Re: Largeobject Access Controls (r2460)

KaiGai Kohei <kaigai(at)ak(dot)jp(dot)nec(dot)com> wrote:

> Tom Lane wrote:
> > Takahiro Itagaki <itagaki(dot)takahiro(at)oss(dot)ntt(dot)co(dot)jp> writes:
> >> <structname>pg_largeobject</structname> should not be readable by the
> >> public, since the catalog contains data in large objects of all users.
> >
> > This is going to be a problem, because it will break applications that
> > expect to be able to read pg_largeobject. Like, say, pg_dump.
>
> Is it a right behavior, even if we have permission checks on large objects?

Can we use column-level access control here?

REVOKE ALL ON pg_largeobject FROM PUBLIC;
=> GRANT SELECT (loid) ON pg_largeobject TO PUBLIC;

We use "SELECT loid FROM pg_largeobject LIMIT 1" in pg_dump. We could
replace pg_largeobject_metadata instead if we try to fix only pg_dump,
but it's no wonder that any other user applications use such queries.
I think to allow reading loid is a balanced solution.

> If so, we can inject a hardwired rule to prevent to select pg_largeobject
> when lo_compat_privileges is turned off, instead of REVOKE ALL FROM PUBLIC.

Is it enough to run "GRANT SELECT ON pg_largeobject TO PUBLIC" ?

Regards,
---
Takahiro Itagaki
NTT Open Source Software Center