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Shore up ADMIN OPTION restrictions.
Granting a role without ADMIN OPTION is supposed to prevent the grantee from adding or removing members from the granted role. Issuing SET ROLE before the GRANT bypassed that, because the role itself had an implicit right to add or remove members. Plug that hole by recognizing that implicit right only when the session user matches the current role. Additionally, do not recognize it during a security-restricted operation or during execution of a SECURITY DEFINER function. The restriction on SECURITY DEFINER is not security-critical. However, it seems best for a user testing his own SECURITY DEFINER function to see the same behavior others will see. Back-patch to 8.4 (all supported versions). The SQL standards do not conflate roles and users as PostgreSQL does; only SQL roles have members, and only SQL users initiate sessions. An application using PostgreSQL users and roles as SQL users and roles will never attempt to grant membership in the role that is the session user, so the implicit right to add or remove members will never arise. The security impact was mostly that a role member could revoke access from others, contrary to the wishes of his own grantor. Unapproved role member additions are less notable, because the member can still largely achieve that by creating a view or a SECURITY DEFINER function. Reviewed by Andres Freund and Tom Lane. Reported, independently, by Jonas Sundman and Noah Misch. Security: CVE-2014-0060
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‎doc/src/sgml/ref/grant.sgml

Lines changed: 7 additions & 5 deletions
Original file line numberDiff line numberDiff line change
@@ -396,11 +396,13 @@ GRANT <replaceable class="PARAMETER">role_name</replaceable> [, ...] TO <replace
396396
<para>
397397
If <literal>WITH ADMIN OPTION</literal> is specified, the member can
398398
in turn grant membership in the role to others, and revoke membership
399-
in the role as well. Without the admin option, ordinary users cannot do
400-
that. However,
401-
database superusers can grant or revoke membership in any role to anyone.
402-
Roles having <literal>CREATEROLE</> privilege can grant or revoke
403-
membership in any role that is not a superuser.
399+
in the role as well. Without the admin option, ordinary users cannot
400+
do that. A role is not considered to hold <literal>WITH ADMIN
401+
OPTION</literal> on itself, but it may grant or revoke membership in
402+
itself from a database session where the session user matches the
403+
role. Database superusers can grant or revoke membership in any role
404+
to anyone. Roles having <literal>CREATEROLE</> privilege can grant
405+
or revoke membership in any role that is not a superuser.
404406
</para>
405407

406408
<para>

‎src/backend/commands/user.c

Lines changed: 10 additions & 1 deletion
Original file line numberDiff line numberDiff line change
@@ -1334,7 +1334,16 @@ AddRoleMems(const char *rolename, Oid roleid,
13341334
rolename)));
13351335
}
13361336

1337-
/* XXX not sure about this check */
1337+
/*
1338+
* The role membership grantor of record has little significance at
1339+
* present. Nonetheless, inasmuch as users might look to it for a crude
1340+
* audit trail, let only superusers impute the grant to a third party.
1341+
*
1342+
* Before lifting this restriction, give the member == role case of
1343+
* is_admin_of_role() a fresh look. Ensure that the current role cannot
1344+
* use an explicit grantor specification to take advantage of the session
1345+
* user's self-admin right.
1346+
*/
13381347
if (grantorId != GetUserId() && !superuser())
13391348
ereport(ERROR,
13401349
(errcode(ERRCODE_INSUFFICIENT_PRIVILEGE),

‎src/backend/utils/adt/acl.c

Lines changed: 40 additions & 10 deletions
Original file line numberDiff line numberDiff line change
@@ -4580,6 +4580,11 @@ pg_role_aclcheck(Oid role_oid, Oid roleid, AclMode mode)
45804580
{
45814581
if (mode & ACL_GRANT_OPTION_FOR(ACL_CREATE))
45824582
{
4583+
/*
4584+
* XXX For roleid == role_oid, is_admin_of_role() also examines the
4585+
* session and call stack. That suits two-argument pg_has_role(), but
4586+
* it gives the three-argument version a lamentable whimsy.
4587+
*/
45834588
if (is_admin_of_role(roleid, role_oid))
45844589
return ACLCHECK_OK;
45854590
}
@@ -4897,11 +4902,9 @@ is_member_of_role_nosuper(Oid member, Oid role)
48974902

48984903

48994904
/*
4900-
* Is member an admin of role (directly or indirectly)? That is, is it
4901-
* a member WITH ADMIN OPTION?
4902-
*
4903-
* We could cache the result as for is_member_of_role, but currently this
4904-
* is not used in any performance-critical paths, so we don't.
4905+
* Is member an admin of role? That is, is member the role itself (subject to
4906+
* restrictions below), a member (directly or indirectly) WITH ADMIN OPTION,
4907+
* or a superuser?
49054908
*/
49064909
bool
49074910
is_admin_of_role(Oid member, Oid role)
@@ -4910,14 +4913,41 @@ is_admin_of_role(Oid member, Oid role)
49104913
List *roles_list;
49114914
ListCell *l;
49124915

4913-
/* Fast path for simple case */
4914-
if (member == role)
4915-
return true;
4916-
4917-
/* Superusers have every privilege, so are part of every role */
49184916
if (superuser_arg(member))
49194917
return true;
49204918

4919+
if (member == role)
4920+
/*
4921+
* A role can admin itself when it matches the session user and we're
4922+
* outside any security-restricted operation, SECURITY DEFINER or
4923+
* similar context. SQL-standard roles cannot self-admin. However,
4924+
* SQL-standard users are distinct from roles, and they are not
4925+
* grantable like roles: PostgreSQL's role-user duality extends the
4926+
* standard. Checking for a session user match has the effect of
4927+
* letting a role self-admin only when it's conspicuously behaving
4928+
* like a user. Note that allowing self-admin under a mere SET ROLE
4929+
* would make WITH ADMIN OPTION largely irrelevant; any member could
4930+
* SET ROLE to issue the otherwise-forbidden command.
4931+
*
4932+
* Withholding self-admin in a security-restricted operation prevents
4933+
* object owners from harnessing the session user identity during
4934+
* administrative maintenance. Suppose Alice owns a database, has
4935+
* issued "GRANT alice TO bob", and runs a daily ANALYZE. Bob creates
4936+
* an alice-owned SECURITY DEFINER function that issues "REVOKE alice
4937+
* FROM carol". If he creates an expression index calling that
4938+
* function, Alice will attempt the REVOKE during each ANALYZE.
4939+
* Checking InSecurityRestrictedOperation() thwarts that attack.
4940+
*
4941+
* Withholding self-admin in SECURITY DEFINER functions makes their
4942+
* behavior independent of the calling user. There's no security or
4943+
* SQL-standard-conformance need for that restriction, though.
4944+
*
4945+
* A role cannot have actual WITH ADMIN OPTION on itself, because that
4946+
* would imply a membership loop. Therefore, we're done either way.
4947+
*/
4948+
return member == GetSessionUserId() &&
4949+
!InLocalUserIdChange() && !InSecurityRestrictedOperation();
4950+
49214951
/*
49224952
* Find all the roles that member is a member of, including multi-level
49234953
* recursion. We build a list in the same way that is_member_of_role does

‎src/test/regress/expected/privileges.out

Lines changed: 35 additions & 1 deletion
Original file line numberDiff line numberDiff line change
@@ -32,7 +32,7 @@ ALTER GROUP regressgroup1 ADD USER regressuser4;
3232
ALTER GROUP regressgroup2 ADD USER regressuser2; -- duplicate
3333
NOTICE: role "regressuser2" is already a member of role "regressgroup2"
3434
ALTER GROUP regressgroup2 DROP USER regressuser2;
35-
ALTER GROUP regressgroup2 ADD USER regressuser4;
35+
GRANT regressgroup2 TO regressuser4 WITH ADMIN OPTION;
3636
-- test owner privileges
3737
SET SESSION AUTHORIZATION regressuser1;
3838
SELECT session_user, current_user;
@@ -929,6 +929,40 @@ SELECT has_table_privilege('regressuser1', 'atest4', 'SELECT WITH GRANT OPTION')
929929
t
930930
(1 row)
931931

932+
-- Admin options
933+
SET SESSION AUTHORIZATION regressuser4;
934+
CREATE FUNCTION dogrant_ok() RETURNS void LANGUAGE sql SECURITY DEFINER AS
935+
'GRANT regressgroup2 TO regressuser5';
936+
GRANT regressgroup2 TO regressuser5; -- ok: had ADMIN OPTION
937+
SET ROLE regressgroup2;
938+
GRANT regressgroup2 TO regressuser5; -- fails: SET ROLE suspended privilege
939+
ERROR: must have admin option on role "regressgroup2"
940+
SET SESSION AUTHORIZATION regressuser1;
941+
GRANT regressgroup2 TO regressuser5; -- fails: no ADMIN OPTION
942+
ERROR: must have admin option on role "regressgroup2"
943+
SELECT dogrant_ok(); -- ok: SECURITY DEFINER conveys ADMIN
944+
NOTICE: role "regressuser5" is already a member of role "regressgroup2"
945+
CONTEXT: SQL function "dogrant_ok" statement 1
946+
dogrant_ok
947+
------------
948+
949+
(1 row)
950+
951+
SET ROLE regressgroup2;
952+
GRANT regressgroup2 TO regressuser5; -- fails: SET ROLE did not help
953+
ERROR: must have admin option on role "regressgroup2"
954+
SET SESSION AUTHORIZATION regressgroup2;
955+
GRANT regressgroup2 TO regressuser5; -- ok: a role can self-admin
956+
NOTICE: role "regressuser5" is already a member of role "regressgroup2"
957+
CREATE FUNCTION dogrant_fails() RETURNS void LANGUAGE sql SECURITY DEFINER AS
958+
'GRANT regressgroup2 TO regressuser5';
959+
SELECT dogrant_fails(); -- fails: no self-admin in SECURITY DEFINER
960+
ERROR: must have admin option on role "regressgroup2"
961+
CONTEXT: SQL function "dogrant_fails" statement 1
962+
DROP FUNCTION dogrant_fails();
963+
SET SESSION AUTHORIZATION regressuser4;
964+
DROP FUNCTION dogrant_ok();
965+
REVOKE regressgroup2 FROM regressuser5;
932966
-- has_sequence_privilege tests
933967
\c -
934968
CREATE SEQUENCE x_seq;

‎src/test/regress/sql/privileges.sql

Lines changed: 28 additions & 1 deletion
Original file line numberDiff line numberDiff line change
@@ -37,7 +37,7 @@ ALTER GROUP regressgroup1 ADD USER regressuser4;
3737

3838
ALTER GROUP regressgroup2 ADD USER regressuser2; -- duplicate
3939
ALTER GROUP regressgroup2 DROP USER regressuser2;
40-
ALTER GROUP regressgroup2 ADD USER regressuser4;
40+
GRANT regressgroup2 TO regressuser4 WITH ADMIN OPTION;
4141

4242
-- test owner privileges
4343

@@ -581,6 +581,33 @@ SELECT has_table_privilege('regressuser3', 'atest4', 'SELECT'); -- false
581581
SELECT has_table_privilege('regressuser1', 'atest4', 'SELECT WITH GRANT OPTION'); -- true
582582

583583

584+
-- Admin options
585+
586+
SET SESSION AUTHORIZATION regressuser4;
587+
CREATE FUNCTION dogrant_ok() RETURNS void LANGUAGE sql SECURITY DEFINER AS
588+
'GRANT regressgroup2 TO regressuser5';
589+
GRANT regressgroup2 TO regressuser5; -- ok: had ADMIN OPTION
590+
SET ROLE regressgroup2;
591+
GRANT regressgroup2 TO regressuser5; -- fails: SET ROLE suspended privilege
592+
593+
SET SESSION AUTHORIZATION regressuser1;
594+
GRANT regressgroup2 TO regressuser5; -- fails: no ADMIN OPTION
595+
SELECT dogrant_ok(); -- ok: SECURITY DEFINER conveys ADMIN
596+
SET ROLE regressgroup2;
597+
GRANT regressgroup2 TO regressuser5; -- fails: SET ROLE did not help
598+
599+
SET SESSION AUTHORIZATION regressgroup2;
600+
GRANT regressgroup2 TO regressuser5; -- ok: a role can self-admin
601+
CREATE FUNCTION dogrant_fails() RETURNS void LANGUAGE sql SECURITY DEFINER AS
602+
'GRANT regressgroup2 TO regressuser5';
603+
SELECT dogrant_fails(); -- fails: no self-admin in SECURITY DEFINER
604+
DROP FUNCTION dogrant_fails();
605+
606+
SET SESSION AUTHORIZATION regressuser4;
607+
DROP FUNCTION dogrant_ok();
608+
REVOKE regressgroup2 FROM regressuser5;
609+
610+
584611
-- has_sequence_privilege tests
585612
\c -
586613

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