From 3d442dbf936d197aa11ca0a71663c2bc61696151 Mon Sep 17 00:00:00 2001
From: fujiwarat <takao.fujiwara1@gmail.com>
Date: Fri, 13 Sep 2019 15:59:03 +0900
Subject: [PATCH] bus: Implement GDBusAuthObserver callback
ibus uses a GDBusServer with G_DBUS_SERVER_FLAGS_AUTHENTICATION_ALLOW_ANONYMOUS,
and doesn't set a GDBusAuthObserver, which allows anyone who can connect
to its AF_UNIX socket to authenticate and be authorized to send method calls.
It also seems to use an abstract AF_UNIX socket, which does not have
filesystem permissions, so the practical effect might be that a local
attacker can connect to another user's ibus service and make arbitrary
method calls.
BUGS=rhbz#1717958
---
bus/server.c | 89 ++++++++++++++++++++++++++++++++++++++++++----------
1 file changed, 73 insertions(+), 16 deletions(-)
diff --git a/bus/server.c b/bus/server.c
index 3a626230..2439de14 100644
--- a/bus/server.c
+++ b/bus/server.c
@@ -2,7 +2,8 @@
/* vim:set et sts=4: */
/* bus - The Input Bus
* Copyright (C) 2008-2010 Peng Huang <shawn.p.huang@gmail.com>
- * Copyright (C) 2008-2010 Red Hat, Inc.
+ * Copyright (C) 2011-2019 Takao Fujiwara <takao.fujiwara1@gmail.com>
+ * Copyright (C) 2008-2019 Red Hat, Inc.
*
* This library is free software; you can redistribute it and/or
* modify it under the terms of the GNU Lesser General Public
@@ -70,16 +71,63 @@ _restart_server (void)
}
/**
+ * bus_allow_mechanism_cb:
+ * @observer: A #GDBusAuthObserver.
+ * @mechanism: The name of the mechanism.
+ * @user_data: always %NULL.
+ *
+ * Check if @mechanism can be used to authenticate the other peer.
+ * Returns: %TRUE if the peer's mechanism is allowed.
+ */
+static gboolean
+bus_allow_mechanism_cb (GDBusAuthObserver *observer,
+ const gchar *mechanism,
+ G_GNUC_UNUSED gpointer user_data)
+{
+ if (g_strcmp0 (mechanism, "EXTERNAL") == 0)
+ return TRUE;
+ return FALSE;
+}
+
+/**
+ * bus_authorize_authenticated_peer_cb:
+ * @observer: A #GDBusAuthObserver.
+ * @stream: A #GIOStream.
+ * @credentials: A #GCredentials.
+ * @user_data: always %NULL.
+ *
+ * Check if a peer who has already authenticated should be authorized.
+ * Returns: %TRUE if the peer's credential is authorized.
+ */
+static gboolean
+bus_authorize_authenticated_peer_cb (GDBusAuthObserver *observer,
+ GIOStream *stream,
+ GCredentials *credentials,
+ G_GNUC_UNUSED gpointer user_data)
+{
+ gboolean authorized = FALSE;
+ if (credentials) {
+ GCredentials *own_credentials = g_credentials_new ();
+ if (g_credentials_is_same_user (credentials, own_credentials, NULL))
+ authorized = TRUE;
+ g_object_unref (own_credentials);
+ }
+ return authorized;
+}
+
+/**
* bus_new_connection_cb:
- * @user_data: always NULL.
- * @returns: TRUE when the function can handle the connection.
+ * @observer: A #GDBusAuthObserver.
+ * @dbus_connection: A #GDBusconnection.
+ * @user_data: always %NULL.
*
* Handle incoming connections.
+ * Returns: %TRUE when the function can handle the connection.
*/
static gboolean
-bus_new_connection_cb (GDBusServer *server,
- GDBusConnection *dbus_connection,
- gpointer user_data)
+bus_new_connection_cb (GDBusServer *server,
+ GDBusConnection *dbus_connection,
+ G_GNUC_UNUSED gpointer user_data)
{
BusConnection *connection = bus_connection_new (dbus_connection);
bus_dbus_impl_new_connection (dbus, connection);
@@ -94,9 +142,9 @@ bus_new_connection_cb (GDBusServer *
}
static void
-_server_connect_start_portal_cb (GObject *source_object,
- GAsyncResult *res,
- gpointer user_data)
+_server_connect_start_portal_cb (GObject *source_object,
+ GAsyncResult *res,
+ G_GNUC_UNUSED gpointer user_data)
{
GVariant *result;
GError *error = NULL;
@@ -113,9 +161,9 @@ _server_connect_start_portal_cb (GObject
}
static void
-bus_acquired_handler (GDBusConnection *connection,
- const gchar *name,
- gpointer user_data)
+bus_acquired_handler (GDBusConnection *connection,
+ const gchar *name,
+ G_GNUC_UNUSED gpointer user_data)
{
g_dbus_connection_call (connection,
IBUS_SERVICE_PORTAL,
@@ -136,22 +184,27 @@ void
bus_server_init (void)
{
GError *error = NULL;
+ GDBusServerFlags flags = G_DBUS_SERVER_FLAGS_NONE;
+ gchar *guid;
+ GDBusAuthObserver *observer;
dbus = bus_dbus_impl_get_default ();
ibus = bus_ibus_impl_get_default ();
bus_dbus_impl_register_object (dbus, (IBusService *)ibus);
/* init server */
- GDBusServerFlags flags = G_DBUS_SERVER_FLAGS_AUTHENTICATION_ALLOW_ANONYMOUS;
- gchar *guid = g_dbus_generate_guid ();
- if (!g_str_has_prefix (g_address, "unix:tmpdir=")) {
- g_error ("Your socket address does not have the format unix:tmpdir=$DIR; %s",
- g_address);
+ guid = g_dbus_generate_guid ();
+ observer = g_dbus_auth_observer_new ();
+ if (!g_str_has_prefix (g_address, "unix:tmpdir=") &&
+ !g_str_has_prefix (g_address, "unix:path=")) {
+ g_error ("Your socket address does not have the format unix:tmpdir=$DIR "
+ "or unix:path=$FILE; %s", g_address);
+
}
server = g_dbus_server_new_sync (
g_address, /* the place where the socket file lives, e.g. /tmp, abstract namespace, etc. */
flags, guid,
- NULL /* observer */,
+ observer,
NULL /* cancellable */,
&error);
if (server == NULL) {
@@ -161,7 +214,13 @@ bus_server_init (void)
}
g_free (guid);
- g_signal_connect (server, "new-connection", G_CALLBACK (bus_new_connection_cb), NULL);
+ g_signal_connect (observer, "allow-mechanism",
+ G_CALLBACK (bus_allow_mechanism_cb), NULL);
+ g_signal_connect (observer, "authorize-authenticated-peer",
+ G_CALLBACK (bus_authorize_authenticated_peer_cb), NULL);
+ g_object_unref (observer);
+ g_signal_connect (server, "new-connection",
+ G_CALLBACK (bus_new_connection_cb), NULL);
g_dbus_server_start (server);
--
2.21.0