I have 2 app service plans in the same Azure region running 1 app each - web frontend on one, API on the other.
I want to use access restrictions on the API to only allow access from the front end app.
I set access restriction rules using all the outgoing IP addresses associated with the frontend app (I note that these are exactly the same as the outgoing IP addresses on the API app as well) however when the frontend app tries to contact the API I get an error:
403 forbidden 'The web app you have attempted to reach has blocked your access.'
The 2 apps can communicate as normal when the access restrictions are removed.
I turned on diagnostic settings and ran a query on IP blocking by the app.
Turns out that the FE app is using an IPv6 address instead of the v4 addresses listed in the app properties.
This is because the app has a vnet integration set up connecting to a Subnet delegated to Webservice/serverfarm.
Azure does not make it obvious that using delegated subnets forces an integrated app to use IPv6 and there does not appear to be a way to discover what v6 addresses may be in use. MS forum response suggests any firewall rule for a web app attached to a delegated subnet should allow ALL IPv6 addresses (!!) as a way of working around the problem.
https://learn.microsoft.com/en-us/answers/questions/493483/why-is-my-azure-web-app-showing-an-ipv6-outbound-i.html
You can control the IP address of outbound traffic from your FE web app by using regional VNet integration together with a virtual network NAT gateway to direct traffic through a static public IP address. Regional VNet integration is available on Standard, Premium, PremiumV2 and PremiumV3 App Service plans. To learn more about this setup, see NAT gateway integration.
Once you FE web app has a static IP you can use that on the API web app restriction in an ALLOW rule.
If your requirement fits, you may also leverage Service Endpoints.
With service endpoints,to ensure inbound traffic to your API app comes only from the subnet used by your front-end web app.
With this route, you need to use VNet Integration with your front end app and service endpoints with your API app. Set service endpoints on the integration subnet used by your Front End application. This solution is fast to set up and easy as well.
-This feature works together with IP access restrictions. Service endpoints aren't compatible with remote debugging. There are some considerations you need to make, you may take a look at them here and also other combination of networking features available on App Service and related scenarios.
As a side note:
-IP-based access restriction rules only handle virtual network address ranges when your app is in an App Service Environment. If your app is in the multitenant service, you need to use service endpoints to restrict traffic to select subnets in your virtual network.
-On App Service, you could have those two separate apps in the same App Service Plan (ASP), since you pay only for ASP, saving costs.
So, you can continue to add apps to an existing plan as long as the plan has enough resources to handle the load. The apps in the same App Service plan all share the same compute resource.
Related
I deploy my web application to an App Service instance on Premium tier. My web application makes outbound requests to external resources on the Internet.
In order to secure the connection with one of these external resources so I can reach it with a private IP address, my plan is to create a Site-to-Site VPN from Azure to Oracle Cloud Infrastructure (where the external resource resides). Then, I plan to use the VNET Integration for outbound traffic and connect my App Service to my VPN.
My question is - will the web application still be able to reach the other external resources on the Internet with their public IPs? I believe the answer is related to routing tables but I can't wrap my mind around it.
Just because you integrate a Regional VNet (I'm assuming) doesn't mean the app service won't be able to make outbound connections. Pretty much like
When you integrate your app service with your VNet that has the site-to-site VPN, traffic from your app service will traverse the Azure network rather than going out to internet, assuming your app service is using an RFC1918 address for your infrastructure. If you want to secure the traffic even further, then your app service would need to be hosted inside an App Service Environment
To clarify what I'm not asking about, there's alot of documentation about using endpoints to expose apps in a App Service Plan to a vnet, which is useful for private communication between vnet hosted VMs or other resources outside the app service plan.
What I'm asking about is specifically communication between two apps inside the same app service plan. So if we had PlanA, and AppB and AppC both deployed to that plan, then if PlanA scales to two instances, each instance would have both AppB and AppC inside it. Very similar to an IIS farm hosting multiple applications.
If I want to disable public access for AppC, but still allow AppB to call AppC(imagine if AppC is a API service and AppB is a front end web app), is that possible? How would you resolve that call if the AppC doesn't have a public IP? Would the domain appC.azurewebsites.net resolve to a privateIP that AppB can access?
The fact that two app services run in one app service plan means only that these app services can share the same set of computing resources (CPU, memory, etc.) and it does provide any network isolation or private IP addresses within an app service plan.
If you want to keep the existing setup and restrict access to AppC, you can whitelist IP addresses of AppB as follows:
Go to the AppB in Azure Portal, click Properties and copy the list of Outbound IP addresses.
Go to the AppC, click Networking -> Access Restrictions and deny access to everything apart from the outbound IP addresses you copied in step 1.
The domain appC.azurewebsites.net will still have a public IP address but Azure will only allow accessing it from the IP addresses you configured and return 403 error to any other client.
However, if you want to have a truly private endpoint and more granular control over routing configuration, then consider integrating your app services with Azure virtual network as described here. Virtual networks are not limited to VMs, they can be used for app services too.
I'm trying to secure my containerized web app with a Premium V2 App Service Plan. I've enabled Service Endpoints for an integration subnet for the different App Services to restrict incoming traffic from each other except for the frontend (so all of them are integrated with the VNet and all have incoming traffic restricted to that VNet except for the frontend).
I have also other Azure services like Azure Functions or a Storage Account that can have inbound traffic restricted by using those Service Endpoints. However, One of the App Services calls an external 3rd party API that lies on Azure too. That API may or not be behind a static IP. However, it has a Custom Domain associated.
The problem arises when I try to connect to that API from one of the VNet integrated App Services. As the destination IP is inside one of the IP ranges that are added to the routing with the use of a Service Endpoint, traffic is sent via that Service Endpoint instead of simple Azure routing. I've tried overriding the route with a Route Table associated to that subnet but that seems not to be possible, with or without a NAT Gateway attached to the subnet. I guess Azure routing is prioritized here. I'm sure the route is not effective as I used it on a different subnet where I deployed a VM.
Is there any way I can use that Service Endpoint for my internal traffic only so it's not used when it goes to an Azure hosted API or I need to switch to a different approach like Private Endpoints or an ASE?
I am unsure what you're looking for but if you want to explicitly define routes you should try using app services setting "WEBSITE_VNET_ROUTE_ALL" = 1 which overrides the default precedence of routing and makes sure that every outbound call follows the route defined inside route table of subnet.
Use the following steps to add the WEBSITE_VNET_ROUTE_ALL setting in your app:
Go to the Configuration UI in your app portal. Select New application setting.
Enter WEBSITE_VNET_ROUTE_ALL in the Name box, and enter 1 in the Value box.
When WEBSITE_VNET_ROUTE_ALL is set to 1, outbound traffic is still sent from the addresses that are listed in your app properties, unless you provide routes that direct the traffic elsewhere.
We've been able to ask the 3rd party to disable blocking rules. It turns out they had a rule that blocked this specific traffic.
I already tried changing that setting, but didn't try putting a route table on it. However, it'd make no difference as I can't define a list of allowed outbound IPs belonging to Azure since we have no static IP to call.
I have azure app service which runs .net core web api. This api access several external API s to get data and those external services has to whitelist the outbound ip addresses of my app service.
Azure app service has several outbound ip addresses and it can be change when upgrade/downgrade app service or when make internal changes like changing app service plan or resource group.
Is there any solution in azure to setup this app service behind a forward proxy ?, so i can share the IP of the forward proxy to external parties.
I think the best way would be to add all App services under a virtual network and create a Virtual Network Gateway to all outbound connections.
This would potentially need below azure services to be created:
- Virtual network
- Subnet
- Virtual Network gateway
- Routing tables (to route traffic via Gateway)
A better way would be sharing a domain name rather than IP address. Here's how to configure it directly in the Azure Portal:
https://learn.microsoft.com/en-us/azure/app-service/app-service-web-tutorial-custom-domain
You can also add an API Management in front of your web app and use it as API gateway and also apply policies on it.
https://learn.microsoft.com/en-us/azure/api-management/configure-custom-domain
In Azure, I have 3 Web Apps (for simplicity):
Frontend website
Endpoint 1
Endpoint 2
The frontend website requests data from an endpoint.
Both endpoints are synchronized all the time (outside the scope of this question), but sometimes I need to do some maintenance on them, which gives me some downtime.
Can I somehow setup a loadbalancer only my frontend website can see, and get any of the online endpoints - like this:
The last line of this article says Internal Load Balancers might be the fit:
Can I use ILB on PaaS services (Web/Worker roles)?
ILB is designed to work with web/worker roles as well, and it is available from SDK 2.4 onwards.
Does anyone know of a guide, or have tried making this with Web Apps?
I dont think this is something you can achieve "natively" with load balancers. App Services are not actually bound to the VNet. Previously you could only use point-to-site vpn to connect them to vnet, right now there is a new vnet integration feature in preview which might allow you to use internal load balancers, but I doubt that, because they (load balancers) only allow to use virtual machines\scale sets\availability sets as backend pools.
Application gateways can be bound to the App Services. And they can be internal as well. You'd also need to restrict App Service(s) to receive traffic from anything that is not you Application gateway.
You can use traffic manager\front door for this sort of load balancing, but the endpoints won't be private