/usr/lib/x86_64-linux-gnu/libtirpc.so is in libtirpc-dev 0.2.5-1.2+deb9u1.
This file is owned by root:root, with mode 0o777.
It is a symlink to /lib/x86_64-linux-gnu/libtirpc.so.1.0.10
/lib/x86_64-linux-gnu/libtirpc.so.1.0.10