Setup a secure (SSH) tunnel as a systemd service. #systemd #ssh #ssh-tunnel #ssh-forward

README-setup-tunnel-as-systemd-service.md

README

Create a template service file at /etc/systemd/system/secure-tunnel@.service. The template parameter will correspond to the name of target host:

[Unit]
Description=Setup a secure tunnel to %I
After=network.target

[Service]
Environment="LOCAL_ADDR=localhost"
EnvironmentFile=/etc/default/secure-tunnel@%i
ExecStart=/usr/bin/ssh -NT -o ServerAliveInterval=60 -o ExitOnForwardFailure=yes -L ${LOCAL_ADDR}:${LOCAL_PORT}:localhost:${REMOTE_PORT} ${TARGET}

# Restart every >2 seconds to avoid StartLimitInterval failure
RestartSec=5
Restart=always

[Install]
WantedBy=multi-user.target

We need a configuration file (inside /etc/default) for each target host we will be creating tunnels for. For example, let's assume we want to tunnel to a host named jupiter (probably aliased in /etc/hosts). Create the file at /etc/default/secure-tunnel@jupiter:

TARGET=jupiter
LOCAL_ADDR=0.0.0.0
LOCAL_PORT=20022
REMOTE_PORT=22

Note that for the above to work we need to have allready setup a password-less SSH login to target (e.g. by giving access to a non-protected private key).

Now we can start the service instance:

systemctl start secure-tunnel@jupiter.service
systemctl status secure-tunnel@jupiter.service

Or enable it, so it get's started at boot time:

systemctl enable secure-tunnel@jupiter.service

Thank you

Thank for this, I've used adaptations of this a few times now. The latest was a dynamic proxy so that apt and web traffic could all be tunneled though a jump host.

Hello,

i have at least the same example

[Unit]
Description=Tunnel for HA
After=network.target

[Service]


ExecStart=/usr/bin/ssh -i "/home/pi/.ssh/id_rsa" -p 22 -o ExitOnForwardFailure=yes -o ServerAliveInterval=60 -N -R 31281:localhost:8123 login@server.com

RestartSec=5s
Restart=always

[Install]
WantedBy=multi-user.target

But it do not start. i get

It also do not shows any logs with command

PLease advice me what have i've done wrong?

Thanks a lot!

Hi, did you solve this problem ？

Hi, did you solve this problem ？

Yes https://github.com/AlexxIT/hassio-addons/tree/master/ssh_tunnel

I also think it's better to exec in user mode. But my machine systemctl has bug when running --user, so I add user permission in service file

@sunnyszy I forked aswell and added a littlebit of stuff:

https://gist.github.com/ranomier/2e6ae91fa26cc0c0d6557238a8f60764

Greetings colleagues. Tell me what I need to add in the config. to make my unit work.
I'm setting up ssh sock-proxy.
In the terminal, the command looks like this:
ssh -D 0.0.0.0:8080 user@remoteserver -i /home/user/.ssh/id_rsa

What is the alternative to this on Windows? Or am I missing something

What is the alternative to this on Windows? Or am I missing something

Install cygwin and you get it on Windows.

Instead of setting up the service template to a fixed set of environment variables and to use distinct environments, why not setup the service with minimal default options like timeouts and disabling password prompt, and to use distinct ssh_config.d profiles instead, e.g. /etc/systemd/system/ssh-client@.service:

[Unit]
Description=Auto-SSH to %i
After=network.target

[Service]
ExecStart=/usr/bin/ssh -NT -o PasswordAuthentication=no -o TCPKeepAlive=yes -o ServerAliveInterval=60 %i
Restart=always
RestartSec=5

[Install]
WantedBy=multi-user.target

...and then define your ssh_config in /etc/ssh/ssh_config.d/auto-ssh (name doesn't actually matter):

Host myalias
    User myuser
    HostName hostname.example.org
    ProxyJump other@jumphost.example.org
    …

...and then activate it:
$ systemctl start ssh-client@myalias.service

...or enable autostart, respectively:
$ systemctl enable ssh-client@myalias.service

I'm using this concept since a while ;)

I use this especially to open SOCKS proxies (DynamicForward) to access private kubernetes-API-endpoints via bastion-hosts configured as --user services.

https://gist.github.com/drmalex07/c0f9304deea566842490?permalink_comment_id=3145418#gistcomment-3145418