[superuser2]

Any CA performing domain ownership validation would be vulnerable to the same thing. If you can fake its WHOIS requests or make it appear as if the domain making the request does in fact have the "canary" file they told you to host to prove ownership, then you can get any CA to give you a cert for any site.

You have to trust something.

[0x0]

If the registrar held the job of being a CA, then at least there wouldn't be a spoofable link between the CA and the domain owner - the registrar already has your account information and proof of ownership, 100% verified, when your domain is held with them...

[nailer]

Sure, but registrars would need to start doing a lot better job of checking the identity of people applying for domains, otherwise we'd just end up with domain validated certificates all over again.

As the grandparent post notes, all CAs completely automate domian validation at present.

[0x0]

My point is that regular domain validated CA should be the sole job of registrars. It would even prevent parallel certs being fraudulently issued - a domain can only be registered at one registrar at one time.

Sure, you could have the other CAs still offer EV (real-world identity) validation as a value-add.

But it's pretty silly that, currently, you have to pay a third party (today's CAs) to validate something that the registrar already knows for sure.

[kej]

The other side of that argument is that if your registrar is also your CA, they have the ability to give bogus SSL certs to an evil server and the ability to direct your domain to that evil server.

[0x0]

They can already do that, as they could temporarily hijack your NS records and buy a cert somewhere else. If you can't trust your registrar, you have bigger problems (I'd say "all is lost")

On the flipside, having a registar act as the only valid CA would mean that choosing a trustworthy registrar suddenly has real value. Power users could make an educated opinion on the trustworthyness of a given domain validated CA. Domain owners could be sure they're not at risk for how in the current system, an adversarity could get a valid parallel SSL certificate from a sloppy bargain-bin CA, even if the domain owner picked the most expensive and diligent CA and registrar for themselves.

[schoen]

A lot of folks might not have thought through the weakest-link aspect of the current system: they feel like they're safer because they chose to use a reputable or trustworthy CA. But misissuance events that I've heard of have never involved CAs that the victims had any business relationship with at all.

[RyanZAG]

Agreed - but by making this a fully automated system you open up an easily testable and repeatable source of attack.

I don't think "You have to trust something" is really right in this case, as you're basically saying "You have to trust every single router between letsencrypt and every server on the internet".

I guess it's correct that with most current CAs now automating a lot of this with minimal manual checks, this is probably happening already? I wonder how many amazon.com valid certs are floating around the place? (Or more likely, smaller sites where people wouldn't be checking if the cert is really valid). The original point behind the costs charged by Thawte et al was that they would actually validate that you're who you say you are. I guess that ship has sailed though.

[superuser2]

All mainstream CAs issue certs through a fully automated process, and have for at least a decade. Generally you are required to receive emails sent to the administrative contact in WHOIS, put something in a DNS TXT record, place or file they give you at a URL they give you, or some combination of the above.

There are Extended Validation (EV) certs where a human verifies your ownership of a legal entity. Chrome presents these as a big green bar with the name of the corporation in the URL bar. Most certs (including Amazon's) are not EV certs.