SSH SOCKS tunnel helper script, opens tunnel, checks that the port is open then launches Firefox, the ssh session closes after 10 seconds which is enough time for Firefox to start but the tunnel will remain open till Firefox is closed.

tunnel.sh

#!/bin/bash
# SSH SOCKS tunnel helper script, opens tunnel, checks
# that the port is open then launches Firefox, the ssh
# session closes after 10 seconds which is enough time
# for Firefox to start but the tunnel will remain open
# till Firefox is closed.
#
# Changes: MP - 22/08/2018 - Initial version, tested on Ubuntu 18.04 and Windows under Cygwin
#
# Todo: Add proper detection of Cygwin environment

# Username of account on remote ssh server
USERNAME=username
# Hostname or IP address of remote ssh server
HOST=remotehost.not.a.real.domain
# Port of the remote ssh server
SSH_PORT=remote ssh port eg 22
# Local SOCKS port to create
SOCKS_PORT=8123

echo -ne "Bringing up SOCKS tunnel on port ${SOCKS_PORT}... "
if ssh -D ${SOCKS_PORT} -f -C ${USERNAME}@${HOST} -p ${SSH_PORT} sleep 10 > /tmp/ssh_error 2>&1; then
  echo "done"
else
  echo "failed"
  cat /tmp/ssh_error
  exit 1
fi

echo -ne "Checking status of port ${SOCKS_PORT}... "
if timeout 1 bash -c "</dev/tcp/localhost/${SOCKS_PORT}" -eq 0; then
  echo "open"
else
  echo "closed"
  exit 1
fi

echo -e "Starting Firefox... "

# Check if Firefox is a valid command and execute it, else it could be cygwin so we'll try the Windows version of Firefox
if command -v firefox &> /dev/null; then
  firefox > /dev/null 2>&1 &
else
  FIREFOX="/cygdrive/c/Program Files/Mozilla Firefox/firefox.exe"
  if [ -f "${FIREFOX}" ]; then
    "${FIREFOX}" > /dev/null 2>&1 &
  fi
fi

echo -e "\nNetwork Proxy in the web browser needs to be configured"
echo "Firefox:"
echo "  • Menu (3 bars in the top right corner), click Options or Preferences"
echo "  • Under \"Network Proxy\" click Settings"
echo "  • Check \"Manual proxy connection\""
echo "  • Enter \"localhost\" in SOCKS host"
echo "  • Enter \"8123\" in port"
echo "  • Click \"OK\""
echo "  Optional but recommended, this setting makes Firefox use the proxy server for DNS requests rather than the local client:"
echo "  • In the search bar type \"about:config\" and press enter"
echo "  • Search for \"socks_remote_dns\""
echo "  • If not already set to true double click \"network.proxy.socks_remote_dns\" to set to true"