This topic describes how to use Container Registry, Key Management Service (KMS), Security Center, and kritis-validation-hook to automatically verify the signatures of container images. This allows you to deploy only container images that have been signed by trusted authorities. This also reduces the risk of malicious code execution in your environment.

Step 1: Install kritis-validation-hook

  1. Log on to the ACK console.
  2. In the left-side navigation pane of the ACK console, click Clusters.
  3. On the Clusters page, find the cluster that you want to manage and click the name of the cluster or click Details in the Actions column. The details page of the cluster appears.
  4. In the left-side navigation pane, choose Operations > Add-ons.
  5. In the Security section of the Add-ons page, find kritis-validation-hook and click Install.
  6. Authorize your cluster to run kritis-validation-hook.

    You must grant your cluster the permissions to run kritis-validation-hook. For more information, see Authorize a cluster to access resources.

Step 2: Create a key that is used to sign images in the KMS console

  1. Log on to the KMS console.
  2. In the upper-left corner of the Keys page, click Create Key.
  3. In the Create Key dialog box, set Alias Name and Description.
Notice Select RSA_2048 from the Key Spec drop-down list and Sign/Verify from the Purpose drop-down list.
  1. Click Advanced and specify Key Material Source.
    • Alibaba Cloud KMS: Use KMS to generate key material.
    • External: Import key material from an external source. For more information about how to import key material, see Import key material.
      Note If you select External, you must also select I understand the implications of using the external key materials key.
  2. Click OK.

Step 3: Create a witness that uses the key in the Security Center console

  1. Log on to the Security Center console.
  2. In the left-side navigation pane, choose Operation > Container Signature.
  3. On the Witness tab, click Create a witness.
    Set the witness information. For more information, see Use the container signature feature.
  4. Click OK.

Step 4: Enable image signing in Container Registry

  1. Log on to the Container Registry console.
  2. On the Instances page, find the Enterprise Edition instance that you want to manage and click the instance name or click Manage.
  3. In the left-side navigation pane of the details page, choose Repository > Namespace.
    Create a namespace and enable image signing for images in the namespace. For more information, see Manage namespaces.
  4. Enable image signing for the created namespace.

    When you create signature signing rules, select the witness that you created in Step 3.

    1. In the left-side navigation pane, choose Content Trust > Image Signature.
    2. On the Image Signature tab, click Create a signature rule.
      For more information about how to configure signature signing rules, see Configure a signature rule for automatic image signing.

Step 5: Enable signature verification in Security Center

To enable signature verification for a namespace, add and enable a security policy for the cluster in the Security Center console.

  1. Log on to the Security Center console.
  2. In the left-side navigation pane, choose Operation > Container Signature.
  3. On the Security Policy tab, click Add Policy.
    For more information about how to add a security policy, see Create a security policy. Signature verification
  4. Click OK.

Step 6: Check whether signature verification is enabled

Note Only images in digest format are supported.

Run the following command to check whether signature verification is enabled:

  • After signature verification is enabled for the default namespace, unsigned images cannot be deployed in the namespace.
    To specify an image by tag, run the following command:
    kubectl -n default create deployment not-sign --image=alpine:3.11 -- sleep 10
    Error from server: admission webhook "kritis-validation-hook-deployments.grafeas.io" denied the request: image alpine:3.11 is not attested
    To specify an image by digest, run the following command:
    kubectl -n default create deployment not-sign --image=alpine@sha256:ddba4d27a7ffc3f86dd6c2f92041af252a1f23a8e742c90e6e1297bfa1bc0c45 -- sleep 10
    Error from server: admission webhook "kritis-validation-hook-deployments.grafeas.io" denied the request: image alpine@sha256:ddba4d27a7ffc3f86dd6c2f92041af252a1f23a8e742c90e6e1297bfa1bc0c45 is not attested
  • Push an image to a namespace where image signature signing is enabled. Then, verify that the image can be deployed after the image is signed.
    docker push kritis-demo-registry-vpc.cn-hongkong.cr.aliyuncs.com/kritis-demo/alpine:3.11
    The push refers to repository [kritis-demo-registry-vpc.cn-hongkong.cr.aliyuncs.com/kritis-demo/alpine]
    5216338b40a7: Pushed
    3.11: digest: sha256:ddba4d27a7ffc3f86dd6c2f92041af252a1f23a8e742c90e6e1297bfa1bc0c45 size: 528
    To accept requests to deploy signed images, run the following command:
    kubectl -n default create deployment is-signed --image=kritis-demo-registry-vpc.cn-hongkong.cr.aliyuncs.com/kritis-demo/alpine@sha256:ddba4d27a7ffc3f86dd6c2f92041af252a1f23a8e742c90e6e1297bfa1bc0c45 -- sleep 10
    deployment.apps/is-signed created