Re: exposing pg_controldata and pg_config as functions

From: Joe Conway <mail(at)joeconway(dot)com>
To: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>, Andrew Dunstan <andrew(at)dunslane(dot)net>
Cc: Michael Paquier <michael(dot)paquier(at)gmail(dot)com>, PostgreSQL-development <pgsql-hackers(at)postgresql(dot)org>
Subject: Re: exposing pg_controldata and pg_config as functions
Date: 2015-08-26 03:32:55
Message-ID: 55DD3367.6070802@joeconway.com
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On 08/24/2015 08:52 AM, Joe Conway wrote:
> On 08/24/2015 06:50 AM, Tom Lane wrote:
>> Andrew Dunstan <andrew(at)dunslane(dot)net> writes:
>>> On 08/23/2015 08:58 PM, Michael Paquier wrote:
>>>> I think that's a good thing to have, now I have concerns
>>>> about making this data readable for non-superusers. Cloud
>>>> deployments of Postgres are logically going to block the
>>>> access of this view.
>
>>> I don't think it exposes any information of great security
>>> value.
>
>> We just had that kerfuffle about whether WAL compression posed a
>> security risk; doesn't that imply that at least the data
>> relevant to WAL position has to be unreadable by non-superusers?
>
> So pg_config might be fully unrestricted, but pg_controldata might
> need certain rows filtered based on superuser status? Do you think
> those rows should be present but redacted, or completely filtered
> out?

Here is the next installment on this. It addresses most of the
previous comments, but does not yet address the issue raised here by Tom
.

Changes:
1.) pg_controldata() function and pg_controldata view added

2.) cleanup_path() moved to port/path.c

3.) extra PG_FUNCTION_INFO_V1() noise removed

Issues needing comment:
a.) Which items need hiding from non-superusers and should the value be
redacted or the entire result set row be suppressed?

b.) There is a difference in the formatting of timestamps between the
pg_controldata binary and the builtin function. To see it do:

diff -c <(pg_controldata) \
<(psql -qAt -c "select rpad(name || ':', 38) || setting
from pg_controldata")

What I see is:

pg_controldata
! pg_control last modified: Tue 25 Aug 2015 08:10:42 PM PDT
pg_controldata()
! pg_control last modified: Tue Aug 25 20:10:42 2015

Does it matter?

c.) There is some common code between pg_controldata.c in bin and
pg_controldata.c in backend/utils/misc. Specifically the string
definitions in printf statements match those in ControlData[], and
dbState() and wal_level_str() are in both places. Any opinions
on consolidating them in src/common somewhere?

d.) Still no docs yet - will get to it eventually.

Thanks,

Joe

- --
Crunchy Data - http://crunchydata.com
PostgreSQL Support for Secure Enterprises
Consulting, Training, & Open Source Development
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Attachment Content-Type Size
2015082503-pgconfig_controldata.diff text/x-diff 33.2 KB

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