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/* Transport Security Layer (TLS)
* Copyright (c) 2003-2004 Carlos Guzman Alvarez
*
* 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:
* RFC 2104 (http://www.ietf.org/rfc/rfc2104.txt)
* RFC 2202 (http://www.ietf.org/rfc/rfc2202.txt)
* MSDN:
*
* Extending the KeyedHashAlgorithm Class (http://msdn.microsoft.com/library/default.asp?url=/library/en-us/cpguide/html/cpconextendingkeyedhashalgorithmclass.asp)
*/
internal class HMAC : System.Security.Cryptography.KeyedHashAlgorithm
{
#region Fields
private HashAlgorithm hash;
private bool hashing;
private byte[] innerPad;
private byte[] outerPad;
#endregion
#region Properties
public override byte[] Key
{
get { return (byte[])KeyValue.Clone(); }
set
{
if (hashing)
{
throw new Exception("Cannot change key during hash operation.");
}
/* if key is longer than 64 bytes reset it to rgbKey = Hash(rgbKey) */
if (value.Length > 64)
{
KeyValue = hash.ComputeHash(value);
}
else
{
KeyValue = (byte[])value.Clone();
}
initializePad();
}
}
#endregion
#region Constructors
public HMAC()
{
// Create the hash
hash = MD5.Create();
// Set HashSizeValue
HashSizeValue = hash.HashSize;
// Generate a radom key
byte[] rgbKey = new byte[64];
RNGCryptoServiceProvider rng = new RNGCryptoServiceProvider();
rng.GetNonZeroBytes(rgbKey);
KeyValue = (byte[])rgbKey.Clone();
this.Initialize();
}
public HMAC(string hashName, byte[] rgbKey)
{
// Create the hash
if (hashName == null || hashName.Length == 0)
{
hashName = "MD5";
}
hash = HashAlgorithm.Create(hashName);
// Set HashSizeValue
HashSizeValue = hash.HashSize;
/* if key is longer than 64 bytes reset it to rgbKey = Hash(rgbKey) */
if (rgbKey.Length > 64)
{
KeyValue = hash.ComputeHash(rgbKey);
}
else
{
KeyValue = (byte[])rgbKey.Clone();
}
this.Initialize();
}
#endregion
#region Methods
public override void Initialize()
{
hash.Initialize();
initializePad();
hashing = false;
}
protected override byte[] HashFinal()
{
if (!hashing)
{
hash.TransformBlock(innerPad, 0, innerPad.Length, innerPad, 0);
hashing = true;
}
// Finalize the original hash
hash.TransformFinalBlock(new byte[0], 0, 0);
byte[] firstResult = hash.Hash;
hash.Initialize();
hash.TransformBlock(outerPad, 0, outerPad.Length, outerPad, 0);
hash.TransformFinalBlock(firstResult, 0, firstResult.Length);
Initialize();
return hash.Hash;
}
protected override void HashCore(
byte[] array,
int ibStart,
int cbSize)
{
if (!hashing)
{
hash.TransformBlock(innerPad, 0, innerPad.Length, innerPad, 0);
hashing = true;
}
hash.TransformBlock(array, ibStart, cbSize, array, ibStart);
}
#endregion
#region Private Methods
private void initializePad()
{
// Fill pad arrays
innerPad = new byte[64];
outerPad = new byte[64];
/* Pad the key for inner and outer digest */
for (int i = 0 ; i < KeyValue.Length; ++i)
{
innerPad[i] = (byte)(KeyValue[i] ^ 0x36);
outerPad[i] = (byte)(KeyValue[i] ^ 0x5C);
}
for (int i = KeyValue.Length; i < 64; ++i)
{
innerPad[i] = 0x36;
outerPad[i] = 0x5C;
}
}
#endregion
}
}
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