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Sign arbitrary data with your SSH keys

(www.agwa.name)
637 points h1x | 1 comments | 13 Nov 21 09:13 UTC | HN request time: 0.244s | source
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pizza ◴[13 Nov 21 10:03 UTC] No.29208734[source]▶
I get that they're "public" keys, but I was surprised to learn (and from somebody other than github themselves) that ssh public keys are just available at that github.com/username.keys URL (without there being an option to disable it, it seems?). Did most people already know that? Probably fine but just surprised. Just tried searching their authentication docs [0] and I don't get any results for "public key url" either

https://docs.github.com/en/authentication?query=public+key+u...

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diggan ◴[13 Nov 21 10:39 UTC] No.29208877[source]▶
I don't think it's super well known, but it is very handy. Used it in the past to give people SSH access by just asking for GitHub user, and then basically just doing `curl https://github.com/victorb.keys >> ~/.ssh/authorized_keys` without sending keys back/forward.

Keybase (or similar) would ideally be used for this instead, but they chose to go a very weird route for their tool, and are now disappearing completely eventually probably.

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Hendrikto ◴[13 Nov 21 10:57 UTC] No.29208947[source]▶
Shouldn‘t you be using different keys for different services though? What you are doing sounds like bad practice.
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1. snorremd ◴[13 Nov 21 11:41 UTC] No.29209133[source]▶
I don't think using different keys per service or host buys you much in terms of security. Yes, an attacker that compromised your keys would have to brute-force your passphrase for N keys rather than one private key, but that just takes N times as long, not really an obstacle.

It would be better to use a hardware authenticator like a Yubikey to either generate a FIDO token-backed SSH key or a GPG key and use the gpg agent as your ssh agent. This way you get SSH keys that cannot reasonably be compromised by other means than physical attacks (someone steals your key and coerces you to reveal pin code).