Create custom constraints for Access Context Manager

This page shows you how to use Organization Policy Service custom constraints to restrict specific operations on the following Google Cloud resources:

  • accesscontextmanager.googleapis.com/AccessPolicy
  • accesscontextmanager.googleapis.com/AccessLevel
  • accesscontextmanager.googleapis.com/AuthorizedOrgsDesc
  • accesscontextmanager.googleapis.com/ServicePerimeter

To learn more about Organization Policy, see Custom organization policies.

About organization policies and constraints

The Google Cloud Organization Policy Service gives you centralized, programmatic control over your organization's resources. As the organization policy administrator, you can define an organization policy, which is a set of restrictions called constraints that apply to Google Cloud resources and descendants of those resources in the Google Cloud resource hierarchy. You can enforce organization policies at the organization, folder, or project level.

Organization Policy provides predefined constraints for various Google Cloud services. However, if you want more granular, customizable control over the specific fields that are restricted in your organization policies, you can also create custom constraints and use those custom constraints in an organization policy.

Policy inheritance

By default, organization policies are inherited by the descendants of the resources on which you enforce the policy. For example, if you enforce a policy on a folder, Google Cloud enforces the policy on all projects in the folder. To learn more about this behavior and how to change it, refer to Hierarchy evaluation rules.

Before you begin

  1. Sign in to your Google Cloud account. If you're new to Google Cloud, create an account to evaluate how our products perform in real-world scenarios. New customers also get $300 in free credits to run, test, and deploy workloads.

  2. In the Google Cloud console, on the project selector page, select or create a Google Cloud project.

    Go to project selector

  3. Make sure that billing is enabled for your Google Cloud project.

  4. Install the Google Cloud CLI.

  5. If you're using an external identity provider (IdP), you must first sign in to the gcloud CLI with your federated identity.

  6. To initialize the gcloud CLI, run the following command: 

    gcloud init

  7. In the Google Cloud console, on the project selector page, select or create a Google Cloud project.

    Go to project selector

  8. Make sure that billing is enabled for your Google Cloud project.

  9. Install the Google Cloud CLI.

  10. If you're using an external identity provider (IdP), you must first sign in to the gcloud CLI with your federated identity.

  11. To initialize the gcloud CLI, run the following command: 

    gcloud init
  12. Ensure that you know your organization ID.

Required roles

To get the permissions that you need to manage custom organization policies, ask your administrator to grant you the Organization Policy Administrator (roles/orgpolicy.policyAdmin) IAM role on the organization resource. For more information about granting roles, see Manage access to projects, folders, and organizations.

You might also be able to get the required permissions through custom roles or other predefined roles.

Create a custom constraint

A custom constraint is defined in a YAML file by the resources, methods, conditions, and actions that are supported by the service on which you are enforcing the organization policy. Conditions for your custom constraints are defined using Common Expression Language (CEL). For more information about how to build conditions in custom constraints using CEL, see the CEL section of Creating and managing custom constraints.

To create a custom constraint, create a YAML file using the following format:

name: organizations/ORGANIZATION_ID/customConstraints/CONSTRAINT_NAME
resourceTypes:
- RESOURCE_NAME
methodTypes:
- CREATE
- UPDATE
condition: "CONDITION"
actionType: ACTION
displayName: DISPLAY_NAME
description: DESCRIPTION

Replace the following:

  • ORGANIZATION_ID: your organization ID, such as 123456789.

  • CONSTRAINT_NAME: the name you want for your new custom constraint. A custom constraint must start with custom., and can only include uppercase letters, lowercase letters, or numbers. For example, custom.disableCustomAccessLevels. The maximum length of this field is 70 characters.

  • RESOURCE_NAME: the fully qualified name of the Google Cloud resource containing the object and field you want to restrict. For example, accesscontextmanager.googleapis.com/AccessLevel.

  • CONDITION: a CEL condition that is written against a representation of a supported service resource. This field has a maximum length of 1000 characters. See Supported resources for more information about the resources available to write conditions against. For example, "resource.basic.conditions.exists(c, has(c.devicePolicy))".

  • ACTION: the action to take if the condition is met. Possible values are ALLOW and DENY.

  • DISPLAY_NAME: a human-friendly name for the constraint. This field has a maximum length of 200 characters.

  • DESCRIPTION: a human-friendly description of the constraint to display as an error message when the policy is violated. This field has a maximum length of 2000 characters.

For more information about how to create a custom constraint, see Defining custom constraints.

Set up a custom constraint

After you have created the YAML file for a new custom constraint, you must set it up to make it available for organization policies in your organization. To set up a custom constraint, use the gcloud org-policies set-custom-constraint command: 
gcloud org-policies set-custom-constraint CONSTRAINT_PATH
 Replace CONSTRAINT_PATH with the full path to your custom constraint file. For example, /home/user/customconstraint.yaml. Once completed, your custom constraints are available as organization policies in your list of Google Cloud organization policies. To verify that the custom constraint exists, use the gcloud org-policies list-custom-constraints command: 
gcloud org-policies list-custom-constraints --organization=ORGANIZATION_ID
 Replace ORGANIZATION_ID with the ID of your organization resource. For more information, see Viewing organization policies.

Enforce a custom organization policy

You can enforce a boolean constraint by creating an organization policy that references it, and then applying that organization policy to a Google Cloud resource.

Console

  1. In the Google Cloud console, go to the Organization policies page.

    Go to Organization policies

  2. From the project picker, select the project for which you want to set the organization policy.
  3. From the list on the Organization policies page, select your constraint to view the Policy details page for that constraint.
  4. To configure the organization policy for this resource, click Manage policy.
  5. On the Edit policy page, select Override parent's policy.
  6. Click Add a rule.
  7. In the Enforcement section, select whether enforcement of this organization policy is on or off.
  8. Optional: To make the organization policy conditional on a tag, click Add condition. Note that if you add a conditional rule to an organization policy, you must add at least one unconditional rule or the policy cannot be saved. For more information, see Setting an organization policy with tags.
  9. If this is a custom constraint, you can click Test changes to simulate the effect of this organization policy. For more information, see Test organization policy changes with Policy Simulator.
  10. To finish and apply the organization policy, click Set policy. The policy requires up to 15 minutes to take effect.

gcloud

To create an organization policy that enforces a boolean constraint, create a policy YAML file that references the constraint: 

      name: projects/PROJECT_ID/policies/CONSTRAINT_NAME
      spec:
        rules:
        - enforce: true

Replace the following:

  • PROJECT_ID: the project on which you want to enforce your constraint.
  • CONSTRAINT_NAME: the name you defined for your custom constraint. For example, custom.disableCustomAccessLevels.

To enforce the organization policy containing the constraint, run the following command: 

    gcloud org-policies set-policy POLICY_PATH

Replace POLICY_PATH with the full path to your organization policy YAML file. The policy requires up to 15 minutes to take effect.

Test the custom organization policy

The following example creates a custom constraint and policy that denies all basic access levels in a specific organization that uses the devicePolicy attribute.

Before you begin, you should know the following:

  • Your organization ID
  • A project ID

Create a custom constraint

  1. Save the following file as constraint-disable_custom_access_level.yaml:

    name: organizations/ORGANIZATION_ID/customConstraints/custom.disableCustomAccessLevels
resourceTypes:
- accesscontextmanager.googleapis.com/AccessLevel
methodTypes:
- CREATE
- UPDATE
condition: "resource.basic.conditions.exists(c, has(c.devicePolicy))"
actionType: DENY
displayName: Deny basic access levels using `devicePolicy`
description: Basic access levels must not use the `devicePolicy` attribute.

    Replace ORGANIZATION_ID with your organization ID.

    This defines a constraint that only allows the creation of basic access levels and denies the creation of custom access levels.

  2. Apply the constraint:

    gcloud org-policies set-custom-constraint ~/constraint-disable_custom_access_level.yaml

  3. Verify that the constraint exists:

    gcloud org-policies list-custom-constraints --organization=ORGANIZATION_ID

    The output is similar to the following:

    CUSTOM_CONSTRAINT                  ACTION_TYPE   METHOD_TYPES   RESOURCE_TYPES                                    DISPLAY_NAME
custom.disableCustomAccessLevels   DENY          CREATE         accesscontextmanager.googleapis.com/AccessLevel   Deny basic access levels using `devicePolicy`
...

Create the policy

  1. Save the following file as policy-disable_custom_access_level.yaml:

    name: organizations/ORGANIZATION_ID/policies/custom.disableCustomAccessLevels
spec:
  rules:
  - enforce: true

    Replace ORGANIZATION_ID with your organization ID.

  2. Apply the policy:

    gcloud org-policies set-policy ~/policy-disable_custom_access_level.yaml

  3. Verify that the policy exists:

    gcloud org-policies list --organization=ORGANIZATION_ID

    The output is similar to the following:

    CONSTRAINT                               LIST_POLICY   BOOLEAN_POLICY   ETAG
custom.disableCustomAccessLevels         -             SET              COCsm5QGENiXi2E=

After you apply the policy, wait for about two minutes for Google Cloud to start enforcing the policy.

Test the policy

  1. Save the following access level specification file as example_access_level.yaml:

    - devicePolicy:
requireScreenlock: true

  2. Create an access level:

    gcloud access-context-manager levels create ACCESS_LEVEL_NAME --policy=ACCESS_POLICY_ID --title=ACCESS_LEVEL_TITLE --basic-level-spec=example_access_level.yaml

    Replace the following:

    • ACCESS_LEVEL_NAME: A unique name for the access level.

    • ACCESS_POLICY_ID: The ID of your organization's access policy.

    • ACCESS_LEVEL_TITLE: A short title for the access level.

    For more information about creating a basic access level, see Create a basic access level.

    The output is similar to the following:

    ERROR: (gcloud.access-context-manager.levels.create) [USER] does not have permission to access accessPolicies instance [ACCESS_POLICY_ID] (or it may not exist): The caller does not have permission. This command is authenticated as USER which is the active account specified by the [core/account] property
  '@type': type.googleapis.com/google.rpc.DebugInfo
  detail: '[ORIGINAL ERROR] generic::permission_denied: com.google.apps.framework.request.ForbiddenException:
    The user is not authorized!'

    Example custom organization policies for common use cases

    The following table provides the syntax of some custom constraints for common use cases:

    Description Constraint syntax
    Disable scoped policies 
        name: organizations/ORGANIZATION_ID/customConstraints/custom.disableScopedPolicies
    resourceTypes:
    - accesscontextmanager.googleapis.com/AccessPolicy
    methodTypes:
    - CREATE
    - UPDATE
    condition: "size(resource.scopes) == 0"
    actionType: DENY
    displayName: Disable scoped policies
    description: Disables the creation of scoped policies.
    Disable custom access levels 
        name: organizations/ORGANIZATION_ID/customConstraints/custom.denyBasicAccessLevels
    resourceTypes:
    - accesscontextmanager.googleapis.com/AccessLevel
    methodTypes:
    - CREATE
    - UPDATE
    condition: "has(resource.custom)"
    actionType: ALLOW
    displayName: Disable custom access levels
    description: Disables the creation of custom access levels. Allows only basic access levels.
    Disable region_code in custom access levels 
        name: organizations/ORGANIZATION_ID/customConstraints/custom.denyRegionCode
    resourceTypes:
    - accesscontextmanager.googleapis.com/AccessLevel
    methodTypes:
    - CREATE
    - UPDATE
    condition: "resource.custom.expr.expression.contains('region_code')"
    actionType: DENY
    displayName: Disable region_code in custom access levels
    description: Disables the use of region_code attribute in custom access levels.
    Enforce verbose description for access levels 
        name: organizations/ORGANIZATION_ID/customConstraints/custom.enforseVerboseDescriptioninAccessLevels
    resourceTypes:
    - accesscontextmanager.googleapis.com/AccessLevel
    methodTypes:
    - CREATE
    - UPDATE
    condition: "size(resource.description) < 50"
    actionType: DENY
    displayName: Enforce access level descriptions to have at least 50 characters
    description: Denies access levels with a short description. The access level description must be at least 50 characters long.
    Disable perimeter bridges 
        name: organizations/ORGANIZATION_ID/customConstraints/custom.denyBridgePerimeters
    resourceTypes:
    - accesscontextmanager.googleapis.com/ServicePerimeter
    methodTypes:
    - CREATE
    - UPDATE
    condition: "resource.perimeterType == 'PERIMETER_TYPE_BRIDGE'"
    actionType: DENY
    displayName: Disable perimeter bridges
    description: Disables the use of perimeter bridges. Instead, use ingress and egress rules.

    Access Context Manager supported resources

    The following table lists the Access Context Manager resources that you can reference in custom constraints.

    Resource Field
    accesscontextmanager.googleapis.com/AccessLevel resource.basic.combiningFunction
    resource.basic.conditions.devicePolicy.allowedDeviceManagementLevels
    resource.basic.conditions.devicePolicy.allowedEncryptionStatuses
    resource.basic.conditions.devicePolicy.osConstraints.minimumVersion
    resource.basic.conditions.devicePolicy.osConstraints.osType
    resource.basic.conditions.devicePolicy.osConstraints.requireVerifiedChromeOs
    resource.basic.conditions.devicePolicy.requireAdminApproval
    resource.basic.conditions.devicePolicy.requireCorpOwned
    resource.basic.conditions.devicePolicy.requireScreenlock
    resource.basic.conditions.ipSubnetworks
    resource.basic.conditions.members
    resource.basic.conditions.negate
    resource.basic.conditions.regions
    resource.basic.conditions.requiredAccessLevels
    resource.custom.expr.description
    resource.custom.expr.expression
    resource.custom.expr.location
    resource.custom.expr.title
    resource.description
    resource.title
    accesscontextmanager.googleapis.com/AccessPolicy resource.parent
    resource.scopes
    resource.title
    accesscontextmanager.googleapis.com/AuthorizedOrgsDesc resource.assetType
    resource.authorizationDirection
    resource.authorizationType
    resource.orgs
    accesscontextmanager.googleapis.com/ServicePerimeter resource.description
    resource.perimeterType
    resource.spec.accessLevels
    resource.spec.egressPolicies.egressFrom.identities
    resource.spec.egressPolicies.egressFrom.identityType
    resource.spec.egressPolicies.egressFrom.sourceRestriction
    resource.spec.egressPolicies.egressTo.externalResources
    resource.spec.egressPolicies.egressTo.operations.methodSelectors.method
    resource.spec.egressPolicies.egressTo.operations.methodSelectors.permission
    resource.spec.egressPolicies.egressTo.operations.serviceName
    resource.spec.egressPolicies.egressTo.resources
    resource.spec.ingressPolicies.ingressFrom.identities
    resource.spec.ingressPolicies.ingressFrom.identityType
    resource.spec.ingressPolicies.ingressFrom.sources.accessLevel
    resource.spec.ingressPolicies.ingressFrom.sources.resource
    resource.spec.ingressPolicies.ingressTo.operations.methodSelectors.method
    resource.spec.ingressPolicies.ingressTo.operations.methodSelectors.permission
    resource.spec.ingressPolicies.ingressTo.operations.serviceName
    resource.spec.ingressPolicies.ingressTo.resources
    resource.spec.resources
    resource.spec.restrictedServices
    resource.spec.vpcAccessibleServices.allowedServices
    resource.spec.vpcAccessibleServices.enableRestriction
    resource.status.accessLevels
    resource.status.egressPolicies.egressFrom.identities
    resource.status.egressPolicies.egressFrom.identityType
    resource.status.egressPolicies.egressFrom.sourceRestriction
    resource.status.egressPolicies.egressTo.externalResources
    resource.status.egressPolicies.egressTo.operations.methodSelectors.method
    resource.status.egressPolicies.egressTo.operations.methodSelectors.permission
    resource.status.egressPolicies.egressTo.operations.serviceName
    resource.status.egressPolicies.egressTo.resources
    resource.status.ingressPolicies.ingressFrom.identities
    resource.status.ingressPolicies.ingressFrom.identityType
    resource.status.ingressPolicies.ingressFrom.sources.accessLevel
    resource.status.ingressPolicies.ingressFrom.sources.resource
    resource.status.ingressPolicies.ingressTo.operations.methodSelectors.method
    resource.status.ingressPolicies.ingressTo.operations.methodSelectors.permission
    resource.status.ingressPolicies.ingressTo.operations.serviceName
    resource.status.ingressPolicies.ingressTo.resources
    resource.status.resources
    resource.status.restrictedServices
    resource.status.vpcAccessibleServices.allowedServices
    resource.status.vpcAccessibleServices.enableRestriction
    resource.title
    resource.useExplicitDryRunSpec

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