class/corlib/Mono.Security.Cryptography/HMACAlgorithm.cs

   1 //
   2 // HMACAlgorithm.cs: Handles HMAC with any hash algorithm
   3 //
   4 // Author:
   5 //      Sebastien Pouliot (spouliot@motus.com)
   6 //
   7 // (C) 2002, 2003 Motus Technologies Inc. (http://www.motus.com)
   8 //
   9
  10 //
  11 // Copyright (C) 2004 Novell, Inc (http://www.novell.com)
  12 //
  13 // Permission is hereby granted, free of charge, to any person obtaining
  14 // a copy of this software and associated documentation files (the
  15 // "Software"), to deal in the Software without restriction, including
  16 // without limitation the rights to use, copy, modify, merge, publish,
  17 // distribute, sublicense, and/or sell copies of the Software, and to
  18 // permit persons to whom the Software is furnished to do so, subject to
  19 // the following conditions:
  20 //
  21 // The above copyright notice and this permission notice shall be
  22 // included in all copies or substantial portions of the Software.
  23 //
  24 // THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
  25 // EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
  26 // MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
  27 // NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE
  28 // LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION
  29 // OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION
  30 // WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
  31 //
  32
  33 using System;
  34 using System.Security.Cryptography;
  35
  36 namespace Mono.Security.Cryptography {
  37
  38         // References:
  39         // a.   FIPS PUB 198: The Keyed-Hash Message Authentication Code (HMAC), 2002 March.
  40         //      http://csrc.nist.gov/publications/fips/fips198/fips-198a.pdf
  41         // b.   Internet RFC 2104, HMAC, Keyed-Hashing for Message Authentication
  42         //      (include C source for HMAC-MD5)
  43         //      http://www.ietf.org/rfc/rfc2104.txt
  44         // c.   IETF RFC2202: Test Cases for HMAC-MD5 and HMAC-SHA-1
  45         //      (include C source for HMAC-MD5 and HAMAC-SHA1)
  46         //      http://www.ietf.org/rfc/rfc2202.txt
  47         // d.   ANSI X9.71, Keyed Hash Message Authentication Code.
  48         //      not free :-(
  49         //      http://webstore.ansi.org/ansidocstore/product.asp?sku=ANSI+X9%2E71%2D2000
  50
  51         // Generic HMAC mechanisms - most of HMAC work is done in here.
  52         // It should work with any hash function e.g. MD5 for HMACMD5 (RFC2104)
  53         internal class HMACAlgorithm {
  54
  55                 private byte[] key;
  56                 private byte[] hash;
  57                 private HashAlgorithm algo;
  58                 private string hashName;
  59                 private BlockProcessor block;
  60
  61                 public HMACAlgorithm (string algoName)
  62                 {
  63                         CreateHash (algoName);
  64                 }
  65
  66                 ~HMACAlgorithm ()
  67                 {
  68                         Dispose ();
  69                 }
  70
  71                 private void CreateHash (string algoName)
  72                 {
  73                         algo = HashAlgorithm.Create (algoName);
  74                         hashName = algoName;
  75                         block = new BlockProcessor (algo, 8);
  76                 }
  77
  78                 public void Dispose ()
  79                 {
  80                         if (key != null)
  81                                 Array.Clear (key, 0, key.Length);
  82                 }
  83
  84                 public HashAlgorithm Algo {
  85                         get { return algo; }
  86                 }
  87
  88                 public string HashName {
  89                         get { return hashName; }
  90                         set { CreateHash (value); }
  91                 }
  92
  93                 public byte[] Key {
  94                         get { return key; }
  95                         set {
  96                                 if ((value != null) && (value.Length > 64))
  97                                         key = algo.ComputeHash (value);
  98                                 else
  99                                         key = (byte[]) value.Clone();
 100                         }
 101                 }
 102
 103                 public void Initialize ()
 104                 {
 105                         hash = null;
 106                         block.Initialize ();
 107                         byte[] buf = KeySetup (key, 0x36);
 108                         algo.Initialize ();
 109                         block.Core (buf);
 110                         // zeroize key
 111                         Array.Clear (buf, 0, buf.Length);
 112                 }
 113
 114                 private byte[] KeySetup (byte[] key, byte padding)
 115                 {
 116                         byte[] buf = new byte [64];
 117
 118                         for (int i = 0; i < key.Length; ++i)
 119                                 buf [i] = (byte) ((byte) key [i] ^ padding);
 120
 121                         for (int i = key.Length; i < 64; ++i)
 122                                 buf [i] = padding;
 123
 124                         return buf;
 125                 }
 126
 127                 public void Core (byte[] rgb, int ib, int cb)
 128                 {
 129                         block.Core (rgb, ib, cb);
 130                 }
 131
 132                 public byte[] Final ()
 133                 {
 134                         block.Final ();
 135                         byte[] intermediate = algo.Hash;
 136
 137                         byte[] buf = KeySetup (key, 0x5C);
 138                         algo.Initialize ();
 139                         algo.TransformBlock (buf, 0, buf.Length, buf, 0);
 140                         algo.TransformFinalBlock (intermediate, 0, intermediate.Length);
 141                         hash = algo.Hash;
 142                         algo.Clear ();
 143                         // zeroize sensitive data
 144                         Array.Clear (buf, 0, buf.Length);
 145                         Array.Clear (intermediate, 0, intermediate.Length);
 146                         return hash;
 147                 }
 148         }
 149 }