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//
// HMACAlgorithm.cs: Handles HMAC with any hash 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 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
// Generic HMAC mechanisms - most of HMAC work is done in here.
// It should work with any hash function e.g. MD5 for HMACMD5 (RFC2104)
internal class HMACAlgorithm {
private byte[] key;
private byte[] hash;
private HashAlgorithm algo;
private string hashName;
private BlockProcessor block;
public HMACAlgorithm (string algoName)
{
CreateHash (algoName);
}
~HMACAlgorithm ()
{
Dispose ();
}
private void CreateHash (string algoName)
{
algo = HashAlgorithm.Create (algoName);
hashName = algoName;
block = new BlockProcessor (algo, 8);
}
public void Dispose ()
{
if (key != null)
Array.Clear (key, 0, key.Length);
}
public HashAlgorithm Algo {
get { return algo; }
}
public string HashName {
get { return hashName; }
set { CreateHash (value); }
}
public byte[] Key {
get { return key; }
set {
if ((value != null) && (value.Length > 64))
key = algo.ComputeHash (value);
else
key = (byte[]) value.Clone();
}
}
public void Initialize ()
{
hash = null;
block.Initialize ();
byte[] buf = KeySetup (key, 0x36);
algo.Initialize ();
block.Core (buf);
// zeroize key
Array.Clear (buf, 0, buf.Length);
}
private byte[] KeySetup (byte[] key, byte padding)
{
byte[] buf = new byte [64];
for (int i = 0; i < key.Length; ++i)
buf [i] = (byte) ((byte) key [i] ^ padding);
for (int i = key.Length; i < 64; ++i)
buf [i] = padding;
return buf;
}
public void Core (byte[] rgb, int ib, int cb)
{
block.Core (rgb, ib, cb);
}
public byte[] Final ()
{
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);
hash = algo.Hash;
algo.Clear ();
// zeroize sensitive data
Array.Clear (buf, 0, buf.Length);
Array.Clear (intermediate, 0, intermediate.Length);
return hash;
}
}
}
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