setting extra_pg_conf="log_file_mode=0600" results in a traceback

[Chris Johnston]

As per PostgreSQL 9.x STIG V-214152 [1], log_file_mode must be configured to 0600.

When trying to do this via `juju config landscape-postgresql extra_pg_conf="log_file_mode=0600"` it results in the following error:

2022-01-03 20:05:46 WARNING config-changed Traceback (most recent call last):
2022-01-03 20:05:46 WARNING config-changed File "/var/lib/juju/agents/unit-landscape-postgresql-1/charm/hooks/config-changed", line 22, in <module>
2022-01-03 20:05:46 WARNING config-changed main()
2022-01-03 20:05:46 WARNING config-changed File "/var/lib/juju/agents/unit-landscape-postgresql-1/.venv/lib/python3.6/site-packages/charms/reactive/__init__.py", line 74, in main
2022-01-03 20:05:46 WARNING config-changed bus.dispatch(restricted=restricted_mode)
2022-01-03 20:05:46 WARNING config-changed File "/var/lib/juju/agents/unit-landscape-postgresql-1/.venv/lib/python3.6/site-packages/charms/reactive/bus.py", line 390, in dispatch
2022-01-03 20:05:46 WARNING config-changed _invoke(other_handlers)
2022-01-03 20:05:46 WARNING config-changed File "/var/lib/juju/agents/unit-landscape-postgresql-1/.venv/lib/python3.6/site-packages/charms/reactive/bus.py", line 359, in _invoke
2022-01-03 20:05:46 WARNING config-changed handler.invoke()
2022-01-03 20:05:46 WARNING config-changed File "/var/lib/juju/agents/unit-landscape-postgresql-1/.venv/lib/python3.6/site-packages/charms/reactive/bus.py", line 181, in invoke
2022-01-03 20:05:46 WARNING config-changed self._action(*args)
2022-01-03 20:05:46 WARNING config-changed File "/var/lib/juju/agents/unit-landscape-postgresql-1/charm/reactive/postgresql/service.py", line 246, in configure_cluster
2022-01-03 20:05:46 WARNING config-changed update_postgresql_conf()
2022-01-03 20:05:46 WARNING config-changed File "/var/lib/juju/agents/unit-landscape-postgresql-1/charm/reactive/postgresql/service.py", line 820, in update_postgresql_conf
2022-01-03 20:05:46 WARNING config-changed settings = assemble_postgresql_conf()
2022-01-03 20:05:46 WARNING config-changed File "/var/lib/juju/agents/unit-landscape-postgresql-1/charm/reactive/postgresql/service.py", line 558, in assemble_postgresql_conf
2022-01-03 20:05:46 WARNING config-changed validate_postgresql_conf(conf) # May terminate.
2022-01-03 20:05:46 WARNING config-changed File "/var/lib/juju/agents/unit-landscape-postgresql-1/charm/reactive/postgresql/service.py", line 813, in validate_postgresql_conf
2022-01-03 20:05:46 WARNING config-changed raise ValueError("{} above maximum {}".format(v, r.maxvalue))
2022-01-03 20:05:46 WARNING config-changed AttributeError: 'pg_settings' object has no attribute 'maxvalue'
2022-01-03 20:05:46 ERROR juju.worker.uniter.operation runhook.go:136 hook "config-changed" (via explicit, bespoke hook script) failed: exit status 1

Looking into this validate_postgresql_conf, I see that the min/max for this config option is 0/511 [2]. To validate that this isn't something related to the charm at all, I have installed postgresql-10 on a 18.04 VM and ran:

`sudo runuser -u postgres -- psql -c "SELECT name, unit, context, vartype, min_val, max_val, enumvals, boot_val FROM pg_settings WHERE context <> 'internal';`

which results in:

log_file_mode | | sighup | integer | 0 | 511 | | 384

Confirming that the max value is 511. Upon reading the PostgreSQL documentation [3], I see that the default value for this field is 0600, though 0640 is also commonly used. While 0600 is the default, a user should still be able to hard code the default value, or the 0640 as mentioned in the documentation.

[1] https://www.stigviewer.com/stig/postgresql_9.x/2021-06-04/finding/V-214152
[2] https://git.launchpad.net/postgresql-charm/tree/lib/pg_settings_10.json#n1640
[3] https://www.postgresql.org/docs/10/runtime-config-logging.html#id-1.6.6.11.3.4.5.1.3

[Tom Haddon (mthaddon)]

Ok, so the issue here is that the value is specified as an octal (e.g. 0600) which corresponds to 384 as an integer (0600 = (0 × 8³) + (6 × 8²) + (0 × 8¹) + (0 × 8⁰) = 384). However, we're not converting from octal to integer before comparing in the code.

I think the follow up fix here should be to switch the "type" in the pg_settings json files to octal and then convert that appropriately in `validate_postgresql_conf`.

[Tom Haddon (mthaddon)]

This has been fixed in cs:postgresql-236. This change will also be propogated to charmhub within 24 hours.