Re: Session Identifiers

2015-12-20 19:08 GMT+01:00 Dmitry Igrishin <dmitigr(at)gmail(dot)com>:

>
>
> 2015-12-20 21:00 GMT+03:00 Pavel Stehule <pavel(dot)stehule(at)gmail(dot)com>:
>
>>
>>
>> 2015-12-20 18:56 GMT+01:00 Dmitry Igrishin <dmitigr(at)gmail(dot)com>:
>>
>>>
>>>
>>> 2015-12-20 19:44 GMT+03:00 Pavel Stehule <pavel(dot)stehule(at)gmail(dot)com>:
>>>
>>>>
>>>>
>>>> 2015-12-20 17:30 GMT+01:00 Dmitry Igrishin <dmitigr(at)gmail(dot)com>:
>>>>
>>>>> Can be totally different if you use some connection pooler like pgpool
>>>>>> or pgbouncer - these applications can reuse Postgres server sessions for
>>>>>> more user sessions.
>>>>>>
>>>>> BTW, AFAIK, it's not possible to change the session authentication
>>>>> information by
>>>>> using SET SESSION AUTHORIZATION [1] if the current user is not a
>>>>> superuser.
>>>>> But it would be very nice to have a feature to change the session
>>>>> authorization
>>>>> of current user even without superuser's privilege by supplying a
>>>>> password of
>>>>> the user specified in SET SESSION AUTHORIZATION. This feature allows
>>>>> to use PostgreSQL's native privileges via connection pools -- i.e.
>>>>> without
>>>>> needs to open a dedicated connection for authenticated user. Is it
>>>>> possible
>>>>> to implement it?
>>>>>
>>>>
>>>> there is a workaround with security definer function and SET role TO ?
>>>>
>>> No there isn't. According to [2] "SET ROLE cannot be used within SECURITY
>>> DEFINER function". Furthermore, SET ROLE doesn't affects the
>>> session_user's
>>> function result which can be used by a logic.
>>>
>>
>> you want to modify result of session_user? It's looks like possible
>> security issue to me.
>>
> I want to be able to change the session user without creating the new
> connection, like this
> (pseudo REPL):
> notsuperuser > SELECT current_user, session_user;
> notsuperuser notsuperuser
> notsuperuser > SET SESSION AUTHORIZATION notsuperuser2 PASSWORD
> 'password_of_notsuperuser2';
> SET SESSION AUTHORIZATION
> notsuperuser2 > SELECT current_user, session_user;
> notsuperuser2 notsuperuser2
>
> I don't see any security issue here.
>

It needs a change in PGPROC - and maybe invalidation some memory
structures. I don't know why it is limited to superuser only.

Pavel

>
>
>> postgres=# create role tom ;
>> CREATE ROLE
>> Time: 91.461 ms
>> postgres=# select current_user;
>> ┌──────────────┐
>> │ current_user │
>> ╞══════════════╡
>> │ pavel │
>> └──────────────┘
>> (1 row)
>>
>> Time: 15.692 ms
>> postgres=# set role tom;
>> SET
>> Time: 0.609 ms
>> postgres=> select current_user;
>> ┌──────────────┐
>> │ current_user │
>> ╞══════════════╡
>> │ tom │
>> └──────────────┘
>> (1 row)
>>
>>
>>
>>
>>>
>>> [2] http://www.postgresql.org/docs/9.4/static/sql-set-role.html
>>>
>>> --
>>> // Dmitry.
>>>
>>>
>>
>
>
> --
> // Dmitry.
>
>