azure: pass MSI auth info through to terraform

Configure the managed identity within the provider block as per the
provider docs [1]

[1] https://registry.terraform.io/providers/hashicorp/azurerm/latest/docs/guides/managed_service_identity#configuring-with-the-provider-block

Author: r4f4

data/data/azure/bootstrap/main.tf

@@ -13,6 +13,7 @@ provider "azurerm" {
   client_certificate_path     = var.azure_certificate_path
   tenant_id                   = var.azure_tenant_id
   environment                 = var.azure_environment
+  use_msi                     = var.azure_use_msi
 }
 
 data "azurerm_storage_account" "storage_account" {

data/data/azure/cluster/main.tf

@@ -12,6 +12,7 @@ provider "azurerm" {
   client_certificate_password = var.azure_certificate_password
   client_certificate_path     = var.azure_certificate_path
   tenant_id                   = var.azure_tenant_id
+  use_msi                     = var.azure_use_msi
   environment                 = var.azure_environment
 }
 

data/data/azure/variables-azure.tf

@@ -99,6 +99,7 @@ variable "azure_subscription_id" {
 variable "azure_client_id" {
   type = string
   description = "The app ID that should be used to interact with Azure API"
+  default = ""
 }
 
 variable "azure_client_secret" {
@@ -124,6 +125,12 @@ variable "azure_tenant_id" {
   description = "The tenant ID that should be used to interact with Azure API"
 }
 
+variable "azure_use_msi" {
+  type = bool
+  default = false
+  description = "Specifies if we are to use a managed identity for authentication"
+}
+
 variable "azure_master_availability_zones" {
   type = list(string)
   description = "The availability zones in which to create the masters. The length of this list must match master_count."

data/data/azure/vnet/main.tf

@@ -19,6 +19,7 @@ provider "azurerm" {
   client_certificate_password = var.azure_certificate_password
   client_certificate_path     = var.azure_certificate_path
   tenant_id                   = var.azure_tenant_id
+  use_msi                     = var.azure_use_msi
   environment                 = var.azure_environment
 }
 

pkg/asset/cluster/tfvars.go

@@ -315,13 +315,15 @@ func (t *TerraformVariables) Generate(parents asset.Parents) error {
 		if err != nil {
 			return err
 		}
+
 		auth := azuretfvars.Auth{
 			SubscriptionID:            session.Credentials.SubscriptionID,
 			ClientID:                  session.Credentials.ClientID,
 			ClientSecret:              session.Credentials.ClientSecret,
 			TenantID:                  session.Credentials.TenantID,
 			ClientCertificatePath:     session.Credentials.ClientCertificatePath,
 			ClientCertificatePassword: session.Credentials.ClientCertificatePassword,
+			UseMSI:                    session.AuthType == aztypes.ManagedIdentityAuth,
 		}
 		masters, err := mastersAsset.Machines()
 		if err != nil {

pkg/tfvars/azure/azure.go

@@ -22,6 +22,7 @@ type Auth struct {
 	TenantID                  string `json:"azure_tenant_id,omitempty"`
 	ClientCertificatePath     string `json:"azure_certificate_path,omitempty"`
 	ClientCertificatePassword string `json:"azure_certificate_password,omitempty"`
+	UseMSI                    bool   `json:"azure_use_msi,omitempty"`
 }
 
 type config struct {