pg_dump does not handle indirectly-granted permissions properly

From: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>
To: Stephen Frost <sfrost(at)snowman(dot)net>
Cc: pgsql-hackers(at)postgreSQL(dot)org
Subject: pg_dump does not handle indirectly-granted permissions properly
Date: 2017-07-25 20:42:45
Message-ID: 16996.1501015365@sss.pgh.pa.us
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AFAICT, pg_dump has no notion that it needs to be careful about the order
in which permissions are granted. I did

regression=# create user joe;
CREATE ROLE
regression=# create user bob;
CREATE ROLE
regression=# create user alice;
CREATE ROLE
regression=# \c - joe
You are now connected to database "regression" as user "joe".
regression=> create table joestable(f1 int);
CREATE TABLE
regression=> grant select on joestable to alice with grant option;
GRANT
regression=> \c - alice
You are now connected to database "regression" as user "alice".
regression=> grant select on joestable to bob;
GRANT

and then pg_dump'd that. The ACL entry for joestable looks like this:

--
-- TOC entry 5642 (class 0 OID 0)
-- Dependencies: 606
-- Name: joestable; Type: ACL; Schema: public; Owner: joe
--

SET SESSION AUTHORIZATION alice;
GRANT SELECT ON TABLE joestable TO bob;
RESET SESSION AUTHORIZATION;
GRANT SELECT ON TABLE joestable TO alice WITH GRANT OPTION;

Unsurprisingly, that fails to restore:

db2=# SET SESSION AUTHORIZATION alice;
SET
db2=> GRANT SELECT ON TABLE joestable TO bob;
ERROR: permission denied for relation joestable

I am not certain whether this is a newly introduced bug or not.
However, I tried it in 9.2-9.6, and all of them produce the
GRANTs in the right order:

GRANT SELECT ON TABLE joestable TO alice WITH GRANT OPTION;
SET SESSION AUTHORIZATION alice;
GRANT SELECT ON TABLE joestable TO bob;
RESET SESSION AUTHORIZATION;

That might be just chance, but my current bet is that Stephen
broke it sometime in the v10 cycle --- especially since we
haven't heard any complaints like this from the field.

regards, tom lane

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