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.
Related
I have a scenario regarding web apps on Azure that I can't wrap my head around.
I have a Web App (not ASE) that is connected to a VNET/Subnet and I have setup access restrictions on the Web App so that only traffic from that specific VNET/Subnet is allowed. This works as expected and a 403 is thrown when trying to access the web app from the internet.
My problem is that the Web App is no longer accessible from the on-premises setup anymore either, and I am unsure how to facilitate that. I don't like to use IP whitelisting to enable access, but I don't know the alternatives.
Anybody with experience on how to access a restricted Web App from an on-premises system? All the examples I could find are about accessing on-premise data from a VNET, not the other way around.
Illustration of setup:
On-premises server --> VPN Gateway in Azure --> VNET --> Web App in VNET -x-> Internet
Private Endpoints are your friends :)
I see you wanna set a S2S connection using vpn to allow access to your on-premises networks(subnets)
You should create a local network gateway representing your on-promises and also you should verify your firewall devices is supported by azure to make sure that the configuration works. Supported Vpn Devices by Azure
Earlier we had Windows App Service Plan and App services within the plan have VNet-integration enabled to connect to on-premises services. It used to reach on-premises services from the app service by resolving the domain names.
Recently Microsoft announced that regional VNet-integration for Linux App Services feature is Generally Available. we tried to migrate all our windows app services to Linux. Fortunately, we did not face any issues with subnet-delegation. But after the migration, the Linux app services are not able to reach on-premises service. It says UnknownHostException from the java code and tried from Kudo console, there also it says domain name is not being resolved. and we noticed that logs are not being pushed to Application Insights.
The next day, we just tried with IP address instead of domain names, it worked. For Application Insights, we could not do anything. To just confirm for Application Insights, we disconnected the vnet-integration for app service, then the app is able to send logs to application insights.
So what would be the problem?
You cannot create a Linux Web App in an App Service plan already hosting non-Linux Web Apps. I suppose you have created new app service plan and app service for Linux to manage regional VNet Integration.
Your app cannot resolve addresses in Azure DNS Private Zones without
configuration changes
The feature is fully supported for both Windows and Linux web apps.
All of the behaviors act the same between Windows apps and Linux apps.
Also, from https://learn.microsoft.com/en-us/azure/virtual-network/virtual-networks-name-resolution-for-vms-and-role-instances
In the scenario of name resolution from App Service Web Apps in one virtual network to VMs in a different virtual network, it requires customer-managed DNS servers forwarding queries between virtual networks for resolution by Azure (DNS proxy). See Name resolution using your own DNS server.
By default, app service use the Azure providing DNS server in the delegated VNet, it don't know your on-premise DNS records. You need to deploy a custom DNS server in your Azure virtual network and target network to forward the DNS query.
For Application Insights, you could check if you have a rule blocking the outbound call to application insights if you have set the app setting WEBSITE_VNET_ROUTE_ALL to 1. Refer to this.
If you integrate your app with your VNet, the default behavior remains
as it was. You would only be able to reach RFC1918 addresses
(10.0.0.0/8, 172.16.0.0/12, 192.168.0.0/16) and service endpoints.
Just like with Windows, the feature now supports outbound calls into
the VNet on non-RFC1918 addresses as well. To reach all addresses you
need to set the app setting WEBSITE_VNET_ROUTE_ALL to 1, your app will
then enable all of the outbound traffic from your app to be subject to
NSGs and UDRs.
Finally, all of a sudden it got resolved by itself. And when we asked Microsoft Support, its mentioned that they have done recent network update in their backbone network.
Since we did not know what was the issue, we did not migrate Win to Linux in our higher env, we rollback to Windows and there was no issue after that.
We have an App Service running in Azure that hosts a website. We've recently had a security review on the web site and one of the items found was that the end point below was exposed.
https://<appName>.azurewebsites.net:8172/msdeploy.axd
The recommendation is that this end point should be blocked and using a whitelist to allow limited access (e.g. the build machine that deploys to Azure). How do I block this end point?
After discussions with Microsoft support it appears that port 8172 is enabled for backwards compatibility with old versions of MsDeploy. This port is being phased out and will be open sometimes and not other times.
The fix was for us to create a new resource group, app service plan and app services multiple times until we ended up a server that had the port closed. This was frustrating but ultimately it did resolve the issue.
You could use IP level limitation in the Azure App Service access restrictions to allow limited IP addresses or VNet access to your app service. In this case, it will work on all the applications in your app service.
For some specific endpoint access control, perhaps, you need to control it with access authorization in your application code. Read Tutorial: Authenticate and authorize users end-to-end in Azure App Service and Managing access to apps.
Alternatively, you select to use Application Gateway integration with service endpoints. In this case, you only want the front end to be accessible to your end-users. The back-end should be locked down so it is only callable from the front-end. Also the front end subnet support NSG, you could restrict the end-users with IP and port to access your front end, meanwhile, it will limit access to your endpoint. See Securing Back-end App Service Web Apps with VNets and Service Endpoints for more details.
Hope this helps you.
I have been messing around with Azure trying to get a web app up and running. My plan was to create a WAF and site the web app behind that, each in a seperate subnet and then to use the service endpoint tech to point the web app to a database.
I have been stopped in my tracks almost straight away with the revelation that if i want to use a WAF in front of the web app i have to configure the networking in the web app but when i choose a vnet it says that no gateway is configured for the selected VNET.
My question being is do i have to use point to site VPN to get this setup working? i thought that it would work like
INTERNET ---> VNET ----> subnet ----> WAF -----> subnet -----> web app ----> service endpoint ------> DB
but that doesnt seem to be the case. I am not keen on the idea of having to install a client certificate on every machine in our network that might want to access this website (it is currently internal). I suppose i am looking for the best of both worlds. Accessible from the internet but having the added comfort of having something like a WAF sat in front of it to make up for any security inadequacies which might exist somewhere in said app.
Thanks
As far as I know, you could not deploy a web app in a VNet unless you are using the App Service Environment(Isolated). App VNet integration could not do it. It allows you to securely access resources in a VNet. For example, you have a database on an Azure VM in a private VNet. You could not access it from Azure web app to this database if this database is not available publicly, but you could reach it via app VNet integration.
VNet service endpoints is another different service. Endpoints allow you to secure your critical Azure service resources to only your virtual networks. If you enable such service endpoint like Azure SQL database( which differs from the database on Azure VMs) in a VNet, this means only the resource in these authorized VNets could access your SQL database unless you add an exclusion like the public IP address in the firewall of the database.
In this case, you could put a Public facing Azure app gateway at the high level of the web app service, then add the Azure app gateway public IP in the IP restriction of the web app.This will restrict to access to web app via Azure web app gateway over the Internet. Also, you could control the network inbound and outbound in Azure app gateway subnet NSG. See Network security groups on the Application Gateway subnet if you want to add an NSG to the app gateway subnet level. I think these are enough if you just want to create a WAF and site the web app behind that.
Furthermore, if you want to let web app privately access the Azure SQL database. You could deploy a web app in an ASE, then enable the VNet service endpoint for Azure SQL database. App VNet integration does not need to use it with the service endpoint.
If you want to use Azure WAF with Azure App Service (multi-tenant) you can, you just need to ensure you are supplying the host header with your request.
If you want you Azure Web App on a VNet, you will need to run your Azure Web App on an App Service Environment (Isolated). This version of Azure Web App is more expensive but allows you to apply NSG's to the VNet to fully control access to your web app. Personally I think WAF w/ Azure App Service (multi-tenant) should meet your needs.
We have it all documented here:
https://learn.microsoft.com/en-us/azure/application-gateway/application-gateway-web-app-overview
https://learn.microsoft.com/en-us/azure/application-gateway/configure-web-app-portal
I have multiple web apps on Azure that I want to put behind an Application Gateway in order to use a single domain name with path routing.
However, my web apps needs to connect to a db outside of Azure. So I wonder what will the IP of the requests from these web apps to the db would be? I hope it will be the gateway public IP so I only have to authorize one IP at my db provider but I don't find any docs to confirm it (or not).
So I wonder what will the IP of the requests from these web apps to
the db would be?
If you want your web apps to connect a database outside Azure, you may need App service Environment. Because the Web Apps need VNet to connect other resources. Also, due to the date base is outside Azure , you need to create VPN gateway to connect it. This connection is between the Web App and the database, not Application Gateway and Database.
So, the IP of requests from those Web Apps is not the IP of Application Gateway, It depends on the VNet in App Service Environment.
This picture explains how this environment works:
I hope it will be the gateway public IP so I only have to authorize
one IP at my db provider but I don't find any docs to confirm it (or
not).
Also, if you still want to use one IP to connect other resources, you can also add Internal Loadbalancer to achieve that.
You can see more details about Integrating your ILB ASE with an Application Gateway to help your deploy resources.
Please let me know if this answer helps.
I would suggest using the Azure Web App's Hybrid connection. This provides a TCP tunnel in a secured fashion between your azure web app and your SQL db. There is a service bus in between and you have to install the relay agent in your network that does the outgoing communication to this service bus.
Hybrid connection diagram
Details are at:
https://learn.microsoft.com/en-us/azure/app-service/app-service-hybrid-connections
The app gateway's public IP address can't be leveraged nor is it necessary to manage connections between Azure Web Apps and databases outside of Azure. The web apps have their own IP addresses.
On another note, my blog post may be useful to understand how the architecture and configuration between app gateway and azure web app.