Open a shared file under another user and domain?

Question

I have a C# console application that needs to read a shared file on a machine in another domain. When the application tries to access the file an exception occurs as the local user does not have permission to access the shared resource.

Currently I overcome this problem manually by open the shared folder from the run and put the username and password into the windows authentication dialog then run the application.

How can I do it programmatically?

Answer 1

From memory you'll need to use a Windows API call and login as a user on the other domain. See this link for an example.

Another idea could be to use the RunAs command line argument to read the file and save it into a file on your local domain/server.

Answer 2

a) p/invoke LogonUser with LOGON32_LOGON_NEW_CREDENTIALS and create a new WindowsIdentity with the new token, then use normal file access.

b) p/invoke WNetAddConnection3. Be advised that this makes your remote share accessible to every other process on your machine.

c) WMI via System.Management and CIM_DataFile; you won't even need p/invoke. System.Management lets you specify credentials for remote machine.

Answer 3

I used the point "a" as "Anton" suggested, I developed two versions for one class, first one using Win32 APIs and second uses WindowsIdentity class

Version 1:

class UserImpersonation:IDisposable
    {       
        [DllImport("advapi32.dll")]
            public static extern int LogonUser(String lpszUserName,
                String lpszDomain,
                String lpszPassword,
                int dwLogonType,
                int dwLogonProvider,
                ref IntPtr phToken);

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

            [DllImport("advapi32.dll", CharSet = CharSet.Auto, SetLastError = true)]
            public static extern bool RevertToSelf();

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

            const int LOGON32_PROVIDER_DEFAULT = 0;
            const int LOGON32_LOGON_INTERACTIVE = 2;

            WindowsImpersonationContext wic;
            string _userName;
            string _domain;
            string _passWord;
            public UserImpersonation(string userName, string domain, string passWord)
            {
                _userName = userName;
                _domain = domain;
                _passWord = passWord;
            }
            public bool ImpersonateValidUser()
            {
                WindowsIdentity wi;
                IntPtr token = IntPtr.Zero;
                IntPtr tokenDuplicate = IntPtr.Zero;

                if (RevertToSelf())
                {
                    if (LogonUser(_userName, _domain, _passWord, LOGON32_LOGON_INTERACTIVE,
                        LOGON32_PROVIDER_DEFAULT, ref token) != 0)
                    {
                        if (DuplicateToken(token, 2, ref tokenDuplicate) != 0)
                        {
                            wi = new WindowsIdentity(tokenDuplicate);
                            wic = wi.Impersonate();
                            if (wic != null)
                            {
                                CloseHandle(token);
                                CloseHandle(tokenDuplicate);
                                return true;
                            }
                        }
                    }
                }
                if (token != IntPtr.Zero)
                    CloseHandle(token);
                if (tokenDuplicate != IntPtr.Zero)
                    CloseHandle(tokenDuplicate);
                return false;
            }

        #region IDisposable Members
            public void Dispose()
            {
                if(wic != null)
                 wic.Dispose();
                RevertToSelf();

            }
            #endregion
    }

Version2 (from MSDN with small changes)

class UserImpersonation2:IDisposable
    {
        [DllImport("advapi32.dll")]
        public static extern bool LogonUser(String lpszUserName,
            String lpszDomain,
            String lpszPassword,
            int dwLogonType,
            int dwLogonProvider,
            ref IntPtr phToken);

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

        WindowsImpersonationContext wic;
        IntPtr tokenHandle;
        string _userName;
        string _domain;
        string _passWord;

        public UserImpersonation2(string userName, string domain, string passWord)
        {
            _userName = userName;
            _domain = domain;
            _passWord = passWord;
        }

        const int LOGON32_PROVIDER_DEFAULT = 0;
        const int LOGON32_LOGON_INTERACTIVE = 2;

        public bool ImpersonateValidUser()
        {
            bool returnValue = LogonUser(_userName, _domain, _passWord,
                    LOGON32_LOGON_INTERACTIVE, LOGON32_PROVIDER_DEFAULT,
                    ref tokenHandle);

            Console.WriteLine("LogonUser called.");

            if (false == returnValue)
            {
                int ret = Marshal.GetLastWin32Error();
                Console.WriteLine("LogonUser failed with error code : {0}", ret);
                return false;
            }

            Console.WriteLine("Did LogonUser Succeed? " + (returnValue ? "Yes" : "No"));
            Console.WriteLine("Value of Windows NT token: " + tokenHandle);

            // Check the identity.
            Console.WriteLine("Before impersonation: "
                + WindowsIdentity.GetCurrent().Name);
            // Use the token handle returned by LogonUser.
            WindowsIdentity newId = new WindowsIdentity(tokenHandle);
            wic = newId.Impersonate();

            // Check the identity.
            Console.WriteLine("After impersonation: "
                + WindowsIdentity.GetCurrent().Name);
            return true;
        }
        #region IDisposable Members
        public void Dispose()
        {
            if(wic!=null)
                wic.Undo();
            if (tokenHandle != IntPtr.Zero)
                CloseHandle(tokenHandle);

        }
        #endregion
    }

How to use (both are the same)

            const string file = @"\\machine\test\file.txt";

            using (UserImpersonation user = new UserImpersonation("user", "domain", "password"))
            {
                if (user.ImpersonateValidUser())
                {
                    StreamReader reader = new StreamReader(file);
                    Console.WriteLine(reader.ReadToEnd());
                    reader.Close();
                }
            }

Answer 4

Does this hack also work for windows background services?