Message-ID: <4AD83EC6.2080800@enterprisedb.com>
Date: Fri, 16 Oct 2009 12:37:10 +0300
From: Heikki Linnakangas <heikki.linnakangas@enterprisedb.com>
Organization: EnterpriseDB
User-Agent: Mozilla-Thunderbird 2.0.0.22 (X11/20090706)
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To: KaiGai Kohei <kaigai@ak.jp.nec.com>
CC: Tom Lane <tgl@sss.pgh.pa.us>, Stephen Frost <sfrost@snowman.net>,
	robertmhaas@gmail.com, pgsql-hackers@postgresql.org, kaigai@kaigai.gr.jp
Subject: Re: Reworks for Access Control facilities (r2363)
References: <4AC5A14F.6050306@ak.jp.nec.com>
	<20091012024604.GW17756@tamriel.snowman.net>
	<4AD54082.9050001@ak.jp.nec.com> <10495.1255627322@sss.pgh.pa.us>
	<4AD7CCDD.1070402@ak.jp.nec.com>
In-Reply-To: <4AD7CCDD.1070402@ak.jp.nec.com>
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KaiGai Kohei wrote:
> The purpose of this patch is to provide function entrypoints for the
> upcoming SE-PostgreSQL feature, because I got a few comments that we
> hesitate to put sepgsql_xxx() hooks on the main routines directly in
> the first commit fest. In addition, I already tried to put SE-PG hooks
> within pg_xxx_aclchecks() in this CF, but it was failed due to the
> differences in the security models.

Can you elaborate that? It might well be that you need to adapt the
SE-PostgreSQL security model to the one that's there already. Putting
SE-PG hooks into existing pg_xxx_aclcheck functions is the only
low-impact way I can see to implement SE-PostgreSQL.

>> * There are two special-purpose shims, ac_database_calculate_size and
>> ac_tablespace_calculate_size, that got added for the benefit of
>> utils/adt/dbsize.c.  What if that code were still in contrib?  How is it
>> different from a lot of the code that is in contrib now, eg dblink or
>> pgrowlocks, to say nothing of third-party modules?  Presuming that the
>> shim layer can know explicitly about each individual permission-checking
>> requirement is a dead-end design.
> 
> Back to the definition of access controls (or reference monitor).
> It prevents violated accesses launched by user's requests (SQL).
> It is not a job to protect something from malicious internal modules.

The issue isn't malicious modules, but modules that have pg_xxx_aclcheck
calls in them and haven't been modified to do SE-pgsql checks like you
modified all the backend code. As the patch stands, they would perform
just the regular acl checks and bypass SE-pgsql.

-- 
  Heikki Linnakangas
  EnterpriseDB   http://www.enterprisedb.com