#! /bin/sh
###
### Generate .ssh/authorized_keys files for SSH services
###
### (c) 2015 Mark Wooding
###

###----- Licensing notice ---------------------------------------------------
###
### 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., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA

set -e

## Initial setup.
allow_agent_forwarding=no
allow_x11_forwarding=no
allow_port_forwarding=no
allow_pty=no
env="SSHSVC_USER=@user"
cmd="bin/sshsvc"

## Hook functions.
make_key_line () {
  user=$1
  e=$env
  while :; do
    progressp=t
    case "$e" in
      *@user*) e=${e%%@user*}$user${e#*@user} ;;
      *) progressp=nil ;;
    esac
    case $progressp in nil) break ;; esac
  done
  line="environment=\"$e\""
  echo "$line"
}

make_full_key_line () {
  user=$1
  line=$(make_key_line "$user")
  case "${cmd+t},$line" in
    ,* | *,command=*) ;;
    t,*) line="command=\"$cmd\",$line" ;;
  esac
  case "$allow_port_forwarding" in
    yes) ;; *) line="no-port-forwarding,$line" ;;
  esac
  case "$allow_x11_forwarding" in
    yes) ;; *) line="no-X11-forwarding,$line" ;;
  esac
  case "$allow_agent_forwarding" in
    yes) ;; *) line="no-agent-forwarding,$line" ;;
  esac
  case "$allow_pty" in
    yes) ;; *) line="no-pty,$line" ;;
  esac
  echo "$line"
}

## Scan the command line.
prog=${0##*/} bogusp=nil
conf=sshsvc.conf out=authorized_keys keysdir=keys
head=sshsvc-authkeys.head tail=sshsvc-authkeys.tail
usage () {
  echo "usage: $prog [-c CONF] [-k DIR] [-o OUTPUT] [-H HEAD] [-T TAIL]"
}
while getopts hc:k:o:H:T: opt; do
  case $opt in
    h) usage; exit 0 ;;
    c) conf=$OPTARG ;;
    k) keysdir=$OPTARG ;;
    o) out=$OPTARG ;;
    H) head=$OPTARG ;;
    T) tail=$OPTARG ;;
    *) bogusp=t ;;
  esac
done
shift $(( $OPTIND - 1 ))
case $# in 0) ;; *) bogusp=t ;; esac
case $bogusp in t) usage >&2; exit 1 ;; esac

## Read the configuration.
case $conf in /*) ;; *) conf=./$conf ;; esac
. "$conf"

## Do the thing.
case $out in
  -) exec 3>&1 ;;
  *) exec 3>"$out.new" ;;
esac

echo >&3 "### GENERATED by $prog"

if [ -r "$head" ]; then cat "$head" >&3; fi

for i in "$keysdir"/*.pub; do
  u=${i#*/}; u=${u%.*}; u=${u%%!*}
  l=$(make_full_key_line "$u")
  k=$(cat "$i")
  echo >&3 "$l $k"
done

if [ -r "$tail" ]; then cat "$tail" >&3; fi

echo >&3 "### GENERATED by $prog"

exec 3>&-
case $out in
  -) ;;
  *) mv "$out.new" "$out" ;;
esac