Using Access Control Views in PostgreSQL

Question

I have a table schema, the content of which basically boils down to:

• User Recruitment
• Object Group Set
• Access Control List (acl) indicating which users have access to those groups
• A collection of objects, each of which belongs to exactly one group.

I want to create a simple application that supports access control. I think the views will be a good approach here.

Suppose I have the following database initialization:

/* Database definition */

BEGIN;

CREATE SCHEMA foo;

CREATE TABLE foo.users (
    id SERIAL PRIMARY KEY,
    name TEXT
);

CREATE TABLE foo.groups (
    id SERIAL PRIMARY KEY,
    name TEXT
);

CREATE TABLE foo.acl (
    user_ INT REFERENCES foo.users,
    group_ INT REFERENCES foo.groups
);

CREATE TABLE foo.objects (
    id SERIAL PRIMARY KEY,
    group_ INT REFERENCES foo.groups,
    name TEXT,
    data TEXT
);

/* Sample data */

-- Create groups A and B
INSERT INTO foo.groups VALUES (1, 'A');
INSERT INTO foo.groups VALUES (2, 'B');

-- Create objects belonging to group A
INSERT INTO foo.objects VALUES (1, 1, 'object in A', 'apples');
INSERT INTO foo.objects VALUES (2, 1, 'another object in A', 'asparagus');

-- Create objects belonging to group B
INSERT INTO foo.objects VALUES (3, 2, 'object in B', 'bananas');
INSERT INTO foo.objects VALUES (4, 2, 'object in B', 'blueberries');

-- Create users
INSERT INTO foo.users VALUES (1, 'alice');
INSERT INTO foo.users VALUES (2, 'amy');
INSERT INTO foo.users VALUES (3, 'billy');
INSERT INTO foo.users VALUES (4, 'bob');
INSERT INTO foo.users VALUES (5, 'caitlin');
INSERT INTO foo.users VALUES (6, 'charlie');

-- alice and amy can access group A
INSERT INTO foo.acl VALUES (1, 1);
INSERT INTO foo.acl VALUES (2, 1);

-- billy and bob can access group B
INSERT INTO foo.acl VALUES (3, 2);
INSERT INTO foo.acl VALUES (4, 2);

-- caitlin and charlie can access groups A and B
INSERT INTO foo.acl VALUES (5, 1);
INSERT INTO foo.acl VALUES (5, 2);
INSERT INTO foo.acl VALUES (6, 1);
INSERT INTO foo.acl VALUES (6, 2);

COMMIT;

- , , , ( PHP script) ( "bob" ). , PostgreSQL ( , - ):

BEGIN;

CREATE TEMPORARY VIEW users AS
SELECT * FROM foo.users
WHERE name='bob';

CREATE TEMPORARY VIEW acl AS
SELECT acl.* FROM foo.acl, users
WHERE acl.user_=users.id;

CREATE TEMPORARY VIEW groups AS
SELECT groups.* FROM foo.groups, acl
WHERE groups.id=acl.group_;

CREATE TEMPORARY VIEW objects AS
SELECT objects.* FROM foo.objects, groups
WHERE objects.group_=groups.id;

COMMIT;

, ? CREATE TEMPORARY VIEW , ?

, , ? , , .

Answer 1

:

• - - , . .

• , / .

- :

CREATE VIEW AllowedObjects
SELECT objects.*, users.name AS alloweduser
FROM objects
   INNER JOIN groups ON groups.id = objects.group_
   INNER JOIN acl ON acl.group_ = groups.id
   INNER JOIN users ON users.id = acl.user_

:

SELECT * FROM AllowedObjects
WHERE alloweduser='Bob'

, ACL, , DISTINCT .

, UPDATE DELETE:

CREATE VIEW AllowedUserGroup
SELECT groups.id AS allowedgroup, users.name AS alloweduser
FROM groups
   INNER JOIN acl ON acl.group_ = groups.id
   INNER JOIN users ON users.id = acl.user_

, , UPDATE/DELETE:

UPDATE objects SET foo='bar' WHERE id=42 AND EXISTS
(SELECT NULL FROM AllowedUserGroup 
 WHERE alloweduser='Bob' AND allowedgroup = objects.group_)