Re: Allow placeholders in ALTER ROLE w/o superuser

On Sun, Jun 05, 2022 at 11:20:38PM -0500, Steve Chavez wrote:
> However, defining placeholders at the role level require superuser:
>
> alter role myrole set my.username to 'tomas';
> ERROR: permission denied to set parameter "my.username"
>
> Which is inconsistent and surprising behavior. I think it doesn't make
> sense since you can already set them at the session or transaction
> level(SET LOCAL my.username = 'tomas'). Enabling this would allow sidecar
> services to store metadata scoped to its pertaining role.
>
> I've attached a patch that removes this restriction. From my testing, this
> doesn't affect permission checking when an extension defines its custom GUC
> variables.
>
> DefineCustomStringVariable("my.custom", NULL, NULL, &my_custom, NULL,
> PGC_SUSET, ..);
>
> Using PGC_SUSET or PGC_SIGHUP will fail accordingly. Also no tests fail
> when doing "make installcheck".

IIUC you are basically proposing to revert a6dcd19 [0], but it is not clear
to me why that is safe. Am I missing something?

[0] https://www.postgresql.org/message-id/flat/4090.1258042387%40sss.pgh.pa.us

--
Nathan Bossart
Amazon Web Services: https://aws.amazon.com