As I understand it, the MITM attack is relying on the lack of authentication rather than lack of confidentiality. The attacker can go to LE and get a challenge file (AIUI), which they host on a fake version of the website. They then use DNS spoofing/cache poisoning/ARP spoofing/whatever to get the CA to hit their spoof website rather than the real one. This “proves” the attacker owns that domain and so they can then carry out the rest of the steps to get a cert.
IMO its much harder to carry out this MITM against a CA compared to typical MITM attacks against end users. CAs generally speaking aren’t connecting to random wifi hotspots or using random ISPs etc. So you’d need to be in a pretty privileged network position to carry this out. And the multi-endpoint resolution approach seems like it would make it very hard indeed to pull off.
That said, it seems a bit of a shame not to use the existing cert where one exists (which is presumably the case for most requests, which I’d expect are renewals).
IMO its much harder to carry out this MITM against a CA compared to typical MITM attacks against end users. CAs generally speaking aren’t connecting to random wifi hotspots or using random ISPs etc. So you’d need to be in a pretty privileged network position to carry this out. And the multi-endpoint resolution approach seems like it would make it very hard indeed to pull off.
That said, it seems a bit of a shame not to use the existing cert where one exists (which is presumably the case for most requests, which I’d expect are renewals).