One of the technical aspects one needs to understand is how to configure network isolation for Web Apps and Azure Functions. Network isolation is critical to protect resources from unauthenticated access and potential threats. It limits what resources can communicate with your app, providing an additional security layer to your Azure environment.
1. Networking in Web Apps and Azure Functions
Web Apps and Azure Functions in Azure are hosted in a secure environment, with Azure App Service Environment providing a fully isolated and dedicated environment for securely running App Service apps at a high scale. It includes web apps, mobile app backends, and RESTful APIs, with additional capabilities like network isolation and improved scaling.
2. VNet Integration and Access Restrictions
Azure provides VNet (Virtual Network) Integration and Access Restrictions for isolating your apps. VNet Integration allows your app to access resources in or through a VNet, while Access Restrictions enable you to define a priority ordered allow/deny list that controls network access to your app.
| Feature | VNet Integration | Access Restrictions |
|---|---|---|
| Purpose | To access resources in your VNet. | To provide priority list of network access controls. |
| Network types | VNet | CIDR blocks, Azure VNets |
| Outbound network | Yes | No |
| Inbound network | No | Yes |
3. Configuring VNet Integration
To set up VNet Integration for your apps, follow this process:
- In the Azure portal, navigate to your app’s management page.
- In the left pane, under Settings, select Networking > VNet Integration > Click on “Click here to configure”.
- You’ll see a list of your VNet with Subnets. Select the VNet and Subnet, then click “OK”.
Remember, the targeted subnet should not contain any other resources.
4. Configuring Access Restrictions
To limit network access to your app using Access Restrictions, follow these steps:
- In the Azure portal, go to your app’s management page.
- Select Networking > Access Restrictions > Click on “Configure Access Restrictions”.
- Click on ‘+ Add rule’ under either ‘IPv4 Restrictions’ or ‘IPv6 Restrictions’ based on your requirement.
- Enter the details like Name, IP address, and Subnet, then click “Add rule”.
Add a rule for each IP address range or VNet that you wish to allow.
5. Service Endpoints and Private Endpoints
You can also secure your Azure Functions’ network access using Azure Service Endpoints or Azure Private Endpoints.
-
Azure Service Endpoint
: This extends your VNet private address space and the identity of your VNet to the Azure services, over a direct and secured connection. For example, to turn on service endpoints for Azure Storage, at your Azure Storage account, navigate to Firewall and virtual networks, then select Selected networks, and add the subnet you want to give access to.
-
Azure Private Endpoint
: A network interface that you connect to your VNet, providing a private IP address from your VNet to an Azure Service. To set up a Private Endpoint, create a new private endpoint from within your app’s management blade or at the private endpoint’s Azure portal blade.
In conclusion, to harden the security posture of your Azure environment, it’s crucial to understand and appropriately use the networking features offered by Azure. Configuring network isolation effectively will help to bar unauthorized access to your apps, thereby providing a safeguard against potential threat vectors in your Azure Web Apps and Azure Functions.
Practice Test
True or False: Network isolation in Azure Web Apps and Azure Functions is provided using Azure Virtual Networks (VNets).
- True
- False
Answer: True
Explanation: Network isolation using VNets is a fundamental part of the security boundaries for Azure Web Apps and Functions. They allow you to securely host and access resources within your own private network space in Azure.
Which of the following are required to configure network isolation for Web Apps and Azure Functions? (Multiple Select)
- A) A Virtual Network
- B) Azure Active Directory
- C) Service Plan
- D) Private Endpoint
Answer: A, C, D
Explanation: Setting up network isolation requires a virtual network for isolation, a Service Plan for pricing, and Private Endpoints to establish a private link to provide secure connectivity.
True or False: Azure Functions cannot be integrated with Azure Virtual Network.
- True
- False
Answer: False
Explanation: Azure Functions can be integrated with Azure Virtual Network via VNet Integration.
What feature of Azure should be used to secure inbound traffic to Azure Functions and Web Apps?
- A) Application Gateway
- B) Azure Firewall
- C) Network Security Group
- D) Private Link
Answer: D, Private Link
Explanation: Private Link allows you to access Azure (PaaS) services, like Azure Functions and Web Apps, over a private endpoint in your virtual network.
True or False: Azure Service Endpoints provide network isolation for Azure Web Apps and Azure Functions.
- True
- False
Answer: False
Explanation: Azure Service Endpoints do not provide network isolation. They simply extend your virtual network private address space and identity to the services over a direct connection.
True or False: In Azure, all applications deployed in a VNet are fully isolated from the internet by default.
- True
- False
Answer: False
Explanation: By default, all services inside a VNet can connect outbound to the internet. Network isolation is achieved through configurations like implementing Private Endpoints, network security groups etc.
Which tool can be used to force traffic from your VNet to go out to the internet through a specific IP?
- A) Azure Firewall
- B) BGP
- C) NAT Gateway
- D) Azure Private Link
Answer: C, NAT Gateway
Explanation: NAT Gateways can route traffic from your VNet to the internet through a specific, user-defined public IP.
True or False: Azure Functions and Web Apps can directly use a private IP in your VNet.
- True
- False
Answer: False
Explanation: They cannot use a private IP directly. However, they can access resources in your VNet over a Private Endpoint, which uses a private IP.
What Azure feature is capable of providing network isolation between two subnets in the same VNet?
- A) Azure Firewall
- B) Network Security Group
- C) Virtual Network Peering
- D) Azure Private Link
Answer: B, Network Security Group
Explanation: Network Security Groups can be used to control inbound and outbound traffic to resources within VNets.
True or False: Regional VNet Integration is only supported with Function apps and Web apps that are hosted in a Standard, Premium, or Isolated app service plan.
- True
- False
Answer: True
Explanation: Azure’s Regional VNet Integration allows apps that are hosted in Supported plans–Standard, Premium, and Isolated–to integrate with resources in a VNet.
Interview Questions
What is network isolation in Azure?
Network isolation is the process of restricting network access to enhance security. In Azure, the service instance’s access is limited to a specific network, thereby protecting data from an unauthorized resource.
How is network isolation implemented in Azure Web Apps and Azure Functions?
Network isolation in Azure Web Apps and Azure Functions is implemented using service endpoints, private endpoints/VNet integration, or Azure App Service Environment(ASE).
What is the Azure Private Endpoint?
The Azure Private Endpoint is a network interface that connects your application to an Azure service in your virtual network (VNet). The connection over Private Endpoint uses a private IP address from your VNet, ensuring network isolation while providing a secure route to your Azure service resource.
What is the purpose of Azure Service Endpoint?
Azure Service Endpoint helps to secure Azure service resources to your virtual network by eliminating data exposure over the public internet. It extends your VNet private address space and the identity of your VNet to the Azure service.
What is Azure App Service Environment(ASE)?
Azure App Service Environment(ASE) is an Azure App Service feature that provides a fully isolated and dedicated environment for running App Service apps securely.
Can we install Azure Functions in an Azure App Service Environment (ASE)?
Yes, Azure Functions can be hosted in an Azure App Service Environment providing network isolation and improved security.
How does VNet Integration provide network isolation?
VNet Integration gives the Azure Web App access to resources in or through a VNet. The apps make outbound calls to the internet using the identities and firewall rules applied to VNet, so they’re isolated.
How many IP addresses are required in the subnet to configure Azure Private Endpoint?
At least five continue IP addresses are required in the subnet to configure Azure Private Endpoint.
What are the primary requirements for VNet Integration?
The primary requirements for VNet Integration include a dedicated subnet and the selected VNet must not force tunnel traffic to on-premises.
Is it possible to use Azure Private Endpoint for Azure Functions?
Yes, it is possible to use Azure Private Endpoint for Azure Functions to securely access function apps over Private Link, ensuring the function apps and data don’t go over the internet.
Where are Azure Functions and the hosting plan deployed when using an App Service Environment (ASE)?
Both Azure Functions and their hosting plan are deployed inside an Azure Virtual Network (VNet).
What types of apps can use VNet Integration?
Web apps, function apps, and API apps in a Standard, Premium, or Isolated pricing plan can use VNet Integration.
How can we secure inbound traffic to our web apps in Azure?
We can secure inbound traffic to our web apps in Azure using Azure Private Link, as it provides a secure and scalable method for consuming services on the Azure platform.
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