5 ms·

> a compromised root ca allows an attacker who already has dns or ip control DNS or host/IP control is not a requirement at all: a Trusted CA is already truste

> a compromised root ca allows an attacker who already has dns or ip control DNS or host/IP control is not a requirement at all: a Trusted CA is already trusted to sign a certificate for any hostname (with exceptions): that's what Trust means, and it also means that we trust them not to issue certificates for domains/hostnames without doing at-least Domain Validation - and we have schemes like Certificate Transparency to help bolster that trust, but it still doesn't prevent an already-trusted CA from issuing its own certificate for, say, google.com or microsoft.com. This is why techniques like Certificate Pinning and co/counter-signing, and others exist - but they're only useful when the client isn't a human-operated web-browser ("smart clients", "IoT", etc). EV certificates were (amongst other things...) meant to help protect against small-time crooks but again, don't help when the CA itself is compromised.

kragen 4y ago
if i type https://gmail.com/ https://gmail.com/ into my browser, it usually doesn't matter if you have successfully gotten comodo or actalis to issue you a fake certificate for gmail.com, because my browser doesn't try to connect to your malicious server; it tries to connect to google's actual gmail server, and so you don't receive my packets, and your fake certificate does you no good but, as i said, if you can feed me fake dns results so i connect to the wrong ip, or if you can arrange so that packets to gmail's legitimate ip go to your server instead (for example by having me connect to your wifi), then you can leverage the fake certificate into a successful mitm attack but your explanation of the part of the basics of tls you understand, incomplete though it is, is irrelevant to the attack i was actually discussing, where someone doesn't like what you're saying (or the communication service you're providing) and gets your cert revoked to shut you up
- b112 4y ago
  because my browser doesn't try to connect to your malicious server Unless a router is compromised along the route, which is a known thing, and part of why we use ssl everywhere now.
  - kragen 4y ago
    the paragraph immediately following the one you quoted from explains that, and did so nine hours before your comment the grandparent comment https://news.ycombinator.com/item?id=34629050 https://news.ycombinator.com/item?id=34629050 also describes some more common ways that this can happen without routers being compromised
    - b112 4y ago
      Noted.
lol768 4y ago
If the browser enforced that the certificate had been issued in line with the domain's CAA record, such an attack might be less tractable without DNS control...

kragen 4y ago

if i type https://gmail.com/ https://gmail.com/ into my browser, it usually doesn't matter if you have successfully gotten comodo or actalis to issue you a fake certificate for gmail.com, because my browser doesn't try to connect to your malicious server; it tries to connect to google's actual gmail server, and so you don't receive my packets, and your fake certificate does you no good but, as i said, if you can feed me fake dns results so i connect to the wrong ip, or if you can arrange so that packets to gmail's legitimate ip go to your server instead (for example by having me connect to your wifi), then you can leverage the fake certificate into a successful mitm attack but your explanation of the part of the basics of tls you understand, incomplete though it is, is irrelevant to the attack i was actually discussing, where someone doesn't like what you're saying (or the communication service you're providing) and gets your cert revoked to shut you up

b112 4y ago
because my browser doesn't try to connect to your malicious server Unless a router is compromised along the route, which is a known thing, and part of why we use ssl everywhere now.
- kragen 4y ago
  the paragraph immediately following the one you quoted from explains that, and did so nine hours before your comment the grandparent comment https://news.ycombinator.com/item?id=34629050 https://news.ycombinator.com/item?id=34629050 also describes some more common ways that this can happen without routers being compromised
  - b112 4y ago
    Noted.

lol768 4y ago

If the browser enforced that the certificate had been issued in line with the domain's CAA record, such an attack might be less tractable without DNS control...