A network I often use has started to decrypt HTTPS traffic (and reencrypt, using a different key) using a local proxy. This proxy is operated by people I mostly trust. However, I would like to know if there is a way to maintain encryption and MAC through said proxy, with something like Tor or a VPN. Bonus points for ease of use.
I would also like to ensure that there is not a second MITM, between the local proxy and internet server, if I am not using the above methods, for example, if they are blocked somehow. If there is another MITM present, I'd like some form of warning, similar to the one a browser gives when using an untrusted certificate.