#!/usr/bin/env python # SPDX-FileCopyrightText: 2022 Espressif Systems (Shanghai) CO LTD # SPDX-License-Identifier: Apache-2.0 import argparse import os import construct from fatfs_utils.boot_sector import BootSector from fatfs_utils.entry import Entry from fatfs_utils.fat import FAT from fatfs_utils.fatfs_state import BootSectorState from fatfs_utils.utils import FULL_BYTE, LONG_NAMES_ENCODING, PAD_CHAR, FATDefaults, lfn_checksum, read_filesystem from wl_fatfsgen import remove_wl def build_file_name(name1: bytes, name2: bytes, name3: bytes) -> str: full_name_ = name1 + name2 + name3 # need to strip empty bytes and null-terminating char ('\x00') return full_name_.rstrip(FULL_BYTE).decode(LONG_NAMES_ENCODING).rstrip('\x00') def get_obj_name(obj_: dict, directory_bytes_: bytes, entry_position_: int, lfn_checksum_: int) -> str: obj_ext_ = obj_['DIR_Name_ext'].rstrip(chr(PAD_CHAR)) ext_ = f'.{obj_ext_}' if len(obj_ext_) > 0 else '' obj_name_: str = obj_['DIR_Name'].rstrip(chr(PAD_CHAR)) + ext_ # short entry name # if LFN was detected, the record is considered as single SFN record only if DIR_NTRes == 0x18 (LDIR_DIR_NTRES) # if LFN was not detected, the record cannot be part of the LFN, no matter the value of DIR_NTRes if not args.long_name_support or obj_['DIR_NTRes'] == Entry.LDIR_DIR_NTRES: return obj_name_ full_name = {} for pos in range(entry_position_ - 1, -1, -1): # loop from the current entry back to the start obj_address_: int = FATDefaults.ENTRY_SIZE * pos entry_bytes_: bytes = directory_bytes_[obj_address_: obj_address_ + FATDefaults.ENTRY_SIZE] struct_ = Entry.parse_entry_long(entry_bytes_, lfn_checksum_) if len(struct_.items()) > 0: full_name[struct_['order']] = build_file_name(struct_['name1'], struct_['name2'], struct_['name3']) if struct_['is_last']: break return ''.join(map(lambda x: x[1], sorted(full_name.items()))) or obj_name_ def traverse_folder_tree(directory_bytes_: bytes, name: str, state_: BootSectorState, fat_: FAT, binary_array_: bytes) -> None: os.makedirs(name) assert len(directory_bytes_) % FATDefaults.ENTRY_SIZE == 0 entries_count_: int = len(directory_bytes_) // FATDefaults.ENTRY_SIZE for i in range(entries_count_): obj_address_: int = FATDefaults.ENTRY_SIZE * i try: obj_: dict = Entry.ENTRY_FORMAT_SHORT_NAME.parse( directory_bytes_[obj_address_: obj_address_ + FATDefaults.ENTRY_SIZE]) except (construct.core.ConstError, UnicodeDecodeError): args.long_name_support = True continue if obj_['DIR_Attr'] == 0: # empty entry continue obj_name_: str = get_obj_name(obj_, directory_bytes_, entry_position_=i, lfn_checksum_=lfn_checksum(obj_['DIR_Name'] + obj_['DIR_Name_ext'])) if obj_['DIR_Attr'] == Entry.ATTR_ARCHIVE: content_ = b'' if obj_['DIR_FileSize'] > 0: content_ = fat_.get_chained_content(cluster_id_=Entry.get_cluster_id(obj_), size=obj_['DIR_FileSize']) with open(os.path.join(name, obj_name_), 'wb') as new_file: new_file.write(content_) elif obj_['DIR_Attr'] == Entry.ATTR_DIRECTORY: # avoid creating symlinks to itself and parent folder if obj_name_ in ('.', '..'): continue child_directory_bytes_ = fat_.get_chained_content(cluster_id_=obj_['DIR_FstClusLO']) traverse_folder_tree(directory_bytes_=child_directory_bytes_, name=os.path.join(name, obj_name_), state_=state_, fat_=fat_, binary_array_=binary_array_) def remove_wear_levelling_if_exists(fs_: bytes) -> bytes: """ Detection of the wear levelling layer is performed in two steps: 1) check if the first sector is a valid boot sector 2) check if the size defined in the boot sector is the same as the partition size: - if it is, there is no wear levelling layer - otherwise, we need to remove wl for further processing """ try: boot_sector__ = BootSector() boot_sector__.parse_boot_sector(fs_) if boot_sector__.boot_sector_state.size == len(fs_): return fs_ except construct.core.ConstError: pass plain_fs: bytes = remove_wl(fs_) return plain_fs if __name__ == '__main__': desc = 'Tool for parsing fatfs image and extracting directory structure on host.' argument_parser: argparse.ArgumentParser = argparse.ArgumentParser(description=desc) argument_parser.add_argument('input_image', help='Path to the image that will be parsed and extracted.') argument_parser.add_argument('--long-name-support', action='store_true', help=argparse.SUPPRESS) # ensures backward compatibility argument_parser.add_argument('--wear-leveling', action='store_true', help=argparse.SUPPRESS) argument_parser.add_argument('--wl-layer', choices=['detect', 'enabled', 'disabled'], default=None, help="If detection doesn't work correctly, " 'you can force analyzer to or not to assume WL.') args = argument_parser.parse_args() # if wear levelling is detected or user explicitly sets the parameter `--wl_layer enabled` # the partition with wear levelling is transformed to partition without WL for convenient parsing # in some cases the partitions with and without wear levelling can be 100% equivalent # and only user can break this tie by explicitly setting # the parameter --wl-layer to enabled, respectively disabled if args.wear_leveling and args.wl_layer: raise NotImplementedError('Argument --wear-leveling cannot be combined with --wl-layer!') if args.wear_leveling: args.wl_layer = 'enabled' args.wl_layer = args.wl_layer or 'detect' fs = read_filesystem(args.input_image) # An algorithm for removing wear levelling: # 1. find an remove dummy sector: # a) dummy sector is at the position defined by the number of records in the state sector # b) dummy may not be placed in state nor cfg sectors # c) first (boot) sector position (boot_s_pos) is calculated using value of move count # boot_s_pos = - mc # 2. remove state sectors (trivial) # 3. remove cfg sector (trivial) # 4. valid fs is then old_fs[-mc:] + old_fs[:-mc] if args.wl_layer == 'enabled': fs = remove_wl(fs) elif args.wl_layer != 'disabled': # wear levelling is removed to enable parsing using common algorithm fs = remove_wear_levelling_if_exists(fs) boot_sector_ = BootSector() boot_sector_.parse_boot_sector(fs) fat = FAT(boot_sector_.boot_sector_state, init_=False) boot_dir_start_ = boot_sector_.boot_sector_state.root_directory_start boot_dir_sectors = boot_sector_.boot_sector_state.root_dir_sectors_cnt full_ = fs[boot_dir_start_: boot_dir_start_ + boot_dir_sectors * boot_sector_.boot_sector_state.sector_size] traverse_folder_tree(full_, boot_sector_.boot_sector_state.volume_label.rstrip(chr(PAD_CHAR)), boot_sector_.boot_sector_state, fat, fs)