#!/bin/bash
#
# Simple shell wrapper to proxy ssh appropriately when only SOMETIMES
# behind a draconian firewall.  Indended for use inside an ssh-config
# file, something like this:
#
#    Host *
#      ProxyCommand $HOME/.ssh/proxy httpproxy.foo.com 8080 %h %p
#
# Generally, the usage of this is:
#    proxy [optional-args] <http-proxy> <proxy-port> <host> <port>
# with optional args:
#   [-n <netcat>] - version or path to netcat/direct-connect program
#   [-t <tunnel>] - version or path of http-tunnel program
#   [-w <timout>] - timeout (seconds) to test connection to proxy server
#
# This script assumes both netcat (nc) and corkscrew (an http-proxy
# available from http://www.agroman.net/corkscrew).  Netcat is used
# both to detect the availablility of the destination or proxy hosts
# as well as for direct connections.  Both are assumed to be resident
# in your PATH.  If not, you may specify a different http-proxy or
# alternate location for netcat on the command line (in your ssh
# config) OR, of course, "use the source, Luke"...
#
# Author:  Eric Engstrom (engstrom(-AT-)m t u(-DOT-)n e t)
#
# $Id: ssh-proxy,v 1.6 2004-08-11 16:50:55 eric Exp $
##

# set to "echo" to debug
DEBUG=

# defaults
tunnel=corkscrew
netcat=nc
timeout=8
# if "nc" not found, try "netcat"
if ! type -p ${netcat} >/dev/null 2>&1; then
  netcat="netcat"
fi
if ! type -p ${netcat} >/dev/null 2>&1; then
  echo "Cannot find netcat - failing..." 1>&2
  exit 1;
fi

# parse args - can specify -n <netcat> and/or -t <tunnel>
while getopts "n:t:w:" OPT; do
  #echo "$OPT $OPTARG $OPTIND"
  case $OPT in
    n) netcat=$OPTARG ;;
    t) tunnel=$OPTARG ;;
    w) timeout=$OPTARG ;;
  esac
done
shift $(($OPTIND - 1))

# test connection to proxy, then tunnel or not
if ${netcat} -w ${timeout} -z $3 $4 >/dev/null 2>&1; then
  $DEBUG exec ${netcat} $3 $4
else
  $DEBUG exec ${tunnel} $*
fi

##