Automatically allow access to tables in postgres from a user - postgresql

Question

I have a Postgresql database for a web application. The database is owned by a particular user on the system, let's say foouser. As the owner, this user has full permissions on the database.
The server also has another user, let's say webappuser, which is the user under which the application server runs. Instead of specifying a username and password in the web application's config file, I want to use "peer" authentication. I have gotten the authentication to work properly, but I ran into the following issue.
When I created the webappuser role in Postgresql, I granted it LOGIN permission as well as GRANT ALL ON DATABASE foo TO webappuser; and within the database GRANT ALL ON SCHEMA public TO webappuser;.
The issue that I am having is with the table permissions. Unlike MySQL which allows access by default to all tables if you have access to the database (a reasonable assumption in my opinion), Postgresql denies access to all of the tables even though permission has been given on the schema and the database. In order to get around this, I have to explicitly grant permissions on all new tables, views, procedures, etc. that I create using GRANT ALL ON TABLE table_name TO webappuser; (and similarly for views, etc.).
It ends up that any time I run a database migration, I have to add the permissions to the database for the new tables that were created. The problem is that I can't add this permission information to the migrations themselves because developer machines don't have that additional user. In any case, that really looks like the wrong way of doing things.
How can I allow access to the database tables from this additional user without needing manual intervention every time a table, view, procedure, etc. is created?
BONUS POINTS: Is there a way to restrict the user's permission to only CRUD operations instead of full permissions and still do the whole thing automatically?

Answer 1

Without experience with the specifics of Laravel migrations: When you do migrations on the same server there should be no problem, so long as the permissions are also migrated, because the webappuser is available cluster-wide.
When migrating to a different server you need to create the user on that new server and set the permissions for all migrated objects. You basically have two ways to do that.
The first is to set default privileges on the tables in the schema before you migrate or GRANT SELECT, INSERT, UPDATE, DELETE ON ALL TABLES IN SCHEMA sch_name TO webappuser after the migration. Default privileges are set with:
ALTER DEFAULT PRIVILEGES IN SCHEMA sch_name
GRANT SELECT, INSERT, UPDATE, DELETE ON TABLES TO webappuser;
Both commands are fully SQL-standard compliant so you should have no problems across compliant architectures.
Keep in mind that any other tables created in the same schema will also have privileges set for webappuser. Setting privileges this way for an "untrusted" user (the person using the web application) is not recommended in a production environment because of potential privilege leaks; in a development environment it may be acceptable.
The second - which I would favour personally - is to write a stored procedure that sets the appropriate permissions. Do the migration, run the stored procedure once and you should be up-and-running. This gives you more control over the permission granting. The procedure could be something like:
CREATE FUNCTION grant_webapp_privileges() RETURNS void AS $$
-- Create the webappuser, if necessary
CREATE ROLE webappuser LOGIN;
-- Grant privileges on all required objects
GRANT SELECT, INSERT, UPDATE, DELETE ON TABLE table1 TO webappuser;
...
$$ LANGUAGE SQL;
On the master database you simply need to keep the stored procedure up-to-date when you create or drop new relations. If Laravel supports insertion of code blocks not in the schema you are migrating, you can make the above procedure an anonymous code block that gets executed after the migration.
(As an aside, I NEVER give webappuser-like roles CRUD access. Instead I always provide access through views that hide some of the underlying data model specifics, such as a person having an address, contact_information and other details; the view serves it all up in one big row. That way you can easily change the underlying relations and update the view, rather than having to tweak your web application. Same principle really as OOP and easier to manage privileges.)