SImple tool for unpacking and repacking firmware files with automatic squashfs decompression allowing for quick and easy embedded filesystem modifications

firmware-tool

#!/usr/bin/env python3

import sys
import os

def usage():
    print("Usage: firmware-tool <(u)npack/(p)ack> <binary file/unpacked directory> [output filename]")
    exit(0)

if len(sys.argv) < 3:
    usage

if sys.argv[1] not in ["u", "p"]:
    usage

if len(sys.argv) < 4:
    outputFirmware = "packed_firmware.bin"
else:
    outputFirmware = sys.argv[3]

os.system(f"cp {sys.argv[2]} {outputFirmware}")

sqfsPath = "unpacked/squashfs"

class FirmwarePart:
    def __init__(self, name, offset, size, forceOffset = False, forceSize = False):
        self.name = name
        self.offset = offset
        self.size = size
        self.forceOffset = forceOffset
        self.forceSize = forceSize

"""
SPECIFY YOUR FIRMWARE PARTS HERE
using the output of `binwalk firmware.bin`,
with the format FirmwarePart("part name", offset in bytes, size in bytes, whether to force the part offset, whether to force the part size),
currently set for the firmware of 3G-6408n_v1.19.bin
"""
firmware_parts = [
    FirmwarePart("misc-header-data", 0, 11288),
    FirmwarePart("lzma-misc-data", 11288, (1114112 - 11288)),
    FirmwarePart("squashfs", 1114112, 4353626),
    FirmwarePart("misc-footer-data", 5467738, (5468162 - 5467738))
]

if sys.argv[1] == "u":
    firmwareFile = open(sys.argv[2], "rb")
    os.system("mkdir -v unpacked")
    for part in firmware_parts:
        outfile = open("unpacked/" + part.name + ".bin", "wb")
        firmwareFile.seek(part.offset, 0)
        data = firmwareFile.read(part.size)
        outfile.write(data)
        outfile.close()
        print(f"Wrote {part.size} bytes to unpacked/{part.name}.bin")
        if part.name == "squashfs":
            if os.system(f"unsquashfs -d {sqfsPath} {sqfsPath}.bin"):
                print(f"Extracted {sqfsPath}.bin into {sqfsPath}/")
                os.remove(f"{sqfsPath}.bin")

if sys.argv[1] == "p":
    firmwareFile = open(outputFirmware, "wb")
    for part in firmware_parts: 
        if part.name == "squashfs":
            if os.path.exists(f"{sqfsPath}.bin"):
                print(f"File {sqfsPath}.bin already exists, removing in order to avoid problems")
                os.remove(f"{sqfsPath}.bin")
            os.system(f"mksquashfs {sqfsPath}/* {sqfsPath}.bin -comp lzma -no-xattrs -no-sparse -no-progress -quiet") 
        
        print(f"Repacking {part.name} from {sys.argv[2]}/", end="")
        if part.forceOffset:
            firmwareFile.seek(part.offset, 0)
            print(f", with forced offset set to {part.offset}", end="")

        unpackedPart = open(sys.argv[2] + "/" + part.name + ".bin", "rb")

        if part.forceSize:
            firmwareFile.write(unpackedPart.read(part.size))
            print(f", with forced size set to {part.size}", end="")
        else:
            firmwareFile.write(unpackedPart.read())
        print()
        unpackedPart.close()

shit, binwalk gives wrong size data, gotta fix that