Understanding IAM custom roles

Identity and Access Management (IAM) provides predefined roles that give granular access to specific Google Cloud resources and prevent unwanted access to other resources.

IAM also provides the ability to create customized IAM roles. You can create a custom IAM role with one or more permissions and then grant that custom role to users. IAM provides a UI and API for creating and managing custom roles.

This topic does not provide a comprehensive list of all the IAM permissions you can include in your custom roles. To check whether a specific permission is supported in custom roles, see Support level for permissions in custom roles.

Before you begin

Basic concepts

In IAM, you don't directly grant users permissions. Instead, you grant them roles, which bundle one or more permissions. There are several kinds of roles in IAM: basic roles, predefined roles, and custom roles.

Basic roles include three roles that existed prior to the introduction of IAM: Owner, Editor, and Viewer.

Predefined roles are created and maintained by Google. Their permissions are automatically updated as necessary, such as when new features or services are added to Google Cloud.

Custom roles are user-defined, and allow you to bundle one or more supported permissions to meet your specific needs. Custom roles are not maintained by Google; when new permissions, features, or services are added to Google Cloud, your custom roles will not be updated automatically.

When you create a custom role, you must choose an organization or project to create it in. You can then grant the custom role on the organization or project, as well as any resources within that organization or project.

You create a custom role by combining one or more of the available IAM permissions. Permissions allow users to perform specific actions on Google Cloud resources. In the IAM world, permissions are represented in the form:

service.resource.verb

For example, the compute.instances.list permission allows a user to list the Compute Engine instances they own, and compute.instances.stop allows a user to stop a VM.

Permissions usually, but not always, correspond 1:1 with REST methods. That is, each Google Cloud service has an associated permission for each REST method that it has. To call a method, the caller needs that permission. For example, the caller of topic.publish() needs the pubsub.topics.publish permission.

You can only grant a custom role within the project or organization in which you created it. You cannot grant custom roles on other projects or organizations, or on resources within other projects or organizations.

Required permissions and roles

To create a custom role, a caller must have the iam.roles.create permission.

Users who are not owners, including organization administrators, must be assigned either the Organization Role Administrator role (roles/iam.organizationRoleAdmin) or the IAM Role Administrator role (roles/iam.roleAdmin). The IAM Security Reviewer role (roles/iam.securityReviewer) enables the ability to view custom roles but not administer them. To learn how to grant these roles, see Granting, changing, and revoking access.

The custom roles user interface is in the Google Cloud Console under IAM Roles. It is only available to users who have permissions to create or manage custom roles. By default, only project owners can create new roles. Project owners can control access to this feature by granting IAM Role Administrator role to others on the same project; for organizations, only Organization Administrators can grant the Organization Role Administrator role.

The administrative roles are described in more detail below.

Organization Role Administrator role

If you have an organization associated with your Google Cloud account, the Organization Role Administrator role enables you to administer all custom roles in your organization. This role can only be granted at the organization level. Only Organization Administrators can grant the Organization Role Administrator role.

The following table lists the permissions in the Organization Role Administrator role:

Role Permissions
roles/iam.organizationRoleAdmin iam.roles.create
iam.roles.delete
iam.roles.undelete
iam.roles.get
iam.roles.list
iam.roles.update
resourcemanager.projects.get
resourcemanager.projects.getIamPolicy
resourcemanager.projects.list
resourcemanager.organizations.get
resourcemanager.organizations.getIamPolicy

Role Administrator role

The Role Administrator role enables you to administer all custom roles for a project. Use this role if you do not have an organization. This role can only be granted at the project level by project or organization owners.

The following table lists the permissions in the Role Administrator role:

Role Permissions
roles/iam.roleAdmin iam.roles.create
iam.roles.delete
iam.roles.undelete
iam.roles.get
iam.roles.list
iam.roles.update
resourcemanager.projects.get
resourcemanager.projects.getIamPolicy

Custom roles lifecycle

There are a few concepts that apply when deciding how to model, create, and manage your custom roles.

Creation

Before you decide to create a custom role, check whether the service has a predefined role—or a combination of multiple predefined roles—that meets your needs. For a complete list of predefined roles, as well as the permissions that are included in each predefined role, see the predefined roles reference.

If there is no predefined role—or combination of predefined roles—that meets your needs, you can create a custom role that includes only the permissions you need to grant. For details, see Creating and managing custom roles.

Unsupported or unavailable permissions

Some permissions might not be visible to you or usable in a custom role. For example, a permission might not be available for use in custom roles if the service is in beta, or if you have not enabled the API for the service.

To check whether you can use a specific permission in custom roles, see Support level for permissions in custom roles. To check which permissions you can use with a specific resource, see Viewing the available permissions for a resource.

Permission dependencies

Some permissions are effective only when granted in pairs. For example, to update an IAM policy, you must use the read-modify-write pattern. As a result, to update a policy, you almost always need the getIamPolicy permission for that service and resource type, in addition to the setIamPolicy permission.

To make sure your custom roles are effective, you can create custom roles based on predefined roles with similar permissions. The predefined roles can help you see which permissions are typically used in combination.

To learn how to create a custom role based on a predefined role, see Creating and managing custom roles.

Naming the role

Roles have both an ID and a title. The role ID is a unique identifier for the role. The role title appears in the list of roles in the Cloud Console.

Role IDs must be unique within the project or organization in which you created the role. This ensures that the role's full ID, which includes its project or organization, is unique. Role IDs can be up to 64 characters long and can contain uppercase and lowercase alphanumeric characters, underscores, and periods.

You cannot change role IDs, so choose your role IDs carefully. You can delete a custom role, but you can't create a new custom role with the same full ID until after the 37-day deletion process has completed. For more information about the deletion process, see Deleting a custom role.

The title for a custom role does not have to be unique. Therefore, the Cloud Console could display more than one custom role with the same title. To avoid confusion, use unique and descriptive titles for your custom roles. Also, consider indicating in the role title if the role is an organization-level role or a project-level role.

Role titles can be up to 100 bytes long and can contain uppercase and lowercase alphanumeric characters and symbols. You can change role titles at any time.

Role description

Consider updating the role description after editing a custom role, and include both the date it was modified and a summary of the intended purpose for the role. Descriptions can be up to 256 characters long and can contain uppercase and lowercase alphanumeric characters and symbols.

Testing and deploying

Custom roles include a launch stage, which is stored in the stage property for the role. The launch stage is informational; it helps you keep track of whether each role is ready for widespread use.

Each custom role can have one of the following launch stages:

Launch stages
ALPHA The role is still being developed or tested, or it includes permissions for Google Cloud services or features that are not yet public. It is not ready for widespread use.
BETA The role has been tested on a limited basis, or it includes permissions for Google Cloud services or features that are not generally available.
GA The role has been widely tested, and all of its permissions are for Google Cloud services or features that are generally available.

When you create a custom role, set its launch stage to ALPHA. Ask a few members of your organization to test the role. After you confirm that the custom role works correctly, change the launch stage to BETA or GA.

Maintenance

Job functions and product functionality are constantly evolving. Keeping custom roles up-to-date and following the principle of least privilege requires maintenance effort.

For example, when a released service gets new Beta features, those API methods become publicly available and the permissions are automatically added to the corresponding basic and predefined roles. Your custom roles for that service do not inherit those new permissions, so users assigned to those custom roles may report that they cannot access the new Beta features. At that point, you could choose to add them, or perhaps create a separate custom role to only grant certain users access to those Beta features.

While Google may update an existing predefined role by adding (or removing) permissions, we do not modify custom roles based on the predefined roles. Custom roles are flat lists of permissions; a custom role has no link to the predefined roles it may have been based on.

If your custom role is based on any predefined roles, we recommend listing those roles in the custom role's description field. Doing this makes it easier for you to check whether you should update your custom role based on changes to a predefined role. The Cloud Console automatically puts that information in the description when it creates a new custom role. To learn how to update a custom role's description, see Editing an existing custom role.

Refer to the permissions change log to determine what roles and permissions have changed recently.

Disabling custom roles

If you no longer want people in your organization to use the role, change its role.stage property to DEPRECATED, and optionally set the deprecation_message to let users know what alternative roles should be used or where to get more information. You should also make sure that you don't have any policies in your organization that might still be referencing the deprecated role.

When you're sure that the role can be disabled, call roles:UpdateRole() to disable this role.

Known limitations

  • Some predefined roles contain permissions that are not permitted in custom roles. To check whether you can use a specific permission in a custom role, see Support level for permissions in custom roles.
  • The resourcemanager.projects.list permission is only supported for organization-level custom roles—it is not permitted in project-level custom roles. When you copy a predefined role that includes the resourcemanager.projects.list permission into a new project-level custom role, one of the following messages will be displayed:
    • Cloud Console: The following warning message is displayed: "Not applicable for project-level custom roles". The resourcemanager.projects.list permission will be automatically unselected from the list of included permissions, and you can proceed with creating the role.
    • Cloud SDK gcloud command-line tool: The following error message is returned: INVALID_ARGUMENT: Permission resourcemanager.projects.list is not valid. The custom role will not be created until you first remove the resourcemanager.projects.list permission from the role definition and try the operation again.
    • Google Cloud APIs: The following error message is returned: Permission resourcemanager.projects.list is not valid, along with an HTTP 400 error code and a status of INVALID_ARGUMENT. The custom role will not be created until you first remove the resourcemanager.projects.list permission from the role definition and try the operation again.

What's next

Learn how to create custom roles.