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// Licensed to the .NET Foundation under one or more agreements.
// The .NET Foundation licenses this file to you under the MIT license.

using System;
using System.Diagnostics;
using System.Runtime.CompilerServices;
using System.Runtime.InteropServices;
using Microsoft.Win32.SafeHandles;

internal static partial class Interop
{
    internal static partial class BCrypt
    {
        internal static unsafe IntPtr BCryptImportKey(IntPtr hAlg, ReadOnlySpan<byte> key)
        {
            const string BCRYPT_KEY_DATA_BLOB = "KeyDataBlob";
            int keySize = key.Length;
            int blobSize = sizeof(BCRYPT_KEY_DATA_BLOB_HEADER) + keySize;

// 64 is large enough to hold a BCRYPT_KEY_DATA_BLOB_HEADER and an AES-256 key with room to spare.
            int MaxStackKeyBlob = 64;
            Span<byte> blob = stackalloc byte[MaxStackKeyBlob];

if (blobSize > MaxStackKeyBlob)
            {
                blob = new byte[blobSize];
            }
            else
            {
                blob.Clear();
            }

fixed (byte* pbBlob = blob)
            {
                BCRYPT_KEY_DATA_BLOB_HEADER* pBlob = (BCRYPT_KEY_DATA_BLOB_HEADER*)pbBlob;
                pBlob->dwMagic = BCRYPT_KEY_DATA_BLOB_HEADER.BCRYPT_KEY_DATA_BLOB_MAGIC;
                pBlob->dwVersion = BCRYPT_KEY_DATA_BLOB_HEADER.BCRYPT_KEY_DATA_BLOB_VERSION1;
                pBlob->cbKeyData = (uint)keySize;

key.CopyTo(blob.Slice(sizeof(BCRYPT_KEY_DATA_BLOB_HEADER)));
                IntPtr hKey;
                uint ntStatus = BCryptImportKey(hAlg, IntPtr.Zero, BCRYPT_KEY_DATA_BLOB, out hKey, IntPtr.Zero, 0, pbBlob, blobSize, 0);
                if (ntStatus != 0)
                {
                    throw CreateCryptographicException(ntStatus);
                }

return hKey;
            }
        }

[StructLayout(LayoutKind.Sequential)]
        internal struct BCRYPT_KEY_DATA_BLOB_HEADER
        {
            public uint dwMagic;
            public uint dwVersion;
            public uint cbKeyData;

public const uint BCRYPT_KEY_DATA_BLOB_MAGIC = 0x4d42444b;
            public const uint BCRYPT_KEY_DATA_BLOB_VERSION1 = 0x1;
        }

internal static Exception CreateCryptographicException(uint ntStatus)
        {
            return new Exception("Stub code");
        }

[DllImport("BCrypt.dll", CharSet = CharSet.Unicode)]
        private static unsafe extern uint BCryptImportKey(IntPtr hAlgorithm, IntPtr hImportKey, string pszBlobType, out IntPtr hKey, IntPtr pbKeyObject, int cbKeyObject, byte* pbInput, int cbInput, int dwFlags);
    }
}