> for HTTPS, they usually can only support transparent byte relaying anyway.
On my LAN I run Squid on a Raspberry Pi, and have my personal laptop configured to use that as a HTTP and HTTPS proxy.
All TLS HTTP connections going through the Squid proxy are intercepted.
This only requires that my laptop trusts a self-signed TLS certificate that Squid uses.
Someone could easily run the same kind of thing on the internet, providing free proxy service and telling their users to trust a certificate signed by them, without properly explaining the consequences of that. And a lot of novice users would likely use that proxy service. Gleefully unaware that even the “encrypted” traffic is completely visible to the proxy.
In fact, I would be extremely surprised if there aren’t a whole gazillion of services out there doing exactly that.
But in many jurisdictions running a service like that would likely be cybercrime. And even if it wasn’t illegal, it’s still not nice. So, you know, don’t go and actually create a service like that.