From: Tom Lane <tgl@sss.pgh.pa.us>
To: Stephen Frost <sfrost@snowman.net>
cc: Josh Berkus <josh@agliodbs.com>, Kohei KaiGai <kaigai@kaigai.gr.jp>,
 "ktm@rice.edu" <ktm@rice.edu>, Alexander Korotkov <aekorotkov@gmail.com>,
 Oleg Bartunov <obartunov@gmail.com>, Greg Smith <greg@2ndquadrant.com>,
 PgHacker <pgsql-hackers@postgresql.org>
Subject: Re: [v9.4] row level security
In-reply-to: <20130830192729.GO2706@tamriel.snowman.net>
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 <CAPpHfdsgMrBnzu9um48O6kwY=_pRFuRrBrHqnA03fCAo8x3-Gg@mail.gmail.com>
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 <20130829142321.GA30496@aart.rice.edu>
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 <5220D832.7090104@agliodbs.com> <20130830192729.GO2706@tamriel.snowman.net>
Comments: In-reply-to Stephen Frost <sfrost@snowman.net>
 message dated "Fri, 30 Aug 2013 15:27:29 -0400"
Date: Fri, 30 Aug 2013 15:43:14 -0400
Message-ID: <16798.1377891794@sss.pgh.pa.us>
Precedence: bulk
Sender: pgsql-hackers-owner@postgresql.org

Stephen Frost <sfrost@snowman.net> writes:
> We have issues with covert channels even without RLS though and holding
> up RLS because it doesn't fix all the covert channels isn't sensible.

I think it's entirely sensible to question whether we should reject (not
"hold up") RLS if it has major covert-channel problems.

The scenario I'm worried about is where somebody says "hey, Postgres has
RLS now, I can rely on that to hide my sooper sekrit data from other users
in the same database", and later they have a security breach through some
covert-channel attack.  Are they going to blame themselves?  No, they're
gonna blame Postgres.  Or consider the case where some bozo publishes
a method for such an attack and uses it to badmouth us as insecure.

I don't think we need the headaches that will result from promising
(or at least appearing to promise) something we can't deliver.  Nor am
I convinced that we're really doing users any favors by providing such a
feature.  They'd be *far* better advised to put their critical data in a
separate database.

In short, "we can check some check-box" is a really, really bad reason
to accept a security-related feature.  If we're going to put up with
all the downsides of RLS, I want the end result to be something that's
actually secure, not something that gives the illusion of security.
And right now, I do not believe we can get past the illusion stage,
ever (certainly not in a release or two).

			regards, tom lane


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