SSH notes

Tunnel a remote port to localhost through a jump host

With -o ProxyCommand:

ssh -o ProxyCommand='ssh -W %h:%p -i myssh.key $user@$jumpserver_ip' -i myssh.key -L $local_port:$address_to_forward:$port_to_forward $user@$remote_ip

Or with -J and the follwing ~/.ssh/config:

Host <jumpserver_ip>
    User <user>
    IdentityFile /path/to/myssh.key

ssh -J $user@$jumpserver_ip -i myssh.key -L $local_port:$address_to_forward:$port_to_forward $user@remote

Make a port on a remote host available for kubernetes pods through an ssh jump host

ssh -g: Allows remote hosts to connect to local forwarded ports.

Remote forward the port to the jump host

$remote_ip:$remote_port has to be available on the network of the host from which this command is executed.

ssh $user@$jumpserver_ip -gfNT -R $remote_port:$remote_ip:$remote_port

Local forwad the port from the jump server to a pod

Create a pod in kubernetes with ssh in it an expose the target port

kubectl run ssh-tunnel \
    --rm \
    --image=linuxserver/openssh-server \
    --restart=Never \
    --expose --port $remote_port \
    -- bash -c 'while true; do sleep 30; done;'

Exec into the pod

kubectl exec -it ssh-tunnel -- bash

Open the tunnel inside the pod

ssh $user@$jumpserver_ip -gfNT -L $remote_port:127.0.0.1:$remote_port

Now other pods can access $remote_ip:$remote_port using ssh-tunnel:$remote_port.