GDebugControllerDBus: GIO Reference Manual

## GDebugControllerDBus GDebugControllerDBus — Debugging controller D-Bus implementation |

## Functions

GDebugControllerDBus * | g_debug_controller_dbus_new ()
void | g_debug_controller_dbus_stop ()

## Properties

GDBusConnection * | connection | Read / Write / Construct Only

## Signals

gboolean | authorize | Run Last

## Types and Values

| GDebugControllerDBus

## Object Hierarchy

        GObject
        ╰── GDebugControllerDBus

## Implemented Interfaces

GDebugControllerDBus implements GInitable and GDebugController.

## Includes

    #include <gio/gio.h>

## Description

GDebugControllerDBus is an implementation of GDebugController which exposes debug settings as a D-Bus object.

It is a GInitable object, and will register an object at `/org/gtk/Debugging` on the bus given as “connection” once it’s initialized. The object will be unregistered when the last reference to the GDebugControllerDBus 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 “debug-enabled” and, by default, `g_log_get_debug_enabled()`. default.

By default, no processes are allowed to call ``SetDebugEnabled()`` unless a “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/`:

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    <?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 “authorize” signal and query polkit in it:

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    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);
    }

## Functions

### g_debug_controller_dbus_new ()

    GDebugControllerDBus *
    g_debug_controller_dbus_new (GDBusConnection *connection,
                                 GCancellable *cancellable,
                                 GError **error);

Create a new GDebugControllerDBus and synchronously initialize it.

Initializing the object will export the debug object on `connection` . The object will remain registered until the last reference to the GDebugControllerDBus is dropped.

Initialization may fail if registering the object on `connection` fails.

#### Parameters

connection | a GDBusConnection to register the debug object on |
cancellable | a GCancellable, or `NULL`. | [nullable]
error | return location for a GError, or `NULL` |

#### Returns

a new GDebugControllerDBus, or `NULL` on failure.

[nullable][transfer full]

Since: 2.72

### g_debug_controller_dbus_stop ()

    void
    g_debug_controller_dbus_stop (GDebugControllerDBus *self);

Stop the debug controller, unregistering its object from the bus.

Any pending method calls to the object will complete successfully, but new ones will return an error. This method will block until all pending “authorize” signals have been handled. This is expected to not take long, as it will just be waiting for threads to join. If any “authorize” signal handlers are still executing in other threads, this will block until after they have returned.

This method will be called automatically when the final reference to the GDebugControllerDBus is dropped. You may want to call it explicitly to know when the controller has been fully removed from the bus, or to break reference count cycles.

Calling this method from within a “authorize” signal handler will cause a deadlock and must not be done.

#### Parameters

self | a GDebugControllerDBus |

Since: 2.72

## Types and Values

### GDebugControllerDBus

    typedef struct _GDebugControllerDBus GDebugControllerDBus;

GDebugControllerDBus is an implementation of GDebugController over D-Bus.

Since: 2.72

## Property Details

### The `“connection”` property

      “connection”               GDBusConnection *

The D-Bus connection to expose the debugging interface on.

Typically this will be the same connection (to the system or session bus) which the rest of the application or service’s D-Bus objects are registered on.

Owner: GDebugControllerDBus

Flags: Read / Write / Construct Only

Since: 2.72

## Signal Details

### The `“authorize”` signal

    gboolean
    user_function (GDebugControllerDBus  *controller,
                   GDBusMethodInvocation *invocation,
                   gpointer               user_data)

Emitted when a D-Bus peer is trying to change the debug settings and used to determine if that is authorized.

This signal is emitted in a dedicated worker thread, so handlers are allowed to perform blocking I/O. This means that, for example, it is appropriate to call ``polkit_authority_check_authorization_sync()`` to check authorization using polkit.

If `FALSE` is returned then no further handlers are run and the request to change the debug settings is rejected.

Otherwise, if `TRUE` is returned, signal emission continues. If no handlers return `FALSE`, then the debug settings are allowed to be changed.

Signal handlers must not modify `invocation` , or cause it to return a value.

The default class handler just returns `TRUE`.

#### Parameters

controller | The GDebugControllerDBus emitting the signal. |
invocation | A GDBusMethodInvocation. |
user_data | user data set when the signal handler was connected. |

#### Returns

`TRUE` if the call is authorized, `FALSE` otherwise.

Flags: Run Last

Since: 2.72