private static ICryptoTransform CreateCryptoTransform(SymmetricEncryptionSettings settings, Stream stream)
{
Check.NotNull(settings, nameof(settings));
Check.NotNull(stream, nameof(stream));
using var algorithm = SymmetricAlgorithmFactory.CreateSymmetricAlgorithm(settings);
if (settings.InitializationVector == null)
{
// Read the IV prepended to the message
byte[] buffer = new byte[algorithm.IV.Length];
int totalReadCount = 0;
while (totalReadCount < algorithm.IV.Length)
{
int readCount = stream.Read(buffer, totalReadCount, algorithm.IV.Length - totalReadCount);
if (readCount == 0)
{
break;
}
totalReadCount = totalReadCount + readCount;
}
algorithm.IV = buffer;
}
return(algorithm.CreateDecryptor());
}
/// <summary>
/// Initializes a new instance of the <see cref="SymmetricEncryptStream" /> class.
/// </summary>
/// <param name="stream">
/// The inner <see cref="Stream" /> to read the clear-text message from.
/// </param>
/// <param name="settings">
/// The <see cref="SymmetricEncryptionSettings" /> specifying the cryptographic algorithm settings.
/// </param>
public SymmetricEncryptStream(Stream stream, SymmetricEncryptionSettings settings)
{
Check.NotNull(stream, nameof(stream));
Check.NotNull(settings, nameof(settings));
_cryptoTransform = CreateCryptoTransform(settings);
_cryptoStream = new CryptoStream(stream, _cryptoTransform, CryptoStreamMode.Read);
}
private ICryptoTransform CreateCryptoTransform(SymmetricEncryptionSettings settings)
{
using var algorithm = SymmetricAlgorithmFactory.CreateSymmetricAlgorithm(settings);
if (settings.InitializationVector == null)
{
_prefixBuffer = algorithm.IV;
}
return(algorithm.CreateEncryptor());
}
public static SymmetricAlgorithm CreateSymmetricAlgorithm(SymmetricEncryptionSettings encryptionSettings)
{
var algorithm = SymmetricAlgorithm.Create(encryptionSettings.AlgorithmName);
if (encryptionSettings.BlockSize != null)
{
algorithm.BlockSize = encryptionSettings.BlockSize.Value;
}
if (encryptionSettings.FeedbackSize != null)
{
algorithm.FeedbackSize = encryptionSettings.FeedbackSize.Value;
}
if (encryptionSettings.BlockSize != null)
{
algorithm.BlockSize = encryptionSettings.BlockSize.Value;
}
if (encryptionSettings.InitializationVector != null)
{
algorithm.IV = encryptionSettings.InitializationVector;
}
algorithm.Key = encryptionSettings.Key;
if (encryptionSettings.CipherMode != null)
{
algorithm.Mode = encryptionSettings.CipherMode.Value;
}
if (encryptionSettings.PaddingMode != null)
{
algorithm.Padding = encryptionSettings.PaddingMode.Value;
}
return(algorithm);
}