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