Re: sepgsql contrib module

On Fri, Jan 21, 2011 at 11:00 AM, Kohei KaiGai <kaigai@kaigai.gr.jp> wrote:
> 2011/1/22 Robert Haas <robertmhaas@gmail.com>:
>> On Fri, Jan 21, 2011 at 10:46 AM, Tom Lane <tgl@sss.pgh.pa.us> wrote:
>>> Robert Haas <robertmhaas@gmail.com> writes:
>>>> On Fri, Jan 21, 2011 at 9:55 AM, Tom Lane <tgl@sss.pgh.pa.us> wrote:
>>>>> ALTER FUNCTION is supposed to cause plan invalidation in such a case.
>>>>> Not sure if GRANT plays nice with that though.
>>>
>>>> And in the case of SE-Linux, this could get changed from outside the
>>>> database.  Not sure how to handle that.  I guess we could just never
>>>> inline anything, but that might be an overreaction.
>>>
>>> I think SELinux is just out of luck in that case.  If it didn't refuse
>>> execution permission at the time we checked before inlining (which we
>>> do), it doesn't get to change its mind later.
>>
>> Seems reasonable to me, if it works for KaiGai.
>>
> I assume users of SE-PostgreSQL put their first priority on security,
> not best-performance. So, I also think it is reasonable to kill a part of
> optimization for the strict security checks.
>
> Here is one request for the hook.
> needs_fmgr_hook() is called by fmgr_info_cxt_security() and routines
> to inline. I need a flag to distinct these cases, because we don't need
> to invoke all the functions via fmgr_security_definer(), even if it never
> allows to inline.

I don't want to go there, and it's not what Tom was proposing anyway.
The idea is - if the user creates a function which is NOT a trusted
procedure and executes it, and then subsequently changes the system
security policy so that it becomes a trusted procedure, the user will
be responsible for flushing the cached plans before the new value will
take effect.  That doesn't require nearly as much de-optimization, and
I don't believe it is a serious issue from a security perspective,
either.  (Note that the reverse case, where a trusted procedure is
demoted to a non-trusted procedure, isn't an issue, because we will
have suppressed inlining and the new execution will follow the right
rules, just with reduced performance.)

-- 
Robert Haas
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