/usr/lib/x86_64-linux-gnu/libffi.so is in libffi-dev 3.0.10-3.
This file is owned by root:root, with mode 0o777.
It is a symlink to /usr/lib/x86_64-linux-gnu/libffi.so.5.0.10
/usr/lib/x86_64-linux-gnu/libffi.so.5.0.10