GitHub Managed Policy Controller

This repository hosts a temporary GitHub owned fork of the Sigstore Policy Controller repository. Once functionality only present in this fork is merged upstream to sigstore/policy-controller, this fork will be archived.

The policy-controller admission controller can be used to enforce policy on a Kubernetes cluster based on verifiable supply-chain metadata from cosign and artifacts attestations produced by the attest-build-provenance GitHub Action.

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

Background

See the official documentation on using artifact attestations to establish build provenance and the blog post introducing Artifact Attestations.

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)

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 oci://ghcr.io/artifact-attestations-helm-charts/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 install policy-controller oci://ghcr.io/artifact-attestations-helm-charts/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}\"}"

License

This project is licensed under the terms of the Apache 2.0 open source license. Please refer to Apache 2.0 for the full terms.

Maintainers

See CODEOWNERS for a list of maintainers.

Support

If you have any questions or issues following examples outlined in this repository, please file an issue and we will assist you.

K8s 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

Security

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

Maintainer Documentation

Cutting a new release

The branch release on the private fork is used for customer-facing released code.

In order to push a new release, follow these steps:

1. Merge any changes into the release branch.
2. Tag as v0.9.0+githubX (incrementing the X as needed).
3. Push the tag to the private fork.
4. The Release GitHub Action workflow will triggered automatically when the tag is pushed