BIOSUtilities/Apple_EFI_PBZX.py

#!/usr/bin/env python3 -B
# coding=utf-8

"""
Apple PBZX Extract
Apple EFI PBZX Extractor
Copyright (C) 2021-2024 Plato Mavropoulos
"""

import ctypes
import logging
import lzma
import os

from common.comp_szip import is_szip_supported, szip_decompress
from common.path_ops import make_dirs, path_stem
from common.patterns import PAT_APPLE_PBZX
from common.struct_ops import get_struct, UInt32
from common.system import printer
from common.templates import BIOSUtility
from common.text_ops import file_to_bytes

TITLE = 'Apple EFI PBZX Extractor v2.0'


class PbzxChunk(ctypes.BigEndianStructure):
    """ PBZX Chunk Header """

    _pack_ = 1
    _fields_ = [
        ('Reserved0', UInt32),  # 0x00
        ('InitSize', UInt32),  # 0x04
        ('Reserved1', UInt32),  # 0x08
        ('CompSize', UInt32),  # 0x0C
        # 0x10
    ]

    def struct_print(self, padd):
        """ Display structure information """

        printer(['Reserved 0     :', f'0x{self.Reserved0:X}'], padd, False)
        printer(['Initial Size   :', f'0x{self.InitSize:X}'], padd, False)
        printer(['Reserved 1     :', f'0x{self.Reserved1:X}'], padd, False)
        printer(['Compressed Size:', f'0x{self.CompSize:X}'], padd, False)


def is_apple_pbzx(input_file):
    """ Check if input is Apple PBZX image """

    input_buffer = file_to_bytes(input_file)

    return bool(PAT_APPLE_PBZX.search(input_buffer[:0x4]))


def apple_pbzx_extract(input_file, extract_path, padding=0):
    """ Parse & Extract Apple PBZX image """

    input_buffer = file_to_bytes(input_file)

    make_dirs(extract_path, delete=True)

    cpio_bin = b''  # Initialize PBZX > CPIO Buffer

    cpio_len = 0x0  # Initialize PBZX > CPIO Length

    chunk_off = 0xC  # First PBZX Chunk starts at 0xC
    while chunk_off < len(input_buffer):
        chunk_hdr = get_struct(input_buffer, chunk_off, PbzxChunk)

        printer(f'PBZX Chunk at 0x{chunk_off:08X}\n', padding)

        chunk_hdr.struct_print(padding + 4)

        # PBZX Chunk data starts after its Header
        comp_bgn = chunk_off + PBZX_CHUNK_HDR_LEN

        # To avoid a potential infinite loop, double-check Compressed Size
        comp_end = comp_bgn + max(chunk_hdr.CompSize, PBZX_CHUNK_HDR_LEN)

        comp_bin = input_buffer[comp_bgn:comp_end]

        try:
            # Attempt XZ decompression, if applicable to Chunk data
            cpio_bin += lzma.LZMADecompressor().decompress(comp_bin)

            printer('Successful LZMA decompression!', padding + 8)
        except Exception as error:  # pylint: disable=broad-except
            logging.debug('Error: Failed to LZMA decompress PBZX Chunk 0x%X: %s', chunk_off, error)

            # Otherwise, Chunk data is not compressed
            cpio_bin += comp_bin

        # Final CPIO size should match the sum of all Chunks > Initial Size
        cpio_len += chunk_hdr.InitSize

        # Next Chunk starts at the end of current Chunk's data
        chunk_off = comp_end

    # Check that CPIO size is valid based on all Chunks > Initial Size
    if cpio_len != len(cpio_bin):
        printer('Error: Unexpected CPIO archive size!', padding)

        return 1

    cpio_name = path_stem(input_file) if os.path.isfile(input_file) else 'Payload'

    cpio_path = os.path.join(extract_path, f'{cpio_name}.cpio')

    with open(cpio_path, 'wb') as cpio_object:
        cpio_object.write(cpio_bin)

    # Decompress PBZX > CPIO archive with 7-Zip
    if is_szip_supported(cpio_path, padding, args=['-tCPIO'], check=True):
        if szip_decompress(cpio_path, extract_path, 'CPIO', padding, args=['-tCPIO'], check=True) == 0:
            os.remove(cpio_path)  # Successful extraction, delete PBZX > CPIO archive
        else:
            return 3
    else:
        return 2

    return 0


# Get common ctypes Structure Sizes
PBZX_CHUNK_HDR_LEN = ctypes.sizeof(PbzxChunk)

if __name__ == '__main__':
    BIOSUtility(title=TITLE, check=is_apple_pbzx, main=apple_pbzx_extract).run_utility()