/usr/lib/x86_64-linux-gnu/librpmsign.so.3 is in librpmsign3 4.12.0.1+dfsg1-3build3.
This file is owned by root:root, with mode 0o777.
It is a symlink to /usr/lib/x86_64-linux-gnu/librpmsign.so.3.3.1
/usr/lib/x86_64-linux-gnu/librpmsign.so.3.3.1