Ngrok SystemD Service

This is going to be a quick post, but it’s still something that I like. I love systemd, and try to (over)use it every time I can.

This is one of those use-cases where I can use ngrok to freely demo my app without having to set up a cloud instance or open up a port in my router. The simple usage of running ngrok is fine for simple cases like hosting a minecraft server for an hour, but if you need to run it in the background you’d need a service. This is all done without the use of sudo or becoming root; you just need to set up ngrok and have a machine with systemd.

Over at .config/systemd/user/ngrok.service you can make a simple service

[Unit]
Description=Ngrok

[Service]
ExecStart=/tmp/ngrok http --log=stdout 8080

[Install]
WantedBy=multi-user.target

Your /tmp/ngrok could be (and should be) placed elsewhere for a permanent location. Then,

systemctl --user daemon-reload
systemctl --user start ngrok

and that’s it! You got yourself a user-level service, i.e. you can do this on any Linux machine you can ssh to without the need for any sort of privilege.

You can use this as a backdoor while red-teaming1. You can use it for a local minecraft server. You can use it for simple web-apps. Good luck 🙂.

  1. This provides some security, since ngrok supports any tcp-based protocol like ssh, and it provides https out of the box. It also is a generic domain, whereas having your static internet facing C2 server make a reverse ssh-tunnel would be much more revealing. My knowledge of backdoor-ing is limited so I’d point you to this. ↩︎