From 0a069ce62de904ae9cbaf23d026ac380b02e50e4 Mon Sep 17 00:00:00 2001 From: David Herrmann Date: Sat, 4 Jul 2015 12:14:45 +0200 Subject: core: harden cgroups-agent forwarding On dbus1, we receive systemd1.Agent signals via the private socket, hence it's trusted. However, on kdbus we receive it on the system bus. We must make sure it's sent by UID=0, otherwise unprivileged users can fake it. Furthermore, never forward broadcasts we sent ourself. This might happen on kdbus, as we forward the message on the same bus we received it on, thus ending up in an endless loop. --- src/core/dbus.c | 26 +++++++++++++++++++++++++- 1 file changed, 25 insertions(+), 1 deletion(-) (limited to 'src/core/dbus.c') diff --git a/src/core/dbus.c b/src/core/dbus.c index 86886e6d2c..6679ebadf1 100644 --- a/src/core/dbus.c +++ b/src/core/dbus.c @@ -69,13 +69,37 @@ int bus_send_queued_message(Manager *m) { } static int signal_agent_released(sd_bus_message *message, void *userdata, sd_bus_error *error) { + _cleanup_bus_creds_unref_ sd_bus_creds *creds = NULL; + const char *cgroup, *me; Manager *m = userdata; - const char *cgroup; + uid_t sender_uid; + sd_bus *bus; int r; assert(message); assert(m); + /* ignore recursive events sent by us on the system/user bus */ + bus = sd_bus_message_get_bus(message); + if (!sd_bus_is_server(bus)) { + r = sd_bus_get_unique_name(bus, &me); + if (r < 0) + return r; + + if (streq_ptr(sd_bus_message_get_sender(message), me)) + return 0; + } + + /* only accept org.freedesktop.systemd1.Agent from UID=0 */ + r = sd_bus_query_sender_creds(message, SD_BUS_CREDS_EUID, &creds); + if (r < 0) + return r; + + r = sd_bus_creds_get_euid(creds, &sender_uid); + if (r < 0 || sender_uid != 0) + return 0; + + /* parse 'cgroup-empty' notification */ r = sd_bus_message_read(message, "s", &cgroup); if (r < 0) { bus_log_parse_error(r); -- cgit v1.2.3-54-g00ecf