mcs/class/corlib/System.Security.Cryptography/Rfc2898DeriveBytes.cs

   1 //
   2 // Rfc2898DeriveBytes.cs: RFC2898 (PKCS#5 v2) Key derivation for Password Based Encryption
   3 //
   4 // Author:
   5 //      Sebastien Pouliot (sebastien@ximian.com)
   6 //
   7 // (C) 2003 Motus Technologies Inc. (http://www.motus.com)
   8 // Copyright (C) 2004-2005 Novell, Inc (http://www.novell.com)
   9 //
  10 // Permission is hereby granted, free of charge, to any person obtaining
  11 // a copy of this software and associated documentation files (the
  12 // "Software"), to deal in the Software without restriction, including
  13 // without limitation the rights to use, copy, modify, merge, publish,
  14 // distribute, sublicense, and/or sell copies of the Software, and to
  15 // permit persons to whom the Software is furnished to do so, subject to
  16 // the following conditions:
  17 //
  18 // The above copyright notice and this permission notice shall be
  19 // included in all copies or substantial portions of the Software.
  20 //
  21 // THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
  22 // EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
  23 // MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
  24 // NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE
  25 // LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION
  26 // OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION
  27 // WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
  28 //
  29
  30 #if NET_2_0
  31
  32 using System.Text;
  33
  34 using Mono.Security.Cryptography;
  35
  36 namespace System.Security.Cryptography {
  37
  38         public class Rfc2898DeriveBytes : DeriveBytes {
  39
  40                 private const int defaultIterations = 1000;
  41
  42                 private int _iteration;
  43                 private byte[] _salt;
  44                 private HMACSHA1 _hmac;
  45                 private byte[] _buffer;
  46                 private int _pos;
  47                 private int _f;
  48
  49                 // constructors
  50
  51                 public Rfc2898DeriveBytes (string password, byte[] salt)
  52                         : this (password, salt, defaultIterations)
  53                 {
  54                 }
  55
  56                 public Rfc2898DeriveBytes (string password, byte[] salt, int iterations)
  57                 {
  58                         if (password == null)
  59                                 throw new ArgumentNullException ("password");
  60
  61                         Salt = salt;
  62                         IterationCount = iterations;
  63                         _hmac = new HMACSHA1 (Encoding.UTF8.GetBytes (password));
  64                 }
  65
  66                 public Rfc2898DeriveBytes (byte[] password, byte[] salt, int iterations)
  67                 {
  68                         if (password == null)
  69                                 throw new ArgumentNullException ("password");
  70
  71                         Salt = salt;
  72                         IterationCount = iterations;
  73                         _hmac = new HMACSHA1 (password);
  74                 }
  75
  76                 public Rfc2898DeriveBytes (string password, int saltSize)
  77                         : this (password, saltSize, defaultIterations)
  78                 {
  79                 }
  80
  81                 public Rfc2898DeriveBytes (string password, int saltSize, int iterations)
  82                 {
  83                         if (password == null)
  84                                 throw new ArgumentNullException ("password");
  85                         if (saltSize < 0)
  86                                 throw new ArgumentOutOfRangeException ("invalid salt length");
  87
  88                         Salt = KeyBuilder.Key (saltSize);
  89                         IterationCount = iterations;
  90                         _hmac = new HMACSHA1 (Encoding.UTF8.GetBytes (password));
  91                 }
  92
  93                 // properties
  94
  95                 public int IterationCount {
  96                         get { return _iteration; }
  97                         set {
  98                                 if (value < 1)
  99                                         throw new ArgumentOutOfRangeException ("IterationCount < 1");
 100
 101                                 _iteration = value;
 102                         }
 103                 }
 104
 105                 public byte[] Salt {
 106                         get { return (byte[]) _salt.Clone (); }
 107                         set {
 108                                 if (value == null)
 109                                         throw new ArgumentNullException ("Salt");
 110                                 if (value.Length < 8)
 111                                         throw new ArgumentException ("Salt < 8 bytes");
 112
 113                                 _salt = (byte[])value.Clone ();
 114                         }
 115                 }
 116
 117                 // methods
 118
 119                 private byte[] F (byte[] s, int c, int i)
 120                 {
 121                         byte[] data = new byte [s.Length + 4];
 122                         Buffer.BlockCopy (s, 0, data, 0, s.Length);
 123                         byte[] int4 = BitConverter.GetBytes (i);
 124                         Array.Reverse (int4, 0, 4);
 125                         Buffer.BlockCopy (int4, 0, data, s.Length, 4);
 126
 127                         // this is like j=0
 128                         byte[] u1 = _hmac.ComputeHash (data);
 129                         data = u1;
 130                         // so we start at j=1
 131                         for (int j=1; j < c; j++) {
 132                                 byte[] un = _hmac.ComputeHash (data);
 133                                 // xor
 134                                 for (int k=0; k < 20; k++)
 135                                         u1 [k] = (byte)(u1 [k] ^ un [k]);
 136                                 data = un;
 137                         }
 138                         return u1;
 139                 }
 140
 141                 public override byte[] GetBytes (int cb)
 142                 {
 143                         if (cb < 1)
 144                                 throw new ArgumentOutOfRangeException ("cb");
 145
 146                         int l = cb / 20;        // HMACSHA1 == 160 bits == 20 bytes
 147                         int r = cb % 20;        // remainder
 148                         if (r != 0)
 149                                 l++;            // rounding up
 150
 151                         byte[] result = new byte [cb];
 152                         int rpos = 0;
 153                         if (_pos > 0) {
 154                                 int count = Math.Min (20 - _pos, cb);
 155                                 Buffer.BlockCopy (_buffer, _pos, result, 0, count);
 156                                 if (count >= cb)
 157                                         return result;
 158                                 _pos = 0;
 159                                 rpos = 20 - cb;
 160                                 r = cb - rpos;
 161                         }
 162
 163                         for (int i=1; i <= l; i++) {
 164                                 _buffer = F (_salt, _iteration, ++_f);
 165                                 int count = ((i == l) ? r : 20);
 166                                 Buffer.BlockCopy (_buffer, _pos, result, rpos, count);
 167                                 rpos += _pos + count;
 168                                 _pos = ((count == 20) ? 0 : count);
 169                         }
 170
 171                         return result;
 172                 }
 173
 174                 public override void Reset ()
 175                 {
 176                         _buffer = null;
 177                         _pos = 0;
 178                         _f = 0;
 179                 }
 180         }
 181 }
 182
 183 #endif