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 #if INSIDE_SYSTEM
  38         internal
  39 #else
  40         public
  41 #endif
  42         class ARC4Managed : RC4, ICryptoTransform {
  43
  44                 private byte[] key;
  45                 private byte[] state;
  46                 private byte x;
  47                 private byte y;
  48                 private bool m_disposed;
  49
  50                 public ARC4Managed () : base ()
  51                 {
  52                         state = new byte [256];
  53                         m_disposed = false;
  54                 }
  55
  56                 ~ARC4Managed ()
  57                 {
  58                         Dispose (true);
  59                 }
  60
  61                 protected override void Dispose (bool disposing)
  62                 {
  63                         if (!m_disposed) {
  64                                 x = 0;
  65                                 y = 0;
  66                                 if (key != null) {
  67                                         Array.Clear (key, 0, key.Length);
  68                                         key = null;
  69                                 }
  70                                 Array.Clear (state, 0, state.Length);
  71                                 state = null;
  72                                 GC.SuppressFinalize (this);
  73                                 m_disposed = true;
  74                         }
  75                 }
  76
  77                 public override byte[] Key {
  78                         get {
  79                                 if (KeyValue == null)
  80                                         GenerateKey ();
  81                                 return (byte[]) KeyValue.Clone ();
  82                         }
  83                         set {
  84                                 if (value == null)
  85                                         throw new ArgumentNullException ("Key");
  86                                 KeyValue = key = (byte[]) value.Clone ();
  87                                 KeySetup (key);
  88                         }
  89                 }
  90
  91                 public bool CanReuseTransform {
  92                         get { return false; }
  93                 }
  94
  95                 public override ICryptoTransform CreateEncryptor (byte[] rgbKey, byte[] rgvIV)
  96                 {
  97                         Key = rgbKey;
  98                         return (ICryptoTransform) this;
  99                 }
 100
 101                 public override ICryptoTransform CreateDecryptor (byte[] rgbKey, byte[] rgvIV)
 102                 {
 103                         Key = rgbKey;
 104                         return CreateEncryptor ();
 105                 }
 106
 107                 public override void GenerateIV ()
 108                 {
 109                         // not used for a stream cipher
 110                         IV = new byte [0];
 111                 }
 112
 113                 public override void GenerateKey ()
 114                 {
 115                         KeyValue = KeyBuilder.Key (KeySizeValue >> 3);
 116                 }
 117
 118                 public bool CanTransformMultipleBlocks {
 119                         get { return true; }
 120                 }
 121
 122                 public int InputBlockSize {
 123                         get { return 1; }
 124                 }
 125
 126                 public int OutputBlockSize {
 127                         get { return 1; }
 128                 }
 129
 130                 private void KeySetup (byte[] key)
 131                 {
 132                         byte index1 = 0;
 133                         byte index2 = 0;
 134
 135                         for (int counter = 0; counter < 256; counter++)
 136                                 state [counter] = (byte) counter;
 137                         x = 0;
 138                         y = 0;
 139                         for (int counter = 0; counter < 256; counter++) {
 140                                 index2 = (byte) (key [index1] + state [counter] + index2);
 141                                 // swap byte
 142                                 byte tmp = state [counter];
 143                                 state [counter] = state [index2];
 144                                 state [index2] = tmp;
 145                                 index1 = (byte) ((index1 + 1) % key.Length);
 146                         }
 147                 }
 148
 149                 private void CheckInput (byte[] inputBuffer, int inputOffset, int inputCount)
 150                 {
 151                         if (inputBuffer == null)
 152                                 throw new ArgumentNullException ("inputBuffer");
 153                         if (inputOffset < 0)
 154                                 throw new ArgumentOutOfRangeException ("inputOffset", "< 0");
 155                         if (inputCount < 0)
 156                                 throw new ArgumentOutOfRangeException ("inputCount", "< 0");
 157                         // ordered to avoid possible integer overflow
 158                         if (inputOffset > inputBuffer.Length - inputCount)
 159                                 throw new ArgumentException ("inputBuffer", Locale.GetText ("Overflow"));
 160                 }
 161
 162                 public int TransformBlock (byte[] inputBuffer, int inputOffset, int inputCount, byte[] outputBuffer, int outputOffset)
 163                 {
 164                         CheckInput (inputBuffer, inputOffset, inputCount);
 165                         // check output parameters
 166                         if (outputBuffer == null)
 167                                 throw new ArgumentNullException ("outputBuffer");
 168                         if (outputOffset < 0)
 169                                 throw new ArgumentOutOfRangeException ("outputOffset", "< 0");
 170                         // ordered to avoid possible integer overflow
 171                         if (outputOffset > outputBuffer.Length - inputCount)
 172                                 throw new ArgumentException ("outputBuffer", Locale.GetText ("Overflow"));
 173
 174                         return InternalTransformBlock (inputBuffer, inputOffset, inputCount, outputBuffer, outputOffset);
 175                 }
 176
 177                 private int InternalTransformBlock (byte[] inputBuffer, int inputOffset, int inputCount, byte[] outputBuffer, int outputOffset)
 178                 {
 179                         byte xorIndex;
 180                         for (int counter = 0; counter < inputCount; counter ++) {
 181                                 x = (byte) (x + 1);
 182                                 y = (byte) (state [x] + y);
 183                                 // swap byte
 184                                 byte tmp = state [x];
 185                                 state [x] = state [y];
 186                                 state [y] = tmp;
 187
 188                                 xorIndex = (byte) (state [x] + state [y]);
 189                                 outputBuffer [outputOffset + counter] = (byte) (inputBuffer [inputOffset + counter] ^ state [xorIndex]);
 190                         }
 191                         return inputCount;
 192                 }
 193
 194                 public byte[] TransformFinalBlock (byte[] inputBuffer, int inputOffset, int inputCount)
 195                 {
 196                         CheckInput (inputBuffer, inputOffset, inputCount);
 197
 198                         byte[] output = new byte [inputCount];
 199                         InternalTransformBlock (inputBuffer, inputOffset, inputCount, output, 0);
 200                         return output;
 201                 }
 202         }
 203 }