I have the below problem I try to solve:
There is an MVC web application (AppA) in domain DomA that is configured to use a CUSTOM STS for authentication/authorization.
On the other hand we have a CRM installation in another domain, the MyCRM domain, that is configured to use ADFS (ADFS is in the same domain as the CRM).
What we want to achieve is the AppA to be able to POST data to the Dynamics CRM Web API but we don’t want the users of AppA to re-enter credentials or have any other kind of interaction regarding authentication/authorization with ADFS. The AppA should be able to POST data from both Javascript (client side) and the backend (MVC controller)
How could we achieve the above? What kind of Trust should we establish between the Custom STS of DomA domain and the ADFS of MyCRM domain?
You don't need federated identity for back-end (server-to-server) connections. You might want to use Impersonation which permits you to setup a user account that can act on behalf of another user in the system.