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 #if !MOONLIGHT
  54                 // Silverlight 2.0 does not support any feedback mode
  55                 private int FeedBackByte;
  56                 private int FeedBackIter;
  57 #endif
  58                 private bool m_disposed = false;
  59                 private bool lastBlock;
  60
  61                 public SymmetricTransform (SymmetricAlgorithm symmAlgo, bool encryption, byte[] rgbIV)
  62                 {
  63                         algo = symmAlgo;
  64                         encrypt = encryption;
  65                         BlockSizeByte = (algo.BlockSize >> 3);
  66
  67                         if (rgbIV == null) {
  68                                 rgbIV = KeyBuilder.IV (BlockSizeByte);
  69                         } else {
  70                                 rgbIV = (byte[]) rgbIV.Clone ();
  71                         }
  72                         // compare the IV length with the "currently selected" block size and *ignore* IV that are too big
  73                         if (rgbIV.Length < BlockSizeByte) {
  74                                 string msg = Locale.GetText ("IV is too small ({0} bytes), it should be {1} bytes long.",
  75                                         rgbIV.Length, BlockSizeByte);
  76                                 throw new CryptographicException (msg);
  77                         }
  78                         // mode buffers
  79                         temp = new byte [BlockSizeByte];
  80                         Buffer.BlockCopy (rgbIV, 0, temp, 0, System.Math.Min (BlockSizeByte, rgbIV.Length));
  81                         temp2 = new byte [BlockSizeByte];
  82 #if !MOONLIGHT
  83                         FeedBackByte = (algo.FeedbackSize >> 3);
  84                         if (FeedBackByte != 0)
  85                                 FeedBackIter = (int) BlockSizeByte / FeedBackByte;
  86 #endif
  87                         // transform buffers
  88                         workBuff = new byte [BlockSizeByte];
  89                         workout =  new byte [BlockSizeByte];
  90                 }
  91
  92                 ~SymmetricTransform ()
  93                 {
  94                         Dispose (false);
  95                 }
  96
  97                 void IDisposable.Dispose ()
  98                 {
  99                         Dispose (true);
 100                         GC.SuppressFinalize (this);  // Finalization is now unnecessary
 101                 }
 102
 103                 // MUST be overriden by classes using unmanaged ressources
 104                 // the override method must call the base class
 105                 protected virtual void Dispose (bool disposing)
 106                 {
 107                         if (!m_disposed) {
 108                                 if (disposing) {
 109                                         // dispose managed object: zeroize and free
 110                                         Array.Clear (temp, 0, BlockSizeByte);
 111                                         temp = null;
 112                                         Array.Clear (temp2, 0, BlockSizeByte);
 113                                         temp2 = null;
 114                                 }
 115                                 m_disposed = true;
 116                         }
 117                 }
 118
 119                 public virtual bool CanTransformMultipleBlocks {
 120                         get { return true; }
 121                 }
 122
 123                 public virtual bool CanReuseTransform {
 124                         get { return false; }
 125                 }
 126
 127                 public virtual int InputBlockSize {
 128                         get { return BlockSizeByte; }
 129                 }
 130
 131                 public virtual int OutputBlockSize {
 132                         get { return BlockSizeByte; }
 133                 }
 134
 135                 // note: Each block MUST be BlockSizeValue in size!!!
 136                 // i.e. Any padding must be done before calling this method
 137                 protected virtual void Transform (byte[] input, byte[] output)
 138                 {
 139 #if MOONLIGHT
 140                         // Silverlight 2.0 only supports CBC
 141                         CBC (input, output);
 142 #else
 143                         switch (algo.Mode) {
 144                         case CipherMode.ECB:
 145                                 ECB (input, output);
 146                                 break;
 147                         case CipherMode.CBC:
 148                                 CBC (input, output);
 149                                 break;
 150                         case CipherMode.CFB:
 151                                 CFB (input, output);
 152                                 break;
 153                         case CipherMode.OFB:
 154                                 OFB (input, output);
 155                                 break;
 156                         case CipherMode.CTS:
 157                                 CTS (input, output);
 158                                 break;
 159                         default:
 160                                 throw new NotImplementedException ("Unkown CipherMode" + algo.Mode.ToString ());
 161                         }
 162 #endif
 163                 }
 164
 165                 // Electronic Code Book (ECB)
 166                 protected abstract void ECB (byte[] input, byte[] output);
 167
 168                 // Cipher-Block-Chaining (CBC)
 169                 protected virtual void CBC (byte[] input, byte[] output)
 170                 {
 171                         if (encrypt) {
 172                                 for (int i = 0; i < BlockSizeByte; i++)
 173                                         temp[i] ^= input[i];
 174                                 ECB (temp, output);
 175                                 Buffer.BlockCopy (output, 0, temp, 0, BlockSizeByte);
 176                         }
 177                         else {
 178                                 Buffer.BlockCopy (input, 0, temp2, 0, BlockSizeByte);
 179                                 ECB (input, output);
 180                                 for (int i = 0; i < BlockSizeByte; i++)
 181                                         output[i] ^= temp[i];
 182                                 Buffer.BlockCopy (temp2, 0, temp, 0, BlockSizeByte);
 183                         }
 184                 }
 185
 186 #if !MOONLIGHT
 187                 // Cipher-FeedBack (CFB)
 188                 protected virtual void CFB (byte[] input, byte[] output)
 189                 {
 190                         if (encrypt) {
 191                                 for (int x = 0; x < FeedBackIter; x++) {
 192                                         // temp is first initialized with the IV
 193                                         ECB (temp, temp2);
 194
 195                                         for (int i = 0; i < FeedBackByte; i++)
 196                                                 output[i + x] = (byte)(temp2[i] ^ input[i + x]);
 197                                         Buffer.BlockCopy (temp, FeedBackByte, temp, 0, BlockSizeByte - FeedBackByte);
 198                                         Buffer.BlockCopy (output, x, temp, BlockSizeByte - FeedBackByte, FeedBackByte);
 199                                 }
 200                         }
 201                         else {
 202                                 for (int x = 0; x < FeedBackIter; x++) {
 203                                         // we do not really decrypt this data!
 204                                         encrypt = true;
 205                                         // temp is first initialized with the IV
 206                                         ECB (temp, temp2);
 207                                         encrypt = false;
 208
 209                                         Buffer.BlockCopy (temp, FeedBackByte, temp, 0, BlockSizeByte - FeedBackByte);
 210                                         Buffer.BlockCopy (input, x, temp, BlockSizeByte - FeedBackByte, FeedBackByte);
 211                                         for (int i = 0; i < FeedBackByte; i++)
 212                                                 output[i + x] = (byte)(temp2[i] ^ input[i + x]);
 213                                 }
 214                         }
 215                 }
 216
 217                 // Output-FeedBack (OFB)
 218                 protected virtual void OFB (byte[] input, byte[] output)
 219                 {
 220                         throw new CryptographicException ("OFB isn't supported by the framework");
 221                 }
 222
 223                 // Cipher Text Stealing (CTS)
 224                 protected virtual void CTS (byte[] input, byte[] output)
 225                 {
 226                         throw new CryptographicException ("CTS isn't supported by the framework");
 227                 }
 228 #endif
 229
 230                 private void CheckInput (byte[] inputBuffer, int inputOffset, int inputCount)
 231                 {
 232                         if (inputBuffer == null)
 233                                 throw new ArgumentNullException ("inputBuffer");
 234                         if (inputOffset < 0)
 235                                 throw new ArgumentOutOfRangeException ("inputOffset", "< 0");
 236                         if (inputCount < 0)
 237                                 throw new ArgumentOutOfRangeException ("inputCount", "< 0");
 238                         // ordered to avoid possible integer overflow
 239                         if (inputOffset > inputBuffer.Length - inputCount)
 240                                 throw new ArgumentException ("inputBuffer", Locale.GetText ("Overflow"));
 241                 }
 242
 243                 // this method may get called MANY times so this is the one to optimize
 244                 public virtual int TransformBlock (byte[] inputBuffer, int inputOffset, int inputCount, byte[] outputBuffer, int outputOffset)
 245                 {
 246                         if (m_disposed)
 247                                 throw new ObjectDisposedException ("Object is disposed");
 248                         CheckInput (inputBuffer, inputOffset, inputCount);
 249                         // check output parameters
 250                         if (outputBuffer == null)
 251                                 throw new ArgumentNullException ("outputBuffer");
 252                         if (outputOffset < 0)
 253                                 throw new ArgumentOutOfRangeException ("outputOffset", "< 0");
 254
 255                         // ordered to avoid possible integer overflow
 256                         int len = outputBuffer.Length - inputCount - outputOffset;
 257 #if MOONLIGHT
 258                         // only PKCS7 is supported Silverlight 2.0
 259                         if (KeepLastBlock) {
 260 #else
 261                         if (!encrypt && (0 > len) && ((algo.Padding == PaddingMode.None) || (algo.Padding == PaddingMode.Zeros))) {
 262                                 throw new CryptographicException ("outputBuffer", Locale.GetText ("Overflow"));
 263                         } else if (KeepLastBlock) {
 264 #endif
 265                                 if (0 > len + BlockSizeByte) {
 266                                         throw new CryptographicException ("outputBuffer", Locale.GetText ("Overflow"));
 267                                 }
 268                         } else {
 269                                 if (0 > len) {
 270                                         // there's a special case if this is the end of the decryption process
 271                                         if (inputBuffer.Length - inputOffset - outputBuffer.Length == BlockSizeByte)
 272                                                 inputCount = outputBuffer.Length - outputOffset;
 273                                         else
 274                                                 throw new CryptographicException ("outputBuffer", Locale.GetText ("Overflow"));
 275                                 }
 276                         }
 277                         return InternalTransformBlock (inputBuffer, inputOffset, inputCount, outputBuffer, outputOffset);
 278                 }
 279
 280                 private bool KeepLastBlock {
 281                         get {
 282 #if MOONLIGHT
 283                                 // only PKCS7 is supported Silverlight 2.0
 284                                 return !encrypt;
 285 #else
 286                                 return ((!encrypt) && (algo.Padding != PaddingMode.None) && (algo.Padding != PaddingMode.Zeros));
 287 #endif
 288                         }
 289                 }
 290
 291                 private int InternalTransformBlock (byte[] inputBuffer, int inputOffset, int inputCount, byte[] outputBuffer, int outputOffset)
 292                 {
 293                         int offs = inputOffset;
 294                         int full;
 295
 296                         // this way we don't do a modulo every time we're called
 297                         // and we may save a division
 298                         if (inputCount != BlockSizeByte) {
 299                                 if ((inputCount % BlockSizeByte) != 0)
 300                                         throw new CryptographicException ("Invalid input block size.");
 301
 302                                 full = inputCount / BlockSizeByte;
 303                         }
 304                         else
 305                                 full = 1;
 306
 307                         if (KeepLastBlock)
 308                                 full--;
 309
 310                         int total = 0;
 311
 312                         if (lastBlock) {
 313                                 Transform (workBuff, workout);
 314                                 Buffer.BlockCopy (workout, 0, outputBuffer, outputOffset, BlockSizeByte);
 315                                 outputOffset += BlockSizeByte;
 316                                 total += BlockSizeByte;
 317                                 lastBlock = false;
 318                         }
 319
 320                         for (int i = 0; i < full; i++) {
 321                                 Buffer.BlockCopy (inputBuffer, offs, workBuff, 0, BlockSizeByte);
 322                                 Transform (workBuff, workout);
 323                                 Buffer.BlockCopy (workout, 0, outputBuffer, outputOffset, BlockSizeByte);
 324                                 offs += BlockSizeByte;
 325                                 outputOffset += BlockSizeByte;
 326                                 total += BlockSizeByte;
 327                         }
 328
 329                         if (KeepLastBlock) {
 330                                 Buffer.BlockCopy (inputBuffer, offs, workBuff, 0, BlockSizeByte);
 331                                 lastBlock = true;
 332                         }
 333
 334                         return total;
 335                 }
 336
 337 #if !MOONLIGHT
 338                 RandomNumberGenerator _rng;
 339
 340                 private void Random (byte[] buffer, int start, int length)
 341                 {
 342                         if (_rng == null) {
 343                                 _rng = RandomNumberGenerator.Create ();
 344                         }
 345                         byte[] random = new byte [length];
 346                         _rng.GetBytes (random);
 347                         Buffer.BlockCopy (random, 0, buffer, start, length);
 348                 }
 349
 350                 private void ThrowBadPaddingException (PaddingMode padding, int length, int position)
 351                 {
 352                         string msg = String.Format (Locale.GetText ("Bad {0} padding."), padding);
 353                         if (length >= 0)
 354                                 msg += String.Format (Locale.GetText (" Invalid length {0}."), length);
 355                         if (position >= 0)
 356                                 msg += String.Format (Locale.GetText (" Error found at position {0}."), position);
 357                         throw new CryptographicException (msg);
 358                 }
 359 #endif
 360
 361                 private byte[] FinalEncrypt (byte[] inputBuffer, int inputOffset, int inputCount)
 362                 {
 363                         // are there still full block to process ?
 364                         int full = (inputCount / BlockSizeByte) * BlockSizeByte;
 365                         int rem = inputCount - full;
 366                         int total = full;
 367
 368 #if MOONLIGHT
 369                         // only PKCS7 is supported Silverlight 2.0
 370                         total += BlockSizeByte;
 371 #else
 372                         switch (algo.Padding) {
 373                         case PaddingMode.ANSIX923:
 374                         case PaddingMode.ISO10126:
 375                         case PaddingMode.PKCS7:
 376                                 // we need to add an extra block for padding
 377                                 total += BlockSizeByte;
 378                                 break;
 379                         default:
 380                                 if (inputCount == 0)
 381                                         return new byte [0];
 382                                 if (rem != 0) {
 383                                         if (algo.Padding == PaddingMode.None)
 384                                                 throw new CryptographicException ("invalid block length");
 385                                         // zero padding the input (by adding a block for the partial data)
 386                                         byte[] paddedInput = new byte [full + BlockSizeByte];
 387                                         Buffer.BlockCopy (inputBuffer, inputOffset, paddedInput, 0, inputCount);
 388                                         inputBuffer = paddedInput;
 389                                         inputOffset = 0;
 390                                         inputCount = paddedInput.Length;
 391                                         total = inputCount;
 392                                 }
 393                                 break;
 394                         }
 395 #endif // NET_2_1
 396
 397                         byte[] res = new byte [total];
 398                         int outputOffset = 0;
 399
 400                         // process all blocks except the last (final) block
 401                         while (total > BlockSizeByte) {
 402                                 InternalTransformBlock (inputBuffer, inputOffset, BlockSizeByte, res, outputOffset);
 403                                 inputOffset += BlockSizeByte;
 404                                 outputOffset += BlockSizeByte;
 405                                 total -= BlockSizeByte;
 406                         }
 407
 408                         // now we only have a single last block to encrypt
 409                         byte padding = (byte) (BlockSizeByte - rem);
 410 #if MOONLIGHT
 411                         // only PKCS7 is supported Silverlight 2.0
 412                         for (int i = res.Length; --i >= (res.Length - padding);)
 413                                 res [i] = padding;
 414                         Buffer.BlockCopy (inputBuffer, inputOffset, res, full, rem);
 415                         InternalTransformBlock (res, full, BlockSizeByte, res, full);
 416 #else
 417                         switch (algo.Padding) {
 418                         case PaddingMode.ANSIX923:
 419                                 // XX 00 00 00 00 00 00 07 (zero + padding length)
 420                                 res [res.Length - 1] = padding;
 421                                 Buffer.BlockCopy (inputBuffer, inputOffset, res, full, rem);
 422                                 // the last padded block will be transformed in-place
 423                                 InternalTransformBlock (res, full, BlockSizeByte, res, full);
 424                                 break;
 425                         case PaddingMode.ISO10126:
 426                                 // XX 3F 52 2A 81 AB F7 07 (random + padding length)
 427                                 Random (res, res.Length - padding, padding - 1);
 428                                 res [res.Length - 1] = padding;
 429                                 Buffer.BlockCopy (inputBuffer, inputOffset, res, full, rem);
 430                                 // the last padded block will be transformed in-place
 431                                 InternalTransformBlock (res, full, BlockSizeByte, res, full);
 432                                 break;
 433                         case PaddingMode.PKCS7:
 434                                 // XX 07 07 07 07 07 07 07 (padding length)
 435                                 for (int i = res.Length; --i >= (res.Length - padding);)
 436                                         res [i] = padding;
 437                                 Buffer.BlockCopy (inputBuffer, inputOffset, res, full, rem);
 438                                 // the last padded block will be transformed in-place
 439                                 InternalTransformBlock (res, full, BlockSizeByte, res, full);
 440                                 break;
 441                         default:
 442                                 InternalTransformBlock (inputBuffer, inputOffset, BlockSizeByte, res, outputOffset);
 443                                 break;
 444                         }
 445 #endif // NET_2_1
 446                         return res;
 447                 }
 448
 449                 private byte[] FinalDecrypt (byte[] inputBuffer, int inputOffset, int inputCount)
 450                 {
 451                         if ((inputCount % BlockSizeByte) > 0)
 452                                 throw new CryptographicException ("Invalid input block size.");
 453
 454                         int total = inputCount;
 455                         if (lastBlock)
 456                                 total += BlockSizeByte;
 457
 458                         byte[] res = new byte [total];
 459                         int outputOffset = 0;
 460
 461                         while (inputCount > 0) {
 462                                 int len = InternalTransformBlock (inputBuffer, inputOffset, BlockSizeByte, res, outputOffset);
 463                                 inputOffset += BlockSizeByte;
 464                                 outputOffset += len;
 465                                 inputCount -= BlockSizeByte;
 466                         }
 467
 468                         if (lastBlock) {
 469                                 Transform (workBuff, workout);
 470                                 Buffer.BlockCopy (workout, 0, res, outputOffset, BlockSizeByte);
 471                                 outputOffset += BlockSizeByte;
 472                                 lastBlock = false;
 473                         }
 474
 475                         // total may be 0 (e.g. PaddingMode.None)
 476                         byte padding = ((total > 0) ? res [total - 1] : (byte) 0);
 477 #if MOONLIGHT
 478                         // only PKCS7 is supported Silverlight 2.0
 479                         if ((padding == 0) || (padding > BlockSizeByte))
 480                                 throw new CryptographicException (Locale.GetText ("Bad padding length."));
 481                         for (int i = padding - 1; i > 0; i--) {
 482                                 if (res [total - 1 - i] != padding)
 483                                         throw new CryptographicException (Locale.GetText ("Bad padding at position {0}.", i));
 484                         }
 485                         total -= padding;
 486 #else
 487                         switch (algo.Padding) {
 488                         case PaddingMode.ANSIX923:
 489                                 if ((padding == 0) || (padding > BlockSizeByte))
 490                                         ThrowBadPaddingException (algo.Padding, padding, -1);
 491                                 for (int i = padding - 1; i > 0; i--) {
 492                                         if (res [total - 1 - i] != 0x00)
 493                                                 ThrowBadPaddingException (algo.Padding, -1, i);
 494                                 }
 495                                 total -= padding;
 496                                 break;
 497                         case PaddingMode.ISO10126:
 498                                 if ((padding == 0) || (padding > BlockSizeByte))
 499                                         ThrowBadPaddingException (algo.Padding, padding, -1);
 500                                 total -= padding;
 501                                 break;
 502                         case PaddingMode.PKCS7:
 503                                 if ((padding == 0) || (padding > BlockSizeByte))
 504                                         ThrowBadPaddingException (algo.Padding, padding, -1);
 505                                 for (int i = padding - 1; i > 0; i--) {
 506                                         if (res [total - 1 - i] != padding)
 507                                                 ThrowBadPaddingException (algo.Padding, -1, i);
 508                                 }
 509                                 total -= padding;
 510                                 break;
 511                         case PaddingMode.None:  // nothing to do - it's a multiple of block size
 512                         case PaddingMode.Zeros: // nothing to do - user must unpad himself
 513                                 break;
 514                         }
 515 #endif // NET_2_1
 516
 517                         // return output without padding
 518                         if (total > 0) {
 519                                 byte[] data = new byte [total];
 520                                 Buffer.BlockCopy (res, 0, data, 0, total);
 521                                 // zeroize decrypted data (copy with padding)
 522                                 Array.Clear (res, 0, res.Length);
 523                                 return data;
 524                         }
 525                         else
 526                                 return new byte [0];
 527                 }
 528
 529                 public virtual byte[] TransformFinalBlock (byte[] inputBuffer, int inputOffset, int inputCount)
 530                 {
 531                         if (m_disposed)
 532                                 throw new ObjectDisposedException ("Object is disposed");
 533                         CheckInput (inputBuffer, inputOffset, inputCount);
 534
 535                         if (encrypt)
 536                                 return FinalEncrypt (inputBuffer, inputOffset, inputCount);
 537                         else
 538                                 return FinalDecrypt (inputBuffer, inputOffset, inputCount);
 539                 }
 540         }
 541 }