Re: "set role" semantics - Mailing list pgsql-general

adrian.klaver@aklaver.com wrote:

david.g.johnston@gmail.com wrote:

bryn@yugabyte.com wrote:

Notice that I didn't grant "connect" on either of the databases, "d1" or "d2", to any of the roles, "clstr$mgr, "d1$mgr", or "d2$mgr".

You didn't have to since PUBLIC gets that privilege and you didn't revoke it.

https://www.postgresql.org/docs/current/ddl-priv.html

Revoking PUBLIC has been explained before to you (Bryn Llewellyn).

A quick search:

https://www.postgresql.org/message-id/2176817.1644613186@sss.pgh.pa.us

https://www.postgresql.org/message-id/CAKFQuwayij%3DAQRQxJhFuJ3Qejq3E-PfiBjJ9CoHx_L_46BEgXQ@mail.gmail.com

https://www.postgresql.org/message-id/CAKFQuwZVq-LerGMTN0E3_7MqhJwtuJuzf0GSnKG32mH_Qf24Zw@mail.gmail.com

Here's an extract from the script that I copied in my first email:

create database d1;
revoke all on database d1 from public;

create database d2;
revoke all on database d2 from public;

Didn't I do exactly what you both said that I failed to do?

*Summary*

My experiments (especially below) show that "set role" has special semantics that differ from starting a session from cold:

"set role" allows a role that lacks "connect" on some database to end up so that the "current_database()" shows that forbidden database.

My question still stands: where can I read the account of this? I'm also interested to know _why_ it was decided not to test for the "connect" privilege when "set role" is used.

*Detail*

I suppose that the script that I first showed you conflated too many separable notions. (My aim was to you show what my overall aim was). Here's a drastically cut down version. It still demonstrates the behavior that I asked about.

create role joe

  nosuperuser

  nocreaterole

  nocreatedb

  noreplication

  nobypassrls

  connection limit -1

  login password 'p';

create database d1;

revoke all on database d1 from public;

\c d1 postgres

set role joe;

select current_database()||' > '||session_user||' > '||current_user;

I'm still able to end up with "Joe" as the "current_user" and "d1" (to which Joe cannot connect) as the "current_database()".

I then did the sanity test that I should have shown you at the outset. (Sorry that I didn't do that.) I started a session from cold, running "psql" on a client machine where the server machine is called "u" (for Ubuntu) in my "/etc/hosts", thus:

psql -h u -p 5432 -d d1 -U joe

The connect attempt was rejected with the error that I expected: "User does not have CONNECT privilege".

I wondered if the fact that the "session_user" was "postgres" in my tests was significant. So I did a new test. (As ever, I started with a freshly created cluster to be sure that no earlier tests had left a trace.)

create role mary
  nosuperuser
  noinherit
  nocreaterole
  nocreatedb
  noreplication
  nobypassrls
  connection limit -1
  login password 'p';

create role joe
  nosuperuser
  noinherit
  nocreaterole
  nocreatedb
  noreplication
  nobypassrls
  connection limit -1
  login password 'p';

create database d1;
revoke all on database d1 from public;
grant connect on database d1 to mary;
grant joe to mary;

Then I did this on the client machine:

psql -h u -p 5432 -d d1 -U mary

set role joe;

Here, too, I ended up with "Joe" as the "current_user" and "d1" (to which Joe cannot connect) as the "current_database()".