/usr/lib/x86_64-linux-gnu/libsignon-extension.so.1 is in libsignon-extension1 8.59+17.10.20170606-0ubuntu1.
This file is owned by root:root, with mode 0o777.
It is a symlink to /usr/lib/x86_64-linux-gnu/libsignon-extension.so.1.0.0