Yeah, checking from multiple perspectives is a good idea, but still ultimately a band-aid over the top of a flawed system. A properly engineered solution would need to ultimately come down to cryptographic proof of domain ownership (whether through DNSSEC, or something similar). Even RPKI still seems a little too indirect for my tastes (it fixes BGP attacks but potentially leaves the door open to other forms of domain hijacking).

Maybe in practice this is good enough, but the security nerd inside me rebels at how sloppy the whole thing feels.

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tptacek 6 hours ago | parent [-]

A lot of practical security is, in effect, band-aids over flawed systems. But I think it's useful to remember that the WebPKI doesn't actually want arbitrary secure DNS; it wants proof of domain ownership. There are ways to deliver that without forklifting in an entire new non-transparent PKI, especially since literally the only thing it will be used for is proving domain ownership.

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Ajedi32 4 hours ago | parent [-]

I don't see how you can have actual "proof of domain ownership" without secure DNS, or some kind of similar PKI. Right now they don't check for proof of domain ownership at all, just whether you have temporary, de facto control of the DNS record or the network it points at. This usually works well enough, but won't do anything if a MITM attack occurs on the server side rather than the client side.

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tptacek 2 hours ago | parent [-]

There's a whole design space of options here, one of the simpler ones being just checking via the registrar, using a protocol like RDAP. You could also use the DNS for this, but not require the entire zone to be encrypted (you'd be designing a new protocol, but that's what we have to do anyways, since DNSSEC is a dead letter).

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Ajedi32 2 hours ago | parent [-]

Yes. That would fall under the "some kind of similar PKI" category I mentioned, as you'd still need some kind of PKI to secure the RDAP connection. (Perhaps that PKI could be simpler than full DNSSEC, but it would have to solve a lot of the same problems.)

	▲	tptacek 2 hours ago \| parent [-]
		For RDAP to work (for instance) you only need to bootstrap with secure connectivity to the registrars. Current DV challenges have a much harder problem: they have to work with every zone on the Internet. There's no real reason to accept that constraint! When we think about "sound engineering" this is the level we need to start at, not "what features could we bolt on to core Internet infrastructure to define the problem away". The people most avidly pushing DNSSEC for this problem aren't stupid. They're just smuggling in an additional premise: that the WebPKI itself is bad, and should be replaced with a DNS PKI. Seen through that lens, secure proof of domain ownership would be deeply problematic, as it would leave the DNS PKI with literally no reason to exist.