farshidtz/ssh-tunnel repository overview

⁠docker-ssh-tunnel

Dockerized OpenSSH server for port forwarding over SSH.

The Dockerfile is available here⁠.

⁠Build

⁠Extract SSH config file from a temporary container

docker run -d --rm --name temptunnel farshidtz/ssh-tunnel
docker cp temptunneler:/etc/ssh ./ssh-conf
docker stop temptunnel

Add the following to the end of ./ssh-conf/sshd_config:

GatewayPorts yes
AllowAgentForwarding no
ForceCommand echo 'Not Allowed.'
ClientAliveInterval 100
ClientAliveCountMax 3

⁠Run

docker run -d --name tunnel \
    -p 8822:22 \
    -p 9900-9910:9900-9910 \
    -v $(pwd)/limited-home:/home/limited/.ssh \
    -v $(pwd)/ssh-conf:/etc/ssh \
    farshidtz/ssh-tunnel

where

• 8822 is the port where the ssh-server can be reached locally
• 9900-9910 is the range of ports that are forwarded to the host
• limited-home is the home directory of the limited user. The public key of the user should be placed in ./limited-home/.ssh/authorized_keys for key-based authentication.
• ssh-conf is the directory containing ssh server config files

⁠Get the logs

docker logs --timestamps -f tunnel

⁠Open a tunnel (using autossh)

autossh -TNn -f -R :$9901:localhost:22 -p 8822 [email protected]

where

• Local port 22 is forwarded to server as port 9901 at example.com public address and 8822 port for the ssh-tunnel server