AZT404.1 - Principal Impersonation: Function Application

By utilizing a Function Application configured with a managed identity or other identity provider, an attacker can execute Azure operations on a given resource.

Resource

Function Application

Actions

• Microsoft.Web/sites/hostruntime/vfs/run.csx/write
• Microsoft.Web/sites/functions/write
• Microsoft.Web/sites/write

Examples

Az PowerShellAzure CLIAzure REST APIAzure Portal

Update-AzFunctionApp

az functionapp update

PUT https://management.azure.com/subscriptions/{subscriptionId}/resourceGroups/{resourceGroupName}/providers/Microsoft.Web/sites/{name}?api-version=2021-02-01

Detections

Logs

Data Source	Operation Name	Action	Log Location
Resource	Write Run.csx	Microsoft.Web/sites/hostruntime/vfs/run.csx/write	Azure Activity Log
Resource	Update Web Apps Functions	Microsoft.Web/sites/functions/write	Azure Activity Log
Resource	Update website	Microsoft.Web/sites/write	Azure Activity Log

Queries

Log Analytics

AzureActivity 
|where OperationNameValue=="Microsoft.Web/sites/hostruntime/vfs/run.csx/write" or OperationNameValue=="Microsoft.Web/sites/functions/write"
or OperationNameValue=="Microsoft.Web/sites/write"

Additional Resources

https://docs.microsoft.com/en-us/azure/app-service/overview-managed-identity?tabs=ps%2Cdotnet