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determining user access rights on Windows PC before auto-installing DLL

Posted on 2007-10-04
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Last Modified: 2013-12-04
Can anyone suggest away of determining whether a user has admin rights to be able to install (in Program Files) on their PC?

I'm trying to find an elegant way to provide a link via a web page that will auto-install a DLL on any Windows PC - but won't attempt an install if the user doesn't have admin rights, instead displays a message back to the browser.

KC.
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Question by:TangoGirl
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jkr earned 1500 total points
ID: 20015359
That would be

/*------------------------------------------------------------------
| Name: RunningAsAdministrator
| Desc: checks if user has administrator privileges
| Notes: This function returns TRUE if the user identifier associated with
|   this process is a member of the the Administrators group.
------------------------------------------------------------------*/
BOOL RunningAsAdministrator ( VOID)
{
 BOOL   fAdmin;
 HANDLE  hThread;
 TOKEN_GROUPS *ptg = NULL;
 DWORD  cbTokenGroups;
 DWORD  dwGroup;
 PSID   psidAdmin;

 SID_IDENTIFIER_AUTHORITY SystemSidAuthority= SECURITY_NT_AUTHORITY;

 // First we must open a handle to the access token for this thread.

 if ( !OpenThreadToken ( GetCurrentThread(), TOKEN_QUERY, FALSE, &hThread))
 {
  if ( GetLastError() == ERROR_NO_TOKEN)
  {
   // If the thread does not have an access token, we'll examine the
   // access token associated with the process.

   if (! OpenProcessToken ( GetCurrentProcess(), TOKEN_QUERY,
                 &hThread))
   return ( FALSE);
  }
  else
   return ( FALSE);
 }

 // Then we must query the size of the group information associated with
 // the token. Note that we expect a FALSE result from GetTokenInformation
 // because we've given it a NULL buffer. On exit cbTokenGroups will tell
 // the size of the group information.

 if ( GetTokenInformation ( hThread, TokenGroups, NULL, 0, &cbTokenGroups))
  return ( FALSE);

 // Here we verify that GetTokenInformation failed for lack of a large
 // enough buffer.

 if ( GetLastError() != ERROR_INSUFFICIENT_BUFFER)
  return ( FALSE);

 // Now we allocate a buffer for the group information.
 // Since _alloca allocates on the stack, we don't have
 // to explicitly deallocate it. That happens automatically
 // when we exit this function.

 if ( ! ( ptg= _alloca ( cbTokenGroups)))
  return ( FALSE);

 // Now we ask for the group information again.
 // This may fail if an administrator has added this account
 // to an additional group between our first call to
 // GetTokenInformation and this one.

 if ( !GetTokenInformation ( hThread, TokenGroups, ptg, cbTokenGroups,
          &cbTokenGroups) )
  return ( FALSE);

 // Now we must create a System Identifier for the Admin group.

 if ( ! AllocateAndInitializeSid ( &SystemSidAuthority, 2,
            SECURITY_BUILTIN_DOMAIN_RID,
            DOMAIN_ALIAS_RID_ADMINS,
            0, 0, 0, 0, 0, 0, &psidAdmin) )
  return ( FALSE);

 // Finally we'll iterate through the list of groups for this access
 // token looking for a match against the SID we created above.

 fAdmin= FALSE;

 for ( dwGroup= 0; dwGroup < ptg->GroupCount; dwGroup++)
 {
  if ( EqualSid ( ptg->Groups[dwGroup].Sid, psidAdmin))
  {
   fAdmin = TRUE;

   break;
  }
 }

 // Before we exit we must explicity deallocate the SID we created.

 FreeSid ( psidAdmin);

 return ( fAdmin);
}

See also http://msdn2.microsoft.com/en-us/library/ms995339.aspx ("Windows NT Security")
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Expert Comment

by:jkr
ID: 20155941
I'd say this question is answered, thus I object.
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