#!/bin/sh

##  author:  parv, parv UNDERSCORE AT yahoo DOT com
##  date:  dec 24 2001
##
##  license:  free to use as you please w/ proper credit given
##
##  name:  myssh
##
##  purpose:  wrap ssh port transfer options and plain ssh ipv4
##  connections
##
##  usage: to see usage, run...
##     myssh
##


##  use PATH only for what's required...
#    ssh (of course)
#    cat, echo, test
#    awk, sed, (e)grep
#    ps, kill
#
PATH=/bin:/usr/bin

##  set server for regual ssh connection & for port transfer
#
REMOTE_ssh_server=remote.host

## set for transferring port & used to kill 'transferred' connections
#
REMOTE_xfer_host=remote.host


#  ---  be sure you know what you are doing before editing below ---


# ssh options
#  2: use ssh v2 protocol
#  4: force ipv4 address
#  6: force ipv6 address
#  a: disable auhentication agent forwarding
#  C: use compression/gzip
#  f: go to background after authentication
#  L: forward local port
#  N: don't execute remote commands (just port forwarding; ssh2 only)
#  v: be verbose
#  x: disable X11 forwarding
#  X: allow X11 forwording
#
OPT_xfer='-2 -4 -a -x -c blowfish -f -N'
OPT_ssh='-2 -4 -a -x -c blowfish'
#
OPT_xfer="$OPT_xfer -C"
OPT_ssh="$OPT_ssh -C"
#
#OPT_xfer="$OPT_xfer -v -v -v"
#OPT_ssh="$OPT_ssh -v -v -v"
#


usage ()
{
  cat <<_USAGE_
 # see ssh man page for various options given below.
 #
 # befor starting, make sure that you have set your own...
 #   REMOTE_ssh_server -- destination server to connect to
 #   REMOTE_xfer_host -- reciever of the transferred host


 - to transfer local port to remote port, give one of the options...

     `basename $0` ([ftp|21] [telnet|23] [pop3|110] [imap|143] [nntp|119])

   default options for port transfer: $OPT_xfer


 - to start ssh...

    `basename $0` [ssh|22]

  default options for ssh: $OPT_ssh


 - to stop/kill port transfer processes only...
     a. kill all of them...
       `basename $0` [stop|0]

     b. kill cretain ones, specify type...
       `basename $0` [stop|0] ([ftp|21] [telnet|23] [pop3|110] [imap|143] [nntp|119])
_USAGE_
}


# assign service based on 1st argument given
#
case $1 in
  ftp|21)
  SERVICE=ftp

  LOCAL_xfer_port=50021
  REMOTE_xfer_port=21
  ;;

  telnet|23)
  SERVICE=telnet

  LOCAL_xfer_port=50023
  REMOTE_xfer_port=23
  ;;

  pop3|110)
  SERVICE=pop3

  LOCAL_xfer_port=50110
  REMOTE_xfer_port=110
  ;;

  imap|143)
  SERVICE=imap

  LOCAL_xfer_port=50143
  REMOTE_xfer_port=143
  ;;

  news|nntp|119)
  SERVICE=nntp

  LOCAL_xfer_port=50119
  REMOTE_xfer_port=119
  ;;

  ssh|22)
  SERVICE=ssh
  # shift so that rest of $@ can be used as "remote command"
  shift
  ;;

  stop|0)
  SERVICE=stop
  shift
  ;;

  *)
  usage
  exit
  ;;
esac


## kill function, used before starting a service or explicit request
#
kill_me ()
{
  # get ps output & convert spaces to #'s
  #
  PS=$(ps -wax | egrep "ssh.* -L .*:${REMOTE_xfer_host}:.*" | sed 's! !#!g' | egrep -v 'ps -wax|grep|sed')

  # no process found, exit then
  #
  if test -z "$PS"
  then
    echo ' -' no ssh process found, exiting...
    exit 0
  fi

  # otherwise, kill 'em
  #
  for current_ps in $PS
  do
    # restore spaces
    current_ps=$(echo $current_ps | sed 's!#! !g')

    case $1 in
      ftp)
      Pid=$(echo $current_ps | awk '/50021:'"$REMOTE_xfer_host"':21/ {print $1}')
      ;;

      telnet)
      Pid=$(echo $current_ps | awk '/50023:'"$REMOTE_xfer_host"':23/ {print $1}')
      ;;

      pop3)
      Pid=$(echo $current_ps | awk '/50110:'"$REMOTE_xfer_host"':110/ {print $1}')
      ;;

      nntp)
      Pid=$(echo $current_ps | awk '/50119:'"$REMOTE_xfer_host"':119/ {print $1}')
      ;;

      *)
      Pid=$(echo $current_ps | awk '{print $1}')
      ;;
    esac

    if test -z $Pid
    then
      echo ' -' no ssh process found ${1}
    else
      # for debugging only...
      #
      #echo $current_ps

      echo ' -' $1 killing $Pid ...

      kill -SIGTERM $Pid

      echo ' ... done'
    fi
  done

}

#
##  stop, kill actually, ssh clients
#
if test "$SERVICE" = 'stop'
then
  kill_me $1
  exit

#
##  transfer local port
#
elif test "$SERVICE" != 'ssh'
then
  # kill old functions before starting...
  #
  #kill_me

  # create tunnel/forward port only
  #
  echo ' -' ${SERVICE} xfer: localhost $LOCAL_xfer_port '->' $REMOTE_xfer_host $REMOTE_xfer_port
  echo '  ' destination: $REMOTE_ssh_server ...
  echo

  ssh  $OPT_xfer  -L ${LOCAL_xfer_port}:${REMOTE_xfer_host}:${REMOTE_xfer_port} $REMOTE_ssh_server
  rc=$?

  [ $rc -eq 0 ] && echo && echo '  ' ...connection M A D E
  [ $rc -ne 0 ] && echo && echo '  ' ...connection F A I L E D "(rc: ${rc})"

  exit $rc
#
##  start ssh
#
else
  # by chance, we manage to specify a ssh connection, either start
  # ssh or display/exit; i decided to start ssh
  #
  #echo ' -' ssh: $REMOTE_ssh_server

  exec ssh  $OPT_ssh  $REMOTE_ssh_server "$@"
fi

exit
# end of script