Revoking usage of pg_catalog

Hi there!

Is it possible to revoke usage of pg_catalog for a specific user?

The reason is to secure PostgreSQL. If a user can connect to a database, it
could query pg_class, pg_attribute, pg_proc search for specific tables and
if using dblink, even database passwords...

I just made a test, revoking usage of pg_catalog from PUBLIC, but tables are
still available through "SELECT * FROM pg_class", but not through "SELECT *
FROM pg_catalog.pg_class". I found in manual, where it says pg_catalog is
searched before any schema on search_path...

If schema pg_catalog became blocked, PostgreSQL could be used? Could it be
possible to made queries on allowed schemas and tables? This could be an
item for the wishlist?

Kind regards,
--
Daniel Cristian Cruz