C# Programmatic Remote Folder / File Authentication In Non-Domain Windows Environment

Question

I need to be able to programmatically authenticate when trying to read and write files on a remote computer in a non-domain environment.

When you type a command into the Windows RUN prompt that is similar to \\targetComputer\C$\targetFolder or \\targetComputer\admin$, where the targetComputer is NOT on a domain, you will be prompted to enter a username and password. Once you enter the username and password, you have full access to the remote folder.

How can I accomplish this authentication programmatically in C#?

I've tried..

--Impersonation, but it appears to only work in a domain environment.

--CMDKEY.exe, but it also seems to only work in a domain environment.

There must be a way to do this, but I have searched high and low with no luck so far. Maybe I'm just looking for the wrong thing? I'm sure I'm not the first to have this question. Any help would be greatly appreciated.

Thanks!

EDIT :

I think I just found a different SO posting that answers my question: Accessing a Shared File (UNC) From a Remote, Non-Trusted Domain With Credentials

I will work with that for now and see where it gets me.

Thanks!

Answer 1

Impersonation works with Peer/LAN network as well. I got your typical home network with some machines on default "Workgroup" and some on a named one if I remembered doing it on the install.

Here is the code I use from my IIS server app to access files on my other computer (without having to have the same user and password on both machines involved, copied from somewhere and modified for my use):

using System;
using System.Collections.Generic;
using System.Text;
using System.Runtime.InteropServices;
using System.Security.Principal;
using System.ComponentModel;

/// <summary>
/// Class to impersonate another user. Requires user, pass and domain/computername
/// All code run after impersonationuser has been run will run as this user.
/// Remember to Dispose() afterwards.
/// </summary>
public class ImpersonateUser:IDisposable {

    private WindowsImpersonationContext LastContext = null;
    private IntPtr LastUserHandle = IntPtr.Zero;

    #region User Impersonation api
    [DllImport("advapi32.dll", SetLastError = true)]
    public static extern bool LogonUser(string lpszUsername, string lpszDomain, string lpszPassword, int dwLogonType, int dwLogonProvider, out IntPtr phToken);

    [DllImport("advapi32.dll", SetLastError = true)]
    public static extern bool ImpersonateLoggedOnUser(int Token);

    [DllImport("advapi32.dll", CharSet = CharSet.Auto, SetLastError = true)]
    public static extern bool DuplicateToken(IntPtr token, int impersonationLevel, ref IntPtr duplication);

    [DllImport("kernel32.dll")]
    public static extern Boolean CloseHandle(IntPtr hObject);

    public const int LOGON32_PROVIDER_DEFAULT = 0;
    public const int LOGON32_PROVIDER_WINNT35 = 1;
    public const int LOGON32_LOGON_INTERACTIVE = 2;
    public const int LOGON32_LOGON_NETWORK = 3;
    public const int LOGON32_LOGON_BATCH = 4;
    public const int LOGON32_LOGON_SERVICE = 5;
    public const int LOGON32_LOGON_UNLOCK = 7;
    public const int LOGON32_LOGON_NETWORK_CLEARTEXT = 8;// Win2K or higher
    public const int LOGON32_LOGON_NEW_CREDENTIALS = 9;// Win2K or higher
    #endregion

    public ImpersonateUser(string username, string domainOrComputerName, string password, int nm = LOGON32_LOGON_NETWORK) {

        IntPtr userToken = IntPtr.Zero;
        IntPtr userTokenDuplication = IntPtr.Zero;

        bool loggedOn = false;

        if (domainOrComputerName == null) domainOrComputerName = Environment.UserDomainName;

        if (domainOrComputerName.ToLower() == "nt authority") {
            loggedOn = LogonUser(username, domainOrComputerName, password, LOGON32_LOGON_SERVICE, LOGON32_PROVIDER_DEFAULT, out userToken);
        } else {
            loggedOn = LogonUser(username, domainOrComputerName, password, nm, LOGON32_PROVIDER_DEFAULT, out userToken);
        }

        WindowsImpersonationContext _impersonationContext = null;
        if (loggedOn) {
            try {
                // Create a duplication of the usertoken, this is a solution
                // for the known bug that is published under KB article Q319615.
                if (DuplicateToken(userToken, 2, ref userTokenDuplication)) {
                    // Create windows identity from the token and impersonate the user.
                    WindowsIdentity identity = new WindowsIdentity(userTokenDuplication);
                    _impersonationContext = identity.Impersonate();
                } else {
                    // Token duplication failed!
                    // Use the default ctor overload
                    // that will use Mashal.GetLastWin32Error();
                    // to create the exceptions details.
                    throw new Win32Exception();
                }
            } finally {
                // Close usertoken handle duplication when created.
                if (!userTokenDuplication.Equals(IntPtr.Zero)) {
                    // Closes the handle of the user.
                    CloseHandle(userTokenDuplication);
                    userTokenDuplication = IntPtr.Zero;
                }

                // Close usertoken handle when created.
                if (!userToken.Equals(IntPtr.Zero)) {
                    // Closes the handle of the user.
                    CloseHandle(userToken);
                    userToken = IntPtr.Zero;
                }
            }
        } else {
            // Logon failed!
            // Use the default ctor overload that 
            // will use Mashal.GetLastWin32Error();
            // to create the exceptions details.
            throw new Win32Exception();
        }

        if (LastContext == null) LastContext = _impersonationContext;
    }

    public void Dispose() {
        LastContext.Undo();
        LastContext.Dispose();
    }
}

The specific code I found out worked after a bit of trying was this:

using (var impersonation = new ImpersonateUser("OtherMachineUser", "OtherMachineName", "Password", LOGON32_LOGON_NEW_CREDENTIALS))
    {
        var files = System.IO.Directory.GetFiles("\\OtherMachineName\fileshare");
    }