You can use HCP Terraform’s native OpenID Connect integration with Vault to use Vault-backed dynamic credentials with the AWS provider in your HCP Terraform runs. Configuring the integration requires the following steps:

1. Configure Vault Dynamic Provider Credentials: Set up a trust configuration between Vault and HCP Terraform, create Vault roles and policies for your HCP Terraform workspaces, and add environment variables to those workspaces.
2. Configure the Vault AWS Secrets Engine: Set up the AWS secrets engine in your Vault instance.
3. Configure HCP Terraform: Add additional environment variables to the HCP Terraform workspaces where you want to use Vault-Backed Dynamic Credentials.
4. Configure Terraform Providers: Configure your Terraform providers to work with Vault-backed dynamic credentials.

Once you complete this setup, HCP Terraform automatically authenticates with AWS via Vault-generated credentials during the plan and apply phase of each run. The AWS provider's authentication is only valid for the length of the plan or apply phase.

Configure Vault Dynamic Provider Credentials

You must first set up Vault dynamic provider credentials before you can use Vault-backed dynamic credentials. This includes setting up the JWT auth backend in Vault, configuring trust between HCP Terraform and Vault, and populating the required environment variables in your HCP Terraform workspace.

See the setup instructions for Vault dynamic provider credentials.

Configure Vault AWS Secrets Engine

Follow the instructions in the Vault documentation for setting up the AWS secrets engine in your Vault instance. You can also do this configuration through Terraform. Refer to our example Terraform configuration.

Configure HCP Terraform

Next, you need to set certain environment variables in your HCP Terraform workspace to authenticate HCP Terraform with AWS using Vault-backed dynamic credentials. These variables are in addition to those you previously set while configuring Vault dynamic provider credentials. You can add these as workspace variables or as a variable set.

Common Environment Variables

The below variables apply to all AWS auth types.

Required Common Environment Variables

Optional Common Environment Variables

You may need to set these variables, depending on your use case.

Assumed Role Specific Environment Variables

These environment variables are only valid if the TFC_VAULT_BACKED_AWS_AUTH_TYPE is assumed_role.

Required Assumed Role Specific Environment Variables

Optional Assumed Role Specific Environment Variables

You may need to set these variables, depending on your use case.

Configure Terraform Providers

The final step is to directly configure your AWS and Vault providers.

Configure the AWS Provider

Ensure you pass a value for the region argument in your AWS provider configuration block or set the AWS_REGION variable in your workspace.

Ensure you are not using any of the arguments or methods mentioned in the authentication and configuration section of the provider documentation. Otherwise, these settings may interfere with dynamic provider credentials.

Configure the Vault Provider

If you were previously using the Vault provider to authenticate the AWS provider, remove any existing usage of the AWS secrets engine from your Terraform Code. This includes the vault_aws_access_credentials data source and any instances of vault_generic_secret you previously used to generate AWS credentials.

Specifying Multiple Configurations

You can add additional configurations to handle multiple distinct Vault-backed AWS setups, enabling you to use multiple provider aliases within the same workspace.

For more details, see Specifying Multiple Configurations.

Required Terraform Variable

To use additional configurations, add the following code to your Terraform configuration. This lets HCP Terraform supply variable values that you can then use to map authentication and configuration details to the correct provider blocks.

variable "tfc_vault_backed_aws_dynamic_credentials" {
  description = "Object containing Vault-backed AWS dynamic credentials configuration"
  type = object({
    default = object({
      shared_credentials_file = string
    })
    aliases = map(object({
      shared_credentials_file = string
    }))
  })
}

Example Usage

provider "aws" {
  shared_credentials_files = [var.tfc_vault_backed_aws_dynamic_credentials.default.shared_credentials_file]
}

provider "aws" {
  alias = "ALIAS1"
  shared_credentials_files = [var.tfc_vault_backed_aws_dynamic_credentials.aliases["ALIAS1"].shared_credentials_file]
}