mcs/class/Mono.Security/Mono.Security.Cryptography/TlsHMAC.cs

   1 /* Transport Security Layer (TLS)
   2  * Copyright (c) 2003-2004 Carlos Guzman Alvarez
   3  *
   4  * Permission is hereby granted, free of charge, to any person
   5  * obtaining a copy of this software and associated documentation
   6  * files (the "Software"), to deal in the Software without restriction,
   7  * including without limitation the rights to use, copy, modify, merge,
   8  * publish, distribute, sublicense, and/or sell copies of the Software,
   9  * and to permit persons to whom the Software is furnished to do so,
  10  * subject to the following conditions:
  11  *
  12  * The above copyright notice and this permission notice shall be included
  13  * in all copies or substantial portions of the Software.
  14  *
  15  * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
  16  * EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES
  17  * OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
  18  * NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT
  19  * HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY,
  20  * WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
  21  * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
  22  * DEALINGS IN THE SOFTWARE.
  23  */
  24
  25 using System;
  26 using System.Security.Cryptography;
  27
  28 namespace Mono.Security.Cryptography
  29 {
  30    /*
  31         * References:
  32         *               RFC 2104 (http://www.ietf.org/rfc/rfc2104.txt)
  33         *               RFC 2202 (http://www.ietf.org/rfc/rfc2202.txt)
  34         * MSDN:
  35         *
  36         *               Extending the KeyedHashAlgorithm Class (http://msdn.microsoft.com/library/default.asp?url=/library/en-us/cpguide/html/cpconextendingkeyedhashalgorithmclass.asp)
  37         */
  38         internal class HMAC : System.Security.Cryptography.KeyedHashAlgorithm
  39         {
  40                 #region Fields
  41
  42                 private HashAlgorithm   hash;
  43                 private bool                    hashing;
  44
  45                 private byte[]                  innerPad;
  46                 private byte[]                  outerPad;
  47
  48                 #endregion
  49
  50                 #region Properties
  51
  52                 public override byte[] Key
  53                 {
  54                         get { return (byte[])KeyValue.Clone(); }
  55                         set
  56                         {
  57                                 if (hashing)
  58                                 {
  59                                         throw new Exception("Cannot change key during hash operation.");
  60                                 }
  61
  62                                 /* if key is longer than 64 bytes reset it to rgbKey = Hash(rgbKey) */
  63                                 if (value.Length > 64)
  64                                 {
  65                                         KeyValue = hash.ComputeHash(value);
  66                                 }
  67                                 else
  68                                 {
  69                                         KeyValue = (byte[])value.Clone();
  70                                 }
  71
  72                                 initializePad();
  73                         }
  74                 }
  75
  76                 #endregion
  77
  78                 #region Constructors
  79
  80                 public HMAC()
  81                 {
  82                         // Create the hash
  83                         hash = MD5.Create();
  84                         // Set HashSizeValue
  85                         HashSizeValue = hash.HashSize;
  86
  87                         // Generate a radom key
  88                         byte[] rgbKey = new byte[64];
  89                         RNGCryptoServiceProvider rng = new RNGCryptoServiceProvider();
  90                         rng.GetNonZeroBytes(rgbKey);
  91
  92                         KeyValue = (byte[])rgbKey.Clone();
  93
  94                         this.Initialize();
  95                 }
  96
  97                 public HMAC(string hashName, byte[] rgbKey)
  98                 {
  99                         // Create the hash
 100                         if (hashName == null || hashName.Length == 0)
 101                         {
 102                                 hashName = "MD5";
 103                         }
 104                         hash = HashAlgorithm.Create(hashName);
 105                         // Set HashSizeValue
 106                         HashSizeValue = hash.HashSize;
 107
 108                         /* if key is longer than 64 bytes reset it to rgbKey = Hash(rgbKey) */
 109                         if (rgbKey.Length > 64)
 110                         {
 111                                 KeyValue = hash.ComputeHash(rgbKey);
 112                         }
 113                         else
 114                         {
 115                                 KeyValue = (byte[])rgbKey.Clone();
 116                         }
 117
 118                         this.Initialize();
 119                 }
 120
 121                 #endregion
 122
 123                 #region Methods
 124
 125                 public override void Initialize()
 126                 {
 127                         hash.Initialize();
 128                         initializePad();
 129                         hashing = false;
 130                 }
 131
 132                 protected override byte[] HashFinal()
 133                 {
 134                         if (!hashing)
 135                         {
 136                                 hash.TransformBlock(innerPad, 0, innerPad.Length, innerPad, 0);
 137                                 hashing = true;
 138                         }
 139                         // Finalize the original hash
 140                         hash.TransformFinalBlock(new byte[0], 0, 0);
 141
 142                         byte[] firstResult = hash.Hash;
 143
 144                         hash.Initialize();
 145                         hash.TransformBlock(outerPad, 0, outerPad.Length, outerPad, 0);
 146                         hash.TransformFinalBlock(firstResult, 0, firstResult.Length);
 147
 148                         Initialize();
 149
 150                         return hash.Hash;
 151                 }
 152
 153                 protected override void HashCore(
 154                         byte[] array,
 155                         int ibStart,
 156                         int cbSize)
 157                 {
 158                         if (!hashing)
 159                         {
 160                                 hash.TransformBlock(innerPad, 0, innerPad.Length, innerPad, 0);
 161                                 hashing = true;
 162                         }
 163                         hash.TransformBlock(array, ibStart, cbSize, array, ibStart);
 164                 }
 165
 166                 #endregion
 167
 168                 #region Private Methods
 169
 170                 private void initializePad()
 171                 {
 172                         // Fill pad arrays
 173                         innerPad = new byte[64];
 174                         outerPad = new byte[64];
 175
 176                         /* Pad the key for inner and outer digest */
 177                         for (int i = 0 ; i < KeyValue.Length; ++i)
 178                         {
 179                                 innerPad[i] = (byte)(KeyValue[i] ^ 0x36);
 180                                 outerPad[i] = (byte)(KeyValue[i] ^ 0x5C);
 181                         }
 182                         for (int i = KeyValue.Length; i < 64; ++i)
 183                         {
 184                                 innerPad[i] = 0x36;
 185                                 outerPad[i] = 0x5C;
 186                         }
 187                 }
 188
 189                 #endregion
 190         }
 191 }