Use custom organization policies

Google Cloud Organization Policy 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 organization policies.

Benefits

You can use custom organization policies that reference IAM attributes to control how your allow policies can be modified. Specifically, you can control the following:

• Who can be granted roles
• Who can have their roles revoked
• Which roles can be granted
• Which roles can be revoked

For example, you can prevent roles that contain the word admin from being granted to principals whose email addresses end in @gmail.com.

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.

Pricing

The Organization Policy Service, including predefined and custom organization policies, is offered at no charge.

Limitations

Custom organization policies in dry-run mode that reference IAM attributes have some limitations. Namely, audit logs for violations that involve the setiamPolicy method might be missing the following fields:

• resourceName
• serviceName
• methodName

Before you begin

• Ensure that you know your organization ID.

• If you want to test out custom organization policies that reference IAM resources, create a new project. Testing these organization policies in an existing project could disrupt security workflows.

  1. In the Google Cloud console, go to the project selector page.

     Go to project selector

  2. Select or create a Google Cloud project.

Required roles

To get the permissions that you need to manage organization policies, ask your administrator to grant you the following IAM roles:

• Organization policy administrator (roles/orgpolicy.policyAdmin) on the organization
• Modify your project's IAM policy: Project IAM Admin (roles/resourcemanager.projectIamAdmin) on the project

For more information about granting roles, see Manage access to projects, folders, and organizations.

These predefined roles contain the permissions required to manage organization policies. To see the exact permissions that are required, expand the Required permissions section:

You might also be able to get these permissions with 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 YAML file for a custom constraint:

name: organizations/ORG_ID/customConstraints/CONSTRAINT_NAME
resourceTypes: iam.googleapis.com/AllowPolicy
methodTypes:
  METHOD_TYPE
condition: "CONDITION"
actionType: ACTION
displayName: DISPLAY_NAME
description: DESCRIPTION

Replace the following:

• ORG_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.denyProjectIAMAdmin. The maximum length of this field is 70 characters, not counting the prefix, for example, organizations/123456789/customConstraints/custom.

• METHOD_TYPE: the type of action that you want to the constraint to apply for. If you want the constraint to apply when someone tries to grant a role to a principal, use the following values:

  - CREATE
  - UPDATE
  

  If you want the constraint to apply when someone tries to revoke a principal's role, use the following value:

  - REMOVE_GRANT
  

• 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 attributes for more information about the attributes available to write conditions against. For example, resource.bindings.exists(binding, RoleNameMatches(binding.role, ['roles/resourcemanager.projectIamAdmin'])).

• ACTION: the action to take if the condition is met. This can be either ALLOW or DENY.

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

• DESCRIPTION: optional. 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

gcloud org-policies set-custom-constraint CONSTRAINT_PATH

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

Enforce a custom organization policy

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

    gcloud org-policies set-policy POLICY_PATH
    

Test the custom organization policy

Optionally, you can test the organization policy by setting the policy and then trying to take an action that the policy should prevent.

This section describes how to test the following organization policy constraint:

name: organizations/ORG_ID/customConstraints/custom.denyProjectIAMAdmin
resourceTypes: iam.googleapis.com/AllowPolicy
methodTypes:
  - CREATE
  - UPDATE
condition:
  "resource.bindings.exists(
    binding,
    RoleNameMatches(binding.role, ['roles/resourcemanager.projectIamAdmin']) &&
    binding.members.exists(member,
      MemberSubjectMatches(member, ['user:EMAIL_ADDRESS'])
    )
  )"
actionType: DENY
displayName: Do not allow EMAIL_ADDRESS to be granted the Project IAM Admin role.

If you want to test this custom constraint, do the following:

• Copy the constraint into a YAML file and replace the following values:

  • ORG_ID: the numeric ID of your Google Cloud organization.
  • MEMBER_EMAIL_ADDRESS: the email address of the principal that you want to use to test the custom constraint. While the constraint is active, this principal won't be able to be granted the Project IAM Admin role (roles/resourcemanager.projectIamAdmin) on the project that you enforce the constraint for.

• Set up the custom constraint and enforce it for the project that you created to test the custom organization policy constraint.

• Try to grant the Project IAM Admin role (roles/resourcemanager.projectIamAdmin) to the principal whose email address you included in the custom constraint. Before running the command, replace the following values:

  • PROJECT_ID: The ID of the Google Cloud project where you enforced the constraint
  • EMAIL_ADDRESS: The email address of the principal that you specified when you created the organization policy constraint.

gcloud projects add-iam-policy-binding PROJECT_ID \
    --member=user:EMAIL_ADDRESS --role=roles/resourcemanager.projectIamAdmin

The output is the following:

Operation denied by custom org policies: ["customConstraints/custom.denyProjectIAMAdmin": "EMAIL_ADDRESS can't be granted the Project IAM Admin role."]

Identity and Access Management supported attributes

IAM supports the resources.bindings attribute. This attribute is returned for all methods that modify a resource's allow policy. All of these methods end with setIamPolicy.

The resource.bindings attribute has the following structure, where BINDINGS is an array of role bindings that were modified during a change to an allow policy:

{
  "bindings": {
    BINDINGS
  }
}

Each binding in resource.bindings has the following structure, where ROLE is the name of the role in the role binding and MEMBERS is a list of identifiers for the principals that were added to or removed from the role binding:

{
  "role": "ROLE"
  "members": {
    MEMBERS
  }
}

To see the formats that principal identifiers can have, see Principal identifiers.

You can only evaluate the resource.bindings attribute and its fields using the supported functions. Other operators and functions—like ==, !=, in, contains, startsWith, and endsWith—are not supported.

Supported functions

You can use the following CEL functions to evaluate the role and members fields of binding resources. When using these functions, you can also use the logical operators && (and) and || (or) to write multipart conditions.

Example custom organization policies for common use cases

The following table provides the syntax of some custom organization policies that you might find useful.

The following examples use the CEL macros all and exists. For more information about these macros, see Macros.

name: organizations/ORG_ID/customConstraints/custom.denyRole
resourceTypes: iam.googleapis.com/AllowPolicy
methodTypes:
  - CREATE
  - UPDATE
condition:
"resource.bindings.exists(
    binding,
    RoleNameMatches(binding.role, ['ROLE'])
  )"
actionType: DENY
displayName: Do not allow the ROLE role to be granted

name: organizations/ORG_ID/customConstraints/custom.specificRolesOnly
resourceTypes: iam.googleapis.com/AllowPolicy
methodTypes:
  - CREATE
  - UPDATE
condition:
  "resource.bindings.all(
    binding,
    RoleNameMatches(binding.role, ['ROLE_1', 'ROLE_2'])
  )"
actionType: ALLOW
displayName: Only allow the ROLE_1 role and ROLE_2 role to be granted

name: organizations/ORG_ID/customConstraints/custom.dontgrantStorageRoles
resourceTypes: iam.googleapis.com/AllowPolicy
methodTypes:
  - CREATE
  - UPDATE
condition:
  "resource.bindings.exists(
    binding,
    RoleNameStartsWith(binding.role, ['roles/storage.'])
  )"
actionType: DENY
displayName: Prevent roles that start with "roles/storage." from being granted

name: organizations/ORG_ID/customConstraints/custom.dontRevokeAdminRoles
resourceTypes: iam.googleapis.com/AllowPolicy
methodTypes:
  - REMOVE_GRANT
condition:
  "resource.bindings.exists(
    binding,
    RoleNameContains(binding.role, ['admin'])
  )"
actionType: DENY
displayName: Prevent roles with "admin" in their names from being revoked

name: organizations/ORG_ID/customConstraints/custom.allowSpecificPrincipals
resourceTypes: iam.googleapis.com/AllowPolicy
methodTypes:
  - CREATE
  - UPDATE
condition:
  "resource.bindings.all(
    binding,
    binding.members.all(member,
      MemberSubjectMatches(member, ['user:USER','serviceAccount:SERVICE_ACCOUNT'])
    )
  )"
actionType: ALLOW
displayName: Only allow roles to be granted to USER and SERVICE_ACCOUNT

name: organizations/ORG_ID/customConstraints/custom.denyRemovalOfSpecificPrincipals
resourceTypes: iam.googleapis.com/AllowPolicy
methodTypes:
  - REMOVE_GRANT
condition:
  "resource.bindings.exists(
    binding,
    binding.members.exists(member,
      MemberSubjectMatches(member, ['user:USER_1','user:USER_2'])
    )
  )"
actionType: DENY
displayName: Do not allow roles to be revoked from USER_1 or USER_2

name: organizations/ORG_ID/customConstraints/custom.dontGrantToGmail
resourceTypes: iam.googleapis.com/AllowPolicy
methodTypes:
  - CREATE
  - UPDATE
condition:
  "resource.bindings.exists(
    binding,
    binding.members.exists(member,
      MemberSubjectEndsWith(member, ['@gmail.com'])
    )
  )"
actionType: DENY
displayName: Do not allow members whose email addresses end with "@gmail.com" to be granted roles

name: organizations/ORG_ID/customConstraints/custom.allowSpecificRolesAndPrincipals
resourceTypes: iam.googleapis.com/AllowPolicy
methodTypes:
  - CREATE
  - UPDATE
condition:
  "resource.bindings.all(
    binding,
    RoleNameMatches(binding.role, ['ROLE_1', 'ROLE_2'])  &&
    binding.members.all(member,
      MemberSubjectMatches(member, ['serviceAccount:SERVICE_ACCOUNT', 'group:GROUP'])
    )
  )"
actionType: ALLOW
displayName: Only allow ROLE_1 and ROLE_2 to be granted to SERVICE_ACCOUNT and GROUP

name: organizations/ORG_ID/customConstraints/custom.denyStorageRolesForPrincipalAllUsers
resourceTypes: iam.googleapis.com/AllowPolicy
methodTypes:
  - CREATE
  - UPDATE
condition:
  "resource.bindings.exists(
    binding,
    RoleNameStartsWith(binding.role, ['roles/storage.']) &&
    binding.members.exists(member,
      MemberSubjectMatches(member, ['allUsers', 'allAuthenticatedUsers'])
    )
  )"
actionType: DENY
displayName: Do not allow storage roles to be granted to allUsers or allAuthenticatedUsers

What's next

• See Introduction to the Organization Policy Service to learn more about organization policies.
• Learn more about how to create and manage organization policies.
• See the full list of predefined Organization policy constraints.