I was recently informed that a client I work with considers that a legal risk.
If the SSH connection is set to disallow passwords and only authorize via SSH keys, how big of a risk is this?
Given its sensitivity, OpenSSH is incredibly battle-hardened and probably better than almost everything else you can run on an exposed port.
ELI5, please. I understand it for passwords laymen use, but why is my 128 random byte password less secure than a key?
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.
The only thing it helps with is log spam, but then why not just configure SSH to not log login failures?
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-...
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.
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.
SSH is a risk because you’re trusting the users and client to not be idiots or get compromised. In general, people tend to do stupid things. If it’s just you and your server, potentially a different story.
It’s like sharing secrets with people, the more who are involved, the less likely the secret will be kept.
What's their alternative? I guess you could install frontpage extensions to manage content, but Microsoft's contractor for FrontPage extensions on unix and similar took the downloads down[1], so that's a lot of work. :P
Treat it as a teaching moment for them
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.
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?
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:
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.
Or how large companies actually think about this risk in the real world. Expose SSH ports to the public internet willy-nilly and count the seconds until their ops and security teams come knocking wondering what the heck. YMMV of course, but that's generally how it goes.
Are critical SSH vulns few and far between, as far as anyone knows? Yes.
Do large companies want to protect against APT-style threats with nation-state level resources? Yep.
Does seeing hundreds if not thousands of failed login attempts a day directly on their infrastructure maybe worry some people, for that reason? Yup.
You call it consultant distraction speak, I call it educating you about what Wireguard actually is, because in your original reply you suggested it was password-based.
>Further, they serve two different purposes so its comparing Apples to oranges in the first place.
Not when both can be used to protect authentication flows.
One is chatty and handshakes with unauthenticated requests, also yielding a server version number. The other simply doesn't reply and stays silent.
>Simple software can have plenty vulns, and complex software can be well tested.
In this case, both are among some of the most highly audited pieces of software on the planet.
The same with this last reply; you can keep throwing out new points all you want, but thats not going to make you correct in the original question.
Saying or implying that one software has a “principle” risk of vulnerabilities that another software doesn’t is plain and simply wrong.
And that has nothing to do with all the other stuff about layered defence, vpns, enterprise security, chatty protocols or whatever you want to pile on the discusion.
>So what’s the difference in risk of ssh software vulns and other software vulns?
I proceeded to explain how large companies think about the issue and what their rationale is for not exposing SSH endpoints to the public internet. On the technical side, I compared SSH to WireGuard.
For that comparison, the chattiness of their respective protocols was directly relevant.
Likewise complexity: between two highly-audited pieces of software, the silent one that's vastly simpler tends to win from a security perspective.
All of those points seem highly relevant to your question.
>... but thats not going to make you correct in the original question.
If you can elucidate what I said that was incorrect, I'm all ears.
Edit: codebase of ssh/wireguard implementations, just to be clear
WireGuard is 4k LoC and is very intentional about its choice of using a single, static crypto implementation to drastically reduce its complexity. Technically speaking, it has a lower attack surface for that reason.
That said, I've been on your side of the argument before, and practically speaking you can expose OpenSSH on the public internet with a proper key setup and almost certainly nothing will happen because it's a highly-audited, proven piece of software. Even though it's technically very complex.
But, that still doesn't mean it isn't best practice to avoid exposing it to the public internet. Especially when you can put things in front of it (such as WireGuard) that have a much lower technical complexity, and thus a reduced attack surface.
Wireguard is a protocol. So what implementation is “very intentional about its choice of …”? Are you talking about my own WG client implementation? Or the one made by this other Chinese vendor?
I don’t care what software we are talking about, or who made it. All software has a risk of undiscovered/-disclosed vulnerabilities already existing, or when new ones introduced with an update.
If you really want to make this argument we can talk about the implementing organisations SDLC, including SW supply chain, and compare those.
But back to the OP/point above: its false to state that one piece of software has a “principle risk” of vulnerabilities that another piece does not. At least, not when both are internet exposed and accepting incoming data.
Lasty remember that I never disagreed with you point that a VPN solution is often a better solution, but that was never what I was arguing about. Simply that all code always has a risk of vulnerabilities. No piece of software is excempt from that.
So according to you, the concept of attack surface doesn't exist. A 100MB binary is equivalent in risk to a 1KB binary. Got it.
If both are highly-audited, their risk is equal despite their size and protocol complexity. Got it.
>...its false to state that one piece of software has a “principle risk” of vulnerabilities that another piece does not.
That's like the third or fourth time you've scare-quoted the word principle. You're aware that principle and principal are two different words with different meanings?
The word I used, principal, in that context means the foremost or primary risk.
Anyways, I'm just telling you how major corporations think about it. Their underlying rationale is exactly what I've explained thus far, and hence why it's best practice.
Keep shooting the messenger I guess.
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.
But yeah putting it behind some kind of VPN is advisable if anything because of all the driveby nuisance attacks on ipv4.