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From e3808a1b4042761055b1d975333a8243d67b8bfe Mon Sep 17 00:00:00 2001
From: Simon McVittie <smcv@collabora.com>
Date: Wed, 5 Jun 2019 13:33:38 +0100
Subject: [PATCH] gvfsdaemon: Check that the connecting client is the same user
Otherwise, an attacker who learns the abstract socket address from
netstat(8) or similar could connect to it and issue D-Bus method
calls.
Signed-off-by: Simon McVittie <smcv@collabora.com>
---
daemon/gvfsdaemon.c | 36 +++++++++++++++++++++++++++++++++++-
1 file changed, 35 insertions(+), 1 deletion(-)
diff --git a/daemon/gvfsdaemon.c b/daemon/gvfsdaemon.c
index 406d4f8e..be148a7b 100644
--- a/daemon/gvfsdaemon.c
+++ b/daemon/gvfsdaemon.c
@@ -79,6 +79,7 @@ struct _GVfsDaemon
gint mount_counter;
+ GDBusAuthObserver *auth_observer;
GDBusConnection *conn;
GVfsDBusDaemon *daemon_skeleton;
GVfsDBusMountable *mountable_skeleton;
@@ -171,6 +172,8 @@ g_vfs_daemon_finalize (GObject *object)
}
if (daemon->conn != NULL)
g_object_unref (daemon->conn);
+ if (daemon->auth_observer != NULL)
+ g_object_unref (daemon->auth_observer);
g_hash_table_destroy (daemon->registered_paths);
g_hash_table_destroy (daemon->client_connections);
@@ -236,6 +239,35 @@ name_vanished_handler (GDBusConnection *connection,
daemon->lost_main_daemon = TRUE;
}
+/*
+ * Authentication observer signal handler that authorizes connections
+ * from the same uid as this process. This matches the behaviour of a
+ * libdbus DBusServer/DBusConnection when no DBusAllowUnixUserFunction
+ * has been set, but is not the default in GDBus.
+ */
+static gboolean
+authorize_authenticated_peer_cb (GDBusAuthObserver *observer,
+ G_GNUC_UNUSED GIOStream *stream,
+ GCredentials *credentials,
+ G_GNUC_UNUSED gpointer user_data)
+{
+ gboolean authorized = FALSE;
+
+ if (credentials != NULL)
+ {
+ GCredentials *own_credentials;
+
+ own_credentials = g_credentials_new ();
+
+ if (g_credentials_is_same_user (credentials, own_credentials, NULL))
+ authorized = TRUE;
+
+ g_object_unref (own_credentials);
+ }
+
+ return authorized;
+}
+
static void
g_vfs_daemon_init (GVfsDaemon *daemon)
{
@@ -265,6 +297,8 @@ g_vfs_daemon_init (GVfsDaemon *daemon)
daemon->conn = g_bus_get_sync (G_BUS_TYPE_SESSION, NULL, NULL);
g_assert (daemon->conn != NULL);
+ daemon->auth_observer = g_dbus_auth_observer_new ();
+ g_signal_connect (daemon->auth_observer, "authorize-authenticated-peer", G_CALLBACK (authorize_authenticated_peer_cb), NULL);
daemon->daemon_skeleton = gvfs_dbus_daemon_skeleton_new ();
g_signal_connect (daemon->daemon_skeleton, "handle-get-connection", G_CALLBACK (handle_get_connection), daemon);
@@ -876,7 +910,7 @@ handle_get_connection (GVfsDBusDaemon *object,
server = g_dbus_server_new_sync (address1,
G_DBUS_SERVER_FLAGS_NONE,
guid,
- NULL, /* GDBusAuthObserver */
+ daemon->auth_observer,
NULL, /* GCancellable */
&error);
g_free (guid);
--
2.21.0
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