Enforcing Pod Security Standards

This page provides an overview of best practices when it comes to enforcing Pod Security Standards.

Using the built-in Pod Security Admission Controller

The Pod Security Admission Controller intends to replace the deprecated PodSecurityPolicies.

Configure all cluster namespaces

Namespaces that lack any configuration at all should be considered significant gaps in your cluster security model. We recommend taking the time to analyze the types of workloads occurring in each namespace, and by referencing the Pod Security Standards, decide on an appropriate level for each of them. Unlabeled namespaces should only indicate that they've yet to be evaluated.

In the scenario that all workloads in all namespaces have the same security requirements, we provide an example that illustrates how the PodSecurity labels can be applied in bulk.

Embrace the principle of least privilege

In an ideal world, every pod in every namespace would meet the requirements of the restricted policy. However, this is not possible nor practical, as some workloads will require elevated privileges for legitimate reasons.

• Namespaces allowing privileged workloads should establish and enforce appropriate access controls.
• For workloads running in those permissive namespaces, maintain documentation about their unique security requirements. If at all possible, consider how those requirements could be further constrained.

Adopt a multi-mode strategy

The audit and warn modes of the Pod Security Standards admission controller make it easy to collect important security insights about your pods without breaking existing workloads.

It is good practice to enable these modes for all namespaces, setting them to the desired level and version you would eventually like to enforce. The warnings and audit annotations generated in this phase can guide you toward that state. If you expect workload authors to make changes to fit within the desired level, enable the warn mode. If you expect to use audit logs to monitor/drive changes to fit within the desired level, enable the audit mode.

When you have the enforce mode set to your desired value, these modes can still be useful in a few different ways:

• By setting warn to the same level as enforce, clients will receive warnings when attempting to create Pods (or resources that have Pod templates) that do not pass validation. This will help them update those resources to become compliant.
• In Namespaces that pin enforce to a specific non-latest version, setting the audit and warn modes to the same level as enforce, but to the latest version, gives visibility into settings that were allowed by previous versions but are not allowed per current best practices.

Third-party alternatives

Other alternatives for enforcing security profiles are being developed in the Kubernetes ecosystem:

• Kubewarden.
• Kyverno.
• OPA Gatekeeper.

The decision to go with a built-in solution (e.g. PodSecurity admission controller) versus a third-party tool is entirely dependent on your own situation. When evaluating any solution, trust of your supply chain is crucial. Ultimately, using any of the aforementioned approaches will be better than doing nothing.