This article shows how to implement certificate authentication to secure downstream APIs using Microsoft YARP reverse proxy in an ASP.NET Core app that uses Angular for UI.
Along with securing the Angular UI and ASP.NET Core backend, the API is protected with certificate authentication and deployed on Azure App Service.
The YARP reverse proxy is added in the ASP.NET Core application's startup and the appsettings.json file.
The ReverseProxy settings add the configuration defined in the app settings.
The downstream API uses certificate authentication to protect it and requires a certificate forwarding middleware in local development but not on Azure App Service.
The article also includes the setup process that shows the app working with increased security using a certificate rather than just a token.
This approach increases security and makes it simple to implement a secure app-to-app security.
Securing the downstream APIs with cookies may still be the weakest link if not secured correctly.
Links to related resources used while making the app are provided in the article.