i want to remotely ssh to my home server, and I was wondering if I could just forward port 22 with disabling password login and use pubkey authentication will be safe enough?
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disabling password login and use pubkey authentication will be safe enough?
Just make sure you actually disable password login. Simply enabling key doesn’t disable password. So as long as the password is disabled then you’re fine.
Disable password auth.
Enable key only auth.
Add in TOTP 2FA (google authenticator).
Randomize the port (reduce bots) that forwards to 22.
Configure lockout to block upon 3 failed attempts, for a long duration like 1 year. (Have a backup access on LAN).
Ensure only the highest encryption ciphers are accepted.
Ensure upgrades are applied to sshd at least monthly.
If you are going all out, may as well add hosts.deny and hosts.allow.
Easy to do with known internal networks.
Difficult to manage when roaming.
Absolutely, just sometimes people forget those tools even exist. Of course, you can easily do the same thing with firewall rules as well.
Also, that was a great tidbit about the pam email notification on successful logon. I haven’t seen that one before, thank you!!
Add port knocking, if we go all out, let’s go all out!
To help with identifying issues within your SSHd configuration, I recommend using ssh-audit: https://github.com/jtesta/ssh-audit
Good summaries. How does the TOTP 2FA article handle drop/reconnects? TOTP needed for each reconnect attempt?
Configure lockout to block upon 3 failed attempts
fail2ban
If you disable password authentication, and use public key authentication, yes.
As long as password auth is disabled you’re fine. No one is cracking your RSA key. You can add Fail2Ban to reduce the log noise, but security wise it’s fine.
Likely better behind a VPN. This was reported recently. https://thehackernews.com/2023/11/experts-uncover-passive-method-to.html?m=1
Dont connect it to the internet too. Chances are even less likely that some navy seals kinda guys will steal you data with brute force. Also always keep explosives next to your hdds so once they do come you can explode them.
Thats why I store thermite by my rack. Burns it all down.
Also don’t use rsa, use Ed25519 nowadays
RSA is fine. It isn’t like you will have to worry about the length of the keys for SSH.
It is but if you’re going to use something security related, use the current recommendation unless you stricly can’t for legacy reason or something.
Requires an actual hardware error. Almost all implementations, including all open source SSH implementations, check that the signature is valid thus preventing a cosmic ray induced bit flip from triggering this issue and any related issue.
What effect do hardware errors have on Ed25519?
Well it‘s true that one can use RSA, which is still save with keys big enough, but if someone wants so save some extra computing power and time ed25519 is the way to go.
The difference is extremely tiny because asymmetric encryption is only used at the very beginning to securely establish a symmetric key that will be used for everything else afterwards. So you would have to be running this on a smart fridge to notice the speed difference.
True enough
Change your port.
No one’s cracking a proper implementation of RSA, but not every implementation is proper. A little obscurity can’t hurt.
Just waiting for everyone to come in saying you shouldn’t do this lol. Yes, changing the port is a nice little bonus. It doesn’t any extra security, but it moves you out of the way from the automated bots that scan the internet trying recent 0days. You’ll probably see a reduction of 99% traffic hitting the service and the only logs will be real people.
only logs will be real people.
There are bots that scan for open ports in minutes.
Yes but most bots are scanning for common ports. It’s far too slow to scan 65k ports on every host. Even things like shodan only scan a handful of common ports. But you can test this yourself, expose SSH on a port number in 20-40ks, I’ve seen several weeks without a single probe.
If you’ve ever done mass scanning you know that’s minutes is not going to to be a full scan and if you are trying to do 65k ports in a few minutes, your results will not be accurate.
But then it’s blatantly obvious and you can behavior block.
Apparently, the downvoters don’t understand IPS.
Which is easily defeated by using one block of ip addresses to gather data and another block for actually trying to exploit found ports. Unless you block the whole AS. If the attacker only uses one system with one ip they probably wouldn’t have the resources to get past ssh anyway.
Behavior blocking can be done across many IPs.
If you have one IP that scans port 10000, the other port 10001, and thousands of other IPs scanning just 1 port it’s still blatantly obvious.
And if they want to scan in a less obvious manner they need to do this spaced by days.
Realistically no one is cracking my super long randomized password either. Seems fine to leave it on as backup login.
If you really want security you should also add UFW and restrict it to only your IP address.
Get fail2ban setup at a minimum
Better use some kind of VPN and only open the SSH port over the VPN interface.
I run this on port 22 and ssh with keys on a different port
No. Just VPN in and SSH in.
How is a VPN service more secure than an SSH service?
Both accept login.
Both provide can be brute forced / if using password.
Generally speaking. VPN is easier to setup securely out of the box for most especially with limited knowledge. You can choose a random port and then have access to any server on your network. Scanners won’t usually test all ports unless they find something that’s tempting.
Normally just the normal ports will be poked including 22. SSH can be secured well but not without jumping through a few hoops. It’s easier imho to accidentally allow access through incorrect ssh setup than vpn.
When you think vpn has been developed with this exact purpose in mind. It’s fair to assume the protection will be better out of the box. If you have a vpn then a hacker needs to get through the vpn and then also the ssh so there’s not really any disadvantage to using a vpn and then also harden ssh if you want to.
It’s about making things difficult. Nobody is going to spend days or weeks battering a vpn if they don’t think there’s anything useful behind it. A VPN also shows somewhat that you’ve given things consideration and are not an easy target.
Don’t get me wrong. If somebody is determined enough and has the resources then they will find a way but given the choice between an easy target and one that’s ever so slightly more difficult, they will almost always go for the easiest.
VPN is easier to setup securely out of the box for most especially with limited knowledge.
One of the top audit companies disagrees with you: https://blog.trailofbits.com/2016/12/12/meet-algo-the-vpn-that-works/
A “top” audit company pushing their own agenda.
OpenVPN is simple and easy to deploy on any major operating system. Pfsense or similar is easy to setup and run in a VM. That does all the hard work for you and creates a profile. Then you essentially copy or download that profile to the client machine and you’re done. It’s all done via gui or web interface so is easier for a lot of people. My sister managed it. She wouldn’t have been able to handle command line stuff.
Like i said before though. Why not use a vpn and also harden your ssh. I can’t see a downside to that.
It’s just my opinion and experience from working with both. You’re welcome to dissagree and do your own thing though of course :)
WireGuard uses UDP and will not respond if the attacker doesn’t have the correct key. So the port used by WG will appears as a closed port.
I think many ppl are missing a step here. Setup a VPN with wireguard or similar. Then in ur sshd configs only allow ssh from ur VPN local subnet. That on top of ssh key login is pretty secure. Unless one of ur other services gets compromised and they pivot to ur VPN network. Then u prob have more problems tbh
With PubKey and Fail2Ban its probably ok but wouldnt chance it personally. Can you use a different port too?
Yes and no.
Yes if you have the resources to monitor and update. Companies have entire teams dedicated to this.
No if you don’t have the resources/time to keep up with it regularly.
IMO, no need to take this risk when you have services like Tailscale available today.
Port knocking could be useful here
I would risk it. After all, it’s the only thing protecting my entire gitlab account. If someone could break my ssh, they could do what they want to my gitlab presence,and I’m guessing someone at gitlab is paid and qualified to make that call.
A VPN will always be better for this purpose, but as long as you properly secure your SSH server, shouldn’t be a problem
Port forwarding will work, but it has major downsides
- Will draw attention of bots
- Secure as long as there are no security holes in openssh (which is rare but has happened)
- You _must_ harden the ssh server by disabling password auth, putting behind fail2ban
There are far better and safer alternatives that I would recommend over exposing a raw port to the world.
- Tailscale
- Wireguard/OpenVPN
- The bots are looking anyways.
- The other options being presented are various VPNs. OpenSSH has far more eyes on it, for much longer than any of the VPNs. Both generally run as root on the host and so have similar attack surfaces.
- Disabling password auth is less important than having good passwords, but is still a good idea since turning off passwords guarantees no bad passwords. Fail2ban provides no security.
I would also add twingate as an alternative.
This is my current hardened sshd configuration.
ssh/sshd_config: https://pastebin.com/7tH36TdJ
- Public key authentication and 2fa using oathtool are used to authenticate.
- Logging in is only possible for members of the ‘ssh-user’ group.
- “root” login is disabled through “PermitRootLogin”, “DenyGroups”, and “DenyUsers”.
- “restricted” has the ability to log in from any host.
- “user” is limited to using the internal network to log in.
- ‘admin’ can only log in when connected via WireGuard.
- “sftp” may login, but only uses the sftp server. There is no shell available.
pam.d/sshd: https://pastebin.com/eqkisf4F
- All successful pre-2FA logins will trigger the ‘ssh-login-alert’, which sends an NTFY alert containing the time, date, user, and host IP.
- The use of /etc/users.deny prevents root login.
- The use of /etc/users.allowed permits login by “restricted”, “user”, “admin” and “sftp”.
- 2FA and ssh-login-alert trigger do not apply to “sftp”