Ask HN: Is Connecting via SSH Risky?

12 comments

• bigstrat2003 18 hours ago
  SSH is not at all risky if you disable password authentication. There's essentially zero chance that someone guesses your private key, though you might get annoyed with all the login failures spamming your logs. Fail2ban helps with that if you care, though I don't personally bother these days.
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  • null_deref 12 hours ago
    So that’s generally my train of thought, but from what I know there were serious vulnerabilities discovered in OpenSSH throughout the years, doesn’t it increase the risk for open ssh port or were the vulnerabilities discovered never touched those areas of ssh authentication. Seems to me that tools like tailscale and so on aren’t open to this sort of risk but I definitely can be wrong
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    • lxgr 11 hours ago
      The only one I can think of is the one on Debian where key generation used weak entropy, making keys guessable.

      Given its sensitivity, OpenSSH is incredibly battle-hardened and probably better than almost everything else you can run on an exposed port.
• tim-tday 20 hours ago
  They probably mean leaving ssh open to all ips. Take a look at your auth failure logs to see the thousands of daily attempts to compromise your server using default passwords. Most of those are low effort and low risk. Sometimes the bots will try password stuffing. Disabling password auth in sshd config is good practice. Fail2ban also helps block repeated attempts like that.

  There’s also the risk of a zero day RCE vulnerability in ssh (though I’ve not seen one in the 20 years I’ve been paying attention )

  I tend to not expose ssh to the world and log in with some other method to pass the perimeter (VPN, IP whitelist, tailscale) and the ssh from inside.

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  • lxgr 11 hours ago
    fail2ban seems like security theater for a keys-only SSH server, and it won't help against zero days either (unless it happens to be one that requires many attempts).

    The only thing it helps with is log spam, but then why not just configure SSH to not log login failures?
• kasey_junk 14 hours ago
  You said “legal” risk, not “security” risk. You’ll need to get more information on what risks they are trying to mitigate and talk to a “legal” expert rather than engaging on a technical or security basis.
• _Chief 15 hours ago
  > If the SSH connection is set to disallow passwords and only authorize via SSH keys, how big of a risk is this

  low risk, do this. Keys (ed25519,4096 rsa) are impractical to brute force. However I'd also recommend:

  - use a different port than 22 (add your .ssh/config for easier UX if needed) - port 22 can get incredibly noisy with tons of bots probing

  - disable passwordAuth, disable PermitRootLogin - use a normal user with sudo for your ssh

  - consider a vpn please - I use tailscale, but I hear headscale is good - then use UFW to only allow SSH from the tailscale network (I generally allow all network on tailscale). Tailscale wrote a guide on this here [1]

  - do not add and forget authorized_keys from machines you arent using

  - I'm especially worried about how people keep giving Clawdbot/Openclaw access to all their machines, key auth means the machine is authorized on your server

  - For new servers I often just add all my public keys to them (github lists all your keys at github.com/GH_USERNAME.keys

  1: https://tailscale.com/docs/how-to/secure-ubuntu-server-with-...

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  • atrevbot 10 hours ago
    Thanks a lot for the detailed response. I see Tailscale pop up here often and have been meaning to better understand how it could fit into my typical hosting setup, so I appreciate that reference.

    For additional context I usually host on a shared or dedicated VPS, and in this case am managing a WordPress site I inherited. It seems to me that if the SSH connection is restricted by IP and limited to keys, there are much larger risks involved in hosting a WordPress site publicly available on the internet w/ dozens of plugin dependencies.
  • lxgr 11 hours ago
    > key auth means the machine is authorized on your server

    Not necessarily: Depends on whether your key is passphrase-protected and how your SSH agent is configured (if you use one). You can have the standard OpenSSH one ask you for confirmation of every key usage, for example.

    > consider a vpn please

    But also consider how you'll fix a broken VPN without SSH access.
  • janmalec 15 hours ago
    Many people keep offering advice to consider a VPN and while VPN is very usefull, I have not yet come accross a reason why not use ssh auth. Like what can actually happen? From my pov the risk of running all sorts of userspace software with internet access is much greater, even without port forwarding.
• 1970-01-01 11 hours ago
  No, but if you do it badly of course it will be. How else do they expect you to login? Unless they are giving you physical access, SSH by all measures is the best way to connect. Leaving it unmaintained is the worst way forward. Just follow best practices and patch on a regular schedule. They seem to be worried about the wrong problem here. Where is your client's security team and why are they ignoring this issue? If they don't have one, then tell them to get one before complaining about something they know nothing about.
• electroly 11 hours ago
  If you're hosting on a public cloud, you can use a feature like AWS Session Manager to connect "through the backdoor" (via the guest's private communication with the hypervisor) without actually opening the ssh port to the world. This should fully address the client's concerns. None of my servers have ssh exposed at all.
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  • lxgr 11 hours ago
    How does the nature of remote access address the legal concern (presumably) about there being remote access in general?
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    • electroly 11 hours ago
      That isn't my presumption about nature of the concern. In OP's other comment they specify that the client is specifically worried about the open port.
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      • lxgr 11 hours ago
        Well, if you allow remote access, you conceptually allow some kind of logical inbound connection, no matter how it's technically realized.
• verdverm 20 hours ago
  Runs counter to my understanding, I'd ask for clarification and find support material to show your approach is safer.

  Treat it as a teaching moment for them
• rl3 20 hours ago
  Best practices usually call for not exposing the SSH endpoints to the public internet. The principal risk is vulnerabilities in the underlying SSH server implementation. Historically, critical flaws that can compromise you are few and far between. However, these days AI is already starting to become adept at reverse engineering.

  If you must, you'd typically use a bastion host that's configured just for the purpose of handing inbound SSH connections, and is locked down to a maximal degree. It then routes SSH traffic to your other machines internally.

  I'd argue that model is outdated though, and the prevailing preference is putting SSH behind the firewall on internal networks. Think Wireguard, Tailscale, service meshes, and so on.

  With AWS, restricting SSH ports via security groups to just your IP is simple and goes a long way.

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  • Msurrow 18 hours ago
    But doesn’t your argument that the principal risk [with ssh] is vulnerabilities also apply to the alternatives you say is best practice? Firewalling off ssh (but not http(s)) has the risk of vulns in the FW software. Tailscale, wireguard etc also has the risk of vulns in that software?

    So what’s the difference in risk of ssh software vulns and other software vulns?

    Also, another point of view is that vulnerabilities are not very high on the risk ladder. Weak passwords, password reuse etc are far greater risks. So, the alternatives to ssh you suggest are all reliant on passwords but ssh, in the case, is based on secure keys and no passwords. Should “best practices” not include this perpective?

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    • rl3 17 hours ago
      Good defense is layered.

      For vulnerabilities, complexity usually equals surface area. WireGuard was created with simplicity in mind.

      >So, the alternatives to ssh you suggest are all reliant on passwords but ssh, in the case, is based on secure keys and no passwords.

      WireGuard is key-based. I highly suggest reading its whitepaper:

      https://www.wireguard.com/papers/wireguard.pdf

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      • Msurrow 11 hours ago
        Sure, no one said it wasnt layered.

        But saying ssh is a risk “on principle” due to possible vulnerabilities, and then implying that if wireguard is used then that risk isnt there is wrong. Wireguard, and any other software, has the same vuln risk “on principle”.

        > For vulnerabilities, complexity usually equals surface area. WireGuard was created with simplicity in mind.

        That is such consultant distraction-speak. Simple software can have plenty vulns, and complex software can be well tested. Wireguard being “created with simplicity in mind” doesn’t not make it a better alternative to ssh, since it doesn’t mean ssh wasnt created with simplicity in mind.

        I don’t disagree that adding a vpn layer is an extra layer of security which can be good. But that does not make ssh bad and vpn good. Further, they serve two different purposes so its comparing Apples to oranges in the first place.
• speleolinux 20 hours ago
  If your private key has a good passphrase and is suitably encrypted, say with ed25519, then that's probably as good as you can do other than physically going into work and storing everything in your head :-) Politely ask the client to suggest what they consider would be a suitable alternative. I also setup git hooks to prevent accidentally checking in private keys or passwords into git or other version control systems. And if I'm travelling into or from work I also encrypt some stuff just in case I have a problem and the laptop is stolen.
• xhanah 20 hours ago
  ditto to everything here. If you really want to you can also change the port to something random to avoid bot spam. but you shouldn't have SSH accessible directly from the internet anyway.

  If you are using only keys, make sure they are managed, tracked, securely stored and backed up. The last thing you want is to have a machine die that has the only private key for your environment.
• phren0logy 21 hours ago
  Compared to what?
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  • atrevbot 21 hours ago
    They seem to be okay w/ only HTTP ports being open on the server (80, 443). They "found that open ports can lead to cyber claims".
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    • wolvoleo 18 hours ago
      "Cyber claims" sounds like someone who doesn't have a clue what they are talking about.

      But yeah putting it behind some kind of VPN is advisable if anything because of all the driveby nuisance attacks on ipv4.
    • bediger4000 20 hours ago
      That's like saying that open bottles lead to alcoholism.
  • DamonHD 21 hours ago
    Indeed.
• robertcope 20 hours ago
  How else would you do it?
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  • muppetman 19 hours ago
    Wireguard and Telnet ;)