protected override unsafe byte[] UncheckedTransformFinalBlock(byte[] inputBuffer, int inputOffset, int inputCount)
{
if (SymmetricPadding.DepaddingRequired(PaddingMode))
{
byte[] rented = CryptoPool.Rent(inputCount + InputBlockSize);
int written = 0;
fixed(byte *pRented = rented)
{
try
{
written = UncheckedTransformFinalBlock(inputBuffer.AsSpan(inputOffset, inputCount), rented);
return(rented.AsSpan(0, written).ToArray());
}
finally
{
CryptoPool.Return(rented, clearSize: written);
}
}
}
else
{
byte[] buffer = GC.AllocateUninitializedArray <byte>(inputCount);
int written = UncheckedTransformFinalBlock(inputBuffer.AsSpan(inputOffset, inputCount), buffer);
Debug.Assert(written == buffer.Length);
return(buffer);
}
}
public override bool TransformOneShot(ReadOnlySpan <byte> input, Span <byte> output, out int bytesWritten)
{
int ciphertextLength = SymmetricPadding.GetCiphertextLength(input.Length, PaddingSizeBytes, PaddingMode);
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 = SymmetricPadding.PadBlock(input, output, PaddingSizeBytes, PaddingMode);
// 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 override byte[] UncheckedTransformFinalBlock(byte[] inputBuffer, int inputOffset, int inputCount)
{
int ciphertextLength = SymmetricPadding.GetCiphertextLength(inputCount, PaddingSizeBytes, PaddingMode);
byte[] buffer = GC.AllocateUninitializedArray <byte>(ciphertextLength);
int written = UncheckedTransformFinalBlock(inputBuffer.AsSpan(inputOffset, inputCount), buffer);
Debug.Assert(written == buffer.Length);
return(buffer);
}
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 = SymmetricPadding.PadBlock(inputBuffer, outputBuffer, PaddingSizeBytes, PaddingMode);
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 override int UncheckedTransformBlock(ReadOnlySpan <byte> inputBuffer, Span <byte> outputBuffer)
{
//
// If we're decrypting, it's possible to be called with the last blocks of the data, and then
// have TransformFinalBlock called with an empty array. Since we don't know if this is the case,
// we won't decrypt the last block of the input until either TransformBlock or
// TransformFinalBlock is next called.
//
// We don't need to do this for PaddingMode.None because there is no padding to strip, and
// we also don't do this for PaddingMode.Zeros since there is no way for us to tell if the
// zeros at the end of a block are part of the plaintext or the padding.
//
int decryptedBytes = 0;
if (SymmetricPadding.DepaddingRequired(PaddingMode))
{
// If we have data saved from a previous call, decrypt that into the output first
if (_heldoverCipher != null)
{
int depadDecryptLength = BasicSymmetricCipher.Transform(_heldoverCipher, outputBuffer);
outputBuffer = outputBuffer.Slice(depadDecryptLength);
decryptedBytes += depadDecryptLength;
}
else
{
_heldoverCipher = new byte[InputBlockSize];
}
// Postpone the last block to the next round.
Debug.Assert(inputBuffer.Length >= _heldoverCipher.Length, "inputBuffer.Length >= _heldoverCipher.Length");
inputBuffer.Slice(inputBuffer.Length - _heldoverCipher.Length).CopyTo(_heldoverCipher);
inputBuffer = inputBuffer.Slice(0, inputBuffer.Length - _heldoverCipher.Length);
Debug.Assert(inputBuffer.Length % InputBlockSize == 0, "Did not remove whole blocks for depadding");
}
if (inputBuffer.Length > 0)
{
decryptedBytes += BasicSymmetricCipher.Transform(inputBuffer, outputBuffer);
}
return(decryptedBytes);
}
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);
}
}
}
public static unsafe bool OneShotDecrypt(
ILiteSymmetricCipher cipher,
PaddingMode paddingMode,
ReadOnlySpan <byte> input,
Span <byte> output,
out int bytesWritten)
{
if (input.Length % cipher.PaddingSizeInBytes != 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 = cipher.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 = cipher.TransformFinal(input, buffer);
decryptedBuffer = buffer.Slice(0, transformWritten);
// This intentionally passes in BlockSizeInBytes instead of PaddingSizeInBytes. This is so that
// "extra padded" CFB data can still be decrypted. The .NET Framework always padded CFB8 to the
// block size, not the feedback size. We want the one-shot to be able to continue to decrypt
// those ciphertexts, so for CFB8 we are more lenient on the number of allowed padding bytes.
int unpaddedLength = SymmetricPadding.GetPaddingLength(decryptedBuffer, paddingMode, cipher.BlockSizeInBytes); // validates padding
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.
}
}
}
