Re: Synchronizing slots from primary to standby

Hi,

On Fri, Feb 23, 2024 at 02:15:11PM +0530, shveta malik wrote:
> On Fri, Feb 23, 2024 at 1:28 PM Bertrand Drouvot
> <bertranddrouvot.pg@gmail.com> wrote:
> >
> > Hi,
> >
> > Because one could create say the "=" OPERATOR in their own schema, attach a
> > function to it doing undesired stuff and change the search_path for the database
> > the sync slot worker connects to.
> >
> > Then this new "=" operator would be used (instead of the pg_catalog.= one),
> > triggering the "undesired" function as superuser.
> 
> Thanks for the details. I understand it now.  We do not use '=' in our
> main slots-fetch query but we do use '=' in remote-validation query.
> See validate_remote_info().

Oh, right, I missed it during the review.

> Do you think instead of doing the above,
> we can override search-path with empty string in the slot-sync case.
> SImilar to logical apply worker and autovacuum worker case (see
> InitializeLogRepWorker(), AutoVacWorkerMain()).

Yeah, we should definitively ensure that any operators being used in the query
is coming from the pg_catalog schema (could be by setting the search path or
using the up-thread proposal).

Setting the search path would prevent any risks in case the query is changed
later on, so I'd vote for changing the search path in validate_remote_info()
and in synchronize_slots() to be on the safe side.

Regards,

-- 
Bertrand Drouvot
PostgreSQL Contributors Team
RDS Open Source Databases
Amazon Web Services: https://aws.amazon.com