CMac
using Org.BouncyCastle.Crypto.Modes;
using Org.BouncyCastle.Crypto.Paddings;
using Org.BouncyCastle.Crypto.Parameters;
using System;
namespace Org.BouncyCastle.Crypto.Macs
{
public class CMac : IMac
{
private const byte CONSTANT_128 = 135;
private const byte CONSTANT_64 = 27;
private byte[] ZEROES;
private byte[] mac;
private byte[] buf;
private int bufOff;
private IBlockCipherMode m_cipherMode;
private int macSize;
private byte[] L;
private byte[] Lu;
private byte[] Lu2;
public string AlgorithmName => m_cipherMode.AlgorithmName;
public CMac(IBlockCipher cipher)
: this(cipher, cipher.GetBlockSize() * 8)
{
}
public CMac(IBlockCipher cipher, int macSizeInBits)
{
if (macSizeInBits % 8 != 0)
throw new ArgumentException("MAC size must be multiple of 8");
if (macSizeInBits > cipher.GetBlockSize() * 8)
throw new ArgumentException("MAC size must be less or equal to " + (cipher.GetBlockSize() * 8).ToString());
if (cipher.GetBlockSize() != 8 && cipher.GetBlockSize() != 16)
throw new ArgumentException("Block size must be either 64 or 128 bits");
m_cipherMode = new CbcBlockCipher(cipher);
macSize = macSizeInBits / 8;
mac = new byte[cipher.GetBlockSize()];
buf = new byte[cipher.GetBlockSize()];
ZEROES = new byte[cipher.GetBlockSize()];
bufOff = 0;
}
private static int ShiftLeft(byte[] block, byte[] output)
{
int num = block.Length;
uint num2 = 0;
while (--num >= 0) {
uint num3 = block[num];
output[num] = (byte)((num3 << 1) | num2);
num2 = ((num3 >> 7) & 1);
}
return (int)num2;
}
private static byte[] DoubleLu(byte[] input)
{
byte[] array = new byte[input.Length];
int num = ShiftLeft(input, array);
int num2 = (input.Length == 16) ? 135 : 27;
array[input.Length - 1] ^= (byte)(num2 >> (1 - num << 3));
return array;
}
public void Init(ICipherParameters parameters)
{
if (parameters is KeyParameter) {
m_cipherMode.Init(true, parameters);
L = new byte[ZEROES.Length];
m_cipherMode.ProcessBlock(ZEROES, 0, L, 0);
Lu = DoubleLu(L);
Lu2 = DoubleLu(Lu);
} else if (parameters != null) {
throw new ArgumentException("CMac mode only permits key to be set.", "parameters");
}
Reset();
}
public int GetMacSize()
{
return macSize;
}
public void Update(byte input)
{
if (bufOff == buf.Length) {
m_cipherMode.ProcessBlock(buf, 0, mac, 0);
bufOff = 0;
}
buf[bufOff++] = input;
}
public void BlockUpdate(byte[] inBytes, int inOff, int len)
{
if (len < 0)
throw new ArgumentException("Can't have a negative input length!");
BlockUpdate(inBytes.AsSpan(inOff, len));
}
public void BlockUpdate(ReadOnlySpan<byte> input)
{
int blockSize = m_cipherMode.GetBlockSize();
int num = blockSize - bufOff;
if (input.Length > num) {
input.Slice(0, num).CopyTo(buf.AsSpan(bufOff));
m_cipherMode.ProcessBlock(buf, mac);
bufOff = 0;
int num2 = num;
input = input.Slice(num2, input.Length - num2);
while (input.Length > blockSize) {
m_cipherMode.ProcessBlock(input, mac);
num2 = blockSize;
input = input.Slice(num2, input.Length - num2);
}
}
input.CopyTo(buf.AsSpan(bufOff));
bufOff += input.Length;
}
public int DoFinal(byte[] outBytes, int outOff)
{
return DoFinal(outBytes.AsSpan(outOff));
}
public int DoFinal(Span<byte> output)
{
int blockSize = m_cipherMode.GetBlockSize();
byte[] array;
if (bufOff == blockSize)
array = Lu;
else {
new ISO7816d4Padding().AddPadding(buf, bufOff);
array = Lu2;
}
for (int i = 0; i < mac.Length; i++) {
buf[i] ^= array[i];
}
m_cipherMode.ProcessBlock(buf, mac);
mac.AsSpan(0, macSize).CopyTo(output);
Reset();
return macSize;
}
public void Reset()
{
Array.Clear(buf, 0, buf.Length);
bufOff = 0;
m_cipherMode.Reset();
}
}
}