HMAC.cs :  » 2.6.4-mono-.net-core » System.Security » System » Security » Cryptography » C# / CSharp Open Source

//
// HMAC.cs: Generic HMAC inplementation
//
// Author:
//  Sebastien Pouliot  <sebastien@ximian.com>
//
// (C) 2003 Motus Technologies Inc. (http://www.motus.com)
// Copyright (C) 2004-2005, 2007 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.Runtime.InteropServices;
using Mono.Security.Cryptography;

namespace System.Security.Cryptography{

  // Mostly copied from (internal) Mono.Security.Cryptography.HMACAlgorithm

  // References:
  // a.  FIPS PUB 198: The Keyed-Hash Message Authentication Code (HMAC), 2002 March.
  //  http://csrc.nist.gov/publications/fips/fips198/fips-198a.pdf
  // b.  Internet RFC 2104, HMAC, Keyed-Hashing for Message Authentication
  //  (include C source for HMAC-MD5)
  //  http://www.ietf.org/rfc/rfc2104.txt
  // c.  IETF RFC2202: Test Cases for HMAC-MD5 and HMAC-SHA-1
  //  (include C source for HMAC-MD5 and HAMAC-SHA1)
  //  http://www.ietf.org/rfc/rfc2202.txt
  // d.  ANSI X9.71, Keyed Hash Message Authentication Code.
  //  not free :-(
  //  http://webstore.ansi.org/ansidocstore/product.asp?sku=ANSI+X9%2E71%2D2000

  [ComVisible (true)]
  public abstract class HMAC : KeyedHashAlgorithm {

    private bool _disposed;
    private string _hashName;
    private HashAlgorithm _algo;
    private BlockProcessor _block;
    private int _blockSizeValue; 

    // constructors

    protected HMAC () 
    {
      _disposed = false;
      _blockSizeValue = 64;
    }

    // properties

    protected int BlockSizeValue {
      get { return _blockSizeValue; }
      set { _blockSizeValue = value;  }
    }

    public string HashName {
      get { return _hashName; }
      set { 
        _hashName = value; 
        _algo = HashAlgorithm.Create (_hashName);
      }
    }

    public override byte[] Key { 
      get { return (byte[]) base.Key.Clone (); }
      set { 
        if ((value != null) && (value.Length > 64))
          base.Key = _algo.ComputeHash (value);
        else
          base.Key = (byte[]) value.Clone();
      }
    }

    internal BlockProcessor Block {
      get {
        if (_block == null)
          _block = new BlockProcessor (_algo, (BlockSizeValue >> 3));
        return _block;
      }
    }

    // methods

    private byte[] KeySetup (byte[] key, byte padding) 
    {
      byte[] buf = new byte [BlockSizeValue];
  
      for (int i = 0; i < key.Length; ++i)
        buf [i] = (byte) ((byte) key [i] ^ padding);
  
      for (int i = key.Length; i < BlockSizeValue; ++i)
        buf [i] = padding;
      
      return buf;
    }

    protected override void Dispose (bool disposing) 
    {
      if (!_disposed) {
        base.Dispose (disposing);
      }
    }

    protected override void HashCore (byte[] rgb, int ib, int cb) 
    {
      if (_disposed)
        throw new ObjectDisposedException ("HMACSHA1");

      if (State == 0) {
        Initialize ();
        State = 1;
      }
      Block.Core (rgb, ib, cb);
    }

    protected override byte[] HashFinal () 
    {
      if (_disposed)
        throw new ObjectDisposedException ("HMAC");
      State = 0;

      Block.Final ();
      byte[] intermediate = _algo.Hash;
  
      byte[] buf = KeySetup (Key, 0x5C);
      _algo.Initialize ();
      _algo.TransformBlock (buf, 0, buf.Length, buf, 0);
      _algo.TransformFinalBlock (intermediate, 0, intermediate.Length);
      byte[] hash = _algo.Hash;
      _algo.Initialize ();
      // zeroize sensitive data
      Array.Clear (buf, 0, buf.Length);  
      Array.Clear (intermediate, 0, intermediate.Length);
      return hash;
    }

    public override void Initialize () 
    {
      if (_disposed)
        throw new ObjectDisposedException ("HMAC");

      State = 0;
      Block.Initialize ();
      byte[] buf = KeySetup (Key, 0x36);
      _algo.Initialize ();
      Block.Core (buf);
      // zeroize key
      Array.Clear (buf, 0, buf.Length);
    }

    // static methods

    public static new HMAC Create () 
    {
      return Create ("System.Security.Cryptography.HMAC");
    }

    public static new HMAC Create (string algorithmName) 
    {
      return (HMAC) CryptoConfig.CreateFromName (algorithmName);
    }
  }
}