protected void TryDecryptOneShot_DestinationTooSmallTest(byte[] plaintext, byte[] ciphertext, PaddingMode padding, CipherMode mode, int feedbackSize = 0)
{
if (plaintext.Length == 0)
{
// Can't have a ciphertext length shorter than zero.
return;
}
using (SymmetricAlgorithm alg = CreateAlgorithm())
{
alg.Key = Key;
Span <byte> destinationBuffer = new byte[plaintext.Length - 1];
int bytesWritten;
bool result = mode switch
{
CipherMode.ECB => alg.TryDecryptEcb(ciphertext, destinationBuffer, padding, out bytesWritten),
CipherMode.CBC => alg.TryDecryptCbc(ciphertext, IV, destinationBuffer, out bytesWritten, padding),
CipherMode.CFB => alg.TryDecryptCfb(ciphertext, IV, destinationBuffer, out bytesWritten, padding, feedbackSize),
_ => throw new NotImplementedException(),
};
Assert.False(result, "TryDecrypt");
Assert.Equal(0, bytesWritten);
}
}
protected void TryDecryptOneShot_DestinationLargerTest(byte[] plaintext, byte[] ciphertext, PaddingMode padding, CipherMode mode, int feedbackSize = 0)
{
using (SymmetricAlgorithm alg = CreateAlgorithm())
{
alg.Key = Key;
int expectedPlaintextSize = padding == PaddingMode.Zeros ? ciphertext.Length : plaintext.Length;
Span <byte> largeBuffer = new byte[expectedPlaintextSize + 10];
Span <byte> destinationBuffer = largeBuffer.Slice(0, expectedPlaintextSize);
largeBuffer.Fill(0xCC);
int bytesWritten;
bool result = mode switch
{
CipherMode.ECB => alg.TryDecryptEcb(ciphertext, destinationBuffer, padding, out bytesWritten),
CipherMode.CBC => alg.TryDecryptCbc(ciphertext, IV, destinationBuffer, out bytesWritten, padding),
CipherMode.CFB => alg.TryDecryptCfb(ciphertext, IV, destinationBuffer, out bytesWritten, padding, feedbackSize),
_ => throw new NotImplementedException(),
};
Assert.True(result, "TryDecrypt");
Assert.Equal(destinationBuffer.Length, bytesWritten);
AssertPlaintexts(plaintext, destinationBuffer, padding);
Span <byte> excess = largeBuffer.Slice(destinationBuffer.Length);
AssertExtensions.FilledWith <byte>(0xCC, excess);
}
}
public void DecryptOneShot_CfbFeedbackSizeNotSupported()
{
using (SymmetricAlgorithm alg = CreateAlgorithm())
{
Assert.ThrowsAny <CryptographicException>(() =>
alg.TryDecryptCfb(ReadOnlySpan <byte> .Empty, IV, Span <byte> .Empty, out _, feedbackSizeInBits: 48));
}
}