zlacker

>>aendru+(OP)
This is a terrible implementation of domain verification. dns-01 and http-01 are more or less standardized at this point. Use them, and don't roll your own. Reference: https://letsencrypt.org/docs/challenge-types/.

>>paxys+x4
I don't get http-based verification in general. If you want to really prove someone owns a domain, make them change an authoritative DNS record. Everything else feels like it is begging for edge cases to crop up. Why should my social media or SSL certificate vendor care about my web servers?

>>bob102+S9
Both http and dns verification are stupid. Neither of them prove you own the domain.

http verification proves you temporarily control IP space relative to a viewer. dns verification proves you temporarily control name resolution relative to a viewer.

Both are trivially hacked, multiple ways. By the time someone finds out you did it (if they closely monitor CT logs, which nobody does) you've already had hours, days, weeks to run a MITM on any domain you want. The attack only has to work once, on any of 130+ CAs.

The solution is registrar-level proof. Cert request signed by the private key of the domain owner, sent to the registrar to verify, the registrar signs it if its true, it's sent to the CA who can see the registrar signed it. Now you know for a fact the domain owner asked for the cert. The only possible attack is to steal all three of the owner's private key, the registrar's private key, and a CA's private key.

I have been shouting about this for 10 years, none of the industry incumbents care. The internet is run by morons.

>>throwa+Ji
> ...dns verification proves you temporarily control name resolution relative to a viewer.

> Both are trivially hacked, multiple ways.

I'm genuinely curious how it is trivial to "control [authoritative] name resolution relative to a viewer".

>>mikea1+Nl
Find out what the CA uses for its DNS resolver. Attack it with cache poisoning, or BGP spoofing, or compromise the account controlling the target domain's nameserver records, or trick some other system into making a record you want.

The BGP attack requires knowledge of internet routing and the DNS attack requires knowledge of DNS server exploits, but either of them can be executed with very minimal network access that any consumer can get. Target the nameserver account admin with a phishing attack, account reset attack, lateral password bruteforce, etc.

You'd be surprised how incredibly stupid the admins of some of the largest computer networks are. It's really not hard to get access to some accounts. It should require more than just a username and password to hijack a domain, but usually it doesn't.

In any case, if all you want is a valid cert, you can do it a number of ways that nobody will notice. Again, this only has to work once, on any one of 130+ different organizations. Not all of them have stellar security.

And I'm not even talking about social engineering either the CA, Nameserver, or Registrar's support people, which I consider cheating because it's so much easier.