/usr/share/man/man3/RSA_flags.3ssl.gz is in libssl-doc 1.0.2g-1ubuntu4.
This file is owned by root:root, with mode 0o777.
It is a symlink to /usr/share/man/man3/RSA_set_method.3ssl.gz
/usr/share/man/man3/RSA_set_method.3ssl.gz