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//
// MACAlgorithm.cs: Handles MAC with any symmetric algorithm
//
// Author:
// Sebastien Pouliot (spouliot@motus.com)
//
// (C) 2002, 2003 Motus Technologies Inc. (http://www.motus.com)
// Copyright (C) 2004 Novell, Inc (http://www.novell.com)
//
// Permission is hereby granted, free of charge, to any person obtaining
// a copy of this software and associated documentation files (the
// "Software"), to deal in the Software without restriction, including
// without limitation the rights to use, copy, modify, merge, publish,
// distribute, sublicense, and/or sell copies of the Software, and to
// permit persons to whom the Software is furnished to do so, subject to
// the following conditions:
//
// The above copyright notice and this permission notice shall be
// included in all copies or substantial portions of the Software.
//
// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
// EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
// MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
// NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE
// LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION
// OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION
// WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
//
using System;
using System.Security.Cryptography;
namespace Mono.Security.Cryptography {
// References:
// a. FIPS PUB 81: DES MODES OF OPERATION
// MAC: Appendix F (MACDES not MACTripleDES but close enough ;-)
// http://www.itl.nist.gov/fipspubs/fip81.htm
// Generic MAC mechanims - most of the work is done in here
// It should work with any symmetric algorithm function e.g. DES for MACDES (fips81)
internal class MACAlgorithm {
private SymmetricAlgorithm algo;
private ICryptoTransform enc;
private byte[] block;
private int blockSize;
private int blockCount;
public MACAlgorithm (SymmetricAlgorithm algorithm)
{
algo = (SymmetricAlgorithm) algorithm;
algo.Mode = CipherMode.CBC;
blockSize = (algo.BlockSize >> 3); // in bytes
algo.IV = new byte [blockSize];
block = new byte [blockSize];
}
public void Initialize (byte[] key)
{
algo.Key = key;
// note: the encryptor transform may be reusable - see Final
if (enc == null) {
enc = algo.CreateEncryptor ();
}
Array.Clear (block, 0, blockSize);
blockCount = 0;
}
public void Core (byte[] rgb, int ib, int cb)
{
// 1. fill the rest of the "block"
int n = System.Math.Min (blockSize - blockCount, cb);
Array.Copy (rgb, ib, block, blockCount, n);
blockCount += n;
// 2. if block is full then transform it
if (blockCount == blockSize) {
enc.TransformBlock (block, 0, blockSize, block, 0);
// 3. transform any other full block in specified buffer
int b = (int) ((cb - n) / blockSize);
for (int i=0; i < b; i++) {
enc.TransformBlock (rgb, n, blockSize, block, 0);
n += blockSize;
}
// 4. if data is still present fill the "block" with the remainder
blockCount = cb - n;
if (blockCount > 0)
Array.Copy (rgb, n, block, 0, blockCount);
}
}
public byte[] Final ()
{
byte[] result;
if ((blockCount > 0) || ((algo.Padding != PaddingMode.Zeros) && (algo.Padding != PaddingMode.None))) {
result = enc.TransformFinalBlock (block, 0, blockCount);
} else {
result = (byte[]) block.Clone ();
}
if (!enc.CanReuseTransform) {
enc.Dispose ();
enc = null;
}
return result;
}
}
}
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