Horton

Re: Possibility to disable `ALTER SYSTEM`

Tom Lane <tgl@sss.pgh.pa.us>

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From: Tom Lane <tgl@sss.pgh.pa.us>
To: Heikki Linnakangas <hlinnaka@iki.fi>
Cc: PostgreSQL Hackers <pgsql-hackers@postgresql.org>, Jelte Fennema-Nio <postgres@jeltef.nl>, Daniel Gustafsson <daniel@yesql.se>, Bruce Momjian <bruce@momjian.us>, Joel Jacobson <joel@compiler.org>, Andrew Dunstan <andrew@dunslane.net>, Gabriele Bartolini <gabriele.bartolini@enterprisedb.com>, Magnus Hagander <magnus.hagander@redpill-linpro.com>, Maciek Sakrejda <m.sakrejda@gmail.com>, Robert Haas <robertmhaas@gmail.com>
Date: 2024-03-19T14:51:50Z
Lists: pgsql-hackers

Commits

Same data as JSON: GET /api/v1/messages/:b64id/commits the thread's linked commits as JSON, with link sources. API reference →

  1. Add allow_alter_system GUC.

  2. Rename COMPAT_OPTIONS_CLIENT to COMPAT_OPTIONS_OTHER.

  3. Remove support for version-0 calling conventions.

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?

Another question is whether this should be one-size-fits-all for
all the configuration files.  I can imagine situations where
you'd like to lock down postgresql[.auto].conf but not pg_hba.conf.
But maybe that can wait for somebody to show up with a use-case.

			regards, tom lane