Code:
/ 4.0 / 4.0 / untmp / DEVDIV_TFS / Dev10 / Releases / RTMRel / ndp / clr / src / BCL / System / Security / Cryptography / mactripleDES.cs / 1305376 / mactripleDES.cs
// ==++== // // Copyright (c) Microsoft Corporation. All rights reserved. // // ==--== //[....] // // // MACTripleDES.cs -- Implementation of the MAC-CBC keyed hash w/ 3DES // // See: http://www.itl.nist.gov/fipspubs/fip81.htm for a spec namespace System.Security.Cryptography { using System.IO; using System.Diagnostics.Contracts; [System.Runtime.InteropServices.ComVisible(true)] public class MACTripleDES : KeyedHashAlgorithm { // Output goes to HashMemorySink since we don't care about the actual data private ICryptoTransform m_encryptor; private CryptoStream _cs; private TailStream _ts; private const int m_bitsPerByte = 8; private int m_bytesPerBlock; private TripleDES des; // // public constructors // [System.Security.SecuritySafeCritical] // auto-generated public MACTripleDES() { KeyValue = new byte[24]; Utils.StaticRandomNumberGenerator.GetBytes(KeyValue); // Create a TripleDES encryptor des = TripleDES.Create(); HashSizeValue = des.BlockSize; m_bytesPerBlock = des.BlockSize/m_bitsPerByte; // By definition, MAC-CBC-3DES takes an IV=0. C# zero-inits arrays, // so all we have to do here is define it. des.IV = new byte[m_bytesPerBlock]; des.Padding = PaddingMode.Zeros; m_encryptor = null; } [System.Security.SecuritySafeCritical] // auto-generated public MACTripleDES(byte[] rgbKey) : this("System.Security.Cryptography.TripleDES",rgbKey) {} [System.Security.SecuritySafeCritical] // auto-generated public MACTripleDES(String strTripleDES, byte[] rgbKey) { // Make sure we know which algorithm to use if (rgbKey == null) throw new ArgumentNullException("rgbKey"); Contract.EndContractBlock(); // Create a TripleDES encryptor if (strTripleDES == null) { des = TripleDES.Create(); } else { des = TripleDES.Create(strTripleDES); } HashSizeValue = des.BlockSize; // Stash the key away KeyValue = (byte[]) rgbKey.Clone(); m_bytesPerBlock = des.BlockSize/m_bitsPerByte; // By definition, MAC-CBC-3DES takes an IV=0. C# zero-inits arrays, // so all we have to do here is define it. des.IV = new byte[m_bytesPerBlock]; des.Padding = PaddingMode.Zeros; m_encryptor = null; } public override void Initialize() { m_encryptor = null; } [System.Runtime.InteropServices.ComVisible(false)] public PaddingMode Padding { get { return des.Padding; } set { if ((value < PaddingMode.None) || (PaddingMode.ISO10126 < value)) throw new CryptographicException(Environment.GetResourceString("Cryptography_InvalidPaddingMode")); des.Padding = value; } } // // protected methods // protected override void HashCore(byte[] rgbData, int ibStart, int cbSize) { // regenerate the TripleDES object before each call to ComputeHash if (m_encryptor == null) { des.Key = this.Key; m_encryptor = des.CreateEncryptor(); _ts = new TailStream(des.BlockSize / 8); // 8 bytes _cs = new CryptoStream(_ts, m_encryptor, CryptoStreamMode.Write); } // Encrypt using 3DES _cs.Write(rgbData, ibStart, cbSize); } protected override byte[] HashFinal() { // If Hash has been called on a zero buffer if (m_encryptor == null) { des.Key = this.Key; m_encryptor = des.CreateEncryptor(); _ts = new TailStream(des.BlockSize / 8); // 8 bytes _cs = new CryptoStream(_ts, m_encryptor, CryptoStreamMode.Write); } // Finalize the hashing and return the result _cs.FlushFinalBlock(); return _ts.Buffer; } // IDisposable methods protected override void Dispose(bool disposing) { if (disposing) { // dispose of our internal state if (des != null) des.Clear(); if (m_encryptor != null) m_encryptor.Dispose(); if (_cs != null) _cs.Clear(); if (_ts != null) _ts.Clear(); } base.Dispose(disposing); } } // // TailStream is another utility class -- it remembers the last n bytes written to it // This is useful for MAC-3DES since we need to capture only the result of the last block internal sealed class TailStream : Stream { private byte[] _Buffer; private int _BufferSize; private int _BufferIndex = 0; private bool _BufferFull = false; public TailStream(int bufferSize) { _Buffer = new byte[bufferSize]; _BufferSize = bufferSize; } public void Clear() { Close(); } protected override void Dispose(bool disposing) { try { if (disposing) { if (_Buffer != null) { Array.Clear(_Buffer, 0, _Buffer.Length); } _Buffer = null; } } finally { base.Dispose(disposing); } } public byte[] Buffer { get { return (byte[]) _Buffer.Clone(); } } public override bool CanRead { [Pure] get { return false; } } public override bool CanSeek { [Pure] get { return false; } } public override bool CanWrite { [Pure] get { return _Buffer != null; } } public override long Length { get { throw new NotSupportedException(Environment.GetResourceString("NotSupported_UnseekableStream")); } } public override long Position { get { throw new NotSupportedException(Environment.GetResourceString("NotSupported_UnseekableStream")); } set { throw new NotSupportedException(Environment.GetResourceString("NotSupported_UnseekableStream")); } } public override void Flush() { return; } public override long Seek(long offset, SeekOrigin origin) { throw new NotSupportedException(Environment.GetResourceString("NotSupported_UnseekableStream")); } public override void SetLength(long value) { throw new NotSupportedException(Environment.GetResourceString("NotSupported_UnseekableStream")); } public override int Read(byte[] buffer, int offset, int count) { throw new NotSupportedException(Environment.GetResourceString("NotSupported_UnreadableStream")); } [System.Security.SecuritySafeCritical] // auto-generated public override void Write(byte[] buffer, int offset, int count) { if (_Buffer == null) throw new ObjectDisposedException("TailStream"); // If no bytes to write, then return if (count == 0) return; // The most common case will be when we have a full buffer if (_BufferFull) { // if more bytes are written in this call than the size of the buffer, // just remember the last _BufferSize bytes if (count > _BufferSize) { System.Buffer.InternalBlockCopy(buffer, offset+count-_BufferSize, _Buffer, 0, _BufferSize); return; } else { // move _BufferSize - count bytes left, then copy the new bytes System.Buffer.InternalBlockCopy(_Buffer, _BufferSize - count, _Buffer, 0, _BufferSize - count); System.Buffer.InternalBlockCopy(buffer, offset, _Buffer, _BufferSize - count, count); return; } } else { // buffer isn't full yet, so more cases if (count > _BufferSize) { System.Buffer.InternalBlockCopy(buffer, offset+count-_BufferSize, _Buffer, 0, _BufferSize); _BufferFull = true; return; } else if (count + _BufferIndex >= _BufferSize) { System.Buffer.InternalBlockCopy(_Buffer, _BufferIndex+count-_BufferSize, _Buffer, 0, _BufferSize - count); System.Buffer.InternalBlockCopy(buffer, offset, _Buffer, _BufferIndex, count); _BufferFull = true; return; } else { System.Buffer.InternalBlockCopy(buffer, offset, _Buffer, _BufferIndex, count); _BufferIndex += count; return; } } } } } // File provided for Reference Use Only by Microsoft Corporation (c) 2007.
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