mcs/class/Mono.Security/Mono.Security.Cryptography/ARC4Managed.cs

   1 //
   2 // ARC4Managed.cs: Alleged RC4(tm) compatible symmetric stream cipher
   3 //      RC4 is a trademark of RSA Security
   4 //
   5
   6 //
   7 // Permission is hereby granted, free of charge, to any person obtaining
   8 // a copy of this software and associated documentation files (the
   9 // "Software"), to deal in the Software without restriction, including
  10 // without limitation the rights to use, copy, modify, merge, publish,
  11 // distribute, sublicense, and/or sell copies of the Software, and to
  12 // permit persons to whom the Software is furnished to do so, subject to
  13 // the following conditions:
  14 //
  15 // The above copyright notice and this permission notice shall be
  16 // included in all copies or substantial portions of the Software.
  17 //
  18 // THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
  19 // EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
  20 // MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
  21 // NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE
  22 // LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION
  23 // OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION
  24 // WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
  25 //
  26
  27 using System;
  28 using System.Globalization;
  29 using System.Security.Cryptography;
  30
  31 namespace Mono.Security.Cryptography {
  32
  33         // References:
  34         // a.   Usenet 1994 - RC4 Algorithm revealed
  35         //      http://www.qrst.de/html/dsds/rc4.htm
  36
  37         public class ARC4Managed : RC4, ICryptoTransform {
  38
  39                 private byte[] key;
  40                 private byte[] state;
  41                 private byte x;
  42                 private byte y;
  43                 private bool m_disposed;
  44
  45                 public ARC4Managed () : base ()
  46                 {
  47                         state = new byte [256];
  48                         m_disposed = false;
  49                 }
  50
  51                 ~ARC4Managed ()
  52                 {
  53                         Dispose (true);
  54                 }
  55
  56                 protected override void Dispose (bool disposing)
  57                 {
  58                         if (!m_disposed) {
  59                                 x = 0;
  60                                 y = 0;
  61                                 if (key != null) {
  62                                         Array.Clear (key, 0, key.Length);
  63                                         key = null;
  64                                 }
  65                                 Array.Clear (state, 0, state.Length);
  66                                 state = null;
  67                                 GC.SuppressFinalize (this);
  68                                 m_disposed = true;
  69                         }
  70                 }
  71
  72                 public override byte[] Key {
  73                         get {
  74                                 if (KeyValue == null)
  75                                         GenerateKey ();
  76                                 return (byte[]) KeyValue.Clone ();
  77                         }
  78                         set {
  79                                 if (value == null)
  80                                         throw new ArgumentNullException ("Key");
  81                                 KeyValue = key = (byte[]) value.Clone ();
  82                                 KeySetup (key);
  83                         }
  84                 }
  85
  86                 public bool CanReuseTransform {
  87                         get { return false; }
  88                 }
  89
  90                 public override ICryptoTransform CreateEncryptor (byte[] rgbKey, byte[] rgvIV)
  91                 {
  92                         Key = rgbKey;
  93                         return (ICryptoTransform) this;
  94                 }
  95
  96                 public override ICryptoTransform CreateDecryptor (byte[] rgbKey, byte[] rgvIV)
  97                 {
  98                         Key = rgbKey;
  99                         return CreateEncryptor ();
 100                 }
 101
 102                 public override void GenerateIV ()
 103                 {
 104                         // not used for a stream cipher
 105                         IV = new byte [0];
 106                 }
 107
 108                 public override void GenerateKey ()
 109                 {
 110                         KeyValue = KeyBuilder.Key (KeySizeValue >> 3);
 111                 }
 112
 113                 public bool CanTransformMultipleBlocks {
 114                         get { return true; }
 115                 }
 116
 117                 public int InputBlockSize {
 118                         get { return 1; }
 119                 }
 120
 121                 public int OutputBlockSize {
 122                         get { return 1; }
 123                 }
 124
 125                 private void KeySetup (byte[] key)
 126                 {
 127                         byte index1 = 0;
 128                         byte index2 = 0;
 129
 130                         for (int counter = 0; counter < 256; counter++)
 131                                 state [counter] = (byte) counter;
 132                         x = 0;
 133                         y = 0;
 134                         for (int counter = 0; counter < 256; counter++) {
 135                                 index2 = (byte) (key [index1] + state [counter] + index2);
 136                                 // swap byte
 137                                 byte tmp = state [counter];
 138                                 state [counter] = state [index2];
 139                                 state [index2] = tmp;
 140                                 index1 = (byte) ((index1 + 1) % key.Length);
 141                         }
 142                 }
 143
 144                 private void CheckInput (byte[] inputBuffer, int inputOffset, int inputCount)
 145                 {
 146                         if (inputBuffer == null)
 147                                 throw new ArgumentNullException ("inputBuffer");
 148                         if (inputOffset < 0)
 149                                 throw new ArgumentOutOfRangeException ("inputOffset", "< 0");
 150                         if (inputCount < 0)
 151                                 throw new ArgumentOutOfRangeException ("inputCount", "< 0");
 152                         // ordered to avoid possible integer overflow
 153                         if (inputOffset > inputBuffer.Length - inputCount)
 154                                 throw new ArgumentException ("inputBuffer", Locale.GetText ("Overflow"));
 155                 }
 156
 157                 public int TransformBlock (byte[] inputBuffer, int inputOffset, int inputCount, byte[] outputBuffer, int outputOffset)
 158                 {
 159                         CheckInput (inputBuffer, inputOffset, inputCount);
 160                         // check output parameters
 161                         if (outputBuffer == null)
 162                                 throw new ArgumentNullException ("outputBuffer");
 163                         if (outputOffset < 0)
 164                                 throw new ArgumentOutOfRangeException ("outputOffset", "< 0");
 165                         // ordered to avoid possible integer overflow
 166                         if (outputOffset > outputBuffer.Length - inputCount)
 167                                 throw new ArgumentException ("outputBuffer", Locale.GetText ("Overflow"));
 168
 169                         return InternalTransformBlock (inputBuffer, inputOffset, inputCount, outputBuffer, outputOffset);
 170                 }
 171
 172                 private int InternalTransformBlock (byte[] inputBuffer, int inputOffset, int inputCount, byte[] outputBuffer, int outputOffset)
 173                 {
 174                         byte xorIndex;
 175                         for (int counter = 0; counter < inputCount; counter ++) {
 176                                 x = (byte) (x + 1);
 177                                 y = (byte) (state [x] + y);
 178                                 // swap byte
 179                                 byte tmp = state [x];
 180                                 state [x] = state [y];
 181                                 state [y] = tmp;
 182
 183                                 xorIndex = (byte) (state [x] + state [y]);
 184                                 outputBuffer [outputOffset + counter] = (byte) (inputBuffer [inputOffset + counter] ^ state [xorIndex]);
 185                         }
 186                         return inputCount;
 187                 }
 188
 189                 public byte[] TransformFinalBlock (byte[] inputBuffer, int inputOffset, int inputCount)
 190                 {
 191                         CheckInput (inputBuffer, inputOffset, inputCount);
 192
 193                         byte[] output = new byte [inputCount];
 194                         InternalTransformBlock (inputBuffer, inputOffset, inputCount, output, 0);
 195                         return output;
 196                 }
 197         }
 198 }