Setting up an SSH tunnel with Net::SSH::Gateway then working through that tunnel

tunneler.rb

require 'net/ssh'
require 'net/ssh/gateway'

# Connect to the gateway machine
gateway = Net::SSH::Gateway.new('host.to.tunnel.from', 'user.name')

# Open the tunnel (in this example we are using port 5900 locally)
gateway.open('host.to.tunnel.to', 22, 5900)

# SSH through our tunnel and grab the list of vault contents
Net::SSH.start('127.0.0.1', 'user.name', :port => 5900) do |ssh|
  some_files = ssh.exec!('cd /data; ls')
end

# Close the tunnel
gateway.close