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Re: almost-super-user problems that we haven't fixed yet

Nathan Bossart <nathandbossart@gmail.com>

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From: Nathan Bossart <nathandbossart@gmail.com>
To: Robert Haas <robertmhaas@gmail.com>
Cc: "pgsql-hackers@postgresql.org" <pgsql-hackers@postgresql.org>
Date: 2023-01-18T00:15:23Z
Lists: pgsql-hackers

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On Tue, Jan 17, 2023 at 02:59:31PM -0500, Robert Haas wrote:
> On Tue, Jan 17, 2023 at 1:42 PM Nathan Bossart <nathandbossart@gmail.com> wrote:
>> If we create a new batch of reserved connections, only roles with
>> privileges of pg_use_reserved_connections would be able to connect if the
>> number of remaining slots is greater than superuser_reserved_connections
>> but less than or equal to superuser_reserved_connections +
>> reserved_connections.  Only superusers would be able to connect if the
>> number of remaining slots is less than or equal to
>> superuser_reserved_connections.  This helps avoid blocking new superuser
>> connections even if you've reserved some connections for non-superusers.
> 
> This is precisely what I had in mind.

Great.  Here is a first attempt at the patch.

> I think the documentation will need some careful wordsmithing,
> including adjustments to superuser_reserved_connections. We want to
> recast superuser_reserved_connections as a final reserve to be touched
> after even reserved_connections has been exhausted.

I tried to do this, but there is probably still room for improvement,
especially for the parts that discuss the relationship between
max_connections, superuser_reserved_connections, and reserved_connections.

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

Commits

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

  1. Improve several permission-related error messages.

  2. Integrate superuser check into has_rolreplication()

  3. Small code simplification

  4. Adjust interaction of CREATEROLE with role properties.

  5. Add new GUC reserved_connections.

  6. Rename ReservedBackends variable to SuperuserReservedConnections.

  7. Update docs and error message for superuser_reserved_connections.

  8. Add new GUC createrole_self_grant.

  9. Restrict the privileges of CREATEROLE users.

  10. Add a SET option to the GRANT command.