I want to protect a web app behind some other application. This application should only let users through after they authenticated. While this is a common use case for Web Application Firewalls it seems. I want the WAF to try out filling username and password and determine if those are valid by seeing if the web app redirects to the welcome page.
What kind of programs are able to do this? Is there a name or term for this strategy? Is there anything that would speak against this strategy?