4 ms·

Ok ye the CA system isn't great, but as far as I'm aware, letsencrypt do DNS queries from multiple POPs, so that the route would have to propagate extremely wid

Ok ye the CA system isn't great, but as far as I'm aware, letsencrypt do DNS queries from multiple POPs, so that the route would have to propagate extremely widely to convince them to issue a cert.

peterwwillis 8y ago
A representative of LE commented on HN recently that they do not verify from multiple POPs. But even if they did, that would not stop this attack. There are hundreds of CAs, and not all of them are going to verify from multiple POPs. You only need your attack to work on one CA for it to be effective against every client on the web. Even if all CAs verified from multiple POPs (not likely) the attacker will just increase their attack to advertise from multiple ISPs/POPs. The attack is virtually the same, the only thing you need is more network access, which is not hard to get.
- amaccuish 8y ago
  Thanks for that, I had no idea! I stand corrected :)
- tialaramex 8y ago
  There aren't really "hundreds" of CAs in a sense that matters here. Last time somebody insisted on this I actually counted, I forget the answer I got, but it's less than three figures. You can get a bigger number if your idea of "effective against every client on the web" is "It works in Internet Explorer". Microsoft is very... liberal in accepting new CAs controlled by corporate or sovereign entities. But if you expect "every client on the web" to include Chrome on Android phones, Safari on iPhones and Firefox everywhere, not just Internet Explorer, then you're talking about dozens, not hundreds, mostly because of the work done by Mozilla. And most of those CAs are fairly small. Forget a nice API you can just make an HTTP request to and get your certificate in seconds, some of them are going to expect you to wait until business hours and talk to them on the telephone.

4 ms·

Ok ye the CA system isn't great, but as far as I'm aware, letsencrypt do DNS queries from multiple POPs, so that the route would have to propagate extremely wid

by amaccuish 8y ago

Ok ye the CA system isn't great, but as far as I'm aware, letsencrypt do DNS queries from multiple POPs, so that the route would have to propagate extremely widely to convince them to issue a cert.

peterwwillis 8y ago
A representative of LE commented on HN recently that they do not verify from multiple POPs. But even if they did, that would not stop this attack. There are hundreds of CAs, and not all of them are going to verify from multiple POPs. You only need your attack to work on one CA for it to be effective against every client on the web. Even if all CAs verified from multiple POPs (not likely) the attacker will just increase their attack to advertise from multiple ISPs/POPs. The attack is virtually the same, the only thing you need is more network access, which is not hard to get.
- amaccuish 8y ago
  Thanks for that, I had no idea! I stand corrected :)
- tialaramex 8y ago
  There aren't really "hundreds" of CAs in a sense that matters here. Last time somebody insisted on this I actually counted, I forget the answer I got, but it's less than three figures. You can get a bigger number if your idea of "effective against every client on the web" is "It works in Internet Explorer". Microsoft is very... liberal in accepting new CAs controlled by corporate or sovereign entities. But if you expect "every client on the web" to include Chrome on Android phones, Safari on iPhones and Firefox everywhere, not just Internet Explorer, then you're talking about dozens, not hundreds, mostly because of the work done by Mozilla. And most of those CAs are fairly small. Forget a nice API you can just make an HTTP request to and get your certificate in seconds, some of them are going to expect you to wait until business hours and talk to them on the telephone.