terraform-google-bastion-host

This module will generate a bastion host vm compatible with OS Login and IAP Tunneling that can be used to access internal VMs.

This module will:

• Create a dedicated service account for the bastion host
• Create a GCE instance to be the bastion host
• Create a firewall rule to allow TCP:22 SSH access from the IAP to the bastion
• Necessary IAM bindings to allow IAP and OS Logins from specified members

Usage

Basic usage of this module is as follows:

module "iap_bastion" {
  source = "terraform-google-modules/bastion-host/google"

  project = var.project
  zone    = var.zone
  network = google_compute_network.net.self_link
  subnet  = google_compute_subnetwork.net.self_link
  members = [
    "group:devs@example.com",
    "user:me@example.com",
  ]
}

Functional example is included in the examples directory.

Requirements

These sections describe requirements for using this module.

Software

The following dependencies must be available:

• Terraform >= v0.12
• Terraform Provider for GCP

APIs

A project with the following APIs enabled must be used to host the resources of this module:

• Google Cloud Storage JSON API: storage-api.googleapis.com
• Compute Engine API: compute.googleapis.com
• Cloud Identity-Aware Proxy API: iap.googleapis.com
• OS Login API: oslogin.googleapis.com

The Project Factory module can be used to provision a project with the necessary APIs enabled.

Permissions

This module only sets up permissions for the bastion service account, not the users who need access. To allow access, grant one of the following instance access roles.

• roles/compute.osLogin Does not grant administrator permissions
• roles/compute.osAdminLogin Grants administrator permissions.

If the user does not share the same domain as the org the bastion is in, you will also need to grant that user roles/compute.osLoginExternalUser. This is to prevent external SSH access from being granted at the project level. See the OS Login documentation for more information.

Inputs

Name	Description	Type	Default	Required
access_config	Access configs for network, nat_ip and DNS	list(object({ network_tier = string nat_ip = string public_ptr_domain_name = string }))	[ { "nat_ip": "", "network_tier": "PREMIUM", "public_ptr_domain_name": "" } ]	no
additional_networks	Additional network interface details for the instance template, if any.	list(object({ network = string subnetwork = string subnetwork_project = string network_ip = string access_config = list(object({ nat_ip = string network_tier = string })) }))	[]	no
additional_ports	A list of additional ports/ranges to open access to on the instances from IAP.	list(string)	[]	no
create_firewall_rule	If we need to create the firewall rule or not.	bool	true	no
create_instance_from_template	Whether to create and instance from the template or not. If false, no instance is created, but the instance template is created and usable by a MIG	bool	true	no
disk_encryption_key	The key used to encrypt the bastion host disk. If not set, the disk will not be encrypted.	string	null	no
disk_labels	Key-value map of labels to assign to the bastion host disk	map(any)	{}	no
disk_size_gb	Boot disk size in GB	number	100	no
disk_type	Boot disk type, can be either pd-ssd, local-ssd, or pd-standard	string	"pd-standard"	no
external_ip	Set to true if an ephemeral or static external IP/DNS is required, must also set access_config if true	bool	false	no
fw_name_allow_ssh_from_iap	Firewall rule name for allowing SSH from IAP	string	"allow-ssh-from-iap-to-tunnel"	no
host_project	The network host project ID	string	""	no
image	Source image for the Bastion. If image is not specified, image_family will be used (which is the default).	string	""	no
image_family	Source image family for the Bastion.	string	"debian-11"	no
image_project	Project where the source image for the Bastion comes from	string	"debian-cloud"	no
labels	Key-value map of labels to assign to the bastion host	map(any)	{}	no
machine_type	Instance type for the Bastion host	string	"n1-standard-1"	no
members	List of IAM resources to allow access to the bastion host	list(string)	[]	no
metadata	Key-value map of additional metadata to assign to the instances	map(string)	{}	no
name	Name of the Bastion instance	string	"bastion-vm"	no
name_prefix	Name prefix for instance template	string	"bastion-instance-template"	no
network	Self link for the network on which the Bastion should live	string	n/a	yes
preemptible	Allow the instance to be preempted	bool	false	no
project	The project ID to deploy to	string	n/a	yes
random_role_id	Enables role random id generation.	bool	true	no
region	The region where the bastion instance template will live	string	null	no
scopes	List of scopes to attach to the bastion host	list(string)	[ "cloud-platform" ]	no
service_account_email	If set, the service account and its permissions will not be created. The service account being passed in should have at least the roles listed in the service_account_roles variable so that logging and OS Login work as expected.	string	""	no
service_account_name	Account ID for the service account	string	"bastion"	no
service_account_roles	List of IAM roles to assign to the service account.	list(string)	[ "roles/logging.logWriter", "roles/monitoring.metricWriter", "roles/monitoring.viewer", "roles/compute.osLogin" ]	no
service_account_roles_supplemental	An additional list of roles to assign to the bastion if desired	list(string)	[]	no
shielded_vm	Enable shielded VM on the bastion host (recommended)	bool	true	no
startup_script	Render a startup script with a template.	string	""	no
subnet	Self link for the subnet on which the Bastion should live. Can be private when using IAP	string	n/a	yes
tags	Network tags, provided as a list	list(string)	[]	no
zone	The primary zone where the bastion host will live	string	"us-central1-a"	no

Outputs

Name	Description
hostname	Host name of the bastion
instance_template	Self link of the bastion instance template for use with a MIG
ip_address	Internal IP address of the bastion host
self_link	Self link of the bastion host
service_account	The email for the service account created for the bastion host

Contributing

Refer to the contribution guidelines for information on contributing to this module.