Managing access to Compute Engine resources

This page describes how you can exercise the principle of least privilege by granting access to specific Compute Engine resources instead of granting access to a parent resource such as a project, folder, or organization.

You grant access to a resource by setting an Identity and Access Management (IAM) policy on the resource. The policy binds one or more members, such as a user or a service account, to one or more roles. Each role contains a list of permissions that let the member interact with the resource.

If you grant access to a parent resource (for example, to a project), you implicitly grant access to all its child resources (for example, to all VMs in that project). To limit access to resources, set IAM policies on lower-level resources when possible, instead of at the project level or above.

For general information about how to grant, change, and revoke access to resources unrelated to Compute Engine, for example, to grant access to a Google Cloud project, see the IAM documentation for Granting, changing, and revoking access to resources.

Before you begin

  • Review the IAM overview.
  • Read the Compute Engine access control overview.
  • Familiarize yourself with IAM roles for Compute Engine .
  • If you haven't already, then set up authentication. Authentication is the process by which your identity is verified for access to Google Cloud services and APIs. To run code or samples from a local development environment, you can authenticate to Compute Engine by selecting one of the following options:

    Select the tab for how you plan to use the samples on this page:

    Console

    When you use the Google Cloud console to access Google Cloud services and APIs, you don't need to set up authentication.

    gcloud

    1. Install the Google Cloud CLI, then initialize it by running the following command: 

      gcloud init
    2. Set a default region and zone.

    REST

    To use the REST API samples on this page in a local development environment, you use the credentials you provide to the gcloud CLI.

      Install the Google Cloud CLI, then initialize it by running the following command: 

      gcloud init

    For more information, see Authenticate for using REST in the Google Cloud authentication documentation.

Required roles

To get the permissions that you need to manage access to Compute Engine resources, ask your administrator to grant you the Compute Admin (roles/compute.admin) IAM role on the resource. For more information about granting roles, see Manage access to projects, folders, and organizations.

This predefined role contains the permissions required to manage access to Compute Engine resources. To see the exact permissions that are required, expand the Required permissions section:

Required permissions

The following permissions are required to manage access to Compute Engine resources:

  • To grant or revoke access to resources:
    • compute.projects.get on the project
    • compute.RESOURCE_TYPE.get on the resource
    • compute.RESOURCE_TYPE.getIamPolicy on the resource
    • compute.RESOURCE_TYPE.setIamPolicy on the resource
  • To test caller permissions: compute.RESOURCE_TYPE.getIamPolicy on the resource

    Replace RESOURCE_TYPE with the resource that you want to manage access to. For example instances, instanceTemplates, or images.

You might also be able to get these permissions with custom roles or other predefined roles.

Supported resources

To view a list of Compute Engine resources that support resource-level access control, see Resource types that accept IAM policies and filter for Compute Engine.

For other Compute Engine resources that don't support resource-level access control, you must manage access to those resources at the project, folder, or organization levels. For information about organizations, folders, or projects, see Resource hierarchy.

Granting access to Compute Engine resources

A principal, such as a user or service account, can access Compute Engine resources. An identity is a property of a principal. A principal's identity is typically represented by an email address associated with the account.

Before you grant an IAM role to a principal for a resource, check which roles are available to grant on a particular resource. For more information, see Viewing the grantable roles on resources.

To grant permission to access specific Compute Engine resources, set an IAM policy on the resource.

Console

  1. In the Google Cloud console, go to the respective resource page for which you want to add permissions.
  2. Select the checkboxes next to the resources you want to update.
  3. Complete the following steps based on the resource page.
    • For VM instances, click Permissions.
    • For all other resources, complete the following:
      1. Check if the info panel is visible. If it is not visible, click Show info panel.
      2. Select the Permissions tab.
  4. Click Add principal.
  5. Add the identity for the principal and select the required role.
  6. To save your changes, click Save.

gcloud

To grant a role to a principal on a resource, use that resource's add-iam-policy-binding sub-command with the --member and --role flags.

gcloud compute RESOURCE_TYPE add-iam-policy-binding RESOURCE_NAME \
    --member='PRINCIPAL' \
    --role='ROLE'

Replace the following:

  • RESOURCE_TYPE: the type of resource. Valid values include:
    • disks
    • images
    • instances
    • instance-templates
    • machine-images
    • reservations
    • sole-tenancy node-groups
    • sole-tenancy node-templates
    • snapshots
  • RESOURCE_NAME: the name of the resource. For example, my_instance.
  • PRINCIPAL: a valid identity for the principal that you want to grant the role. Must be of the form user|group|serviceAccount:EMAIL_ADDRESS or domain:DOMAIN_ADDRESS. For example:
  • ROLE: the role to assign this principal.

If you are granting access to a resource that is in preview, use a gcloud beta compute command instead.

REST

To modify an IAM policy through the API, do the following:

  1. Read the existing policy with the resource's respective getIamPolicy method. For example, the following HTTP request reads the IAM policy of a VM:

    POST https://compute.googleapis.com/compute/v1/projects/PROJECT_ID/zones/ZONE/instances/VM_NAME:getIamPolicy

    Replace the following:

    • PROJECT_ID: the project ID of the project this VM belongs to.
    • ZONE: the zone of the VM. For regional or global resources, replace zones/ZONE with regions/REGION or global.
    • VM_NAME: the name of the VM instance.

    Compute Engine returns the current policy in the response.

  2. Edit the policy with a text editor to add or remove principals and their associated roles. For example, to grant the compute.admin role to [email protected], add the following new binding to policy:

    {
  "members": [
    "user:[email protected]"
  ],
  "role":"roles/compute.admin"
}

  3. Write the updated policy with setIamPolicy():

    POST https://compute.googleapis.com/compute/v1/projects/PROJECT_ID/zones/ZONE/instances/VM_NAME:setIamPolicy

    Replace the following:

    • PROJECT_ID: the project ID of the project this VM belongs to.
    • ZONE: the zone of the VM. For regional or global resources, replace zones/ZONE with regions/REGION or global.
    • VM_NAME: the name of the VM instance.

    In the body of the request, provide the updated IAM policy from the previous step.

Revoking access to resources

As a best practice, after principals no longer need access to your Compute Engine resources, revoke their access.

Console

  1. In the Google Cloud console, go to the respective resource page for which you want to add permissions.
  2. Select the checkboxes next to the resources you want to update.
  3. Complete the following steps based on the resource page.
    • For VM instances, click Permissions.
    • For all other resources, complete the following:
      1. Check if the info panel is visible. If it is not visible, click Show info panel.
      2. Select the Permissions tab.
  4. Click the role card from which you want to remove principals. This expands the card and shows users with that role for that resource.
  5. To remove a principal from that role, click Delete.

gcloud

To remove a role from a principal for a resource, use the resource's remove-iam-policy-binding sub-command with the --member and --role flags.

gcloud compute RESOURCE_TYPE remove-iam-policy-binding RESOURCE_NAME \
    --member='MEMBER' \
    --role='ROLE'

Replace the following:

  • RESOURCE_TYPE: type of resource. Valid values include:
    • disks
    • images
    • instances
    • instance-templates
    • machine-images
    • reservations
    • sole-tenancy node-groups
    • sole-tenancy node-templates
    • snapshots
  • RESOURCE_NAME: name of the resource. For example, my_instance.
  • PRINCIPAL: a valid identity for the principal. Must be of the form user|group|serviceAccount:EMAIL_ADDRESS or domain:DOMAIN_ADDRESS. For example:
  • ROLE: role from which you want to remove the principal.

If you are revoking access to a resource that is in preview, use a gcloud beta compute command instead.

REST

To modify an IAM policy directly through the API, do the following:

  1. Read the existing policy with the resource's respective getIamPolicy method. For example, the following HTTP request reads the IAM policy of a VM:

    POST https://compute.googleapis.com/compute/v1/projects/PROJECT_ID/zones/ZONE/instances/VM_NAME:getIamPolicy

    Replace the following:

    • PROJECT_ID: the project ID of the project this VM belongs to.
    • ZONE: the zone of the VM. For regional or global resources, replace zones/ZONE with regions/REGION or global.
    • VM_NAME: the name of the VM instance.

    Compute Engine returns the current policy in the response.

  2. Edit the policy with a text editor to remove members from the associated roles. For example, remove [email protected] from the compute.admin role:

    {
  "members": [
    "user:[email protected]"
  ],
  "role":"roles/compute.admin"
}

  3. Write the updated policy with setIamPolicy():

    POST https://compute.googleapis.com/compute/v1/projects/PROJECT_ID/zones/ZONE/instances/VM_NAME:setIamPolicy

    Replace the following:

    • PROJECT_ID: the project ID of the project this VM belongs to.
    • ZONE: the zone of the VM. For regional or global resources, replace zones/ZONE with regions/REGION or global.
    • VM_NAME: the name of the VM instance.

    In the body of the request, provide the updated IAM policy from the previous step.

Testing whether a caller has permissions

If you don't know what permissions an identity has, use the testIamPermissions API method to check which permissions are available to an identity.

The method takes a resource URL and a set of permissions as input parameters, and returns the set of permissions that the caller is allowed. You can use this method on any of the supported resources.

Typically, testIamPermissions is intended for integration with your proprietary software, such as a customized graphical user interface. You typically don't call testIamPermissions if you're using Google Cloud directly to manage permissions.

For example, if you are building a GUI on top of the Compute Engine API and your GUI has a "start" button that starts an instance, you could call compute.instances.testIamPermissions() to determine whether the button should be enabled or disabled.

To test whether a caller has specific permissions on a resource:

  1. Send a request to the resource and include in the request body a list of permissions to check for.

    For example, on an instance, you might check for compute.instances.start, compute.instances.stop, and compute.instances.delete.

    POST https://compute.googleapis.com/compute/v1/projects/PROJECT_ID/zones/ZONE/instances/VM_NAME/testIamPermissions
    {
      "permissions": [
        "compute.instances.start",
        "compute.instances.stop",
        "compute.instances.delete"
       ]
    }

  2. The request returns the permissions that are enabled for the caller.

    {
  "permissions": [
    "compute.instances.start",
    "compute.instances.stop"
  ]
}

Modifying resource access for multiple members

If you want to modify access to Compute Engine resources for multiple members simultaneously, review recommendations on how to modify an IAM policy programmatically.

What's next