/* GIO - GLib Input, Output and Streaming Library
*
* Copyright © 2021 Endless OS Foundation, LLC
*
* SPDX-License-Identifier: LGPL-2.1-or-later
*
* This library is free software; you can redistribute it and/or
* modify it under the terms of the GNU Lesser General Public
* License as published by the Free Software Foundation; either
* version 2.1 of the License, or (at your option) any later version.
*
* This library is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
* Lesser General Public License for more details.
*
* You should have received a copy of the GNU Lesser General
* Public License along with this library; if not, see .
*
* SPDX-License-Identifier: LGPL-2.1-or-later
*/
#include "config.h"
#include
#include "gdebugcontroller.h"
#include "gdebugcontrollerdbus.h"
#include "giomodule-priv.h"
#include "gi18n.h"
#include "gio/gdbusprivate.h"
#include "gio/gmarshal-internal.h"
/**
* SECTION:gdebugcontrollerdbus
* @title: GDebugControllerDBus
* @short_description: Debugging controller D-Bus implementation
* @include: gio/gio.h
*
* #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
* #GDebugControllerDBus: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
* #GDebugController:debug-enabled and, by default, g_log_get_debug_enabled().
* default.
*
* By default, no processes are allowed to call `SetDebugEnabled()` unless a
* #GDebugControllerDBus::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/`:
* |[
*
*
*
*
*
*
*
*
*
*
* ]|
*
* 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 #GDebugControllerDBus::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);
* }
* ]|
*
* Since: 2.72
*/
static const gchar org_gtk_Debugging_xml[] =
""
""
""
""
""
""
""
"";
static GDBusInterfaceInfo *org_gtk_Debugging;
#define G_DEBUG_CONTROLLER_DBUS_GET_INITABLE_IFACE(o) (G_TYPE_INSTANCE_GET_INTERFACE ((o), G_TYPE_INITABLE, GInitable))
static void g_debug_controller_dbus_iface_init (GDebugControllerInterface *iface);
static void g_debug_controller_dbus_initable_iface_init (GInitableIface *iface);
static gboolean g_debug_controller_dbus_authorize_default (GDebugControllerDBus *self,
GDBusMethodInvocation *invocation);
typedef enum
{
PROP_CONNECTION = 1,
/* Overrides: */
PROP_DEBUG_ENABLED,
} GDebugControllerDBusProperty;
static GParamSpec *props[PROP_CONNECTION + 1] = { NULL, };
typedef enum
{
SIGNAL_AUTHORIZE,
} GDebugControllerDBusSignal;
static guint signals[SIGNAL_AUTHORIZE + 1] = {0};
typedef struct
{
GObject parent_instance;
GCancellable *cancellable; /* (owned) */
GDBusConnection *connection; /* (owned) */
guint object_id;
GPtrArray *pending_authorize_tasks; /* (element-type GWeakRef) (owned) (nullable) */
gboolean debug_enabled;
} GDebugControllerDBusPrivate;
G_DEFINE_TYPE_WITH_CODE (GDebugControllerDBus, g_debug_controller_dbus, G_TYPE_OBJECT,
G_ADD_PRIVATE (GDebugControllerDBus)
G_IMPLEMENT_INTERFACE (G_TYPE_INITABLE,
g_debug_controller_dbus_initable_iface_init)
G_IMPLEMENT_INTERFACE (G_TYPE_DEBUG_CONTROLLER,
g_debug_controller_dbus_iface_init)
_g_io_modules_ensure_extension_points_registered ();
g_io_extension_point_implement (G_DEBUG_CONTROLLER_EXTENSION_POINT_NAME,
g_define_type_id,
"dbus",
30))
static void
g_debug_controller_dbus_init (GDebugControllerDBus *self)
{
GDebugControllerDBusPrivate *priv = g_debug_controller_dbus_get_instance_private (self);
priv->cancellable = g_cancellable_new ();
}
static void
set_debug_enabled (GDebugControllerDBus *self,
gboolean debug_enabled)
{
GDebugControllerDBusPrivate *priv = g_debug_controller_dbus_get_instance_private (self);
if (g_cancellable_is_cancelled (priv->cancellable))
return;
if (debug_enabled != priv->debug_enabled)
{
GVariantBuilder builder;
priv->debug_enabled = debug_enabled;
/* Change the default log writer’s behaviour in GLib. */
g_log_set_debug_enabled (debug_enabled);
/* Notify internally and externally of the property change. */
g_object_notify (G_OBJECT (self), "debug-enabled");
g_variant_builder_init (&builder, G_VARIANT_TYPE ("a{sv}"));
g_variant_builder_add (&builder, "{sv}", "DebugEnabled", g_variant_new_boolean (priv->debug_enabled));
g_dbus_connection_emit_signal (priv->connection,
NULL,
"/org/gtk/Debugging",
"org.freedesktop.DBus.Properties",
"PropertiesChanged",
g_variant_new ("(sa{sv}as)",
"org.gtk.Debugging",
&builder,
NULL),
NULL);
g_debug ("Debug output %s", debug_enabled ? "enabled" : "disabled");
}
}
/* Called in the #GMainContext which was default when the #GDebugControllerDBus
* was initialised. */
static GVariant *
dbus_get_property (GDBusConnection *connection,
const gchar *sender,
const gchar *object_path,
const gchar *interface_name,
const gchar *property_name,
GError **error,
gpointer user_data)
{
GDebugControllerDBus *self = user_data;
GDebugControllerDBusPrivate *priv = g_debug_controller_dbus_get_instance_private (self);
if (g_str_equal (property_name, "DebugEnabled"))
return g_variant_new_boolean (priv->debug_enabled);
g_assert_not_reached ();
return NULL;
}
static GWeakRef *
weak_ref_new (GObject *obj)
{
GWeakRef *weak_ref = g_new0 (GWeakRef, 1);
g_weak_ref_init (weak_ref, obj);
return g_steal_pointer (&weak_ref);
}
static void
weak_ref_free (GWeakRef *weak_ref)
{
g_weak_ref_clear (weak_ref);
g_free (weak_ref);
}
/* Called in the #GMainContext which was default when the #GDebugControllerDBus
* was initialised. */
static void
garbage_collect_weak_refs (GDebugControllerDBus *self)
{
GDebugControllerDBusPrivate *priv = g_debug_controller_dbus_get_instance_private (self);
guint i;
if (priv->pending_authorize_tasks == NULL)
return;
/* Iterate in reverse order so that if we remove an element the hole won’t be
* filled by an element we haven’t checked yet. */
for (i = priv->pending_authorize_tasks->len; i > 0; i--)
{
GWeakRef *weak_ref = g_ptr_array_index (priv->pending_authorize_tasks, i - 1);
GObject *obj = g_weak_ref_get (weak_ref);
if (obj == NULL)
g_ptr_array_remove_index_fast (priv->pending_authorize_tasks, i - 1);
else
g_object_unref (obj);
}
/* Don’t need to keep the array around any more if it’s empty. */
if (priv->pending_authorize_tasks->len == 0)
g_clear_pointer (&priv->pending_authorize_tasks, g_ptr_array_unref);
}
/* Called in a worker thread. */
static void
authorize_task_cb (GTask *task,
gpointer source_object,
gpointer task_data,
GCancellable *cancellable)
{
GDebugControllerDBus *self = G_DEBUG_CONTROLLER_DBUS (source_object);
GDBusMethodInvocation *invocation = G_DBUS_METHOD_INVOCATION (task_data);
gboolean authorized = TRUE;
g_signal_emit (self, signals[SIGNAL_AUTHORIZE], 0, invocation, &authorized);
g_task_return_boolean (task, authorized);
}
/* Called in the #GMainContext which was default when the #GDebugControllerDBus
* was initialised. */
static void
authorize_cb (GObject *object,
GAsyncResult *result,
gpointer user_data)
{
GDebugControllerDBus *self = G_DEBUG_CONTROLLER_DBUS (object);
GDebugControllerDBusPrivate *priv G_GNUC_UNUSED /* when compiling with G_DISABLE_ASSERT */;
GTask *task = G_TASK (result);
GDBusMethodInvocation *invocation = g_task_get_task_data (task);
GVariant *parameters = g_dbus_method_invocation_get_parameters (invocation);
gboolean enabled = FALSE;
gboolean authorized;
priv = g_debug_controller_dbus_get_instance_private (self);
authorized = g_task_propagate_boolean (task, NULL);
if (!authorized)
{
GError *local_error = g_error_new (G_DBUS_ERROR, G_DBUS_ERROR_ACCESS_DENIED,
_("Not authorized to change debug settings"));
g_dbus_method_invocation_take_error (invocation, g_steal_pointer (&local_error));
}
else
{
/* Update the property value. */
g_variant_get (parameters, "(b)", &enabled);
set_debug_enabled (self, enabled);
g_dbus_method_invocation_return_value (invocation, NULL);
}
/* The GTask will stay alive for a bit longer as the worker thread is
* potentially still in the process of dropping its reference to it. */
g_assert (priv->pending_authorize_tasks != NULL && priv->pending_authorize_tasks->len > 0);
}
/* Called in the #GMainContext which was default when the #GDebugControllerDBus
* was initialised. */
static void
dbus_method_call (GDBusConnection *connection,
const gchar *sender,
const gchar *object_path,
const gchar *interface_name,
const gchar *method_name,
GVariant *parameters,
GDBusMethodInvocation *invocation,
gpointer user_data)
{
GDebugControllerDBus *self = user_data;
GDebugControllerDBusPrivate *priv = g_debug_controller_dbus_get_instance_private (self);
GDebugControllerDBusClass *klass = G_DEBUG_CONTROLLER_DBUS_GET_CLASS (self);
/* Only on the org.gtk.Debugging interface */
if (g_str_equal (method_name, "SetDebugEnabled"))
{
GTask *task = NULL;
task = g_task_new (self, priv->cancellable, authorize_cb, NULL);
g_task_set_source_tag (task, dbus_method_call);
g_task_set_task_data (task, g_object_ref (invocation), (GDestroyNotify) g_object_unref);
/* Track the pending #GTask with a weak ref as its final strong ref could
* be dropped from this thread or an arbitrary #GTask worker thread. The
* weak refs will be evaluated in g_debug_controller_dbus_stop(). */
if (priv->pending_authorize_tasks == NULL)
priv->pending_authorize_tasks = g_ptr_array_new_with_free_func ((GDestroyNotify) weak_ref_free);
g_ptr_array_add (priv->pending_authorize_tasks, weak_ref_new (G_OBJECT (task)));
/* Take the opportunity to clean up a bit. */
garbage_collect_weak_refs (self);
/* Check the calling peer is authorised to change the debug mode. So that
* the signal handler can block on checking polkit authorisation (which
* definitely involves D-Bus calls, and might involve user interaction),
* emit the #GDebugControllerDBus::authorize signal in a worker thread, so
* that handlers can synchronously block it. This is similar to how
* #GDBusInterfaceSkeleton::g-authorize-method works.
*
* If no signal handlers are connected, don’t bother running the worker
* thread, and just return a default value of %FALSE. Fail closed. */
if (g_signal_has_handler_pending (self, signals[SIGNAL_AUTHORIZE], 0, FALSE) ||
klass->authorize != g_debug_controller_dbus_authorize_default)
g_task_run_in_thread (task, authorize_task_cb);
else
g_task_return_boolean (task, FALSE);
g_clear_object (&task);
}
else
g_assert_not_reached ();
}
static gboolean
g_debug_controller_dbus_initable_init (GInitable *initable,
GCancellable *cancellable,
GError **error)
{
GDebugControllerDBus *self = G_DEBUG_CONTROLLER_DBUS (initable);
GDebugControllerDBusPrivate *priv = g_debug_controller_dbus_get_instance_private (self);
static const GDBusInterfaceVTable vtable = {
dbus_method_call,
dbus_get_property,
NULL /* set_property */,
{ 0 }
};
if (org_gtk_Debugging == NULL)
{
GError *local_error = NULL;
GDBusNodeInfo *info;
info = g_dbus_node_info_new_for_xml (org_gtk_Debugging_xml, &local_error);
if G_UNLIKELY (info == NULL)
g_error ("%s", local_error->message);
org_gtk_Debugging = g_dbus_node_info_lookup_interface (info, "org.gtk.Debugging");
g_assert (org_gtk_Debugging != NULL);
g_dbus_interface_info_ref (org_gtk_Debugging);
g_dbus_node_info_unref (info);
}
priv->object_id = g_dbus_connection_register_object (priv->connection,
"/org/gtk/Debugging",
org_gtk_Debugging,
&vtable, self, NULL, error);
if (priv->object_id == 0)
return FALSE;
return TRUE;
}
static void
g_debug_controller_dbus_get_property (GObject *object,
guint prop_id,
GValue *value,
GParamSpec *pspec)
{
GDebugControllerDBus *self = G_DEBUG_CONTROLLER_DBUS (object);
GDebugControllerDBusPrivate *priv = g_debug_controller_dbus_get_instance_private (self);
switch ((GDebugControllerDBusProperty) prop_id)
{
case PROP_CONNECTION:
g_value_set_object (value, priv->connection);
break;
case PROP_DEBUG_ENABLED:
g_value_set_boolean (value, priv->debug_enabled);
break;
default:
G_OBJECT_WARN_INVALID_PROPERTY_ID (object, prop_id, pspec);
break;
}
}
static void
g_debug_controller_dbus_set_property (GObject *object,
guint prop_id,
const GValue *value,
GParamSpec *pspec)
{
GDebugControllerDBus *self = G_DEBUG_CONTROLLER_DBUS (object);
GDebugControllerDBusPrivate *priv = g_debug_controller_dbus_get_instance_private (self);
switch ((GDebugControllerDBusProperty) prop_id)
{
case PROP_CONNECTION:
/* Construct only */
g_assert (priv->connection == NULL);
priv->connection = g_value_dup_object (value);
break;
case PROP_DEBUG_ENABLED:
set_debug_enabled (self, g_value_get_boolean (value));
break;
default:
G_OBJECT_WARN_INVALID_PROPERTY_ID (object, prop_id, pspec);
break;
}
}
static void
g_debug_controller_dbus_dispose (GObject *object)
{
GDebugControllerDBus *self = G_DEBUG_CONTROLLER_DBUS (object);
GDebugControllerDBusPrivate *priv = g_debug_controller_dbus_get_instance_private (self);
g_debug_controller_dbus_stop (self);
g_assert (priv->pending_authorize_tasks == NULL);
g_clear_object (&priv->connection);
g_clear_object (&priv->cancellable);
G_OBJECT_CLASS (g_debug_controller_dbus_parent_class)->dispose (object);
}
static gboolean
g_debug_controller_dbus_authorize_default (GDebugControllerDBus *self,
GDBusMethodInvocation *invocation)
{
return TRUE;
}
static void
g_debug_controller_dbus_class_init (GDebugControllerDBusClass *klass)
{
GObjectClass *gobject_class = G_OBJECT_CLASS (klass);
gobject_class->get_property = g_debug_controller_dbus_get_property;
gobject_class->set_property = g_debug_controller_dbus_set_property;
gobject_class->dispose = g_debug_controller_dbus_dispose;
klass->authorize = g_debug_controller_dbus_authorize_default;
/**
* GDebugControllerDBus:connection:
*
* 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.
*
* Since: 2.72
*/
props[PROP_CONNECTION] =
g_param_spec_object ("connection", NULL, NULL,
G_TYPE_DBUS_CONNECTION,
G_PARAM_READWRITE |
G_PARAM_CONSTRUCT_ONLY |
G_PARAM_STATIC_STRINGS);
g_object_class_install_properties (gobject_class, G_N_ELEMENTS (props), props);
g_object_class_override_property (gobject_class, PROP_DEBUG_ENABLED, "debug-enabled");
/**
* GDebugControllerDBus::authorize:
* @controller: The #GDebugControllerDBus emitting the signal.
* @invocation: A #GDBusMethodInvocation.
*
* 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.
*
* Returns: %TRUE if the call is authorized, %FALSE otherwise.
*
* Since: 2.72
*/
signals[SIGNAL_AUTHORIZE] =
g_signal_new ("authorize",
G_TYPE_DEBUG_CONTROLLER_DBUS,
G_SIGNAL_RUN_LAST,
G_STRUCT_OFFSET (GDebugControllerDBusClass, authorize),
_g_signal_accumulator_false_handled,
NULL,
_g_cclosure_marshal_BOOLEAN__OBJECT,
G_TYPE_BOOLEAN,
1,
G_TYPE_DBUS_METHOD_INVOCATION);
g_signal_set_va_marshaller (signals[SIGNAL_AUTHORIZE],
G_TYPE_FROM_CLASS (klass),
_g_cclosure_marshal_BOOLEAN__OBJECTv);
}
static void
g_debug_controller_dbus_iface_init (GDebugControllerInterface *iface)
{
}
static void
g_debug_controller_dbus_initable_iface_init (GInitableIface *iface)
{
iface->init = g_debug_controller_dbus_initable_init;
}
/**
* g_debug_controller_dbus_new:
* @connection: a #GDBusConnection to register the debug object on
* @cancellable: (nullable): a #GCancellable, or %NULL
* @error: return location for a #GError, or %NULL
*
* 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.
*
* Returns: (nullable) (transfer full): a new #GDebugControllerDBus, or %NULL
* on failure
* Since: 2.72
*/
GDebugControllerDBus *
g_debug_controller_dbus_new (GDBusConnection *connection,
GCancellable *cancellable,
GError **error)
{
g_return_val_if_fail (G_IS_DBUS_CONNECTION (connection), NULL);
g_return_val_if_fail (cancellable == NULL || G_IS_CANCELLABLE (cancellable), NULL);
g_return_val_if_fail (error == NULL || *error == NULL, NULL);
return g_initable_new (G_TYPE_DEBUG_CONTROLLER_DBUS,
cancellable,
error,
"connection", connection,
NULL);
}
/**
* g_debug_controller_dbus_stop:
* @self: a #GDebugControllerDBus
*
* 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
* #GDebugControllerDBus::authorize signals have been handled. This is expected
* to not take long, as it will just be waiting for threads to join. If any
* #GDebugControllerDBus::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 #GDebugControllerDBus::authorize signal
* handler will cause a deadlock and must not be done.
*
* Since: 2.72
*/
void
g_debug_controller_dbus_stop (GDebugControllerDBus *self)
{
GDebugControllerDBusPrivate *priv = g_debug_controller_dbus_get_instance_private (self);
g_cancellable_cancel (priv->cancellable);
if (priv->object_id != 0)
{
g_dbus_connection_unregister_object (priv->connection, priv->object_id);
priv->object_id = 0;
}
/* Wait for any pending authorize tasks to finish. These will just be waiting
* for threads to join at this point, as the D-Bus object has been
* unregistered and the cancellable cancelled.
*
* The loop will never terminate if g_debug_controller_dbus_stop() is
* called from within an ::authorize callback.
*
* See discussion in https://gitlab.gnome.org/GNOME/glib/-/merge_requests/2486 */
while (priv->pending_authorize_tasks != NULL)
{
garbage_collect_weak_refs (self);
g_thread_yield ();
}
}