Kyverno: The Reference Architecture for Kubernetes-native Policy Management

TL;DR

Kubernetes is permissive by default: it allows developers almost anything, including insecure configurations (e.g., running containers as “Root”). To prevent this, policy engines like OPA Gatekeeper were needed, which require a steep learning curve (Rego programming language). Kyverno democratizes security. It is a policy engine built for Kubernetes. Policies are simple YAML. Kyverno can not only block (validation) but also actively fix resources (mutation) and generate default configurations (generation) without developers having to change their workflow.

1. The Architecture Principle: Policy as YAML (No Rego!)

The biggest hurdle for governance in Kubernetes was the language. The industry standard Open Policy Agent (OPA) uses Rego, a complex query language. Anyone wanting to write a rule (“No LoadBalancers without a cost center”) had to learn programming.

Kyverno changes the paradigm: Kubernetes-native Policies.

• YAML-based: If you can define a Pod, you can write a Kyverno policy. It uses the same structures and patterns as Kubernetes itself.
• Admission Controller: Kyverno hooks into the API server as a webhook. Every request (e.g., kubectl apply) is checked by Kyverno before being written to the database (etcd).

2. Core Feature: Mutation & Generation (Automation instead of Blockade)

Most policy tools can only say “No” (validation). This frustrates developers (“Deployment failed”). Kyverno is more constructive.

• Mutation (Silent Fixing): A developer forgets the label team: marketing? Instead of rejecting the deployment, Kyverno automatically adds the label. An image has no tag (:latest)? Kyverno changes it at runtime to the specific digest SHA.
• Generation (Self-Service): This is Kyverno’s superpower. A developer creates a new namespace? Kyverno automatically generates the appropriate NetworkPolicies, ResourceQuotas, and Secrets for the image registry. This enables true self-service without security gaps.

3. Supply Chain Security

Kyverno is the guardian of your software supply chain. In combination with tools like Cosign (Sigstore), Kyverno checks cryptographic signatures.

You can define a policy: “Only run images signed by our CI pipeline.”

Even if an attacker gains access to the cluster and tries to start a malicious container, Kyverno blocks the request because the signature is missing.

4. Operational Models Compared: OPA Gatekeeper vs. ayedo Managed Kyverno

Here it is decided whether governance remains a theoretical concept or becomes a lived practice.

Scenario A: OPA Gatekeeper (The Expert Hurdle)

Gatekeeper is powerful but cumbersome.

• The Rego Barrier: To write or debug a policy, you need specialists. Ops teams often shy away from the effort of writing their own rules and rely on standard libraries that often don’t fit exactly.
• No Generation: Gatekeeper can primarily validate. It cannot create new resources (like default network policies). You need additional tools or operators for that.
• Debugging Pain: When a deployment is blocked, the error message from Rego is often cryptic for the end user.

Scenario B: Kyverno with Managed Kubernetes by ayedo

In the ayedo app catalog, Kyverno is the standard for security.

• Readability: Anyone on the team can kubectl get clusterpolicy and immediately understand what is allowed and what is not. Security becomes transparent.
• Best-Practice Library: Ayedo delivers Kyverno with a set of proven policies (Pod Security Standards) that are immediately active (e.g., “Disallow Privileged Containers”).
• Background Scanning: Kyverno not only checks new requests but also scans existing workloads. It creates reports (“Policy Reports”) that show you where you have compliance violations in the cluster without breaking everything immediately.

5. Technical Comparison of Operational Models

FAQ: Kyverno & Governance Strategy

Does Kyverno slow down my cluster?

Kyverno operates as a webhook. Yes, it adds a tiny latency (milliseconds) when creating resources. It has zero impact on the running performance of the application. Kyverno is highly optimized and uses caching to avoid slowing down API calls.

Can I introduce Kyverno without blocking everything?

Yes, that is the recommended way. You first set policies to Audit mode. Kyverno then lets everything through but creates reports on violations. This way, you see which deployments would fail. Only when you are sure, you switch to Enforce.

Does Kyverno replace Pod Security Policies (PSP)?

Yes. Pod Security Policies were removed in Kubernetes v1.25. Kyverno (or the integrated Pod Security Admission Controller) is the official successor. Kyverno is significantly more flexible and granular than the old PSPs.

What happens in an emergency (Break Glass)?

Kyverno can be configured so that certain users (e.g., cluster-admin in an emergency group) are exempt from the policies. Additionally, the webhook can be set (failurePolicy: Ignore) so that in a total Kyverno failure, the cluster still accepts deployments (Fail Open) to ensure operations.

Conclusion

Security must be simple, or it will be bypassed. OPA Gatekeeper has served well for years, but it is too complex for many teams (“Over-Engineering”). Kyverno brings governance back to reality – with understandable YAML and powerful features like mutation and generation. With the ayedo Managed Stack, you get a policy engine that not only says “No” but actively keeps your cluster clean, secure, and compliant – automatically and transparently.