Cis Azure Compute 2.4.11

Ensure managed identities are configured

Description

Managed identities from Microsoft Entra ID allow function app deployment slots to securely access other Azure services without the need to provision or rotate any secrets.

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

Rationale

Using managed identities with function app deployment slots eliminates the need to store and manage credentials to access Azure resources.

Impact

Minor administrative overhead to configure and manage role assignments for managed identities.

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 Identity.
6. Ensure that in the System assigned pane, the Status is set to On, and an Object (principal) ID is displayed, or that in the User assigned pane, a managed identity is listed.
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 identity contains type set to SystemAssigned, UserAssigned, or both.

Expected Result

The deployment slot should have a managed identity configured, either system-assigned, user-assigned, or both.

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 Identity.
6. To add a system assigned managed identity:
   1. In the System assigned pane, under Status, click On.
   2. Click Save.
   3. Click Yes.
7. To add a user assigned managed identity:
   1. In the User assigned pane, click Add.
   2. Use the filter box to search for a managed identity.
   3. Select the identity.
   4. Click Add.
8. Repeat steps 1-7 for each function app and deployment slot requiring remediation.

Using Azure PowerShell

For each deployment slot requiring remediation, run the following command to assign a system-assigned managed identity:

Set-AzWebAppSlot -ResourceGroupName <resource-group-name> -Name <function-app-name> -Slot <deployment-slot-name> -AssignIdentity $true

Default Value

Managed identities are disabled by default for function app deployment slots.

References

1. https://learn.microsoft.com/en-us/security/benchmark/azure/mcsb-identity-management#im-1-use-centralized-identity-and-authentication-system
2. https://learn.microsoft.com/en-us/azure/app-service/overview-managed-identity
3. https://learn.microsoft.com/en-us/cli/azure/functionapp
4. https://learn.microsoft.com/en-us/powershell/module/az.websites/set-azwebappslot

Profile

Level 1 | Automated