[embedding-shape]

> Besides you'd leak the subdomain to (typically) unencrypted DNS when you do a lookup and maybe via SNI.

"Leak" is maybe a bit over-exaggerated, although if someone MitM'd you they definitely be able to see it. But "leak" makes it seem like it's broadcasted somehow, which obviously it isn't.

[8organicbits]

No man-in-the-middle is needed, DNS queries are often collected into large datasets which can be analyzed by threat hunters or attackers. Check out passive DNS https://www.spamhaus.com/resource-center/what-is-passive-dns...

You'd need to check the privacy policy of your DNS provider to know if they share the data with anyone else. I've commonly seen source IP address consider as PII, but not the content of the query. Cloudflare's DNS, for example, shares queries with APNIC for research purposes. https://developers.cloudflare.com/1.1.1.1/privacy/public-dns... Other providers share much more broadly.

[embedding-shape]

> No man-in-the-middle is needed [...] Check out passive DNS

How does one execute this "passive DNS" without quite literally being on the receiving end, or at least sitting in-between the sending and receiving end? You're quite literally describing what I'm saying, which makes it less of a "leak" and more like "others might collect your data, even your ISP", which I'd say would be accurate than "your DNS leaks".

[8organicbits]

There's a lot of online documentation about passive DNS. Here's one example

> Passive DNS is a historical database of how domains have resolved to IP addresses over time, collected from recursive DNS servers around the world. It has been an industry-standard tool for more than a decade.

> Spamhaus’ Passive DNS cluster handles more than 200 million DNS records per hour and stores hundreds of billions of records per month, providing you with access to a vast lake of threat intelligence data.

https://www.spamhaus.com/resource-center/what-is-passive-dns...

[embedding-shape]

> collected from recursive DNS servers around the world

Yes, of course, because those DNS servers are literally receiving the queries, eg "receiving the data".

Again, there is nothing "leaking" here, that's like saying you leak what HTTP path you're requesting to a server, when you're sending a HTTP request to that server. Of course, that's how the protocol works!

[8organicbits]

I think you are hung up on the word "leak".

Putting a secret subdomain in a DNS query shares it with the recursive resolver, who's privacy policy may permit them to share it with others. This is a common practice and attackers have access to the aggregated datasets. You are correct that third-party web servers or CDN could share your HTTP path, but I am not aware of any examples and most privacy policies should prohibit them from doing so. If your web server provider or CDN do this, change providers. DNS recursive resolvers are chosen client side, so you can't always choose which one handles the query. Even privacy-focused DNS recursive resolvers share anonymized query data. They remove the source IP address, since it's PII, but still "leak" the secret subdomain.

Any time you send secret data such that it travels to an attacker visible dataset it is vulnerable to attack. I call that a leak but we can use a different term.

[embedding-shape]

> I think you are hung up on the word "leak".

What gave you that idea? Maybe because my initial comment started with:

> "Leak" is maybe a bit over-exaggerated...

And continues with about why I think so?

I raised this sub-thread specifically because I got hung up on "leak", that's entire point of the conversation in my mind.

[NetMageSCW]

So nothing to do with your DNS queries at all? Why did you bring it up?