public override bool TransformOneShot(ReadOnlySpan <byte> input, Span <byte> output, out int bytesWritten)
{
int ciphertextLength = GetCiphertextLength(input.Length);
if (output.Length < ciphertextLength)
{
bytesWritten = 0;
return(false);
}
// Copy the input to the output, and apply padding if required. This will not throw since the
// output length has already been checked, and PadBlock will not copy from input to output
// until it has checked that it will be able to apply padding correctly.
int padWritten = PadBlock(input, output);
// Do an in-place encrypt. All of our implementations support this, either natively
// or making a temporary buffer themselves if in-place is not supported by the native
// implementation.
Span <byte> paddedOutput = output.Slice(0, padWritten);
bytesWritten = BasicSymmetricCipher.TransformFinal(paddedOutput, paddedOutput);
// After padding, we should have an even number of blocks, and the same applies
// to the transform.
Debug.Assert(padWritten == bytesWritten);
return(true);
}
public override unsafe bool TransformOneShot(ReadOnlySpan <byte> input, Span <byte> output, out int bytesWritten)
{
if (input.Length % PaddingSizeBytes != 0)
{
throw new CryptographicException(SR.Cryptography_PartialBlock);
}
// If there is no padding that needs to be removed, and the output buffer is large enough to hold
// the resulting plaintext, we can decrypt directly in to the output buffer.
// We do not do this for modes that require padding removal.
//
// This is not done for padded ciphertexts because we don't know if the padding is valid
// until it's been decrypted. We don't want to decrypt in to a user-supplied buffer and then throw
// a padding exception after we've already filled the user buffer with plaintext. We should only
// release the plaintext to the caller once we know the padding is valid.
if (!SymmetricPadding.DepaddingRequired(PaddingMode))
{
if (output.Length >= input.Length)
{
bytesWritten = BasicSymmetricCipher.TransformFinal(input, output);
return(true);
}
// If no padding is going to be removed, we know the buffer is too small and we can bail out.
bytesWritten = 0;
return(false);
}
byte[] rentedBuffer = CryptoPool.Rent(input.Length);
Span <byte> buffer = rentedBuffer.AsSpan(0, input.Length);
Span <byte> decryptedBuffer = default;
fixed(byte *pBuffer = buffer)
{
try
{
int transformWritten = BasicSymmetricCipher.TransformFinal(input, buffer);
decryptedBuffer = buffer.Slice(0, transformWritten);
// validates padding
int unpaddedLength = SymmetricPadding.GetPaddingLength(decryptedBuffer, PaddingMode, InputBlockSize);
if (unpaddedLength > output.Length)
{
bytesWritten = 0;
return(false);
}
decryptedBuffer.Slice(0, unpaddedLength).CopyTo(output);
bytesWritten = unpaddedLength;
return(true);
}
finally
{
CryptographicOperations.ZeroMemory(decryptedBuffer);
CryptoPool.Return(rentedBuffer, clearSize: 0); // ZeroMemory clears the part of the buffer that was written to.
}
}
}
protected sealed override byte[] UncheckedTransformFinalBlock(byte[] inputBuffer, int inputOffset, int inputCount)
{
// We can't complete decryption on a partial block
if (inputCount % InputBlockSize != 0)
{
throw new CryptographicException(SR.Cryptography_PartialBlock);
}
//
// If we have postponed cipher bits from the prior round, copy that into the decryption buffer followed by the input data.
// Otherwise the decryption buffer is just the input data.
//
byte[]? ciphertext = null;
if (_heldoverCipher == null)
{
ciphertext = new byte[inputCount];
Buffer.BlockCopy(inputBuffer, inputOffset, ciphertext, 0, inputCount);
}
else
{
ciphertext = new byte[_heldoverCipher.Length + inputCount];
Buffer.BlockCopy(_heldoverCipher, 0, ciphertext, 0, _heldoverCipher.Length);
Buffer.BlockCopy(inputBuffer, inputOffset, ciphertext, _heldoverCipher.Length, inputCount);
}
// Decrypt the data, then strip the padding to get the final decrypted data. Note that even if the cipherText length is 0, we must
// invoke TransformFinal() so that the cipher object knows to reset for the next cipher operation.
byte[] decryptedBytes = BasicSymmetricCipher.TransformFinal(ciphertext, 0, ciphertext.Length);
byte[] outputData;
if (ciphertext.Length > 0)
{
unsafe
{
fixed(byte *decryptedBytesPtr = decryptedBytes)
{
outputData = DepadBlock(decryptedBytes, 0, decryptedBytes.Length);
if (outputData != decryptedBytes)
{
CryptographicOperations.ZeroMemory(decryptedBytes);
}
}
}
}
else
{
outputData = Array.Empty <byte>();
}
Reset();
return(outputData);
}
protected override int UncheckedTransformFinalBlock(ReadOnlySpan <byte> inputBuffer, Span <byte> outputBuffer)
{
// The only caller of this method is the array-allocating overload, outputBuffer is
// always new memory, not a user-provided buffer.
Debug.Assert(!inputBuffer.Overlaps(outputBuffer));
int padWritten = PadBlock(inputBuffer, outputBuffer);
int transformWritten = BasicSymmetricCipher.TransformFinal(outputBuffer.Slice(0, padWritten), outputBuffer);
// After padding, we should have an even number of blocks, and the same applies
// to the transform.
Debug.Assert(padWritten == transformWritten);
return(transformWritten);
}
protected sealed override unsafe byte[] UncheckedTransformFinalBlock(byte[] inputBuffer, int inputOffset, int inputCount)
{
byte[] paddedBlock = PadBlock(inputBuffer, inputOffset, inputCount);
fixed(byte *paddedBlockPtr = paddedBlock)
{
byte[] output = BasicSymmetricCipher.TransformFinal(paddedBlock, 0, paddedBlock.Length);
if (paddedBlock != inputBuffer)
{
CryptographicOperations.ZeroMemory(paddedBlock);
}
return(output);
}
}
protected override unsafe int UncheckedTransformFinalBlock(ReadOnlySpan <byte> inputBuffer, Span <byte> outputBuffer)
{
// We can't complete decryption on a partial block
if (inputBuffer.Length % PaddingSizeBytes != 0)
{
throw new CryptographicException(SR.Cryptography_PartialBlock);
}
//
// If we have postponed cipher bits from the prior round, copy that into the decryption buffer followed by the input data.
// Otherwise the decryption buffer is just the input data.
//
ReadOnlySpan <byte> inputCiphertext;
Span <byte> ciphertext;
byte[]? rentedCiphertext = null;
int rentedCiphertextSize = 0;
try
{
if (_heldoverCipher == null)
{
rentedCiphertextSize = inputBuffer.Length;
rentedCiphertext = CryptoPool.Rent(inputBuffer.Length);
ciphertext = rentedCiphertext.AsSpan(0, inputBuffer.Length);
inputCiphertext = inputBuffer;
}
else
{
rentedCiphertextSize = _heldoverCipher.Length + inputBuffer.Length;
rentedCiphertext = CryptoPool.Rent(rentedCiphertextSize);
ciphertext = rentedCiphertext.AsSpan(0, rentedCiphertextSize);
_heldoverCipher.AsSpan().CopyTo(ciphertext);
inputBuffer.CopyTo(ciphertext.Slice(_heldoverCipher.Length));
// Decrypt in-place
inputCiphertext = ciphertext;
}
int unpaddedLength = 0;
fixed(byte *pCiphertext = ciphertext)
{
// Decrypt the data, then strip the padding to get the final decrypted data. Note that even if the cipherText length is 0, we must
// invoke TransformFinal() so that the cipher object knows to reset for the next cipher operation.
int decryptWritten = BasicSymmetricCipher.TransformFinal(inputCiphertext, ciphertext);
Span <byte> decryptedBytes = ciphertext.Slice(0, decryptWritten);
if (decryptedBytes.Length > 0)
{
unpaddedLength = SymmetricPadding.GetPaddingLength(decryptedBytes, PaddingMode, InputBlockSize);
decryptedBytes.Slice(0, unpaddedLength).CopyTo(outputBuffer);
}
}
Reset();
return(unpaddedLength);
}
finally
{
if (rentedCiphertext != null)
{
CryptoPool.Return(rentedCiphertext, clearSize: rentedCiphertextSize);
}
}
}
protected sealed override byte[] UncheckedTransformFinalBlock(byte[] inputBuffer, int inputOffset, int inputCount)
{
byte[] paddedBlock = PadBlock(inputBuffer, inputOffset, inputCount);
byte[] output = BasicSymmetricCipher.TransformFinal(paddedBlock, 0, paddedBlock.Length);
return(output);
}