3DS NATIVE_FIRM unpacker

firmunpack.sh

#!/bin/bash -e

odbin() {
	od --output-duplicates --address=none --endian=little $*
}

rdu32() {
	odbin --format d4 --skip-bytes "$2" --read-bytes 4 "$1" | tr -c -d [:digit:]
}

rdu32hex() {
	printf 0x%08X $(rdu32 "$1" "$2")
}

rdhex() {
	odbin --format x1 --skip-bytes "$2" --read-bytes "$3" "$1" | tr -c -d [:xdigit:]
}

if [ $# != 2 ]; then
	echo "Usage: $0 firm.bin outdir" 2>&1
	exit 1
fi

FIRM="$1"
OUTDIR="$2"

if [ ! -f "$FIRM" ]; then
	echo "Firmware file not found"
	exit 2
fi

if [ ! -d "$OUTDIR" ]; then
	mkdir "$OUTDIR"
fi

MAGIC=$(rdu32hex "$FIRM" 0x000)
echo "FIRM magic:        $MAGIC"
if [ $MAGIC != 0x4D524946 ]; then
	echo "Invalid magic (expected 0x4D524946)"
	exit 3
fi

ARM11EP=$(rdu32hex "$FIRM" 0x008)
echo "ARM11 entry point: $ARM11EP"

ARM9EP=$(rdu32hex "$FIRM" 0x00C)
echo "ARM9 entry point:  $ARM9EP"

echo

for SECID in 0 1 2 3; do
	echo "Section $SECID:"
	SECBASE=$((0x040 + $SECID * 0x30))

	SECOFF=$(rdu32hex "$FIRM" $(($SECBASE + 0x000)))
	echo " - File offset:  $SECOFF"

	SECADDR=$(rdu32hex "$FIRM" $(($SECBASE + 0x004)))
	echo " - Load address: $SECADDR"

	SECSIZE=$(rdu32 "$FIRM" $(($SECBASE + 0x008)))
	echo " - Size:         $SECSIZE"

	if [ $SECSIZE -eq 0 ]; then
		continue
	fi

	SECTYPE=$(rdu32 "$FIRM" $(($SECBASE + 0x00C)))
	echo -n " - Type:         $SECTYPE "
	case $SECTYPE in
		0)
			echo "(ARM9)"
			;;
		1)
			echo "(ARM11)"
			;;
		*)
			echo "(unknown)"
	esac

	SECSHA=$(rdhex "$FIRM" $(($SECBASE + 0x010)) 32)
	echo " - SHA256: $SECSHA"

	SECFILE="$OUTDIR/sec$SECID.bin"
	dd if="$FIRM" of="$SECFILE" skip=$(($SECOFF)) count=$SECSIZE iflag=count_bytes,skip_bytes status=none
	echo "$SECSHA *$SECFILE" | sha256sum --check --quiet

	echo
done