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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
This commit is contained in:
Noah Misch 2014-02-17 09:33:31 -05:00
parent 0983315b1d
commit fea164a72a
5 changed files with 120 additions and 18 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

12
doc/src/sgml/ref/grant.sgml
View File

@ -395,11 +395,13 @@ GRANT <replaceable class="PARAMETER">role_name</replaceable> [, ...] TO <replace
<para>
If <literal>WITH ADMIN OPTION</literal> is specified, the member can
in turn grant membership in the role to others, and revoke membership
in the role as well. Without the admin option, ordinary users cannot do
that. However,
database superusers can grant or revoke membership in any role to anyone.
Roles having <literal>CREATEROLE</> privilege can grant or revoke
membership in any role that is not a superuser.
in the role as well. Without the admin option, ordinary users cannot
do that. A role is not considered to hold <literal>WITH ADMIN
OPTION</literal> on itself, but it may grant or revoke membership in
itself from a database session where the session user matches the
role. Database superusers can grant or revoke membership in any role
to anyone. Roles having <literal>CREATEROLE</> privilege can grant
or revoke membership in any role that is not a superuser.
</para>
<para>

11
src/backend/commands/user.c
View File

@ -1366,7 +1366,16 @@ AddRoleMems(const char *rolename, Oid roleid,
rolename)));
}
/* XXX not sure about this check */
/*
* The role membership grantor of record has little significance at
* present. Nonetheless, inasmuch as users might look to it for a crude
* audit trail, let only superusers impute the grant to a third party.
*
* Before lifting this restriction, give the member == role case of
* is_admin_of_role() a fresh look. Ensure that the current role cannot
* use an explicit grantor specification to take advantage of the session
* user's self-admin right.
*/
if (grantorId != GetUserId() && !superuser())
ereport(ERROR,
(errcode(ERRCODE_INSUFFICIENT_PRIVILEGE),

50
src/backend/utils/adt/acl.c
View File

@ -4582,6 +4582,11 @@ pg_role_aclcheck(Oid role_oid, Oid roleid, AclMode mode)
{
if (mode & ACL_GRANT_OPTION_FOR(ACL_CREATE))
{
/*
* XXX For roleid == role_oid, is_admin_of_role() also examines the
* session and call stack. That suits two-argument pg_has_role(), but
* it gives the three-argument version a lamentable whimsy.
*/
if (is_admin_of_role(roleid, role_oid))
return ACLCHECK_OK;
}
@ -4899,11 +4904,9 @@ is_member_of_role_nosuper(Oid member, Oid role)
/*
* Is member an admin of role (directly or indirectly)? That is, is it
* a member WITH ADMIN OPTION?
*
* We could cache the result as for is_member_of_role, but currently this
* is not used in any performance-critical paths, so we don't.
* Is member an admin of role? That is, is member the role itself (subject to
* restrictions below), a member (directly or indirectly) WITH ADMIN OPTION,
* or a superuser?
*/
bool
is_admin_of_role(Oid member, Oid role)
@ -4912,14 +4915,41 @@ is_admin_of_role(Oid member, Oid role)
List *roles_list;
ListCell *l;
/* Fast path for simple case */
if (member == role)
return true;
/* Superusers have every privilege, so are part of every role */
if (superuser_arg(member))
return true;
if (member == role)
/*
* A role can admin itself when it matches the session user and we're
* outside any security-restricted operation, SECURITY DEFINER or
* similar context. SQL-standard roles cannot self-admin. However,
* SQL-standard users are distinct from roles, and they are not
* grantable like roles: PostgreSQL's role-user duality extends the
* standard. Checking for a session user match has the effect of
* letting a role self-admin only when it's conspicuously behaving
* like a user. Note that allowing self-admin under a mere SET ROLE
* would make WITH ADMIN OPTION largely irrelevant; any member could
* SET ROLE to issue the otherwise-forbidden command.
*
* Withholding self-admin in a security-restricted operation prevents
* object owners from harnessing the session user identity during
* administrative maintenance. Suppose Alice owns a database, has
* issued "GRANT alice TO bob", and runs a daily ANALYZE. Bob creates
* an alice-owned SECURITY DEFINER function that issues "REVOKE alice
* FROM carol". If he creates an expression index calling that
* function, Alice will attempt the REVOKE during each ANALYZE.
* Checking InSecurityRestrictedOperation() thwarts that attack.
*
* Withholding self-admin in SECURITY DEFINER functions makes their
* behavior independent of the calling user. There's no security or
* SQL-standard-conformance need for that restriction, though.
*
* A role cannot have actual WITH ADMIN OPTION on itself, because that
* would imply a membership loop. Therefore, we're done either way.
*/
return member == GetSessionUserId() &&
!InLocalUserIdChange() && !InSecurityRestrictedOperation();
/*
* Find all the roles that member is a member of, including multi-level
* recursion. We build a list in the same way that is_member_of_role does

36
src/test/regress/expected/privileges.out
View File

@ -32,7 +32,7 @@ ALTER GROUP regressgroup1 ADD USER regressuser4;
ALTER GROUP regressgroup2 ADD USER regressuser2; -- duplicate
NOTICE: role "regressuser2" is already a member of role "regressgroup2"
ALTER GROUP regressgroup2 DROP USER regressuser2;
ALTER GROUP regressgroup2 ADD USER regressuser4;
GRANT regressgroup2 TO regressuser4 WITH ADMIN OPTION;
-- test owner privileges
SET SESSION AUTHORIZATION regressuser1;
SELECT session_user, current_user;
@ -948,6 +948,40 @@ SELECT has_table_privilege('regressuser1', 'atest4', 'SELECT WITH GRANT OPTION')
t
(1 row)
-- Admin options
SET SESSION AUTHORIZATION regressuser4;
CREATE FUNCTION dogrant_ok() RETURNS void LANGUAGE sql SECURITY DEFINER AS
'GRANT regressgroup2 TO regressuser5';
GRANT regressgroup2 TO regressuser5; -- ok: had ADMIN OPTION
SET ROLE regressgroup2;
GRANT regressgroup2 TO regressuser5; -- fails: SET ROLE suspended privilege
ERROR: must have admin option on role "regressgroup2"
SET SESSION AUTHORIZATION regressuser1;
GRANT regressgroup2 TO regressuser5; -- fails: no ADMIN OPTION
ERROR: must have admin option on role "regressgroup2"
SELECT dogrant_ok(); -- ok: SECURITY DEFINER conveys ADMIN
NOTICE: role "regressuser5" is already a member of role "regressgroup2"
CONTEXT: SQL function "dogrant_ok" statement 1
dogrant_ok
------------
(1 row)
SET ROLE regressgroup2;
GRANT regressgroup2 TO regressuser5; -- fails: SET ROLE did not help
ERROR: must have admin option on role "regressgroup2"
SET SESSION AUTHORIZATION regressgroup2;
GRANT regressgroup2 TO regressuser5; -- ok: a role can self-admin
NOTICE: role "regressuser5" is already a member of role "regressgroup2"
CREATE FUNCTION dogrant_fails() RETURNS void LANGUAGE sql SECURITY DEFINER AS
'GRANT regressgroup2 TO regressuser5';
SELECT dogrant_fails(); -- fails: no self-admin in SECURITY DEFINER
ERROR: must have admin option on role "regressgroup2"
CONTEXT: SQL function "dogrant_fails" statement 1
DROP FUNCTION dogrant_fails();
SET SESSION AUTHORIZATION regressuser4;
DROP FUNCTION dogrant_ok();
REVOKE regressgroup2 FROM regressuser5;
-- has_sequence_privilege tests
\c -
CREATE SEQUENCE x_seq;

29
src/test/regress/sql/privileges.sql
View File

@ -37,7 +37,7 @@ ALTER GROUP regressgroup1 ADD USER regressuser4;
ALTER GROUP regressgroup2 ADD USER regressuser2; -- duplicate
ALTER GROUP regressgroup2 DROP USER regressuser2;
ALTER GROUP regressgroup2 ADD USER regressuser4;
GRANT regressgroup2 TO regressuser4 WITH ADMIN OPTION;
-- test owner privileges
@ -599,6 +599,33 @@ SELECT has_table_privilege('regressuser3', 'atest4', 'SELECT'); -- false
SELECT has_table_privilege('regressuser1', 'atest4', 'SELECT WITH GRANT OPTION'); -- true
-- Admin options
SET SESSION AUTHORIZATION regressuser4;
CREATE FUNCTION dogrant_ok() RETURNS void LANGUAGE sql SECURITY DEFINER AS
'GRANT regressgroup2 TO regressuser5';
GRANT regressgroup2 TO regressuser5; -- ok: had ADMIN OPTION
SET ROLE regressgroup2;
GRANT regressgroup2 TO regressuser5; -- fails: SET ROLE suspended privilege
SET SESSION AUTHORIZATION regressuser1;
GRANT regressgroup2 TO regressuser5; -- fails: no ADMIN OPTION
SELECT dogrant_ok(); -- ok: SECURITY DEFINER conveys ADMIN
SET ROLE regressgroup2;
GRANT regressgroup2 TO regressuser5; -- fails: SET ROLE did not help
SET SESSION AUTHORIZATION regressgroup2;
GRANT regressgroup2 TO regressuser5; -- ok: a role can self-admin
CREATE FUNCTION dogrant_fails() RETURNS void LANGUAGE sql SECURITY DEFINER AS
'GRANT regressgroup2 TO regressuser5';
SELECT dogrant_fails(); -- fails: no self-admin in SECURITY DEFINER
DROP FUNCTION dogrant_fails();
SET SESSION AUTHORIZATION regressuser4;
DROP FUNCTION dogrant_ok();
REVOKE regressgroup2 FROM regressuser5;
-- has_sequence_privilege tests
\c -