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using System;
using Org.BouncyCastle.Crypto.Modes;
using Org.BouncyCastle.Crypto.Paddings;
namespace Org.BouncyCastle.Crypto.Macs
{
/**
* standard CBC Block Cipher MAC - if no padding is specified the default of
* pad of zeroes is used.
*/
public class CbcBlockCipherMac
: IMac
{
private byte[] buf;
private int bufOff;
private IBlockCipher cipher;
private IBlockCipherPadding 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.
*
* @param cipher the cipher to be used as the basis of the MAC generation.
*/
public CbcBlockCipherMac(
IBlockCipher 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.
*
* @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(
IBlockCipher cipher,
IBlockCipherPadding 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.
* <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).
* </p>
* @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(
IBlockCipher 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.
* <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).
* </p>
* @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(
IBlockCipher cipher,
int macSizeInBits,
IBlockCipherPadding padding)
{
if ((macSizeInBits % 8) != 0)
throw new ArgumentException("MAC size must be multiple of 8");
this.cipher = new CbcBlockCipher(cipher);
this.padding = padding;
this.macSize = macSizeInBits / 8;
buf = new byte[cipher.GetBlockSize()];
bufOff = 0;
}
public string AlgorithmName
{
get { return cipher.AlgorithmName; }
}
public void Init(ICipherParameters parameters)
{
Reset();
cipher.Init(true, parameters);
}
public int GetMacSize()
{
return macSize;
}
public void Update(byte input)
{
if (bufOff == buf.Length)
{
cipher.ProcessBlock(buf, 0, buf, 0);
bufOff = 0;
}
buf[bufOff++] = input;
}
public void BlockUpdate(byte[] input, int inOff, int len)
{
if (len < 0)
throw new ArgumentException("Can't have a negative input length!");
#if NETCOREAPP2_1_OR_GREATER || NETSTANDARD2_1_OR_GREATER
BlockUpdate(input.AsSpan(inOff, len));
#else
int blockSize = cipher.GetBlockSize();
int gapLen = blockSize - bufOff;
if (len > gapLen)
{
Array.Copy(input, inOff, buf, bufOff, gapLen);
cipher.ProcessBlock(buf, 0, buf, 0);
bufOff = 0;
len -= gapLen;
inOff += gapLen;
while (len > blockSize)
{
cipher.ProcessBlock(input, inOff, buf, 0);
len -= blockSize;
inOff += blockSize;
}
}
Array.Copy(input, inOff, buf, bufOff, len);
bufOff += len;
#endif
}
#if NETCOREAPP2_1_OR_GREATER || NETSTANDARD2_1_OR_GREATER
public void BlockUpdate(ReadOnlySpan<byte> input)
{
int blockSize = cipher.GetBlockSize();
int gapLen = blockSize - bufOff;
if (input.Length > gapLen)
{
input[..gapLen].CopyTo(buf.AsSpan(bufOff));
cipher.ProcessBlock(buf, buf);
bufOff = 0;
input = input[gapLen..];
while (input.Length > blockSize)
{
cipher.ProcessBlock(input, buf);
input = input[blockSize..];
}
}
input.CopyTo(buf.AsSpan(bufOff));
bufOff += input.Length;
}
#endif
public int DoFinal(byte[] output, int outOff)
{
#if NETCOREAPP2_1_OR_GREATER || NETSTANDARD2_1_OR_GREATER
return DoFinal(output.AsSpan(outOff));
#else
int blockSize = cipher.GetBlockSize();
if (padding == null)
{
// pad with zeroes
while (bufOff < blockSize)
{
buf[bufOff++] = 0;
}
}
else
{
if (bufOff == blockSize)
{
cipher.ProcessBlock(buf, 0, buf, 0);
bufOff = 0;
}
padding.AddPadding(buf, bufOff);
}
cipher.ProcessBlock(buf, 0, buf, 0);
Array.Copy(buf, 0, output, outOff, macSize);
Reset();
return macSize;
#endif
}
#if NETCOREAPP2_1_OR_GREATER || NETSTANDARD2_1_OR_GREATER
public int DoFinal(Span<byte> output)
{
int blockSize = cipher.GetBlockSize();
if (padding == null)
{
// pad with zeroes
while (bufOff < blockSize)
{
buf[bufOff++] = 0;
}
}
else
{
if (bufOff == blockSize)
{
cipher.ProcessBlock(buf, buf);
bufOff = 0;
}
padding.AddPadding(buf, bufOff);
}
cipher.ProcessBlock(buf, buf);
buf.AsSpan(0, macSize).CopyTo(output);
Reset();
return macSize;
}
#endif
/**
* Reset the mac generator.
*/
public void Reset()
{
// Clear the buffer.
Array.Clear(buf, 0, buf.Length);
bufOff = 0;
// Reset the underlying cipher.
cipher.Reset();
}
}
}
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