2.3. Securing the Service Mesh

Procedure

1. Make sure that all Red Hat OpenShift Serverless projects of your tenant are part of the same ServiceMeshMemberRoll object as members:

   apiVersion: maistra.io/v1
   kind: ServiceMeshMemberRoll
   metadata:
    name: default
    namespace: istio-system
   spec:
    members:
      - knative-serving    # static value, needs to be here, see setup page
      - knative-eventing   # static value, needs to be here, see setup page
      - team-alpha-1       # example OpenShift project that belongs to the team-alpha tenant
      - team-alpha-2       # example OpenShift project that belongs th the team-alpha tenant
      - team-bravo-1       # example OpenShift project that belongs to the team-bravo tenant
      - team-bravo-2       # example OpenShift project that belongs th the team-bravo tenant

   All projects that are part of the mesh must enforce mTLS in strict mode. This forces Istio to only accept connections with a client-certificate present and allows the Service Mesh sidecar to validate the origin using an AuthorizationPolicy object.

2. Create the configuration with AuthorizationPolicy objects in the knative-serving and knative-eventing namespaces:

   Example knative-default-authz-policies.yaml configuration file

   apiVersion: security.istio.io/v1beta1
   kind: AuthorizationPolicy
   metadata:
     name: deny-all-by-default
     namespace: knative-eventing
   spec: { }
   ---
   apiVersion: security.istio.io/v1beta1
   kind: AuthorizationPolicy
   metadata:
     name: deny-all-by-default
     namespace: knative-serving
   spec: { }
   ---
   apiVersion: security.istio.io/v1beta1
   kind: AuthorizationPolicy
   metadata:
     name: allow-mt-channel-based-broker-ingress-to-imc-dispatcher
     namespace: knative-eventing
   spec:
     action: ALLOW
     selector:
       matchLabels:
         app.kubernetes.io/component: "imc-dispatcher"
     rules:
       - from:
           - source:
               namespaces: [ "knative-eventing" ]
               principals: [ "cluster.local/ns/knative-eventing/sa/mt-broker-ingress" ]
         to:
           - operation:
               methods: [ "POST" ]
   ---
   apiVersion: security.istio.io/v1beta1
   kind: AuthorizationPolicy
   metadata:
     name: allow-mt-channel-based-broker-ingress-to-kafka-channel
     namespace: knative-eventing
   spec:
     action: ALLOW
     selector:
       matchLabels:
         app.kubernetes.io/component: "kafka-channel-receiver"
     rules:
       - from:
           - source:
               namespaces: [ "knative-eventing" ]
               principals: [ "cluster.local/ns/knative-eventing/sa/mt-broker-ingress" ]
         to:
           - operation:
               methods: [ "POST" ]
   ---
   apiVersion: security.istio.io/v1beta1
   kind: AuthorizationPolicy
   metadata:
     name: allow-kafka-channel-to-mt-channel-based-broker-filter
     namespace: knative-eventing
   spec:
     action: ALLOW
     selector:
       matchLabels:
         app.kubernetes.io/component: "broker-filter"
     rules:
       - from:
           - source:
               namespaces: [ "knative-eventing" ]
               principals: [ "cluster.local/ns/knative-eventing/sa/knative-kafka-channel-data-plane" ]
         to:
           - operation:
               methods: [ "POST" ]
   ---
   apiVersion: security.istio.io/v1beta1
   kind: AuthorizationPolicy
   metadata:
     name: allow-imc-to-mt-channel-based-broker-filter
     namespace: knative-eventing
   spec:
     action: ALLOW
     selector:
       matchLabels:
         app.kubernetes.io/component: "broker-filter"
     rules:
       - from:
           - source:
               namespaces: [ "knative-eventing" ]
               principals: [ "cluster.local/ns/knative-eventing/sa/imc-dispatcher" ]
         to:
           - operation:
               methods: [ "POST" ]
   ---
   apiVersion: security.istio.io/v1beta1
   kind: AuthorizationPolicy
   metadata:
     name: allow-probe-kafka-broker-receiver
     namespace: knative-eventing
   spec:
     action: ALLOW
     selector:
       matchLabels:
         app.kubernetes.io/component: "kafka-broker-receiver"
     rules:
       - from:
           - source:
               namespaces: [ "knative-eventing" ]
               principals: [ "cluster.local/ns/knative-eventing/sa/kafka-controller" ]
         to:
           - operation:
               methods: [ "GET" ]
   ---
   apiVersion: security.istio.io/v1beta1
   kind: AuthorizationPolicy
   metadata:
     name: allow-probe-kafka-sink-receiver
     namespace: knative-eventing
   spec:
     action: ALLOW
     selector:
       matchLabels:
         app.kubernetes.io/component: "kafka-sink-receiver"
     rules:
       - from:
           - source:
               namespaces: [ "knative-eventing" ]
               principals: [ "cluster.local/ns/knative-eventing/sa/kafka-controller" ]
         to:
           - operation:
               methods: [ "GET" ]
   ---
   apiVersion: security.istio.io/v1beta1
   kind: AuthorizationPolicy
   metadata:
     name: allow-probe-kafka-channel-receiver
     namespace: knative-eventing
   spec:
     action: ALLOW
     selector:
       matchLabels:
         app.kubernetes.io/component: "kafka-channel-receiver"
     rules:
       - from:
           - source:
               namespaces: [ "knative-eventing" ]
               principals: [ "cluster.local/ns/knative-eventing/sa/kafka-controller" ]
         to:
           - operation:
               methods: [ "GET" ]
   ---
   apiVersion: security.istio.io/v1beta1
   kind: AuthorizationPolicy
   metadata:
     name: allow-traffic-to-activator
     namespace: knative-serving
   spec:
     selector:
       matchLabels:
         app: activator
     action: ALLOW
     rules:
       - from:
           - source:
               namespaces: [ "knative-serving", "istio-system" ]
   ---
   apiVersion: security.istio.io/v1beta1
   kind: AuthorizationPolicy
   metadata:
     name: allow-traffic-to-autoscaler
     namespace: knative-serving
   spec:
     selector:
       matchLabels:
         app: autoscaler
     action: ALLOW
     rules:
       - from:
           - source:
               namespaces: [ "knative-serving" ]

   These policies restrict the access rules for the network communication between Serverless system components. Specifically, they enforce the following rules:

   • Deny all traffic that is not explicitly allowed in the knative-serving and knative-eventing namespaces
   • Allow traffic from the istio-system and knative-serving namespaces to activator
   • Allow traffic from the knative-serving namespace to autoscaler
   • Allow health probes for Apache Kafka components in the knative-eventing namespace
   • Allow internal traffic for channel-based brokers in the knative-eventing namespace

3. Apply the authorization policy configuration:

   $ oc apply -f knative-default-authz-policies.yaml

4. Define which OpenShift projects can communicate with each other. For this communication, every OpenShift project of a tenant requires the following:

   • One AuthorizationPolicy object limiting directly incoming traffic to the tenant’s project
   • One AuthorizationPolicy object limiting incoming traffic using the activator component of Serverless that runs in the knative-serving project
   • One AuthorizationPolicy object allowing Kubernetes to call PreStopHooks on Knative Services

   Instead of creating these policies manually, install the helm utility and create the necessary resources for each tenant:

   Installing the helm utility

   $ helm repo add openshift-helm-charts https://charts.openshift.io/

   Creating example configuration for team alpha

   $ helm template openshift-helm-charts/redhat-knative-istio-authz --version 1.36.0 --set "name=team-alpha" --set "namespaces={team-alpha-1,team-alpha-2}" > team-alpha.yaml

   Creating example configuration for team bravo

   $ helm template openshift-helm-charts/redhat-knative-istio-authz --version 1.31.0 --set "name=team-bravo" --set "namespaces={team-bravo-1,team-bravo-2}" > team-bravo.yaml

5. Apply the authorization policy configuration:

   $ oc apply -f team-alpha.yaml team-bravo.yaml