Mastering Pod Security in Kubernetes

In the rapidly evolving landscape of Kubernetes, security remains a top concern for developers and architects. Kubernetes 1.25 brings significant changes, particularly in the way we approach pod security, an area critical to secure application deployment. This article dives deep into the intricacies of Pod Security Admission (PSA), the successor to Pod Security Policies (PSP), providing insights and practical guidance for effectively leveraging its potential.

Understanding Under Security Admission

Along with the suspension of Pod Security Policy in previous releases, Kubernetes 1.29 highlights Pod Security Admission (PSA), a built-in access controller designed to enforce Pod security standards at creation and modification time. PSA introduces a simpler, more understandable and manageable approach to securing floors, critical to protecting cluster resources and data.

Basics of PSA

PSA works on the principle of predefined security levels: privileged, basic and restricted. These levels provide a clear framework for securing your pods based on the security posture you require:

• Privileged: This level is essentially unlimited and should be used sparingly as it exposes modules to significant security vulnerabilities.
• The baseline: A moderate level that provides protection against known privilege escalations while maintaining broad compatibility with existing applications.
• Limited: This level applies a rigorous set of security standards, minimizing the attack surface and enforcing best practices.

Implementation of Under Security Admission

In order to use PSA effectively, it is essential to understand its configuration and deployment process. Let’s walk through the steps to enforce pod security standards within a Kubernetes cluster.

Step 1: Enable Pod Security Admission

Make sure your Kubernetes cluster is running version 1.25 or higher. PSA is on by default, but it’s crucial to check its activation:

apiVersion: admissionregistration.k8s.io/v1
kind: ValidatingWebhookConfiguration
metadata:
  name: "podsecurity.webhook.admission.k8s.io"

Step 2: Define the namespace tags

PSA uses namespace tags to determine the security level for pods within that namespace. Define the desired level by marking each namespace:

kubectl label ns <namespace> pod-security.kubernetes.io/enforce=baseline

This example sets the security level to basic for the specified namespace.

Step 3: Configuring Pod security standards

Configuration at the namespace level allows for flexibility and granularity in security enforcement. For example, to apply the restricted level, you would update the namespace configuration as follows:

kubectl label ns <namespace> pod-security.kubernetes.io/enforce=restricted

Practical example: setting up a security unit

Let’s illustrate how to implement a floor that complies with a limited security level. This example assumes that you have already marked your namespace as restricted.

Secure Pod Manifest

apiVersion: v1
kind: Pod
metadata:
  name: secure-example
spec:
  securityContext:
    runAsNonRoot: true
    seccompProfile:
      type: RuntimeDefault
  containers:
  - name: secure-container
    image: nginx:stable
    securityContext:
      allowPrivilegeEscalation: false
      capabilities:
        drop: ["ALL"]

This manifest defines a pod that adheres to limited standards, ensuring that it runs as a non-root user and preventing privilege escalation.

Pod Security Best Practices

The adoption of PSA requires a change in our approach to capsule safety. Here are key best practices to consider:

• Gradual adoption: Start with privileged, move to baseline and aim for restricted to reduce interference.
• Audit and supervision: Use auditing and alerting modes to identify non-compliant resources without forcing changes.
• Continuous education: Keep your team informed about the latest security features and practices in Kubernetes.

Conclusion

As Kubernetes continues to mature, its security mechanisms evolve to offer more robust protections and simpler management. The Security Admission pod in Kubernetes 1.25+ represents a significant step forward in securing container environments, providing clear guidance and practical tools for developers and architects. By understanding and implementing these new standards, you can significantly improve the security posture of your Kubernetes deployments.

Embracing these changes not only secures your applications, but also aligns your security practices with the latest developments in Kubernetes. As we manage this change, the importance of adaptation and continuous learning cannot be overstated – our journey towards a more secure, efficient and reliable container orchestration continues.