confidential-containers/guides/coco-dev.md

Running a workload

Creating a sample CoCo workload

Once you've used the operator to install Confidential Containers, you can run a pod with CoCo by simply adding a runtime class. First, we will use the kata-qemu-coco-dev runtime class which uses CoCo without hardware support. Initially we will try this with an unencrypted container image.

In this example, we will be using the bitnami/nginx image as described in the following yaml:

apiVersion: v1
kind: Pod
metadata:
  labels:
    run: nginx
  name: nginx
  annotations:
    io.containerd.cri.runtime-handler: kata-qemu-coco-dev
spec:
  containers:
  - image: bitnami/nginx:1.22.0
    name: nginx
  dnsPolicy: ClusterFirst
  runtimeClassName: kata-qemu-coco-dev

Setting the runtimeClassName is usually the only change needed to the pod yaml, but some platforms support additional annotations for configuring the enclave. See the guides for more details.

With Confidential Containers, the workload container images are never downloaded on the host. For verifying that the container image doesn’t exist on the host, you should log into the k8s node and ensure the following command returns an empty result:

root@cluster01-master-0:/home/ubuntu# crictl -r unix:///run/containerd/containerd.sock image ls | grep bitnami/nginx

You will run this command again after the container has started.

Create a pod YAML file as previously described (we named it nginx.yaml) .

Create the workload:

kubectl apply -f nginx.yaml

Output:

pod/nginx created

Ensure the pod was created successfully (in running state):

kubectl get pods

Output:

NAME    READY   STATUS    RESTARTS   AGE
nginx   1/1     Running   0          3m50s

Now go back to the k8s node and ensure that you don’t have any bitnami/nginx images on it:

root@cluster01-master-0:/home/ubuntu# crictl  -r  unix:///run/containerd/containerd.sock image ls | grep bitnami/nginx

Encrypted and/or signed images with attestation

The previous example does not involve any attestation because the workload container isn't signed or encrypted, and the workload itself does not require any secrets.

This is not the case for most real workloads. It is recommended to use CoCo with signed and/or encrypted images. The workload itself can also request secrets from the attestation agent in the guest.

Secrets are provisioned to the guest in conjunction with an attestation, which is based on hardware evidence. The rest of this guide focuses on setting up more substantial encrypted/signed workloads using attestation and confidential hardware.

CoCo has a modular attestation interface and there are a few options for attestation. CoCo provides a generic Key Broker Service (KBS) that the rest of this guide will be focused on.

Select Runtime Class

To use CoCo with confidential hardware, first switch to the appropriate runtime class. TDX has one runtime class, kata-qemu-tdx.

For SNP, use the kata-qemu-snp runtime class and follow the SNP guide.

For enclave-cc follow the enclave-cc guide.

Deploy and Configure tenant-side CoCo Key Broker System cluster

The following describes how to run and provision the generic KBS. The KBS should be run in a trusted environment. The KBS is not just one service, but a combination of several.

A tenant-side CoCo Key Broker System cluster includes:

• Key Broker Service (KBS): Brokering service for confidential resources.
• Attestation Service (AS): Verifier for remote attestation.
• Reference Value Provider Service (RVPS): Provides reference values for AS.
• CoCo Keyprovider: Component to encrypt the images following ocicrypt spec.

To quick start the KBS cluster, a docker compose yaml is provided to launch.

# Clone KBS git repository
git clone https://github.com/confidential-containers/trustee.git
cd trustee/kbs
export KBS_DIR_PATH=$(pwd)

# Generate a user auth key pair
openssl genpkey -algorithm ed25519 > config/private.key
openssl pkey -in config/private.key -pubout -out config/public.pub

cd ..

# Start KBS cluster
docker compose up -d

If configuration of KBS cluster is required, edit the following config files and restart the KBS cluster with docker compose:

• $KBS_DIR_PATH/config/kbs-config.toml: configuration for Key Broker Service.
• $KBS_DIR_PATH/config/as-config.json: configuration for Attestation Service.
• $KBS_DIR_PATH/config/sgx_default_qcnl.conf: configuration for Intel TDX/SGX verification. See details.

When KBS cluster is running, you can modify the policy file used by AS policy engine (OPA) at any time:

• $KBS_DIR_PATH/data/attestation-service/opa/default.rego: Policy file for evidence verification of AS, refer to AS Policy Engine for more infomation.

Encrypting an Image

skopeo is required to encrypt the container image. Follow the instructions to install skopeo. If building with Ubuntu 22.04, make sure to follow the instructions to build skopeo from source, otherwise there will be errors regarding version incompatibility between ocicrypt and skopeo. Make sure the downloaded skopeo version is at least 1.16.0. Ubuntu 22.04 builds skopeo with an outdated ocicrypt version, which does not support the keyprovider protocol we depend on.

Use skopeo to encrypt an image on the same node of the KBS cluster (use busybox:latest for example):

# edit ocicrypt.conf
tee > ocicrypt.conf <<EOF
{
    "key-providers": {
        "attestation-agent": {
            "grpc": "127.0.0.1:50000"
        }
    }
}
EOF

# encrypt the image
OCICRYPT_KEYPROVIDER_CONFIG=ocicrypt.conf skopeo copy --insecure-policy --encryption-key provider:attestation-agent docker://library/busybox oci:busybox:encrypted

The image will be encrypted, and things happens in the KBS cluster background include:

• CoCo Keyprovider generates a random key and a key-id. Then encrypts the image using the key.
• CoCo Keyprovider registers the key with key-id into KBS.

Then push the image to a registry:

skopeo copy oci:busybox:encrypted [SCHEME]://[REGISTRY_URL]:encrypted

Be sure to replace [SCHEME] with registry scheme type like docker, replace [REGISTRY_URL] with the desired registry URL like docker.io/encrypt_test/busybox.

Signing an Image

cosign is required to sign the container image. Follow the instructions here to install cosign:

To install cosign, find and unpackage the corresponding package to the machine being used from their release page.

Generate a cosign key pair and register the public key to KBS storage:

cosign generate-key-pair
mkdir -p $KBS_DIR_PATH/data/kbs-storage/default/cosign-key && cp cosign.pub $KBS_DIR_PATH/data/kbs-storage/default/cosign-key/1

Sign the encrypted image with cosign private key:

cosign sign --key cosign.key [REGISTRY_URL]:encrypted

Be sure to replace [REGISTRY_URL] with the desired registry URL of the encrypted image generated in previous steps.

Then edit an image pulling validation policy file. Here is a sample policy file security-policy.json:

{
    "default": [{"type": "reject"}],
    "transports": {
        "docker": {
            "[REGISTRY_URL]": [
                {
                    "type": "sigstoreSigned",
                    "keyPath": "kbs:///default/cosign-key/1"
                }
            ]
        }
    }
}

Be sure to replace [REGISTRY_URL] with the desired registry URL of the encrypted image.

Register the image pulling validation policy file to KBS storage:

mkdir -p $KBS_DIR_PATH/data/kbs-storage/default/security-policy
cp security-policy.json $KBS_DIR_PATH/data/kbs-storage/default/security-policy/test

Deploy an Encrypted Image as a CoCo workload on CC HW

Here is a sample yaml for encrypted image deploying:

cat << EOT | tee encrypted-image-test-busybox.yaml
apiVersion: v1
kind: Pod
metadata:
  labels:
    run: encrypted-image-test-busybox
  name: encrypted-image-test-busybox
  annotations:
    io.containerd.cri.runtime-handler: [RUNTIME_CLASS]
spec:
  containers:
  - image: [REGISTRY_URL]:encrypted
    name: busybox
  dnsPolicy: ClusterFirst
  runtimeClassName: [RUNTIME_CLASS]
EOT

Be sure to replace [REGISTRY_URL] with the desired registry URL of the encrypted image generated in previous step, replace [RUNTIME_CLASS] with kata runtime class for CC HW.

Then configure /opt/confidential-containers/share/defaults/kata-containers/configuration-<RUNTIME_CLASS_SUFFIX>.toml to add agent.aa_kbc_params=cc_kbc::<KBS_URI> to kernel parameters. Here RUNTIME_CLASS_SUFFIX is something like qemu-coco-dev, KBS_URI is the address of Key Broker Service in KBS cluster like http://123.123.123.123:8080.

Deploy encrypted image as a workload:

kubectl apply -f encrypted-image-test-busybox.yaml