I was faced with a firewall denying access to the outside world using ssh. All I had was http/https access via a proxy server which required authentication. I had an Ubuntu jump host outside the network connected to the internet with a free 443 port. I tried accessing that with httptunnel and proxytunnel, but could get neither to work with this proxy server.
The solution that worked in this particular case was stunnel. It can wrap any TCP connection into an https session which was not rejected by the proxy server I was facing.