Question

I am trying to have my program determine if it has permission to delete a registry key in C#. I have been trying this code which is returning true when in fact I don’t have the right permissions for the registry key.

public static bool CanDeleteKey(RegistryKey key)
{
    try
    {
        if (key.SubKeyCount > 0)
        {
            bool ret = false;

            foreach (string subKey in key.GetSubKeyNames())
            {
                ret = CanDeleteKey(key.OpenSubKey(subKey));

                if (!ret)
                    break;
            }

            return ret;
        }
        else
        {
            RegistryPermission r = new 
          RegistryPermission(RegistryPermissionAccess.AllAccess, key.ToString());
            r.Demand();
            return true;
        }

    }
    catch (SecurityException)
    {
        return false;
    }
}

The registry key that I am passing to this function is HKEY_CLASSES_ROOT\eHomeSchedulerService.TVThumbnailCache. It should be re-cursing to the sub key CLSID and returning false because the Full Control permission is only set for TrustedInstaller.

Here are the permissions for HKEY_CLASSES_ROOT\eHomeSchedulerService.TVThumbnailCache\CLSID from regedit:

I should note that I am running the code with Administrative privileges. Also, I know I can just use a try-catch block when I am deleting the registry key but I would like to know if I can delete it beforehand.

Answer 1

I was able to do some digging on Google and I came up with this code which seems to do the trick:

    /// Checks if we have permission to delete a registry key
    /// </summary>
    /// <param name="key">Registry key</param>
    /// <returns>True if we can delete it</returns>
    public static bool CanDeleteKey(RegistryKey key)
    {
        try
        {
            if (key.SubKeyCount > 0)
            {
                bool ret = false;

                foreach (string subKey in key.GetSubKeyNames())
                {
                    ret = CanDeleteKey(key.OpenSubKey(subKey));

                    if (!ret)
                        break;
                }

                return ret;
            }
            else
            {
                System.Security.AccessControl.RegistrySecurity regSecurity = key.GetAccessControl();

                foreach (System.Security.AccessControl.AuthorizationRule rule in regSecurity.GetAccessRules(true, false, typeof(System.Security.Principal.NTAccount)))
                {
                    if ((System.Security.AccessControl.RegistryRights.Delete & ((System.Security.AccessControl.RegistryAccessRule)(rule)).RegistryRights) != System.Security.AccessControl.RegistryRights.Delete)
                    {
                        return false;
                    }
                }

                return true;
            }

        }
        catch (SecurityException)
        {
            return false;
        }
    }