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/* ICMRandomSpi.java --

   Copyright (C) 2001, 2002, 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.jce.prng;

import gnu.java.security.Configuration;

import gnu.java.security.Registry;

import gnu.java.security.jce.prng.SecureRandomAdapter;

import gnu.java.security.prng.LimitReachedException;

import gnu.javax.crypto.cipher.IBlockCipher;

import gnu.javax.crypto.prng.ICMGenerator;

import java.math.BigInteger;

import java.security.SecureRandomSpi;

import java.util.HashMap;

import java.util.Random;

import java.util.logging.Logger;

/**

 * An <em>Adapter</em> class around {@link ICMGenerator} to allow using this

 * algorithm as a JCE {@link java.security.SecureRandom}.

 */

public class ICMRandomSpi

    extends SecureRandomSpi

{

  private static final Logger log = Logger.getLogger(ICMRandomSpi.class.getName());

  /** Class-wide prng to generate random material for the underlying prng. */

  private static final ICMGenerator prng; // blank final

  static

    {

      prng = new ICMGenerator();

      resetLocalPRNG();

    }

  // error messages

  private static final String MSG = "Exception while setting up an "

                                    + Registry.ICM_PRNG + " SPI: ";

  private static final String RETRY = "Retry...";

  private static final String LIMIT_REACHED_MSG = "Limit reached: ";

  private static final String RESEED = "Re-seed...";

  /** Our underlying prng instance. */

  private ICMGenerator adaptee = new ICMGenerator();

  // default 0-arguments constructor

  private static void resetLocalPRNG()

  {

    if (Configuration.DEBUG)

      log.entering(ICMRandomSpi.class.getName(), "resetLocalPRNG");

    HashMap attributes = new HashMap();

    attributes.put(ICMGenerator.CIPHER, Registry.AES_CIPHER);

    byte[] key = new byte[128 / 8]; // AES default key size

    Random rand = new Random(System.currentTimeMillis());

    rand.nextBytes(key);

    attributes.put(IBlockCipher.KEY_MATERIAL, key);

    int aesBlockSize = 128 / 8; // AES block size in bytes

    byte[] offset = new byte[aesBlockSize];

    rand.nextBytes(offset);

    attributes.put(ICMGenerator.OFFSET, offset);

    int ndxLen = 0; // the segment length

    // choose a random value between 1 and aesBlockSize / 2

    int limit = aesBlockSize / 2;

    while (ndxLen < 1 || ndxLen > limit)

      ndxLen = rand.nextInt(limit + 1);

    attributes.put(ICMGenerator.SEGMENT_INDEX_LENGTH, Integer.valueOf(ndxLen));

    byte[] index = new byte[ndxLen];

    rand.nextBytes(index);

    attributes.put(ICMGenerator.SEGMENT_INDEX, new BigInteger(1, index));

    prng.setup(attributes);

    if (Configuration.DEBUG)

      log.exiting(ICMRandomSpi.class.getName(), "resetLocalPRNG");

  }

  public byte[] engineGenerateSeed(int numBytes)

  {

    return SecureRandomAdapter.getSeed(numBytes);

  }

  public void engineNextBytes(byte[] bytes)

  {

    if (Configuration.DEBUG)

      log.entering(this.getClass().getName(), "engineNextBytes");

    if (! adaptee.isInitialised())

      this.engineSetSeed(engineGenerateSeed(32));

    while (true)

      {

        try

          {

            adaptee.nextBytes(bytes, 0, bytes.length);

            break;

          }

        catch (LimitReachedException x)

          { // reseed the generator

            if (Configuration.DEBUG)

              {

                log.fine(LIMIT_REACHED_MSG + String.valueOf(x));

                log.fine(RESEED);

              }

            resetLocalPRNG();

          }

      }

    if (Configuration.DEBUG)

      log.exiting(this.getClass().getName(), "engineNextBytes");

  }

  public void engineSetSeed(byte[] seed)

  {

    if (Configuration.DEBUG)

      log.entering(this.getClass().getName(), "engineSetSeed");

    // compute the total number of random bytes required to setup adaptee

    int materialLength = 0;

    materialLength += 16; // key material size

    materialLength += 16; // offset size

    materialLength += 8; // index size == half of an AES block

    byte[] material = new byte[materialLength];

    // use as much as possible bytes from the seed

    int materialOffset = 0;

    int materialLeft = material.length;

    if (seed.length > 0)

      { // copy some bytes into key and update indices

        int lenToCopy = Math.min(materialLength, seed.length);

        System.arraycopy(seed, 0, material, 0, lenToCopy);

        materialOffset += lenToCopy;

        materialLeft -= lenToCopy;

      }

    if (materialOffset > 0) // generate the rest

      {

        while (true)

          {

            try

              {

                prng.nextBytes(material, materialOffset, materialLeft);

                break;

              }

            catch (IllegalStateException x)

              { // should not happen

                throw new InternalError(MSG + String.valueOf(x));

              }

            catch (LimitReachedException x)

              {

                if (Configuration.DEBUG)

                  {

                    log.fine(MSG + String.valueOf(x));

                    log.fine(RETRY);

                  }

              }

          }

      }

    // setup the underlying adaptee instance

    HashMap attributes = new HashMap();

    // use AES cipher with 128-bit block size

    attributes.put(ICMGenerator.CIPHER, Registry.AES_CIPHER);

    // use an index the size of quarter of an AES block

    attributes.put(ICMGenerator.SEGMENT_INDEX_LENGTH, Integer.valueOf(4));

    // specify the key

    byte[] key = new byte[16];

    System.arraycopy(material, 0, key, 0, 16);

    attributes.put(IBlockCipher.KEY_MATERIAL, key);

    // specify the offset

    byte[] offset = new byte[16];

    System.arraycopy(material, 16, offset, 0, 16);

    attributes.put(ICMGenerator.OFFSET, offset);

    // specify the index

    byte[] index = new byte[4];

    System.arraycopy(material, 32, index, 0, 4);

    attributes.put(ICMGenerator.SEGMENT_INDEX, new BigInteger(1, index));

    adaptee.init(attributes);

    if (Configuration.DEBUG)

      log.exiting(this.getClass().getName(), "engineSetSeed");

  }

}