Forward Port To Windows

Access a Web Service on a Ubuntu Server from Windows with Port forwarding. Using a standard port (needs root), but still use the users ssh configuration (needs the user, not root).

Server Setup

• Docker container is binded to 127.0.0.1:4200->4200/tcp
• nginx as a reverse proxy: redirect traffic from :80 -> to :4200
• /etc/hosts contains: 127.0.0.1 my-domain.local to access webservice using this domain
  • we need to access all request using this domain, because the web app, uses the same domain for the rest API

Extension to access the same from another host

• C:\Windows\System32\drivers\etc\hosts: add 127.0.0.1 my-domain.local
  • to have the same domain name locally available
• Because we would like to use a non-root port for ssh -> so that we can use the users .ssh/config (and keys) we add a simple local redirect using socat (which runs as root)
  • setup a simple redirect as systemd service

    sudo apt install socat
    cat /etc/systemd/system/domain-local-80.service
      
    [Unit]
    Description=Expose domain.local:80 inside WSL
    After=network.target
        
    [Service]
    ExecStart=/usr/bin/socat TCP-LISTEN:80,bind=127.0.0.1,fork,reuseaddr TCP:127.0.0.1:4200
    Restart=always
    AmbientCapabilities=CAP_NET_BIND_SERVICE
        
    [Install]
    WantedBy=multi-user.target
    

  • manage service

    sudo systemctl daemon-reload
    sudo systemctl enable --now domain-local-80.service
    # verify
    sudo systemctl status domain-local-80.service
    

• SSH Tunnel: finally we can redirect socats output to the remote server

  # params
  #   -N: No remote command -> no shell start up, no command injection TTY
  #   -f: **f**ork -> Background
  #   ServerAliveInterval=60: Prevents timeout (resend every 60s)
  ssh -L 4200:my-domain.local:80 -N -f -o ServerAliveInterval=60 ssh-config-entry
  
  # to exit the background process
  ## simple classic way
  ps aux | grep "ssh"
  kill x
  
  ## simple easy way
  pgrep -f "ssh -L"
  pkill -f "ssh -L"
    
  ## or other ways
  ss -ltnp | grep ":4200"
  sudo lsof -iTCP:4200 -sTCP:LISTEN
  

Whole setup overview