You can use HCP Terraform’s native OpenID Connect integration with Vault to use Vault-backed dynamic credentials with the GCP 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 GCP Secrets Engine: Set up the GCP 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 GCP via Vault-generated credentials during the plan and apply phase of each run. The GCP 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 GCP Secrets Engine

Follow the instructions in the Vault documentation for setting up the GCP 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 GCP 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. When you configure dynamic provider credentials with multiple provider configurations of the same type, use either a default variable or a tagged alias variable name for each provider configuration. Refer to Specifying Multiple Configurations for more details.

Common Environment Variables

The below variables apply to all GCP auth types.

Required Common Environment Variables

Optional Common Environment Variables

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

Roleset Specific Environment Variables

These environment variables are only valid if the TFC_VAULT_BACKED_GCP_AUTH_TYPE is roleset/access_token or roleset/service_account_key.

Required Roleset Specific Environment Variables

Optional Roleset Specific Environment Variables

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

Static Account Specific Environment Variables

These environment variables are only valid if the TFC_VAULT_BACKED_GCP_AUTH_TYPE is static_account/access_token or static_account/service_account_key.

Required Static Account Specific Environment Variables

Optional Static Account 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 GCP and Vault providers.

Configure the GCP Provider

Ensure you pass values for the project and region arguments into the provider configuration block.

Ensure you are not setting values or environment variables for GOOGLE_CREDENTIALS or GOOGLE_APPLICATION_CREDENTIALS. Otherwise, these values may interfere with dynamic provider credentials.

Configure the Vault Provider

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

Specifying Multiple Configurations

You can add additional variables to handle multiple distinct Vault-backed GCP setups, enabling you to use multiple provider aliases within the same workspace. You can configure each set of credentials independently, or use default values by configuring the variables prefixed with TFC_DEFAULT_.

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_gcp_dynamic_credentials" {
  description = "Object containing Vault-backed GCP dynamic credentials configuration"
  type = object({
    default = object({
      credentials = string
      access_token = string
    })
    aliases = map(object({
      credentials = string
      access_token = string
    }))
  })
}

Example Usage

Access Token

provider "google" {
  access_token = var.tfc_vault_backed_gcp_dynamic_credentials.default.access_token
}

provider "google" {
  alias = "ALIAS1"
  access_token = var.tfc_vault_backed_gcp_dynamic_credentials.aliases["ALIAS1"].access_token
}

Credentials

provider "google" {
  credentials = var.tfc_vault_backed_gcp_dynamic_credentials.default.credentials
}

provider "google" {
  alias = "ALIAS1"
  credentials = var.tfc_vault_backed_gcp_dynamic_credentials.aliases["ALIAS1"].credentials
}