Re: [GENERAL] LYDB: Feasible to use PG roles instead ofapplication-level security? - Mailing list pgsql-general

> On 30 Dec 2016, at 4:19, Guyren Howe <guyren@gmail.com> wrote:
>
> Further to my attempts to enlighten application developers about what they might better do in the database:
>
> https://medium.com/@gisborne/love-your-database-lydb-23c69f480a1d#.4jngp2rcb
>
> it occurs to me to wonder whether it is practical to use PG’s own roles and security model in lieu of using an
application-levelone. 
>
> It seems that the role system in PG is sufficient for most general purposes. One could presumably also have a table
withrole names and associated metainformation (email address etc) as needed. 
>
> If I have a system with many thousands of users, is it practical to manage these users’ authentication and
authorizationusing *just* Postgres? 

Postgres roles are global to the cluster, so you would end up with multiple thousands of roles if you have multiple
databasesin your cluster with different users on each. Which roles each user is allowed to have becomes quite the
nightmarefor the administrators, I suspect. 

For a web-application facing the internet, I'd say no, don't do that. You're dealing with far too many users to be
maintainable.

For an intranet database in a not-too-large company with a fixed set of users, it could be a good solution, especially
ifthose roles can be linked to the company's LDAP server (assuming that's possible, I don't know). Multiple intranet
applicationson that same database can use the same users and roles. 

Someone needs to do the administration though; with volumes (of users) like that and the database knowledge level of
theaverage system administrator, a GUI seems preferable. IMHO, pgadmin provides too many features to be practical for
someonelike that, you would probably prefer something that only does user administration. I don't know of anything that
doesthat though (not a GUI user myself)... 

> It occurs to me that some client frameworks might have issues with their connection pools if those connections keep
switchingusers, assuming they even can, but let’s set that aside for now. Or perhaps every connection could immediately
doa SET USER before executing its connection? 
>
> This seems an attractive proposition from a security standpoint: if I use row-level security pervasively, I can have
asecurity system that’s nestled nice and close to the data and presumably tricky to work around from a hacker given
directaccess only to the client application. 

With a few changes, that could work very well.

First, create roles for the different types of users that you expect. In a company, that could be by division,
distinguishingdivision-heads, interns, etc. 

Secondly, have a table with the users and their attributes like you describe. Include an attribute for their database
rolethere. Only administrator users should have access to that table. 

Finally, create a stored procedure that looks up a user name in that table and sets the accompanying role. If a user is
notfound, set the role to some default 'unprivileged' user. 
Make that procedure a SECURITY DEFINER with according permissions. That role stays active the entire session, so unless
youclose the connection, create a new one or change the user's role, this procedure doesn't need calling again. 

> Is this practical? Has anyone here done it? What might the caveats be?

It's a fairly common practice, the ML archives should contain plenty of examples.

Alban Hertroys
--
If you can't see the forest for the trees,
cut the trees and you'll find there is no forest.