tf-ghes-oidc

Terraform configuration to setup cloud resources for OpenID Connect (OIDC) on GitHub Enterprise Server (GHES).

Configuring cloud resources to utilize Actions on GHES with OIDC can be a lengthy and challenging task due to stringent security demands that necessitate precise configuration. This repository, although not intended for production purposes, includes Terraform configurations necessary for creating resources across the top three enterprise cloud services: Azure, Amazon Web Services (AWS), and Google Cloud Platform (GCP).

This Terraform configuration is designed to be executed by an individual user, rather than by a Service Account, who is logged into their chosen cloud provider through the corresponding CLI on Linux.

Requirements

To make use of this repository, you need to have a project or a similar setup on either Azure, AWS, or Google Cloud, specifically for creating resources.

Additionally, you need access to the GHES instance, both through its user interface and over SSH. Make sure your SSH keys are properly set up in the GHES Management Console to ensure this access.

Usage

To deploy the resources, follow these steps:

1. Install Terraform and the cloud provider CLIs by executing the scripts/install.sh script. If needed, refresh the console profile file (such as ~/.bashrc) to enable the use of the CLI without requiring the full path.
2. Initialize the (chosen) cloud CLI(s) and authenticate with your cloud provider(s).
3. Navigate to the src directory.
4. Run terraform init to initialize Terraform and install necessary dependencies.
5. The default Terraform backend is set to local, meaning Terraform state is stored locally. This can be altered to any supported backend.
6. Change the name of terraform.tfvars.example to terraform.tfvars and modify the variables to suit your setup. The terraform.tfvars file holds the configuration for the Terraform files.
7. Execute terraform plan -out=plan to prepare for resource creation. This plan is saved in the plan file for the next step.
8. Use terraform apply plan to initiate the creation of the resources.
9. The configuration necessary for enabling Actions on GHES with OIDC in the GHES Management Console is provided at the conclusion of the process, as dictated by the outputs specified in src/outputs.tf.
10. Additional instructions specific to each cloud provider are detailed further below.

Note: If you're just experimenting with Actions on GHES with OIDC, use terraform destroy to delete all resources created by Terraform to prevent unwanted expenses.

Useful Information: This repository's configuration is verified through a GitHub Action in .github/terraform.yml, which ensures its accuracy.

Variables

The Terraform setup requires values for the variables listed in src/variables.tf. The file terraform.tfvars.example serves as a guide. By renaming terraform.tfvars.example to terraform.tfvars, you can supply the necessary information as follows:

• GHES_NAME: Name of the GHES instance (e.g. my-ghes-instance)
• GHES_HOSTNAME: URL of the GHES instance without 'https://' (e.g. my-ghes-instance.com)
• AZURE_SUBSCRIPTION_ID: ID of the Azure Subscription to use
• AZURE_REGION: Region for the Azure Storage Account (defaults to West Europe)
• AZURE_STORAGE_ACCOUNT_TIER: Tier for the Azure Storage Account (defaults to Standard)
• AZURE_STORAGE_ACCOUNT_REPLICATION_TYPE: Replication Type for Azure Storage Account (defaults to LRS)
• AWS_REGION: AWS Region for OIDC Resources (defaults to eu-north-1)
• AWS_OIDC_THUMBPRINT: Thumbprint of the GHES Instance to for OIDC setup on AWS
• GCP_PROJECT_ID: ID of the Google Cloud Project to use
• GCP_REGION: Google Cloud Region for OIDC Resources (defaults to EUROPE-WEST4)

Cloud Providers

Azure

Prior to starting resource creation in Azure, follow these preliminary steps:

1. Ensure the availability of an Azure subscription for your use.
2. Execute az login --use-device-code to authenticate with Azure.
3. If the specific Azure subscription you wish to use is not already active, set it using az account set --subscription="SUBSCRIPTION_ID".
4. Modify the AZURE_SUBSCRIPTION_ID variable in the terraform.tfvars file to match the ID of your chosen Azure subscription for resource deployment.

The required resources for Azure are detailed in the src/azure.tf file. The configuration essential for configuring Actions on GHES with OIDC in the Management Console is produced as outputs: azure_tenant_id, azure_client_id, azure_storage_account_name, and azure_blob_endpoint_suffix.

AWS

To set up the resources on AWS, you need to follow these steps:

1. In AWS, create a set of Access Keys for your account. You can find this in the Security Credentials section (see the documentation).
2. Run the aws configure command and enter the Access Keys you just created. This step links the AWS CLI with your AWS account and creates the ~/.aws/config and ~/.aws/credentials files required by the Terraform AWS provider.
3. Create a new Thumbprint for your GHES instance as outlined in the documentation. This Thumbprint is necessary for the OIDC setup.

This repository also provides the scripts/thumbprint.sh script which generates the Thumbprint. Use it as follows:

# ./script/thumbprint.sh <GHES_HOSTNAME>
$ ./script/thumbprint.sh my-ghes-instance.example.com
$ GHES Thumbprint: AB1234567890ABCDEF1234567890ABCDEF123456 # Thumbprint

4. Update the AWS_REGION and AWS_OIDC_THUMBPRINT variables in the terraform.tfvars file. Set them to your chosen AWS region for deploying resources and the Thumbprint of the GHES instance for the OIDC setup.

The required resources for AWS are detailed in the src/aws.tf file. The configuration essential for configuring Actions on GHES with OIDC in the Management Console is produced as outputs: aws_s3_bucket, aws_role and aws_region.

Google Cloud

Before initiating resource creation in a Google Cloud project, you should follow these preparatory steps:

1. Make sure that the project is linked to a Billing Account.
2. Execute gcloud init to start the Google Cloud CLI and choose the project where you plan to deploy the resources.
3. Run gcloud auth application-default login for authenticating the CLI with Google Cloud.
4. Modify the GCP_PROJECT_ID variable in the terraform.tfvars file to match the ID of your chosen Google Cloud project for resource deployment.

The required resources for Google Cloud are detailed in the src/gcp.tf file. The configuration essential for configuring Actions on GHES with OIDC in the Management Console is produced as outputs: gcp_service_url, gcp_bucket_name, gcp_workload_identity_provider_id, and gcp_service_account.

Improvements

In the future, we could make things better by splitting the settings for different cloud services like Azure, AWS, and Google Cloud into their own separate parts. This would make it easier and more flexible to work with each one on its own. It would help users handle their settings for each cloud service by themselves. This way, if you're just working with one cloud service, things would be smoother.