This is useful if you want to just play around with it, but if you actually want to (legally of course) get info and still have it remain on the same page and a signed SSL Certificate you would have to work as a proxy server that can intercept requests. A good introduction to this is with
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(Universal, Java) where you can modify, intercept, and repeat requests from within one place. With this tutorial it shows that you have physical access to the network, and if you have that you have total access anyways.
All you need to do is set your server as the proxy server and install the SSL certificate.
(Since I'm referencing an outside executable even though it's well known: VirusTotal
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)