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 thouhg the 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 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 functionAm 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 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 ?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 nameThe 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 requires SELECT permissions due to "ON CONFLICT" (appuser was previously only granted INSERT and UPDATE).