Configure Network Policies and Egress Firewalls for a ROSA Cluster

It’s common to want to restrict network access between namespaces, as well as restricting where traffic can go outside of the cluster. OpenShift achieves this with the Network Policy and Egress Firewall resources.

It’s common to use these methods to restrict network traffic alongside Egress IP and other OpenShift and OVN-Kubernetes resources.

Prerequisites

• ROSA Cluster 4.14
• openshift-cli (oc)
• rosa-cli (rosa)
• jq

Project Template

The first thing to do is create a Project Template that containes Network Policys and Egress Firewalls with default deny rules

1. Create and Apply a Project template with default deny rules

   NOTE This template will ensure that any new projects have a default deny rule for egress, and a network policy that only allows traffic to come from an Ingress Controller

   cat << "EOF" | oc apply -f -
   apiVersion: template.openshift.io/v1
   kind: Template
   metadata:
     name: project-request
     namespace: openshift-config
   parameters:
     - name: PROJECT_NAME
     - name: PROJECT_DISPLAYNAME
     - name: PROJECT_DESCRIPTION
     - name: PROJECT_ADMIN_USER
     - name: PROJECT_REQUESTING_USER
   objects:
   - apiVersion: project.openshift.io/v1
     kind: Project
     metadata:
       annotations:
         openshift.io/description: ${PROJECT_DESCRIPTION}
         openshift.io/display-name: ${PROJECT_DISPLAYNAME}
         openshift.io/requester: ${PROJECT_REQUESTING_USER}
       creationTimestamp: null
       name: ${PROJECT_NAME}
     spec: {}
     status: {}
   - apiVersion: rbac.authorization.k8s.io/v1
     kind: RoleBinding
     metadata:
       creationTimestamp: null
       name: admin
       namespace: ${PROJECT_NAME}
     roleRef:
       apiGroup: rbac.authorization.k8s.io
       kind: ClusterRole
       name: admin
     subjects:
     - apiGroup: rbac.authorization.k8s.io
       kind: User
       name: ${PROJECT_ADMIN_USER}
   - apiVersion: k8s.ovn.org/v1
     kind: EgressFirewall
     metadata:
       name: default
       namespace: ${PROJECT_NAME}
     spec:
       egress:
         - to:
             cidrSelector: 0.0.0.0/0
           type: Deny
   - apiVersion: networking.k8s.io/v1
     kind: NetworkPolicy
     metadata:
       name: deny-by-default
       namespace: ${PROJECT_NAME}
     spec:
       podSelector: {}
       policyTypes:
         - Ingress
       ingress:
         - from:
           - namespaceSelector:
               matchLabels:
                 network.openshift.io/policy-group: ingress
         - from:
           - podSelector: {}
   EOF
   

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2. Patch the project configuration to use the newly created Project Template

   kubectl patch project.config.openshift.io/cluster --type=merge -p "
   apiVersion: config.openshift.io/v1
   kind: Project
   metadata:
     name: cluster
   spec:
     projectRequestTemplate:
       name: project-request
   "
   

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3. Create a new Project to verify the policies

   oc new-project restricted
   

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4. Check for EgressFirewall

   oc get egressfirewall -n restricted
   

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   you should see

   NAME      EGRESSFIREWALL STATUS
   default   EgressFirewall Rules applied
   

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5. Check for NetworkPolicy

   oc get networkpolicy -n restricted
   

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   you should see

   NAME              POD-SELECTOR   AGE
   deny-by-default   <none>         15m
   

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Test the Network Policy

1. Create a debug pod in the default namespace to use later

   oc run \
     debug \
     --namespace=default \
     --image=registry.access.redhat.com/ubi9/ubi -- \
     sleep 360000
   

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2. Create a debug pod in the restricted namespace to use later

   oc run \
     debug \
     --namespace=restricted \
     --image=registry.access.redhat.com/ubi9/ubi -- \
     sleep 360000
   

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3. Deploy a web service and expose it

   oc -n restricted new-app --name=hello --image=docker.io/openshift/hello-openshift
   oc expose service/hello
   ROUTE=$(oc get route hello -o jsoNetwork Policyath='{.spec.host}')
   echo $ROUTE
   

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4. See if you can access the application via its Route (you should be able to)

   curl -s http://$ROUTE
   

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   You should see

   Hello OpenShift!
   

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5. See if you can access the application via its Route from the default namespace. (again you should be able to)

   oc -n default debug debug -- curl -s http://$ROUTE
   

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   You should see

   Starting pod/debug-debug-xrrmt ...
   Hello OpenShift!
   

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6. Now try to access the application via its local service from within the same pod (this should succeed due to the Network Policy)

   oc -n restricted debug debug -- curl -sv http://hello.restricted:8080
   

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   output

   Starting pod/debug-debug-p69x7 ...
   *   Trying 172.30.137.196:8080...
   ...
   ...
   Hello OpenShift!
   Removing debug pod ...
   

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7. Now try to access the application via its local service (this should fail due to the Network Policy)

   NOTE: To avoid waiting for a long timeout feel free to hit CTRL-C.

   oc -n default debug debug -- curl -sv http://hello.restricted:8080
   

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   output

   Starting pod/debug-debug-p69x7 ...
   *   Trying 172.30.137.196:8080...
   <CTRL-C>
   

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Test the Egress Firewall

1. Verify you can access an external website from the default namespace debug pod (this should work)

   oc -n default debug debug -- curl -sSL https://icanhazip.com
   

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   output

   Starting pod/debug-debug-sznlt ...
   *   Trying 104.16.185.241:443...
   * Connected to icanhazip.com (104.16.185.241) port 443 (#0)
   ...
   ...
   3.136.221.97
   

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2. Verify that you cannot access an external website from the restricted namespace (this should fail)

   oc -n restricted debug debug -- curl -sSL https://icanhazip.com
   

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   output

   oc -n restricted debug debug -- curl -sSL https://icanhazip.com
   Starting pod/debug-debug-rbd79 ...
   <CTRL-C>
   

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