Linux VPS – Setting Up a Reverse Proxy

tsocks allows multiple SOCKS services, you set it up to use a different SOCKS service (i.e. different ssh -D listening on a different port) for each desired target. man tsocks.conf for more details.

assuming /etc/tsocks.conf containing:

path {
    server = localhost
    server_port = 1081
    reaches = <ip-address-of-server-b>/32
    }
path {
    server = localhost
    server_port = 1082
    reaches = <ip-address-of-server-d>/32
    }

Then you would run

ssh -fND :1081 server-a & sleep 1 ; tsocks ssh server-b
ssh -fND :1082 server-c & sleep 1 ; tsocks ssh server-d

You need to resolve these things for it to work:

1. That the X application can find the X server
   • For SSH there needs to be a tunnel ("ssh -X" and "X11Forwarding yes" in /etc/ssh/sshd_config)
   • The address must be in $DISPLAY (using -e). You must replace "localhost" with the actual IP address of the Docker host seen from the Docker container.
2. That the X application is authorised to talk to the X server
   • Propagate the xauth magic cookie into the Docker container
   • Open up any firewall ports from the Docker host to the Docker container for the X11 port
   • Make sure the SSH server is configured to accept X11 TCP connections on a remote IP.

See my question (and answer) here on StackOverflow for details of how it can be done: https://stackoverflow.com/questions/48235040/run-x11-application-in-a-docker-container-reliably-on-a-server-connected-via-ssh