Kubernetes

What is Kubernetes?

Kubernetes (often abbreviated as K8s) is an open-source container orchestration platform designed to automate the deployment, scaling, and management of containerized applications. Originally developed by Google based on their internal container management system (Borg), Kubernetes is now maintained by the Cloud Native Computing Foundation (CNCF).

Kubernetes provides a framework to run distributed systems across clusters of machines, abstracting away the underlying infrastructure and enabling developers to focus on building applications rather than managing deployment environments.

Core Kubernetes Concepts

Cluster Architecture

Kubernetes operates on a cluster consisting of:

• Control Plane (Master Node): The brain of the cluster that manages scheduling, state maintenance, and API access

  • API Server: Entry point for all REST commands
  • Scheduler: Assigns workloads to nodes
  • Controller Manager: Maintains the desired state
  • etcd: Distributed key-value store for cluster state

• Worker Nodes: Machines that run containerized applications

  • Kubelet: Agent that communicates with control plane
  • Container Runtime: Software that runs containers (Docker, containerd, CRI-O)
  • Kube Proxy: Network proxy maintaining network rules

Kubernetes Objects

Kubernetes uses declarative objects to represent the desired state of the system:

• Pods: The smallest deployable units in Kubernetes, containing one or more containers that share storage and network resources
• Deployments: Define the desired state for pod replicas, enabling rolling updates and rollbacks
• Services: Abstract way to expose applications running in pods, providing stable network endpoints
• ConfigMaps and Secrets: Mechanisms to separate configuration from code
• Namespaces: Virtual clusters within a physical cluster, providing isolation for resources
• Persistent Volumes: Storage resources in the cluster, independent of pod lifecycle

Kubernetes in the Software Supply Chain

Kubernetes plays multiple important roles in the software supply chain:

Deployment Environment

Kubernetes provides a consistent platform for deploying applications, reducing "works on my machine" problems and standardizing the runtime environment across development, testing, and production.

Immutable Infrastructure

Kubernetes embraces immutable infrastructure principles by treating containers as immutable artifacts and replacing (rather than updating) pods when configurations change.

Security Controls

Kubernetes offers various security mechanisms relevant to supply chain security:

• Role-Based Access Control (RBAC): Granular permissions for cluster resources
• Pod Security Policies/Standards: Enforcing security requirements for pods
• Network Policies: Controlling traffic between pods and external services
• Admission Controllers: Intercepting and potentially rejecting requests to create or modify resources

Supply Chain Integration

Kubernetes integrates with modern supply chain security tools:

• Image Scanning: Vulnerability scanning for containers
• Policy Enforcement: Using OPA Gatekeeper or Kyverno to enforce security policies
• Sigstore Integration: Verifying container signatures before deployment
• SBOM Management: Managing Software Bills of Materials for deployed containers

Kubernetes Security Considerations

Image Security

• Image Vulnerability Scanning: Identifying and remediating vulnerabilities in container images
• Image Signing and Verification: Ensuring images come from trusted sources using tools like Cosign
• Private Registries: Using authenticated and secure registries to store trusted images

Cluster Security

• Control Plane Hardening: Securing the core components of Kubernetes
• Node Security: Properly securing the underlying host systems
• Network Security: Implementing network segmentation and encryption
• Secret Management: Properly handling sensitive information

Runtime Security

• Pod Security Standards: Implementing baseline security policies for pods
• Runtime Protection: Using tools to monitor for suspicious behavior
• Audit Logging: Maintaining comprehensive records of all activities

Kubernetes Ecosystem Tools

Supply Chain Security Tools

• Sigstore/Cosign: For signing and verifying container images
• Kyverno: Policy management for K8s resources
• OPA Gatekeeper: Policy enforcement engine for Kubernetes
• Trivy/Clair: Container vulnerability scanners
• Notary: Trusted content delivery system

Management and Monitoring

• Helm: Package manager for Kubernetes
• Prometheus: Monitoring system and time-series database
• Grafana: Visualization and dashboarding
• Istio: Service mesh providing additional security controls
• Argo CD: Declarative GitOps CD for Kubernetes

Best Practices for Kubernetes in a Secure Supply Chain

1. Use Minimal Base Images: Start with small, secure base images like distroless or Alpine
2. Implement CI/CD Pipeline Security: Secure the pipelines that build and deploy to Kubernetes
3. Apply Least Privilege Principles: Use RBAC and ensure all components have minimal permissions
4. Enforce Image Signing: Require cryptographic signatures for all deployed container images
5. Implement Network Policies: Control network traffic between pods and external services
6. Regular Vulnerability Scanning: Continuously scan images and running containers
7. Enable Audit Logging: Maintain comprehensive logs of all activities within the cluster
8. Use Namespaces for Isolation: Properly segment workloads using namespaces
9. Implement Pod Security Standards: Apply appropriate security contexts to pods
10. Automate Security Policy Enforcement: Use admission controllers to enforce security policies