Deploy Tunnels with Terraform

Terraform Open external link is an infrastructure as code software tool that allows you to deploy services from different providers using a standardized configuration syntax. When creating a Terraform configuration file, you define the final state of the configuration rather than the step-by-step procedure. This allows you to easily deploy, modify, and manage your Tunnels alongside your other infrastructure.

In this guide, you will use Terraform to deploy:

• A Google Cloud Project (GCP) virtual machine that runs a simple HTTP test server
• A Cloudflare Tunnel that makes the server available over the Internet
• A Cloudflare Access policy that defines who can connect to the server

​​ Prerequisites

To complete the following procedure, you will need:

• A Google Cloud Project Open external link
• A zone on Cloudflare

​​ 1. Install Terraform

Refer to the Terraform installation guide Open external link for your operating system.

​​ 2. Install the gcloud CLI

1. Install the gcloud CLI Open external link so that Terraform can interact with your GCP account.

2. Authenticate with the CLI by running:

   $ gcloud auth application-default login
   

​​ 3. Create a Cloudflare API token

Create an API token so that Terraform can interact with your Cloudflare account. At minimum, your token should include the following permissions:

​​ 4. Create a configuration directory

Terraform functions through a working directory that contains the configuration files. You can store your configuration in multiple files or just one — Terraform will evaluate all of the configuration files in the directory as if they were in a single document.

1. Create a folder for your Terraform configuration:

   $ mkdir gcp-tunnel
   

2. Change into the directory:

   $ cd gcp-tunnel
   

​​ 5. Create Terraform configuration files

​​ Define input variables

The following variables will be passed into your GCP and Cloudflare configuration.

1. In your configuration directory, create a .tf file:

   $ touch variables.tf
   

2. Open the file in a text editor and copy and paste the following:

   variables.tf
   # GCP variables
   variable "gcp_project_id" {
     description = "Google Cloud Platform (GCP) project ID"
     type        = string
   }
   
   variable "zone" {
     description = "Geographical zone for the GCP VM instance"
     type        = string
   }
   
   variable "machine_type" {
     description = "Machine type for the GCP VM instance"
     type        = string
   }
   
   # Cloudflare variables
   variable "cloudflare_zone" {
     description = "Domain used to expose the GCP VM instance to the Internet"
     type        = string
   }
   
   variable "cloudflare_zone_id" {
     description = "Zone ID for your domain"
     type        = string
   }
   
   variable "cloudflare_account_id" {
     description = "Account ID for your Cloudflare account"
     type        = string
     sensitive   = true
   }
   
   variable "cloudflare_email" {
     description = "Email address for your Cloudflare account"
     type        = string
     sensitive   = true
   }
   
   variable "cloudflare_token" {
     description = "Cloudflare API token created at https://dash.cloudflare.com/profile/api-tokens"
     type        = string
     sensitive   = true
   }

​​ Assign values to the variables

1. In your configuration directory, create a .tfvars file:

   $ touch terraform.tfvars
   

   Terraform will automatically use these variables if the file is named terraform.tfvars, otherwise the variable file will need to be manually passed in.

2. Add the following variables to terraform.tfvars. Be sure to modify the example with your own values.

   terraform.tfvars
   cloudflare_zone           = "example.com"
   cloudflare_zone_id        = "023e105f4ecef8ad9ca31a8372d0c353"
   cloudflare_account_id     = "372e67954025e0ba6aaa6d586b9e0b59"
   cloudflare_email          = "user@example.com"
   cloudflare_token          = "y3AalHS_E7Vabk3c3lX950F90_Xl7YtjSlzyFn_X"
   gcp_project_id            = "testvm-123"
   zone                      = "us-central1-a"
   machine_type              = "e2-medium"

​​ Configure Terraform providers

You will need to declare the providers Open external link used to provision the infrastructure.

1. In your configuration directory, create a .tf file:

   $ touch providers.tf
   

2. Add the following providers to providers.tf. The random provider is used to generate a tunnel secret.

   providers.tf
   terraform {
     required_providers {
       cloudflare = {
         source = "cloudflare/cloudflare"
         version = ">= 4.9.0"
       }
       google = {
         source = "hashicorp/google"
       }
       random = {
         source = "hashicorp/random"
       }
     }
     required_version = ">= 0.13"
   }
   
   # Providers
   provider "cloudflare" {
     api_token    = var.cloudflare_token
   }
   provider "google" {
     project    = var.gcp_project_id
   }
   provider "random" {
   }

​​ Configure Cloudflare resources

The following configuration will modify settings in your Cloudflare account.

1. In your configuration directory, create a .tf file:

   $ touch Cloudflare-config.tf
   

2. Add the following resources to Cloudflare-config.tf:

   Cloudflare-config.tf
   # Generates a 64-character secret for the tunnel.
   # Using `random_password` means the result is treated as sensitive and, thus,
   # not displayed in console output. Refer to: https://registry.terraform.io/providers/hashicorp/random/latest/docs/resources/password
   resource "random_password" "tunnel_secret" {
     length = 64
   }
   
   # Creates a new locally-managed tunnel for the GCP VM.
   resource "cloudflare_tunnel" "auto_tunnel" {
     account_id = var.cloudflare_account_id
     name       = "Terraform GCP tunnel"
     secret     = base64sha256(random_password.tunnel_secret.result)
   }
   
   # Creates the CNAME record that routes http_app.${var.cloudflare_zone} to the tunnel.
   resource "cloudflare_record" "http_app" {
     zone_id = var.cloudflare_zone_id
     name    = "http_app"
     value   = "${cloudflare_tunnel.auto_tunnel.cname}"
     type    = "CNAME"
     proxied = true
   }
   
   # Creates the configuration for the tunnel.
   resource "cloudflare_tunnel_config" "auto_tunnel" {
     tunnel_id = cloudflare_tunnel.auto_tunnel.id
     account_id = var.cloudflare_account_id
     config {
      ingress_rule {
        hostname = "${cloudflare_record.http_app.hostname}"
        service  = "http://httpbin:8080"
      }
      ingress_rule {
        service  = "http_status:404"
      }
     }
   }
   
   # Creates an Access application to control who can connect.
   resource "cloudflare_access_application" "http_app" {
     zone_id          = var.cloudflare_zone_id
     name             = "Access application for http_app.${var.cloudflare_zone}"
     domain           = "http_app.${var.cloudflare_zone}"
     session_duration = "1h"
   }
   
   # Creates an Access policy for the application.
   resource "cloudflare_access_policy" "http_policy" {
     application_id = cloudflare_access_application.http_app.id
     zone_id        = var.cloudflare_zone_id
     name           = "Example policy for http_app.${var.cloudflare_zone}"
     precedence     = "1"
     decision       = "allow"
     include {
       email = [var.cloudflare_email]
     }
   }

   To learn more about these resources, refer to the Cloudflare provider documentation Open external link .

​​ Configure GCP resources

The following configuration defines the specifications for the GCP virtual machine and creates a startup script to run upon boot.

1. In your configuration directory, create a .tf file:

   $ touch GCP-config.tf
   

2. Add the following content to GCP-config.tf:

   GCP-config.tf
   # Selects the OS for the GCP VM.
   data "google_compute_image" "image" {
     family  = "ubuntu-minimal-2004-lts"
     project = "ubuntu-os-cloud"
   }
   
   # Sets up a GCP VM instance.
   resource "google_compute_instance" "origin" {
     name         = "test"
     machine_type = var.machine_type
     zone         = var.zone
     tags         = []
     boot_disk {
       initialize_params {
         image = data.google_compute_image.image.self_link
       }
     }
   
     network_interface {
       network = "default"
       access_config {
         // Ephemeral IP
       }
     }
     // Optional config to make the instance ephemeral
     scheduling {
       preemptible       = true
       automatic_restart = false
     }
     // Configures the VM to run a startup script that takes in the Terraform variables.
     metadata_startup_script = templatefile("./install-tunnel.tpl",
       {
         tunnel_token = cloudflare_tunnel.auto_tunnel.tunnel_token
       })
   }

​​ Create a startup script

The following script will install cloudflared, create a permissions and configuration file for the tunnel, and set up the tunnel to run as a service. This example also installs a lightweight HTTP application that you can use to test connectivity.

1. In your configuration directory, create a Terraform template file:

   $ touch install-tunnel.tftpl
   

2. Open the file in a text editor and copy and paste the following bash script:

   install-tunnel.tftpl
   # Script to install Cloudflare Tunnel and Docker resources
   
   # Docker configuration
   cd /tmp
   sudo apt-get install software-properties-common
   # Retrieving the docker repository for this OS
   curl -fsSL https://download.docker.com/linux/ubuntu/gpg | sudo apt-key add -
   sudo add-apt-repository "deb [arch=amd64] https://download.docker.com/linux/ubuntu bionic stable"
   # The OS is updated and docker is installed
   sudo apt update -y && sudo apt upgrade -y
   sudo apt install docker docker-compose -y
   # Add the HTTPBin application and run it on localhost:8080.
   cat > /tmp/docker-compose.yml << "EOF"
   version: '3'
   services:
     httpbin:
       image: kennethreitz/httpbin
       restart: always
       container_name: httpbin
   
     cloudflared:
       image: cloudflare/cloudflared:latest
       restart: always
       container_name: cloudflared
       command: tunnel run --token ${tunnel_token} 
   EOF
   cd /tmp
   sudo docker-compose up -d
   

​​ 6. Deploy Terraform

Once the configuration files are created, they can be deployed.

1. Initialize your configuration directory:

   $ terraform init
   

   This will set up the directory so that your infrastructure can be deployed.

2. Before actually deploying your infrastructure, you can preview everything that will be created:

   $ terraform plan
   

3. Deploy the configuration:

   $ terraform apply
   

It may take several minutes for the GCP instance and tunnel to come online. You can view your new tunnel, Access application, and Access policy in the Access section of Zero Trust Open external link . The new DNS records are available in the Cloudflare dashboard Open external link .

​​ 7. Test the connection

1. In Networks > Tunnels, verify that your tunnel is active.

2. In Access > Applications, verify that your Cloudflare email is allowed by the Access policy.

3. From any device, open a browser and go to http_app.<cloudflare_zone> (for example, http_app.example.com).

   You will see the Access login page if you have not recently logged in.

4. Log in with your Cloudflare email.

   You should see the HTTPBin Open external link homepage.