CMEK organization policies

Preview

This feature is covered by the Pre-GA Offerings Terms of the Google Cloud Terms of Service. Pre-GA features might have limited support, and changes to pre-GA features might not be compatible with other pre-GA versions. For more information, see the launch stage descriptions.

Google Cloud offers two organization policy constraints to help ensure CMEK usage across an organization:

• constraints/gcp.restrictNonCmekServices is used to require CMEK protection.
• constraints/gcp.restrictCmekCryptoKeyProjects is used to limit which Cloud KMS keys are used for CMEK protection.

CMEK organization policies only apply to newly created resources within supported Google Cloud services.

Require CMEK protection

To require CMEK protection for your organization, configure the constraints/gcp.restrictNonCmekServices organization policy.

As a list constraint, the accepted values for this constraint are Google Cloud service names (for example, sqladmin.googleapis.com). By configuring a list of Google Cloud service names and setting the constraint to Deny, you can reject resource creation that does not use CMEK in the configured services. In other words, requests to create a resource in the service do not succeed without specifying a Cloud KMS key. This constraint can only be applied to Supported services.

Caution: The creation of some Google Cloud resource types may trigger the creation of a resource type from a different service. Use caution when configuring this constraint in an environment with services that do not support CMEK. Requiring CMEK protection for a service that is CMEK-aware may prevent a CMEK-unaware service from creating resources and disrupt normal functionality.

Limit the use of Cloud KMS keys for CMEK

To limit which Cloud KMS keys are used for CMEK protection, configure the constraints/gcp.restrictCmekCryptoKeyProjects constraint.

As a list constraint, the accepted values are resource hierarchy indicators (for example, projects/PROJECT_ID, under:folders/FOLDER_ID, and under:organizations/ORGANIZATION_ID). By configuring a list of resource hierarchy indicators and setting the constraint to Allow, you can restrict supported services to only allow keys to be used from the listed projects, folders, and organizations for CMEK protection. Requests to create a CMEK protected resource in configured services do not succeed without specifying a Cloud KMS key from one of the allowed projects, folders, or organizations. Where configured, this constraint applies to all Supported services.

Supported services

Service	Constraint value when requiring CMEK
Cloud Bigtable	bigtable.googleapis.com
Cloud Composer	composer.googleapis.com
Compute Engine	compute.googleapis.com
Google Kubernetes Engine	container.googleapis.com
Dataflow	dataflow.googleapis.com
Cloud Logging	logging.googleapis.com
Pub/Sub	pubsub.googleapis.com
Cloud Spanner	spanner.googleapis.com
Cloud SQL	sqladmin.googleapis.com
Cloud Storage	storage.googleapis.com

Enforcement exceptions by resource type

CMEK organization policy constraints are enforced when creating a new resource or when changing (where supported) the Cloud KMS key on an existing resource. Generally, they are enforced on all of a service's resource types that support CMEK and based solely on the resource's configuration. Some notable exceptions are summarized here:

Resource type	Enforcement exception
compute.googleapis.com/Instance	Enforced based on configured boot disk
logging.googleapis.com/LogBucket	Enforced on explicitly created log buckets; see also separate configuration required to ensure compliance of built-in log buckets
storage.googleapis.com/Bucket	(Preview) Enforcement is on bucket default Cloud KMS key; enforced when updating bucket default Cloud KMS key; enforced when creating a bucket through Google Cloud console
storage.googleapis.com/Object	Enforced independently of bucket; see also separate configuration of bucket default Cloud KMS key

Configuration examples

In the configuration examples, assume the sample organization has the following resource hierarchy:

Note: CMEK organization policies only apply to newly created resources within supported services.

Require CMEK and limit keys for a project

Suppose you want to require CMEK protection for all Cloud Storage resources under projects/5 and ensure that only keys coming from projects/4 can be used.

To require CMEK protection for all new Cloud Storage resources, use the following organization policy setting:

• Organization policy: constraints/gcp.restrictNonCmekServices
• Binding at: projects/5
• Policy type: Deny
• Policy value: storage.googleapis.com

To ensure only keys from projects/4 are used, use the following configuration:

• Organization policy: constraints/gcp.restrictCmekCryptoKeyProjects
• Binding at: projects/5
• Policy type: Allow
• Policy value: projects/4

Require CMEK and limit keys to within a folder

Alternatively, suppose you're expecting to add additional Cloud KMS projects under folders/2 in the future and want to require CMEK more broadly within folders/3. For this scenario, you need slightly different configurations.

To require additional CMEK protection for new Cloud SQL and Cloud Storage resources anywhere under folders/3:

• Organization policy: constraints/gcp.restrictNonCmekServices
• Binding at: folders/3
• Policy type: Deny
• Policy values: sqladmin.googleapis.com, storage.googleapis.com

To ensure only keys from Cloud KMS projects under folders/2 are used:

• Organization policy: constraints/gcp.restrictCmekCryptoKeyProjects
• Binding at: folders/3
• Policy type: Allow
• Policy value: under:folders/2

Require CMEK for an organization

To require CMEK everywhere in the organization (in supported services), configure the constraints/gcp.restrictNonCmekServices constraint with the following setting:

• Organization policy: constraints/gcp.restrictNonCmekServices
• Binding at: organizations/1
• Policy type: Deny
• Policy values: (all supported services)

Limitations

If you use Google Cloud console to create a resource, you may notice that you can't use any encryption options other than CMEK when constraints/gcp.restrictNonCmekServices is configured for a project and service. In Preview, the CMEK organization policy restriction is only visible when the customer account has been granted the orgpolicy.policy.get IAM permission on the project.

What's next?

See Introduction to the Organization Policy Service to learn more about the benefits and common use cases for organization policies.

For more examples on creating an organization policy with particular constraints, see Using constraints.