+
+_public_ int sd_bus_query_sender_privilege(sd_bus_message *call, int capability) {
+ _cleanup_bus_creds_unref_ sd_bus_creds *creds = NULL;
+ uid_t our_uid;
+ bool know_caps = false;
+ int r;
+
+ assert_return(call, -EINVAL);
+ assert_return(call->sealed, -EPERM);
+ assert_return(call->bus, -EINVAL);
+ assert_return(!bus_pid_changed(call->bus), -ECHILD);
+
+ if (!BUS_IS_OPEN(call->bus->state))
+ return -ENOTCONN;
+
+ if (capability >= 0) {
+ r = sd_bus_query_sender_creds(call, SD_BUS_CREDS_UID|SD_BUS_CREDS_EUID|SD_BUS_CREDS_EFFECTIVE_CAPS, &creds);
+ if (r < 0)
+ return r;
+
+ /* Note that not even on kdbus we might have the caps
+ * field, due to faked identities, or namespace
+ * translation issues. */
+ r = sd_bus_creds_has_effective_cap(creds, capability);
+ if (r > 0)
+ return 1;
+ if (r == 0)
+ know_caps = true;
+ } else {
+ r = sd_bus_query_sender_creds(call, SD_BUS_CREDS_UID|SD_BUS_CREDS_EUID, &creds);
+ if (r < 0)
+ return r;
+ }
+
+ /* Now, check the UID, but only if the capability check wasn't
+ * sufficient */
+ our_uid = getuid();
+ if (our_uid != 0 || !know_caps || capability < 0) {
+ uid_t sender_uid;
+
+ /* Try to use the EUID, if we have it. */
+ r = sd_bus_creds_get_euid(creds, &sender_uid);
+ if (r < 0)
+ r = sd_bus_creds_get_uid(creds, &sender_uid);
+
+ if (r >= 0) {
+ /* Sender has same UID as us, then let's grant access */
+ if (sender_uid == our_uid)
+ return 1;
+
+ /* Sender is root, we are not root. */
+ if (our_uid != 0 && sender_uid == 0)
+ return 1;
+ }
+ }
+
+ return 0;
+}