Automated Let's Encrypt certificate generator on Azure Functions for App Services

Useful for App Services based on Container / Docker

Setup

• create Azure Function App (with Hosting Plan: Consumption)
• in Azure Function App add:
  • Application settings:
    • WEBSITE_NODE_DEFAULT_VERSION = 8.10.0
    • OPENSSL_PATH = D:\Program Files (x86)\Git\usr\bin\openssl.exe
    • TEST = false
  • Connection strings (with type Custom):
    • CLIENT_ID = How to get client id & secret »
    • CLIENT_SECRET = How to get client id & secret »
    • SUBSCRIPTION_ID = Azure AD > Subscriptions > Subscription ID
    • TENANT = Azure AD > Azure Active Directory > Properties > Directory ID
    • PFX_PASSWORD = Random password
    • AZURE_STORAGE_CONNECTION_STRING = Connection string to any storage for Let's Encrypt challenges
    • AZURE_STORAGE_CONTAINER = Container name in storage for Let's Encrypt challenges
• in Azure Function App create function from template: Timer trigger / Javascript (named: TimerTriggerJS1)
• copy wwwroot to Azure Function App wwwroot
• run npm install in wwwroot
• change parameters in file index.js for your App Service
• in your app add redirect from path /.well-known/acme-challenge/:key to https://«storage_name».blob.core.windows.net/«storage_container»/:key (example for: expressjs)
• run TimerTriggerJS1 function