Policy Controller

The policy-controller admission controller can be used to enforce policy on a Kubernetes cluster based on verifiable supply-chain metadata from cosign.

policy-controller also resolves the image tags to ensure the image being ran is not different from when it was admitted.

See the installation instructions for more information.

Today, policy-controller can automatically validate signatures and attestations on container images. Enforcement is configured on a per-namespace basis, and multiple keys are supported.

We're actively working on more features here.

For more information about the policy-controller, have a look at our documentation website here.

Examples

Please see the examples/ directory for example policies etc.

Policy Testing

This repo includes a policy-tester tool which enables checking a policy against various images.

In the root of this repo, run the following to build:

make policy-tester

Then run it pointing to a YAML file containing a ClusterImagePolicy, and an image to evaluate the policy against:

(set -o pipefail && \
    ./policy-tester \
        --policy=test/testdata/policy-controller/tester/cip-public-keyless.yaml \
        --image=ghcr.io/sigstore/cosign/cosign:v1.9.0 | jq)

Local Development

You can spin up a local Kind K8s cluster to test local changes to the policy controller using the local-dev CLI tool. Build the tool with make local-dev and then run it with ./bin/local-dev setup.

It optionally accepts the following:

--cluster-name
--k8s-version
--registry-url

You can clean up the cluster with ./bin/local-dev clean --cluster-name=<my cluster name>.

You will need to have the following tools installed to use this:

• Docker
• kind
• ko
• kubectl

Use local registry

If you would like to use the local Kind registry instead of a live one, do not include the registry-url flag when calling the CLI. It will default to using the local registry. But before running the CLI, you must add the following line to your /etc/hosts file first: 127.0.0.1 registry.local

Using Policy Controller with Azure Container Registry (ACR)

To allow the webhook to make requests to ACR, you must use one of the following methods to authenticate:

1. Managed identities (used with AKS clusters)
2. Service principals (used with AKS clusters)
3. Pod imagePullSecrets (used with non AKS clusters)

See the official documentation.

Managed Identities for AKS Clusters

See the official documentation for more details.

1. You must enable managed identities for the cluster using the --enable-managed-identities flag with either the az aks create or az aks update commands
2. You must attach the ACR to the AKS cluster using the --attach-acr with either the az aks create or az aks update commands. See here for more details
3. You must set the AZURE_CLIENT_ID environment variable to the managed identity's client ID.
4. You must set the AZURE_TENANT_ID environment variable to the Azure tenant the managed identity resides in.

These will detected by the Azure credential manager.

When you create a cluster that has managed identities enabled, a user assigned managed identity called <AKS cluster name>-agentpool. Use this identity's client ID when setting AZURE_CLIENT_ID. Make sure the ACR is attached to your cluster.

Installing Policy Controller locally from this repository

If you are deploying policy-controller directly from this repository with make ko-apply, you will need to add AZURE_CLIENT_ID and AZURE_TENANT_ID to the list of environment variables in the webhook deployment configuration.

Installing Policy Controller from the Helm chart

You can provide the managed identity's client ID as a custom environment variable when installing the Helm chart:

helm install policy-controller sigstore/policy-controller --version 0.9.0 \
--set webhook.env.AZURE_CLIENT_ID=my-managed-id-client-id,webhook.env.AZURE_TENANT_ID=tenant-id

Service Principals for AKS Clusters

Installing Policy Controller from the Helm chart

You should be able to provide the service principal client ID and tenant ID as a workload identity annotations:

helm upgrade --install policy-controller sigstore/policy-controller --version 0.9.0 \
--set-json webhook.serviceAccount.annotations="{\"azure.workload.identity/client-id\": \"${SERVICE_PRINCIPAL_CLIENT_ID}\", \"azure.workload.identity/tenant-id\": \"${TENANT_ID}\"}"

Support Policy

This policy-controller's versions are able to run in the following versions of Kubernetes:

	policy-controller > 0.2.x	policy-controller > 0.10.x
Kubernetes 1.23	✓
Kubernetes 1.24	✓
Kubernetes 1.25	✓
Kubernetes 1.27		✓
Kubernetes 1.28		✓
Kubernetes 1.29		✓

note: not fully tested yet, but can be installed

Release Cadence

We are intending to move to a monthly cadence for minor releases. Minor releases will be published around the beginning of the month. We may cut a patch release instead, if the changes are small enough not to warrant a minor release. We will also cut patch releases periodically as needed to address bugs.

Security

Should you discover any security issues, please refer to Sigstore's security policy.