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:

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

Verifying images for all control plane components

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

curl -Ls https://sbom.k8s.io/$(curl -Ls https://dl.k8s.io/release/latest.txt)/release | grep 'PackageName: k8s.gcr.io/' | awk '{print $2}' > images.txt
input=images.txt
while IFS= read -r image
do
  COSIGN_EXPERIMENTAL=1 cosign verify "$image"
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 cosigned admission controller. To get started with cosigned here are a few helpful resources:

Last modified April 12, 2022 at 8:29 AM PST: Task Page for Verifying Signed Images (#32184) (ba6776b2a6)