mcs/class/corlib/Mono.Security.Cryptography/SymmetricTransform.cs

   1 //
   2 // Mono.Security.Cryptography.SymmetricTransform implementation
   3 //
   4 // Authors:
   5 //      Thomas Neidhart (tome@sbox.tugraz.at)
   6 //      Sebastien Pouliot <sebastien@ximian.com>
   7 //
   8 // Portions (C) 2002, 2003 Motus Technologies Inc. (http://www.motus.com)
   9 // Copyright (C) 2004-2008 Novell, Inc (http://www.novell.com)
  10 //
  11 // Permission is hereby granted, free of charge, to any person obtaining
  12 // a copy of this software and associated documentation files (the
  13 // "Software"), to deal in the Software without restriction, including
  14 // without limitation the rights to use, copy, modify, merge, publish,
  15 // distribute, sublicense, and/or sell copies of the Software, and to
  16 // permit persons to whom the Software is furnished to do so, subject to
  17 // the following conditions:
  18 //
  19 // The above copyright notice and this permission notice shall be
  20 // included in all copies or substantial portions of the Software.
  21 //
  22 // THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
  23 // EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
  24 // MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
  25 // NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE
  26 // LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION
  27 // OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION
  28 // WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
  29 //
  30
  31 using System;
  32 using System.Security.Cryptography;
  33
  34 namespace Mono.Security.Cryptography {
  35
  36         // This class implement most of the common code required for symmetric
  37         // algorithm transforms, like:
  38         // - CipherMode: Builds CBC and CFB on top of (descendant supplied) ECB
  39         // - PaddingMode, transform properties, multiple blocks, reuse...
  40         //
  41         // Descendants MUST:
  42         // - intialize themselves (like key expansion, ...)
  43         // - override the ECB (Electronic Code Book) method which will only be
  44         //   called using BlockSize byte[] array.
  45         internal abstract class SymmetricTransform : ICryptoTransform {
  46                 protected SymmetricAlgorithm algo;
  47                 protected bool encrypt;
  48                 private int BlockSizeByte;
  49                 private byte[] temp;
  50                 private byte[] temp2;
  51                 private byte[] workBuff;
  52                 private byte[] workout;
  53                 private int FeedBackByte;
  54                 private int FeedBackIter;
  55                 private bool m_disposed = false;
  56                 private bool lastBlock;
  57
  58                 public SymmetricTransform (SymmetricAlgorithm symmAlgo, bool encryption, byte[] rgbIV)
  59                 {
  60                         algo = symmAlgo;
  61                         encrypt = encryption;
  62                         BlockSizeByte = (algo.BlockSize >> 3);
  63
  64                         if (rgbIV == null) {
  65                                 rgbIV = KeyBuilder.IV (BlockSizeByte);
  66                         } else {
  67                                 rgbIV = (byte[]) rgbIV.Clone ();
  68                         }
  69 #if NET_2_0
  70                         // compare the IV length with the "currently selected" block size and *ignore* IV that are too big
  71                         if (rgbIV.Length < BlockSizeByte) {
  72                                 string msg = Locale.GetText ("IV is too small ({0} bytes), it should be {1} bytes long.",
  73                                         rgbIV.Length, BlockSizeByte);
  74                                 throw new CryptographicException (msg);
  75                         }
  76 #endif
  77                         // mode buffers
  78                         temp = new byte [BlockSizeByte];
  79                         Buffer.BlockCopy (rgbIV, 0, temp, 0, System.Math.Min (BlockSizeByte, rgbIV.Length));
  80                         temp2 = new byte [BlockSizeByte];
  81                         FeedBackByte = (algo.FeedbackSize >> 3);
  82                         if (FeedBackByte != 0)
  83                                 FeedBackIter = (int) BlockSizeByte / FeedBackByte;
  84                         // transform buffers
  85                         workBuff = new byte [BlockSizeByte];
  86                         workout =  new byte [BlockSizeByte];
  87                 }
  88
  89                 ~SymmetricTransform ()
  90                 {
  91                         Dispose (false);
  92                 }
  93
  94                 void IDisposable.Dispose ()
  95                 {
  96                         Dispose (true);
  97                         GC.SuppressFinalize (this);  // Finalization is now unnecessary
  98                 }
  99
 100                 // MUST be overriden by classes using unmanaged ressources
 101                 // the override method must call the base class
 102                 protected virtual void Dispose (bool disposing)
 103                 {
 104                         if (!m_disposed) {
 105                                 if (disposing) {
 106                                         // dispose managed object: zeroize and free
 107                                         Array.Clear (temp, 0, BlockSizeByte);
 108                                         temp = null;
 109                                         Array.Clear (temp2, 0, BlockSizeByte);
 110                                         temp2 = null;
 111                                 }
 112                                 m_disposed = true;
 113                         }
 114                 }
 115
 116                 public virtual bool CanTransformMultipleBlocks {
 117                         get { return true; }
 118                 }
 119
 120                 public virtual bool CanReuseTransform {
 121                         get { return false; }
 122                 }
 123
 124                 public virtual int InputBlockSize {
 125                         get { return BlockSizeByte; }
 126                 }
 127
 128                 public virtual int OutputBlockSize {
 129                         get { return BlockSizeByte; }
 130                 }
 131
 132                 // note: Each block MUST be BlockSizeValue in size!!!
 133                 // i.e. Any padding must be done before calling this method
 134                 protected virtual void Transform (byte[] input, byte[] output)
 135                 {
 136                         switch (algo.Mode) {
 137                         case CipherMode.ECB:
 138                                 ECB (input, output);
 139                                 break;
 140                         case CipherMode.CBC:
 141                                 CBC (input, output);
 142                                 break;
 143                         case CipherMode.CFB:
 144                                 CFB (input, output);
 145                                 break;
 146                         case CipherMode.OFB:
 147                                 OFB (input, output);
 148                                 break;
 149                         case CipherMode.CTS:
 150                                 CTS (input, output);
 151                                 break;
 152                         default:
 153                                 throw new NotImplementedException ("Unkown CipherMode" + algo.Mode.ToString ());
 154                         }
 155                 }
 156
 157                 // Electronic Code Book (ECB)
 158                 protected abstract void ECB (byte[] input, byte[] output);
 159
 160                 // Cipher-Block-Chaining (CBC)
 161                 protected virtual void CBC (byte[] input, byte[] output)
 162                 {
 163                         if (encrypt) {
 164                                 for (int i = 0; i < BlockSizeByte; i++)
 165                                         temp[i] ^= input[i];
 166                                 ECB (temp, output);
 167                                 Buffer.BlockCopy (output, 0, temp, 0, BlockSizeByte);
 168                         }
 169                         else {
 170                                 Buffer.BlockCopy (input, 0, temp2, 0, BlockSizeByte);
 171                                 ECB (input, output);
 172                                 for (int i = 0; i < BlockSizeByte; i++)
 173                                         output[i] ^= temp[i];
 174                                 Buffer.BlockCopy (temp2, 0, temp, 0, BlockSizeByte);
 175                         }
 176                 }
 177
 178                 // Cipher-FeedBack (CFB)
 179                 protected virtual void CFB (byte[] input, byte[] output)
 180                 {
 181                         if (encrypt) {
 182                                 for (int x = 0; x < FeedBackIter; x++) {
 183                                         // temp is first initialized with the IV
 184                                         ECB (temp, temp2);
 185
 186                                         for (int i = 0; i < FeedBackByte; i++)
 187                                                 output[i + x] = (byte)(temp2[i] ^ input[i + x]);
 188                                         Buffer.BlockCopy (temp, FeedBackByte, temp, 0, BlockSizeByte - FeedBackByte);
 189                                         Buffer.BlockCopy (output, x, temp, BlockSizeByte - FeedBackByte, FeedBackByte);
 190                                 }
 191                         }
 192                         else {
 193                                 for (int x = 0; x < FeedBackIter; x++) {
 194                                         // we do not really decrypt this data!
 195                                         encrypt = true;
 196                                         // temp is first initialized with the IV
 197                                         ECB (temp, temp2);
 198                                         encrypt = false;
 199
 200                                         Buffer.BlockCopy (temp, FeedBackByte, temp, 0, BlockSizeByte - FeedBackByte);
 201                                         Buffer.BlockCopy (input, x, temp, BlockSizeByte - FeedBackByte, FeedBackByte);
 202                                         for (int i = 0; i < FeedBackByte; i++)
 203                                                 output[i + x] = (byte)(temp2[i] ^ input[i + x]);
 204                                 }
 205                         }
 206                 }
 207
 208                 // Output-FeedBack (OFB)
 209                 protected virtual void OFB (byte[] input, byte[] output)
 210                 {
 211                         throw new CryptographicException ("OFB isn't supported by the framework");
 212                 }
 213
 214                 // Cipher Text Stealing (CTS)
 215                 protected virtual void CTS (byte[] input, byte[] output)
 216                 {
 217                         throw new CryptographicException ("CTS isn't supported by the framework");
 218                 }
 219
 220                 private void CheckInput (byte[] inputBuffer, int inputOffset, int inputCount)
 221                 {
 222                         if (inputBuffer == null)
 223                                 throw new ArgumentNullException ("inputBuffer");
 224                         if (inputOffset < 0)
 225                                 throw new ArgumentOutOfRangeException ("inputOffset", "< 0");
 226                         if (inputCount < 0)
 227                                 throw new ArgumentOutOfRangeException ("inputCount", "< 0");
 228                         // ordered to avoid possible integer overflow
 229                         if (inputOffset > inputBuffer.Length - inputCount)
 230                                 throw new ArgumentException ("inputBuffer", Locale.GetText ("Overflow"));
 231                 }
 232
 233                 // this method may get called MANY times so this is the one to optimize
 234                 public virtual int TransformBlock (byte[] inputBuffer, int inputOffset, int inputCount, byte[] outputBuffer, int outputOffset)
 235                 {
 236                         if (m_disposed)
 237                                 throw new ObjectDisposedException ("Object is disposed");
 238                         CheckInput (inputBuffer, inputOffset, inputCount);
 239                         // check output parameters
 240                         if (outputBuffer == null)
 241                                 throw new ArgumentNullException ("outputBuffer");
 242                         if (outputOffset < 0)
 243                                 throw new ArgumentOutOfRangeException ("outputOffset", "< 0");
 244
 245                         // ordered to avoid possible integer overflow
 246                         int len = outputBuffer.Length - inputCount - outputOffset;
 247                         if (!encrypt && (0 > len) && ((algo.Padding == PaddingMode.None) || (algo.Padding == PaddingMode.Zeros))) {
 248                                 throw new CryptographicException ("outputBuffer", Locale.GetText ("Overflow"));
 249                         } else  if (KeepLastBlock) {
 250                                 if (0 > len + BlockSizeByte) {
 251 #if NET_2_0
 252                                         throw new CryptographicException ("outputBuffer", Locale.GetText ("Overflow"));
 253 #else
 254                                         throw new IndexOutOfRangeException (Locale.GetText ("Overflow"));
 255 #endif
 256                                 }
 257                         } else {
 258                                 if (0 > len) {
 259                                         // there's a special case if this is the end of the decryption process
 260                                         if (inputBuffer.Length - inputOffset - outputBuffer.Length == BlockSizeByte)
 261                                                 inputCount = outputBuffer.Length - outputOffset;
 262                                         else
 263                                                 throw new CryptographicException ("outputBuffer", Locale.GetText ("Overflow"));
 264                                 }
 265                         }
 266                         return InternalTransformBlock (inputBuffer, inputOffset, inputCount, outputBuffer, outputOffset);
 267                 }
 268
 269                 private bool KeepLastBlock {
 270                         get {
 271                                 return ((!encrypt) && (algo.Padding != PaddingMode.None) && (algo.Padding != PaddingMode.Zeros));
 272                         }
 273                 }
 274
 275                 private int InternalTransformBlock (byte[] inputBuffer, int inputOffset, int inputCount, byte[] outputBuffer, int outputOffset)
 276                 {
 277                         int offs = inputOffset;
 278                         int full;
 279
 280                         // this way we don't do a modulo every time we're called
 281                         // and we may save a division
 282                         if (inputCount != BlockSizeByte) {
 283                                 if ((inputCount % BlockSizeByte) != 0)
 284                                         throw new CryptographicException ("Invalid input block size.");
 285
 286                                 full = inputCount / BlockSizeByte;
 287                         }
 288                         else
 289                                 full = 1;
 290
 291                         if (KeepLastBlock)
 292                                 full--;
 293
 294                         int total = 0;
 295
 296                         if (lastBlock) {
 297                                 Transform (workBuff, workout);
 298                                 Buffer.BlockCopy (workout, 0, outputBuffer, outputOffset, BlockSizeByte);
 299                                 outputOffset += BlockSizeByte;
 300                                 total += BlockSizeByte;
 301                                 lastBlock = false;
 302                         }
 303
 304                         for (int i = 0; i < full; i++) {
 305                                 Buffer.BlockCopy (inputBuffer, offs, workBuff, 0, BlockSizeByte);
 306                                 Transform (workBuff, workout);
 307                                 Buffer.BlockCopy (workout, 0, outputBuffer, outputOffset, BlockSizeByte);
 308                                 offs += BlockSizeByte;
 309                                 outputOffset += BlockSizeByte;
 310                                 total += BlockSizeByte;
 311                         }
 312
 313                         if (KeepLastBlock) {
 314                                 Buffer.BlockCopy (inputBuffer, offs, workBuff, 0, BlockSizeByte);
 315                                 lastBlock = true;
 316                         }
 317
 318                         return total;
 319                 }
 320
 321 #if NET_2_0
 322                 RandomNumberGenerator _rng;
 323
 324                 private void Random (byte[] buffer, int start, int length)
 325                 {
 326                         if (_rng == null) {
 327                                 _rng = RandomNumberGenerator.Create ();
 328                         }
 329                         byte[] random = new byte [length];
 330                         _rng.GetBytes (random);
 331                         Buffer.BlockCopy (random, 0, buffer, start, length);
 332                 }
 333
 334                 private void ThrowBadPaddingException (PaddingMode padding, int length, int position)
 335                 {
 336                         string msg = String.Format (Locale.GetText ("Bad {0} padding."), padding);
 337                         if (length >= 0)
 338                                 msg += String.Format (Locale.GetText (" Invalid length {0}."), length);
 339                         if (position >= 0)
 340                                 msg += String.Format (Locale.GetText (" Error found at position {0}."), position);
 341                         throw new CryptographicException (msg);
 342                 }
 343 #endif
 344
 345                 private byte[] FinalEncrypt (byte[] inputBuffer, int inputOffset, int inputCount)
 346                 {
 347                         // are there still full block to process ?
 348                         int full = (inputCount / BlockSizeByte) * BlockSizeByte;
 349                         int rem = inputCount - full;
 350                         int total = full;
 351
 352                         switch (algo.Padding) {
 353 #if NET_2_0
 354                         case PaddingMode.ANSIX923:
 355                         case PaddingMode.ISO10126:
 356 #endif
 357                         case PaddingMode.PKCS7:
 358                                 // we need to add an extra block for padding
 359                                 total += BlockSizeByte;
 360                                 break;
 361                         default:
 362                                 if (inputCount == 0)
 363                                         return new byte [0];
 364                                 if (rem != 0) {
 365                                         if (algo.Padding == PaddingMode.None)
 366                                                 throw new CryptographicException ("invalid block length");
 367                                         // zero padding the input (by adding a block for the partial data)
 368                                         byte[] paddedInput = new byte [full + BlockSizeByte];
 369                                         Buffer.BlockCopy (inputBuffer, inputOffset, paddedInput, 0, inputCount);
 370                                         inputBuffer = paddedInput;
 371                                         inputOffset = 0;
 372                                         inputCount = paddedInput.Length;
 373                                         total = inputCount;
 374                                 }
 375                                 break;
 376                         }
 377
 378                         byte[] res = new byte [total];
 379                         int outputOffset = 0;
 380
 381                         // process all blocks except the last (final) block
 382                         while (total > BlockSizeByte) {
 383                                 InternalTransformBlock (inputBuffer, inputOffset, BlockSizeByte, res, outputOffset);
 384                                 inputOffset += BlockSizeByte;
 385                                 outputOffset += BlockSizeByte;
 386                                 total -= BlockSizeByte;
 387                         }
 388
 389                         // now we only have a single last block to encrypt
 390                         byte padding = (byte) (BlockSizeByte - rem);
 391                         switch (algo.Padding) {
 392 #if NET_2_0
 393                         case PaddingMode.ANSIX923:
 394                                 // XX 00 00 00 00 00 00 07 (zero + padding length)
 395                                 res [res.Length - 1] = padding;
 396                                 Buffer.BlockCopy (inputBuffer, inputOffset, res, full, rem);
 397                                 // the last padded block will be transformed in-place
 398                                 InternalTransformBlock (res, full, BlockSizeByte, res, full);
 399                                 break;
 400                         case PaddingMode.ISO10126:
 401                                 // XX 3F 52 2A 81 AB F7 07 (random + padding length)
 402                                 Random (res, res.Length - padding, padding - 1);
 403                                 res [res.Length - 1] = padding;
 404                                 Buffer.BlockCopy (inputBuffer, inputOffset, res, full, rem);
 405                                 // the last padded block will be transformed in-place
 406                                 InternalTransformBlock (res, full, BlockSizeByte, res, full);
 407                                 break;
 408 #endif
 409                         case PaddingMode.PKCS7:
 410                                 // XX 07 07 07 07 07 07 07 (padding length)
 411                                 for (int i = res.Length; --i >= (res.Length - padding);)
 412                                         res [i] = padding;
 413                                 Buffer.BlockCopy (inputBuffer, inputOffset, res, full, rem);
 414                                 // the last padded block will be transformed in-place
 415                                 InternalTransformBlock (res, full, BlockSizeByte, res, full);
 416                                 break;
 417                         default:
 418                                 InternalTransformBlock (inputBuffer, inputOffset, BlockSizeByte, res, outputOffset);
 419                                 break;
 420                         }
 421                         return res;
 422                 }
 423
 424                 private byte[] FinalDecrypt (byte[] inputBuffer, int inputOffset, int inputCount)
 425                 {
 426                         if ((inputCount % BlockSizeByte) > 0)
 427                                 throw new CryptographicException ("Invalid input block size.");
 428
 429                         int total = inputCount;
 430                         if (lastBlock)
 431                                 total += BlockSizeByte;
 432
 433                         byte[] res = new byte [total];
 434                         int outputOffset = 0;
 435
 436                         while (inputCount > 0) {
 437                                 int len = InternalTransformBlock (inputBuffer, inputOffset, BlockSizeByte, res, outputOffset);
 438                                 inputOffset += BlockSizeByte;
 439                                 outputOffset += len;
 440                                 inputCount -= BlockSizeByte;
 441                         }
 442
 443                         if (lastBlock) {
 444                                 Transform (workBuff, workout);
 445                                 Buffer.BlockCopy (workout, 0, res, outputOffset, BlockSizeByte);
 446                                 outputOffset += BlockSizeByte;
 447                                 lastBlock = false;
 448                         }
 449
 450                         // total may be 0 (e.g. PaddingMode.None)
 451                         byte padding = ((total > 0) ? res [total - 1] : (byte) 0);
 452                         switch (algo.Padding) {
 453 #if NET_2_0
 454                         case PaddingMode.ANSIX923:
 455                                 if ((padding == 0) || (padding > BlockSizeByte))
 456                                         ThrowBadPaddingException (algo.Padding, padding, -1);
 457                                 for (int i = padding - 1; i > 0; i--) {
 458                                         if (res [total - 1 - i] != 0x00)
 459                                                 ThrowBadPaddingException (algo.Padding, -1, i);
 460                                 }
 461                                 total -= padding;
 462                                 break;
 463                         case PaddingMode.ISO10126:
 464                                 if ((padding == 0) || (padding > BlockSizeByte))
 465                                         ThrowBadPaddingException (algo.Padding, padding, -1);
 466                                 total -= padding;
 467                                 break;
 468                         case PaddingMode.PKCS7:
 469                                 if ((padding == 0) || (padding > BlockSizeByte))
 470                                         ThrowBadPaddingException (algo.Padding, padding, -1);
 471                                 for (int i = padding - 1; i > 0; i--) {
 472                                         if (res [total - 1 - i] != padding)
 473                                                 ThrowBadPaddingException (algo.Padding, -1, i);
 474                                 }
 475                                 total -= padding;
 476                                 break;
 477 #else
 478                         case PaddingMode.PKCS7:
 479                                 total -= padding;
 480                                 break;
 481 #endif
 482                         case PaddingMode.None:  // nothing to do - it's a multiple of block size
 483                         case PaddingMode.Zeros: // nothing to do - user must unpad himself
 484                                 break;
 485                         }
 486
 487                         // return output without padding
 488                         if (total > 0) {
 489                                 byte[] data = new byte [total];
 490                                 Buffer.BlockCopy (res, 0, data, 0, total);
 491                                 // zeroize decrypted data (copy with padding)
 492                                 Array.Clear (res, 0, res.Length);
 493                                 return data;
 494                         }
 495                         else
 496                                 return new byte [0];
 497                 }
 498
 499                 public virtual byte[] TransformFinalBlock (byte[] inputBuffer, int inputOffset, int inputCount)
 500                 {
 501                         if (m_disposed)
 502                                 throw new ObjectDisposedException ("Object is disposed");
 503                         CheckInput (inputBuffer, inputOffset, inputCount);
 504
 505                         if (encrypt)
 506                                 return FinalEncrypt (inputBuffer, inputOffset, inputCount);
 507                         else
 508                                 return FinalDecrypt (inputBuffer, inputOffset, inputCount);
 509                 }
 510         }
 511 }