package org.bouncycastle.crypto.macs;

import org.bouncycastle.crypto.BlockCipher;
import org.bouncycastle.crypto.CipherParameters;
import org.bouncycastle.crypto.Mac;
import org.bouncycastle.crypto.engines.DESEngine;
import org.bouncycastle.crypto.modes.CBCBlockCipher;
import org.bouncycastle.crypto.paddings.BlockCipherPadding;
import org.bouncycastle.crypto.params.KeyParameter;
import org.bouncycastle.crypto.params.ParametersWithIV;

DES based CBC Block Cipher MAC according to ISO9797, algorithm 3 (ANSI X9.19 Retail MAC)
This could as well be derived from CBCBlockCipherMac, but then the property mac in the base
class must be changed to protected  
/**
 * DES based CBC Block Cipher MAC according to ISO9797, algorithm 3 (ANSI X9.19 Retail MAC)
 *
 * This could as well be derived from CBCBlockCipherMac, but then the property mac in the base
 * class must be changed to protected  
 */

public class ISO9797Alg3Mac 
    implements Mac 
{
    private byte[]              mac;
    
    private byte[]              buf;
    private int                 bufOff;
    private BlockCipher         cipher;
    private BlockCipherPadding  padding;
    
    private int                 macSize;
    private KeyParameter        lastKey2;
    private KeyParameter        lastKey3;
    
    
create a Retail-MAC based on a CBC block cipher. This will produce an
authentication code of the length of the block size of the cipher.
Params:
cipher – the cipher to be used as the basis of the MAC generation. This must
be DESEngine./**
     * create a Retail-MAC based on a CBC block cipher. This will produce an
     * authentication code of the length of the block size of the cipher.
     *
     * @param cipher the cipher to be used as the basis of the MAC generation. This must
     * be DESEngine.
     */
    public ISO9797Alg3Mac(
            BlockCipher     cipher)
    {
        this(cipher, cipher.getBlockSize() * 8, null);
    }
    
    
create a Retail-MAC based on a CBC block cipher. This will produce an
authentication code of 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 Retail-MAC based on a CBC block cipher. This will produce an
     * authentication code of 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 ISO9797Alg3Mac(
        BlockCipher         cipher,
        BlockCipherPadding  padding)
    {
        this(cipher, cipher.getBlockSize() * 8, padding);
    }

    
create a Retail-MAC based on a block cipher with the size of the
MAC been given in bits. This class uses single DES 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 Retail-MAC based on a block cipher with the size of the
     * MAC been given in bits. This class uses single DES 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 ISO9797Alg3Mac(
        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 single DES CBC mode as the basis for the
MAC generation. The final block is decrypted and then encrypted using the
middle and right part of the key.

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 single DES CBC mode as the basis for the
     * MAC generation. The final block is decrypted and then encrypted using the
     * middle and right part of the key.
     * <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 ISO9797Alg3Mac(
        BlockCipher         cipher,
        int                 macSizeInBits,
        BlockCipherPadding  padding)
    {
        if ((macSizeInBits % 8) != 0)
        {
            throw new IllegalArgumentException("MAC size must be multiple of 8");
        }

        if (!(cipher instanceof DESEngine))
        {
            throw new IllegalArgumentException("cipher must be instance of DESEngine");
        }

        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 "ISO9797Alg3";
    }

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

        if (!(params instanceof KeyParameter || params instanceof ParametersWithIV))
        {
            throw new IllegalArgumentException(
                    "params must be an instance of KeyParameter or ParametersWithIV");
        }

        // KeyParameter must contain a double or triple length DES key,
        // however the underlying cipher is a single DES. The middle and
        // right key are used only in the final step.

        KeyParameter kp;

        if (params instanceof KeyParameter)
        {
            kp = (KeyParameter)params;
        }
        else
        {
            kp = (KeyParameter)((ParametersWithIV)params).getParameters();
        }

        KeyParameter key1;
        byte[] keyvalue = kp.getKey();

        if (keyvalue.length == 16)
        { // Double length DES key
            key1 = new KeyParameter(keyvalue, 0, 8);
            this.lastKey2 = new KeyParameter(keyvalue, 8, 8);
            this.lastKey3 = key1;
        }
        else if (keyvalue.length == 24)
        { // Triple length DES key
            key1 = new KeyParameter(keyvalue, 0, 8);
            this.lastKey2 = new KeyParameter(keyvalue, 8, 8);
            this.lastKey3 = new KeyParameter(keyvalue, 16, 8);
        }
        else
        {
            throw new IllegalArgumentException(
                    "Key must be either 112 or 168 bit long");
        }

        if (params instanceof ParametersWithIV)
        {
            cipher.init(true, new ParametersWithIV(key1, ((ParametersWithIV)params).getIV()));
        }
        else
        {
            cipher.init(true, key1);
        }
    }
    
    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();
        
        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);

        // Added to code from base class
        DESEngine deseng = new DESEngine();
        
        deseng.init(false, this.lastKey2);
        deseng.processBlock(mac, 0, mac, 0);
        
        deseng.init(true, this.lastKey3);
        deseng.processBlock(mac, 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();
    }
}