Grabbing data from the registry on a remote machine using dot net and WMI


I recently had to write an app which, given a computer name, would grab their telephone extension from a registry key (For the purpose of the code example below, I just grab the CommonFilesDir key from the windows node. There’s a couple of ways you can achieve this- either using RegistryKey.OpenRemoteBaseKey which gave me a whole bunch of permissions issues, plus you need the remote registry and remote administration services active on the server/client OR you can use the Windows Management Instrumentation (WMI) service. I took this route, as it’s a service which is active by default on all of our machines on the domain, and it was easier to get the permissions right.

Before I paste the code, a GOTCHA to beware of, straight from the MSDN here;

The registry provider is hosted in LocalService—not the LocalSystem. Therefore, obtaining information remotely from the subtree HKEY_CURRENT_USER is not possible

ConnectionOptions options = new ConnectionOptions();
options.Impersonation = ImpersonationLevel.Impersonate;
options.EnablePrivileges = true;
options.Username = "<domain_admin_username>";
options.Password = "<domain_admin_password>";

// http://msdn.microsoft.com/en-us/library/system.management.managementscope.aspx
ManagementScope ms = new ManagementScope("\\\\<computer name>\\root\\default", options);          
   
ms.Connect();

// http://msdn.microsoft.com/en-us/library/windows/desktop/aa390788(v=vs.85).aspx
ManagementClass mc = new ManagementClass("stdRegProv");
mc.Scope = ms;

ManagementBaseObject inParams = mc.GetMethodParameters("GetStringValue"); 
// there are other methods for grabbing other reg types- see 
// http://msdn.microsoft.com/en-us/library/windows/desktop/aa393664(v=VS.85).aspx

inParams["hDefKey"] = RegHive.HKEY_LOCAL_MACHINE;
inParams["sSubKeyName"] = "SOFTWARE\\Microsoft\\Windows\\CurrentVersion";
inParams["sValueName"] = "CommonFilesDir";

ManagementBaseObject outParams =
        mc.InvokeMethod("GetStringValue", inParams, null);

if (outParams["ReturnValue"].ToString() == "0")
{
    Console.WriteLine(outParams["sValue"]);
}
else
{
    Console.WriteLine("Error " + outParams["ReturnValue"] + " please refer to http://msdn.microsoft.com/en-us/library/ms681382%28v=3Dvs.85%29.aspx");
}

Console.ReadLine();

This code requires this enum..

public enum RegHive : uint
{
  HKEY_CLASSES_ROOT = 0x80000000,
  HKEY_CURRENT_USER = 0x80000001,
  HKEY_LOCAL_MACHINE = 0x80000002,
  HKEY_USERS = 0x80000003,
  HKEY_CURRENT_CONFIG = 0x80000005
}

If you receive a COM error back “The RPC server is unavailable”, make sure the target machine’s firewall isn’t blocking the call- this will open the port;
netsh firewall set service RemoteAdmin

  1. No comments yet.
(will not be published)