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                 protected int BlockSizeByte;
  49                 protected byte[] temp;
  50                 protected byte[] temp2;
  51                 private byte[] workBuff;
  52                 private byte[] workout;
  53                 protected PaddingMode padmode;
  54 #if !MOONLIGHT
  55                 // Silverlight 2.0 does not support any feedback mode
  56                 protected int FeedBackByte;
  57 #endif
  58                 private bool m_disposed = false;
  59                 protected 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                         padmode = algo.Padding;
  79                         // mode buffers
  80                         temp = new byte [BlockSizeByte];
  81                         Buffer.BlockCopy (rgbIV, 0, temp, 0, System.Math.Min (BlockSizeByte, rgbIV.Length));
  82                         temp2 = new byte [BlockSizeByte];
  83 #if !MOONLIGHT
  84                         FeedBackByte = (algo.FeedbackSize >> 3);
  85 #endif
  86                         // transform buffers
  87                         workBuff = new byte [BlockSizeByte];
  88                         workout =  new byte [BlockSizeByte];
  89                 }
  90
  91                 ~SymmetricTransform ()
  92                 {
  93                         Dispose (false);
  94                 }
  95
  96                 void IDisposable.Dispose ()
  97                 {
  98                         Dispose (true);
  99                         GC.SuppressFinalize (this);  // Finalization is now unnecessary
 100                 }
 101
 102                 // MUST be overriden by classes using unmanaged ressources
 103                 // the override method must call the base class
 104                 protected virtual void Dispose (bool disposing)
 105                 {
 106                         if (!m_disposed) {
 107                                 if (disposing) {
 108                                         // dispose managed object: zeroize and free
 109                                         Array.Clear (temp, 0, BlockSizeByte);
 110                                         temp = null;
 111                                         Array.Clear (temp2, 0, BlockSizeByte);
 112                                         temp2 = null;
 113                                 }
 114                                 m_disposed = true;
 115                         }
 116                 }
 117
 118                 public virtual bool CanTransformMultipleBlocks {
 119                         get { return true; }
 120                 }
 121
 122                 public virtual bool CanReuseTransform {
 123                         get { return false; }
 124                 }
 125
 126                 public virtual int InputBlockSize {
 127                         get { return BlockSizeByte; }
 128                 }
 129
 130                 public virtual int OutputBlockSize {
 131                         get { return BlockSizeByte; }
 132                 }
 133
 134                 // note: Each block MUST be BlockSizeValue in size!!!
 135                 // i.e. Any padding must be done before calling this method
 136                 protected virtual void Transform (byte[] input, byte[] output)
 137                 {
 138 #if MOONLIGHT
 139                         // Silverlight 2.0 only supports CBC
 140                         CBC (input, output);
 141 #else
 142                         switch (algo.Mode) {
 143                         case CipherMode.ECB:
 144                                 ECB (input, output);
 145                                 break;
 146                         case CipherMode.CBC:
 147                                 CBC (input, output);
 148                                 break;
 149                         case CipherMode.CFB:
 150                                 CFB (input, output);
 151                                 break;
 152                         case CipherMode.OFB:
 153                                 OFB (input, output);
 154                                 break;
 155                         case CipherMode.CTS:
 156                                 CTS (input, output);
 157                                 break;
 158                         default:
 159                                 throw new NotImplementedException ("Unkown CipherMode" + algo.Mode.ToString ());
 160                         }
 161 #endif
 162                 }
 163
 164                 // Electronic Code Book (ECB)
 165                 protected abstract void ECB (byte[] input, byte[] output);
 166
 167                 // Cipher-Block-Chaining (CBC)
 168                 protected virtual void CBC (byte[] input, byte[] output)
 169                 {
 170                         if (encrypt) {
 171                                 for (int i = 0; i < BlockSizeByte; i++)
 172                                         temp[i] ^= input[i];
 173                                 ECB (temp, output);
 174                                 Buffer.BlockCopy (output, 0, temp, 0, BlockSizeByte);
 175                         }
 176                         else {
 177                                 Buffer.BlockCopy (input, 0, temp2, 0, BlockSizeByte);
 178                                 ECB (input, output);
 179                                 for (int i = 0; i < BlockSizeByte; i++)
 180                                         output[i] ^= temp[i];
 181                                 Buffer.BlockCopy (temp2, 0, temp, 0, BlockSizeByte);
 182                         }
 183                 }
 184
 185 #if !MOONLIGHT
 186                 // Cipher-FeedBack (CFB)
 187                 // this is how *CryptoServiceProvider implements CFB
 188                 // only AesCryptoServiceProvider support CFB > 8
 189                 // RijndaelManaged is incompatible with this implementation (and overrides it in it's own transform)
 190                 protected virtual void CFB (byte[] input, byte[] output)
 191                 {
 192                         if (encrypt) {
 193                                 for (int x = 0; x < BlockSizeByte; x++) {
 194                                         // temp is first initialized with the IV
 195                                         ECB (temp, temp2);
 196                                         output [x] = (byte) (temp2 [0] ^ input [x]);
 197                                         Buffer.BlockCopy (temp, 1, temp, 0, BlockSizeByte - 1);
 198                                         Buffer.BlockCopy (output, x, temp, BlockSizeByte - 1, 1);
 199                                 }
 200                         }
 201                         else {
 202                                 for (int x = 0; x < BlockSizeByte; 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, 1, temp, 0, BlockSizeByte - 1);
 210                                         Buffer.BlockCopy (input, x, temp, BlockSizeByte - 1, 1);
 211                                         output [x] = (byte) (temp2 [0] ^ input [x]);
 212                                 }
 213                         }
 214                 }
 215
 216                 // Output-FeedBack (OFB)
 217                 protected virtual void OFB (byte[] input, byte[] output)
 218                 {
 219                         throw new CryptographicException ("OFB isn't supported by the framework");
 220                 }
 221
 222                 // Cipher Text Stealing (CTS)
 223                 protected virtual void CTS (byte[] input, byte[] output)
 224                 {
 225                         throw new CryptographicException ("CTS isn't supported by the framework");
 226                 }
 227 #endif
 228
 229                 private void CheckInput (byte[] inputBuffer, int inputOffset, int inputCount)
 230                 {
 231                         if (inputBuffer == null)
 232                                 throw new ArgumentNullException ("inputBuffer");
 233                         if (inputOffset < 0)
 234                                 throw new ArgumentOutOfRangeException ("inputOffset", "< 0");
 235                         if (inputCount < 0)
 236                                 throw new ArgumentOutOfRangeException ("inputCount", "< 0");
 237                         // ordered to avoid possible integer overflow
 238                         if (inputOffset > inputBuffer.Length - inputCount)
 239                                 throw new ArgumentException ("inputBuffer", Locale.GetText ("Overflow"));
 240                 }
 241
 242                 // this method may get called MANY times so this is the one to optimize
 243                 public virtual int TransformBlock (byte[] inputBuffer, int inputOffset, int inputCount, byte[] outputBuffer, int outputOffset)
 244                 {
 245                         if (m_disposed)
 246                                 throw new ObjectDisposedException ("Object is disposed");
 247                         CheckInput (inputBuffer, inputOffset, inputCount);
 248                         // check output parameters
 249                         if (outputBuffer == null)
 250                                 throw new ArgumentNullException ("outputBuffer");
 251                         if (outputOffset < 0)
 252                                 throw new ArgumentOutOfRangeException ("outputOffset", "< 0");
 253
 254                         // ordered to avoid possible integer overflow
 255                         int len = outputBuffer.Length - inputCount - outputOffset;
 256 #if MOONLIGHT
 257                         // only PKCS7 is supported Silverlight 2.0
 258                         if (KeepLastBlock) {
 259 #else
 260                         if (!encrypt && (0 > len) && ((padmode == PaddingMode.None) || (padmode == PaddingMode.Zeros))) {
 261                                 throw new CryptographicException ("outputBuffer", Locale.GetText ("Overflow"));
 262                         } else if (KeepLastBlock) {
 263 #endif
 264                                 if (0 > len + BlockSizeByte) {
 265                                         throw new CryptographicException ("outputBuffer", Locale.GetText ("Overflow"));
 266                                 }
 267                         } else {
 268                                 if (0 > len) {
 269                                         // there's a special case if this is the end of the decryption process
 270                                         if (inputBuffer.Length - inputOffset - outputBuffer.Length == BlockSizeByte)
 271                                                 inputCount = outputBuffer.Length - outputOffset;
 272                                         else
 273                                                 throw new CryptographicException ("outputBuffer", Locale.GetText ("Overflow"));
 274                                 }
 275                         }
 276                         return InternalTransformBlock (inputBuffer, inputOffset, inputCount, outputBuffer, outputOffset);
 277                 }
 278
 279                 private bool KeepLastBlock {
 280                         get {
 281 #if MOONLIGHT
 282                                 // only PKCS7 is supported Silverlight 2.0
 283                                 return !encrypt;
 284 #else
 285                                 return ((!encrypt) && (padmode != PaddingMode.None) && (padmode != PaddingMode.Zeros));
 286 #endif
 287                         }
 288                 }
 289
 290                 private int InternalTransformBlock (byte[] inputBuffer, int inputOffset, int inputCount, byte[] outputBuffer, int outputOffset)
 291                 {
 292                         int offs = inputOffset;
 293                         int full;
 294
 295                         // this way we don't do a modulo every time we're called
 296                         // and we may save a division
 297                         if (inputCount != BlockSizeByte) {
 298                                 if ((inputCount % BlockSizeByte) != 0)
 299                                         throw new CryptographicException ("Invalid input block size.");
 300
 301                                 full = inputCount / BlockSizeByte;
 302                         }
 303                         else
 304                                 full = 1;
 305
 306                         if (KeepLastBlock)
 307                                 full--;
 308
 309                         int total = 0;
 310
 311                         if (lastBlock) {
 312                                 Transform (workBuff, workout);
 313                                 Buffer.BlockCopy (workout, 0, outputBuffer, outputOffset, BlockSizeByte);
 314                                 outputOffset += BlockSizeByte;
 315                                 total += BlockSizeByte;
 316                                 lastBlock = false;
 317                         }
 318
 319                         for (int i = 0; i < full; i++) {
 320                                 Buffer.BlockCopy (inputBuffer, offs, workBuff, 0, BlockSizeByte);
 321                                 Transform (workBuff, workout);
 322                                 Buffer.BlockCopy (workout, 0, outputBuffer, outputOffset, BlockSizeByte);
 323                                 offs += BlockSizeByte;
 324                                 outputOffset += BlockSizeByte;
 325                                 total += BlockSizeByte;
 326                         }
 327
 328                         if (KeepLastBlock) {
 329                                 Buffer.BlockCopy (inputBuffer, offs, workBuff, 0, BlockSizeByte);
 330                                 lastBlock = true;
 331                         }
 332
 333                         return total;
 334                 }
 335
 336 #if !MOONLIGHT
 337                 RandomNumberGenerator _rng;
 338
 339                 private void Random (byte[] buffer, int start, int length)
 340                 {
 341                         if (_rng == null) {
 342                                 _rng = RandomNumberGenerator.Create ();
 343                         }
 344                         byte[] random = new byte [length];
 345                         _rng.GetBytes (random);
 346                         Buffer.BlockCopy (random, 0, buffer, start, length);
 347                 }
 348
 349                 private void ThrowBadPaddingException (PaddingMode padding, int length, int position)
 350                 {
 351                         string msg = String.Format (Locale.GetText ("Bad {0} padding."), padding);
 352                         if (length >= 0)
 353                                 msg += String.Format (Locale.GetText (" Invalid length {0}."), length);
 354                         if (position >= 0)
 355                                 msg += String.Format (Locale.GetText (" Error found at position {0}."), position);
 356                         throw new CryptographicException (msg);
 357                 }
 358 #endif
 359
 360                 protected virtual byte[] FinalEncrypt (byte[] inputBuffer, int inputOffset, int inputCount)
 361                 {
 362                         // are there still full block to process ?
 363                         int full = (inputCount / BlockSizeByte) * BlockSizeByte;
 364                         int rem = inputCount - full;
 365                         int total = full;
 366
 367 #if MOONLIGHT
 368                         // only PKCS7 is supported Silverlight 2.0
 369                         total += BlockSizeByte;
 370 #else
 371                         switch (padmode) {
 372                         case PaddingMode.ANSIX923:
 373                         case PaddingMode.ISO10126:
 374                         case PaddingMode.PKCS7:
 375                                 // we need to add an extra block for padding
 376                                 total += BlockSizeByte;
 377                                 break;
 378                         default:
 379                                 if (inputCount == 0)
 380                                         return new byte [0];
 381                                 if (rem != 0) {
 382                                         if (padmode == PaddingMode.None)
 383                                                 throw new CryptographicException ("invalid block length");
 384                                         // zero padding the input (by adding a block for the partial data)
 385                                         byte[] paddedInput = new byte [full + BlockSizeByte];
 386                                         Buffer.BlockCopy (inputBuffer, inputOffset, paddedInput, 0, inputCount);
 387                                         inputBuffer = paddedInput;
 388                                         inputOffset = 0;
 389                                         inputCount = paddedInput.Length;
 390                                         total = inputCount;
 391                                 }
 392                                 break;
 393                         }
 394 #endif // NET_2_1
 395
 396                         byte[] res = new byte [total];
 397                         int outputOffset = 0;
 398
 399                         // process all blocks except the last (final) block
 400                         while (total > BlockSizeByte) {
 401                                 InternalTransformBlock (inputBuffer, inputOffset, BlockSizeByte, res, outputOffset);
 402                                 inputOffset += BlockSizeByte;
 403                                 outputOffset += BlockSizeByte;
 404                                 total -= BlockSizeByte;
 405                         }
 406
 407                         // now we only have a single last block to encrypt
 408                         byte padding = (byte) (BlockSizeByte - rem);
 409 #if MOONLIGHT
 410                         // only PKCS7 is supported Silverlight 2.0
 411                         for (int i = res.Length; --i >= (res.Length - padding);)
 412                                 res [i] = padding;
 413                         Buffer.BlockCopy (inputBuffer, inputOffset, res, full, rem);
 414                         InternalTransformBlock (res, full, BlockSizeByte, res, full);
 415 #else
 416                         switch (padmode) {
 417                         case PaddingMode.ANSIX923:
 418                                 // XX 00 00 00 00 00 00 07 (zero + padding length)
 419                                 res [res.Length - 1] = padding;
 420                                 Buffer.BlockCopy (inputBuffer, inputOffset, res, full, rem);
 421                                 // the last padded block will be transformed in-place
 422                                 InternalTransformBlock (res, full, BlockSizeByte, res, full);
 423                                 break;
 424                         case PaddingMode.ISO10126:
 425                                 // XX 3F 52 2A 81 AB F7 07 (random + padding length)
 426                                 Random (res, res.Length - padding, padding - 1);
 427                                 res [res.Length - 1] = padding;
 428                                 Buffer.BlockCopy (inputBuffer, inputOffset, res, full, rem);
 429                                 // the last padded block will be transformed in-place
 430                                 InternalTransformBlock (res, full, BlockSizeByte, res, full);
 431                                 break;
 432                         case PaddingMode.PKCS7:
 433                                 // XX 07 07 07 07 07 07 07 (padding length)
 434                                 for (int i = res.Length; --i >= (res.Length - padding);)
 435                                         res [i] = padding;
 436                                 Buffer.BlockCopy (inputBuffer, inputOffset, res, full, rem);
 437                                 // the last padded block will be transformed in-place
 438                                 InternalTransformBlock (res, full, BlockSizeByte, res, full);
 439                                 break;
 440                         default:
 441                                 InternalTransformBlock (inputBuffer, inputOffset, BlockSizeByte, res, outputOffset);
 442                                 break;
 443                         }
 444 #endif // NET_2_1
 445                         return res;
 446                 }
 447
 448                 protected virtual byte[] FinalDecrypt (byte[] inputBuffer, int inputOffset, int inputCount)
 449                 {
 450                         int full = inputCount;
 451                         int total = inputCount;
 452                         if (lastBlock)
 453                                 total += BlockSizeByte;
 454
 455                         byte[] res = new byte [total];
 456                         int outputOffset = 0;
 457
 458                         while (full > 0) {
 459                                 int len = InternalTransformBlock (inputBuffer, inputOffset, BlockSizeByte, res, outputOffset);
 460                                 inputOffset += BlockSizeByte;
 461                                 outputOffset += len;
 462                                 full -= BlockSizeByte;
 463                         }
 464
 465                         if (lastBlock) {
 466                                 Transform (workBuff, workout);
 467                                 Buffer.BlockCopy (workout, 0, res, outputOffset, BlockSizeByte);
 468                                 outputOffset += BlockSizeByte;
 469                                 lastBlock = false;
 470                         }
 471
 472                         // total may be 0 (e.g. PaddingMode.None)
 473                         byte padding = ((total > 0) ? res [total - 1] : (byte) 0);
 474 #if MOONLIGHT
 475                         // only PKCS7 is supported Silverlight 2.0
 476                         if ((padding == 0) || (padding > BlockSizeByte))
 477                                 throw new CryptographicException (Locale.GetText ("Bad padding length."));
 478                         for (int i = padding - 1; i > 0; i--) {
 479                                 if (res [total - 1 - i] != padding)
 480                                         throw new CryptographicException (Locale.GetText ("Bad padding at position {0}.", i));
 481                         }
 482                         total -= padding;
 483 #else
 484                         switch (padmode) {
 485                         case PaddingMode.ANSIX923:
 486                                 if ((padding == 0) || (padding > BlockSizeByte))
 487                                         ThrowBadPaddingException (padmode, padding, -1);
 488                                 for (int i = padding - 1; i > 0; i--) {
 489                                         if (res [total - 1 - i] != 0x00)
 490                                                 ThrowBadPaddingException (padmode, -1, i);
 491                                 }
 492                                 total -= padding;
 493                                 break;
 494                         case PaddingMode.ISO10126:
 495                                 if ((padding == 0) || (padding > BlockSizeByte))
 496                                         ThrowBadPaddingException (padmode, padding, -1);
 497                                 total -= padding;
 498                                 break;
 499                         case PaddingMode.PKCS7:
 500                                 if ((padding == 0) || (padding > BlockSizeByte))
 501                                         ThrowBadPaddingException (padmode, padding, -1);
 502                                 for (int i = padding - 1; i > 0; i--) {
 503                                         if (res [total - 1 - i] != padding)
 504                                                 ThrowBadPaddingException (padmode, -1, i);
 505                                 }
 506                                 total -= padding;
 507                                 break;
 508                         case PaddingMode.None:  // nothing to do - it's a multiple of block size
 509                         case PaddingMode.Zeros: // nothing to do - user must unpad himself
 510                                 break;
 511                         }
 512 #endif // NET_2_1
 513
 514                         // return output without padding
 515                         if (total > 0) {
 516                                 byte[] data = new byte [total];
 517                                 Buffer.BlockCopy (res, 0, data, 0, total);
 518                                 // zeroize decrypted data (copy with padding)
 519                                 Array.Clear (res, 0, res.Length);
 520                                 return data;
 521                         }
 522                         else
 523                                 return new byte [0];
 524                 }
 525
 526                 public virtual byte[] TransformFinalBlock (byte[] inputBuffer, int inputOffset, int inputCount)
 527                 {
 528                         if (m_disposed)
 529                                 throw new ObjectDisposedException ("Object is disposed");
 530                         CheckInput (inputBuffer, inputOffset, inputCount);
 531
 532                         if (encrypt)
 533                                 return FinalEncrypt (inputBuffer, inputOffset, inputCount);
 534                         else
 535                                 return FinalDecrypt (inputBuffer, inputOffset, inputCount);
 536                 }
 537         }
 538 }