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Comment by mkesper | Hacker News Reader

Ssh hostkeys offer no solution for first connect to ephemeral hosts.

If hosts are configured with SSH certificates as part or their setup, you can definitely skip TOFU and determine trust on the first connection. That won't work for the "I need to connect to a random IP address" scenario, but any cloud server exposing SSH can be configured with a certificate signed by a company/personal SSH certificate authority.

You could configure something delightfully atrocious like https://github.com/mjg59/ssh_pki but I think for most use cases where you connect to loads of SSH servers, host keys and certificate authorities will work just fine. We can do with an ACME-like protocol for distributing these certificates, though.

Given how rare this is, using https seems like a great idea

Strict SSHFP can theoretically solve it [1], assuming it's used in the first place and has DNSSEC. I personally use it for all servers I manage purely because I like the additional security, but it not at all common and DNSSEC isn't all that perfect either.

[1] https://aye.sh/blog/sshfp-verification

It's crazy that SSHFP hasn't taken off, I don't think a single person on earth has ever verified a host key before attempting to connect, and deploying DNSSEC is trivial now that you can use ECC and ED25519.

* Deploying DNSSEC is obviously not trivial, as doing so has taken some of the largest companies on the Internet fully off the Internet for multiple hours, within the last year, so much so that it has become a running joke when companies have prolonged outages to suggest that DNSSEC is the culprit.

* There are still resolvers that can't handle Ed25519

* Being able to use Ed25519 was never the ops problem with getting DNSSEC rolled out!

* It's weird to assume that people would want to enroll their server integrity --- something that doesn't in any way depend on an Internet PKI designed to allow strangers to verify your identity, and that enlists de facto government support to make that use case work --- in a global PKI, especially when SSH already has a perfectly good certificate system that solves the same problem without any of the above liabilities.

What boggles my mind, and I mean this sincerely, not as snark, is that anybody in the entire world takes SSHFP seriously. Even if you stipulate that DNSSEC (and/or DANE) works, just arguendo, it's still a totally different use case than resolving SSH key continuity problems.

My favorite thing about normal ssh keys is the way it does not come with the obnoxious assumption that if I don’t rent my cert from some rent-seeker, it is super scary and invalid. And yet it gives me both identity verification and encryption. I get the reasons we got there for HTTPS due to how unsophisticated the least experienced users are, but I am glad this idea here won’t catch on in real life, because we don’t need any of this stuff for SSH — mainly because it already has these features.

TLS certificates are free. Unsigned certificates are super scary and invalid. SSH and TLS do not work with the same threat model; first-contacts with SSH servers are comparatively rare (if they aren't, you should be worried about your SSH threat model, too).

Certificates aren't "free." They cost time at minimum, and complexity (you're forced to add a bunch of tooling to renew them) to satisfy the arbitrary requirements based around the fact that somehow their bits get old. The "free" ones think they get old in 90 days, and Apple decided for the whole world that I think one or two years is the absolute limit and anything longer-lasting is also "invalid."

A cert signed by your own CA isn't scary. You can trust and install your own CA, and unless you're an idiot and publish your private key you're not harming your security profile one bit, but like I said, I understand how we got here because if it were easy and not presented as scary, naive users would be tricked into installing new CAs every day. It's just annoying how it has (in practice) imposed this external prerequisite to use TLS encryption itself, which I think is pretty obviously the reason it took like 15 years for SSL to become ubiquitous.

SSh hosts have supported certs for at least a decade.

You can set up your ephemeral hosts to come up with properly signed host keys.

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