Re: Recursive row level security policy

Hello Simon

> -----Original Message-----
> From: pgsql-general-owner(at)postgresql(dot)org [mailto:pgsql-general-owner(at)postgresql(dot)org] On Behalf Of Simon Charette
> Sent: Freitag, 16. Dezember 2016 07:02
> To: Charles Clavadetscher <clavadetscher(at)swisspug(dot)org>
> Cc: pgsql-general(at)postgresql(dot)org
> Subject: Re: [GENERAL] Recursive row level security policy
>
> Hello Charles,
>
> Unfortunately this will only return accounts matching the current_user's name.
>
> I would expect "SET ROLE foo; SELECT name FROM accounts" to return "foo" and "bar" and not only "foo" like your
> proposed solution would do.

True. I did oversee the real target.

The problem is that the policy for select on the table will be cheked each time a select is performed. So having a select in the using condition will check the policy again, and so on.

I am not sure how to solve this with policies and I assume that somebody else may come up with an idea. One thing I can think of is to check the condition in a security definer function where you temporarily disable row level security. But this is quite a nasty thing to do...

A workaround would be the "old way" using views:

CREATE VIEW public.v_accounts AS
SELECT * FROM accounts
WHERE owner_id = (SELECT owner_id FROM accounts WHERE name = CURRENT_USER);

REVOKE SELECT ON accounts FROM public;
GRANT SELECT ON v_accounts TO public;

charles(at)charles=# set role foo;
SET

charles(at)charles=> SELECT * FROM accounts;
ERROR: permission denied for relation accounts

charles(at)charles=> select * from v_accounts ;
id | name | owner_id
----+------+----------
1 | foo | 1
2 | bar | 1
(2 rows)

Instead of granting select on the table you only grant it on the view.

Hope this helps.
Bye
Charles

>
> Simon
>
> 2016-12-16 0:57 GMT-05:00 Charles Clavadetscher <clavadetscher(at)swisspug(dot)org>:
> > Hello
> >
> >> -----Original Message-----
> >> From: pgsql-general-owner(at)postgresql(dot)org
> >> [mailto:pgsql-general-owner(at)postgresql(dot)org] On Behalf Of Simon
> >> Charette
> >> Sent: Freitag, 16. Dezember 2016 06:15
> >> To: pgsql-general(at)postgresql(dot)org
> >> Subject: [GENERAL] Recursive row level security policy
> >>
> >> Hello there,
> >>
> >> I'm not sure I'm posting to the appropriate mailing list so don't hesitate to redirect me to the appropriate one.
> >>
> >> I've been trying to setup a policy that allows "accounts" table rows
> >> to only be seen by their owner by using the current_user to compare them by name.
> >>
> >> Unfortunately it looks like I'm either missing something or there's a
> >> limitation in the current row level security implementation that prevents me from doing this.
> >>
> >> Here's the actual SQL to reproduce the issue:
> >>
> >> CREATE TABLE "accounts" (
> >> "id" integer NOT NULL PRIMARY KEY,
> >> "name" varchar(50) NOT NULL UNIQUE,
> >> "owner_id" integer NOT NULL
> >> );
> >>
> >> INSERT INTO accounts(id, name, owner_id)
> >> VALUES (1, 'foo', 1), (2, 'bar', 1), (3, 'baz', 3);
> >>
> >> GRANT SELECT ON accounts TO PUBLIC;
> >>
> >> ALTER TABLE accounts ENABLE ROW LEVEL SECURITY;
> >>
> >> CREATE POLICY account_ownership ON accounts FOR SELECT
> >> USING (owner_id = (SELECT id FROM accounts WHERE name =
> >> current_user));
> >
> > I think that should be:
> >
> > CREATE POLICY account_ownership ON accounts FOR SELECT
> > USING (name = current_user);
> >
> > Regards
> > Charles
> >
> >>
> >> CREATE ROLE foo;
> >> SET ROLE foo;
> >> SELECT * FROM accounts;
> >> -- ERROR: infinite recursion detected in policy for relation "accounts"
> >>
> >> Is there any way to alter the "account_ownership" policy's USING
> >> clause to avoid this infinite recursion or a way to model my schema to prevent this from happening?
> >>
> >> Thank you for your time,
> >> Simon
> >>
> >>
> >> --
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> >
>
>
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