/lib/libnss_rsbac.so.2 is in libnss-rsbac2 1.4.0-repack-0ubuntu3.
This file is owned by root:root, with mode 0o777.
It is a symlink to /lib/libnss_rsbac.so.2.0.0
/lib/libnss_rsbac.so.2.0.0