Verify Signed Container Images

FEATURE STATE: Kubernetes v1.24 [alpha]

Before you begin

These instructions are for Kubernetes 1.25. If you want to check the integrity of components for a different version of Kubernetes, check the documentation for that Kubernetes release.

You will need to have the following tools installed:

  • cosign (install guide)
  • curl (often provided by your operating system)

Verifying image signatures

For a complete list of images that are signed please refer to Releases.

Let’s pick one image from this list and verify its signature using the cosign verify command:

  1. COSIGN_EXPERIMENTAL=1 cosign verify registry.k8s.io/kube-apiserver-amd64:v1.24.0

Note: COSIGN_EXPERIMENTAL=1 is used to allow verification of images signed in KEYLESS mode. To learn more about keyless signing, please refer to Keyless Signatures .

Verifying images for all control plane components

To verify all signed control plane images, please run this command:

  1. curl -Ls https://sbom.k8s.io/$(curl -Ls https://dl.k8s.io/release/latest.txt)/release | grep 'PackageName: registry.k8s.io/' | awk '{print $2}' > images.txt
  2. input=images.txt
  3. while IFS= read -r image
  4. do
  5.   COSIGN_EXPERIMENTAL=1 cosign verify "$image"
  6. done < "$input"

Once you have verified an image, specify that image by its digest in your Pod manifests as per this example: registry-url/image-name@sha256:45b23dee08af5e43a7fea6c4cf9c25ccf269ee113168c19722f87876677c5cb2 .

For more information, please refer to Image Pull Policy section.

Verifying Image Signatures with Admission Controller

For non-control plane images ( e.g. conformance image) , signatures can also be verified at deploy time using sigstore policy-controller admission controller. To get started with policy-controller here are a few helpful resources: