenerateSeed(32));
 100     while (true)
 101       {
 102         try
 103           {
 104             adaptee.nextBytes(bytes, 0, bytes.length);
 105             break;
 106           }
 107         catch (LimitReachedException x)
 108           { // reseed the generator
 109             resetLocalPRNG();
 110           }
 111       }
 112   }
 113
 114   public void engineSetSeed(byte[] seed)
 115   {
 116     // compute the total number of random bytes required to setup adaptee
 117     int materialLength = 0;
 118     materialLength += 16; // key material size
 119     materialLength++; // index size
 120     byte[] material = new byte[materialLength];
 121     // use as much as possible bytes from the seed
 122     int materialOffset = 0;
 123     int materialLeft = material.length;
 124     if (seed.length > 0)
 125       { // copy some bytes into key and update indices
 126         int lenToCopy = Math.min(materialLength, seed.length);
 127         System.arraycopy(seed, 0, material, 0, lenToCopy);
 128         materialOffset += lenToCopy;
 129         materialLeft -= lenToCopy;
 130       }
 131     if (materialOffset > 0) // generate the rest
 132       {
 133         while (true)
 134           {
 135             try
 136               {
 137                 prng.nextBytes(material, materialOffset, materialLeft);
 138                 break;
 139               }
 140             catch (IllegalStateException x) // should not happen
 141               {
 142                 throw new InternalError(MSG + String.valueOf(x));
 143               }
 144             catch (LimitReachedException x)
 145               {
 146                 if (Configuration.DEBUG)
 147                   {
 148                     log.fine(MSG + String.valueOf(x));
 149                     log.fine(RETRY);
 150                   }
 151               }
 152           }
 153       }
 154     // setup the underlying adaptee instance
 155     HashMap attributes = new HashMap();
 156     // use AES cipher with 128-bit block size
 157     attributes.put(UMacGenerator.CIPHER, Registry.AES_CIPHER);
 158     // specify the key
 159     byte[] key = new byte[16];
 160     System.arraycopy(material, 0, key, 0, 16);
 161     attributes.put(IBlockCipher.KEY_MATERIAL, key);
 162     // use a 1-byte index
 163     attributes.put(UMacGenerator.INDEX, Integer.valueOf(material[16] & 0xFF));
 164     adaptee.init(attributes);
 165   }
 166 }