mcs/class/Mono.Security/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                 // Silverlight 2.0 does not support any feedback mode
  55                 protected int FeedBackByte;
  56                 private bool m_disposed = false;
  57                 protected bool lastBlock;
  58
  59                 public SymmetricTransform (SymmetricAlgorithm symmAlgo, bool encryption, byte[] rgbIV)
  60                 {
  61                         algo = symmAlgo;
  62                         encrypt = encryption;
  63                         BlockSizeByte = (algo.BlockSize >> 3);
  64
  65                         if (rgbIV == null) {
  66                                 rgbIV = KeyBuilder.IV (BlockSizeByte);
  67                         } else {
  68                                 rgbIV = (byte[]) rgbIV.Clone ();
  69                         }
  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                         padmode = algo.Padding;
  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                         // transform buffers
  83                         workBuff = new byte [BlockSizeByte];
  84                         workout =  new byte [BlockSizeByte];
  85                 }
  86
  87                 ~SymmetricTransform ()
  88                 {
  89                         Dispose (false);
  90                 }
  91
  92                 void IDisposable.Dispose ()
  93                 {
  94                         Dispose (true);
  95                         GC.SuppressFinalize (this);  // Finalization is now unnecessary
  96                 }
  97
  98                 // MUST be overriden by classes using unmanaged ressources
  99                 // the override method must call the base class
 100                 protected virtual void Dispose (bool disposing)
 101                 {
 102                         if (!m_disposed) {
 103                                 if (disposing) {
 104                                         // dispose managed object: zeroize and free
 105                                         Array.Clear (temp, 0, BlockSizeByte);
 106                                         temp = null;
 107                                         Array.Clear (temp2, 0, BlockSizeByte);
 108                                         temp2 = null;
 109                                 }
 110                                 m_disposed = true;
 111                         }
 112                 }
 113
 114                 public virtual bool CanTransformMultipleBlocks {
 115                         get { return true; }
 116                 }
 117
 118                 public virtual bool CanReuseTransform {
 119                         get { return false; }
 120                 }
 121
 122                 public virtual int InputBlockSize {
 123                         get { return BlockSizeByte; }
 124                 }
 125
 126                 public virtual int OutputBlockSize {
 127                         get { return BlockSizeByte; }
 128                 }
 129
 130                 // note: Each block MUST be BlockSizeValue in size!!!
 131                 // i.e. Any padding must be done before calling this method
 132                 protected virtual void Transform (byte[] input, byte[] output)
 133                 {
 134                         switch (algo.Mode) {
 135                         case CipherMode.ECB:
 136                                 ECB (input, output);
 137                                 break;
 138                         case CipherMode.CBC:
 139                                 CBC (input, output);
 140                                 break;
 141                         case CipherMode.CFB:
 142                                 CFB (input, output);
 143                                 break;
 144                         case CipherMode.OFB:
 145                                 OFB (input, output);
 146                                 break;
 147                         case CipherMode.CTS:
 148                                 CTS (input, output);
 149                                 break;
 150                         default:
 151                                 throw new NotImplementedException ("Unkown CipherMode" + algo.Mode.ToString ());
 152                         }
 153                 }
 154
 155                 // Electronic Code Book (ECB)
 156                 protected abstract void ECB (byte[] input, byte[] output);
 157
 158                 // Cipher-Block-Chaining (CBC)
 159                 protected virtual void CBC (byte[] input, byte[] output)
 160                 {
 161                         if (encrypt) {
 162                                 for (int i = 0; i < BlockSizeByte; i++)
 163                                         temp[i] ^= input[i];
 164                                 ECB (temp, output);
 165                                 Buffer.BlockCopy (output, 0, temp, 0, BlockSizeByte);
 166                         }
 167                         else {
 168                                 Buffer.BlockCopy (input, 0, temp2, 0, BlockSizeByte);
 169                                 ECB (input, output);
 170                                 for (int i = 0; i < BlockSizeByte; i++)
 171                                         output[i] ^= temp[i];
 172                                 Buffer.BlockCopy (temp2, 0, temp, 0, BlockSizeByte);
 173                         }
 174                 }
 175
 176                 // Cipher-FeedBack (CFB)
 177                 // this is how *CryptoServiceProvider implements CFB
 178                 // only AesCryptoServiceProvider support CFB > 8
 179                 // RijndaelManaged is incompatible with this implementation (and overrides it in it's own transform)
 180                 protected virtual void CFB (byte[] input, byte[] output)
 181                 {
 182                         if (encrypt) {
 183                                 for (int x = 0; x < BlockSizeByte; x++) {
 184                                         // temp is first initialized with the IV
 185                                         ECB (temp, temp2);
 186                                         output [x] = (byte) (temp2 [0] ^ input [x]);
 187                                         Buffer.BlockCopy (temp, 1, temp, 0, BlockSizeByte - 1);
 188                                         Buffer.BlockCopy (output, x, temp, BlockSizeByte - 1, 1);
 189                                 }
 190                         }
 191                         else {
 192                                 for (int x = 0; x < BlockSizeByte; x++) {
 193                                         // we do not really decrypt this data!
 194                                         encrypt = true;
 195                                         // temp is first initialized with the IV
 196                                         ECB (temp, temp2);
 197                                         encrypt = false;
 198
 199                                         Buffer.BlockCopy (temp, 1, temp, 0, BlockSizeByte - 1);
 200                                         Buffer.BlockCopy (input, x, temp, BlockSizeByte - 1, 1);
 201                                         output [x] = (byte) (temp2 [0] ^ input [x]);
 202                                 }
 203                         }
 204                 }
 205
 206                 // Output-FeedBack (OFB)
 207                 protected virtual void OFB (byte[] input, byte[] output)
 208                 {
 209                         throw new CryptographicException ("OFB isn't supported by the framework");
 210                 }
 211
 212                 // Cipher Text Stealing (CTS)
 213                 protected virtual void CTS (byte[] input, byte[] output)
 214                 {
 215                         throw new CryptographicException ("CTS isn't supported by the framework");
 216                 }
 217
 218                 private void CheckInput (byte[] inputBuffer, int inputOffset, int inputCount)
 219                 {
 220                         if (inputBuffer == null)
 221                                 throw new ArgumentNullException ("inputBuffer");
 222                         if (inputOffset < 0)
 223                                 throw new ArgumentOutOfRangeException ("inputOffset", "< 0");
 224                         if (inputCount < 0)
 225                                 throw new ArgumentOutOfRangeException ("inputCount", "< 0");
 226                         // ordered to avoid possible integer overflow
 227                         if (inputOffset > inputBuffer.Length - inputCount)
 228                                 throw new ArgumentException ("inputBuffer", Locale.GetText ("Overflow"));
 229                 }
 230
 231                 // this method may get called MANY times so this is the one to optimize
 232                 public virtual int TransformBlock (byte[] inputBuffer, int inputOffset, int inputCount, byte[] outputBuffer, int outputOffset)
 233                 {
 234                         if (m_disposed)
 235                                 throw new ObjectDisposedException ("Object is disposed");
 236                         CheckInput (inputBuffer, inputOffset, inputCount);
 237                         // check output parameters
 238                         if (outputBuffer == null)
 239                                 throw new ArgumentNullException ("outputBuffer");
 240                         if (outputOffset < 0)
 241                                 throw new ArgumentOutOfRangeException ("outputOffset", "< 0");
 242
 243                         // ordered to avoid possible integer overflow
 244                         int len = outputBuffer.Length - inputCount - outputOffset;
 245                         if (!encrypt && (0 > len) && ((padmode == PaddingMode.None) || (padmode == PaddingMode.Zeros))) {
 246                                 throw new CryptographicException ("outputBuffer", Locale.GetText ("Overflow"));
 247                         } else if (KeepLastBlock) {
 248                                 if (0 > len + BlockSizeByte) {
 249                                         throw new CryptographicException ("outputBuffer", Locale.GetText ("Overflow"));
 250                                 }
 251                         } else {
 252                                 if (0 > len) {
 253                                         // there's a special case if this is the end of the decryption process
 254                                         if (inputBuffer.Length - inputOffset - outputBuffer.Length == BlockSizeByte)
 255                                                 inputCount = outputBuffer.Length - outputOffset;
 256                                         else
 257                                                 throw new CryptographicException ("outputBuffer", Locale.GetText ("Overflow"));
 258                                 }
 259                         }
 260                         return InternalTransformBlock (inputBuffer, inputOffset, inputCount, outputBuffer, outputOffset);
 261                 }
 262
 263                 private bool KeepLastBlock {
 264                         get {
 265                                 return ((!encrypt) && (padmode != PaddingMode.None) && (padmode != PaddingMode.Zeros));
 266                         }
 267                 }
 268
 269                 private int InternalTransformBlock (byte[] inputBuffer, int inputOffset, int inputCount, byte[] outputBuffer, int outputOffset)
 270                 {
 271                         int offs = inputOffset;
 272                         int full;
 273
 274                         // this way we don't do a modulo every time we're called
 275                         // and we may save a division
 276                         if (inputCount != BlockSizeByte) {
 277                                 if ((inputCount % BlockSizeByte) != 0)
 278                                         throw new CryptographicException ("Invalid input block size.");
 279
 280                                 full = inputCount / BlockSizeByte;
 281                         }
 282                         else
 283                                 full = 1;
 284
 285                         if (KeepLastBlock)
 286                                 full--;
 287
 288                         int total = 0;
 289
 290                         if (lastBlock) {
 291                                 Transform (workBuff, workout);
 292                                 Buffer.BlockCopy (workout, 0, outputBuffer, outputOffset, BlockSizeByte);
 293                                 outputOffset += BlockSizeByte;
 294                                 total += BlockSizeByte;
 295                                 lastBlock = false;
 296                         }
 297
 298                         for (int i = 0; i < full; i++) {
 299                                 Buffer.BlockCopy (inputBuffer, offs, workBuff, 0, BlockSizeByte);
 300                                 Transform (workBuff, workout);
 301                                 Buffer.BlockCopy (workout, 0, outputBuffer, outputOffset, BlockSizeByte);
 302                                 offs += BlockSizeByte;
 303                                 outputOffset += BlockSizeByte;
 304                                 total += BlockSizeByte;
 305                         }
 306
 307                         if (KeepLastBlock) {
 308                                 Buffer.BlockCopy (inputBuffer, offs, workBuff, 0, BlockSizeByte);
 309                                 lastBlock = true;
 310                         }
 311
 312                         return total;
 313                 }
 314
 315                 RandomNumberGenerator _rng;
 316
 317                 private void Random (byte[] buffer, int start, int length)
 318                 {
 319                         if (_rng == null) {
 320                                 _rng = RandomNumberGenerator.Create ();
 321                         }
 322                         byte[] random = new byte [length];
 323                         _rng.GetBytes (random);
 324                         Buffer.BlockCopy (random, 0, buffer, start, length);
 325                 }
 326
 327                 private void ThrowBadPaddingException (PaddingMode padding, int length, int position)
 328                 {
 329                         string msg = String.Format (Locale.GetText ("Bad {0} padding."), padding);
 330                         if (length >= 0)
 331                                 msg += String.Format (Locale.GetText (" Invalid length {0}."), length);
 332                         if (position >= 0)
 333                                 msg += String.Format (Locale.GetText (" Error found at position {0}."), position);
 334                         throw new CryptographicException (msg);
 335                 }
 336
 337                 protected virtual byte[] FinalEncrypt (byte[] inputBuffer, int inputOffset, int inputCount)
 338                 {
 339                         // are there still full block to process ?
 340                         int full = (inputCount / BlockSizeByte) * BlockSizeByte;
 341                         int rem = inputCount - full;
 342                         int total = full;
 343
 344                         switch (padmode) {
 345                         case PaddingMode.ANSIX923:
 346                         case PaddingMode.ISO10126:
 347                         case PaddingMode.PKCS7:
 348                                 // we need to add an extra block for padding
 349                                 total += BlockSizeByte;
 350                                 break;
 351                         default:
 352                                 if (inputCount == 0)
 353                                         return new byte [0];
 354                                 if (rem != 0) {
 355                                         if (padmode == PaddingMode.None)
 356                                                 throw new CryptographicException ("invalid block length");
 357                                         // zero padding the input (by adding a block for the partial data)
 358                                         byte[] paddedInput = new byte [full + BlockSizeByte];
 359                                         Buffer.BlockCopy (inputBuffer, inputOffset, paddedInput, 0, inputCount);
 360                                         inputBuffer = paddedInput;
 361                                         inputOffset = 0;
 362                                         inputCount = paddedInput.Length;
 363                                         total = inputCount;
 364                                 }
 365                                 break;
 366                         }
 367
 368                         byte[] res = new byte [total];
 369                         int outputOffset = 0;
 370
 371                         // process all blocks except the last (final) block
 372                         while (total > BlockSizeByte) {
 373                                 InternalTransformBlock (inputBuffer, inputOffset, BlockSizeByte, res, outputOffset);
 374                                 inputOffset += BlockSizeByte;
 375                                 outputOffset += BlockSizeByte;
 376                                 total -= BlockSizeByte;
 377                         }
 378
 379                         // now we only have a single last block to encrypt
 380                         byte padding = (byte) (BlockSizeByte - rem);
 381                         switch (padmode) {
 382                         case PaddingMode.ANSIX923:
 383                                 // XX 00 00 00 00 00 00 07 (zero + padding length)
 384                                 res [res.Length - 1] = padding;
 385                                 Buffer.BlockCopy (inputBuffer, inputOffset, res, full, rem);
 386                                 // the last padded block will be transformed in-place
 387                                 InternalTransformBlock (res, full, BlockSizeByte, res, full);
 388                                 break;
 389                         case PaddingMode.ISO10126:
 390                                 // XX 3F 52 2A 81 AB F7 07 (random + padding length)
 391                                 Random (res, res.Length - padding, padding - 1);
 392                                 res [res.Length - 1] = padding;
 393                                 Buffer.BlockCopy (inputBuffer, inputOffset, res, full, rem);
 394                                 // the last padded block will be transformed in-place
 395                                 InternalTransformBlock (res, full, BlockSizeByte, res, full);
 396                                 break;
 397                         case PaddingMode.PKCS7:
 398                                 // XX 07 07 07 07 07 07 07 (padding length)
 399                                 for (int i = res.Length; --i >= (res.Length - padding);)
 400                                         res [i] = padding;
 401                                 Buffer.BlockCopy (inputBuffer, inputOffset, res, full, rem);
 402                                 // the last padded block will be transformed in-place
 403                                 InternalTransformBlock (res, full, BlockSizeByte, res, full);
 404                                 break;
 405                         default:
 406                                 InternalTransformBlock (inputBuffer, inputOffset, BlockSizeByte, res, outputOffset);
 407                                 break;
 408                         }
 409                         return res;
 410                 }
 411
 412                 protected virtual byte[] FinalDecrypt (byte[] inputBuffer, int inputOffset, int inputCount)
 413                 {
 414                         int full = inputCount;
 415                         int total = inputCount;
 416                         if (lastBlock)
 417                                 total += BlockSizeByte;
 418
 419                         byte[] res = new byte [total];
 420                         int outputOffset = 0;
 421
 422                         while (full > 0) {
 423                                 int len = InternalTransformBlock (inputBuffer, inputOffset, BlockSizeByte, res, outputOffset);
 424                                 inputOffset += BlockSizeByte;
 425                                 outputOffset += len;
 426                                 full -= BlockSizeByte;
 427                         }
 428
 429                         if (lastBlock) {
 430                                 Transform (workBuff, workout);
 431                                 Buffer.BlockCopy (workout, 0, res, outputOffset, BlockSizeByte);
 432                                 outputOffset += BlockSizeByte;
 433                                 lastBlock = false;
 434                         }
 435
 436                         // total may be 0 (e.g. PaddingMode.None)
 437                         byte padding = ((total > 0) ? res [total - 1] : (byte) 0);
 438                         switch (padmode) {
 439                         case PaddingMode.ANSIX923:
 440                                 if ((padding == 0) || (padding > BlockSizeByte))
 441                                         ThrowBadPaddingException (padmode, padding, -1);
 442                                 for (int i = padding - 1; i > 0; i--) {
 443                                         if (res [total - 1 - i] != 0x00)
 444                                                 ThrowBadPaddingException (padmode, -1, i);
 445                                 }
 446                                 total -= padding;
 447                                 break;
 448                         case PaddingMode.ISO10126:
 449                                 if ((padding == 0) || (padding > BlockSizeByte))
 450                                         ThrowBadPaddingException (padmode, padding, -1);
 451                                 total -= padding;
 452                                 break;
 453                         case PaddingMode.PKCS7:
 454                                 if ((padding == 0) || (padding > BlockSizeByte))
 455                                         ThrowBadPaddingException (padmode, padding, -1);
 456                                 for (int i = padding - 1; i > 0; i--) {
 457                                         if (res [total - 1 - i] != padding)
 458                                                 ThrowBadPaddingException (padmode, -1, i);
 459                                 }
 460                                 total -= padding;
 461                                 break;
 462                         case PaddingMode.None:  // nothing to do - it's a multiple of block size
 463                         case PaddingMode.Zeros: // nothing to do - user must unpad himself
 464                                 break;
 465                         }
 466
 467                         // return output without padding
 468                         if (total > 0) {
 469                                 byte[] data = new byte [total];
 470                                 Buffer.BlockCopy (res, 0, data, 0, total);
 471                                 // zeroize decrypted data (copy with padding)
 472                                 Array.Clear (res, 0, res.Length);
 473                                 return data;
 474                         }
 475                         else
 476                                 return new byte [0];
 477                 }
 478
 479                 public virtual byte[] TransformFinalBlock (byte[] inputBuffer, int inputOffset, int inputCount)
 480                 {
 481                         if (m_disposed)
 482                                 throw new ObjectDisposedException ("Object is disposed");
 483                         CheckInput (inputBuffer, inputOffset, inputCount);
 484
 485                         if (encrypt)
 486                                 return FinalEncrypt (inputBuffer, inputOffset, inputCount);
 487                         else
 488                                 return FinalDecrypt (inputBuffer, inputOffset, inputCount);
 489                 }
 490         }
 491 }