Copying a file to a network share which I don't have access to

Question

This is an extension of this question

I am trying to copy a file from my local user's temp folder to a remote file share. I do not have access to the remote file share, so I have to impersonate a user who does.

Now, I can successfully read a file from the remote server and copy it locally, however I cannot write a local file to the share, since it gives me the error:

Access denied for the LOCAL file

(as I am now impersonating another user).

If you need some code I can post it.

Answer 1

Managed to find the answer,

I simply had to create a FileStream to the local file BEFORE impersonating the remote user, and then pass that FileStream to the copy function.

EDIT: So here is my entire file copying routines

using System.Security.Principal;
using System.Security.Permissions;
using System.Windows.Forms;
using System.Runtime.InteropServices;
using System.Diagnostics;
using System.IO;

public class ImpersonatedFileCopy : IDisposable
{
    #region Assembly Functions
    [DllImport("advapi32.dll")]
    public static extern bool LogonUser(string lpszUsername, string lpszDomain, string lpszPassword, int dwLogonType, int dwLogonProvider, ref IntPtr phToken);

    [DllImport("kernel32.dll")]
    public static extern bool CloseHandle(IntPtr handle);
    #endregion

    #region Private Variables
    private IntPtr _TokenHandle = new IntPtr(0);
    private WindowsImpersonationContext _WindowsImpersonationContext;
    #endregion

    #region Constructors
    public ImpersonatedFileCopy(string domain, string username, string password)
    {
        Impersonate(domain, username, password);
    }
    #endregion

    #region Methods
    [PermissionSet(SecurityAction.Demand, Name = "FullTrust")]
    private void Impersonate(string domain, string username, string password)
    {
        bool returnValue;

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

            _TokenHandle = IntPtr.Zero;

            //Call LogonUser to obtain a handle to an access token.
            returnValue = LogonUser(username, domain, password, LOGON32_LOGON_INTERACTIVE, LOGON32_PROVIDER_DEFAULT, ref _TokenHandle);
            if (returnValue)
            {
                WindowsIdentity newId = new WindowsIdentity(_TokenHandle);
                _WindowsImpersonationContext = newId.Impersonate();
            }
        }
        catch (Exception ex)
        {
            UndoImpersonate();
            Debug.Writeline("Error"+ex.Message);
        }
    }

    private void UndoImpersonate()
    {
        if (_WindowsImpersonationContext != null)
        {
            _WindowsImpersonationContext.Undo();
            if (!_TokenHandle.Equals(IntPtr.Zero))
            {
                CloseHandle(_TokenHandle);
            }
        }
    }

    public bool PutFile(FileStream source, string destRemoteFilename, bool overwrite)
    {
        try
        {
            if (!Directory.Exists(Path.GetDirectoryName(destRemoteFilename))) Directory.CreateDirectory(Path.GetDirectoryName(destRemoteFilename));
            using (FileStream dest = File.OpenWrite(destRemoteFilename))
            {
               source.Seek(0, SeekOrigin.Begin);
               source.CopyTo(dest);
            }
            return true;
        }
        catch
        {
            return false;
        }
    }

    public bool GetFile(string sourceRemoteFilename, FileStream dest, bool overwrite)
    {
        try
        {
            using (FileStream source = File.OpenRead(sourceRemoteFilename))
            {
                source.Seek(0, SeekOrigin.Begin);
                source.CopyTo(dest);
            }
            return true;
        }
        catch
        {
            return false;
        }
    }
    #endregion

    #region IDisposable
    public void Dispose()
    {
        UndoImpersonate();
        GC.SuppressFinalize(this);
    }
    #endregion
}

And the usage:

using (FileStream dest = File.OpenWrite(localDestinationFilename))
using (copy = new ImpersonatedFileCopy(domain,user,pass))
{
   success = copy.GetFile(remoteSourceFilename, dest, true);
}