Managed identity is the best practice regarding security when accessing resources on Azure. There are many ways you can use it for service to service communication. Sometimes though you can use nested managed identity in more complex scenarios like the one demonstrated below. In this guide we will enable managed identity on a virtual machine and we will access this managed identity within a container that runs on that specific virtual machine. This case can be useful in complex deployment scenarios where you have multiple containers inside a virtual machine and you want to deploy using managed identity on azure.
The first thing you will need is the system assigned managed identity on the virtual machine.
Then you can run your containers inside the virtual machine. In my case the containers are windows based as a result I will use the route print command to show the routing table.
Run the following Commands to expose the managed identity endpoint
$gateway = (Get-NetRoute | Where { $_.DestinationPrefix -eq '0.0.0.0/0' } | Sort-Object RouteMetric | Select NextHop).NextHop
$ifIndex = (Get-NetAdapter -InterfaceDescription "Hyper-V Virtual Ethernet*" | Sort-Object | Select ifIndex).ifIndex
New-NetRoute -DestinationPrefix 169.254.169.254/32 -InterfaceIndex $ifIndex -NextHop $gateway -PolicyStore ActiveStore # metadata API
After the successful add of the route the managed identity endpoint should be redirected in the gateway and from there you will be able to authenticate.
We can verify the procedure by executing a key vault managed identity secret retrieval.
$token = Invoke-WebRequest -Uri 'http://169.254.169.254/metadata/identity/oauth2/token?api-version=2018-02-01&resource=https%3A%2F%2Fvault.azure.net' -Headers @{Metadata="true"} -UseBasicParsing
$tokenvalue = ($token.Content | ConvertFrom-Json).access_token
Retrieve secret:
Invoke-WebRequest -Uri "https://test.vault.azure.net/secrets/testsecret/d9ce520dfdfdf4bdc9a41f5572069708c?api-version=7.3" -Headers @{Authorization = "Bearer $tokenvalue"} -UseBasicParsing
At last you can login using Managed Identity from the container using the powershell module.
References:
Co authored with Giannis Anastasiou @ Vivawallet
