Kubernetes Security

Executive Summary

Production-grade Kubernetes security covering defense-in-depth strategies from authentication to runtime protection. This skill provides deep expertise in implementing zero-trust security models, compliance frameworks, and production-hardened configurations for SOC2, PCI-DSS, and HIPAA requirements.

Core Competencies

1. RBAC Architecture

RBAC Hierarchy

User / ServiceAccount / Group
           ↓
    RoleBinding / ClusterRoleBinding
           ↓
    Role / ClusterRole
           ↓
    Rules (apiGroups, resources, verbs)

Production RBAC

apiVersion: v1
kind: ServiceAccount
metadata:
  name: api-server
  namespace: production
automountServiceAccountToken: false
---
apiVersion: rbac.authorization.k8s.io/v1
kind: Role
metadata:
  name: api-server-role
  namespace: production
rules:
- apiGroups: [""]
  resources: ["configmaps"]
  verbs: ["get", "list", "watch"]
  resourceNames: ["api-config"]
- apiGroups: [""]
  resources: ["secrets"]
  verbs: ["get"]
  resourceNames: ["api-secrets"]
---
apiVersion: rbac.authorization.k8s.io/v1
kind: RoleBinding
metadata:
  name: api-server-binding
  namespace: production
roleRef:
  apiGroup: rbac.authorization.k8s.io
  kind: Role
  name: api-server-role
subjects:
- kind: ServiceAccount
  name: api-server
  namespace: production

2. Pod Security Standards

Restricted Security Context

apiVersion: v1
kind: Pod
metadata:
  name: secure-app
spec:
  securityContext:
    runAsNonRoot: true
    runAsUser: 10000
    runAsGroup: 10000
    fsGroup: 10000
    seccompProfile:
      type: RuntimeDefault
  containers:
  - name: app
    image: myregistry.io/app:v1.0.0@sha256:abc123
    securityContext:
      allowPrivilegeEscalation: false
      readOnlyRootFilesystem: true
      capabilities:
        drop: ["ALL"]
    volumeMounts:
    - name: tmp
      mountPath: /tmp
  volumes:
  - name: tmp
    emptyDir: {}

Namespace Enforcement

apiVersion: v1
kind: Namespace
metadata:
  name: production
  labels:
    pod-security.kubernetes.io/enforce: restricted
    pod-security.kubernetes.io/enforce-version: latest
    pod-security.kubernetes.io/warn: baseline
    pod-security.kubernetes.io/audit: restricted

3. Policy Enforcement

Kyverno Policy

apiVersion: kyverno.io/v1
kind: ClusterPolicy
metadata:
  name: require-run-as-nonroot
spec:
  validationFailureAction: Enforce
  rules:
  - name: run-as-non-root
    match:
      any:
      - resources:
          kinds:
          - Pod
    validate:
      message: "Containers must run as non-root"
      pattern:
        spec:
          containers:
          - securityContext:
              runAsNonRoot: true

OPA Gatekeeper

apiVersion: templates.gatekeeper.sh/v1
kind: ConstraintTemplate
metadata:
  name: k8srequiredlabels
spec:
  crd:
    spec:
      names:
        kind: K8sRequiredLabels
  targets:
  - target: admission.k8s.gatekeeper.sh
    rego: |
      package k8srequiredlabels
      violation[{"msg": msg}] {
        provided := {l | input.review.object.metadata.labels[l]}
        required := {l | l := input.parameters.labels[_]}
        missing := required - provided
        count(missing) > 0
        msg := sprintf("Missing labels: %v", [missing])
      }

4. Secret Management

External Secrets Operator

apiVersion: external-secrets.io/v1beta1
kind: ClusterSecretStore
metadata:
  name: aws-secrets-manager
spec:
  provider:
    aws:
      service: SecretsManager
      region: us-east-1
      auth:
        jwt:
          serviceAccountRef:
            name: external-secrets-sa
            namespace: external-secrets
---
apiVersion: external-secrets.io/v1beta1
kind: ExternalSecret
metadata:
  name: database-credentials
  namespace: production
spec:
  refreshInterval: 1h
  secretStoreRef:
    name: aws-secrets-manager
    kind: ClusterSecretStore
  target:
    name: db-credentials
  data:
  - secretKey: password
    remoteRef:
      key: production/database
      property: password

5. Supply Chain Security

Image Signing with Cosign

# Sign image
cosign sign --yes \
  --oidc-issuer=https://token.actions.githubusercontent.com \
  myregistry.io/app:v1.0.0

# Verify in admission
apiVersion: kyverno.io/v1
kind: ClusterPolicy
metadata:
  name: verify-image-signature
spec:
  validationFailureAction: Enforce
  rules:
  - name: verify-signature
    match:
      resources:
        kinds:
        - Pod
    verifyImages:
    - imageReferences:
      - "myregistry.io/*"
      attestors:
      - entries:
        - keyless:
            issuer: "https://token.actions.githubusercontent.com"

Integration Patterns

Uses skill: cluster-admin

• Audit logging configuration
• Node security hardening

Coordinates with skill: storage-networking

• Network policy enforcement
• Secret encryption

Works with skill: monitoring

• Security event alerting
• Compliance dashboards

Troubleshooting Guide

Decision Tree: Access Issues

Access Denied?
│
├── RBAC issue
│   ├── kubectl auth can-i <verb> <resource> --as=<user>
│   ├── Check RoleBindings
│   └── Verify subject matches
│
├── PSS violation
│   ├── Check namespace labels
│   └── Fix securityContext
│
└── Policy blocked
    ├── Check Kyverno/Gatekeeper logs
    └── Review policy rules

Debug Commands

# RBAC debugging
kubectl auth can-i --list --as=system:serviceaccount:prod:myapp
kubectl get rolebindings,clusterrolebindings -A -o wide

# PSS testing
kubectl label ns test pod-security.kubernetes.io/enforce=restricted --dry-run=server

# Policy status
kubectl get constraints -A
kubectl get clusterpolicies

Common Challenges & Solutions

Challenge	Solution
RBAC sprawl	Regular audits, automation
Secret rotation	External Secrets Operator
Policy exceptions	Document, time-limit
Compliance gaps	CIS Benchmark scanning

Success Criteria

Metric	Target
RBAC least privilege	100%
PSS restricted	All prod namespaces
Network policy coverage	100%
Image signing	100% production

Resources

• RBAC Authorization
• Pod Security Standards
• Kyverno