I would like to know if is possible to use Token (JWT) authentication mechanism in Postgres? In order to authenticate users and also authorize access to specific tables, This is in a multi-tenant application context where users can create their own tables and share it if they want.
Is it possible this authentication mechanism or is there any plugin to achieve it?
Postgres can use pam for authentication.
I am not sure that such plugin already exists, but it shouldn't be very hard to implement it.
There are a few problems though:
1. JWT token already contains information about username, but you still have to provide it (username) when opening connection.
2. Token has to be send as a connection password. Therefor connection must be encrypted.
3. Usually JWT tokens are quite big in size, but for example when psql is asking you for a password, it thinks that password can't be longer than 100 characters. And this value is hard-coded. It's possible to overcome this issue if you specify your token in PGPASSWORD env variable.
We at Zalando are using JWT tokens to authenticate employees when they are accessing postgres databases, but we are not dealing with JWT directly.
We have some OAuth infrastructure in-place, which can validate JWT tokens.
At the end it boiled down to sending http request to tokeninfo service and validating its answer.
Basically you can do something similar. Either take pam-oauth2 as a reference and add possibility to validate JWT tokens or implement your tokeninfo service.