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