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PSA: Test Your Server SSH Access (lemmy.ml)

submitted 2 months ago* (last edited 2 months ago) by brownmustardminion@lemmy.ml to c/selfhost@lemmy.ml

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I accidentally attempted to SSH into one of my servers from a device that did not contain my ssh key. I configure all of my servers to only allow authentication via cryptographic keys. Root ssh as well as password auth are disabled.

To my surprise, I was able to log in to my server with a password despite this. Baffled, I first tried some other servers. 2 of the 5 other servers I tried were accessabke via password.

After some swift investigation the culprit was found, a cloud-init ssh config in sshd_config.d/ with one line: password_authentication Yes.

So TLDR PSA....if you run a server in any type of virtualized environment, including a VPS, check your /etc/ssh/sshd_config.d/ folder. And more broadly, actually thoroughly test your ssh access to confirm everything is working as you intend it to.

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[-] friend_of_satan@lemmy.world 43 points 2 months ago

Show your effective sshd server config: sudo sshd -T

[-] MNByChoice@midwest.social 11 points 2 months ago

Good advice. One should always test, for correctness, not just infer.

[-] pe1uca@lemmy.pe1uca.dev 8 points 2 months ago

I could even go further into saying: always test every change you make, do not assume the change has been made because you updated a file.

[-] American_Jesus@lemm.ee 5 points 2 months ago

OpenSSH right? What version?
No issues with Dropbear

[-] Boris_NotTooBadinoff@lemmy.world 4 points 2 months ago* (last edited 2 months ago)

Had a similar issue with tlp recently. I just happened to notice the laptop battery was at 100%, and said it was charging. I double and triple checked the config file, but the tlp-stat -b still showed the thresholds at 90%-100%.

Turns out tlp, at some point, started ignoring /etc/tlp.conf, and was pointing to /etc/default/tlp

[-] arrakark@10291998.xyz 1 points 1 month ago

Yeah that sounds pretty bad. Is there a quick way to disable ssh keys to test?

this post was submitted on 30 Sep 2024

134 points (100.0% liked)

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