Re: prevent users from SELECT-ing from pg_roles/pg_database

På fredag 24. mai 2024 kl. 19:02:13, skrev Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us
<mailto:tgl(at)sss(dot)pgh(dot)pa(dot)us>>:
Andreas Joseph Krogh <andreas(at)visena(dot)com> writes:
> Hi, is there a way to prevent a user/role from SELECT-ing from certain
> system-tables?
> I'd like the contents of pg_{user,roles,database} to not be visible to all
> users.

As noted, you can in principle revoke the public SELECT grant from
those views/catalogs. However, the system is not designed to hide
such information, which means you'll have (at least) two kinds of
issues to worry about:

1. Queries or tools breaking that you didn't expect to break.
It's hardly uncommon for instance for queries on pg_class to
join to pg_roles to get the owner names for tables.

2. Information leaks. For example, mapping role OID to role name
is trivial with either regrole or pg_get_userbyid(), so it
wouldn't take long to scan the plausible range of role OIDs and
get all their names, even without SQL access to the underlying
catalog.

regards, tom lane

I tried:
REVOKE SELECT ON pg_catalog.pg_database FROM public;
But that doesn't prevent a normal user from querying pg_database it seems…

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Andreas Joseph Krogh
CTO / Partner - Visena AS
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