2 // Mono.Security.Cryptography.SymmetricTransform implementation
5 // Thomas Neidhart (tome@sbox.tugraz.at)
6 // Sebastien Pouliot <sebastien@ximian.com>
8 // Portions (C) 2002, 2003 Motus Technologies Inc. (http://www.motus.com)
9 // Copyright (C) 2004-2008 Novell, Inc (http://www.novell.com)
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
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16 // permit persons to whom the Software is furnished to do so, subject to
17 // the following conditions:
19 // The above copyright notice and this permission notice shall be
20 // included in all copies or substantial portions of the Software.
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32 using System.Security.Cryptography;
34 namespace Mono.Security.Cryptography {
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...
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;
54 // Silverlight 2.0 does not support any feedback mode
55 protected int FeedBackByte;
57 private bool m_disposed = false;
58 private bool lastBlock;
60 public SymmetricTransform (SymmetricAlgorithm symmAlgo, bool encryption, byte[] rgbIV)
64 BlockSizeByte = (algo.BlockSize >> 3);
67 rgbIV = KeyBuilder.IV (BlockSizeByte);
69 rgbIV = (byte[]) rgbIV.Clone ();
71 // compare the IV length with the "currently selected" block size and *ignore* IV that are too big
72 if (rgbIV.Length < BlockSizeByte) {
73 string msg = Locale.GetText ("IV is too small ({0} bytes), it should be {1} bytes long.",
74 rgbIV.Length, BlockSizeByte);
75 throw new CryptographicException (msg);
78 temp = new byte [BlockSizeByte];
79 Buffer.BlockCopy (rgbIV, 0, temp, 0, System.Math.Min (BlockSizeByte, rgbIV.Length));
80 temp2 = new byte [BlockSizeByte];
82 FeedBackByte = (algo.FeedbackSize >> 3);
85 workBuff = new byte [BlockSizeByte];
86 workout = new byte [BlockSizeByte];
89 ~SymmetricTransform ()
94 void IDisposable.Dispose ()
97 GC.SuppressFinalize (this); // Finalization is now unnecessary
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)
106 // dispose managed object: zeroize and free
107 Array.Clear (temp, 0, BlockSizeByte);
109 Array.Clear (temp2, 0, BlockSizeByte);
116 public virtual bool CanTransformMultipleBlocks {
120 public virtual bool CanReuseTransform {
121 get { return false; }
124 public virtual int InputBlockSize {
125 get { return BlockSizeByte; }
128 public virtual int OutputBlockSize {
129 get { return BlockSizeByte; }
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)
137 // Silverlight 2.0 only supports CBC
157 throw new NotImplementedException ("Unkown CipherMode" + algo.Mode.ToString ());
162 // Electronic Code Book (ECB)
163 protected abstract void ECB (byte[] input, byte[] output);
165 // Cipher-Block-Chaining (CBC)
166 protected virtual void CBC (byte[] input, byte[] output)
169 for (int i = 0; i < BlockSizeByte; i++)
172 Buffer.BlockCopy (output, 0, temp, 0, BlockSizeByte);
175 Buffer.BlockCopy (input, 0, temp2, 0, BlockSizeByte);
177 for (int i = 0; i < BlockSizeByte; i++)
178 output[i] ^= temp[i];
179 Buffer.BlockCopy (temp2, 0, temp, 0, BlockSizeByte);
184 // Cipher-FeedBack (CFB)
185 // this is how *CryptoServiceProvider implements CFB
186 // only AesCryptoServiceProvider support CFB > 8
187 // RijndaelManaged is incompatible with this implementation (and overrides it in it's own transform)
188 protected virtual void CFB (byte[] input, byte[] output)
191 for (int x = 0; x < BlockSizeByte; x++) {
192 // temp is first initialized with the IV
195 for (int i = 0; i < 1; i++)
196 output[i + x] = (byte)(temp2[i] ^ input[i + x]);
197 Buffer.BlockCopy (temp, 1, temp, 0, BlockSizeByte - 1);
198 Buffer.BlockCopy (output, x, temp, BlockSizeByte - 1, 1);
202 for (int x = 0; x < BlockSizeByte; x++) {
203 // we do not really decrypt this data!
205 // temp is first initialized with the IV
209 Buffer.BlockCopy (temp, 1, temp, 0, BlockSizeByte - 1);
210 Buffer.BlockCopy (input, x, temp, BlockSizeByte - 1, 1);
211 for (int i = 0; i < 1; i++)
212 output[i + x] = (byte)(temp2[i] ^ input[i + x]);
217 // Output-FeedBack (OFB)
218 protected virtual void OFB (byte[] input, byte[] output)
220 throw new CryptographicException ("OFB isn't supported by the framework");
223 // Cipher Text Stealing (CTS)
224 protected virtual void CTS (byte[] input, byte[] output)
226 throw new CryptographicException ("CTS isn't supported by the framework");
230 private void CheckInput (byte[] inputBuffer, int inputOffset, int inputCount)
232 if (inputBuffer == null)
233 throw new ArgumentNullException ("inputBuffer");
235 throw new ArgumentOutOfRangeException ("inputOffset", "< 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"));
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)
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");
255 // ordered to avoid possible integer overflow
256 int len = outputBuffer.Length - inputCount - outputOffset;
258 // only PKCS7 is supported Silverlight 2.0
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) {
265 if (0 > len + BlockSizeByte) {
266 throw new CryptographicException ("outputBuffer", Locale.GetText ("Overflow"));
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;
274 throw new CryptographicException ("outputBuffer", Locale.GetText ("Overflow"));
277 return InternalTransformBlock (inputBuffer, inputOffset, inputCount, outputBuffer, outputOffset);
280 private bool KeepLastBlock {
283 // only PKCS7 is supported Silverlight 2.0
286 return ((!encrypt) && (algo.Padding != PaddingMode.None) && (algo.Padding != PaddingMode.Zeros));
291 private int InternalTransformBlock (byte[] inputBuffer, int inputOffset, int inputCount, byte[] outputBuffer, int outputOffset)
293 int offs = inputOffset;
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.");
302 full = inputCount / BlockSizeByte;
313 Transform (workBuff, workout);
314 Buffer.BlockCopy (workout, 0, outputBuffer, outputOffset, BlockSizeByte);
315 outputOffset += BlockSizeByte;
316 total += BlockSizeByte;
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;
330 Buffer.BlockCopy (inputBuffer, offs, workBuff, 0, BlockSizeByte);
338 RandomNumberGenerator _rng;
340 private void Random (byte[] buffer, int start, int length)
343 _rng = RandomNumberGenerator.Create ();
345 byte[] random = new byte [length];
346 _rng.GetBytes (random);
347 Buffer.BlockCopy (random, 0, buffer, start, length);
350 private void ThrowBadPaddingException (PaddingMode padding, int length, int position)
352 string msg = String.Format (Locale.GetText ("Bad {0} padding."), padding);
354 msg += String.Format (Locale.GetText (" Invalid length {0}."), length);
356 msg += String.Format (Locale.GetText (" Error found at position {0}."), position);
357 throw new CryptographicException (msg);
361 private byte[] FinalEncrypt (byte[] inputBuffer, int inputOffset, int inputCount)
363 // are there still full block to process ?
364 int full = (inputCount / BlockSizeByte) * BlockSizeByte;
365 int rem = inputCount - full;
369 // only PKCS7 is supported Silverlight 2.0
370 total += BlockSizeByte;
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;
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;
390 inputCount = paddedInput.Length;
397 byte[] res = new byte [total];
398 int outputOffset = 0;
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;
408 // now we only have a single last block to encrypt
409 byte padding = (byte) (BlockSizeByte - rem);
411 // only PKCS7 is supported Silverlight 2.0
412 for (int i = res.Length; --i >= (res.Length - padding);)
414 Buffer.BlockCopy (inputBuffer, inputOffset, res, full, rem);
415 InternalTransformBlock (res, full, BlockSizeByte, res, full);
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);
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);
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);)
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);
442 InternalTransformBlock (inputBuffer, inputOffset, BlockSizeByte, res, outputOffset);
449 private byte[] FinalDecrypt (byte[] inputBuffer, int inputOffset, int inputCount)
451 if ((inputCount % BlockSizeByte) > 0)
452 throw new CryptographicException ("Invalid input block size.");
454 int total = inputCount;
456 total += BlockSizeByte;
458 byte[] res = new byte [total];
459 int outputOffset = 0;
461 while (inputCount > 0) {
462 int len = InternalTransformBlock (inputBuffer, inputOffset, BlockSizeByte, res, outputOffset);
463 inputOffset += BlockSizeByte;
465 inputCount -= BlockSizeByte;
469 Transform (workBuff, workout);
470 Buffer.BlockCopy (workout, 0, res, outputOffset, BlockSizeByte);
471 outputOffset += BlockSizeByte;
475 // total may be 0 (e.g. PaddingMode.None)
476 byte padding = ((total > 0) ? res [total - 1] : (byte) 0);
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));
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);
497 case PaddingMode.ISO10126:
498 if ((padding == 0) || (padding > BlockSizeByte))
499 ThrowBadPaddingException (algo.Padding, padding, -1);
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);
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
517 // return output without padding
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);
529 public virtual byte[] TransformFinalBlock (byte[] inputBuffer, int inputOffset, int inputCount)
532 throw new ObjectDisposedException ("Object is disposed");
533 CheckInput (inputBuffer, inputOffset, inputCount);
536 return FinalEncrypt (inputBuffer, inputOffset, inputCount);
538 return FinalDecrypt (inputBuffer, inputOffset, inputCount);