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;
import org.bouncycastle.crypto.paddings.BlockCipherPadding;

standard CBC Block Cipher MAC - if no padding is specified the default of
pad of zeroes is used.
/**
 * standard CBC Block Cipher MAC - if no padding is specified the default of
 * pad of zeroes is used.
 */
public class CBCBlockCipherMac
    implements Mac
{
    private byte[]              mac;

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

    private int                 macSize;

    
create a standard MAC based on a CBC 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./**
     * create a standard MAC based on a CBC 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.
     */
    public CBCBlockCipherMac(
        BlockCipher     cipher)
    {
        this(cipher, (cipher.getBlockSize() * 8) / 2, null);
    }

    
create a standard MAC based on a CBC 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.
padding – the padding to be used to complete the last block./**
     * create a standard MAC based on a CBC 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.
     * @param padding the padding to be used to complete the last block.
     */
    public CBCBlockCipherMac(
        BlockCipher         cipher,
        BlockCipherPadding  padding)
    {
        this(cipher, (cipher.getBlockSize() * 8) / 2, padding);
    }

    
create a standard MAC based on a block cipher with the size of the
MAC been given in bits. This class uses CBC mode as the basis for the
MAC generation.

Note: the size of the MAC must be at least 24 bits (FIPS Publication 81),
or 16 bits if being used as a data authenticator (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./**
     * create a standard MAC based on a block cipher with the size of the
     * MAC been given in bits. This class uses CBC mode as the basis for the
     * MAC generation.
     * <p>
     * Note: the size of the MAC must be at least 24 bits (FIPS Publication 81),
     * or 16 bits if being used as a data authenticator (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.
     */
    public CBCBlockCipherMac(
        BlockCipher     cipher,
        int             macSizeInBits)
    {
        this(cipher, macSizeInBits, null);
    }

    
create a standard MAC based on a block cipher with the size of the
MAC been given in bits. This class uses CBC mode as the basis for the
MAC generation.

Note: the size of the MAC must be at least 24 bits (FIPS Publication 81),
or 16 bits if being used as a data authenticator (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.
padding – the padding to be used to complete the last block./**
     * create a standard MAC based on a block cipher with the size of the
     * MAC been given in bits. This class uses CBC mode as the basis for the
     * MAC generation.
     * <p>
     * Note: the size of the MAC must be at least 24 bits (FIPS Publication 81),
     * or 16 bits if being used as a data authenticator (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.
     * @param padding the padding to be used to complete the last block.
     */
    public CBCBlockCipherMac(
        BlockCipher         cipher,
        int                 macSizeInBits,
        BlockCipherPadding  padding)
    {
        if ((macSizeInBits % 8) != 0)
        {
            throw new IllegalArgumentException("MAC size must be multiple of 8");
        }

        this.cipher = new CBCBlockCipher(cipher);
        this.padding = padding;
        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 gapLen = blockSize - bufOff;

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

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

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

            while (len > blockSize)
            {
                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();

        if (padding == null)
        {
            //
            // pad with zeroes
            //
            while (bufOff < blockSize)
            {
                buf[bufOff] = 0;
                bufOff++;
            }
        }
        else
        {
            if (bufOff == blockSize)
            {
                cipher.processBlock(buf, 0, mac, 0);
                bufOff = 0;
            }

            padding.addPadding(buf, 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();
    }
}