Access a server file using impersonation

see http://support.microsoft.com/?scid=306158

please leave it active, I am still working on the project. thank you.

It's not working and not giving me an error message or any indication of why...

it throws me to the "catch" at this line: impersonationContext =
                              ((System.Security.Principal.WindowsIdentity)User.Identity).Impersonate();

Can you show me how you are using this code?

Bob

I'll post the section of code I"m useing on Monday, as it is on my work computer. Thanks!

using System.Security.Principal;

...code...


                        System.Security.Principal.WindowsImpersonationContext impersonationContext;
                        impersonationContext =
                              ((System.Security.Principal.WindowsIdentity)User.Identity).Impersonate();
                  if (servPath.Equals("Null"))
                  {
                        this.hypServPDF.Enabled = false;
                        this.hypServPDF.Text = "not available";
                  }
                  else
                  {


                        this.hypServPDF.Enabled = true;
                        this.hypServPDF.Text = "Download";
                        this.hypServPDF.NavigateUrl = servPath.ToString();
                        this.hypServPDF.Target = "bill";



                  }
                        impersonationContext.Undo();
                  

Here is a class converted from VB.NET (untested):

using System;
using System.Runtime.InteropServices;
using System.Security.Principal;
using System.Security.Permissions;

public class WindowsImpersonator
{

  [DllImport("advapi32.dll", CharSet=CharSet.Auto)]
  private static extern bool LogonUser(string lpszUsername, string lpszDomain, string lpszPassword, int dwLogonType, int dwLogonProvider, ref IntPtr phToken);

  [DllImport("kernel32.dll")]
  private static extern int FormatMessage(int dwFlags, ref IntPtr lpSource, int dwMessageId, int dwLanguageId, ref string lpBuffer, int nSize, ref IntPtr Arguments);

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

  [DllImport("advapi32.dll", CharSet=CharSet.Auto)]
  private static extern bool DuplicateToken(IntPtr ExistingTokenHandle, int SECURITY_IMPERSONATION_LEVEL, ref IntPtr DuplicateTokenHandle);

  private WindowsImpersonationContext m_impersonatedUser;

  private static string GetErrorMessage(int errorCode)
  {
    int FORMAT_MESSAGE_ALLOCATE_BUFFER = 256;
    int FORMAT_MESSAGE_IGNORE_INSERTS = 512;
    int FORMAT_MESSAGE_FROM_SYSTEM = 4096;

    int messageSize = 255;
    string lpMsgBuf = "";
    int dwFlags = FORMAT_MESSAGE_ALLOCATE_BUFFER | FORMAT_MESSAGE_FROM_SYSTEM | FORMAT_MESSAGE_IGNORE_INSERTS;

    IntPtr ptrlpSource = IntPtr.Zero;
    IntPtr prtArguments = IntPtr.Zero;

    int retVal = FormatMessage(dwFlags, ref ptrlpSource, errorCode, 0, ref lpMsgBuf, messageSize, ref prtArguments);
    if (0 == retVal)
    {
      throw new Exception("Failed to format message for error code " + errorCode.ToString() + ". ");
    }
    return lpMsgBuf;
  }

  public void Impersonate(string domainName, string userName, string password)
  {
    const int LOGON32_PROVIDER_DEFAULT = 0;
    const int LOGON32_LOGON_INTERACTIVE = 2;
    const int SecurityImpersonation = 2;
    IntPtr tokenHandle = IntPtr.Zero;
    IntPtr dupeTokenHandle = IntPtr.Zero;
    try
    {
      bool returnValue = LogonUser(userName, domainName, password, LOGON32_LOGON_INTERACTIVE, LOGON32_PROVIDER_DEFAULT, ref tokenHandle);
      if (!returnValue)
      {
        int ret = Marshal.GetLastWin32Error();
        throw new Exception(string.Format("Error: [{0}] {1}", ret, GetErrorMessage(ret)));
      }
      bool retVal = DuplicateToken(tokenHandle, SecurityImpersonation, ref dupeTokenHandle);
      if (!retVal)
      {
        CloseHandle(tokenHandle);
        throw new Exception("Exception thrown in trying to duplicate token.");
      }
      WindowsIdentity newId = new WindowsIdentity(dupeTokenHandle);
      m_impersonatedUser = newId.Impersonate();
      if (tokenHandle != IntPtr.Zero)
      {
        CloseHandle(tokenHandle);
      }
      if (dupeTokenHandle != IntPtr.Zero)
      {
        CloseHandle(dupeTokenHandle);
      }
    }
    catch (Exception ex)
    {
      Console.WriteLine(("Exception occurred. " + ex.Message));
    }
  }

  public void Undo()
  {
    m_impersonatedUser.Undo();
  }

  public string CurrentName
  {
    get { return WindowsIdentity.GetCurrent().Name; }
  }

}

Bob

That is about 10 miles over my head. where do I put that, and where do I put the file path it is suppoed to be accessing?

ok, I'll give it a go...

I'm off of work until Monday, but I will try it and repond then.