cis-azure-compute-2-3-11

name	cis-azure-compute-2.3.11
description	Ensure 'App Service authentication' is set to 'Enabled'
category	cis-azure-compute
version	2.0.0
author	cyberstrike-official
tags	["cis","azure","function-apps","app-service-auth","authentication","identity"]
cis_id	2.3.11
cis_benchmark	CIS Microsoft Azure Compute Services Benchmark v2.0.0
tech_stack	["azure"]
cwe_ids	[]
chains_with	[]
prerequisites	[]
severity_boost	{}

Ensure 'App Service authentication' is set to 'Enabled'

Description

App Service authentication can prevent anonymous HTTP requests from reaching an app, or authenticate those with tokens before they reach the app. If an anonymous request is received from a browser, App Service will redirect to a login page. To handle the login process, a choice from a set of identity providers can be made, or a custom authentication mechanism can be implemented.

Rationale

By enabling authentication, every incoming HTTP request passes through it before being handled by the application code. It also handles authentication of users with the specified provider (Entra ID, Facebook, Google, Microsoft Account, and Twitter), validation, storage and refreshing of tokens, managing the authenticated sessions, and injecting identity information into request headers.

Impact

This is only required for apps that require authentication. Enabling it on a site like a marketing or support website will prevent unauthenticated access, which would be undesirable.

Adding an authentication requirement will increase costs and require additional security components to facilitate the authentication.

Audit Procedure

Using Azure Portal

1. Go to App Services or Function App.
2. Click the name of a function app.
3. Under Settings, click Authentication.
4. Ensure that App Service authentication is set to Enabled.
5. Repeat steps 1-4 for each function app.

Using Azure CLI

Run the following command to list function apps:

az functionapp list

For each function app, run the following command to get the authentication setting:

For v1 auth commands:

az webapp auth show --resource-group <resource-group-name> --name <function-app-name> --query enabled

For v2 auth commands:

az webapp auth show --resource-group <resource-group-name> --name <function-app-name> --query properties.platform.enabled

Ensure that true is returned.

Expected Result

App Service authentication should be enabled (return true).

Remediation

Using Azure Portal

1. Go to App Services or Function App.
2. Click the name of a function app.