BasicSymmetricCipherCsp.cs

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using System;
using System.Security.Cryptography;
using Internal.NativeCrypto;
 
namespace Internal.Cryptography;
 
internal sealed class BasicSymmetricCipherCsp : Internal.Cryptography.BasicSymmetricCipher
{
    private readonly bool _encrypting;
 
    private SafeProvHandle _hProvider;
 
    private SafeKeyHandle _hKey;
 
    public BasicSymmetricCipherCsp(int algId, CipherMode cipherMode, int blockSizeInBytes, byte[] key, int effectiveKeyLength, bool addNoSaltFlag, byte[] iv, bool encrypting, int feedbackSize, int paddingSizeInBytes)
        : base(cipherMode.GetCipherIv(iv), blockSizeInBytes, paddingSizeInBytes)
    {
        _encrypting = encrypting;
        _hProvider = AcquireSafeProviderHandle();
        _hKey = ImportCspBlob(_hProvider, algId, key, addNoSaltFlag);
        CapiHelper.SetKeyParameter(_hKey, CapiHelper.CryptGetKeyParamQueryType.KP_MODE, (int)cipherMode);
        if (cipherMode == CipherMode.CFB)
        {
            CapiHelper.SetKeyParameter(_hKey, CapiHelper.CryptGetKeyParamQueryType.KP_MODE_BITS, feedbackSize);
        }
        byte[] cipherIv = cipherMode.GetCipherIv(iv);
        if (cipherIv != null)
        {
            CapiHelper.SetKeyParameter(_hKey, CapiHelper.CryptGetKeyParamQueryType.KP_IV, cipherIv);
        }
        if (effectiveKeyLength != 0)
        {
            CapiHelper.SetKeyParameter(_hKey, CapiHelper.CryptGetKeyParamQueryType.KP_EFFECTIVE_KEYLEN, effectiveKeyLength);
        }
    }
 
    protected override void Dispose(bool disposing)
    {
        if (disposing)
        {
            SafeKeyHandle hKey = _hKey;
            _hKey = null;
            hKey?.Dispose();
            SafeProvHandle hProvider = _hProvider;
            _hProvider = null;
            hProvider?.Dispose();
        }
        base.Dispose(disposing);
    }
 
    public override int Transform(ReadOnlySpan<byte> input, Span<byte> output)
    {
        return Transform(input, output, isFinal: false);
    }
 
    public override int TransformFinal(ReadOnlySpan<byte> input, Span<byte> output)
    {
        int result = 0;
        if (input.Length != 0)
        {
            result = Transform(input, output, isFinal: true);
        }
        Reset();
        return result;
    }
 
    private void Reset()
    {
        CapiHelper.EncryptData(_hKey, default(ReadOnlySpan<byte>), default(Span<byte>), isFinal: true);
    }
 
    private int Transform(ReadOnlySpan<byte> input, Span<byte> output, bool isFinal)
    {
        if (_encrypting)
        {
            return CapiHelper.EncryptData(_hKey, input, output, isFinal);
        }
        return CapiHelper.DecryptData(_hKey, input, output);
    }
 
    private static SafeKeyHandle ImportCspBlob(SafeProvHandle safeProvHandle, int algId, byte[] rawKey, bool addNoSaltFlag)
    {
        byte[] keyBlob = CapiHelper.ToPlainTextKeyBlob(algId, rawKey);
        CapiHelper.ImportKeyBlob(safeProvHandle, CspProviderFlags.NoFlags, addNoSaltFlag, keyBlob, out var safeKeyHandle);
        return safeKeyHandle;
    }
 
    private static SafeProvHandle AcquireSafeProviderHandle()
    {
        CspParameters cspParameters = new CspParameters(1);
        CapiHelper.AcquireCsp(cspParameters, out var safeProvHandle);
        return safeProvHandle;
    }
}