Restrict access from one service to another

Security
4

Thank you!

Say I need one service has abilities to GET from another service.

I am creating simple ServiceRole which allows GET to my httpbin service:

apiVersion: "rbac.istio.io/v1alpha1"
kind: ServiceRole
metadata:
  name: httpbin
  namespace: default
spec:
  rules:
  - services: ["httpbin.default.svc.cluster.local"]
    methods: ["GET", "HEAD"]

And I am trying to bind this role to another service:

apiVersion: "rbac.istio.io/v1alpha1"
kind: ServiceRoleBinding
metadata:
  name: httpbind
  namespace: default
spec:
  subjects:
  - properties:
      source.namespace: "default" // What property to use ???
  roleRef:
    kind: ServiceRole
    name: "httpbin"

How could I achieve that? I see the closest one is source.principal property, but that means I will need to create a service account for all services?

Thank you!