How to Programmatically Set GPO to Not Configured or Disabled

Question

I'm looking for a programmatic solution that has the same effect as setting the "Configure Windows NTP Client" state in GPOE Administrative Templates > System > Windows Time Service > Time Providers > Configure Windows NTP Client to Not Configured or Disabled, but I'll take any help I can get at this point.

Is there a registry key I can modify using the .NET Registry class or a property I can modify using the RSoP WMI classes? I've been looking in both places for days, but haven't found anything that will effectively disable the GPO or have the same effect as disabling or setting it to Not Configured in the GUI.

Answer 1

Firstly you have to find the registry value to edit. They are all listed in the XLS document downloadable at http://www.microsoft.com/en-us/download/details.aspx?id=25250. This document does not indicate the type of the value (REGSZ, DWORD, etc), so you have to set the setting by using the editor and then look the type of the value with regedit.

Now you have the registry key, the value name and its type, let's add some C# and use the COM interface IGroupPolicyObject

[ComImport, Guid("EA502722-A23D-11d1-A7D3-0000F87571E3")]
internal class GPClass
{
}

[ComImport, Guid("EA502723-A23D-11d1-A7D3-0000F87571E3"), InterfaceType(ComInterfaceType.InterfaceIsIUnknown)]
public interface IGroupPolicyObject
{
    uint New([MarshalAs(UnmanagedType.LPWStr)] string domainName, [MarshalAs(UnmanagedType.LPWStr)] string displayName, uint flags);

    uint OpenDSGPO([MarshalAs(UnmanagedType.LPWStr)] string path, uint flags);

    uint OpenLocalMachineGPO(uint flags);

    uint OpenRemoteMachineGPO([MarshalAs(UnmanagedType.LPWStr)] string computerName, uint flags);

    uint Save([MarshalAs(UnmanagedType.Bool)] bool machine, [MarshalAs(UnmanagedType.Bool)] bool add, [MarshalAs(UnmanagedType.LPStruct)] Guid extension, [MarshalAs(UnmanagedType.LPStruct)] Guid app);

    uint Delete();

    uint GetName([MarshalAs(UnmanagedType.LPWStr)] StringBuilder name, int maxLength);

    uint GetDisplayName([MarshalAs(UnmanagedType.LPWStr)] StringBuilder name, int maxLength);

    uint SetDisplayName([MarshalAs(UnmanagedType.LPWStr)] string name);

    uint GetPath([MarshalAs(UnmanagedType.LPWStr)] StringBuilder path, int maxPath);

    uint GetDSPath(uint section, [MarshalAs(UnmanagedType.LPWStr)] StringBuilder path, int maxPath);

    uint GetFileSysPath(uint section, [MarshalAs(UnmanagedType.LPWStr)] StringBuilder path, int maxPath);

    uint GetRegistryKey(uint section, out IntPtr key);

    uint GetOptions(out uint options);

    uint SetOptions(uint options, uint mask);

    uint GetType(out IntPtr gpoType);

    uint GetMachineName([MarshalAs(UnmanagedType.LPWStr)] StringBuilder name, int maxLength);

    uint GetPropertySheetPages(out IntPtr pages);
}


public enum GroupPolicySection
{
    Root = 0,
    User = 1,
    Machine = 2,
}

public abstract class GroupPolicyObject
{
    protected const int MaxLength = 1024;

    /// <summary>
    /// The snap-in that processes .pol files
    /// </summary>
    private static readonly Guid RegistryExtension = new Guid(0x35378EAC, 0x683F, 0x11D2, 0xA8, 0x9A, 0x00, 0xC0, 0x4F, 0xBB, 0xCF, 0xA2);

    /// <summary>
    /// This application
    /// </summary>
    private static readonly Guid LocalGuid = new Guid(GetAssemblyAttribute<GuidAttribute>(Assembly.GetExecutingAssembly()).Value);

    protected IGroupPolicyObject Instance = null;

    static T GetAssemblyAttribute<T>(ICustomAttributeProvider assembly) where T : Attribute
    {
        object[] attributes = assembly.GetCustomAttributes(typeof(T), true);
        if (attributes.Length == 0)
            return null;

        return (T)attributes[0];
    }

    internal GroupPolicyObject()
    {
        Instance = GetInstance();
    }

    public void Save()
    {
        var result = Instance.Save(true, true, RegistryExtension, LocalGuid);
        if (result != 0)
        {
            throw new Exception("Error saving machine settings");
        }

        result = Instance.Save(false, true, RegistryExtension, LocalGuid);
        if (result != 0)
        {
            throw new Exception("Error saving user settings");
        }
    }

    public void Delete()
    {
        var result = Instance.Delete();
        if (result != 0)
        {
            throw new Exception("Error deleting the GPO");
        }
        Instance = null;
    }

    public RegistryKey GetRootRegistryKey(GroupPolicySection section)
    {
        IntPtr key;
        var result = Instance.GetRegistryKey((uint)section, out key);
        if (result != 0)
        {
            throw new Exception(string.Format("Unable to get section '{0}'", Enum.GetName(typeof(GroupPolicySection), section)));
        }

        var handle = new SafeRegistryHandle(key, true);
        return RegistryKey.FromHandle(handle, RegistryView.Default);
    }

    public abstract string GetPathTo(GroupPolicySection section);

    protected static IGroupPolicyObject GetInstance()
    {
        var concrete = new GPClass();
        return (IGroupPolicyObject)concrete;
    }
}

public class GroupPolicyObjectSettings
{
    public readonly bool LoadRegistryInformation;
    public readonly bool Readonly;

    public GroupPolicyObjectSettings(bool loadRegistryInfo = true, bool readOnly = false)
    {
        LoadRegistryInformation = loadRegistryInfo;
        Readonly = readOnly;
    }

    private const uint RegistryFlag = 0x00000001;
    private const uint ReadonlyFlag = 0x00000002;

    internal uint Flag
    {
        get
        {
            uint flag = 0x00000000;
            if (LoadRegistryInformation)
            {
                flag |= RegistryFlag;
            }

            if (Readonly)
            {
                flag |= ReadonlyFlag;
            }

            return flag;
        }
    }
}

public class ComputerGroupPolicyObject : GroupPolicyObject
{
    public readonly bool IsLocal;

    public ComputerGroupPolicyObject(GroupPolicyObjectSettings options = null)
    {
        options = options ?? new GroupPolicyObjectSettings();
        var result = Instance.OpenLocalMachineGPO(options.Flag);
        if (result != 0)
        {
            throw new Exception("Unable to open local machine GPO");
        }
        IsLocal = true;
    }

    public ComputerGroupPolicyObject(string computerName, GroupPolicyObjectSettings options = null)
    {
        options = options ?? new GroupPolicyObjectSettings();
        var result = Instance.OpenRemoteMachineGPO(computerName, options.Flag);
        if (result != 0)
        {
            throw new Exception(string.Format("Unable to open GPO on remote machine '{0}'", computerName));
        }
        IsLocal = false;
    }

    public static void SetPolicySetting(string registryInformation, string settingValue, RegistryValueKind registryValueKind)
    {
        string valueName;
        GroupPolicySection section;
        string key = Key(registryInformation, out valueName, out section);

        // Thread must be STA
        Exception exception = null;
        var t = new Thread(() =>
        {
            try
            {
                var gpo = new ComputerGroupPolicyObject();
                using (RegistryKey rootRegistryKey = gpo.GetRootRegistryKey(section))
                {
                    // Data can't be null so we can use this value to indicate key must be delete
                    if (settingValue == null)
                    {
                        using (RegistryKey subKey = rootRegistryKey.OpenSubKey(key, true))
                        {
                            if (subKey != null)
                            {
                                subKey.DeleteValue(valueName);
                            }
                        }
                    }
                    else
                    {
                        using (RegistryKey subKey = rootRegistryKey.CreateSubKey(key))
                        {
                            subKey.SetValue(valueName, settingValue, registryValueKind);
                        }
                    }
                }

                gpo.Save();
            }
            catch (Exception ex)
            {
                exception = ex;
            }
        });
        t.SetApartmentState(ApartmentState.STA);
        t.Start();
        t.Join();

        if (exception != null)
            throw exception;
    }

    public static object GetPolicySetting(string registryInformation)
    {
        string valueName;
        GroupPolicySection section;
        string key = Key(registryInformation, out valueName, out section);

        // Thread must be STA
        object result = null;
        var t = new Thread(() =>
        {
            var gpo = new ComputerGroupPolicyObject();
            using (RegistryKey rootRegistryKey = gpo.GetRootRegistryKey(section))
            {
                // Data can't be null so we can use this value to indicate key must be delete
                using (RegistryKey subKey = rootRegistryKey.OpenSubKey(key, true))
                {
                    if (subKey == null)
                    {
                        result = null;
                    }
                    else
                    {
                        result = subKey.GetValue(valueName);
                    }
                }
            }
        });
        t.SetApartmentState(ApartmentState.STA);
        t.Start();
        t.Join();

        return result;
    }

    private static string Key(string registryInformation, out string value, out GroupPolicySection section)
    {
        // Parse parameter of format HKCU\Software\Policies\Microsoft\Windows\Personalization!NoChangingSoundScheme
        string[] split = registryInformation.Split('!');
        string key = split[0];
        string hive = key.Substring(0, key.IndexOf('\\'));
        key = key.Substring(key.IndexOf('\\') + 1);

        value = split[1];

        if (hive.Equals(@"HKLM", StringComparison.OrdinalIgnoreCase)
            || hive.Equals(@"HKEY_LOCAL_MACHINE", StringComparison.OrdinalIgnoreCase))
        {
            section = GroupPolicySection.Machine;
        }
        else
        {
            section = GroupPolicySection.User;
        }
        return key;
    }

    /// <summary>
    ///     Retrieves the file system path to the root of the specified GPO section.
    ///     The path is in UNC format.
    /// </summary>
    public override string GetPathTo(GroupPolicySection section)
    {
        var sb = new StringBuilder(MaxLength);
        var result = Instance.GetFileSysPath((uint)section, sb, MaxLength);
        if (result != 0)
        {
            throw new Exception(string.Format("Unable to retrieve path to section '{0}'", Enum.GetName(typeof(GroupPolicySection), section)));
        }

        return sb.ToString();
    }
}

And how to use it:

static void Main(string[] args)
{
    ComputerGroupPolicyObject.SetPolicySetting(@"HKLM\Software\Policies\Microsoft\Windows\HomeGroup!DisableHomeGroup", "0", RegistryValueKind.DWord);
    ComputerGroupPolicyObject.SetPolicySetting(@"HKLM\Software\Policies\Microsoft\Windows\HomeGroup!DisableHomeGroup", "1", RegistryValueKind.DWord);
    ComputerGroupPolicyObject.SetPolicySetting(@"HKLM\Software\Policies\Microsoft\Windows\HomeGroup!DisableHomeGroup", null, RegistryValueKind.Unknown);
}

Code inspired from https://bitbucket.org/MartinEden/local-policy