I am going through CISSP materials and I got stuck on Secure Exchange Protocols such as Diffie Hellman and RSA. It is known that DH by itself is vulnerable to MiTM. So the answer is to use authentication methods such as certificates. That's fair and square because that's what https is based on. But how does that make it MiTM proof if we have things like SSL inspection? SSL inspect is by nature a MiTM attack designed to intercept encrypted traffic by injecting its own certificate and looking like the CA for the destination's certificate. Most modern AV solutions today do the same thing. If you check certificates of the https websites you go to, they will be signed by your AV vendor.
These are the sources I have used
The RSA article says "Even though Carol is still able to intercept messages between Alice and Bob, she cannot forge signatures without Alice's private key and Bob's private key."
My question is, why would she need to do that? If she is intercepting their data, she can simply use a certificate signed by her and pretend to be either party. She can use her own private key for signing and decryption because she already provided both parties with her own public key. Then re-encrypt the data with the destination's public key and pass it on. Isn't that exactly how SSL intercept works?
The only way around this I can think of is that her CA used to sign the fake certificate would not be in the trusted certificate root stores of the victims. But when I think back to all the L2L VPNs I have created using Diffie Hellman, neither of those things (certificates or cert root stores) were used.
I must be missing something here.