Skip site navigation (1) Skip section navigation (2)

Re: [GENERAL] column-level update privs + lock table

From: KaiGai Kohei <kaigai(at)ak(dot)jp(dot)nec(dot)com>
To: Simon Riggs <simon(at)2ndQuadrant(dot)com>
Cc: Josh Kupershmidt <schmiddy(at)gmail(dot)com>, Robert Haas <robertmhaas(at)gmail(dot)com>, pgsql-hackers <pgsql-hackers(at)postgresql(dot)org>
Subject: Re: [GENERAL] column-level update privs + lock table
Date: 2010-12-01 03:59:46
Message-ID: 4CF5C832.8040000@ak.jp.nec.com (view raw or flat)
Thread:
Lists: pgsql-generalpgsql-hackers
(2010/11/30 21:26), Simon Riggs wrote:
> On Mon, 2010-11-29 at 21:37 -0500, Josh Kupershmidt wrote:
> 
>> I still see little reason to make LOCK TABLE permissions different for
>> column-level vs. table-level UPDATE privileges
> 
> Agreed.
> 
> This is the crux of the debate. Why should this inconsistency be allowed
> to continue?
> 
> Are there covert channel issues here, KaiGai?
> 
Existing database privilege mechanism (and SELinux, etc...) is not designed
to handle covert channel attacks, basically.
For example, if a user session with column-level UPDATE privilege tries
to update a certain column for each seconds depending on the contents of
other table X, other session can probably know the contents of table X
using iteration of LOCK command without SELECT permission.
It is a typical timing channel attack, but it is not a problem that we
should try to tackle, is it?

Sorry, I don't have a credible idea to solve this inconsistency right now.

Thanks,
-- 
KaiGai Kohei <kaigai(at)ak(dot)jp(dot)nec(dot)com>

In response to

pgsql-hackers by date

Next:From: Tom LaneDate: 2010-12-01 04:17:05
Subject: Re: We really ought to do something about O_DIRECT and data=journalled on ext4
Previous:From: Andy ColsonDate: 2010-12-01 03:36:54
Subject: unlogged tables

pgsql-general by date

Next:From: Greg SwisherDate: 2010-12-01 05:31:10
Subject: Warm Standby log filling up with "FATAL: the database system is starting up" entries
Previous:From: Vick KheraDate: 2010-12-01 00:52:14
Subject: Re: Pg_upgrade question

Privacy Policy | About PostgreSQL
Copyright © 1996-2014 The PostgreSQL Global Development Group