/* BaseMode.java -- 
   Copyright (C) 2001, 2002, 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
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General Public License for more details.

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Linking this library statically or dynamically with other modules is
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permission to link this library with independent modules to produce an
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package gnu.javax.crypto.mode;

import gnu.javax.crypto.cipher.IBlockCipher;

import java.security.InvalidKeyException;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.Collections;
import java.util.HashMap;
import java.util.Iterator;
import java.util.Map;

/**
 * A basic abstract class to facilitate implementing block cipher modes of
 * operations.
 */
public abstract class BaseMode
    implements IMode
{
  /** The canonical name prefix of this mode. */
  protected String name;
  /** The state indicator of this instance. */
  protected int state;
  /** The underlying block cipher implementation. */
  protected IBlockCipher cipher;
  /** The block size, in bytes, to operate the underlying block cipher in. */
  protected int cipherBlockSize;
  /** The block size, in bytes, in which to operate the mode instance. */
  protected int modeBlockSize;
  /** The initialisation vector value. */
  protected byte[] iv;
  /** The instance lock. */
  protected Object lock = new Object();

  /**
   * Trivial constructor for use by concrete subclasses.
   * 
   * @param name the canonical name prefix of this mode.
   * @param underlyingCipher the implementation of the underlying cipher.
   * @param cipherBlockSize the block size, in bytes, in which to operate the
   *          underlying cipher.
   */
  protected BaseMode(String name, IBlockCipher underlyingCipher,
                     int cipherBlockSize)
  {
    super();

    this.name = name;
    this.cipher = underlyingCipher;
    this.cipherBlockSize = cipherBlockSize;
    state = -1;
  }

  public void update(byte[] in, int inOffset, byte[] out, int outOffset)
      throws IllegalStateException
  {
    synchronized (lock)
      {
        switch (state)
          {
          case ENCRYPTION:
            encryptBlock(in, inOffset, out, outOffset);
            break;
          case DECRYPTION:
            decryptBlock(in, inOffset, out, outOffset);
            break;
          default:
            throw new IllegalStateException();
          }
      }
  }

  public String name()
  {
    return new StringBuffer(name).append('(').append(cipher.name()).append(')')
        .toString();
  }

  /**
   * Returns the default value, in bytes, of the mode's block size. This value
   * is part of the construction arguments passed to the Factory methods in
   * {@link ModeFactory}. Unless changed by an invocation of any of the
   * <code>init()</code> methods, a <i>Mode</i> instance would operate with
   * the same block size as its underlying block cipher. As mentioned earlier,
   * the block size of the underlying block cipher itself is specified in one of
   * the method(s) available in the factory class.
   * 
   * @return the default value, in bytes, of the mode's block size.
   * @see ModeFactory
   */
  public int defaultBlockSize()
  {
    return cipherBlockSize;
  }

  /**
   * Returns the default value, in bytes, of the underlying block cipher key
   * size.
   * 
   * @return the default value, in bytes, of the underlying cipher's key size.
   */
  public int defaultKeySize()
  {
    return cipher.defaultKeySize();
  }

  /**
   * Returns an {@link Iterator} over the supported block sizes. Each element
   * returned by this object is an {@link Integer}.
   * <p>
   * The default behaviour is to return an iterator with just one value, which
   * is that currently configured for the underlying block cipher. Concrete
   * implementations may override this behaviour to signal their ability to
   * support other values.
   * 
   * @return an {@link Iterator} over the supported block sizes.
   */
  public Iterator blockSizes()
  {
    ArrayList al = new ArrayList();
    al.add(Integer.valueOf(cipherBlockSize));
    return Collections.unmodifiableList(al).iterator();
  }

  /**
   * Returns an {@link Iterator} over the supported underlying block cipher key
   * sizes. Each element returned by this object is an instance of
   * {@link Integer}.
   * 
   * @return an {@link Iterator} over the supported key sizes.
   */
  public Iterator keySizes()
  {
    return cipher.keySizes();
  }

  public void init(Map attributes) throws InvalidKeyException,
      IllegalStateException
  {
    synchronized (lock)
      {
        if (state != -1)
          throw new IllegalStateException();
        Integer want = (Integer) attributes.get(STATE);
        if (want != null)
          {
            switch (want.intValue())
              {
              case ENCRYPTION:
                state = ENCRYPTION;
                break;
              case DECRYPTION:
                state = DECRYPTION;
                break;
              default:
                throw new IllegalArgumentException();
              }
          }
        Integer bs = (Integer) attributes.get(MODE_BLOCK_SIZE);
        modeBlockSize = (bs == null ? cipherBlockSize : bs.intValue());
        byte[] iv = (byte[]) attributes.get(IV);
        if (iv != null)
          this.iv = (byte[]) iv.clone();
        else
          this.iv = new byte[modeBlockSize];
        cipher.init(attributes);
        setup();
      }
  }

  public int currentBlockSize()
  {
    if (state == -1)
      throw new IllegalStateException();
    return modeBlockSize;
  }

  public void reset()
  {
    synchronized (lock)
      {
        state = -1;
        iv = null;
        cipher.reset();
        teardown();
      }
  }

  public boolean selfTest()
  {
    int ks;
    Iterator bit;
    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;
  }

  public abstract Object clone();

  /** The initialisation phase of the concrete mode implementation. */
  public abstract void setup();

  /** The termination phase of the concrete mode implementation. */
  public abstract void teardown();

  public abstract void encryptBlock(byte[] in, int i, byte[] out, int o);

  public abstract void decryptBlock(byte[] in, int i, byte[] out, int o);

  private boolean testSymmetry(int ks, int bs)
  {
    try
      {
        IMode mode = (IMode) this.clone();
        byte[] iv = new byte[cipherBlockSize]; // all zeroes
        byte[] k = new byte[ks];
        int i;
        for (i = 0; i < ks; i++)
          k[i] = (byte) i;
        int blockCount = 5;
        int limit = blockCount * bs;
        byte[] pt = new byte[limit];
        for (i = 0; i < limit; i++)
          pt[i] = (byte) i;
        byte[] ct = new byte[limit];
        byte[] cpt = new byte[limit];
        Map map = new HashMap();
        map.put(KEY_MATERIAL, k);
        map.put(CIPHER_BLOCK_SIZE, Integer.valueOf(cipherBlockSize));
        map.put(STATE, Integer.valueOf(ENCRYPTION));
        map.put(IV, iv);
        map.put(MODE_BLOCK_SIZE, Integer.valueOf(bs));
        mode.reset();
        mode.init(map);
        for (i = 0; i < blockCount; i++)
          mode.update(pt, i * bs, ct, i * bs);
        mode.reset();
        map.put(STATE, Integer.valueOf(DECRYPTION));
        mode.init(map);
        for (i = 0; i < blockCount; i++)
          mode.update(ct, i * bs, cpt, i * bs);
        return Arrays.equals(pt, cpt);
      }
    catch (Exception x)
      {
        x.printStackTrace(System.err);
        return false;
      }
  }
}