unpack.py

import sys
import os
import re
import shutil

import utils

DEBUG = False
HEADER_SIZE = 16 * utils.KB # Header size is always 16KB

# Vars
headerScript = ""
headerScriptFound = False
counter = {}
env = {} # Environment variables, set by setenv command

# Parse args
if len(sys.argv) == 1: 
	print ("Usage: unpack.py <firmware> <output folder [default: ./unpacked/]>")
	quit()

inputFile = sys.argv[1]
if not os.path.exists(inputFile):
	print ("No such file: {}".format(inputFile))
	quit()

if len(sys.argv) == 3:
	outputDirectory = sys.argv[2]
else:
	outputDirectory = 'unpacked'

# Create output directory
utils.createDirectory(outputDirectory)

# Find header script
# Header size is 16KB
# Non used part is filled by 0xFF
print ("[i] Analizing header ...")
header = utils.loadPart(inputFile, 0, HEADER_SIZE)
utils.copyPart(inputFile, os.path.join(outputDirectory, "~header"), 0, HEADER_SIZE)

offset = header.find('\xff'.encode(encoding='iso-8859-1'))
if offset != -1:
	headerScript = header[:offset].decode()
	headerScriptFound = True

if not headerScriptFound:
	print ("[!] Could not find header script!")
	quit()
	
if DEBUG:
	print (headerScript)

# Save the script
print ("[i] Saving header script to " + os.path.join(outputDirectory, "~header_script") + " ...")
with open(os.path.join(outputDirectory, "~header_script"), "w") as f:
	f.write(headerScript)

# Parse script
print ("[i] Parsing script ...")
# Supporting filepartload, mmc, store_secure_info, store_nuttx_config
for line in headerScript.splitlines():

	if DEBUG:
		print (line)

	if re.match("^setenv", line):
		params = utils.processSetEnv(line)
		key = params["key"]		
		if not "value" in params:
			del env[key]
		else:
			value = params["value"]
			env[key] = value
			print ("[i] Parsing setenv {} -> {}".format(key, value))

	if re.match("^filepartload", line):
		line = utils.applyEnv(line, env)
		params = utils.processFilePartLoad(line)
		offset =  params["offset"]
		size =  params["size"]

	if re.match("^store_secure_info", line):
		line = utils.applyEnv(line, env)		
		params = utils.processStoreSecureInfo(line)
		outputFile = os.path.join(outputDirectory, params["partition_name"])
		utils.copyPart(inputFile, outputFile, int(offset, 16), int(size, 16))

	if re.match("^store_nuttx_config", line):
		line = utils.applyEnv(line, env)
		params = utils.processStoreNuttxConfig(line)
		outputFile = os.path.join(outputDirectory, params["partition_name"])
		utils.copyPart(inputFile, outputFile, int(offset, 16), int(size, 16))

	if re.match("^mmc", line):
		line = utils.applyEnv(line, env)
		params = utils.processMmc(line)

		if params:

			# if params["action"] == "create":
			# 	nothing here

			if params["action"] == "write.boot":
				outputFile = utils.generateFileName(outputDirectory, params, ".img")
				utils.copyPart(inputFile, outputFile, int(offset, 16), int(size, 16))
				print ("[i] Partition: {}\tOffset: {}\tSize {} ({}) -> {}".format(params["partition_name"], offset, size, utils.sizeStr(int(size, 16)), outputFile))

			if params["action"] == "write.p":
				outputFile = os.path.join(outputDirectory, params["partition_name"] + ".img")
				utils.copyPart(inputFile, outputFile, int(offset, 16), int(size, 16))
				print ("[i] Partition: {}\tOffset: {}\tSize {} ({}) -> {}".format(params["partition_name"], offset, size, utils.sizeStr(int(size, 16)), outputFile))

			if params["action"] == "write.p.continue":
				outputFile = os.path.join(outputDirectory, params["partition_name"] + ".img")	
				utils.copyPart(inputFile, outputFile, int(offset, 16), int(size, 16), append = True)
				print ("[i] Partition: {}\tOffset: {}\tSize {} ({}) append to {}".format(params["partition_name"], offset, size, utils.sizeStr(int(size, 16)), outputFile))

			if params["action"] == "unlzo":
				outputLzoFile = utils.generateFileName(outputDirectory, params, ".lzo")
				outputImgFile = utils.generateFileName(outputDirectory, params, ".img")
				# save .lzo
				print ("[i] Partition: {}\tOffset: {}\tSize {} ({}) -> {}".format(params["partition_name"], offset, size, utils.sizeStr(int(size, 16)), outputLzoFile))
				utils.copyPart(inputFile, outputLzoFile, int(offset, 16), int(size, 16))
				# unpack .lzo -> .img
				print ("[i]     Unpacking LZO (Please be patient) {} -> {}".format(outputLzoFile, outputImgFile))
				utils.unlzo(outputLzoFile, outputImgFile)
				# delete .lzo
				os.remove(outputLzoFile)

			if params["action"] == "unlzo.continue":
				if not params["partition_name"] in counter:
					counter[params["partition_name"]] = 0
				counter[params["partition_name"]] += 1

				outputImgFile = os.path.join(outputDirectory, params["partition_name"] + ".img")
				outputChunkLzoFile = os.path.join(outputDirectory, params["partition_name"] + str(counter[params["partition_name"]]) + ".lzo")
				outputChunkImgFile = os.path.join(outputDirectory, params["partition_name"] + str(counter[params["partition_name"]]) + ".img")
				# save .lzo
				print ("[i] Partition: {}\tOffset: {}\tSize {} ({}) -> {}".format(params["partition_name"], offset, size, utils.sizeStr(int(size, 16)), outputChunkLzoFile))
				utils.copyPart(inputFile, outputChunkLzoFile, int(offset, 16), int(size, 16))
				# unpack chunk .lzo -> .img
				print ("[i]     Unpacking LZO (Please be patient) {} -> {}".format(outputChunkLzoFile, outputChunkImgFile))
				utils.unlzo(outputChunkLzoFile, outputChunkImgFile)
				# append the chunk to main .img
				print ("[i]     {} append to {}".format(outputChunkImgFile, outputImgFile))
				utils.appendFile(outputChunkImgFile, outputImgFile)
				# delete chunk
				os.remove(outputChunkLzoFile)
				os.remove(outputChunkImgFile)