Implementing Kubernetes Network Policy with Calico

Genel Bakış

Calico is an open-source CNI plugin that provides fine-grained network policy enforcement for Kubernetes clusters. It implements the full Kubernetes NetworkPolicy API and extends it with Calico-specific GlobalNetworkPolicy, supporting policy ordering, deny rules, and service-account-based selectors.

Ne Zaman Kullanılır

• Dağıt:ing yaparken or configuring implementing kubernetes network policy with calico capabilities in your environment
• establishing yaparken: security controls aligned to compliance requirements
• building yaparken or improving security architecture for this domain
• conducting yaparken security assessments that require this implementation

Ön Gereksinimler

• Kubernetes cluster (v1.24+)
• Calico CNI kurulu (v3.26+)
• kubectl and calicoctl CLI tools
• Cluster admin RBAC permissions

Installing Calico

Operator-based Installation (Recommended)

kubectl create -f https://raw.githubusercontent.com/projectcalico/calico/v3.27.0/manifests/tigera-operator.yaml

kubectl create -f https://raw.githubusercontent.com/projectcalico/calico/v3.27.0/manifests/custom-resources.yaml

kubectl get pods -n calico-system
watch kubectl get pods -n calico-system

kubectl apply -f https://raw.githubusercontent.com/projectcalico/calico/v3.27.0/manifests/calicoctl.yaml

Verify Calico is Running

kubectl get pods -n calico-system

kubectl exec -n calico-system calicoctl -- calicoctl node status

kubectl exec -n calico-system calicoctl -- calicoctl get ippool -o wide

Kubernetes NetworkPolicy

Default Deny All Traffic

apiVersion: networking.k8s.io/v1
kind: NetworkPolicy
metadata:
  name: default-deny-ingress
  namespace: production
spec:
  podSelector: {}
  policyTypes:
    - Ingress

---
apiVersion: networking.k8s.io/v1
kind: NetworkPolicy
metadata:
  name: default-deny-egress
  namespace: production
spec:
  podSelector: {}
  policyTypes:
    - Egress

Allow Specific Pod-to-Pod Communication

apiVersion: networking.k8s.io/v1
kind: NetworkPolicy
metadata:
  name: allow-frontend-to-backend
  namespace: production
spec:
  podSelector:
    matchLabels:
      app: backend
  policyTypes:
    - Ingress
  ingress:
    - from:
        - podSelector:
            matchLabels:
              app: frontend
      ports:
        - protocol: TCP
          port: 8080

Allow DNS Egress

apiVersion: networking.k8s.io/v1
kind: NetworkPolicy
metadata:
  name: allow-dns-egress
  namespace: production
spec:
  podSelector: {}
  policyTypes:
    - Egress
  egress:
    - to:
        - namespaceSelector: {}
      ports:
        - protocol: UDP
          port: 53
        - protocol: TCP
          port: 53

Namespace Isolation

apiVersion: networking.k8s.io/v1
kind: NetworkPolicy
metadata:
  name: allow-same-namespace
  namespace: production
spec:
  podSelector: {}
  policyTypes:
    - Ingress
  ingress:
    - from:
        - podSelector: {}

Calico-Specific Policies

GlobalNetworkPolicy (Cluster-Wide)

apiVersion: projectcalico.org/v3
kind: GlobalNetworkPolicy
metadata:
  name: deny-external-ingress
spec:
  order: 100
  selector: "projectcalico.org/namespace != 'ingress-nginx'"
  types:
    - Ingress
  ingress:
    - action: Deny
      source:
        nets:
          - 0.0.0.0/0
      destination: {}

Calico NetworkPolicy with Deny Rules

apiVersion: projectcalico.org/v3
kind: NetworkPolicy
metadata:
  name: deny-database-from-frontend
  namespace: production
spec:
  order: 10
  selector: app == 'database'
  types:
    - Ingress
  ingress:
    - action: Deny
      source:
        selector: app == 'frontend'
    - action: Allow
      source:
        selector: app == 'backend'
      destination:
        ports:
          - 5432

Service Account Based Policy

apiVersion: projectcalico.org/v3
kind: NetworkPolicy
metadata:
  name: allow-by-service-account
  namespace: production
spec:
  selector: app == 'api'
  ingress:
    - action: Allow
      source:
        serviceAccounts:
          names:
            - frontend-sa
            - monitoring-sa
  egress:
    - action: Allow
      destination:
        serviceAccounts:
          names:
            - database-sa

Host Endpoint Protection

apiVersion: projectcalico.org/v3
kind: GlobalNetworkPolicy
metadata:
  name: restrict-host-ssh
spec:
  order: 10
  selector: "has(kubernetes.io/hostname)"
  applyOnForward: false
  types:
    - Ingress
  ingress:
    - action: Allow
      protocol: TCP
      source:
        nets:
          - 10.0.0.0/8
      destination:
        ports:
          - 22
    - action: Deny
      protocol: TCP
      destination:
        ports:
          - 22

Calico Policy Tiers

apiVersion: projectcalico.org/v3
kind: Tier
metadata:
  name: security
spec:
  order: 100

---
apiVersion: projectcalico.org/v3
kind: Tier
metadata:
  name: platform
spec:
  order: 200

Monitoring and Troubleshooting

kubectl get networkpolicy --all-namespaces

kubectl exec -n calico-system calicoctl -- calicoctl get networkpolicy --all-namespaces -o wide
kubectl exec -n calico-system calicoctl -- calicoctl get globalnetworkpolicy -o wide

kubectl exec -n calico-system calicoctl -- calicoctl get workloadendpoint -n production -o yaml

kubectl logs -n calico-system -l k8s-app=calico-node --tail=100

kubectl exec -n production frontend-pod -- wget -qO- --timeout=2 http://backend-svc:8080/health

En İyi Uygulamalar

1. Start with default deny - Apply deny-all policies to every namespace, then allow specific traffic
2. Use labels consistently - Define a labeling standard for app, tier, environment
3. Order policies - Use Calico policy ordering (order field) to control evaluation precedence
4. Allow DNS first - Always create DNS egress rules before applying egress deny policies
5. Use GlobalNetworkPolicy for cluster-wide security baselines
6. Test policies in staging - Validate network connectivity after applying policies
7. Monitor denied traffic - Enable Calico flow logs for visibility into blocked connections
8. Use tiers - Organize policies into security, platform, and application tiers

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