package org.bouncycastle.crypto.macs;

import org.bouncycastle.crypto.BlockCipher;
import org.bouncycastle.crypto.CipherParameters;
import org.bouncycastle.crypto.Mac;
import org.bouncycastle.crypto.modes.CBCBlockCipher;

public class BlockCipherMac
    implements Mac
{
    private byte[]          mac;

    private byte[]          buf;
    private int             bufOff;
    private BlockCipher     cipher;

    private int             macSize;

    
create a standard MAC based on a block cipher. This will produce an
authentication code half the length of the block size of the cipher.
Params:
cipher – the cipher to be used as the basis of the MAC generation.
Deprecated:
use CBCBlockCipherMac/**
     * create a standard MAC based on a block cipher. This will produce an
     * authentication code half the length of the block size of the cipher.
     *
     * @param cipher the cipher to be used as the basis of the MAC generation.
     * @deprecated use CBCBlockCipherMac
     */
    public BlockCipherMac(
        BlockCipher     cipher)
    {
        this(cipher, (cipher.getBlockSize() * 8) / 2);
    }

    
create a standard MAC based on a block cipher with the size of the
MAC been given in bits.

Note: the size of the MAC must be at least 16 bits (FIPS Publication 113),
and in general should be less than the size of the block cipher as it reduces
the chance of an exhaustive attack (see Handbook of Applied Cryptography).
Params:
cipher – the cipher to be used as the basis of the MAC generation.
macSizeInBits – the size of the MAC in bits, must be a multiple of 8.
Deprecated:
use CBCBlockCipherMac/**
     * create a standard MAC based on a block cipher with the size of the
     * MAC been given in bits.
     * <p>
     * Note: the size of the MAC must be at least 16 bits (FIPS Publication 113),
     * and in general should be less than the size of the block cipher as it reduces
     * the chance of an exhaustive attack (see Handbook of Applied Cryptography).
     *
     * @param cipher the cipher to be used as the basis of the MAC generation.
     * @param macSizeInBits the size of the MAC in bits, must be a multiple of 8.
     * @deprecated use CBCBlockCipherMac
     */
    public BlockCipherMac(
        BlockCipher     cipher,
        int             macSizeInBits)
    {
        if ((macSizeInBits % 8) != 0)
        {
            throw new IllegalArgumentException("MAC size must be multiple of 8");
        }

        this.cipher = new CBCBlockCipher(cipher);
        this.macSize = macSizeInBits / 8;

        mac = new byte[cipher.getBlockSize()];

        buf = new byte[cipher.getBlockSize()];
        bufOff = 0;
    }

    public String getAlgorithmName()
    {
        return cipher.getAlgorithmName();
    }

    public void init(
        CipherParameters    params)
    {
        reset();

        cipher.init(true, params);
    }

    public int getMacSize()
    {
        return macSize;
    }

    public void update(
        byte        in)
    {
        if (bufOff == buf.length)
        {
            cipher.processBlock(buf, 0, mac, 0);
            bufOff = 0;
        }

        buf[bufOff++] = in;
    }

    public void update(
        byte[]      in,
        int         inOff,
        int         len)
    {
        if (len < 0)
        {
            throw new IllegalArgumentException("Can't have a negative input length!");
        }

        int blockSize = cipher.getBlockSize();
        int resultLen = 0;
        int gapLen = blockSize - bufOff;

        if (len > gapLen)
        {
            System.arraycopy(in, inOff, buf, bufOff, gapLen);

            resultLen += cipher.processBlock(buf, 0, mac, 0);

            bufOff = 0;
            len -= gapLen;
            inOff += gapLen;

            while (len > blockSize)
            {
                resultLen += cipher.processBlock(in, inOff, mac, 0);

                len -= blockSize;
                inOff += blockSize;
            }
        }

        System.arraycopy(in, inOff, buf, bufOff, len);

        bufOff += len;
    }

    public int doFinal(
        byte[]  out,
        int     outOff)
    {
        int blockSize = cipher.getBlockSize();

        //
        // pad with zeroes
        //
        while (bufOff < blockSize)
        {
            buf[bufOff] = 0;
            bufOff++;
        }

        cipher.processBlock(buf, 0, mac, 0);

        System.arraycopy(mac, 0, out, outOff, macSize);

        reset();

        return macSize;
    }

    
Reset the mac generator.
/**
     * Reset the mac generator.
     */
    public void reset()
    {
        /*
         * clean the buffer.
         */
        for (int i = 0; i < buf.length; i++)
        {
            buf[i] = 0;
        }

        bufOff = 0;

        /*
         * reset the underlying cipher.
         */
        cipher.reset();
    }
}