/// <summary>
/// Create and bind Encrypt-then-MAC scheme components for an item.
/// Adds finished decorator (cipher/encryptor) and authenticator to mux item resource container.
/// </summary>
/// <param name="item">Item to prepare resources for.</param>
private MuxItemResourceContainer CreateEtMSchemeResources(PayloadItem item)
{
CipherStream encryptor;
MacStream authenticator;
CreateEtMDecorator(item, out encryptor, out authenticator);
var container = new MuxItemResourceContainer(encryptor, authenticator,
_maxStripe + encryptor.OutputBufferSize);
return(container);
}
protected override void ExecuteOperation()
{
Debug.Assert(ItemCompletionRegister[Index] == false);
PayloadItem item = PayloadItems[Index];
Guid itemIdentifier = item.Identifier;
bool skip = ItemSkipRegister != null && ItemSkipRegister.Contains(itemIdentifier);
MuxItemResourceContainer itemContainer;
bool activeResource = _activeItemResources.ContainsKey(itemIdentifier);
if (activeResource)
{
itemContainer = _activeItemResources[itemIdentifier];
}
else
{
if (skip == false)
{
itemContainer = CreateEtMSchemeResources(item);
if (Writing)
{
EmitHeader(itemContainer.Authenticator);
}
else
{
ConsumeHeader(itemContainer.Authenticator);
}
}
else
{
itemContainer = new MuxItemResourceContainer(null, null, null);
}
_activeItemResources.Add(itemIdentifier, itemContainer);
}
int opLength = NextOperationLength();
if (skip == false)
{
CipherStream itemEncryptor = itemContainer.Encryptor;
MacStream itemAuthenticator = itemContainer.Authenticator;
if (Writing)
{
// Writing/multiplexing
if (itemEncryptor.BytesIn + opLength < item.ExternalLength)
{
// Normal operation
itemEncryptor.WriteExactly(item.StreamBinding, opLength);
}
else
{
// Final operation, or just prior to
if (itemContainer.Buffer.IsValueCreated == false)
{
// Redirect final ciphertext to buffer to account for possible expansion
itemAuthenticator.ReassignBinding(itemContainer.Buffer.Value, false, finish: false);
}
var remaining = (int)(item.ExternalLength - itemEncryptor.BytesIn);
if (remaining > 0)
{
while (remaining > 0)
{
int toRead = Math.Min(remaining, BufferSize);
int iterIn = item.StreamBinding.Read(Buffer, 0, toRead);
if (iterIn < toRead)
{
throw new EndOfStreamException();
}
itemEncryptor.Write(Buffer, 0, iterIn); // Writing into recently-lazy-inited buffer
remaining -= iterIn;
}
itemEncryptor.Close();
}
var toWrite = (int)Math.Min(opLength, itemContainer.Buffer.Value.Length);
Debug.Print(DebugUtility.CreateReportString("FabricPayloadMux", "ExecuteOperation",
"Multiplexing item: final stripe length", toWrite));
itemContainer.Buffer.Value.ReadTo(PayloadStream, toWrite);
}
}
else
{
// Reading/demultiplexing
long readRemaining = item.InternalLength - itemEncryptor.BytesIn;
bool finalOp = false;
if (readRemaining <= opLength)
{
// Final operation
opLength = (int)readRemaining;
finalOp = true;
Debug.Print(DebugUtility.CreateReportString("FabricPayloadMux", "ExecuteOperation",
"Demultiplexing item: final stripe length", opLength));
}
itemEncryptor.ReadExactly(item.StreamBinding, opLength, finalOp);
}
if ((Writing && itemEncryptor.BytesIn >= item.ExternalLength && itemContainer.Buffer.Value.Length == 0) ||
(Writing == false && itemEncryptor.BytesIn >= item.InternalLength))
{
// Now that we're finished we need to do some extra things, then clean up
FinishItem(item, itemEncryptor, itemAuthenticator);
}
}
else
{
// Skipping
Debug.Assert(Writing == false, "Should not be skipping when writing!");
if (itemContainer.SkippedLength == 0)
{
// Start of item
PayloadStream.Seek(opLength, SeekOrigin.Current);
itemContainer.SkippedLength += opLength;
}
else if (itemContainer.SkippedLength + opLength >= item.InternalLength)
{
int remainingToSkip = (int)(item.InternalLength - itemContainer.SkippedLength);
itemContainer.SkippedLength += remainingToSkip;
PayloadStream.Seek(remainingToSkip + GetTrailerLength(), SeekOrigin.Current);
// "Finish" item
_activeItemResources.Remove(item.Identifier);
// Mark the item as completed in the register
ItemCompletionRegister[Index] = true;
ItemsCompleted++;
Debug.Print(DebugUtility.CreateReportString("FabricPayloadMux", "ExecuteOperation", "[*** SKIPPED ITEM",
Index + " ***]"));
}
else
{
PayloadStream.Seek(opLength, SeekOrigin.Current);
itemContainer.SkippedLength += opLength;
}
}
}
