Retrieving Managed Identity Access Tokens For Azure Web Apps Using PowerShell Console

If you’re working with Azure Web Apps and securing between services using managed identity, formerly known as Managed Service Identity (MSI), it can be useful to retrieve an access token on behalf of an application. We can accomplish this via PowerShell.

Credit

This is adapted from https://techcommunity.microsoft.com/t5/azure-developer-community-blog/understanding-azure-msi-managed-service-identity-tokens-caching/ba-p/337406 authored by Stephane Eyskens (@stephaneeyskens), big thanks for sharing this!

Code

Update the resource of https://management.azure.com/ as needed for your use case and paste into a PowerShell prompt:

$ProgressPreference="SilentlyContinue"
$secret = (get-item env:MSI_SECRET).value
$endpoint = (get-item env:MSI_ENDPOINT).value
$headers = @{Secret = "$($secret)"}
$req=Invoke-WebRequest -UseBasicParsing -Uri "$($endpoint)?api-version=2017-09-01&resource=https://management.azure.com/" -Headers $headers|ConvertFrom-JSON
$req
$req.access_token

You can access a PowerShell prompt via https://your-app-name.scm.azurewebsites.net/DebugConsole/?shell=powershell (replace your-app-name).