#!/bin/bash
## SSH connection chaining
##
## (C) 2007, Luciano Rocha <strange@nsk.pt>
##
## This program is free software; you can redistribute it and/or
## modify it under the terms of the GNU General Public License
## as published by the Free Software Foundation; either version 2
## of the License, or (at your option) any later version.
## 
## This program is distributed in the hope that it will be useful,
## but WITHOUT ANY WARRANTY; without even the implied warranty of
## MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
## GNU General Public License for more details.
## 
## You should have received a copy of the GNU General Public License
## along with this program; if not, write to the Free Software
## Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston,
## MA 02110-1301, USA.
## 
## Or check the webpage: http://www.gnu.org/licenses/old-licenses/gpl-2.0.html
##
## Documentation:
##
## Include in your .ssh/config:
## host *--*
## proxycommand ssh_p %h %p
##
## And then you can do:
## ssh hosta--hostb--hostc
## scp hosta--hostb--hostc:file .
##
## A user specification is also possible, but not for the last host, for
## that one, you'll have to use ssh's standard user specification (user@host
## or -luser):
## ssh usera_hosta--userb_hostb--hostc -luserc
## scp userc@usera_hosta--userb_hostb--hostc:file .
##
## Compression is disable on all proxy sshs, as traffic is already encrypted.
## Activate compression in the master ssh command, if desired.
##
## Environment variable SSH_CONFIG_FILE can point to a ssh configuration
## file for use in the proxy sshs.

## missing hops
h="${1%--*}"
## nc target
rh="${1##*--}"
p="${2:-22}"


## user for next hop
u=
n="${h##*--}"
if [ -z "${n##*_*}" ]; then
	u=${n%%_*}
	if [ "$h" != "$n" ]; then
		h="${h%--*}--${n##*_}"
	else
		h="${n##*_}"
	fi
fi

echo "${SSH_INDENT}+ connecting to $h for $rh" >&2


exec env SSH_INDENT="${SSH_INDENT} " ssh -o "Compression no" \
	${SSH_CONFIG_FILE:+-F$SSH_CONFIG_FILE} \
	${u:+$u@}$h \
	"echo \"${SSH_INDENT}- connected to $h, forwarding to $rh:$p\" >&2 ; nc -w 3600 $rh $p"