mcs/class/Mono.Security/Mono.Security.Protocol.Tls/RecordProtocol.cs

   1 // Transport Security Layer (TLS)
   2 // Copyright (c) 2003-2004 Carlos Guzman Alvarez
   3 // Copyright (C) 2006-2007 Novell, Inc (http://www.novell.com)
   4 //
   5 // Permission is hereby granted, free of charge, to any person obtaining
   6 // a copy of this software and associated documentation files (the
   7 // "Software"), to deal in the Software without restriction, including
   8 // without limitation the rights to use, copy, modify, merge, publish,
   9 // distribute, sublicense, and/or sell copies of the Software, and to
  10 // permit persons to whom the Software is furnished to do so, subject to
  11 // the following conditions:
  12 //
  13 // The above copyright notice and this permission notice shall be
  14 // included in all copies or substantial portions of the Software.
  15 //
  16 // THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
  17 // EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
  18 // MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
  19 // NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE
  20 // LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION
  21 // OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION
  22 // WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
  23 //
  24
  25 using System;
  26 using System.Collections;
  27 using System.IO;
  28 using System.Threading;
  29
  30 using Mono.Security.Protocol.Tls.Handshake;
  31
  32 namespace Mono.Security.Protocol.Tls
  33 {
  34         internal abstract class RecordProtocol
  35         {
  36                 #region Fields
  37
  38                 private static ManualResetEvent record_processing = new ManualResetEvent (true);
  39
  40                 protected Stream        innerStream;
  41                 protected Context       context;
  42
  43                 #endregion
  44
  45                 #region Properties
  46
  47                 public Context Context
  48                 {
  49                         get { return this.context; }
  50                         set { this.context = value; }
  51                 }
  52
  53                 #endregion
  54
  55                 #region Constructors
  56
  57                 public RecordProtocol(Stream innerStream, Context context)
  58                 {
  59                         this.innerStream                        = innerStream;
  60                         this.context                            = context;
  61                         this.context.RecordProtocol = this;
  62                 }
  63
  64                 #endregion
  65
  66                 #region Abstract Methods
  67
  68                 public virtual void SendRecord(HandshakeType type)
  69                 {
  70
  71                         IAsyncResult ar = this.BeginSendRecord(type, null, null);
  72
  73                         this.EndSendRecord(ar);
  74
  75                 }
  76
  77                 protected abstract void ProcessHandshakeMessage(TlsStream handMsg);
  78
  79                 protected virtual void ProcessChangeCipherSpec ()
  80                 {
  81                         Context ctx = this.Context;
  82
  83                         // Reset sequence numbers
  84                         ctx.ReadSequenceNumber = 0;
  85
  86                         if (ctx is ClientContext) {
  87                                 ctx.EndSwitchingSecurityParameters (true);
  88                         } else {
  89                                 ctx.StartSwitchingSecurityParameters (false);
  90                         }
  91                 }
  92
  93                 public virtual HandshakeMessage GetMessage(HandshakeType type)
  94                 {
  95                         throw new NotSupportedException();
  96                 }
  97
  98                 #endregion
  99
 100                 #region Receive Record Async Result
 101                 private class ReceiveRecordAsyncResult : IAsyncResult
 102                 {
 103                         private object locker = new object ();
 104                         private AsyncCallback _userCallback;
 105                         private object _userState;
 106                         private Exception _asyncException;
 107                         private ManualResetEvent handle;
 108                         private byte[] _resultingBuffer;
 109                         private Stream _record;
 110                         private bool completed;
 111
 112                         private byte[] _initialBuffer;
 113
 114                         public ReceiveRecordAsyncResult(AsyncCallback userCallback, object userState, byte[] initialBuffer, Stream record)
 115                         {
 116                                 _userCallback = userCallback;
 117                                 _userState = userState;
 118                                 _initialBuffer = initialBuffer;
 119                                 _record = record;
 120                         }
 121
 122                         public Stream Record
 123                         {
 124                                 get { return _record; }
 125                         }
 126
 127                         public byte[] ResultingBuffer
 128                         {
 129                                 get { return _resultingBuffer; }
 130                         }
 131
 132                         public byte[] InitialBuffer
 133                         {
 134                                 get { return _initialBuffer; }
 135                         }
 136
 137                         public object AsyncState
 138                         {
 139                                 get { return _userState; }
 140                         }
 141
 142                         public Exception AsyncException
 143                         {
 144                                 get { return _asyncException; }
 145                         }
 146
 147                         public bool CompletedWithError
 148                         {
 149                                 get {
 150                                         if (!IsCompleted)
 151                                                 return false; // Perhaps throw InvalidOperationExcetion?
 152
 153                                         return null != _asyncException;
 154                                 }
 155                         }
 156
 157                         public WaitHandle AsyncWaitHandle
 158                         {
 159                                 get {
 160                                         lock (locker) {
 161                                                 if (handle == null)
 162                                                         handle = new ManualResetEvent (completed);
 163                                         }
 164                                         return handle;
 165                                 }
 166
 167                         }
 168
 169                         public bool CompletedSynchronously
 170                         {
 171                                 get { return false; }
 172                         }
 173
 174                         public bool IsCompleted
 175                         {
 176                                 get {
 177                                         lock (locker) {
 178                                                 return completed;
 179                                         }
 180                                 }
 181                         }
 182
 183                         private void SetComplete(Exception ex, byte[] resultingBuffer)
 184                         {
 185                                 lock (locker) {
 186                                         if (completed)
 187                                                 return;
 188
 189                                         completed = true;
 190                                         _asyncException = ex;
 191                                         _resultingBuffer = resultingBuffer;
 192                                         if (handle != null)
 193                                                 handle.Set ();
 194
 195                                         if (_userCallback != null)
 196                                                 _userCallback.BeginInvoke (this, null, null);
 197                                 }
 198                         }
 199
 200                         public void SetComplete(Exception ex)
 201                         {
 202                                 SetComplete(ex, null);
 203                         }
 204
 205                         public void SetComplete(byte[] resultingBuffer)
 206                         {
 207                                 SetComplete(null, resultingBuffer);
 208                         }
 209
 210                         public void SetComplete()
 211                         {
 212                                 SetComplete(null, null);
 213                         }
 214                 }
 215                 #endregion
 216
 217                 #region Receive Record Async Result
 218                 private class SendRecordAsyncResult : IAsyncResult
 219                 {
 220                         private object locker = new object ();
 221                         private AsyncCallback _userCallback;
 222                         private object _userState;
 223                         private Exception _asyncException;
 224                         private ManualResetEvent handle;
 225                         private HandshakeMessage _message;
 226                         private bool completed;
 227
 228                         public SendRecordAsyncResult(AsyncCallback userCallback, object userState, HandshakeMessage message)
 229                         {
 230                                 _userCallback = userCallback;
 231                                 _userState = userState;
 232                                 _message = message;
 233                         }
 234
 235                         public HandshakeMessage Message
 236                         {
 237                                 get { return _message; }
 238                         }
 239
 240                         public object AsyncState
 241                         {
 242                                 get { return _userState; }
 243                         }
 244
 245                         public Exception AsyncException
 246                         {
 247                                 get { return _asyncException; }
 248                         }
 249
 250                         public bool CompletedWithError
 251                         {
 252                                 get {
 253                                         if (!IsCompleted)
 254                                                 return false; // Perhaps throw InvalidOperationExcetion?
 255
 256                                         return null != _asyncException;
 257                                 }
 258                         }
 259
 260                         public WaitHandle AsyncWaitHandle
 261                         {
 262                                 get {
 263                                         lock (locker) {
 264                                                 if (handle == null)
 265                                                         handle = new ManualResetEvent (completed);
 266                                         }
 267                                         return handle;
 268                                 }
 269
 270                         }
 271
 272                         public bool CompletedSynchronously
 273                         {
 274                                 get { return false; }
 275                         }
 276
 277                         public bool IsCompleted
 278                         {
 279                                 get {
 280                                         lock (locker) {
 281                                                 return completed;
 282                                         }
 283                                 }
 284                         }
 285
 286                         public void SetComplete(Exception ex)
 287                         {
 288                                 lock (locker) {
 289                                         if (completed)
 290                                                 return;
 291
 292                                         completed = true;
 293                                         if (handle != null)
 294                                                 handle.Set ();
 295
 296                                         if (_userCallback != null)
 297                                                 _userCallback.BeginInvoke (this, null, null);
 298
 299                                         _asyncException = ex;
 300                                 }
 301                         }
 302
 303                         public void SetComplete()
 304                         {
 305                                 SetComplete(null);
 306                         }
 307                 }
 308                 #endregion
 309
 310                 #region Reveive Record Methods
 311
 312                 public IAsyncResult BeginReceiveRecord(Stream record, AsyncCallback callback, object state)
 313                 {
 314                         if (this.context.ConnectionEnd)
 315                         {
 316                                 throw new TlsException(
 317                                         AlertDescription.InternalError,
 318                                         "The session is finished and it's no longer valid.");
 319                         }
 320
 321                         record_processing.Reset ();
 322                         byte[] recordTypeBuffer = new byte[1];
 323
 324                         ReceiveRecordAsyncResult internalResult = new ReceiveRecordAsyncResult(callback, state, recordTypeBuffer, record);
 325
 326                         record.BeginRead(internalResult.InitialBuffer, 0, internalResult.InitialBuffer.Length, new AsyncCallback(InternalReceiveRecordCallback), internalResult);
 327
 328                         return internalResult;
 329                 }
 330
 331                 private void InternalReceiveRecordCallback(IAsyncResult asyncResult)
 332                 {
 333                         ReceiveRecordAsyncResult internalResult = asyncResult.AsyncState as ReceiveRecordAsyncResult;
 334                         Stream record = internalResult.Record;
 335
 336                         try
 337                         {
 338
 339                                 int bytesRead = internalResult.Record.EndRead(asyncResult);
 340
 341                                 //We're at the end of the stream. Time to bail.
 342                                 if (bytesRead == 0)
 343                                 {
 344                                         internalResult.SetComplete((byte[])null);
 345                                         return;
 346                                 }
 347
 348                                 // Try to read the Record Content Type
 349                                 int type = internalResult.InitialBuffer[0];
 350
 351                                 // Set last handshake message received to None
 352                                 this.context.LastHandshakeMsg = HandshakeType.ClientHello;
 353
 354                                 ContentType     contentType     = (ContentType)type;
 355                                 byte[] buffer = this.ReadRecordBuffer(type, record);
 356                                 if (buffer == null)
 357                                 {
 358                                         // record incomplete (at the moment)
 359                                         internalResult.SetComplete((byte[])null);
 360                                         return;
 361                                 }
 362
 363                                 // Decrypt message contents if needed
 364                                 if (contentType == ContentType.Alert && buffer.Length == 2)
 365                                 {
 366                                 }
 367                                 else if ((this.Context.Read != null) && (this.Context.Read.Cipher != null))
 368                                 {
 369                                         buffer = this.decryptRecordFragment (contentType, buffer);
 370                                         DebugHelper.WriteLine ("Decrypted record data", buffer);
 371                                 }
 372
 373                                 // Process record
 374                                 switch (contentType)
 375                                 {
 376                                         case ContentType.Alert:
 377                                                 this.ProcessAlert((AlertLevel)buffer [0], (AlertDescription)buffer [1]);
 378                                                 if (record.CanSeek)
 379                                                 {
 380                                                         // don't reprocess that memory block
 381                                                         record.SetLength (0);
 382                                                 }
 383                                                 buffer = null;
 384                                                 break;
 385
 386                                         case ContentType.ChangeCipherSpec:
 387                                                 this.ProcessChangeCipherSpec();
 388                                                 break;
 389
 390                                         case ContentType.ApplicationData:
 391                                                 break;
 392
 393                                         case ContentType.Handshake:
 394                                                 TlsStream message = new TlsStream (buffer);
 395                                                 while (!message.EOF)
 396                                                 {
 397                                                         this.ProcessHandshakeMessage(message);
 398                                                 }
 399                                                 break;
 400
 401                                         case (ContentType)0x80:
 402                                                 this.context.HandshakeMessages.Write (buffer);
 403                                                 break;
 404
 405                                         default:
 406                                                 throw new TlsException(
 407                                                         AlertDescription.UnexpectedMessage,
 408                                                         "Unknown record received from server.");
 409                                 }
 410
 411                                 internalResult.SetComplete(buffer);
 412                         }
 413                         catch (Exception ex)
 414                         {
 415                                 internalResult.SetComplete(ex);
 416                         }
 417
 418                 }
 419
 420                 public byte[] EndReceiveRecord(IAsyncResult asyncResult)
 421                 {
 422                         ReceiveRecordAsyncResult internalResult = asyncResult as ReceiveRecordAsyncResult;
 423
 424                         if (null == internalResult)
 425                                 throw new ArgumentException("Either the provided async result is null or was not created by this RecordProtocol.");
 426
 427                         if (!internalResult.IsCompleted)
 428                                 internalResult.AsyncWaitHandle.WaitOne();
 429
 430                         if (internalResult.CompletedWithError)
 431                                 throw internalResult.AsyncException;
 432
 433                         byte[] result = internalResult.ResultingBuffer;
 434                         record_processing.Set ();
 435                         return result;
 436                 }
 437
 438                 public byte[] ReceiveRecord(Stream record)
 439                 {
 440
 441                         IAsyncResult ar = this.BeginReceiveRecord(record, null, null);
 442                         return this.EndReceiveRecord(ar);
 443
 444                 }
 445
 446                 private byte[] ReadRecordBuffer (int contentType, Stream record)
 447                 {
 448                         switch (contentType)
 449                         {
 450                                 case 0x80:
 451                                         return this.ReadClientHelloV2(record);
 452
 453                                 default:
 454                                         if (!Enum.IsDefined(typeof(ContentType), (ContentType)contentType))
 455                                         {
 456                                                 throw new TlsException(AlertDescription.DecodeError);
 457                                         }
 458                                         return this.ReadStandardRecordBuffer(record);
 459                         }
 460                 }
 461
 462                 private byte[] ReadClientHelloV2 (Stream record)
 463                 {
 464                         int msgLength = record.ReadByte ();
 465                         // process further only if the whole record is available
 466                         if (record.CanSeek && (msgLength + 1 > record.Length))
 467                         {
 468                                 return null;
 469                         }
 470
 471                         byte[] message = new byte[msgLength];
 472                         record.Read (message, 0, msgLength);
 473
 474                         int msgType             = message [0];
 475                         if (msgType != 1)
 476                         {
 477                                 throw new TlsException(AlertDescription.DecodeError);
 478                         }
 479                         int protocol = (message [1] << 8 | message [2]);
 480                         int cipherSpecLength = (message [3] << 8 | message [4]);
 481                         int sessionIdLength = (message [5] << 8 | message [6]);
 482                         int challengeLength = (message [7] << 8 | message [8]);
 483                         int length = (challengeLength > 32) ? 32 : challengeLength;
 484
 485                         // Read CipherSpecs
 486                         byte[] cipherSpecV2 = new byte[cipherSpecLength];
 487                         Buffer.BlockCopy (message, 9, cipherSpecV2, 0, cipherSpecLength);
 488
 489                         // Read session ID
 490                         byte[] sessionId = new byte[sessionIdLength];
 491                         Buffer.BlockCopy (message, 9 + cipherSpecLength, sessionId, 0, sessionIdLength);
 492
 493                         // Read challenge ID
 494                         byte[] challenge = new byte[challengeLength];
 495                         Buffer.BlockCopy (message, 9 + cipherSpecLength + sessionIdLength, challenge, 0, challengeLength);
 496
 497                         if (challengeLength < 16 || cipherSpecLength == 0 || (cipherSpecLength % 3) != 0)
 498                         {
 499                                 throw new TlsException(AlertDescription.DecodeError);
 500                         }
 501
 502                         // Updated the Session ID
 503                         if (sessionId.Length > 0)
 504                         {
 505                                 this.context.SessionId = sessionId;
 506                         }
 507
 508                         // Update the protocol version
 509                         this.Context.ChangeProtocol((short)protocol);
 510
 511                         // Select the Cipher suite
 512                         this.ProcessCipherSpecV2Buffer(this.Context.SecurityProtocol, cipherSpecV2);
 513
 514                         // Updated the Client Random
 515                         this.context.ClientRandom = new byte [32]; // Always 32
 516                         // 1. if challenge is bigger than 32 bytes only use the last 32 bytes
 517                         // 2. right justify (0) challenge in ClientRandom if less than 32
 518                         Buffer.BlockCopy (challenge, challenge.Length - length, this.context.ClientRandom, 32 - length, length);
 519
 520                         // Set
 521                         this.context.LastHandshakeMsg = HandshakeType.ClientHello;
 522                         this.context.ProtocolNegotiated = true;
 523
 524                         return message;
 525                 }
 526
 527                 private byte[] ReadStandardRecordBuffer (Stream record)
 528                 {
 529                         byte[] header = new byte[4];
 530                         if (record.Read (header, 0, 4) != 4)
 531                                 throw new TlsException ("buffer underrun");
 532
 533                         short protocol = (short)((header [0] << 8) | header [1]);
 534                         short length = (short)((header [2] << 8) | header [3]);
 535
 536                         // process further only if the whole record is available
 537                         // note: the first 5 bytes aren't part of the length
 538                         if (record.CanSeek && (length + 5 > record.Length))
 539                         {
 540                                 return null;
 541                         }
 542
 543                         // Read Record data
 544                         int     totalReceived = 0;
 545                         byte[]  buffer          = new byte[length];
 546                         while (totalReceived != length)
 547                         {
 548                                 int justReceived = record.Read(buffer, totalReceived, buffer.Length - totalReceived);
 549
 550                                 //Make sure we get some data so we don't end up in an infinite loop here before shutdown.
 551                                 if (0 == justReceived)
 552                                 {
 553                                         throw new TlsException(AlertDescription.CloseNotify, "Received 0 bytes from stream. It must be closed.");
 554                                 }
 555
 556                                 totalReceived += justReceived;
 557                         }
 558
 559                         // Check that the message has a valid protocol version
 560                         if (protocol != this.context.Protocol && this.context.ProtocolNegotiated)
 561                         {
 562                                 throw new TlsException(
 563                                         AlertDescription.ProtocolVersion, "Invalid protocol version on message received");
 564                         }
 565
 566                         DebugHelper.WriteLine("Record data", buffer);
 567
 568                         return buffer;
 569                 }
 570
 571                 private void ProcessAlert(AlertLevel alertLevel, AlertDescription alertDesc)
 572                 {
 573                         switch (alertLevel)
 574                         {
 575                                 case AlertLevel.Fatal:
 576                                         throw new TlsException(alertLevel, alertDesc);
 577
 578                                 case AlertLevel.Warning:
 579                                 default:
 580                                 switch (alertDesc)
 581                                 {
 582                                         case AlertDescription.CloseNotify:
 583                                                 this.context.ConnectionEnd = true;
 584                                                 break;
 585                                 }
 586                                 break;
 587                         }
 588                 }
 589
 590                 #endregion
 591
 592                 #region Send Alert Methods
 593
 594                 public void SendAlert(AlertDescription description)
 595                 {
 596                         this.SendAlert(new Alert(description));
 597                 }
 598
 599                 public void SendAlert(
 600                         AlertLevel                      level,
 601                         AlertDescription        description)
 602                 {
 603                         this.SendAlert(new Alert(level, description));
 604                 }
 605
 606                 public void SendAlert(Alert alert)
 607                 {
 608                         AlertLevel level;
 609                         AlertDescription description;
 610                         bool close;
 611
 612                         if (alert == null) {
 613                                 DebugHelper.WriteLine(">>>> Write Alert NULL");
 614                                 level = AlertLevel.Fatal;
 615                                 description = AlertDescription.InternalError;
 616                                 close = true;
 617                         } else {
 618                                 DebugHelper.WriteLine(">>>> Write Alert ({0}|{1})", alert.Description, alert.Message);
 619                                 level = alert.Level;
 620                                 description = alert.Description;
 621                                 close = alert.IsCloseNotify;
 622                         }
 623
 624                         // Write record
 625                         this.SendRecord (ContentType.Alert, new byte[2] { (byte) level, (byte) description });
 626
 627                         if (close)
 628                         {
 629                                 this.context.ConnectionEnd = true;
 630                         }
 631                 }
 632
 633                 #endregion
 634
 635                 #region Send Record Methods
 636
 637                 public void SendChangeCipherSpec()
 638                 {
 639                         DebugHelper.WriteLine(">>>> Write Change Cipher Spec");
 640
 641                         // Send Change Cipher Spec message with the current cipher
 642                         // or as plain text if this is the initial negotiation
 643                         this.SendRecord(ContentType.ChangeCipherSpec, new byte[] {1});
 644
 645                         Context ctx = this.context;
 646
 647                         // Reset sequence numbers
 648                         ctx.WriteSequenceNumber = 0;
 649
 650                         // all further data sent will be encrypted with the negotiated
 651                         // security parameters (now the current parameters)
 652                         if (ctx is ClientContext) {
 653                                 ctx.StartSwitchingSecurityParameters (true);
 654                         } else {
 655                                 ctx.EndSwitchingSecurityParameters (false);
 656                         }
 657                 }
 658
 659                 public IAsyncResult BeginSendRecord(HandshakeType handshakeType, AsyncCallback callback, object state)
 660                 {
 661                         HandshakeMessage msg = this.GetMessage(handshakeType);
 662
 663                         msg.Process();
 664
 665                         DebugHelper.WriteLine(">>>> Write handshake record ({0}|{1})", context.Protocol, msg.ContentType);
 666
 667                         SendRecordAsyncResult internalResult = new SendRecordAsyncResult(callback, state, msg);
 668
 669                         this.BeginSendRecord(msg.ContentType, msg.EncodeMessage(), new AsyncCallback(InternalSendRecordCallback), internalResult);
 670
 671                         return internalResult;
 672                 }
 673
 674                 private void InternalSendRecordCallback(IAsyncResult ar)
 675                 {
 676                         SendRecordAsyncResult internalResult = ar.AsyncState as SendRecordAsyncResult;
 677
 678                         try
 679                         {
 680                                 this.EndSendRecord(ar);
 681
 682                                 // Update session
 683                                 internalResult.Message.Update();
 684
 685                                 // Reset message contents
 686                                 internalResult.Message.Reset();
 687
 688                                 internalResult.SetComplete();
 689                         }
 690                         catch (Exception ex)
 691                         {
 692                                 internalResult.SetComplete(ex);
 693                         }
 694                 }
 695
 696                 public IAsyncResult BeginSendRecord(ContentType contentType, byte[] recordData, AsyncCallback callback, object state)
 697                 {
 698                         if (this.context.ConnectionEnd)
 699                         {
 700                                 throw new TlsException(
 701                                         AlertDescription.InternalError,
 702                                         "The session is finished and it's no longer valid.");
 703                         }
 704
 705                         byte[] record = this.EncodeRecord(contentType, recordData);
 706
 707                         return this.innerStream.BeginWrite(record, 0, record.Length, callback, state);
 708                 }
 709
 710                 public void EndSendRecord(IAsyncResult asyncResult)
 711                 {
 712                         if (asyncResult is SendRecordAsyncResult)
 713                         {
 714                                 SendRecordAsyncResult internalResult = asyncResult as SendRecordAsyncResult;
 715                                 if (!internalResult.IsCompleted)
 716                                         internalResult.AsyncWaitHandle.WaitOne();
 717                                 if (internalResult.CompletedWithError)
 718                                         throw internalResult.AsyncException;
 719                         }
 720                         else
 721                         {
 722                                 this.innerStream.EndWrite(asyncResult);
 723                         }
 724                 }
 725
 726                 public void SendRecord(ContentType contentType, byte[] recordData)
 727                 {
 728                         IAsyncResult ar = this.BeginSendRecord(contentType, recordData, null, null);
 729
 730                         this.EndSendRecord(ar);
 731                 }
 732
 733                 public byte[] EncodeRecord(ContentType contentType, byte[] recordData)
 734                 {
 735                         return this.EncodeRecord(
 736                                 contentType,
 737                                 recordData,
 738                                 0,
 739                                 recordData.Length);
 740                 }
 741
 742                 public byte[] EncodeRecord(
 743                         ContentType     contentType,
 744                         byte[]          recordData,
 745                         int                     offset,
 746                         int                     count)
 747                 {
 748                         if (this.context.ConnectionEnd)
 749                         {
 750                                 throw new TlsException(
 751                                         AlertDescription.InternalError,
 752                                         "The session is finished and it's no longer valid.");
 753                         }
 754
 755                         TlsStream record = new TlsStream();
 756
 757                         int     position = offset;
 758
 759                         while (position < ( offset + count ))
 760                         {
 761                                 short   fragmentLength = 0;
 762                                 byte[]  fragment;
 763
 764                                 if ((count + offset - position) > Context.MAX_FRAGMENT_SIZE)
 765                                 {
 766                                         fragmentLength = Context.MAX_FRAGMENT_SIZE;
 767                                 }
 768                                 else
 769                                 {
 770                                         fragmentLength = (short)(count + offset - position);
 771                                 }
 772
 773                                 // Fill the fragment data
 774                                 fragment = new byte[fragmentLength];
 775                                 Buffer.BlockCopy(recordData, position, fragment, 0, fragmentLength);
 776
 777                                 if ((this.Context.Write != null) && (this.Context.Write.Cipher != null))
 778                                 {
 779                                         // Encrypt fragment
 780                                         fragment = this.encryptRecordFragment (contentType, fragment);
 781                                 }
 782
 783                                 // Write tls message
 784                                 record.Write((byte)contentType);
 785                                 record.Write(this.context.Protocol);
 786                                 record.Write((short)fragment.Length);
 787                                 record.Write(fragment);
 788
 789                                 DebugHelper.WriteLine("Record data", fragment);
 790
 791                                 // Update buffer position
 792                                 position += fragmentLength;
 793                         }
 794
 795                         return record.ToArray();
 796                 }
 797
 798                 #endregion
 799
 800                 #region Cryptography Methods
 801
 802                 private byte[] encryptRecordFragment(
 803                         ContentType     contentType,
 804                         byte[]          fragment)
 805                 {
 806                         byte[] mac      = null;
 807
 808                         // Calculate message MAC
 809                         if (this.Context is ClientContext)
 810                         {
 811                                 mac = this.context.Write.Cipher.ComputeClientRecordMAC(contentType, fragment);
 812                         }
 813                         else
 814                         {
 815                                 mac = this.context.Write.Cipher.ComputeServerRecordMAC (contentType, fragment);
 816                         }
 817
 818                         DebugHelper.WriteLine(">>>> Record MAC", mac);
 819
 820                         // Encrypt the message
 821                         byte[] ecr = this.context.Write.Cipher.EncryptRecord (fragment, mac);
 822
 823                         // Update sequence number
 824                         this.context.WriteSequenceNumber++;
 825
 826                         return ecr;
 827                 }
 828
 829                 private byte[] decryptRecordFragment(
 830                         ContentType     contentType,
 831                         byte[]          fragment)
 832                 {
 833                         byte[]  dcrFragment             = null;
 834                         byte[]  dcrMAC                  = null;
 835
 836                         try
 837                         {
 838                                 this.context.Read.Cipher.DecryptRecord (fragment, out dcrFragment, out dcrMAC);
 839                         }
 840                         catch
 841                         {
 842                                 if (this.context is ServerContext)
 843                                 {
 844                                         this.Context.RecordProtocol.SendAlert(AlertDescription.DecryptionFailed);
 845                                 }
 846
 847                                 throw;
 848                         }
 849
 850                         // Generate record MAC
 851                         byte[] mac = null;
 852
 853                         if (this.Context is ClientContext)
 854                         {
 855                                 mac = this.context.Read.Cipher.ComputeServerRecordMAC(contentType, dcrFragment);
 856                         }
 857                         else
 858                         {
 859                                 mac = this.context.Read.Cipher.ComputeClientRecordMAC (contentType, dcrFragment);
 860                         }
 861
 862                         DebugHelper.WriteLine(">>>> Record MAC", mac);
 863
 864                         // Check record MAC
 865                         if (!Compare (mac, dcrMAC))
 866                         {
 867                                 throw new TlsException(AlertDescription.BadRecordMAC, "Bad record MAC");
 868                         }
 869
 870                         // Update sequence number
 871                         this.context.ReadSequenceNumber++;
 872
 873                         return dcrFragment;
 874                 }
 875
 876                 private bool Compare (byte[] array1, byte[] array2)
 877                 {
 878                         if (array1 == null)
 879                                 return (array2 == null);
 880                         if (array2 == null)
 881                                 return false;
 882                         if (array1.Length != array2.Length)
 883                                 return false;
 884                         for (int i = 0; i < array1.Length; i++) {
 885                                 if (array1[i] != array2[i])
 886                                         return false;
 887                         }
 888                         return true;
 889                 }
 890
 891                 #endregion
 892
 893                 #region CipherSpecV2 processing
 894
 895                 private void ProcessCipherSpecV2Buffer (SecurityProtocolType protocol, byte[] buffer)
 896                 {
 897                         TlsStream codes = new TlsStream(buffer);
 898
 899                         string prefix = (protocol == SecurityProtocolType.Ssl3) ? "SSL_" : "TLS_";
 900
 901                         while (codes.Position < codes.Length)
 902                         {
 903                                 byte check = codes.ReadByte();
 904
 905                                 if (check == 0)
 906                                 {
 907                                         // SSL/TLS cipher spec
 908                                         short code = codes.ReadInt16();
 909                                         int index = this.Context.SupportedCiphers.IndexOf(code);
 910                                         if (index != -1)
 911                                         {
 912                                                 this.Context.Negotiating.Cipher = this.Context.SupportedCiphers[index];
 913                                                 break;
 914                                         }
 915                                 }
 916                                 else
 917                                 {
 918                                         byte[] tmp = new byte[2];
 919                                         codes.Read(tmp, 0, tmp.Length);
 920
 921                                         int tmpCode = ((check & 0xff) << 16) | ((tmp[0] & 0xff) << 8) | (tmp[1] & 0xff);
 922                                         CipherSuite cipher = this.MapV2CipherCode(prefix, tmpCode);
 923
 924                                         if (cipher != null)
 925                                         {
 926                                                 this.Context.Negotiating.Cipher = cipher;
 927                                                 break;
 928                                         }
 929                                 }
 930                         }
 931
 932                         if (this.Context.Negotiating == null)
 933                         {
 934                                 throw new TlsException(AlertDescription.InsuficientSecurity, "Insuficient Security");
 935                         }
 936                 }
 937
 938                 private CipherSuite MapV2CipherCode(string prefix, int code)
 939                 {
 940                         try
 941                         {
 942                                 switch (code)
 943                                 {
 944                                         case 65664:
 945                                                 // TLS_RC4_128_WITH_MD5
 946                                                 return this.Context.SupportedCiphers[prefix + "RSA_WITH_RC4_128_MD5"];
 947
 948                                         case 131200:
 949                                                 // TLS_RC4_128_EXPORT40_WITH_MD5
 950                                                 return this.Context.SupportedCiphers[prefix + "RSA_EXPORT_WITH_RC4_40_MD5"];
 951
 952                                         case 196736:
 953                                                 // TLS_RC2_CBC_128_CBC_WITH_MD5
 954                                                 return this.Context.SupportedCiphers[prefix + "RSA_EXPORT_WITH_RC2_CBC_40_MD5"];
 955
 956                                         case 262272:
 957                                                 // TLS_RC2_CBC_128_CBC_EXPORT40_WITH_MD5
 958                                                 return this.Context.SupportedCiphers[prefix + "RSA_EXPORT_WITH_RC2_CBC_40_MD5"];
 959
 960                                         case 327808:
 961                                                 // TLS_IDEA_128_CBC_WITH_MD5
 962                                                 return null;
 963
 964                                         case 393280:
 965                                                 // TLS_DES_64_CBC_WITH_MD5
 966                                                 return null;
 967
 968                                         case 458944:
 969                                                 // TLS_DES_192_EDE3_CBC_WITH_MD5
 970                                                 return null;
 971
 972                                         default:
 973                                                 return null;
 974                                 }
 975                         }
 976                         catch
 977                         {
 978                                 return null;
 979                         }
 980                 }
 981
 982                 #endregion
 983         }
 984 }