Thread: Postgres 12 RLS
Hi,
I'm having a little trouble with RLS in Postgres 12, although first time I've used RLS, so it might just be me !
The problem is that I am calling a function from a web-app, but the function seems to be executing as "postgres" even
thouhgthe web-app logs in as a completely different role ?
This means that current_user in the function resolves to "postgres" instead of the app user.
This is an example of a function :
create function addses(p_regid text,p_msgid text,p_reqid text) returns integer AS $$
BEGIN
UPDATE foo_regs set reg_aws_ses_msgid=p_msgid,reg_aws_amzn_requestid=p_reqid where uuid=p_regid;
IF FOUND THEN
return 1;
ELSE
return 0;
END IF;
END;
$$ LANGUAGE plpgsql SECURITY DEFINER;
grant execute on function addses(p_regid text,p_msgid text,p_reqid text) to myappuser;
The foo_regs table has the following RLS policy:
Policies:
POLICY "foo_regs_policy"
USING (((event_id = CURRENT_USER) AND (reg_hide IS FALSE)))
Hi Laura, > On 08. Jun, 2020, at 12:17, Laura Smith <n5d9xq3ti233xiyif2vp@protonmail.ch> $$ LANGUAGE plpgsql SECURITY DEFINER; you might want to use security invoker instead of definer. https://www.postgresql.org/docs/current/sql-createfunction.html#SQL-CREATEFUNCTION-SECURITY https://www.cybertec-postgresql.com/en/abusing-security-definer-functions/ Cheers, Paul
On Monday, 8 June 2020 11:25, Paul Förster <paul.foerster@gmail.com> wrote: > Hi Laura, > > > On 08. Jun, 2020, at 12:17, Laura Smith n5d9xq3ti233xiyif2vp@protonmail.ch $$ LANGUAGE plpgsql SECURITY DEFINER; > > you might want to use security invoker instead of definer. > > https://www.postgresql.org/docs/current/sql-createfunction.html#SQL-CREATEFUNCTION-SECURITY > > https://www.cybertec-postgresql.com/en/abusing-security-definer-functions/ > > Cheers, > Paul Hi Paul, I had a lightbulb moment just now and tried that, but it doesn't seem to be working. The app returns "pg_execute(): Query failed: ERROR: permission denied for table...." This is despite me: • Changing to SECURITY INVOKER on the PG function. • Granting the app user relevant perms on the underlying table • Re-granting execute for the app on the function Am I missing somehthing ?
Hi Laura, > On 08. Jun, 2020, at 12:46, Laura Smith <n5d9xq3ti233xiyif2vp@protonmail.ch> I had a lightbulb moment just now and triedthat, but it doesn't seem to be working. > > The app returns "pg_execute(): Query failed: ERROR: permission denied for table...." > > This is despite me: > • Changing to SECURITY INVOKER on the PG function. > • Granting the app user relevant perms on the underlying table > • Re-granting execute for the app on the function > > Am I missing somehthing ? another possibility maybe is to use session_user instead of current_user in your policy. current_user name user name of current execution context session_user name session user name The latter is the name of the user who actually started the session. So it should be myappuser in your case. https://www.postgresql.org/docs/current/functions-info.html Cheers, Paul
On Monday, 8 June 2020 12:42, Paul Förster <paul.foerster@gmail.com> wrote: > Hi Laura, > > > On 08. Jun, 2020, at 12:46, Laura Smith n5d9xq3ti233xiyif2vp@protonmail.ch I had a lightbulb moment just now and triedthat, but it doesn't seem to be working. > > The app returns "pg_execute(): Query failed: ERROR: permission denied for table...." > > This is despite me: > > • Changing to SECURITY INVOKER on the PG function. > > • Granting the app user relevant perms on the underlying table > > • Re-granting execute for the app on the function > > Am I missing somehthing ? > > another possibility maybe is to use session_user instead of current_user in your policy. > > current_user name user name of current execution context > session_user name session user name > > The latter is the name of the user who actually started the session. So it should be myappuser in your case. > > https://www.postgresql.org/docs/current/functions-info.html > > Cheers, > Paul Thanks Paul, will experiment with session_user. But actually I found the solution, the function I was testing was using "INSERT ON CONFLICT UPDATE". And it seems that requiresSELECT permissions due to "ON CONFLICT" (appuser was previously only granted INSERT and UPDATE).