How to provide user name and password when connect

Question

When connecting to a network share for which the current user (in my case, a network enabled service user) has no rights, name and password have to be provided.

I know how to do this with Win32 functions (the WNet* family from mpr.dll), but would like to do it with .Net (2.0) functionality.

What options are available?

Maybe some more information helps:

• The use case is a windows service, not an Asp.Net application.
• The service is running under an account which has no rights on the share.
• The user account needed for the share is not known on the client side.
• Client and server are not members of the same domain.

Answer 1

Today 7 years later I'm facing the same issue and I'd like to share my version of the solution.

It is copy & paste ready :-) Here it is:

Step 1

In your code (whenever you need to do something with permissions)

ImpersonationHelper.Impersonate(domain, userName, userPassword, delegate
                            {
                                //Your code here 
                                //Let's say file copy:
                                if (!File.Exists(to))
                                {
                                    File.Copy(from, to);
                                }
                            });

Step 2

The Helper file which does a magic

using System;
using System.Runtime.ConstrainedExecution;
using System.Runtime.InteropServices;
using System.Security;
using System.Security.Permissions;
using System.Security.Principal;    
using Microsoft.Win32.SafeHandles;


namespace BlaBla
{
    public sealed class SafeTokenHandle : SafeHandleZeroOrMinusOneIsInvalid
    {
        private SafeTokenHandle()
            : base(true)
        {
        }

        [DllImport("kernel32.dll")]
        [ReliabilityContract(Consistency.WillNotCorruptState, Cer.Success)]
        [SuppressUnmanagedCodeSecurity]
        [return: MarshalAs(UnmanagedType.Bool)]
        private static extern bool CloseHandle(IntPtr handle);

        protected override bool ReleaseHandle()
        {
            return CloseHandle(handle);
        }
    }

    public class ImpersonationHelper
    {
        [DllImport("advapi32.dll", SetLastError = true, CharSet = CharSet.Unicode)]
        private static extern bool LogonUser(String lpszUsername, String lpszDomain, String lpszPassword,
        int dwLogonType, int dwLogonProvider, out SafeTokenHandle phToken);

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

        [PermissionSet(SecurityAction.Demand, Name = "FullTrust")]
        public static void Impersonate(string domainName, string userName, string userPassword, Action actionToExecute)
        {
            SafeTokenHandle safeTokenHandle;
            try
            {

                const int LOGON32_PROVIDER_DEFAULT = 0;
                //This parameter causes LogonUser to create a primary token.
                const int LOGON32_LOGON_INTERACTIVE = 2;

                // Call LogonUser to obtain a handle to an access token.
                bool returnValue = LogonUser(userName, domainName, userPassword,
                    LOGON32_LOGON_INTERACTIVE, LOGON32_PROVIDER_DEFAULT,
                    out safeTokenHandle);
                //Facade.Instance.Trace("LogonUser called.");

                if (returnValue == false)
                {
                    int ret = Marshal.GetLastWin32Error();
                    //Facade.Instance.Trace($"LogonUser failed with error code : {ret}");

                    throw new System.ComponentModel.Win32Exception(ret);
                }

                using (safeTokenHandle)
                {
                    //Facade.Instance.Trace($"Value of Windows NT token: {safeTokenHandle}");
                    //Facade.Instance.Trace($"Before impersonation: {WindowsIdentity.GetCurrent().Name}");

                    // Use the token handle returned by LogonUser.
                    using (WindowsIdentity newId = new WindowsIdentity(safeTokenHandle.DangerousGetHandle()))
                    {
                        using (WindowsImpersonationContext impersonatedUser = newId.Impersonate())
                        {
                            //Facade.Instance.Trace($"After impersonation: {WindowsIdentity.GetCurrent().Name}");
                            //Facade.Instance.Trace("Start executing an action");

                            actionToExecute();

                            //Facade.Instance.Trace("Finished executing an action");
                        }
                    }
                    //Facade.Instance.Trace($"After closing the context: {WindowsIdentity.GetCurrent().Name}");
                }

            }
            catch (Exception ex)
            {
                //Facade.Instance.Trace("Oh no! Impersonate method failed.");
                //ex.HandleException();
                //On purpose: we want to notify a caller about the issue /Pavel Kovalev 9/16/2016 2:15:23 PM)/
                throw;
            }
        }
    }
}

Answer 2

One option that might work is using WindowsIdentity.Impersonate (and change the thread principal) to become the desired user, like so. Back to p/invoke, though, I'm afraid...

Another cheeky (and equally far from ideal) option might be to spawn a process to do the work... ProcessStartInfo accepts a .UserName, .Password and .Domain.

Finally - perhaps run the service in a dedicated account that has access? (removed as you have clarified that this isn't an option).

Answer 3

For VB.lovers the VB.NET equivalent of Luke Quinane's code (thanks Luke!)

Imports System
Imports System.Net
Imports System.Runtime.InteropServices
Imports System.ComponentModel

Public Class NetworkConnection
    Implements IDisposable

    Private _networkName As String

    Public Sub New(networkName As String, credentials As NetworkCredential)
        _networkName = networkName

        Dim netResource = New NetResource() With {
             .Scope = ResourceScope.GlobalNetwork,
             .ResourceType = ResourceType.Disk,
             .DisplayType = ResourceDisplaytype.Share,
             .RemoteName = networkName
        }

        Dim userName = If(String.IsNullOrEmpty(credentials.Domain), credentials.UserName, String.Format("{0}\{1}", credentials.Domain, credentials.UserName))

        Dim result = WNetAddConnection2(NetResource, credentials.Password, userName, 0)

        If result <> 0 Then
            Throw New Win32Exception(result, "Error connecting to remote share")
        End If
    End Sub

    Protected Overrides Sub Finalize()
        Try
            Dispose (False)
        Finally
            MyBase.Finalize()
        End Try
    End Sub

    Public Sub Dispose() Implements IDisposable.Dispose
        Dispose (True)
        GC.SuppressFinalize (Me)
    End Sub

    Protected Overridable Sub Dispose(disposing As Boolean)
        WNetCancelConnection2(_networkName, 0, True)
    End Sub

    <DllImport("mpr.dll")> _
    Private Shared Function WNetAddConnection2(netResource As NetResource, password As String, username As String, flags As Integer) As Integer
    End Function

    <DllImport("mpr.dll")> _
    Private Shared Function WNetCancelConnection2(name As String, flags As Integer, force As Boolean) As Integer
    End Function

End Class

<StructLayout(LayoutKind.Sequential)> _
Public Class NetResource
    Public Scope As ResourceScope
    Public ResourceType As ResourceType
    Public DisplayType As ResourceDisplaytype
    Public Usage As Integer
    Public LocalName As String
    Public RemoteName As String
    Public Comment As String
    Public Provider As String
End Class

Public Enum ResourceScope As Integer
    Connected = 1
    GlobalNetwork
    Remembered
    Recent
    Context
End Enum

Public Enum ResourceType As Integer
    Any = 0
    Disk = 1
    Print = 2
    Reserved = 8
End Enum

Public Enum ResourceDisplaytype As Integer
    Generic = &H0
    Domain = &H1
    Server = &H2
    Share = &H3
    File = &H4
    Group = &H5
    Network = &H6
    Root = &H7
    Shareadmin = &H8
    Directory = &H9
    Tree = &HA
    Ndscontainer = &HB
End Enum

Answer 4

You can either change the thread identity, or P/Invoke WNetAddConnection2. I prefer the latter, as I sometimes need to maintain multiple credentials for different locations. I wrap it into an IDisposable and call WNetCancelConnection2 to remove the creds afterwards (avoiding the multiple usernames error):

using (new NetworkConnection(@"\\server\read", readCredentials))
using (new NetworkConnection(@"\\server2\write", writeCredentials)) {
   File.Copy(@"\\server\read\file", @"\\server2\write\file");
}

Answer 5

You should be looking at adding a like like this:

<identity impersonate="true" userName="domain\user" password="****" />

Into your web.config.

More Information.