Https vs ssl pinning

Question

I would like to know how does a regular SSL protocol differ from SSL pining. By setting up https, we are able to encrypt the request using SSL. Man in middle attack will not be able to see the raw payload. I also know SSL pinning is another way to prevent man in middle attack. But my question is if a proxy will always see the encrypted data only under https protocol, why do we still need to bundle certificate at client side and have SSL pinning? What advantage can SSL pining give us ?

Answer 1

Certificate pinning means the client has the server's certificate "built-in" and doesn't use your computer's trusted store. This means that even if your IT dept installs their own root cert, it won't be used.

A particularly clever IT department could install their root cert on your computer, use a proxy like Charles to create fake site certs on the fly, and re-write your downloaded program on the fly, replacing the pinned cert, but most aren't sophisticated enough to do that final step.

And you could probably just download the software from home too, in which case the pinned cert will be okay, and IT would never see the content on the transmissions.