Re: Thoughts on row-level security for webapps?

Greetings,

* Siegfried Bilstein (sbilstein(at)gmail(dot)com) wrote:
> I'm evaluating using a tool called Postgraphile that generates a GraphSQL
> server from a postgres setup. The recommended way of handling security is
> to implement RLS within postgres and simply have the webserver take a
> cookie or similar and define which user is querying data.
>
> I've normally built webapps like this: pull out user id from a session
> cookie -> the API endpoint verifies the user and whether or not it has
> access to the given data -> app code mutates the data.
>
> With Postgraphile the request specifies the mutation and the server
> processes the request and relies on Postgres to determine if the user has
> correct access rights.
>
> It seems like I would need to create a ROLE for every single member that
> signs up for my website which I'm a little concerned about. Is this a
> common usage pattern for SQL security? Any gotchas relying on RLS?

You don't have to create a role for every member, though depending on
your expectation you might want to. You could just set a custom GUC
which is used in the policy, but you then have to trust the web
application code to always do that correctly and to always properly
validate the client (without bugs, of course).

RLS has been around for a while now and it works really rather well in
most cases. There are some corner cases where you're doing some kind of
filtering that might be able to use an index but the functions aren't
leakproof and therefore can't be used, causing a performance regression,
but that's not too hard to test for and only an issue if the policy
itself isn't very selective.

Thanks!

Stephen