LogonUser returns 0 and GetLastError also returns 0

Question

I'm attempting to logon to a computer remotely so that I can copy a local directory locally. I'm attempting to use the LogonUser function call found in the advapi32 DLL. When I call the function, it returns 0 (false) but when I call Marshal.GetLastWin32Error() that also returns 0, indicating that there was no error. The username and password I'm trying to use I know works because I use it to log on to the computer. I've used both domain and local accounts and both return the same result. Below is my attempt to logon to the computer.

[DllImport("advapi32.DLL", SetLastError = true)]
public static extern bool LogonUser(string lpszUsername, string lpszDomain, string lpszPassword, int dwLongonType, int dwLogonProvider, ref IntPtr phToken);

[DllImport("kernel32.Dll", CharSet = CharSet.Auto)]
public extern static bool CloseHandle(IntPtr handle);

[DllImport("kernel32.DLL", CharSet = CharSet.Auto)]
public static extern string GetLastError();

private static void CopyDirectory(string computerName, string localPath, string remotePath)
{
    WindowsImpersonationContext impersonationContext = null;
    IntPtr userHandle = IntPtr.Zero;
    string username = @"testing";
    string password = @"testing";

    string fullRemotePath = string.Format("{0}\\{1}", computerName, remotePath);

    try
    {

        bool Logon = LogonUser(username, computerName, password, 2, 0, ref userHandle);
        if (!Logon)
        {
            Console.WriteLine("Error Logging in");
            int errorCode = Marshal.GetLastWin32Error();
            Console.WriteLine(string.Format("Error Code: {0}", errorCode));
            Console.WriteLine(new Win32Exception(errorCode).Message);
        }

        else
        {
            WindowsIdentity user = new WindowsIdentity(userHandle);
            impersonationContext = user.Impersonate();

            System.IO.File.Copy(localPath, fullRemotePath, true);
        }

    }

    catch (Exception ex)
    {
        int errorCode = Marshal.GetLastWin32Error();
        Console.WriteLine(string.Format("Error Code: {0}", errorCode));
        Console.WriteLine(ex.Message);
    }

    finally
    {
        if(impersonationContext != null)
            impersonationContext.Undo();

        if(userHandle != IntPtr.Zero)
            CloseHandle(userHandle);

    }
}

Could you please assist me in finding my flaw?

EDIT: I found the following comment here

Even if an API supports SetLastError/GetLastError, the value returned by GetLastError is only meaningful if the API you just called actually fails. How that failure is indicated depends on the API. Except for a couple of braindead API/situation combinations, like Impersonate* with the new SeImpersonatePrivilege: the API can return a success code even if it fails due to lack of privilege, leaving you with only an identification token. Then you have to call GetLastError () to find out why the nominally-successful API call failed....

I have a feeling this is what is causing me problems. How do I get around this?

There is no flaw visible, code works fine. Surely you never use the completely wrong declaration for GetLastError(), it returns *int*. — Hans Passant, Apr 09 '15 at 17:57
if i change LogonUser to return an int instead of a bool it still returns 0 (false) — xtreampb, Apr 09 '15 at 17:59
also the userHandle reference is 0 which will not work when trying to create the WindowsIdentity — xtreampb, Apr 09 '15 at 18:08

score 0 · Accepted Answer · edited May 23 '17 at 11:51

0

So i was over analyzing my problem and solution. Apparently i may not need to use UserLogon as This answer works in my test environment. Lets see if this works when I use it.

Edit: Results This all worked for me just had to create a user on my server with same credentials (username/password) and could see the other computers on the workgroup

edited May 23 '17 at 11:51

Community

1
1

answered Apr 09 '15 at 18:45

xtreampb

528
6
19

score 0 · Answer 2 · answered Apr 10 '18 at 15:26

0

I ended up solving this problem by using windows login credentials. so if "username/password" is your windows login then just use the same "username/password" in the "LogonUser" method. Hope it helps.

answered Apr 10 '18 at 15:26

L.L.

679
8
14

LogonUser returns 0 and GetLastError also returns 0

2 Answers2