orange_hexauth

#!/bin/sh

# Heavily inspired by https://lafibre.info/remplacer-livebox/tuto-remplacer-la-livebox-par-un-routeur-dd-wrt-internet-tv/

__usage(){
  cat << EOH
$0 [-h]

$0 creates a hex stream (that is not \\n terminated) that can be used in DHCP
clients (v4 and v6) to authenticate to Orange France's network. The hex stream
is intended to be cat(1)-ed with configuration parts to create a complete file
(such as dhclient.conf(5)).

-h : display this help text

ENVIRONMNENT VARIABLES

You MUST specify FTI_USER and FTI_PASS as written in your (paper) contract with
Orange.

EXAMPLES

In crontab:

  FTI_USER=fti/...
  FTI_PASS=...

  ~ 1 * * 0 $0 > /etc/orange_auth_string
  ~ 2 * * 0 cat /etc/dhclient.conf.head /etc/orange_auth_string /etc/dhclient.conf.tail > /etc/dhclient.conf
  ~ 3 * * 0 dhclient vlan832

CAVEATS

Only tested on OpenBSD
EOH
}

while getopts ':h' _opt; do
  case "$_opt" in
    h) __usage ; exit 0 ;;
    *) __usage >&2 ; exit 1 ;;
  esac
done

shift "$((OPTIND-1))"

: "${FTI_USER?"Missing mandatory variable, see $0 -h"}"
: "${FTI_PASS?"Missing mandatory variable, see $0 -h"}"

if ! command -v openssl >/dev/null 2>&1; then
  echo "openssl(1) was no found. WTF?" >&2
  exit 2
fi

if ! command -v md5 >/dev/null 2>&1; then
  md5() {
    openssl md5 | cut -d' ' -f2
  }
fi

# translates individual characters to their hex counterpart and prefixes each
# with `:`
# __tohex foo
# > :66:6f:6f
__tohex() {
  printf '%s' "$1" | hexdump -ve '1/1 ":%.2x"'
}

case "$FTI_USER" in
  fti/*) : ;;
  *) FTI_USER="fti/$FTI_USER" ;;
esac

# random strings
# let's hope this never changes, because if Orange starts using "predictable"
# strings, we're in deep (think: TOTP)
: "${_r:="$(openssl rand -base64 12)"}"
: "${_c:="$(openssl rand -base64 1 | cut -c 1)"}"
# "header"
_o90="1a:09:00:00:05:58:01:03:41"
_o90="$_o90:01:0d$(__tohex "$FTI_USER")"
_o90="$_o90:3c:12$(__tohex "$_r")"
_o90="$_o90:03:13$(__tohex "$_c")"
_o90="$_o90$(printf '%s' "$_c$FTI_PASS$_r" | md5 | sed 's/\(..\)/:\1/g')"

cat << EOM >&2
Generated on $(date) with _r=$_r and _c=$_c
EOM
echo -n "${_o90}"