seraph/seraph/Seraph.Utility/crypt32.cs

namespace seraph.Seraph.Utility;

using System.Runtime.InteropServices;
using System.Text;
using System;

public static class Crypt32Wrapper
{
    [DllImport("crypt32.dll", SetLastError = true, CharSet = CharSet.Unicode)]
    private static extern bool CryptUnprotectData(
        ref DATA_BLOB pDataIn,
        out IntPtr ppszDataDescr,
        IntPtr pOptionalEntropy,
        IntPtr pvReserved,
        IntPtr pPromptStruct,
        int dwFlags,
        out DATA_BLOB pDataOut);

    [StructLayout(LayoutKind.Sequential)]
    private struct DATA_BLOB
    {
        public int cbData;
        public IntPtr pbData;
    }

    private const int CRYPTPROTECT_UI_FORBIDDEN = 0x1;

    public static string Decrypt(byte[] encryptedData)
    {
        if (encryptedData == null || encryptedData.Length == 0)
        {
            throw new ArgumentException("Encrypted data cannot be null or empty.");
        }

        var inBlob = new DATA_BLOB
        {
            cbData = encryptedData.Length,
            pbData = Marshal.AllocHGlobal(encryptedData.Length)
        };
        Marshal.Copy(encryptedData, 0, inBlob.pbData, encryptedData.Length);

        DATA_BLOB outBlob = new DATA_BLOB();
        IntPtr descriptionPtr = IntPtr.Zero;

        try
        {
            bool success = CryptUnprotectData(ref inBlob, out descriptionPtr, IntPtr.Zero, IntPtr.Zero, IntPtr.Zero,
                    CRYPTPROTECT_UI_FORBIDDEN, out outBlob);

            if (!success)
            {
                int errorCode = Marshal.GetLastWin32Error();
                throw new InvalidOperationException($"Decryption failed with error code: {errorCode}");
            }

            if (outBlob.pbData == IntPtr.Zero)
            {
                throw new InvalidOperationException("Decryption failed: outBlob.pbData is null.");
            }

            byte[] decryptedData = new byte[outBlob.cbData];
            Marshal.Copy(outBlob.pbData, decryptedData, 0, outBlob.cbData);
            return Encoding.UTF8.GetString(decryptedData);
        }
        finally
        {
            Marshal.FreeHGlobal(inBlob.pbData);
            if (outBlob.pbData != IntPtr.Zero)
            {
                    Marshal.FreeHGlobal(outBlob.pbData);
            }

            if (descriptionPtr != IntPtr.Zero)
            {
                Marshal.FreeHGlobal(descriptionPtr);
            }
        }
    }
}