+
+static int bus_check_peercred(sd_bus *c) {
+ int fd;
+ struct ucred ucred;
+ socklen_t l;
+
+ assert(c);
+
+ fd = sd_bus_get_fd(c);
+
+ assert(fd >= 0);
+
+ l = sizeof(struct ucred);
+ if (getsockopt(fd, SOL_SOCKET, SO_PEERCRED, &ucred, &l) < 0) {
+ log_error("SO_PEERCRED failed: %m");
+ return -errno;
+ }
+
+ if (l != sizeof(struct ucred)) {
+ log_error("SO_PEERCRED returned wrong size.");
+ return -E2BIG;
+ }
+
+ if (ucred.uid != 0 && ucred.uid != geteuid())
+ return -EPERM;
+
+ return 1;
+}
+
+int bus_connect_system(sd_bus **_bus) {
+ sd_bus *bus = NULL;
+ int r;
+ bool private = true;
+
+ assert(_bus);
+
+ if (geteuid() == 0) {
+ /* If we are root, then let's talk directly to the
+ * system instance, instead of going via the bus */
+
+ r = sd_bus_new(&bus);
+ if (r < 0)
+ return r;
+
+ r = sd_bus_set_address(bus, "unix:path=/run/systemd/private");
+ if (r < 0)
+ return r;
+
+ r = sd_bus_start(bus);
+ if (r < 0)
+ return r;
+
+ } else {
+ r = sd_bus_open_system(&bus);
+ if (r < 0)
+ return r;
+
+ private = false;
+ }
+
+ if (private) {
+ r = bus_check_peercred(bus);
+ if (r < 0) {
+ sd_bus_unref(bus);
+
+ return -EACCES;
+ }
+ }
+
+ *_bus = bus;
+ return 0;
+}