BasicSymmetricCipherNCrypt.cs

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using System;
using System.Security.Cryptography;
using System.Text;
using Microsoft.Win32.SafeHandles;
 
namespace Internal.Cryptography;
 
internal sealed class BasicSymmetricCipherNCrypt : Internal.Cryptography.BasicSymmetricCipher
{
    private CngKey _cngKey;
 
    private readonly bool _encrypting;
 
    private static readonly CngProperty s_ECBMode = new CngProperty("Chaining Mode", Encoding.Unicode.GetBytes("ChainingModeECB\0"), CngPropertyOptions.None);
 
    private static readonly CngProperty s_CBCMode = new CngProperty("Chaining Mode", Encoding.Unicode.GetBytes("ChainingModeCBC\0"), CngPropertyOptions.None);
 
    private static readonly CngProperty s_CFBMode = new CngProperty("Chaining Mode", Encoding.Unicode.GetBytes("ChainingModeCFB\0"), CngPropertyOptions.None);
 
    public BasicSymmetricCipherNCrypt(Func<CngKey> cngKeyFactory, CipherMode cipherMode, int blockSizeInBytes, byte[] iv, bool encrypting, int paddingSize)
        : base(iv, blockSizeInBytes, paddingSize)
    {
        _encrypting = encrypting;
        _cngKey = cngKeyFactory();
        CngProperty property = cipherMode switch
        {
            CipherMode.ECB => s_ECBMode, 
            CipherMode.CBC => s_CBCMode, 
            CipherMode.CFB => s_CFBMode, 
            _ => throw new CryptographicException(System.SR.Cryptography_InvalidCipherMode), 
        };
        _cngKey.SetProperty(property);
        Reset();
    }
 
    public unsafe sealed override int Transform(ReadOnlySpan<byte> input, Span<byte> output)
    {
        global::Interop.NCrypt.ErrorCode errorCode;
        int pcbResult;
        using (SafeNCryptKeyHandle hKey = _cngKey.Handle)
        {
            errorCode = (_encrypting ? global::Interop.NCrypt.NCryptEncrypt(hKey, input, input.Length, null, output, output.Length, out pcbResult, global::Interop.NCrypt.AsymmetricPaddingMode.None) : global::Interop.NCrypt.NCryptDecrypt(hKey, input, input.Length, null, output, output.Length, out pcbResult, global::Interop.NCrypt.AsymmetricPaddingMode.None));
        }
        if (errorCode != 0)
        {
            throw errorCode.ToCryptographicException();
        }
        if (pcbResult != input.Length)
        {
            throw new CryptographicException(System.SR.Cryptography_UnexpectedTransformTruncation);
        }
        return pcbResult;
    }
 
    public sealed override int TransformFinal(ReadOnlySpan<byte> input, Span<byte> output)
    {
        int result = 0;
        if (input.Length != 0)
        {
            result = Transform(input, output);
        }
        Reset();
        return result;
    }
 
    protected sealed override void Dispose(bool disposing)
    {
        if (disposing && _cngKey != null)
        {
            _cngKey.Dispose();
            _cngKey = null;
        }
        base.Dispose(disposing);
    }
 
    private void Reset()
    {
        if (base.IV != null)
        {
            CngProperty property = new CngProperty("IV", base.IV, CngPropertyOptions.None);
            _cngKey.SetProperty(property);
        }
    }
}