Re: Session Identifiers

[Pavel Stehule <pavel.stehule@xxxxxxxxx>]

2015-12-20 19:08 GMT+01:00 Dmitry Igrishin <dmitigr@xxxxxxxxx>:

2015-12-20 21:00 GMT+03:00 Pavel Stehule <pavel.stehule@xxxxxxxxx>:

2015-12-20 18:56 GMT+01:00 Dmitry Igrishin <dmitigr@xxxxxxxxx>:

2015-12-20 19:44 GMT+03:00 Pavel Stehule <pavel.stehule@xxxxxxxxx>:

2015-12-20 17:30 GMT+01:00 Dmitry Igrishin <dmitigr@xxxxxxxxx>:

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.