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Version: 0.6

Workload deployment

The following instructions will guide you through the process of making an existing Kubernetes deployment confidential and deploying it together with Contrast.

A running CoCo-enabled cluster is required for these steps, see the setup guide on how to set it up.

Deploy the Contrast runtime​

Contrast depends on a custom Kubernetes RuntimeClass (contrast-cc), which needs to be installed in the cluster prior to the Coordinator or any confidential workloads. This consists of a RuntimeClass resource and a DaemonSet that performs installation on worker nodes. This step is only required once for each version of the runtime. It can be shared between Contrast deployments.

kubectl apply -f https://github.com/edgelesssys/contrast/releases/latest/download/runtime.yml

Deploy the Contrast Coordinator​

Install the latest Contrast Coordinator release, comprising a single replica deployment and a LoadBalancer service, into your cluster.

kubectl apply -f https://github.com/edgelesssys/contrast/releases/latest/download/coordinator.yml

Prepare your Kubernetes resources​

Your Kubernetes resources need some modifications to run as Confidential Containers. This section guides you through the process and outlines the necessary changes.

RuntimeClass and Initializer​

Contrast will add annotations to your Kubernetes YAML files. If you want to keep the original files unchanged, you can copy the files into a separate local directory. You can also generate files from a Helm chart or from a Kustomization.

mkdir resources
kustomize build $MY_RESOURCE_DIR > resources/all.yml

To specify that a workload (pod, deployment, etc.) should be deployed as confidential containers, add runtimeClassName: contrast-cc to the pod spec (pod definition or template). This is a placeholder name that will be replaced by a versioned runtimeClassName when generating policies. In addition, add the Contrast Initializer as initContainers to these workloads and configure the workload to use the certificates written to a volumeMount named tls-certs.

spec: # v1.PodSpec
  runtimeClassName: contrast-cc
  initContainers:
  - name: initializer
    image: "ghcr.io/edgelesssys/contrast/initializer:latest"
    env:
    - name: COORDINATOR_HOST
      value: coordinator
    volumeMounts:
    - name: tls-certs
      mountPath: /tls-config
  volumes:
  - name: tls-certs
    emptyDir: {}

Handling TLS​

The initializer populates the shared volume with X.509 certificates for your workload. These certificates are used by the Contrast Service Mesh, but can also be used by your application directly. The following tab group explains the setup for both scenarios.

Contrast can be configured to handle TLS in a sidecar container. This is useful for workloads that are hard to configure with custom certificates, like Java applications.

Configuration of the sidecar depends heavily on the application. The following example is for an application with these properties:

  • The app has a main application at TCP port 8001, which should be TLS-wrapped and doesn't require client authentication.
  • The app has a metrics endpoint at TCP port 8080, which should be accessible in plain text.
  • All other endpoints require client authentication.
  • The app connects to a Kubernetes service backend.default:4001, which requires client authentication.

Add the following sidecar definition to your workload:

spec: # v1.PodSpec
  initContainers:
  - name: tls-sidecar
    image: "ghcr.io/edgelesssys/contrast/service-mesh-proxy:latest"
    restartPolicy: Always
    env:
    - name: EDG_INGRESS_PROXY_CONFIG
      value: "main#8001#false##metrics#8080#true"
    - name: EDG_EGRESS_PROXY_CONFIG
      value: "backend#127.0.0.2:4001#backend.default:4001"
    volumeMounts:
    - name: tls-certs
      mountPath: /tls-config

The only change required to the app itself is to let it connect to 127.0.0.2:4001 to reach the backend service. You can find more detailed documentation in the Service Mesh chapter.

Generate policy annotations and manifest​

Run the generate command to generate the execution policies and add them as annotations to your deployment files. A manifest.json with the reference values of your deployment will be created.

contrast generate resources/
warning

Please be aware that runtime policies currently have some blind spots. For example, they can't guarantee the starting order of containers. See the current limitations for more details.

Apply the resources​

Apply the resources to the cluster. Your workloads will block in the initialization phase until a manifest is set at the Coordinator.

kubectl apply -f resources/

Connect to the Contrast Coordinator​

For the next steps, we will need to connect to the Coordinator. The released Coordinator resource includes a LoadBalancer definition we can use.

coordinator=$(kubectl get svc coordinator -o=jsonpath='{.status.loadBalancer.ingress[0].ip}')
Port-forwarding of Confidential Containers

kubectl port-forward uses a Container Runtime Interface (CRI) method that isn't supported by the Kata shim. If you can't use a public load balancer, you can deploy a port-forwarder. The port-forwarder relays traffic from a CoCo pod and can be accessed via kubectl port-forward.

Upstream tracking issue: https://github.com/kata-containers/kata-containers/issues/1693.

Set the manifest​

Attest the Coordinator and set the manifest:

contrast set -c "${coordinator}:1313" resources/

After this step, the Coordinator will start issuing TLS certs to the workloads. The init container will fetch a certificate for the workload and the workload is started.

Verify the Coordinator​

An end user (data owner) can verify the Contrast deployment using the verify command.

contrast verify -c "${coordinator}:1313"

The CLI will attest the Coordinator using embedded reference values. The CLI will write the service mesh root certificate and the history of manifests into the verify/ directory. In addition, the policies referenced in the manifest are also written to the directory.

Communicate with workloads​

You can securely connect to the workloads using the Coordinator's mesh-ca.pem as a trusted CA certificate. First, expose the service on a public IP address via a LoadBalancer service:

kubectl patch svc ${MY_SERVICE} -p '{"spec": {"type": "LoadBalancer"}}'
kubectl wait --timeout=30s --for=jsonpath='{.status.loadBalancer.ingress}' service/${MY_SERVICE}
lbip=$(kubectl get svc ${MY_SERVICE} -o=jsonpath='{.status.loadBalancer.ingress[0].ip}')
echo $lbip
Subject alternative names and LoadBalancer IP

By default, mesh certificates are issued with a wildcard DNS entry. The web frontend is accessed via load balancer IP in this demo. Tools like curl check the certificate for IP entries in the SAN field. Validation fails since the certificate contains no IP entries as a subject alternative name (SAN). For example, a connection attempt using the curl and the mesh CA certificate with throw the following error:

$ curl --cacert ./verify/mesh-ca.pem "https://${frontendIP}:443"
curl: (60) SSL: no alternative certificate subject name matches target host name '203.0.113.34'

Using openssl, the certificate of the service can be validated with the mesh-ca.pem:

openssl s_client -CAfile verify/mesh-ca.pem -verify_return_error -connect ${frontendIP}:443 < /dev/null