I have an Azure Web App and an Azure SQL Server, both in the same subscription. Both of them are connected to the same VNet Subnet as shown in the below snapshots. The SQL Server is configured not to Allow Azure Resources and Services to access the server, as it should only permit access from either the connected subnet or a set of IP rules.
Unfortunately, the SQL Server is actively refusing any connection from the web app stating that the web app IP is not allowed to access the server.
The interesting thing is that I have the exact same configuration working on another subscription.
What could I be missing?
Snapshots:
1- Here you can see the web application connected to the "webapps" subnet
2- And here you can see the SQL Server connected to the same subnet
3- And that's the error I get
TLDR
The configuration is correct, but an app service restart may be required.
VNET Integration
The configuration of using a virtual network to connect a web app to a SQL database is correct: if the web app is connected to the same subnet/vnet which is allowed in the database's ACLs, and the Microsoft.Sql service endpoint is enabled on the subnet, the web app is able to communicate to the database. This is the whole reason for service endpoints: you do not need to configure with IP allowances on the database.
As to why the configuration still resulted in an error, it could be the order in which the resources were configured. We were experiencing the exact same setup and issue (which is what let me to this question)!
We connected our web app to the subnet/vnet but had not enabled the service endpoint on the subnet. We then added/allowed the subnet/vnet as an ACL in the database, during which we were prompted to enable the Microsoft.Sql service endpoint (we did). However, even after waiting ~20 minutes, we were still seeing the same connection issue.
However, once we restarted the app service, the issue went away and the web app could connect to the SQL database.
I suspect the issue is due to enabling the subnet's service endpoint after the app service was connected to the subnet. The app service must need a restart to refresh the app service's vnet config/routing.
Configuration NOT needed
Contrary to other answers, you do not need to configure firewall IP allowances nor enable access to Azure services and resources. In fact, there are downsides to both approaches:
Enabling access to Azure services and resources allows any Azure-based resource to connect to your database, which includes resources not owned by you. From doc:
This option configures the firewall to allow all connections from Azure, including connections from the subscriptions of other customers.
Unless you're using an App Service Environment (which is significantly more expensive than normal App Service plans), your web app's outbound IP addresses are neither static nor specific to your application. From doc:
Azure App Service is a multi-tenant service, except for App Service Environments. Apps that are not in an App Service environment (not in the Isolated tier) share network infrastructure with other apps. As a result, the inbound and outbound IP addresses of an app can be different, and can even change in certain situations.
The second point is further elaborated upon in this Github issue:
IPs are indeed shared with other App Service plans (including other customer's plans) that are deployed into the same shared webspace. The network resources are shared among the plans in a workspace even if the computing instances are dedicated (e.g. in Standard tier). This is inherent to the App Service multi-tenant model. The only way to have a dedicated webspace (i.e. outbound IPs) is to deploy an App Service plan into an App Service Environment (ASE) (i.e. Isolated tier). ASE is the only thing that offers true single-tenency in App Service.
So neither of the above options will truly harden your SQL database if you want to isolate communication from only your web app. If you have resources in the same subnet, using vnet integration is the correct way to solve the problem.
If resources cannot be in the same subnet, the solution is to use Private Endpoints.
Virtual networking in Azure is quite different from how it would work on premises.
I had similar problems in production environment and digging deep, the working solution (meeting security standards and create a secure connection to the database) was to create a private endpoint for SQL access in the virtual network. Then all the calls to the SQL were performed internally (it did not go on the internet), and the databases were denying all public calls.
In your case now, you deactivated the Allow Azure apps to access so when your app is trying to access the SQL the server checks the ip to find out if it is white listed or not. So fast solutions would be one of the following:
Enable Azure Web apps to access SQL
Find all outbound IPs of your web app and register them in you SQL firewall/ security settings.
If you talk about a proper production environment with security regulations I would suggest you go down the more tedious path of private endpoints.
You have to configure the outbound IPs from the app service in the sql fw.
You can find them under properties of your app service. Documentation.
The reason why is that the VNET integration doesn't give your app service an outbound IP in the VNET you configured it in, so the FW you configured doesn't work.
I have working web apps which access storage accounts and KVs. These storage accounts and KVs accept traffic from a particular subnet and the web apps have been configured to integrate with those subnets. I did face an issue where even after integration apps were not able to access these resources. What worked for me was, I changed the App service SKU from Standard to Premium and restarted the app. As you can see, it warns that "Outgoing IPs of your app might change". This is not guaranteed solution but it worked for me.. several times! Not sure about SQL server though. Private endpoint does seem like the way to go but you can give this a try.
How can I make the Azure Web App or web service to only through Application Gateway and disable direct access. So nobody will be able to access through the direct Fully Qualified Domain name such as mysite.azurewebsite.net?
Thanks for your help in advance.
You could set up Azure web app in the ILB Azure service environment. Azure ASE is a deployment of Azure App Service into a subnet in an Azure virtual network (VNet). This ILB ASE (Internal ASE) isn't exposed to the Internet. You can follow this blog to run an App Service behind a WAF-enabled Application Gateway.
This Web App isn't publicly accessible as it is sitting in a subnet
inside a Virtual Network and it isn't exposed to the internet. The
only way to access the site is through a Web Application Firewall
enabled Application Gateway.
Besides, If you just want to restrict public access to your Azure Web Apps with the IPSecurityRestrictions option, you can refer to this to get more references.
We have got VMs on Azure and services are running in there.
We are trying to deploy our MVC Web application to Azure App service, which accesses some of the services from the VM using the private IPs but it can't connect to the service hosted on the VM using the private IP. We were assuming that all of our resources will be in the same network, can anyone help with this?
Thanks
Azure App service are having two kinds of hostings
Single Tenant (App Service Environment) which is dedicated to the customer
Multi tenant ( shareable across other customer subscription inside a data center scale unit)
If your application is hosted as multi tenant application meaning app service URL {WEbAppName}.Azurewebsites.net then its internet facing application and if it needs to connect to any VNET (Virtual Network) hosted service then it needs to integrate to any or same VNET.
How to do App service VNET Integration:
https://learn.microsoft.com/en-us/azure/app-service/overview-vnet-integration#regional-virtual-network-integration
Once the App service integrated with VNET then ideally it has connectivity with all the services present inside the same VNET or with peered VNET.
How to confirm connectivity from App Service to VNET hosted resource.
Go to App Services application => Advanced tools or console => perform below commands sequence wise as the HTTP communication happens through this sequence:
nslookup {Destination_FQDN} {Optional-DNSServer}/nameresolver {Destination_FQDN} {Optional-DNSServer}
tcpping {Destination FQDN}
curl -v {DestinationFQDN}
Common Scenarios:
If you're receiving connection refused it means its NSG is not allowing the communication.
If you're getting request time out it means it could be due to firewall or no proper routes to reach to destination.
If its connection abort it means its intermediate device is not passing connection through.
Troubleshoot connectivity issues using Azure Network Watcher: https://learn.microsoft.com/en-us/azure/network-watcher/network-watcher-connectivity-portal
I have an on premise desktop application and I need it to hit Web APIs I have living in an App Service Web App (on an App Service Plan) in Azure.
My on premise resources are connected over a site to site VPN and I was wondering if there is a way I can call these Web API services(in an app service) directly over the VPN instead of going to the public endpoint.
The "normal" App Service Plan exists in a multi-tenant environment so this is not possible. You would need to use an ASE (App Service Environemnt) to use advanced networking features like VPN and NSG.
There is an azure web app in azure app service ASE. It is linked to a Vnet. And a point to site VPN between laptops/PCs connecting to the Vnet from outside cloud/ on premises to form an hybrid cloud setup of sorts. I am trying to see if a network file share / share folder in a PC/VM in that Vnet can be accessed from the web app (app service) . When I try this I get a unauthorized exception.
what are the options do I have ?
will having a cloud service web role instead of the web app help?
Or set up a domain controller + AD in the Vnet and add VMs to the domain and trying to access the share as a domain user( impersonation via code) ?
Also I am not sure if I connect my laptop/PC to this Vnet via point to site VPN , the laptop/PC will come under the domain that we created.
The use case behind this to show some on premises media( images, videos etc possibly bigger sizes ) on a web app running in azure PaaS.
Please share your thoughts and comments.