Sealed Secrets

Sealed secrets allow confidential information to be stored in the untrusted control plane. Like normal Kubernetes secrets, sealed secrets are orchestrated by the control plane and are transparently provisioned to your workload as environment variables or volumes.

Basic Usage

Here’s how you create a vault secret. There are also envelope secrets, which are described later. Vault secrets are a pointer to resource stored in a KBS, while envelope secrets are wrapped secrets that are unwrapped with a KMS.

Creating a sealed secret

There is a helper tool for sealed secrets in the Guest Components repository.

Clone the repository.

git clone https://github.com/confidential-containers/guest-components.git

Inside the guest-components directory, you can build and run the tool with Cargo.

cargo run -p confidential-data-hub --bin secret

With the tool you can create a secret.

cargo run -p confidential-data-hub --bin secret seal vault --resource-uri kbs:///your/secret/here --provider kbs

A vault secret is fulfilled by retrieving a secret from a KBS inside the guest. The locator of your secret is specified by resource-uri.

This command should return a base64 string which you will use in the next step.

Adding a sealed secret to Kubernetes

Create a secret from your secret string using kubectl.

kubectl create secret generic sealed-secret --from-literal='secret=sealed.fakejwsheader.ewogICAgInZlcnNpb24iOiAiMC4xLjAiLAogICAgInR5cGUiOiAidmF1bHQiLAogICAgIm5hbWUiOiAia2JzOi8vL2RlZmF1bHQvc2VhbGVkLXNlY3JldC90ZXN0IiwKICAgICJwcm92aWRlciI6ICJrYnMiLAogICAgInByb3ZpZGVyX3NldHRpbmdzIjoge30sCiAgICAiYW5ub3RhdGlvbnMiOiB7fQp9Cg==.fakesignature'

When using --from-literal you provide a mapping of secret keys and values. The secret value should be the string generated in the previous step. The secret key can be whatever you want, but make sure to use the same one in future steps. This is separate from the name of the secret.

Deploying a sealed secret to a confidential workload

You can add your sealed secret to a workload yaml file.

You can expose your sealed secret as an environment variable.

apiVersion: v1
kind: Pod
metadata:
  name: sealed-secret-pod
spec:
  runtimeClassName: kata-qemu-coco-dev
  containers:
  - name: busybox
    image: quay.io/prometheus/busybox:latest
    imagePullPolicy: Always
    command: ["echo", "$PROTECTED_SECRET"]
    env:
    - name: PROTECTED_SECRET
      valueFrom:
        secretKeyRef:
          name: sealed-secret
          key: secret

You can also expose your secret as a volume.

apiVersion: v1
kind: Pod
metadata:
  name: secret-test-pod-cc
spec:
  runtimeClassName: kata
  containers:
  - name: busybox
    image: quay.io/prometheus/busybox:latest
    imagePullPolicy: Always
    command: ["cat", "/sealed/secret-value/secret"]
    volumeMounts:
        - name: sealed-secret-volume
          mountPath: "/sealed/secret-value"
  volumes:
    - name: sealed-secret-volume
      secret:
        secretName: sealed-secret

Advanced

Envelope Secrets

You can also create envelope secrets. With envelope secrets, the secret itself is included in the secret (unlike a vault secret, which is just a pointer to a secret). In an envelope secret, the secret value is wrapped and can be unwrapped by a KMS. This allows us to support models where the key for unwrapping secrets never leaves the KMS. It also decouples the secret from the KBS.

We currently support two KMSes for envelope secrets. See specific instructions for aliyun kms and eHSM.