Two weeks ago, I wrote about the new VNet Integration feature on Azure App Services. This has everything to do with being able to lock down downstream systems to only accept traffic coming from a specific VNet under your control, as opposed to a set of public IP addresses that are managed by Microsoft, shared with other tenants, and prone to change.
Today it’s time to follow up on that. Because we may not only want to protect downstream systems, but also the web apps themselves. For public web apps, that protection typically does not exist at the network level, but wouldn’t it be nice if there was some network-level protection option available for private apps? Until now, the only real way to do that was by employing a very pricey App Service Environment. An ASE sits in your own VNet with all the security and flexibility this brings, but it is exceedingly expensive.
But the need to actually deploy an ASE has now disappeared if all you want to do is lock down access to a web app so that it’s only available from your network: the Microsoft.Web service endpoint has just become available!
That’s right: you can now configure a service endpoint for Azure App Services on one or more of your subnets:
Then, on the Web App, you can configure IP restrictions to only allow your subnet to access the Service Endpoint:
So, there you have it: not only can you rigorously protect access to downstream systems while allowing traffic originating from Azure App Services; you can now also protect Azure App Services itself to only allow internal traffic!