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 and click Clusters in the left-side navigation pane.
  2. On the Clusters page, click the name of a cluster and choose Operations > Add-ons in the left-side navigation pane.
  3. In the left-side navigation pane, choose Operations > Add-ons.
  4. On the Add-ons page, click the Security tab, find kritis-validation-hook, and then click Install.
  5. 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 top navigation bar, select the region in which you want to create a CMK.
  3. In the left-side navigation pane, click Keys.
  4. Click Create Key. In the dialog box that appears, configure the parameters.
    For more information about the parameters, see Create a CMK.
    Important Select RSA_2048 from the Key Spec drop-down list and Sign/Verify from the Purpose drop-down list.
  5. Click Advanced and configure the Key Material Source parameter.
    Note The Advanced option appears only when you set the Key Spec parameter to Aliyun_AES_256 or Aliyun_SM4.
    • Alibaba Cloud KMS: KMS generates key material.
    • External: You must import key material from an external source. For more information, see Import key material.
      Note If you select External, you must select I understand the implications of using the external key materials key.
  6. Click Determine.

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 Protection Configuration > Container Protection > Container Signature.
  3. On the Witness tab, click Create a witness. After you configure the parameters, click OK to create a witness.
    ParameterDescription
    WitnessEnter the name of the witness. When you configure a security policy, you must select a witness to enable the container signature feature for the required container. We recommend that you enter an informative name.
    Select a certificateSelect the KMS CMK that you created from the certificate list.
    DescriptionEnter the description of the witness.

Step 4: Enable image signing in Container Registry

  1. Log on to the Container Registry console . In the top navigation bar, select a region.
  2. In the left-side navigation pane, click Instances.
  3. On the Instances page, find the Enterprise Edition instance that you want to manage and click the instance name or click Manage.
  4. 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.
  5. 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 Security and 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 Protection Configuration > Container Protection > Container Signature.
  3. On the Security Policy tab, click Add Policy. After you configure the parameters, click OK.
    ParameterDescription
    Policy NameEnter the name of the security policy. When you configure a security policy, you must select a witness to enable the container feature for the required cluster.

    We recommend that you enter an informative name.

    WitnessSelect the witness that you created from the witness list.
    Application ClusterSelect the cluster group for which you want to enable the container signature feature. Then, select the required Cluster Namespace.
    Policy EnabledTurn on the switch. The policy is automatically enabled after it is created.
    Note The switch is turned off by default. In this case, the policy does not take effect after it is created.
    NoteEnter the description of the security policy.

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

References