And how do you know you're actually encrypting against google.com's public key, and not somebody else's key?
A VPN provider is in the perfect position to MITM all of your traffic, swapping out any site's public keys with their own in real time. If your VPN app has installed an alternative Root CA on your device, you'll get no warning that this has happened.
My understanding was that for Chrome that the CA had to be in the Chrome root store. And that this is what is used over the OS level root store where the VPN providers would be installing theirs. Doesn't Mozilla also ship with its own preferred root store as well?
"If you’re an enterprise managing trusted CAs for your organization, including locally installed enterprise CAs, the policies described in this document do not apply to your CA. No changes are currently planned for how enterprise administrators manage those CAs within Chrome. CAs that have been installed by the device owner or administrator into the operating system trust store are expected to continue to work as they do today."
In other words, locally installed certificates are normally treated as trusted by Chrome.
Thanks. I completely misunderstood that. That makes total sense for an enterprise use case too otherwise it would probably be non-starter for many corporate IT departments.
A VPN provider is in the perfect position to MITM all of your traffic, swapping out any site's public keys with their own in real time. If your VPN app has installed an alternative Root CA on your device, you'll get no warning that this has happened.