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) 2004-2005 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
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:
19 // The above copyright notice and this permission notice shall be
20 // included in all copies or substantial portions of the Software.
22 // THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
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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 private int BlockSizeByte;
51 private byte[] workBuff;
52 private byte[] workout;
53 private int FeedBackByte;
54 private int FeedBackIter;
55 private bool m_disposed = false;
56 private bool lastBlock;
58 public SymmetricTransform (SymmetricAlgorithm symmAlgo, bool encryption, byte[] rgbIV)
62 BlockSizeByte = (algo.BlockSize >> 3);
65 rgbIV = KeyBuilder.IV (BlockSizeByte);
67 rgbIV = (byte[]) rgbIV.Clone ();
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);
78 temp = new byte [BlockSizeByte];
79 Buffer.BlockCopy (rgbIV, 0, temp, 0, System.Math.Min (BlockSizeByte, rgbIV.Length));
80 temp2 = new byte [BlockSizeByte];
81 FeedBackByte = (algo.FeedbackSize >> 3);
82 if (FeedBackByte != 0)
83 FeedBackIter = (int) BlockSizeByte / FeedBackByte;
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 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 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 void Transform (byte[] input, byte[] output)
153 throw new NotImplementedException ("Unkown CipherMode" + algo.Mode.ToString ());
157 // Electronic Code Book (ECB)
158 protected abstract void ECB (byte[] input, byte[] output);
160 // Cipher-Block-Chaining (CBC)
161 protected virtual void CBC (byte[] input, byte[] output)
164 for (int i = 0; i < BlockSizeByte; i++)
167 Buffer.BlockCopy (output, 0, temp, 0, BlockSizeByte);
170 Buffer.BlockCopy (input, 0, temp2, 0, BlockSizeByte);
172 for (int i = 0; i < BlockSizeByte; i++)
173 output[i] ^= temp[i];
174 Buffer.BlockCopy (temp2, 0, temp, 0, BlockSizeByte);
178 // Cipher-FeedBack (CFB)
179 protected virtual void CFB (byte[] input, byte[] output)
182 for (int x = 0; x < FeedBackIter; x++) {
183 // temp is first initialized with the IV
186 for (int i = 0; i < FeedBackByte; i++)
187 output[i + x] = (byte)(temp2[i] ^ input[i + x]);
188 Buffer.BlockCopy (temp, FeedBackByte, temp, 0, BlockSizeByte - FeedBackByte);
189 Buffer.BlockCopy (output, x, temp, BlockSizeByte - FeedBackByte, FeedBackByte);
193 for (int x = 0; x < FeedBackIter; x++) {
194 // we do not really decrypt this data!
196 // temp is first initialized with the IV
200 Buffer.BlockCopy (temp, FeedBackByte, temp, 0, BlockSizeByte - FeedBackByte);
201 Buffer.BlockCopy (input, x, temp, BlockSizeByte - FeedBackByte, FeedBackByte);
202 for (int i = 0; i < FeedBackByte; i++)
203 output[i + x] = (byte)(temp2[i] ^ input[i + x]);
208 // Output-FeedBack (OFB)
209 protected virtual void OFB (byte[] input, byte[] output)
211 throw new CryptographicException ("OFB isn't supported by the framework");
214 // Cipher Text Stealing (CTS)
215 protected virtual void CTS (byte[] input, byte[] output)
217 throw new CryptographicException ("CTS isn't supported by the framework");
220 private void CheckInput (byte[] inputBuffer, int inputOffset, int inputCount)
222 if (inputBuffer == null)
223 throw new ArgumentNullException ("inputBuffer");
225 throw new ArgumentOutOfRangeException ("inputOffset", "< 0");
227 throw new ArgumentOutOfRangeException ("inputCount", "< 0");
228 // ordered to avoid possible integer overflow
229 if (inputOffset > inputBuffer.Length - inputCount)
230 throw new ArgumentException ("inputBuffer", Locale.GetText ("Overflow"));
233 // this method may get called MANY times so this is the one to optimize
234 public virtual int TransformBlock (byte[] inputBuffer, int inputOffset, int inputCount, byte[] outputBuffer, int outputOffset)
237 throw new ObjectDisposedException ("Object is disposed");
238 CheckInput (inputBuffer, inputOffset, inputCount);
239 // check output parameters
240 if (outputBuffer == null)
241 throw new ArgumentNullException ("outputBuffer");
242 if (outputOffset < 0)
243 throw new ArgumentOutOfRangeException ("outputOffset", "< 0");
244 // ordered to avoid possible integer overflow
245 if (outputOffset > outputBuffer.Length - inputCount)
246 throw new ArgumentException ("outputBuffer", Locale.GetText ("Overflow"));
248 return InternalTransformBlock (inputBuffer, inputOffset, inputCount, outputBuffer, outputOffset);
251 private bool KeepLastBlock {
253 return ((!encrypt) && (algo.Mode != CipherMode.ECB) && (algo.Padding != PaddingMode.None));
257 private int InternalTransformBlock (byte[] inputBuffer, int inputOffset, int inputCount, byte[] outputBuffer, int outputOffset)
259 int offs = inputOffset;
262 // this way we don't do a modulo every time we're called
263 // and we may save a division
264 if (inputCount != BlockSizeByte) {
265 if ((inputCount % BlockSizeByte) != 0)
266 throw new CryptographicException ("Invalid input block size.");
268 full = inputCount / BlockSizeByte;
279 Transform (workBuff, workout);
280 Buffer.BlockCopy (workout, 0, outputBuffer, outputOffset, BlockSizeByte);
281 outputOffset += BlockSizeByte;
282 total += BlockSizeByte;
286 for (int i = 0; i < full; i++) {
287 Buffer.BlockCopy (inputBuffer, offs, workBuff, 0, BlockSizeByte);
288 Transform (workBuff, workout);
289 Buffer.BlockCopy (workout, 0, outputBuffer, outputOffset, BlockSizeByte);
290 offs += BlockSizeByte;
291 outputOffset += BlockSizeByte;
292 total += BlockSizeByte;
296 Buffer.BlockCopy (inputBuffer, offs, workBuff, 0, BlockSizeByte);
304 RandomNumberGenerator _rng;
306 private void Random (byte[] buffer, int start, int length)
309 _rng = RandomNumberGenerator.Create ();
311 byte[] random = new byte [length];
312 _rng.GetBytes (random);
313 Buffer.BlockCopy (random, 0, buffer, start, length);
316 private void ThrowBadPaddingException (PaddingMode padding, int length, int position)
318 string msg = String.Format (Locale.GetText ("Bad {0} padding."), padding);
320 msg += String.Format (Locale.GetText (" Invalid length {0}."), length);
322 msg += String.Format (Locale.GetText (" Error found at position {0}."), position);
323 throw new CryptographicException (msg);
327 private byte[] FinalEncrypt (byte[] inputBuffer, int inputOffset, int inputCount)
329 // are there still full block to process ?
330 int full = (inputCount / BlockSizeByte) * BlockSizeByte;
331 int rem = inputCount - full;
334 switch (algo.Padding) {
336 case PaddingMode.ANSIX923:
337 case PaddingMode.ISO10126:
339 case PaddingMode.PKCS7:
340 // we need to add an extra block for padding
341 total += BlockSizeByte;
347 if (algo.Padding == PaddingMode.None)
348 throw new CryptographicException ("invalid block length");
349 // zero padding the input (by adding a block for the partial data)
350 byte[] paddedInput = new byte [full + BlockSizeByte];
351 Buffer.BlockCopy (inputBuffer, inputOffset, paddedInput, 0, inputCount);
352 inputBuffer = paddedInput;
354 inputCount = paddedInput.Length;
360 byte[] res = new byte [total];
361 int outputOffset = 0;
363 // process all blocks except the last (final) block
364 while (total > BlockSizeByte) {
365 InternalTransformBlock (inputBuffer, inputOffset, BlockSizeByte, res, outputOffset);
366 inputOffset += BlockSizeByte;
367 outputOffset += BlockSizeByte;
368 total -= BlockSizeByte;
371 // now we only have a single last block to encrypt
372 byte padding = (byte) (BlockSizeByte - rem);
373 switch (algo.Padding) {
375 case PaddingMode.ANSIX923:
376 // XX 00 00 00 00 00 00 07 (zero + padding length)
377 res [res.Length - 1] = padding;
378 Buffer.BlockCopy (inputBuffer, inputOffset, res, full, rem);
379 // the last padded block will be transformed in-place
380 InternalTransformBlock (res, full, BlockSizeByte, res, full);
382 case PaddingMode.ISO10126:
383 // XX 3F 52 2A 81 AB F7 07 (random + padding length)
384 Random (res, res.Length - padding, padding - 1);
385 res [res.Length - 1] = padding;
386 Buffer.BlockCopy (inputBuffer, inputOffset, res, full, rem);
387 // the last padded block will be transformed in-place
388 InternalTransformBlock (res, full, BlockSizeByte, res, full);
391 case PaddingMode.PKCS7:
392 // XX 07 07 07 07 07 07 07 (padding length)
393 for (int i = res.Length; --i >= (res.Length - padding);)
395 Buffer.BlockCopy (inputBuffer, inputOffset, res, full, rem);
396 // the last padded block will be transformed in-place
397 InternalTransformBlock (res, full, BlockSizeByte, res, full);
400 InternalTransformBlock (inputBuffer, inputOffset, BlockSizeByte, res, outputOffset);
406 private byte[] FinalDecrypt (byte[] inputBuffer, int inputOffset, int inputCount)
408 if ((inputCount % BlockSizeByte) > 0)
409 throw new CryptographicException ("Invalid input block size.");
411 int total = inputCount;
413 total += BlockSizeByte;
415 byte[] res = new byte [total];
416 int outputOffset = 0;
418 while (inputCount > 0) {
419 int len = InternalTransformBlock (inputBuffer, inputOffset, BlockSizeByte, res, outputOffset);
420 inputOffset += BlockSizeByte;
422 inputCount -= BlockSizeByte;
426 Transform (workBuff, workout);
427 Buffer.BlockCopy (workout, 0, res, outputOffset, BlockSizeByte);
428 outputOffset += BlockSizeByte;
432 // total may be 0 (e.g. PaddingMode.None)
433 byte padding = ((total > 0) ? res [total - 1] : (byte) 0);
434 switch (algo.Padding) {
436 case PaddingMode.ANSIX923:
437 if ((padding == 0) || (padding > BlockSizeByte))
438 ThrowBadPaddingException (algo.Padding, padding, -1);
439 for (int i=padding; i > 0; i--) {
440 if (res [total - 1 - i] != 0x00)
441 ThrowBadPaddingException (algo.Padding, -1, i);
445 case PaddingMode.ISO10126:
446 if ((padding == 0) || (padding > BlockSizeByte))
447 ThrowBadPaddingException (algo.Padding, padding, -1);
450 case PaddingMode.PKCS7:
451 if ((padding == 0) || (padding > BlockSizeByte))
452 ThrowBadPaddingException (algo.Padding, padding, -1);
453 for (int i=padding - 1; i > 0; i--) {
454 if (res [total - 1 - i] != padding)
455 ThrowBadPaddingException (algo.Padding, -1, i);
460 case PaddingMode.PKCS7:
464 case PaddingMode.None: // nothing to do - it's a multiple of block size
465 case PaddingMode.Zeros: // nothing to do - user must unpad himself
469 // return output without padding
471 byte[] data = new byte [total];
472 Buffer.BlockCopy (res, 0, data, 0, total);
473 // zeroize decrypted data (copy with padding)
474 Array.Clear (res, 0, res.Length);
481 public virtual byte[] TransformFinalBlock (byte[] inputBuffer, int inputOffset, int inputCount)
484 throw new ObjectDisposedException ("Object is disposed");
485 CheckInput (inputBuffer, inputOffset, inputCount);
488 return FinalEncrypt (inputBuffer, inputOffset, inputCount);
490 return FinalDecrypt (inputBuffer, inputOffset, inputCount);