It happened to me when I was configuring IP geoblocking: Only whitelist IP ranges are allowed. That was fetched from a trusted URL. If the DNS provider just happened to not be on that list, the whitelist would become empty, blocking all IPs. Literally 100% proof firewall; not even a ping gets a pass.
OPNsense has an anti-lock-out rule at the top for a reason 😁
Happened to me in work once… I was connected via SSH to one of our test machines, so I could test connection disruption handling on a product we had installed.
I had a script that added iptables rules to block all ports for 30 seconds then unblock them. Of course I didn’t add an exception for port 22, and I didn’t run it with nohup, so when I ran the script it blocked the ports, which locked me out of SSH access, and the script stopped running when the SSH session ended so never unblocked the ports. I just sat there in awe of my stupidity.
We’ve all experienced the walk of shame to the server room to hook up a monitor keyboard.
Ah, if only it was a server room and not a customer 3 hours drive away. And he’d closed and gone home for the night.
Fortunately it just needed a reboot, and I was able to talk him through that in the morning.
Oof I did a firmware upgrade on my main external firewall.
The upgrade went fine but when we added an ISP a month or so prior, I forgot to redistribute the ISPs routes. While all my ISPs were technically working, and the firewall came back up, nothing below it could get to the internet, so it was good as down.
Cue the 1.5 hour drive into the office…
Had that drive to think about what went wrong. Got into the main lobby, sat down, joined the wifi, and fixed it in 3 minutes.
Didn’t even get to my desk or the datacenter.
Oof… well you can just say “it must be some hardware problem or something… maybe a reboot will fix it.”
lol. When I get asked what went wrong at work. So. A solar flare can swap the bits…
Out of curiousity, how would nohup make your situation different? As I understand, nohup makes it possible to keep terminal applications running even when the terminal session has ended.
If the script was supposed to wait 30 secs and then unblock the ports, running with nohup would have allowed the ports to be unblocked 30 secs later. Instead, the script terminated when the SSH session died, and never executed the countdown nor unblock.
Thanks for the elaborate answer!
Any time! :)
the script stopped running when the SSH session ended so never unblocked the ports
the script stopped running when the SSH session ended
tmux
Always use tmux when possible for remote connections.What does it do in this case?
Tmux essentially creates a pseudo-shell that persists between sessions.
So you can start a process, detach the session, start something else, disconnect, come back next week, and check on it.
It does other things too. Like console tiling.
Well, the script could keep running even after he would have detached from that tmux session due to losing ssh connection. And since that script would unblock all ports after 30 seconds…
(Same use case as nohup that they mentioned)
Connects a monitor and a keyboard to the Raspberry Pi
Defeatedly Connects a monitor and a keyboard to the Raspberry Pi
I accidentally put all the interfaces on my router running openwrt into the wrong firewall zone so now I can’t access it via ssh or the web interface. I already had it configured though and it still works so I’m just ignoring the problem until something breaks
There is nothing more perminant than a temporary solution.
What is a good firewall that can also block ports published with docker? I’d need it to run on the same host.
Ufw should work, jus
ufw block/limit/allow port numberI remember trying with ufw and the docker ports were still open. Iirc I’ve read somewhere that docker and ufw both use the same underlying software, so ufw cannot block docker (IP tables?)
Hmm, not sure. I know with docker you can “mock” ports for the container, where the port the container sees is different than the port on the system. Maybe you can do something with that?
I can configure the containers in ways that don’t require ports to be published for the real network, but that’s always possible. It would still be nice to have a firewall that can block even those containers that try to publish their ports to the whole (real) network.
Are your Docker containers connecting to the network (eg using ipvlan or macvlan)? The default bridge network driver doesn’t expose the container publicly unless you explicitly expose a port. If you don’t expose a port, the Docker container is only accessible from the host, not from any other system on the network.
They are Only in my docker bridge networks and have a few published ports
If you don’t want the Docker container to be accessible from other systems then just don’t publish the port.
Yeah of course, that’s what I’m doing anyways, but the purpose of a firewall would be defense in depth, even is something were to be published, the firewall got it.
I know this is posted in funny, but whatever. You could still login locally using keyboard and monitor. Uncool, but it works
You are assuming there is a keyboard and monitor plugged to it, and that the computer is somewhere nearby.
None of those are automatically true. And when it’s nearby, it’s usually easier to just get the SD card into another computer and edit the configuration.
That moment when you forget to run sudo ufw allow ssh after enabling the firewall
You mean before?
