Chapter 13. OCI Support and Red Hat Quay

Helm, as a graduated project of the Cloud Native Computing Foundation (CNCF), has become the de facto package manager for Kubernetes as it simplifies how applications are packaged and deployed. Helm uses a packaging format called Charts which contain the Kubernetes resources representing an application. Charts can be made available for general distribution and consumption in repositories. A Helm repository is an HTTP server that serves an index.yaml metadata file and optionally a set of packaged charts. Beginning with Helm version 3, support was made available for distributing charts in OCI registries as an alternative to a traditional repository.

Support for Helm is now supported under the FEATURE_GENERAL_OCI_SUPPORT property. If you need to explicitly enable the feature, for example, if it has previously been disabled or if you have upgraded from a version where it is not enabled by default, you need to add two properties in the Quay configuration to enable the use of OCI artifacts:

FEATURE_GENERAL_OCI_SUPPORT: true
FEATURE_HELM_OCI_SUPPORT: true

Cosign is a tool that can be used to sign and verify container images. It uses the ECDSA-P256 signature algorithm and Red Hat’s Simple Signing payload format to create public keys that are stored in PKIX files. Private keys are stored as encrypted PEM files.

Cosign currently supports the following:

If you have Go 1.16+, you can directly install cosign with the following command:

$ go install github.com/sigstore/cosign/cmd/cosign@v1.0.0
go: downloading github.com/sigstore/cosign v1.0.0
go: downloading github.com/peterbourgon/ff/v3 v3.1.0
...

Next, generate a keypair:

$ cosign generate-key-pair
Enter password for private key:
Enter again:
Private key written to cosign.key
Public key written to cosign.pub

Sign the keypair with the following command:

$ cosign sign -key cosign.key quay-server.example.com/user1/busybox:test
Enter password for private key:
Pushing signature to: quay-server.example.com/user1/busybox:sha256-ff13b8f6f289b92ec2913fa57c5dd0a874c3a7f8f149aabee50e3d01546473e3.sig

Some users may experience the following error:

error: signing quay-server.example.com/user1/busybox:test: getting remote image: GET https://quay-server.example.com/v2/user1/busybox/manifests/test: UNAUTHORIZED: access to the requested resource is not authorized; map[]

Because cosign relies on ~/.docker/config.json for authorization, you might need to execute the following command:

$ podman login --authfile ~/.docker/config.json quay-server.example.com
Username:
Password:
Login Succeeded!

You can see the updated authorization configuration using the following command:

$ cat ~/.docker/config.json
{
	"auths": {
		"quay-server.example.com": {
			"auth": "cXVheWFkbWluOnBhc3N3b3Jk"
		}
	}

Helm, cosign, and ztsd compression scheme artifacts are built into Red Hat Quay 3.6 by default. For any other OCI media type that is not supported by default, you can add them to the ALLOWED_OCI_ARTIFACT_TYPES configuration in Quay’s config.yaml using the following format:

ALLOWED_OCI_ARTIFACT_TYPES:
  <oci config type 1>:
  - <oci layer type 1>
  - <oci layer type 2>

  <oci config type 2>:
  - <oci layer type 3>
  - <oci layer type 4>
...

For example, you can add Singularity (SIF) support by adding the following to your config.yaml:

...
ALLOWED_OCI_ARTIFACT_TYPES:
  application/vnd.oci.image.config.v1+json:
  - application/vnd.dev.cosign.simplesigning.v1+json
  application/vnd.cncf.helm.config.v1+json:
  - application/tar+gzip
  application/vnd.sylabs.sif.config.v1+json:
  - application/vnd.sylabs.sif.layer.v1+tar
...

If you want to disable OCI artifact support, you can set FEATURE_GENERAL_OCI_SUPPORT to False in your config.yaml:

...
FEATURE_GENERAL_OCI_SUPPORT = False
...