Cis Azure Compute 2.4.13

Ensure deployment slot is integrated with a virtual network

Description

Integrate function app deployment slots with a virtual network to enable access to resources in or through a non-internet-routable virtual network.

This recommendation applies to function apps using the Premium or Dedicated (App Service) plans, which support deployment slots and virtual networking.

Rationale

Integrate function app deployment slots with a virtual network for increased security and control.

Impact

Additional configuration may be required to ensure that traffic is routed properly.

Audit Procedure

Using Azure Portal

1. Go to App Services or Function App.
2. Click the name of a function app.
3. Under Deployment, click Deployment slots.
4. Click the name of a deployment slot.
5. Under Settings, click Networking.
6. Under Outbound traffic configuration, next to Virtual network integration, ensure that a virtual network and subnet name are displayed.
7. Repeat steps 1-6 for each function app and deployment slot.

Using Azure CLI

Run the following command to list function apps:

az functionapp list

For each function app, run the following command to list deployment slots:

az functionapp deployment slot list --resource-group <resource-group-name> --name <function-app-name>

For each deployment slot, ensure that virtualNetworkSubnetId is set to a virtual network subnet ID.

Expected Result

The virtualNetworkSubnetId property should be set to a valid virtual network subnet ID.

Remediation

Using Azure Portal

1. Go to App Services or Function App.
2. Click the name of a function app.
3. Under Deployment, click Deployment slots.
4. Click the name of a deployment slot.
5. Under Settings, click Networking.
6. Under Outbound traffic configuration, next to Virtual network integration, click Not configured.
7. Click Add virtual network integration.
8. Select an existing App Service Plan connection, or select New connection and select a subscription, virtual network, and subnet.
9. Click Connect.
10. Repeat steps 1-9 for each function app and deployment slot requiring remediation.

Default Value

By default, virtual network integration is not configured.

References

1. https://learn.microsoft.com/en-us/azure/azure-functions/functions-networking-options
2. https://learn.microsoft.com/en-us/azure/app-service/overview-vnet-integration
3. https://learn.microsoft.com/en-us/azure/app-service/configure-vnet-integration-enable
4. https://learn.microsoft.com/en-us/cli/azure/functionapp

Profile

Level 1 | Automated