// rdpthread.exe - RDP Credential Validator for FastRDP-NG
// Uses Windows WNetAddConnection2 API to validate credentials
// against the remote machine's IPC$ share.
//
// Compilation: csc.exe /target:exe /out:rdpthread.exe rdpthread.cs
// or via build.bat
//
// Usage: rdpthread.exe <ip> <port> <username> <password>
// Returns: exit code 0 + prints "success" on valid credentials
//          exit code 1 on failure (invalid, timeout, unreachable)

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

namespace RDPThread
{
    class Program
    {
        // ── Win32 P/Invoke ──────────────────────────────────────
        [DllImport("mpr.dll", CharSet = CharSet.Unicode, SetLastError = true)]
        private static extern int WNetAddConnection2(
            ref NETRESOURCE netResource,
            string password,
            string username,
            int flags
        );

        [DllImport("mpr.dll", CharSet = CharSet.Unicode, SetLastError = true)]
        private static extern int WNetCancelConnection2(
            string name,
            int flags,
            bool force
        );

        [DllImport("ws2_32.dll", CharSet = CharSet.Ansi)]
        private static extern IntPtr socket(int af, int type, int protocol);

        [DllImport("ws2_32.dll", CharSet = CharSet.Ansi)]
        private static extern int connect(IntPtr s, byte[] addr, int addrlen);

        [DllImport("ws2_32.dll", CharSet = CharSet.Ansi)]
        private static extern int closesocket(IntPtr s);

        [DllImport("ws2_32.dll")]
        private static extern int WSAStartup(ushort version, ref WSADATA data);

        [DllImport("ws2_32.dll")]
        private static extern int WSACleanup();

        [StructLayout(LayoutKind.Sequential, CharSet = CharSet.Unicode)]
        private struct NETRESOURCE
        {
            public int dwScope;
            public int dwType;
            public int dwDisplayType;
            public int dwUsage;
            [MarshalAs(UnmanagedType.LPWStr)]
            public string lpLocalName;
            [MarshalAs(UnmanagedType.LPWStr)]
            public string lpRemoteName;
            [MarshalAs(UnmanagedType.LPWStr)]
            public string lpComment;
            [MarshalAs(UnmanagedType.LPWStr)]
            public string lpProvider;
        }

        [StructLayout(LayoutKind.Sequential)]
        private struct WSADATA
        {
            public ushort wVersion;
            public ushort wHighVersion;
            [MarshalAs(UnmanagedType.ByValTStr, SizeConst = 257)]
            public string szDescription;
            [MarshalAs(UnmanagedType.ByValTStr, SizeConst = 129)]
            public string szSystemStatus;
            public ushort iMaxSockets;
            public ushort iMaxUdpDg;
            public IntPtr lpVendorInfo;
        }

        [StructLayout(LayoutKind.Sequential)]
        private struct sockaddr_in
        {
            public short sin_family;
            public ushort sin_port;
            public uint sin_addr;
            [MarshalAs(UnmanagedType.ByValArray, SizeConst = 8)]
            public byte[] sin_zero;
        }

        private const int RESOURCETYPE_ANY = 0;
        private const int CONNECT_TEMPORARY = 4;
        private const int NO_ERROR = 0;
        private const int AF_INET = 2;
        private const int SOCK_STREAM = 1;
        private const int IPPROTO_TCP = 6;

        private const int ERROR_LOGON_FAILURE = 1326;
        private const int ERROR_ACCESS_DENIED = 5;
        private const int ERROR_BAD_NETPATH = 53;
        private const int ERROR_NETWORK_UNREACHABLE = 1231;
        private const int ERROR_INVALID_PASSWORD = 86;
        private const int ERROR_SESSION_CREDENTIAL_CONFLICT = 1219;

        // ── TCP connect check ──────────────────────────────────
        private static bool TcpConnect(string ip, int port, int timeoutMs = 3000)
        {
            try
            {
                WSADATA wsa = new WSADATA();
                if (WSAStartup(0x202, ref wsa) != 0)
                    return false;

                IntPtr s = socket(AF_INET, SOCK_STREAM, IPPROTO_TCP);
                if (s == (IntPtr)(-1))
                {
                    WSACleanup();
                    return false;
                }

                // Set non-blocking for timeout
                var addr = new sockaddr_in
                {
                    sin_family = AF_INET,
                    sin_port = (ushort)System.Net.IPAddress.HostToNetworkOrder((short)port),
                    sin_addr = BitConverter.ToUInt32(
                        System.Net.IPAddress.Parse(ip).GetAddressBytes(), 0),
                    sin_zero = new byte[8]
                };

                byte[] addrBytes = new byte[16];
                Buffer.BlockCopy(BitConverter.GetBytes(addr.sin_family), 0, addrBytes, 0, 2);
                Buffer.BlockCopy(BitConverter.GetBytes(addr.sin_port), 0, addrBytes, 2, 2);
                Buffer.BlockCopy(BitConverter.GetBytes(addr.sin_addr), 0, addrBytes, 4, 4);

                int result = connect(s, addrBytes, 16);
                closesocket(s);
                WSACleanup();

                return result == 0;
            }
            catch
            {
                return false;
            }
        }

        // ── Credential validation via IPC$ ────────────────────
        private static bool ValidateCredentials(string ip, string username, string password)
        {
            string remotePath = string.Format("\\\\{0}\\IPC$", ip);

            NETRESOURCE nr = new NETRESOURCE
            {
                dwScope = 0,
                dwType = RESOURCETYPE_ANY,
                dwDisplayType = 0,
                dwUsage = 0,
                lpLocalName = null,
                lpRemoteName = remotePath,
                lpComment = null,
                lpProvider = null
            };

            int result = WNetAddConnection2(ref nr, password, username, CONNECT_TEMPORARY);

            if (result == NO_ERROR)
            {
                // Success! Clean up the connection
                WNetCancelConnection2(remotePath, CONNECT_TEMPORARY, true);
                return true;
            }

            return false;
        }

        // ── Main ──────────────────────────────────────────────
        static int Main(string[] args)
        {
            if (args.Length < 4)
            {
                Console.Error.WriteLine("Usage: rdpthread.exe <ip> <port> <username> <password>");
                return 1;
            }

            string ip = args[0];
            int port = int.Parse(args[1]);
            string username = args[2];
            string password = args[3];

            // Step 1: Quick TCP connectivity check
            if (!TcpConnect(ip, port))
            {
                // Port not reachable - try IPC$ anyway (SMB uses port 445)
                // The WNetAddConnection2 will fail gracefully if unreachable
            }

            // Step 2: Validate credentials via IPC$ (SMB)
            // This uses Windows built-in authentication against the remote machine
            bool success = ValidateCredentials(ip, username, password);

            if (success)
            {
                Console.WriteLine("success");
                return 0;
            }

            return 1;
        }
    }
}