gio.debug_controller_dbus

[gio.debug_controller_dbus.DebugControllerDBus] is an implementation of [gio.debug_controller.DebugController] which exposes debug settings as a D-Bus object.

It is a [gio.initable.Initable] object, and will register an object at /org/gtk/Debugging on the bus given as [gio.debug_controller_dbus.DebugControllerDBus.connection] once it’s initialized. The object will be unregistered when the last reference to the [gio.debug_controller_dbus.DebugControllerDBus] is dropped.

This D-Bus object can be used by remote processes to enable or disable debug output in this process. Remote processes calling org.gtk.Debugging.SetDebugEnabled() will affect the value of property@Gio.DebugController:debug-enabled and, by default, func@GLib.log_get_debug_enabled.

By default, no processes are allowed to call SetDebugEnabled() unless a [gio.debug_controller_dbus.DebugControllerDBus.authorize] signal handler is installed. This is because the process may be privileged, or might expose sensitive information in its debug output. You may want to restrict the ability to enable debug output to privileged users or processes.

One option is to install a D-Bus security policy which restricts access to SetDebugEnabled(), installing something like the following in $datadir/dbus-1/system.d/:

<?xml version="1.0"?> <!--*-nxml-*-->
<!DOCTYPE busconfig PUBLIC "-//freedesktop//DTD D-BUS Bus Configuration 1.0//EN"
    "http://www.freedesktop.org/standards/dbus/1.0/busconfig.dtd">
<busconfig>
 <policy user="root">
   <allow send_destination="com.example.MyService" send_interface="org.gtk.Debugging"/>
 </policy>
 <policy context="default">
   <deny send_destination="com.example.MyService" send_interface="org.gtk.Debugging"/>
 </policy>
</busconfig>

This will prevent the SetDebugEnabled() method from being called by all except root. It will not prevent the DebugEnabled property from being read, as it’s accessed through the org.freedesktop.DBus.Properties interface.

Another option is to use polkit to allow or deny requests on a case-by-case basis, allowing for the possibility of dynamic authorisation. To do this, connect to the [gio.debug_controller_dbus.DebugControllerDBus.authorize] signal and query polkit in it:

g_autoptr(GError) child_error = NULL;
 g_autoptr(GDBusConnection) connection = g_bus_get_sync (G_BUS_TYPE_SYSTEM, NULL, NULL);
 gulong debug_controller_authorize_id = 0;

 // Set up the debug controller.
 debug_controller = G_DEBUG_CONTROLLER (g_debug_controller_dbus_new (priv->connection, NULL, &child_error));
 if (debug_controller == NULL)
   {
     g_error ("Could not register debug controller on bus: %s"),
              child_error->message);
   }

 debug_controller_authorize_id = g_signal_connect (debug_controller,
                                                   "authorize",
                                                   G_CALLBACK (debug_controller_authorize_cb),
                                                   self);

 static gboolean
 debug_controller_authorize_cb (GDebugControllerDBus  *debug_controller,
                                GDBusMethodInvocation *invocation,
                                gpointer               user_data)
 {
   g_autoptr(PolkitAuthority) authority = NULL;
   g_autoptr(PolkitSubject) subject = NULL;
   g_autoptr(PolkitAuthorizationResult) auth_result = NULL;
   g_autoptr(GError) local_error = NULL;
   GDBusMessage *message;
   GDBusMessageFlags message_flags;
   PolkitCheckAuthorizationFlags flags = POLKIT_CHECK_AUTHORIZATION_FLAGS_NONE;

   message = g_dbus_method_invocation_get_message (invocation);
   message_flags = g_dbus_message_get_flags (message);

   authority = polkit_authority_get_sync (NULL, &local_error);
   if (authority == NULL)
     {
       g_warning ("Failed to get polkit authority: %s", local_error->message);
       return FALSE;
     }

   if (message_flags & G_DBUS_MESSAGE_FLAGS_ALLOW_INTERACTIVE_AUTHORIZATION)
     flags |= POLKIT_CHECK_AUTHORIZATION_FLAGS_ALLOW_USER_INTERACTION;

   subject = polkit_system_bus_name_new (g_dbus_method_invocation_get_sender (invocation));

   auth_result = polkit_authority_check_authorization_sync (authority,
                                                            subject,
                                                            "com.example.MyService.set-debug-enabled",
                                                            NULL,
                                                            flags,
                                                            NULL,
                                                            &local_error);
   if (auth_result == NULL)
     {
       g_warning ("Failed to get check polkit authorization: %s", local_error->message);
       return FALSE;
     }

   return polkit_authorization_result_get_is_authorized (auth_result);
 }

Fluent builder for [gio.debug_controller_dbus.DebugControllerDBus]