OAuth2 (Keycloak): client_credentials grant type additional claims

I have a scenario wherein there are multiple apps/service that need to access my Resource:

These are the three external services: service1, service2, service3.

Now I am using the client_credentials grant type for this since this is machine to machine and no user is involved.

What I did is to create 1 client for each service in Keycloak. It works fine, however I need to add some more details in the token, in particular, a human readable name for each client as the client id is named using the recommended naming.

I know how to map user claims to the token, but is it possible to have something similar for my scenario wherein there are no users and I only have the clients?

Solution

Yes, go to the Realm of your app, then:

Go to Clients;
Select your client;
Select Mappers;
click on the button [Create];
select Hardcoded Claim as Mapper Type;
fill up the details of the claim

Click [Save].

Update answer with more detail

I know how to map user claims to the token, but is it possible to have something similar for my scenario wherein there are no users and I only have the clients?

Yes, you need to create 'Hardcoded Claim Mapper.

For that:

Select the realm of your app
Go to clients
Select the appropriate client for your use-case

(For the OLD Keycloak UI)

Go to Mappers
Click Create
In Mapper type select Hardcoded claim
Fill up the details of the claim, accordingly.
Click on Save

(For the NEW Keycloak UI)

Go to the tab Client Scopes
Click on the client scope <the client ID of your client>-dedicated (e.g., test-dedicated in the picture below)

Click on Configure a new mapper (or Add Mapper > By configuration if you have already created mappers before for this client)

Select Hardcoded claim
Fill up the details of the claim, accordingly.
Click on Save

The client will be the client that you are using to authenticate against.