A shell script for sending BTLE commands to the DEFCON Furs DC27 badge. Requires Bash, BlueZ, and not much else.

DCF27_badge_BTLE_client.sh

#!/bin/bash

set -e

MAGIC_RAND_COLOR='7e'
MAGIC_AWOO='a0'
MAGIC_BEACON='00'
# The docs say MAGIC_EMOTE is b3. The docs are wrong.
MAGIC_EMOTE='b2'
MFG_FLAGS='ff ff 71'
DEV_NAME='BOGOBLE'

color="$MAGIC_RAND_COLOR"
iface='hci0'
sn='8678'


function printHelp {
  cat <<EOHELP
BTLEComm.sh - Control nearby DEFCON Furs DC26 badges via BTLE beaconns.
Usage:
    BTLEComm.sh [-i interface] [-s serial] <command> [argument]
Flags:
    -c, --color COLOR         Hex byte for the color using the badge's weird
                              format. Examples below.
                                  00 = red
                                  28 = green
                                  50 = blue
                                  78 = red
                              There are two special values.
                                  7e = white
                                  7f = random
    -i, --interface IFACE     The Bluetooth interface to broadcast from.
                              Defaults to $iface.
    -s, --serial SERIALNUM    The badge serial number to use.
                              Default to $sn.
    -t, --time SECONDS        Duration of the broadcase. Infinite by default.
Commands:
    awoo         - Starts a howl with a maximum TTL.
    beacon       - Broadcasts the same beacons that an idle badge would.
    emote [face] - Causes nearby badges to display an emote.
                   Accepts an optional argument to specify 2 characters for
                   the face. Only uppercase letters, numbers, most special
                   characters, and lowercase "o" are supported. Examples below.
                       emote '^^'
                       emote '>>'
                       emote 'oO'
                   Special emotes such as 'owo' appear to have been removed.
EOHELP
  exit
}


function decToHex {
  printf "%02x" "$1"
}


function genFieldLength {
  data="$1"
  data_len="$(($(echo "$data" | sed 's/ //g' | wc -c - | sed 's/ .*//') / 2))"
  data_hex_len="$(decToHex "$data_len")"
  echo "$data_hex_len"
}


function setAdvertParams {
  payload="$1"
  mfg_len="$(genFieldLength "$MFG_FLAGS $payload")"
  hex_name="$(asciiToHex "$DEV_NAME")"
  name_len="$(($(genFieldLength "$hex_name") + 1))"
  pkt="03 19 dc 27 02 01 06 $name_len 09 $hex_name $mfg_len $MFG_FLAGS $payload"
  pkt_len="$(genFieldLength "$pkt")"
  # https://gist.github.com/GermaniumSystem/d785ab9717dda672419740a40b0623bb
  hcitool -i  "$iface"  cmd 0x08 0x0008 $pkt_len $pkt >/dev/null
}


function asciiToHex {
  # This limits the input to 16 bytes, but no commands should be this long.
  printf -- "$1" | od -t x1 | head -n 1 | sed -r 's/^[^ ]+ //'
}


function serialHex {
  # The two bytes need to be flipped for the subsequent hcitool command.
   printf "%04x\n" "$sn" | sed -r 's/(..)(..)/\2 \1/'
}


function stop_tx {
  # Stop transmitting on ^C.
  hciconfig "$iface" noleadv
  echo -e "\nTransmission stopped."
}


# Sanity checks.
if [ -z "$(which hciconfig)" ] ; then
  echo "Could not locate hciconfig! Does this system have BlueZ?"
  exit 10
fi
if [ -z "$1" ] ; then
  printHelp
fi
if [ "$(id -u)" -ne "0" ] ; then
  echo -e "\nWARNING: This script probably won't work when not run by root.\n"
fi
if ps ax | grep -v 'grep' | grep -qi 'bluetoothd' ; then
  echo -e "\nWARNING: bluetoothd is running! This may break things.\n"
fi


# Parse args.
while [[ $# -gt 0 ]]; do
  key=$1
  case $key in
    -h|--help)
      printHelp
    ;;
    -c|--color)
      color="$2"
      shift
      shift
    ;;
    -i|--interface)
      iface="$2"
      shift
      shift
    ;;
    -s|--serial)
      sn="$2"
      shift
      shift
    ;;
    -t|--time)
      txtime="$2"
      shift
      shift
    ;;
    *)
      cmd="$1"
      if [ -n "$2" ] ; then
        arg="$2"
        shift
      fi
      shift
    ;;
  esac
done


#echo "Generating payload..."
sn_bytes="$(serialHex)"
case $cmd in
  awoo)
    # Magic byte, two serial num bytes, TTL byte, two origin serial num bytes.
    data="$MAGIC_AWOO $sn_bytes ff $sn_bytes"
  ;;
  beacon)
    # Magic byte, two serial num bytes.
    data="$MAGIC_BEACON $sn_bytes"
  ;;
  emote)
    # Magic byte, optional color byte, 2 optional emote bytes.
    data="$MAGIC_EMOTE"
    if [ -n "$arg" ] ; then
      arg_hex="$(asciiToHex "$arg")"
      data="$MAGIC_EMOTE $color $arg_hex"
    fi
    echo "$data"
  ;;
  *)
    echo "Unknown command '$cmd'"
    exit 2
  ;;
esac


echo "Bringing interface $IFACE up..."
hciconfig "$IFACE" up

#echo "Setting advertisement parameters..."
setAdvertParams "$data"

#echo "Enabling advertisement..."
hciconfig "$IFACE" leadv 3

trap stop_tx INT # Stop trasmitting if ^C is pressed.

if [ -n "$txtime" ] ; then
  printf "Broadcasting! Stopping transmission in $txtime seconds."
  for i in $(seq 1 "$txtime"); do
    printf '.'
    sleep 1s
  done
  stop_tx
else
  printf "Broadcasting! Press ^C to stop transmission."
  while true ; do
    printf '.'
    sleep 1s
  done
fi