/* BaseCipher.java --
   Copyright (C) 2001, 2002, 2003, 2006, 2010 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.

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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
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package gnu.javax.crypto.cipher;

import gnu.java.lang.CPStringBuilder;

import gnu.java.security.Configuration;

import java.security.InvalidKeyException;
import java.util.Arrays;
import java.util.Iterator;
import java.util.Map;
import java.util.logging.Level;
import java.util.logging.Logger;

/**
 * A basic abstract class to facilitate implementing symmetric key block
 * ciphers.
 */
public abstract class BaseCipher
    implements IBlockCipher, IBlockCipherSpi
{
  private static final Logger log = Configuration.DEBUG ?
                        Logger.getLogger(BaseCipher.class.getName()) : null;
  /** The canonical name prefix of the cipher. */
  protected String name;
  /** The default block size, in bytes. */
  protected int defaultBlockSize;
  /** The default key size, in bytes. */
  protected int defaultKeySize;
  /** The current block size, in bytes. */
  protected int currentBlockSize;
  /** The session key for this instance. */
  protected transient Object currentKey;
  /** The instance lock. */
  protected Object lock = new Object();

  /**
   * Trivial constructor for use by concrete subclasses.
   *
   * @param name the canonical name prefix of this instance.
   * @param defaultBlockSize the default block size in bytes.
   * @param defaultKeySize the default key size in bytes.
   */
  protected BaseCipher(String name, int defaultBlockSize, int defaultKeySize)
  {
    super();

    this.name = name;
    this.defaultBlockSize = defaultBlockSize;
    this.defaultKeySize = defaultKeySize;
  }

  public abstract Object clone();

  public String name()
  {
    CPStringBuilder sb = new CPStringBuilder(name).append('-');
    if (currentKey == null)
      sb.append(String.valueOf(8 * defaultBlockSize));
    else
      sb.append(String.valueOf(8 * currentBlockSize));
    return sb.toString();
  }

  public int defaultBlockSize()
  {
    return defaultBlockSize;
  }

  public int defaultKeySize()
  {
    return defaultKeySize;
  }

  public void init(Map attributes) throws InvalidKeyException
  {
    synchronized (lock)
      {
        if (currentKey != null)
          throw new IllegalStateException();
        Integer bs = (Integer) attributes.get(CIPHER_BLOCK_SIZE);
        if (bs == null) // no block size was specified
          {
            if (currentBlockSize == 0) // happy birthday
              currentBlockSize = defaultBlockSize;
            // else it's a clone. use as is
          }
        else
          {
            currentBlockSize = bs.intValue();
            // ensure that value is valid
            Iterator it;
            boolean ok = false;
            for (it = blockSizes(); it.hasNext();)
              {
                ok = (currentBlockSize == ((Integer) it.next()).intValue());
                if (ok)
                  break;
              }
            if (! ok)
              throw new IllegalArgumentException(IBlockCipher.CIPHER_BLOCK_SIZE);
          }
        byte[] k = (byte[]) attributes.get(KEY_MATERIAL);
        currentKey = makeKey(k, currentBlockSize);
      }
  }

  public int currentBlockSize()
  {
    if (currentKey == null)
      throw new IllegalStateException();
    return currentBlockSize;
  }

  public void reset()
  {
    synchronized (lock)
      {
        currentKey = null;
      }
  }

  public void encryptBlock(byte[] in, int inOffset, byte[] out, int outOffset)
      throws IllegalStateException
  {
    synchronized (lock)
      {
        if (currentKey == null)
          throw new IllegalStateException();
        encrypt(in, inOffset, out, outOffset, currentKey, currentBlockSize);
      }
  }

  public void decryptBlock(byte[] in, int inOffset, byte[] out, int outOffset)
      throws IllegalStateException
  {
    synchronized (lock)
      {
        if (currentKey == null)
          throw new IllegalStateException();
        decrypt(in, inOffset, out, outOffset, currentKey, currentBlockSize);
      }
  }

  public boolean selfTest()
  {
    int ks;
    Iterator bit;
    // do symmetry tests for all block-size/key-size combos
    for (Iterator kit = keySizes(); kit.hasNext();)
      {
        ks = ((Integer) kit.next()).intValue();
        for (bit = blockSizes(); bit.hasNext();)
          if (! testSymmetry(ks, ((Integer) bit.next()).intValue()))
            return false;
      }
    return true;
  }

  private boolean testSymmetry(int ks, int bs)
  {
    try
      {
        byte[] kb = new byte[ks];
        byte[] pt = new byte[bs];
        byte[] ct = new byte[bs];
        byte[] cpt = new byte[bs];
        int i;
        for (i = 0; i < ks; i++)
          kb[i] = (byte) i;
        for (i = 0; i < bs; i++)
          pt[i] = (byte) i;
        Object k = makeKey(kb, bs);
        encrypt(pt, 0, ct, 0, k, bs);
        decrypt(ct, 0, cpt, 0, k, bs);
        return Arrays.equals(pt, cpt);
      }
    catch (Exception x)
      {
        if (Configuration.DEBUG)
          log.log(Level.FINE, "Exception in testSymmetry() for " + name(), x);
        return false;
      }
  }

  protected boolean testKat(byte[] kb, byte[] ct)
  {
    return testKat(kb, ct, new byte[ct.length]); // all-zero plaintext
  }

  protected boolean testKat(byte[] kb, byte[] ct, byte[] pt)
  {
    try
      {
        int bs = pt.length;
        byte[] t = new byte[bs];
        Object k = makeKey(kb, bs);
        // test encryption
        encrypt(pt, 0, t, 0, k, bs);
        if (! Arrays.equals(t, ct))
          return false;
        // test decryption
        decrypt(t, 0, t, 0, k, bs);
        return Arrays.equals(t, pt);
      }
    catch (Exception x)
      {
        if (Configuration.DEBUG)
          log.log(Level.FINE, "Exception in testKat() for " + name(), x);
        return false;
      }
  }
}