pam_unix(8) requires root priveleges to access master.passwd(5),
so try authenticating via setuid helper first.

--- etc/pam.d/hikari-unlocker.FreeBSD.orig	2020-03-05 21:52:17 UTC
+++ etc/pam.d/hikari-unlocker.FreeBSD
@@ -1 +1 @@
-auth include passwd
+auth include unix-selfauth