AZManagedIdentity

Azure resources like Virtual Machines, Logic Apps, and Automation Accounts can be assigned to either System- or User-Assigned Managed Identities.

This assignment allows the Azure resource to authenticate to Azure services as the Managed Identity without needing to know the credential for that Managed Identity. Managed Identities, whether System- or User-Assigned, are AzureAD Service Principals.

Abuse Info

You can modify the Azure RM resource to execute actions against Azure with the privileges of the Managed Identity Service Principal.

It is also possible to extract a JSON Web Token (JWT) for the Service Principal, then use that JWT to authenticate as the Service Principal outside the scope of the Azure RM resource. Here is how you extract the JWT using PowerShell:

$tokenAuthURI = $env:MSI_ENDPOINT + "?resource=https://graph.microsoft.com/&api-version=2017-09-01"
$tokenResponse = Invoke-RestMethod -Method Get -Headers @{"Secret"="$env:MSI_SECRET"} -Uri $tokenAuthURI
$tokenResponse.access_token

We can then use this JWT to authenticate as the Service Principal to the Microsoft Graph APIs using BARK for example.

Opsec Considerations

This will depend on which particular abuse you perform, but in general Azure will create a log event for each abuse.

References

• https://attack.mitre.org/techniques/T1078/
• https://posts.specterops.io/managed-identity-attack-paths-part-1-automation-accounts-82667d17187a
• https://m365internals.com/2021/11/30/lateral-movement-with-managed-identities-of-azure-virtual-machines
• https://github.com/BloodHoundAD/BARK