Re: Possibility to disable `ALTER SYSTEM`

On Tue, Mar 19, 2024 at 3:52 PM Tom Lane <tgl@sss.pgh.pa.us> wrote:
>
> Heikki Linnakangas <hlinnaka@iki.fi> writes:
> > Perhaps we could make that even better with a GUC though. I propose a
> > GUC called 'configuration_managed_externally = true / false". If you set
> > it to true, we prevent ALTER SYSTEM and make the error message more
> > definitive:
>
> > postgres=# ALTER SYSTEM SET wal_level TO minimal;
> > ERROR:  configuration is managed externally
>
> > As a bonus, if that GUC is set, we could even check at server startup
> > that all the configuration files are not writable by the postgres user,
> > and print a warning or refuse to start up if they are.
>
> I like this idea.  The "bonus" is not optional though, because
> setting the files' ownership/permissions is the only way to be
> sure that the prohibition is even a little bit bulletproof.
>
> One small issue: how do we make that work on Windows?  Have recent
> versions grown anything that looks like real file permissions?

Windows has had full ACL support since 1993. The  easiest way to do
what you're doing here is to just set a DENY permission on the
postgres operating system user.


//Magnus