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.Runtime.InteropServices;
  33 using System.Text;
  34
  35 using Mono.Security.Cryptography;
  36
  37 namespace System.Security.Cryptography {
  38
  39         [ComVisible (true)]
  40         public class Rfc2898DeriveBytes : DeriveBytes {
  41
  42                 private const int defaultIterations = 1000;
  43
  44                 private int _iteration;
  45                 private byte[] _salt;
  46                 private HMACSHA1 _hmac;
  47                 private byte[] _buffer;
  48                 private int _pos;
  49                 private int _f;
  50
  51                 // constructors
  52
  53                 public Rfc2898DeriveBytes (string password, byte[] salt)
  54                         : this (password, salt, defaultIterations)
  55                 {
  56                 }
  57
  58                 public Rfc2898DeriveBytes (string password, byte[] salt, int iterations)
  59                 {
  60                         if (password == null)
  61                                 throw new ArgumentNullException ("password");
  62
  63                         Salt = salt;
  64                         IterationCount = iterations;
  65                         _hmac = new HMACSHA1 (Encoding.UTF8.GetBytes (password));
  66                 }
  67
  68                 public Rfc2898DeriveBytes (byte[] password, byte[] salt, int iterations)
  69                 {
  70                         if (password == null)
  71                                 throw new ArgumentNullException ("password");
  72
  73                         Salt = salt;
  74                         IterationCount = iterations;
  75                         _hmac = new HMACSHA1 (password);
  76                 }
  77
  78                 public Rfc2898DeriveBytes (string password, int saltSize)
  79                         : this (password, saltSize, defaultIterations)
  80                 {
  81                 }
  82
  83                 public Rfc2898DeriveBytes (string password, int saltSize, int iterations)
  84                 {
  85                         if (password == null)
  86                                 throw new ArgumentNullException ("password");
  87                         if (saltSize < 0)
  88                                 throw new ArgumentOutOfRangeException ("invalid salt length");
  89
  90                         Salt = KeyBuilder.Key (saltSize);
  91                         IterationCount = iterations;
  92                         _hmac = new HMACSHA1 (Encoding.UTF8.GetBytes (password));
  93                 }
  94
  95                 // properties
  96
  97                 public int IterationCount {
  98                         get { return _iteration; }
  99                         set {
 100                                 if (value < 1)
 101                                         throw new ArgumentOutOfRangeException ("IterationCount < 1");
 102
 103                                 _iteration = value;
 104                         }
 105                 }
 106
 107                 public byte[] Salt {
 108                         get { return (byte[]) _salt.Clone (); }
 109                         set {
 110                                 if (value == null)
 111                                         throw new ArgumentNullException ("Salt");
 112                                 if (value.Length < 8)
 113                                         throw new ArgumentException ("Salt < 8 bytes");
 114
 115                                 _salt = (byte[])value.Clone ();
 116                         }
 117                 }
 118
 119                 // methods
 120
 121                 private byte[] F (byte[] s, int c, int i)
 122                 {
 123                         byte[] data = new byte [s.Length + 4];
 124                         Buffer.BlockCopy (s, 0, data, 0, s.Length);
 125                         byte[] int4 = BitConverter.GetBytes (i);
 126                         Array.Reverse (int4, 0, 4);
 127                         Buffer.BlockCopy (int4, 0, data, s.Length, 4);
 128
 129                         // this is like j=0
 130                         byte[] u1 = _hmac.ComputeHash (data);
 131                         data = u1;
 132                         // so we start at j=1
 133                         for (int j=1; j < c; j++) {
 134                                 byte[] un = _hmac.ComputeHash (data);
 135                                 // xor
 136                                 for (int k=0; k < 20; k++)
 137                                         u1 [k] = (byte)(u1 [k] ^ un [k]);
 138                                 data = un;
 139                         }
 140                         return u1;
 141                 }
 142
 143                 public override byte[] GetBytes (int cb)
 144                 {
 145                         if (cb < 1)
 146                                 throw new ArgumentOutOfRangeException ("cb");
 147
 148                         int l = cb / 20;        // HMACSHA1 == 160 bits == 20 bytes
 149                         int r = cb % 20;        // remainder
 150                         if (r != 0)
 151                                 l++;            // rounding up
 152
 153                         byte[] result = new byte [cb];
 154                         int rpos = 0;
 155                         if (_pos > 0) {
 156                                 int count = Math.Min (20 - _pos, cb);
 157                                 Buffer.BlockCopy (_buffer, _pos, result, 0, count);
 158                                 if (count >= cb)
 159                                         return result;
 160                                 _pos = 0;
 161                                 rpos = 20 - cb;
 162                                 r = cb - rpos;
 163                         }
 164
 165                         for (int i=1; i <= l; i++) {
 166                                 _buffer = F (_salt, _iteration, ++_f);
 167                                 int count = ((i == l) ? r : 20);
 168                                 Buffer.BlockCopy (_buffer, _pos, result, rpos, count);
 169                                 rpos += _pos + count;
 170                                 _pos = ((count == 20) ? 0 : count);
 171                         }
 172
 173                         return result;
 174                 }
 175
 176                 public override void Reset ()
 177                 {
 178                         _buffer = null;
 179                         _pos = 0;
 180                         _f = 0;
 181                 }
 182         }
 183 }
 184
 185 #endif