Azure App Service client certificate disabled

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Metadata

Id: a81573f9-3691-4d83-88a0-7d4af63e17a3

Cloud Provider: Azure

Platform: Terraform

Severity: Medium

Category: Insecure Configurations

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Description

Enabling client certificates for Azure App Service ensures that only authenticated clients can access the application by requiring a client SSL certificate in all HTTPS requests. If the client_cert_enabled attribute is not set to true, unauthorized users could potentially connect to the service, increasing the risk of data leaks or abuse. To secure the App Service, always configure the resource as follows:

resource "azurerm_app_service" "example" {
  // ... other configuration ...
  client_cert_enabled = true
}

Compliant Code Examples

resource "azurerm_app_service" "negative" {
  name                = "example-app-service"
  location            = azurerm_resource_group.example.location
  resource_group_name = azurerm_resource_group.example.name
  app_service_plan_id = azurerm_app_service_plan.example.id

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

  app_settings = {
    SOME_KEY = "some-value"
  }

  client_cert_enabled = true

  connection_string {
    name  = "Database"
    type  = "SQLServer"
    value = "Server=some-server.mydomain.com;Integrated Security=SSPI"
  }
}

Non-Compliant Code Examples

resource "azurerm_app_service" "positive2" {
  name                = "example-app-service"
  location            = azurerm_resource_group.example.location
  resource_group_name = azurerm_resource_group.example.name
  app_service_plan_id = azurerm_app_service_plan.example.id

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

  app_settings = {
    SOME_KEY = "some-value"
  }

  client_cert_enabled = false

  connection_string {
    name  = "Database"
    type  = "SQLServer"
    value = "Server=some-server.mydomain.com;Integrated Security=SSPI"
  }
}

resource "azurerm_app_service" "positive1" {
  name                = "example-app-service"
  location            = azurerm_resource_group.example.location
  resource_group_name = azurerm_resource_group.example.name
  app_service_plan_id = azurerm_app_service_plan.example.id

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

  app_settings = {
    SOME_KEY = "some-value"
  }

  connection_string {
    name  = "Database"
    type  = "SQLServer"
    value = "Server=some-server.mydomain.com;Integrated Security=SSPI"
  }
}