Control: 9.1 Ensure App Service Authentication is set up for apps in Azure App Service

Description

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

By enabling App Service 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(Azure Active Directory, Facebook, Google, Microsoft Account, and Twitter), validation, storing and refreshing of tokens, managing the authenticated sessions and injecting identity information into request headers.

Remediation

From Console

1. Login to Azure Portal and go to App Services.
2. Click on each App.
3. Under Settings section, click on Authentication(classic).
4. Set App Service Authentication to On.
5. Choose other parameters as per your requirement and click on Save.

From Command Line

To set App Service Authentication for an existing app, run the following command:

az webapp auth update --resource-group <RESOURCE_GROUP_NAME> --name <APP_NAME> --enabled true

Note

• In order to access App Service Authentication settings for Web app using Microsoft API requires Website Contributor permission at subscription level. A custom role can be created in place of website contributor to provide more specific permission and maintain the principle of least privileged access.
• By default, App Service Authentication is disabled.
• If you need more flexibility than App Service provides, you can also write your own utilities. Secure authentication and authorization require deep understanding of security, including federation, encryption, JSON web tokens (JWT) management, grant types, and so on.