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/* OMAC.java --

   Copyright (C) 2004, 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.mac;

import gnu.java.security.Configuration;

import gnu.java.security.Registry;

import gnu.java.security.util.Util;

import gnu.javax.crypto.cipher.CipherFactory;

import gnu.javax.crypto.cipher.IBlockCipher;

import gnu.javax.crypto.mode.IMode;

import java.security.InvalidKeyException;

import java.util.Arrays;

import java.util.HashMap;

import java.util.Map;

import java.util.logging.Logger;

/**

 * The One-Key CBC MAC, OMAC. This message authentication code is based on a

 * block cipher in CBC mode.

 * <p>

 * References:

 * <ol>

 * <li>Tetsu Iwata and Kaoru Kurosawa, <i><a

 * href="http://crypt.cis.ibaraki.ac.jp/omac/docs/omac.pdf">OMAC: One-Key CBC

 * MAC</a></i>.</li>

 * </ol>

 */

public class OMAC

    implements IMac

{

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

  private static final byte C1 = (byte) 0x87;

  private static final byte C2 = 0x1b;

  // Test key for OMAC-AES-128

  private static final byte[] KEY0 =

      Util.toBytesFromString("2b7e151628aed2a6abf7158809cf4f3c");

  // Test MAC for zero-length input.

  private static final byte[] DIGEST0 =

      Util.toBytesFromString("bb1d6929e95937287fa37d129b756746");

  private static Boolean valid;

  private final IBlockCipher cipher;

  private final String name;

  private IMode mode;

  private int blockSize;

  private int outputSize;

  private byte[] Lu, Lu2;

  private byte[] M;

  private byte[] Y;

  private boolean init;

  private int index;

  public OMAC(IBlockCipher cipher)

  {

    this.cipher = cipher;

    this.name = "OMAC-" + cipher.name();

  }

  public Object clone()

  {

    return new OMAC(cipher);

  }

  public String name()

  {

    return name;

  }

  public int macSize()

  {

    return outputSize;

  }

  public void init(Map attrib) throws InvalidKeyException

  {

    HashMap attrib2 = new HashMap();

    attrib2.put(IBlockCipher.KEY_MATERIAL, attrib.get(MAC_KEY_MATERIAL));

    cipher.reset();

    cipher.init(attrib2);

    blockSize = cipher.currentBlockSize();

    Integer os = (Integer) attrib.get(TRUNCATED_SIZE);

    if (os != null)

      {

        outputSize = os.intValue();

        if (outputSize < 0 || outputSize > blockSize)

          throw new IllegalArgumentException("truncated size out of range");

      }

    else

      outputSize = blockSize;

    byte[] L = new byte[blockSize];

    cipher.encryptBlock(L, 0, L, 0);

    if (Configuration.DEBUG)

      log.fine("L = " + Util.toString(L).toLowerCase());

    if (Lu != null)

      {

        Arrays.fill(Lu, (byte) 0);

        if (Lu.length != blockSize)

          Lu = new byte[blockSize];

      }

    else

      Lu = new byte[blockSize];

    if (Lu2 != null)

      {

        Arrays.fill(Lu2, (byte) 0);

        if (Lu2.length != blockSize)

          Lu2 = new byte[blockSize];

      }

    else

      Lu2 = new byte[blockSize];

    boolean msb = (L[0] & 0x80) != 0;

    for (int i = 0; i < blockSize; i++)

      {

        Lu[i] = (byte)(L[i] << 1 & 0xFF);

        if (i + 1 < blockSize)

          Lu[i] |= (byte)((L[i + 1] & 0x80) >> 7);

      }

    if (msb)

      {

        if (blockSize == 16)

          Lu[Lu.length - 1] ^= C1;

        else if (blockSize == 8)

          Lu[Lu.length - 1] ^= C2;

        else

          throw new IllegalArgumentException("unsupported cipher block size: "

                                             + blockSize);

      }

    if (Configuration.DEBUG)

      log.fine("Lu = " + Util.toString(Lu).toLowerCase());

    msb = (Lu[0] & 0x80) != 0;

    for (int i = 0; i < blockSize; i++)

      {

        Lu2[i] = (byte)(Lu[i] << 1 & 0xFF);

        if (i + 1 < blockSize)

          Lu2[i] |= (byte)((Lu[i + 1] & 0x80) >> 7);

      }

    if (msb)

      {

        if (blockSize == 16)

          Lu2[Lu2.length - 1] ^= C1;

        else

          Lu2[Lu2.length - 1] ^= C2;

      }

    if (Configuration.DEBUG)

      log.fine("Lu2 = " + Util.toString(Lu2).toLowerCase());

    if (M != null)

      {

        Arrays.fill(M, (byte) 0);

        if (M.length != blockSize)

          M = new byte[blockSize];

      }

    else

      M = new byte[blockSize];

    if (Y != null)

      {

        Arrays.fill(Y, (byte) 0);

        if (Y.length != blockSize)

          Y = new byte[blockSize];

      }

    else

      Y = new byte[blockSize];

    index = 0;

    init = true;

  }

  public void update(byte b)

  {

    if (! init)

      throw new IllegalStateException("not initialized");

    if (index == M.length)

      {

        process();

        index = 0;

      }

    M[index++] = b;

  }

  public void update(byte[] buf, int off, int len)

  {

    if (! init)

      throw new IllegalStateException("not initialized");

    if (off < 0 || len < 0 || off + len > buf.length)

      throw new IndexOutOfBoundsException("size=" + buf.length + "; off=" + off

                                          + "; len=" + len);

    for (int i = 0; i < len;)

      {

        if (index == blockSize)

          {

            process();

            index = 0;

          }

        int count = Math.min(blockSize - index, len - i);

        System.arraycopy(buf, off + i, M, index, count);

        index += count;

        i += count;

      }

  }

  public byte[] digest()

  {

    byte[] b = new byte[outputSize];

    digest(b, 0);

    return b;

  }

  public void digest(byte[] out, int off)

  {

    if (! init)

      throw new IllegalStateException("not initialized");

    if (off < 0 || off + outputSize > out.length)

      throw new IndexOutOfBoundsException("size=" + out.length + "; off=" + off

                                          + "; len=" + outputSize);

    byte[] T = new byte[blockSize];

    byte[] L = Lu;

    if (index < blockSize)

      {

        M[index++] = (byte) 0x80;

        while (index < blockSize)

          M[index++] = 0;

        L = Lu2;

      }

    for (int i = 0; i < blockSize; i++)

      T[i] = (byte)(M[i] ^ Y[i] ^ L[i]);

    cipher.encryptBlock(T, 0, T, 0);

    System.arraycopy(T, 0, out, off, outputSize);

    reset();

  }

  public void reset()

  {

    index = 0;

    if (Y != null)

      Arrays.fill(Y, (byte) 0);

    if (M != null)

      Arrays.fill(M, (byte) 0);

  }

  public boolean selfTest()

  {

    OMAC mac = new OMAC(CipherFactory.getInstance(Registry.AES_CIPHER));

    mac.reset();

    Map attr = new HashMap();

    attr.put(MAC_KEY_MATERIAL, KEY0);

    byte[] digest = null;

    try

      {

        mac.init(attr);

        digest = mac.digest();

      }

    catch (Exception x)

      {

        return false;

      }

    if (digest == null)

      return false;

    return Arrays.equals(DIGEST0, digest);

  }

  private void process()

  {

    for (int i = 0; i < blockSize; i++)

      M[i] = (byte)(M[i] ^ Y[i]);

    cipher.encryptBlock(M, 0, Y, 0);

  }

}