package org.bouncycastle.crypto.macs;

import org.bouncycastle.crypto.BlockCipher;
import org.bouncycastle.crypto.CipherParameters;
import org.bouncycastle.crypto.DataLengthException;
import org.bouncycastle.crypto.Mac;
import org.bouncycastle.crypto.OutputLengthException;
import org.bouncycastle.crypto.paddings.BlockCipherPadding;
import org.bouncycastle.crypto.params.ParametersWithIV;

implements a Cipher-FeedBack (CFB) mode on top of a simple cipher.
/**
 * implements a Cipher-FeedBack (CFB) mode on top of a simple cipher.
 */
class MacCFBBlockCipher
{
    private byte[]          IV;
    private byte[]          cfbV;
    private byte[]          cfbOutV;

    private int                 blockSize;
    private BlockCipher         cipher = null;

    
Basic constructor.
Params:
cipher – the block cipher to be used as the basis of the
feedback mode.
blockSize – the block size in bits (note: a multiple of 8)/**
     * Basic constructor.
     *
     * @param cipher the block cipher to be used as the basis of the
     * feedback mode.
     * @param blockSize the block size in bits (note: a multiple of 8)
     */
    public MacCFBBlockCipher(
        BlockCipher         cipher,
        int                 bitBlockSize)
    {
        this.cipher = cipher;
        this.blockSize = bitBlockSize / 8;

        this.IV = new byte[cipher.getBlockSize()];
        this.cfbV = new byte[cipher.getBlockSize()];
        this.cfbOutV = new byte[cipher.getBlockSize()];
    }

    
Initialise the cipher and, possibly, the initialisation vector (IV).
If an IV isn't passed as part of the parameter, the IV will be all zeros.
An IV which is too short is handled in FIPS compliant fashion.
Params:
param – the key and other data required by the cipher.
Throws:
IllegalArgumentException – if the params argument is
inappropriate./**
     * Initialise the cipher and, possibly, the initialisation vector (IV).
     * If an IV isn't passed as part of the parameter, the IV will be all zeros.
     * An IV which is too short is handled in FIPS compliant fashion.
     *
     * @param param the key and other data required by the cipher.
     * @exception IllegalArgumentException if the params argument is
     * inappropriate.
     */
    public void init(
        CipherParameters    params)
        throws IllegalArgumentException
    {
        if (params instanceof ParametersWithIV)
        {
                ParametersWithIV ivParam = (ParametersWithIV)params;
                byte[]      iv = ivParam.getIV();

                if (iv.length < IV.length)
                {
                    System.arraycopy(iv, 0, IV, IV.length - iv.length, iv.length);
                }
                else
                {
                    System.arraycopy(iv, 0, IV, 0, IV.length);
                }

                reset();

                cipher.init(true, ivParam.getParameters());
        }
        else
        {
                reset();

                cipher.init(true, params);
        }
    }

    
return the algorithm name and mode.
Returns:
the name of the underlying algorithm followed by "/CFB"
and the block size in bits./**
     * return the algorithm name and mode.
     *
     * @return the name of the underlying algorithm followed by "/CFB"
     * and the block size in bits.
     */
    public String getAlgorithmName()
    {
        return cipher.getAlgorithmName() + "/CFB" + (blockSize * 8);
    }

    
return the block size we are operating at.
Returns:
the block size we are operating at (in bytes)./**
     * return the block size we are operating at.
     *
     * @return the block size we are operating at (in bytes).
     */
    public int getBlockSize()
    {
        return blockSize;
    }

    
Process one block of input from the array in and write it to
the out array.
Params:
in – the array containing the input data.
inOff – offset into the in array the data starts at.
out – the array the output data will be copied into.
outOff – the offset into the out array the output will start at.
Throws:
DataLengthException – if there isn't enough data in in, or
space in out.
IllegalStateException – if the cipher isn't initialised.
Returns:
the number of bytes processed and produced./**
     * Process one block of input from the array in and write it to
     * the out array.
     *
     * @param in the array containing the input data.
     * @param inOff offset into the in array the data starts at.
     * @param out the array the output data will be copied into.
     * @param outOff the offset into the out array the output will start at.
     * @exception DataLengthException if there isn't enough data in in, or
     * space in out.
     * @exception IllegalStateException if the cipher isn't initialised.
     * @return the number of bytes processed and produced.
     */
    public int processBlock(
        byte[]      in,
        int         inOff,
        byte[]      out,
        int         outOff)
        throws DataLengthException, IllegalStateException
    {
        if ((inOff + blockSize) > in.length)
        {
            throw new DataLengthException("input buffer too short");
        }

        if ((outOff + blockSize) > out.length)
        {
            throw new OutputLengthException("output buffer too short");
        }

        cipher.processBlock(cfbV, 0, cfbOutV, 0);

        //
        // XOR the cfbV with the plaintext producing the cipher text
        //
        for (int i = 0; i < blockSize; i++)
        {
            out[outOff + i] = (byte)(cfbOutV[i] ^ in[inOff + i]);
        }

        //
        // change over the input block.
        //
        System.arraycopy(cfbV, blockSize, cfbV, 0, cfbV.length - blockSize);
        System.arraycopy(out, outOff, cfbV, cfbV.length - blockSize, blockSize);

        return blockSize;
    }

    
reset the chaining vector back to the IV and reset the underlying
cipher.
/**
     * reset the chaining vector back to the IV and reset the underlying
     * cipher.
     */
    public void reset()
    {
        System.arraycopy(IV, 0, cfbV, 0, IV.length);

        cipher.reset();
    }

    void getMacBlock(
        byte[]  mac)
    {
        cipher.processBlock(cfbV, 0, mac, 0);
    }
}

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

    private byte[]              buf;
    private int                 bufOff;
    private MacCFBBlockCipher   cipher;
    private BlockCipherPadding  padding = null;


    private int                 macSize;

    
create a standard MAC based on a CFB block cipher. This will produce an
authentication code half the length of the block size of the cipher, with
the CFB mode set to 8 bits.
Params:
cipher – the cipher to be used as the basis of the MAC generation./**
     * create a standard MAC based on a CFB block cipher. This will produce an
     * authentication code half the length of the block size of the cipher, with
     * the CFB mode set to 8 bits.
     *
     * @param cipher the cipher to be used as the basis of the MAC generation.
     */
    public CFBBlockCipherMac(
        BlockCipher     cipher)
    {
        this(cipher, 8, (cipher.getBlockSize() * 8) / 2, null);
    }

    
create a standard MAC based on a CFB block cipher. This will produce an
authentication code half the length of the block size of the cipher, with
the CFB mode set to 8 bits.
Params:
cipher – the cipher to be used as the basis of the MAC generation.
padding – the padding to be used./**
     * create a standard MAC based on a CFB block cipher. This will produce an
     * authentication code half the length of the block size of the cipher, with
     * the CFB mode set to 8 bits.
     *
     * @param cipher the cipher to be used as the basis of the MAC generation.
     * @param padding the padding to be used.
     */
    public CFBBlockCipherMac(
        BlockCipher         cipher,
        BlockCipherPadding  padding)
    {
        this(cipher, 8, (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 CFB 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.
cfbBitSize – the size of an output block produced by the CFB mode.
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 CFB 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 cfbBitSize the size of an output block produced by the CFB mode.
     * @param macSizeInBits the size of the MAC in bits, must be a multiple of 8.
     */
    public CFBBlockCipherMac(
        BlockCipher         cipher,
        int                 cfbBitSize,
        int                 macSizeInBits)
    {
        this(cipher, cfbBitSize, macSizeInBits, null);
    }

    
create a standard MAC based on a block cipher with the size of the
MAC been given in bits. This class uses CFB 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.
cfbBitSize – the size of an output block produced by the CFB mode.
macSizeInBits – the size of the MAC in bits, must be a multiple of 8.
padding – a padding to be used./**
     * create a standard MAC based on a block cipher with the size of the
     * MAC been given in bits. This class uses CFB 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 cfbBitSize the size of an output block produced by the CFB mode.
     * @param macSizeInBits the size of the MAC in bits, must be a multiple of 8.
     * @param padding a padding to be used.
     */
    public CFBBlockCipherMac(
        BlockCipher         cipher,
        int                 cfbBitSize,
        int                 macSizeInBits,
        BlockCipherPadding  padding)
    {
        if ((macSizeInBits % 8) != 0)
        {
            throw new IllegalArgumentException("MAC size must be multiple of 8");
        }

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

        this.cipher = new MacCFBBlockCipher(cipher, cfbBitSize);
        this.padding = padding;
        this.macSize = macSizeInBits / 8;

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

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

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

        cipher.init(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
        //
        if (this.padding == null)
        {
            while (bufOff < blockSize)
            {
                buf[bufOff] = 0;
                bufOff++;
            }
        }
        else
        {
            padding.addPadding(buf, bufOff);
        }

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

        cipher.getMacBlock(mac);

        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();
    }
}