Windows Access Control List (ACL) Example 35

 

 

 

 

 

Retrieving current user and domain names on Windows NT, Windows 2000, or Windows XP Code Example

 

A program may sometimes need to display the user name and domain name for the current thread. Prior to Windows NT, it could be assumed that a thread was running under the account of the interactively logged on user. Windows NT, however, allows threads to run under multiple security contexts, potentially representing multiple users. For instance, in a client/server application, a thread in the server might impersonate a client through the ImpersonateNamedPipeClient() function. In this case, it runs under the user context of the client. Another example of a thread running in a different security context is a service thread, which has a domain name of NT AUTHORITY and a user name of SYSTEM, assuming that the service is running in the local system account.
If you need to obtain both the user name and the domain name for the current thread, you must first extract the user's security identifier (SID) from the thread's access token by using the GetTokenInformation() function. Then, a call to the LookupAccountSid() function can be used to retrieve the account name and domain name associated with the SID. The sample code at the end of this article demonstrates this technique. The 32-bit functions just mentioned are not available on Microsoft Windows 95 or Microsoft Windows 98. To retrieve the name and domain of the interactive user on Windows 95 or Windows 98, you must call a 16-bit LAN Manager function. The following program example demonstrates how to programmatically retrieve the user name and domain name on Windows NT by using security functions within the Win32 Application Programming Interface (API).

Create a new empty Win32 console application project. Give a suitable project name and change the project location if needed.

 

Retrieving current user and domain names on Windows NT, Windows 2000, or Windows XP Code Example: Creating new C++ empty console mode application using Visual C++

 

Then, add the source file and give it a suitable name.

 

Retrieving current user and domain names on Windows NT, Windows 2000, or Windows XP Code Example: Adding the C++ source file

 

Next, add the following source code.

 

#include <windows.h>

#include <stdio.h>

 

//**********************************************************************

//  FUNCTION:     GetCurrentUserAndDomain - This function looks up

//                the user name and domain name for the user account

//                associated with the calling thread.

//  PARAMETERS:   szUser - a buffer that receives the user name

//                pcchUser - the size, in characters, of szUser

//                szDomain - a buffer that receives the domain name

//                pcchDomain - the size, in characters, of szDomain

//  RETURN VALUE: TRUE if the function succeeds. Otherwise, FALSE and

//                GetLastError() will return the failure reason.

//

//                If either of the supplied buffers are too small,

//                GetLastError() will return ERROR_INSUFFICIENT_BUFFER

//                and pcchUser and pcchDomain will be adjusted to

//                reflect the required buffer sizes.

//**********************************************************************

#define MAX_NAME 256

 

int wmain(int argc, WCHAR **argv)

{

      WCHAR szUser[MAX_NAME];

      WCHAR szDomain[MAX_NAME];

      BOOL         fSuccess = FALSE;

      HANDLE       hToken   = NULL;

      PTOKEN_USER  ptiUser  = NULL;

      DWORD        cbti     = 0;

      SID_NAME_USE snu;

     

      __try {

            // Get the calling thread's access token.

            if (!OpenThreadToken(GetCurrentThread(), TOKEN_QUERY, TRUE, &hToken))

            {

                  if (GetLastError() != ERROR_NO_TOKEN)

                  {

                        wprintf(L"No thread token available!\n");

                        __leave;

                  }

 

                  // Retry against process token if no thread token exists.

                  if (!OpenProcessToken(GetCurrentProcess(), TOKEN_QUERY, &hToken))

                  {

                        wprintf(L"No process token available! error %u\n", GetLastError());

                        __leave;

                  }

                  else

                        wprintf(L"Process token available! Overiding the thread token if available!\n");

            }

            else

                  wprintf(L"Thread token available!\n");

 

           

            // Obtain the size of the user information in the token.

            if (GetTokenInformation(hToken, TokenUser, NULL, 0, &cbti))

            {

                  // Call should have failed due to zero-length buffer.

                  wprintf(L"Getting the size of the user info in the token!\n");

                  __leave;

            }

            else

            {

                  // Call should have failed due to zero-length buffer.

                  if (GetLastError() != ERROR_INSUFFICIENT_BUFFER)

                  {

                        wprintf(L"Insufficient buffer! Re-allocating...\n");

                        __leave;

                  }

            }

           

            // Allocate buffer for user information in the token.

            ptiUser = (PTOKEN_USER) HeapAlloc(GetProcessHeap(), 0, cbti);

            if (!ptiUser)

            {

                  wprintf(L"Heap allocation for ptiUser failed, error %u\n", GetLastError());

                  __leave;

            }

            else

                  wprintf(L"Heap allocated for ptiUser!\n");

           

            // Retrieve the user information from the token.

            if (!GetTokenInformation(hToken, TokenUser, ptiUser, cbti, &cbti))

            {

                  wprintf(L"GetTokenInformation() failed, error %u\n", GetLastError());

                  __leave;

            }

            else

                  wprintf(L"Retrieving the user info from the token!\n");

           

            // Retrieve user name and domain name based on user's SID.

            // The 1st NULL means search the local pc and then domain controller...

            if (!LookupAccountSid(NULL, ptiUser->User.Sid, szUser, &cbti, szDomain, &cbti, &snu))

            {

                  wprintf(L"LookupAccountSid() failed, error %u\n", GetLastError());

                  __leave;

            }

            else

            {

                  wprintf(L"LookupAccountSid() is OK\n");

                  wprintf(L"Current user: %s\n", szUser);

                  wprintf(L"Current domain name (or local pc): %s\n", szDomain);

            }

            // All should be OK

            fSuccess = TRUE;

      }

      __finally

      {

            // Free resources.

            wprintf(L"Freeing up all the allocated resources and handle!\n");

            if (hToken)

                  CloseHandle(hToken);

            if (ptiUser)

                  HeapFree(GetProcessHeap(), 0, ptiUser);

      }

 

   return fSuccess;

}

 

Build and run the project. The following screenshot is a sample output.

 

Retrieving current user and domain names on Windows NT, Windows 2000, or Windows XP Code Example: Showing a sample console outputof the current user of the system

 

 

 

 

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