In Container Service for Kubernetes (ACK) Pro clusters, you can use keys that are created in Key Management Service (KMS) to encrypt Kubernetes Secrets. This topic describes how to use a key that is managed by KMS to encrypt Secrets for an ACK Pro cluster.

Prerequisites

  • A customer master key (CMK) is created in the KMS console. For more information, see Create a CMK.
    Note ACK Pro clusters support only CMKs of the Aliyun_AES_256 type.
  • After you enable Secret encryption, do not use the KMS API or the KMS console to disable or delete the CMK that is used to encrypt and decrypt Secrets, or create a schedule to delete the CMK. Otherwise, the API server becomes unavailable and cannot retrieve Secrets and service accounts. As a result, service interruptions occur.
  • Your Alibaba Cloud account is authorized to assume the AliyunCSManagedSecurityRole role. Otherwise, the system prompts you to perform the authorization when you enable Secret encryption.
  • If you log on to the console as a Resource Access Management (RAM) user or RAM role, you must make sure that the RAM user or RAM role has the AliyunKMSCryptoAdminAccess permission. For more information, see Grant permissions to a RAM user or RAM role.
  • You are charged by KMS for key management and API calls (on a per 10,000 calls basis). After Secret encryption is enabled for the ACK Pro cluster, kube-apiserver must call the encryption and decryption API operations of KMS to read and write Secrets. By default, a large number of API calls are made to read and write Secrets when you manage the lifecycle of service accounts in the cluster. If the cluster contains a large number of service accounts and Secrets, the cost of KMS API calls is high. Make sure that your account balance is sufficient. If you are not familiar with the pricing rules or your account balance is insufficient, you can disable Secret encryption for the cluster. For more information, see Disable Secret encryption for an existing ACK Pro cluster. If your account has been overdue for more than seven days, you cannot manage the cluster. For more information about KMS billing, see Billing.

Background information

Kubernetes Secrets are used to store and manage sensitive data, such as passwords of applications, Transport Layer Security (TLS) certificates, and credentials to download Docker images. Kubernetes stores Secrets in the etcd of a cluster. For more information, see Secrets.

ACK Pro clusters allow you to use a key created in KMS to encrypt Secrets. The KMS provider mechanism of Kubernetes is used during encryption. A KMS provider uses envelope encryption to encrypt and decrypt the keys of Secrets that are stored in etcd. Procedures of Secret encryption and decryption:
  • When you use a Kubernetes Secret to encrypt and store a password, the API server generates a random data encryption key (DEK) to encrypt the Secret. Then, the API server sends the DEK to KMS. KMS uses the specified key to encrypt the DEK and returns the encrypted DEK to the API server. The API server then stores the encrypted Secret and DEK in etcd.
  • When you decrypt the Kubernetes Secret, the system calls the Decrypt operation of KMS to decrypt the data key first. Then, the system uses the plaintext of the data key to decrypt the Kubernetes Secret and returns the decrypted Secret.

For more information, see KMS Encryption Provider mechanism and What is envelope encryption?.

Enable Secret encryption when you create an ACK Pro cluster

  1. Log on to the ACK console.
  2. In the left-side navigation pane of the ACK console, click Clusters.
  3. In the upper-right corner of the Clusters page, click Cluster Template.
  4. On the Select Cluster Template page, find Professional Managed Kubernetes Cluster and click Create to go to the Cluster Configurations wizard page.
  5. On the Managed Kubernetes tab, click Show Advanced Options at the bottom of the page. Then, find Secret Encryption, select Select Key, and select a key from the drop-down list. For more information about how to configure an ACK Pro cluster, see Create an ACK Pro cluster.
    选择KMS
    Log on to the ActionTrail console. In the left-side navigation pane, click Event Detail Query. On the Event Detail Query page, check for encryption and decryption operations that are performed by assuming the aliyuncsmanagedsecurityrole role. If these operations exist, the Secret encryption feature is enabled.

Enable Secret encryption for an existing ACK Pro cluster

  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, click the name of the ACK Pro cluster for which you want to enable Secret encryption.
  4. On the details page of the cluster, click the Basic Information tab. In the Basic Information section, turn on Secret Encryption.
    If this is the first time that you enable Secret encryption, follow the prompt and click Go to RAM console to navigate to the Cloud Resource Access Authorization page. Then, click Confirm Authorization Policy.
    Note
    • If you want to enable Secret encryption, the RAM user or RAM role that you use must be assigned one of the following role-based access control (RBAC) roles: the administrator role and O&M engineer role. For more information, see Assign RBAC roles to RAM users or RAM roles.
    • If you want to assign the aliyuncsmanagedsecurityrole role, make sure that you log on to the ACK console with an Alibaba Cloud account or the RAM user or RAM role that has the RAM management permissions.
  5. In the Secret Encryption dialog box, select an existing key. Click OK.
    If no key is available, click create keys to create a key in the KMS console. For more information, see Create a CMK.
    If the status of the cluster changes from Updating to Running, the Secret encryption feature is enabled for the cluster.

Disable Secret encryption for an existing ACK Pro cluster

  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, click the name of the ACK Pro cluster for which you want to disable Secret encryption.
  4. On the details page of the cluster, click the Basic Information tab. In the Basic Information section, turn off Secret Encryption.
    Note If you log on to the ACK console as a RAM user, make sure that the RAM user is assigned the following RBAC roles: the administrator role or O&M engineer role. For more information, see Assign RBAC roles to RAM users or RAM roles.
    If the status of the cluster changes from Updating to Running, the Secret encryption feature is disabled for the cluster.

Use automatic key rotation to encrypt Secrets

You can use the automatic key rotation feature provided by KMS to encrypt Secrets. When a key is being automatically rotated, the old key version is used to encrypt the existing Secrets in your cluster. For more information, see Automatic key rotation.

To force the system to use the new key version to encrypt existing Secrets, run the following command after the key is rotated: 

kubectl get secrets --all-namespaces -o json  kubectl annotate --overwrite -f - encryption-key-rotation-time="TIME"
Note Replace TIME with the string that indicates when the key rotation was performed, for example, 20220101-010101.