K8s network policy

Examples

Example of Wordpress with Egress Isolation

egress--dns.yaml

---
apiVersion: networking.k8s.io/v1
kind: NetworkPolicy
metadata:
  name: egress-dns
spec:
  podSelector: {}
  policyTypes:
    - Egress
  egress:
  - to:
    - namespaceSelector:
        matchLabels:
          kubernetes.io/metadata.name: kube-system
      podSelector:
        matchLabels:
          k8s-app: kube-dns
    ports:
    - protocol: TCP
      port: 53
    - protocol: UDP
      port: 53

egress--internet-http-https.yaml

---
apiVersion: networking.k8s.io/v1
kind: NetworkPolicy
metadata:
  name: egress-internet-http-https
spec:
  podSelector: {}
  policyTypes:
    - Egress
  egress:
    - to:
        - ipBlock:
            cidr: 0.0.0.0/0
            except:
              - 10.0.0.0/8
              - 192.168.0.0/16
              - 172.16.0.0/20
      ports:
        - protocol: TCP
          port: 443
        - protocol: TCP
          port: 80

egress--wordpress-to-mariadb.yaml

apiVersion: networking.k8s.io/v1
kind: NetworkPolicy
metadata:
  name: egress--wordpress-to-mariadb
spec:
  policyTypes:
    - Egress
  podSelector:
    matchLabels:
      app.kubernetes.io/name: wordpress
  egress:
    - to:
       - namespaceSelector: {}
         podSelector:
           matchLabels:
             app.kubernetes.io/name: mariadb
      ports:
        - protocol: TCP
          port: 3306

egress--email-submission.yaml

---
apiVersion: networking.k8s.io/v1
kind: NetworkPolicy
metadata:
  name: egress--email-submission
spec:
  podSelector: {}
  policyTypes:
    - Egress
  egress:
    - to:
        - ipBlock:
            cidr: ${Your SMTP Submission IP Address}
      ports:
        - protocol: TCP
          port: 587

Apply

kubectl apply -f ../yaml/egress--dns.yaml -f ../yaml/egress--internet-http-https.yaml -f ../yaml/egress--wordpress-to-mariadb.yaml -f ../yaml/egress--email-submission.yaml

Internet Only

• https://stackoverflow.com/questions/57789969/kubernetes-networkpolicy-allow-external-traffic-to-internet-only

Guide

• https://snyk.io/blog/kubernetes-network-policy-best-practices/

Mote

https://loft.sh/blog/kubernetes-network-policies-for-isolating-namespaces/

https://kubernetes.io/docs/concepts/services-networking/network-policies/

https://editor.networkpolicy.io/?id=u7ZyunLd9YSsf9Da

https://cloud.redhat.com/blog/guide-to-kubernetes-egress-network-policies

k8s core DNS example egress

apiVersion: networking.k8s.io/v1
kind: NetworkPolicy
metadata:
  name: foo
spec:
  podSelector:
    matchLabels:
      run: nginx
  policyTypes:
    - Egress
  egress:
    - to:
        - ipBlock:
            cidr: 192.168.0.0/16
      ports:
        - protocol: TCP
          port: 80
          endPort: 81
    - to:
        - namespaceSelector: {}
          podSelector:
            matchLabels:
              k8s-app: kube-dns
      ports:
        - port: 53
          protocol: UDP
        - port: 53
          protocol: TCP

Only k8s dns

apiVersion: networking.k8s.io/v1
kind: NetworkPolicy
metadata:
  name: default-deny-all-egress
spec:
  podSelector: {}
  policyTypes:
    - Egress
    # - Ingress
  egress:
  - to:
    - namespaceSelector:
        matchLabels:
          kubernetes.io/metadata.name: kube-system
      podSelector:
        matchLabels:
          k8s-app: kube-dns
    ports:
    - protocol: TCP
      port: 53
    - protocol: UDP
      port: 53

Internet

apiVersion: networking.k8s.io/v1
kind: NetworkPolicy
metadata:
  name: internet-egress
spec:
  podSelector:
    matchLabels:
      networking/allow-internet-egress: "true"
  egress:
  - {}
  policyTypes:
  - Egress