What if your Kubernetes cluster simply refused to run unsigned images?

I spent some time experimenting with enforcing image provenance in a small Kubernetes setup using MicroK8s.

The idea was simple:

Only container images with valid cryptographic signatures are allowed to run in the cluster.

For this I used:

GitLab CI/CD (build + signing pipeline)

Cosign / Sigstore (image signing)

Kyverno (admission control)

MicroK8s (local cluster)

Repo: https://github.com/trottomv/microk8s-cosign-kyverno

Why this matters

Most Kubernetes setups still rely on mutable image tags like latest , which introduces supply chain risks:

No guarantee of image origin

No binding between CI pipeline and deployed artifact

Risk of registry or tag mutation

So the trust gap is basically:

build time → registry → runtime

Architecture

┌──────────────────────────────┐ │ GitLab CI/CD │ │ │ │ • Build container image │ │ • Push to OCI registry │ │ • Sign image (Cosign) │ │ • Publish signature │ └──────────────┬───────────────┘ │ ▼…