[keycloak-user] Multi tenant on a given resource

[DES PLAS Leonore]

Hi there,

We are wondering how to achieve "multi tenant" on a resource.
We have a spring boot backend with an angular front end, and are using Spring Security and keycloak-angular adapters.

We have one keycloak used to authenticate and authorize users to the application, that configuration is ok.
But now, for a set of resources (angular paths and REST services), we need to authenticate to an other Keycloak server, which we don't know much of because it is somebody else's.
How can we handle having 2 different Keycloak for a set a resources?
How can we tell in Spring Boot and Angular which AccessToken is the right one ?
Is it possible to check if AccessToken is valid on 2 different Keycloak and only for some paths ?

At first, we thought about user federation... but we don't want to be able to log in to the application just with the 2nd Keycloak. We have to be logged in with the first Keycloak on all paths, and for some paths we want to also be logged in to the 2nd Keycloak.

Thank you for your time,

Léonore DES PLAS MATTEI
Ingénieure Etudes et Développement - Aix en Provence SIG