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

submitted 3 months ago* (last edited 3 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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[-] henfredemars@infosec.pub 20 points 3 months ago* (last edited 3 months ago)

This is good advice in general. Think of it like penetration testing. You really should verify what you can actually access remotely on a device and not assume you have any level of protection until you’ve tried it.

Log files can also contain signs of attack like password guessing. You should review these on a regular basis.

this post was submitted on 30 Sep 2024

143 points (100.0% liked)

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