Upload Your Sentinel Policy Set to Terraform Cloud

To enable Sentinel policy enforcement on your Terraform runs, you must upload your policy to your Terraform Cloud organization. In this tutorial, you will create a new Sentinel policy set in your organization, configure a workspace to apply your policy, and trigger the Sentinel policy checks.

»Prerequisites

For this tutorial you will need:

• A Terraform Cloud Team & Governance tier account or a Terraform Enterprise account
• Access to the owners group of your Terraform organization
• A GitHub account
• An AWS account to create example resources

You should also be familiar with how to create and destroy Terraform Cloud workspaces.

»Fork the sample repository

Fork the sample repository, which contains an example Terraform configuration to provision an EC2 instance.

Navigate to the versions.tf file in your fork of the repository in the Github web UI, and click the pencil icon in the top right corner.

In the backend configuration block, replace "<YOUR_TERRAFORM_ORG>" with the name of your Terraform Cloud organization. Commit the change.

»Create a Terraform Cloud workspace

Navigate to your Terraform Cloud organization and create a new VCS-backed workspace connected to your fork of the learn-sentinel-tfc repository.

»Configure workspace variables

Navigate to your learn-sentinel-tfc workspace's "Variables" page.

Define a variable called instance_type and set the value to t2.large.

Define environment variables for your AWS_ACCESS_KEY_ID and AWS_SECRET_ACCESS_KEY. Be sure to set both as sensitive.

When complete, your variable definitions will match the following:

»Fork the Sentinel policy set repository

Now fork the sample repository containing a Sentinel policy and rule enforcement definition.

The restrict-aws-instances-type-and-tag.sentinel file contains a Sentinel policy that defines a main rule that consists of two other rules defining infrastructure requirements:

• mandatory_instance_tags: Ensures that all EC2 instances have a Name tag.
• instance_types_allowed: Ensures that EC2 instances are of type t2.micro, t2.small, or t2.medium.

The sentinel.hcl file defines the level of enforcement for your Sentinel policies. If you have multiple policies in your policy repository, you must list them all here. Terraform Cloud applies the policies in the order they appear in this file.

policy "restrict-aws-instances-type-and-tag" {
  enforcement_level = "hard-mandatory"
}

policy "restrict-aws-instances-type-and-tag" {  enforcement_level = "hard-mandatory"}

Notice the configured enforcement_level for your policy. There are three levels of enforcement associated with policies in Terraform Cloud: advisory, soft mandatory, and hard mandatory. From most permissive to least permissive:

»Connect the policy set

In the Terraform Cloud UI, navigate to "Settings" > "Policy Sets". Then, click on "Connect a new policy set" to create a new policy set.

Select your fork of the learn-sentinel-policy-upload repository as the source. For more information or for other VCS connection settings, visit our documentation on VCS Integrations.

Terraform Cloud applies policy sets either across your organization, or to specific workspaces.

On the "Configure Settings" page:

1. Select "Policies enforced on selected workspaces" under "Scope of Policies"
2. Select your learn-sentinel-tfc workspace and click the purple "Add workspace button"
3. Click "Connect policy set"

»Trigger a Sentinel Check

Navigate to your learn-sentinel-tfc workspace. Select "Start new plan" from the "Actions" menu, and run the default "Plan (most common)" option.

This plan run will fail because your configuration violates the instance_types_allowed rule. Terraform will not allow you to apply the plan.

Navigate to the workspace's "Variables" page and update the value of instance_type to t2.small. Save the variable.

Start another plan run. This time, Sentinel will validate the proposed changes and allow you to apply the plan.

Since this is the end of the tutorial, click "Discard the run".

»Delete the policy set

Navigate back to your policy set under "Settings" > "Policy Sets". Under workspaces, click "Delete policy set". Confirm by clicking "Yes, delete policy set".

»Delete workspace

If you do not plan on exploring other tutorials in this collection, you can delete the workspace you created. Terraform Cloud does not charge per workspace, so you are free to leave it if you would like.

Under your workspace's "Settings" menu, select the "Destruction and Deletion" option and then delete the workspace.

»Next steps

You have now uploaded a Sentinel policy set to Terraform Cloud and triggered policy failures and passes. To learn more about Sentinel, review the following resources:

• Learn how to Generate Mock Policy Data
• Review how to Write a Sentinel Policy
• Review how to Test a Sentinel Policy
• Review Sentinel and Terraform Cloud documentation
• Experiment in the Sentinel Playground
• Review Sentinel Language Specification documentation