Function App not using latest TLS encryption version

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Metadata

Id: 45fc717a-bd86-415c-bdd8-677901be1aa6

Cloud Provider: Azure

Platform: Terraform

Severity: Medium

Category: Encryption

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Description

Azure Function Apps should be configured to use the latest supported TLS version to ensure encrypted communications and protect data in transit. If the min_tls_version attribute is set to an outdated value such as 1.1, as shown below, the application becomes susceptible to known TLS vulnerabilities and exploits:

site_config {
  min_tls_version = 1.1
}

To mitigate these risks and enforce stronger secure connections with clients, set min_tls_version to at least 1.2, as shown here:

site_config {
  min_tls_version = 1.2
}

Compliant Code Examples

resource "azurerm_function_app" "negative3" {
  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
}

resource "azurerm_function_app" "negative2" {
  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

  site_config {
    dotnet_framework_version = "v4.0"
    scm_type                 = "LocalGit"
  }
}

resource "azurerm_function_app" "negative1" {
  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

  site_config {
    dotnet_framework_version = "v4.0"
    scm_type                 = "LocalGit"
    min_tls_version = 1.2
  }
}

Non-Compliant Code Examples

resource "azurerm_function_app" "positive2" {
  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

  site_config {
    dotnet_framework_version = "v4.0"
    scm_type                 = "LocalGit"
    min_tls_version = "1.1"
  }
}

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

  site_config {
    dotnet_framework_version = "v4.0"
    scm_type                 = "LocalGit"
    min_tls_version = 1.1
  }
}