Well Documented Nerd

So by using TerraForm, you gain a lot of benefits, including being able to manage all parts of your infrastructure using HCL languages to make it rather easy to manage.

A key part of that is not only being able to manage the resources you create, but also access to them, by creating and assigning storage principals. In older versions of TerraForm this was possible using the azurerm_azuread_application and other elements. I had previously done this in the Kubernetes template I have on github.

Now, with TerraForm v2.0, there have been some pretty big changes, including removing all of the Azure AD elements and moving them to their own provider, and the question becomes “How does that change my template?”

Below is an example, it shows the creation of a service principal, with a random password, and creating an access policy for a keyvault.

resource "random_string" "kub-rs-pd-kv" {
  length = 32
  special = true
}

data "azurerm_subscription" "current" {
    subscription_id =  "${var.subscription_id}"
}
resource "azurerm_azuread_application" "kub-ad-app-kv1" {
  name = "${format("%s%s%s-KUB1", upper(var.environment_code), upper(var.deployment_code), upper(var.location_code))}"
  available_to_other_tenants = false
  oauth2_allow_implicit_flow = true
}

resource "azurerm_azuread_service_principal" "kub-ad-sp-kv1" {
  application_id = "${azurerm_azuread_application.kub-ad-app-kv1.application_id}"
}

resource "azurerm_azuread_service_principal_password" "kub-ad-spp-kv" {
  service_principal_id = "${azurerm_azuread_service_principal.kub-ad-sp-kv1.id}"
  value                = "${element(random_string.kub-rs-pd-kv.*.result, count.index)}"
  end_date             = "2020-01-01T01:02:03Z"
}

resource "azurerm_key_vault" "kub-kv" {
  name = "${var.environment_code}${var.deployment_code}${var.location_code}lkub-kv1"
  location = "${var.azure_location}"
  resource_group_name = "${azurerm_resource_group.management.name}"

  sku {
    name = "standard"
  }

  tenant_id = "${var.keyvault_tenantid}"

  access_policy {
    tenant_id = "${var.keyvault_tenantid}"
    object_id = "${azurerm_azuread_service_principal.kub-ad-sp-kv1.id}"

    key_permissions = [
      "get",
    ]

    secret_permissions = [
      "get",
    ]
  }
  access_policy {
    tenant_id = "${var.keyvault_tenantid}"
    object_id = "${azurerm_azuread_service_principal.kub-ad-sp-kv1.id}"

    key_permissions = [
      "create",
    ]

    secret_permissions = [
      "set",
    ]
  }

  depends_on = ["azurerm_role_assignment.kub-ad-sp-ra-kv1"]
}

Now as I mentioned, with the change to the new provider, you will see a new version of this code be implemented. Below is an updated form of code that generates a service principal with a random password.

provider "azuread" {
  version = "=0.7.0"
}

resource "random_string" "cds-rs-pd-kv" {
  length = 32
  special = true
}

resource "azuread_application" "cds-ad-app-kv1" {
  name = format("%s-%s%s-cds1",var.project_name,var.deployment_code,var.environment_code)
  oauth2_allow_implicit_flow = true
}

resource "azuread_service_principal" "cds-ad-sp-kv1" {
  application_id = azuread_application.cds-ad-app-kv1.application_id
}

resource "azuread_service_principal_password" "cds-ad-spp-kv" {
  service_principal_id  = azuread_service_principal.cds-ad-sp-kv1.id
  value                = random_string.cds-rs-pd-kv.result
  end_date             = "2020-01-01T01:02:03Z"
}

Notice how much cleaner the code is, first we aren’t doing the ${} to do string interpolation, and ultimately the resources are much cleaner. So the next question is how do I connect this with my code to assign this service principal to a keyvault access policy.

You can accomplish that with the following code, which is in a different file in the same directory:

resource "azurerm_resource_group" "cds-configuration-rg" {
    name = format("%s-Configuration",var.group_name)
    location = var.location 
}

data "azurerm_client_config" "current" {}

resource "azurerm_key_vault" "cds-kv" {
    name = format("%s-%s%s-kv",var.project_name,var.deployment_code,var.environment_code)
    location = var.location
    resource_group_name = azurerm_resource_group.cds-configuration-rg.name 
    enabled_for_disk_encryption = true
    tenant_id = data.azurerm_client_config.current.tenant_id
    soft_delete_enabled = true
    purge_protection_enabled = false
 
  sku_name = "standard"
 
  access_policy {
    tenant_id = data.azurerm_client_config.current.tenant_id
    object_id = data.azurerm_client_config.current.object_id
 
    key_permissions = [
      "create",
      "get",
    ]
 
    secret_permissions = [
      "set",
      "get",
      "delete",
    ]
  }

  access_policy {
    tenant_id = data.azurerm_client_config.current.tenant_id
    object_id = azuread_service_principal.cds-ad-sp-kv1.id

    key_permissions = [
      "get",
    ]

    secret_permissions = [
      "get",
    ]
  }
}

Notice that I am able to reference the “azuread_service_principal.cds-ad-sp-kv1.id” to access the newly created service principal without issue.