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Using Tekton Chains for OpenShift Pipelines supply chain security

Tekton Chains is a Technology Preview feature only. Technology Preview features are not supported with Red Hat production service level agreements (SLAs) and might not be functionally complete. Red Hat does not recommend using them in production. These features provide early access to upcoming product features, enabling customers to test functionality and provide feedback during the development process.

For more information about the support scope of Red Hat Technology Preview features, see https://access.redhat.com/support/offerings/techpreview/.

Tekton Chains is a Kubernetes Custom Resource Definition (CRD) controller. You can use it to manage the supply chain security of the tasks and pipelines created using Red Hat OpenShift Pipelines.

By default, Tekton Chains observes all task run executions in your OpenShift Container Platform cluster. When the task runs complete, Tekton Chains takes a snapshot of the task runs. It then converts the snapshot to one or more standard payload formats, and finally signs and stores all artifacts.

To capture information about task runs, Tekton Chains uses the Result and PipelineResource objects. When the objects are unavailable, Tekton Chains the URLs and qualified digests of the OCI images.

The PipelineResource object is deprecated and will be removed in a future release; for manual use, the Results object is recommended.

Key features

  • You can sign task runs, task run results, and OCI registry images with cryptographic key types and services such as cosign.

  • You can use attestation formats such as in-toto.

  • You can securely store signatures and signed artifacts using OCI repository as a storage backend.

Installing Tekton Chains using the Red Hat OpenShift Pipelines Operator

Cluster administrators can use the TektonChain custom resource (CR) to install and manage Tekton Chains.

Tekton Chains is an optional component of Red Hat OpenShift Pipelines. Currently, you cannot install it using the TektonConfig CR.
Prerequisites

  • Ensure that the Red Hat OpenShift Pipelines Operator is installed in the openshift-pipelines namespace on your cluster.

Procedure

  1. Create the TektonChain CR for your OpenShift Container Platform cluster.

    apiVersion: operator.tekton.dev/v1alpha1
kind: TektonChain
metadata:
  name: chain
spec:
  targetNamespace: openshift-pipelines

  2. Apply the TektonChain CR.

    $ oc apply -f TektonChain.yaml (1)
    1 Substitute with the file name of the TektonChain CR.

  3. Check the status of the installation.

    $ oc get tektonchains.operator.tekton.dev

Configuring Tekton Chains

Tekton Chains uses a ConfigMap object named chains-config in the openshift-pipelines namespace for configuration.

To configure Tekton Chains, use the following example:

Example: Configuring Tekton Chains
$ oc patch configmap chains-config -n openshift-pipelines -p='{"data":{"artifacts.oci.storage": "", "artifacts.taskrun.format":"tekton", "artifacts.taskrun.storage": "tekton"}}' (1)
1 Use a combination of supported key-value pairs in the JSON payload.

Supported keys for Tekton Chains configuration

Cluster administrators can use various supported keys and values to configure specifications about task runs, OCI images, and storage.

Supported keys for task run

Table 1. Chains configuration: Supported keys for task run
Supported keys Description Supported values Default values

artifacts.taskrun.format

The format to store task run payloads.

tekton, in-toto

tekton

artifacts.taskrun.storage

The storage backend for task run signatures. You can specify multiple backends as a comma-separated list, such as “tekton,oci”. To disable this artifact, provide an empty string “”.

tekton, oci

tekton

artifacts.taskrun.signer

The signature backend to sign task run payloads.

x509

x509

Supported keys for OCI

Table 2. Chains configuration: Supported keys for OCI
Supported keys Description Supported values Default values

artifacts.oci.format

The format to store OCI payloads.

simplesigning

simplesigning

artifacts.oci.storage

The storage backend to for OCI signatures. You can specify multiple backends as a comma-separated list, such as “oci,tekton”. To disable the OCI artifact, provide an empty string “”.

tekton, oci

oci

artifacts.oci.signer

The signature backend to sign OCI payloads.

x509, cosign

x509

Supported keys for storage

Table 3. Chains configuration: Supported keys for storage
Supported keys Description Supported values Default values

artifacts.oci.repository

The OCI repository to store OCI signatures.

Currently, Chains support only the internal OpenShift OCI registry; other popular options such as Quay is not supported.

Signing secrets in Tekton Chains

Cluster administrators can generate a key pair and use Tekton Chains to sign artifacts using a Kubernetes secret. For Tekton Chains to work, a private key and a password for encrypted keys must exist as part of the signing-secrets Kubernetes secret, in the openshift-pipelines namespace.

Currently, Tekton Chains supports the x509 and cosign signature schemes.

Use only one of the supported signature schemes.

Signing using x509

To use the x509 signing scheme with Tekton Chains, store the x509.pem private key of the ed25519 or ecdsa type in the signing-secrets Kubernetes secret. Ensure that the key is stored as an unencrypted PKCS8 PEM file (BEGIN PRIVATE KEY).

Signing using cosign

To use the cosign signing scheme with Tekton Chains:

  1. Install cosign.

  2. Generate the cosign.key and cosign.pub key pairs.

    $ cosign generate-key-pair k8s://openshift-pipelines/signing-secrets

    Cosign prompts you for a password, and creates a Kubernetes secret.

  3. Store the encrypted cosign.key private key and the cosign.password decryption password in the signing-secrets Kubernetes secret. Ensure that the private key is stored as an encrypted PEM file of the ENCRYPTED COSIGN PRIVATE KEY type.

Troubleshooting signing

If the signing secrets are already populated, you might get the following error:

Error from server (AlreadyExists): secrets "signing-secrets" already exists

To resolve the error:

  1. Delete the secrets:

    $ oc delete secret signing-secrets -n openshift-pipelines

  2. Recreate the key pairs and store them in the secrets using your preferred signing scheme.

Authenticating to an OCI registry

Before pushing signatures to an OCI registry, cluster administrators must configure Tekton Chains to authenticate with the registry. The Tekton Chains controller uses the same service account under which the task runs execute. To set up a service account with the necessary credentials for pushing signatures to an OCI registry, perform the following steps:

Procedure

  1. Set the namespace and name of the Kubernetes service account.

    $ export NAMESPACE=<namespace> (1)
$ export SERVICE_ACCOUNT_NAME=<service_account> (2)
    1 The namespace associated with the service account.
    2 The name of the service account.

  2. Create a Kubernetes secret.

    $ oc create secret registry-credentials \
  --from-file=.dockerconfigjson \ (1)
  --type=kubernetes.io/dockerconfigjson \
  -n $NAMESPACE
    1 Substitute with the path to your Docker config file. Default path is ~/.docker/config.json.

  3. Give the service account access to the secret.

    $ oc patch serviceaccount $SERVICE_ACCOUNT_NAME \
  -p "{\"imagePullSecrets\": [{\"name\": \"registry-credentials\"}]}" -n $NAMESPACE

    If you patch the default pipeline service account that Red Hat OpenShift Pipelines assigns to all task runs, the Red Hat OpenShift Pipelines Operator will override the service account. As a best practice, you can perform the following steps:

    1. Create a separate service account to assign to user’s task runs.

      $ oc create serviceaccount <service_account_name>

    2. Associate the service account to the task runs by setting the value of the serviceaccountname field in the task run template.

      apiVersion: tekton.dev/v1beta1
kind: TaskRun
metadata:
name: build-push-task-run-2
spec:
serviceAccountName: build-bot (1)
taskRef:
  name: build-push
...
      1 Substitute with the name of the newly created service account.

Creating and verifying task run signatures without any additional authentication

To verify signatures of task runs using Tekton Chains with any additional authentication, p