They could pretend to be any domain, yes, but you asked about inspecting a TLS stream, and afaik, there’s no way to do that without the private key. Once the TLS handshake begins, there wouldn’t be a chance for a man in the middle, so that kind of attack would have to be done before the connection is established.
this only works, if the client doesn’t know the server yet or disregards an already known key (you know, like SSH or web browsers telling you the key has changed)
Surely they can do a man-in-the-middle attack and gemerate the required private keys and certs on the fly.
They could pretend to be any domain, yes, but you asked about inspecting a TLS stream, and afaik, there’s no way to do that without the private key. Once the TLS handshake begins, there wouldn’t be a chance for a man in the middle, so that kind of attack would have to be done before the connection is established.
this only works, if the client doesn’t know the server yet or disregards an already known key (you know, like SSH or web browsers telling you the key has changed)
I don’t think that browsers do that. There is HSTS but I think that it only checks if the connection is using TLS.