Function App managed identity disabled

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Metadata

Id: c87749b3-ff10-41f5-9df2-c421e8151759

Cloud Provider: azure

Framework: Terraform

Severity: Medium

Category: Insecure Configurations

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Description

Azure Function Apps should have managed identities enabled to allow for secure authentication to Azure services without the need for hard-coded credentials. If the identity block is omitted in a Terraform resource, as in the example below, the Function App will not have a managed identity and may rely on less secure methods, such as embedding credentials in code or configuration:

resource "azurerm_function_app" "insecure" {
  name                       = "test-azure-functions"
  location                   = azurerm_resource_group.example.location
  resource_group_name        = azurerm_resource_group.example.name
  app_service_plan_id        = azurerm_app_service_plan.example.id
  storage_account_name       = azurerm_storage_account.example.name
  storage_account_access_key = azurerm_storage_account.example.primary_access_key
}

Enabling a managed identity using the identity { type = "SystemAssigned" } block in your configuration ensures secure service-to-service communication and reduces the risk of credential leakage:

resource "azurerm_function_app" "secure" {
  name                       = "test-azure-functions"
  location                   = azurerm_resource_group.example.location
  resource_group_name        = azurerm_resource_group.example.name
  app_service_plan_id        = azurerm_app_service_plan.example.id
  storage_account_name       = azurerm_storage_account.example.name
  storage_account_access_key = azurerm_storage_account.example.primary_access_key

  identity {
    type = "SystemAssigned"
  }
}

Leaving this unaddressed may expose sensitive data or allow unauthorized access to connected Azure resources through weaker authentication mechanisms.

Compliant Code Examples

resource "azurerm_function_app" "negative" {
  name                       = "test-azure-functions"
  location                   = azurerm_resource_group.example.location
  resource_group_name        = azurerm_resource_group.example.name
  app_service_plan_id        = azurerm_app_service_plan.example.id
  storage_account_name       = azurerm_storage_account.example.name
  storage_account_access_key = azurerm_storage_account.example.primary_access_key

  identity {
    type = "SystemAssigned"
  }
}

Non-Compliant Code Examples

resource "azurerm_function_app" "positive1" {
  name                       = "test-azure-functions"
  location                   = azurerm_resource_group.example.location
  resource_group_name        = azurerm_resource_group.example.name
  app_service_plan_id        = azurerm_app_service_plan.example.id
  storage_account_name       = azurerm_storage_account.example.name
  storage_account_access_key = azurerm_storage_account.example.primary_access_key
}