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Google IAM Terraform Module

This is a collection of submodules that make it easier to non-destructively manage multiple IAM roles for resources on Google Cloud Platform:

Compatibility

This module is meant for use with Terraform 1.3+ and tested using Terraform 1.3+. If you find incompatibilities using Terraform >=1.3, please open an issue.

Upgrading

The following guides are available to assist with upgrades:

Usage

Full examples are in the examples folder, but basic usage is as follows for managing roles on two projects:

module "projects_iam_bindings" {
  source  = "terraform-google-modules/iam/google//modules/projects_iam"
  version = "~> 8.0"

  projects = ["project-123456", "project-9876543"]

  bindings = {
    "roles/storage.admin" = [
      "group:[email protected]",
      "user:[email protected]",
    ]

    "roles/compute.networkAdmin" = [
      "group:[email protected]",
      "user:[email protected]",
    ]

    "roles/compute.imageUser" = [
      "user:[email protected]",
    ]
  }
}

The module also offers an authoritative mode which will remove all roles not assigned through Terraform. This is an example of using the authoritative mode to manage access to a storage bucket:

module "storage_buckets_iam_bindings" {
  source  = "terraform-google-modules/iam/google//modules/storage_buckets_iam"
  version = "~> 8.0"

  storage_buckets = ["my-storage-bucket"]

  mode = "authoritative"

  bindings = {
    "roles/storage.legacyBucketReader" = [
      "user:[email protected]",
      "group:[email protected]",
    ]

    "roles/storage.legacyBucketWriter" = [
      "user:[email protected]",
      "group:[email protected]",
    ]
  }
}

Additive and Authoritative Modes

The mode variable controls a submodule's behavior, by default it's set to "additive", possible options are:

  • additive: add members to role, old members are not deleted from this role.
  • authoritative: set the role's members (including removing any not listed), unlisted roles are not affected.

In authoritative mode, a submodule takes full control over the IAM bindings listed in the module. This means that any members added to roles outside the module will be removed the next time Terraform runs. However, roles not listed in the module will be unaffected.

In additive mode, a submodule leaves existing bindings unaffected. Instead, any members listed in the module will be added to the existing set of IAM bindings. However, members listed in the module are fully controlled by the module. This means that if you add a binding via the module and later remove it, the module will correctly handle removing the role binding.

Caveats

Referencing values/attributes from other resources

Each submodule performs operations over some variables before making any changes on the IAM bindings in GCP. Because of the limitations of for_each (more info), which is widely used in the submodules, there are certain limitations to what kind of dynamic values you can provide to a submodule:

  1. Dynamic entities (for example projects) are only allowed for 1 entity.
  2. If you pass 2 or more entities (for example projects), the configuration MUST be static, meaning that it can't use any of the other resources' fields to get the entity name from (this includes getting the randomly generated hashes through the random_id resource).
  3. The role names themselves can never be dynamic.
  4. Members may only be dynamic in authoritative mode.

IAM Bindings

You can choose the following resource types to apply the IAM bindings:

  • Projects (projects variable)
  • Organizations(organizations variable)
  • Folders (folders variable)
  • Service Accounts (service_accounts variable)
  • Subnetworks (subnets variable)
  • Storage buckets (storage_buckets variable)
  • Pubsub topics (pubsub_topics variable)
  • Pubsub subscriptions (pubsub_subscriptions variable)
  • Kms Key Rings (kms_key_rings variable)
  • Kms Crypto Keys (kms_crypto_keys variable)
  • Secret Manager Secrets (secrets variable)
  • DNS Zones (managed_zones variable)
  • Secure Source Manager (entity_ids and location variable)

Set the specified variable on the module call to choose the resources to affect. Remember to set the mode variable and give enough permissions to manage the selected resource as well. Note that the bindings variable accepts an empty map {} passed in as an argument in the case that resources don't have IAM bindings to apply.

Requirements

Terraform plugins

Permissions

In order to execute a submodule you must have a Service Account with an appropriate role to manage IAM for the applicable resource. The appropriate role differs depending on which resource you are targeting, as follows:

  • Organization:
    • Organization Administrator: Access to administer all resources belonging to the organization and does not include privileges for billing or organization role administration.
    • Custom: Add resourcemanager.organizations.getIamPolicy and resourcemanager.organizations.setIamPolicy permissions.
  • Project:
    • Owner: Full access and all permissions for all resources of the project.
    • Projects IAM Admin: allows users to administer IAM policies on projects.
    • Custom: Add resourcemanager.projects.getIamPolicy and resourcemanager.projects.setIamPolicy permissions.
  • Folder:
    • The Folder Admin: All available folder permissions.
    • Folder IAM Admin: Allows users to administer IAM policies on folders.
    • Custom: Add resourcemanager.folders.getIamPolicy and resourcemanager.folders.setIamPolicy permissions (must be added in the organization).
  • Service Account:
    • Service Account Admin: Create and manage service accounts.
    • Custom: Add resourcemanager.organizations.getIamPolicy and resourcemanager.organizations.setIamPolicy permissions.
  • Subnetwork:
    • Project compute admin: Full control of Compute Engine resources.
    • Project compute network admin: Full control of Compute Engine networking resources.
    • Project custom: Add compute.subnetworks.getIamPolicy and compute.subnetworks.setIamPolicy permissions.
  • Storage bucket:
    • Storage Admin: Full control of GCS resources.
    • Storage Legacy Bucket Owner: Read and write access to existing buckets with object listing/creation/deletion.
    • Custom: Add storage.buckets.getIamPolicy and storage.buckets.setIamPolicy permissions.
  • Pubsub topic:
    • Pub/Sub Admin: Create and manage service accounts.
    • Custom: Add pubsub.topics.getIamPolicy and pubsub.topics.setIamPolicy permissions.
  • Pubsub subscription:
    • Pub/Sub Admin role: Create and manage service accounts.
    • Custom role: Add pubsub.subscriptions.getIamPolicy and pubsub.subscriptions.setIamPolicy permissions.
  • Kms Key Ring:
    • Owner: Full access to all resources.
    • Cloud KMS Admin: Enables management of crypto resources.
    • Custom: Add cloudkms.keyRings.getIamPolicy and cloudkms.keyRings.getIamPolicy permissions.
  • Kms Crypto Key:
    • Owner: Full access to all resources.
    • Cloud KMS Admin: Enables management of cryptoresources.
    • Custom: Add cloudkms.cryptoKeys.getIamPolicy and cloudkms.cryptoKeys.setIamPolicy permissions.
  • Secret Manager:
    • Secret Manager Admin: Full access to administer Secret Manager.
    • Custom: Add secretmanager.secrets.getIamPolicy and secretmanager.secrets.setIamPolicy permissions.
  • DNS Zone:
    • DNS Administrator : Full access to administer DNS Zone.
    • Custom: Add dns.managedZones.setIamPolicy, dns.managedZones.list and dns.managedZones.getIamPolicy permissions.

Install

Terraform

Be sure you have the correct Terraform version >= 1.3

Terraform plugins

Be sure you have the compiled plugins on $HOME/.terraform.d/plugins/

See each plugin page for more information about how to compile and use them.