Windows服务与WMI

Question

For one of my customers, I'm writing a Windows Service in C#. It checks a lot of stuff, but 1 thing it has to do, is check if a printerport (ip address) already exists. if yes, connect certain printer to the ip-port. If no, create port and connect after all.

I use WMI to check for existing printer ports and to create them. I also use WMI to connect the printer to the printerport.

On Windows 7, this works like a charm. But on my (virtual) XP machine, the service doesn't seem to have any WMI rights at all. The port check fails and the creating fails. Just a simple 'access denied' from the ManagementException is given.

If I make a little testprogram (console application in C#), it works like a charm as well.

I tried running the service under different accounts (local system, administrator, my personal login with admin rights), nothing seems to work and I'm getting the feeling you cannot use WMI in a Windows Service on Windows XP.

Do you guys have any clue how to fix this? Or what is wrong here ?

Don't know where else to look for answers, so I made an account here, hoping to find the right answer with you.

Answer 1

Are you using Win32_Printer? On the Win32_Printer reference page, it says,

Remarks

The Win32_Printer class is derived from CIM_Printer. Before calling SWbemObject.Put_ or IWbemServices::PutInstance for a Win32_Printer instance, the SeLoadDriverPrivilege privilege (wbemPrivilegeLoadDriver for Visual Basic and LoadDriver for scripting monikers) must be enabled. For more information, see Privilege Constants and Executing Privileged Operations. The following VBScript code example shows how to enable the SeLoadDriverPrivilege privilege in script.

Edit: I know there a difference between Windows Server 2003 and Server 2008 when it comes to services. Under the older operating systems (maybe XP is included), the user's profile is not loaded by default. This has issues when trying to use DPAPI APIs. Perhaps, something similar is occuring in this situation. Only a guess.

Edit: Ensure you are enabling Impersonation when connecting to WMI. There is an example on the Win32_TCPIPPrinterPort page.

ConnectionOptions options = new ConnectionOptions();
options.Impersonation = System.Management.ImpersonationLevel.Impersonate;

ManagementScope scope = new ManagementScope(@"\\root\\cimv2", options);
scope.Connect();
ManagementObjectSearcher searcher = new ManagementObjectSearcher("SELECT * FROM Win32_TCPIPPrinterPort where HostAddress = '" + printerPort + "'"); 

Answer 2

There are two things you could try, first off you can try and set some credentials on your ConnectionOptions

ConnectionOptions options = new ConnectionOptions();
options.Username = userName;
options.Password = password;
options.EnablePrivileges = true;

The other approach could be by wrapping your entire code in some impersonation trickery, but I would definately try looking at the ConnectionOptions first.

If you want to try the impersonation bit I wrote a blogpost about it a while back. http://beddet.wordpress.com/2011/09/25/remote-controlling/