Re: Review of Row Level Security

2012/12/9 Simon Riggs <simon(at)2ndquadrant(dot)com>:
> On 9 December 2012 06:08, Kohei KaiGai <kaigai(at)kaigai(dot)gr(dot)jp> wrote:
>> 2012/12/7 Simon Riggs <simon(at)2ndquadrant(dot)com>:
>>> On 5 December 2012 11:16, Kohei KaiGai <kaigai(at)kaigai(dot)gr(dot)jp> wrote:
>>>
>>>>> * TRUNCATE works, and allows you to remove all rows of a table, even
>>>>> ones you can't see to run a DELETE on. Er...
>>>>>
>>>> It was my oversight. My preference is to rewrite TRUNCATE command
>>>> with DELETE statement in case when row-security policy is active on
>>>> the target table.
>>>> In this case, a NOTICE message may be helpful for users not to assume
>>>> the table is always empty after the command.
>>>
>>> I think the default must be to throw an ERROR, since part of the
>>> contract with TRUNCATE is that it is fast and removes storage.
>>>
>> OK. Does the default imply you are suggesting configurable
>> behavior using GUC or something?
>> I think both of the behaviors are reasonable from security point
>> of view, as long as user cannot remove unprivileged rows.
>
> Hmm, its difficult one that. I guess this raises the question as to
> whether users know they are accessing a table with RLS enabled. If
> they don't and we want to keep it that way, then changing TRUNCATE
> into DELETE makes sense.
>
> To issue TRUNCATE you need the correct privilege, which is separate from DELETE.
>
> If they have TRUNCATE privilege they should be allowed to remove all
> rows, bypassing the row level security.
>
> If that behavious isn't wanted, then the table owner can create an
> INSTEAD OF TRUNCATE trigger that turns the action into a DELETE, which
> is then subject to RLS rules.
>
It seems to me make sense, also.
Even though selinux does not define separated permissions for TRUNCATE,
the later option will work well for me in case of row-level label based security
is configured in the future version.
So, I don't implement something special around TRUNCATE, except for
paying mention at the documentation.

Thanks,
--
KaiGai Kohei <kaigai(at)kaigai(dot)gr(dot)jp>