/usr/lib/x86_64-linux-gnu/libsl.so.0 is in libsl0-heimdal 1.6~git20120311.dfsg.1-2.
This file is owned by root:root, with mode 0o777.
It is a symlink to /usr/lib/x86_64-linux-gnu/libsl.so.0.2.1
/usr/lib/x86_64-linux-gnu/libsl.so.0.2.1