Comment by amiga386 | Hacker News Reader

Comment by amiga386 | Hacker News Reader

This is how I understand the exploit, can someone please confirm if I have the right idea?

1. I register a domain name -- example.com -- with a registrar like NameCheap. They tell Network Solutions (the .com registry) to add records on my behalf like below, which means the rest of the internet asks NameCheap's nameservers when they want to look up my domain.

    example.com. 172800 IN NS ns1.namecheaphosting.com
    example.com. 172800 IN NS ns2.namecheaphosting.com

2. For no reason, I ask NameCheap to change those NS records to another company's nameservers, such as Hurricane Electric, which I am NOT a customer of

    example.com. 172800 IN NS ns1.he.net
    example.com. 172800 IN NS ns2.he.net

3. Hurricane Electric (HE) are "exploitable"; one of their customers claims to be tranferring a domain to HE, example.com (my domain!), HE doesn't verify the actual ownership and they let it happen.

4. Now this HE customer has control over my domain... because I told my registrar to change the NS records to HE's nameservers. Why would I ever do that?

My understanding is this should never happen, I have no reason why I'd want to make such a change. ICANN have a policy on domain transfer between registrars: https://www.icann.org/resources/pages/transfer-policy-2016-0... -- and transferring a domain should only be done with the gaining registrar (HE in my example) putting an explicit request to the losing registar (NameCheap in my example), and the losing registrar getting to decide yes or no to the transfer.

So... how are there a million or more domains at risk this way? Is it old practises that haven't been corrected? How would this work?

This is kinda how it works, but not how it would work in practice.

The issue would be more like:

1. Register your domain with namecheap, and you want to have digital ocean run your DNS, so you point the domain to use their name servers.

2. A few months later, you decide to stop using digital ocean DNS, so you delete all your records… but you forget to change your NS record at namecheap, so now someone else can now add that DNS name to their digital ocean account.

This would only happen if your aren’t actively using the DNS name, which would allow you to have it point to a NS you aren’t controlling.

But the easy fix is just to change the NS records back to something you control. Somehow I don’t understand the problem.

It's easy to fix if you own the domain, but it still happens. The idea is to find ways to address the problem with the DNS providers so that it doesn't happen at all.

The point is some people will forget.

It is not a huge security hole, but just something that will cause issues for some people.

Gitlab also had same issue few weeks ago. Gitlab, once static pages are published, gives you a URL with gitlab.io ending. You can use your custom domain or subdomain by pointing CNAME or A record to Gitlab.

What users would do is, add DNS records to their DNS Manager to point their custom domain to Gitlab Pages, later will delete the Gitlab pages when not wanted any more. Scammer will simply point that same domain to his fake repository, thus hijacking customer domain.

Gitlab then made customer add a Txt Record for verification of domain. Scammer's txt record value is different from customer txt record, scammer can't modify DNS records.

Is there a similar mitigation that would work when you're using the 3rd party nameservers (a la Cloudflare), and not just a CNAME?

From what I understand the issue is more that people point domain to a DNS service, use it for a while and then remove their account (/domain from the account). Now someone else can add it to their account.

This is unlikely to be an issue on their primary domain but could be for e.g. subdomains or some marketing domains that aren't really in use anymore. Or cases where domain is just be squatted.

Namecheap is not a losing registrar, HE is not a gaining registrar, and the transaction you describe with Namecheap requesting that they update your registration's nameservers to HE's is not a domain transfer. You're conflating registration with nameserver assignment.

I'm not trying to conflate it, but I'm trying to imagine why you would ever switch your domain's NS entries away from your current registrar's nameservers, and the only reason I can think of is that you'd want a registrar transfer -- which should and I think does have more ownership checks around it.

However, other posters have given a more plausible example: you have server hosting with someone who isn't also a registrar, so for simplified management, you get your registrar to point your domain's nameserver at the server hosting company's nameservers, delegating it all to them... now you just need one customer portal to update all your hosting and DNS entries... and then you leave the hosting company (maybe the bill's too much), and you also forget to clean up the NS records, pointing them back to the real registrar's nameservers, so they're still pointing at this server hosting company you're no longer a customer of.

The hosting company isn't a registrar and is under no obligation to follow ICANN policies, so they can give the domain to some other customer of theirs without doing any verification. (I'm not sure they can do domain ownership validation, if they're not a registrar themselves)

I personally keep my domain registrations and zone files separate as a matter of security policy. I place as much importance on vetting reputable DNS providers as I do registrars. Nameserver assignment remains with the ICANN-accredited registrar.

(I would also never maintain a registration nor a zone file with a web/cloud hosting service.)

I've often run my registrars separate from my nameservers. Maybe I'm self hosting my nameservers. Maybe the nameservers are tied to the rest of my hosting (for ease of dynamic hosting) but want the ability to rapidly migrate if the hosting provider goes down. If the registrar is my nameserver host, good luck changing the SOA and NS records when SHTF at your host.

> why you would ever switch your domain's NS entries away from your current registrar's nameservers,

I want my domains at dynadot or namecheap or hexonet, but want CloudFlare to manage all DNS. CF doesn't support al ccTLDs.

> so they can give the domain to some other customer of theirs without doing any verification

Hosting company can not "give" the domain to anybody. If domain is still pointing to Hosting with NS records, anybody could make an account at Hosting, and add that domain. Now that scammer controls whats visible at Domain, but he is not yet the owner of domain.

Owner is who control and can change NS records. Scammer can change all other records, but not NS. NS is at original domain registrar. Original owner can very easily change the NS and cut the scammer out of everything (& should).

Gitlab used to be like this. You add a domain to Gitlab. You add an A record to your domain registrar or NS Manager. Now your domain shows your Gitlab Page. After few months, you don't want the pages anymore. You delete the project from Gitlab. You ignore to delete the A Record. Scammer adds that domain to his Gitlab, and shows his content at your domain.

Now Gitlab asks you to add a verification TXT record when adding any domain. Scammer's veri record is different. He can't prove that he owns the domain.

> Hosting company can not "give" the domain to anybody.

> Gitlab used to be like this

That's what I'm saying. Hosters can "give" a domain (i.e. control of that domain's records on their nameserver only) to someone else, because they're not registrars and aren't _required_ by some painful business contract with ICANN to have to take change of ownership seriously.

They should require a domain validation challenge to add a new domain, like your Gitlab example, but it doesn't seem like anyone can make them.

So therefore the onus is currently on the domain owner not to leave their domains' NS records pointing at nameservers they don't control!

> the onus is currently on the domain owner not to leave their domains' NS records pointing at nameservers they don't control!

That's exactly right. That is how this "attack" happens. Bad actor exploits registrant's abandoned yet still authoritative third-party nameservers assignment.

Discussion elsewhere in this thread[1] of how some of that responsibility/risk could be spread/shifted onto the DNS provider.

[1] https://news.ycombinator.com/item?id=41126976

Hosting can't make the challenge. Only way to prove is to make a TXT or cname record. Anybody where tha NS is pointing to, can make any DNS records.

Its like you put a lock (NS) on your box (Domain). After few months you don't care about that box anymore and leave that key in the wild. Anybody can pick that key and use the box. The box holder (domain registrar) can't make you verify that you are the original owner 'by' asking you to open the box, because by default, anybody who has key, can open the box. The correct way & responsible way is to destroy the box (delete the domain) or at least destroy the key (unpoint the third party NS records).

Reply on news.ycombinator.com