ext2 filesystem: Python parsing library

This page hosts a formal specification of ext2 filesystem using Kaitai Struct. This specification can be automatically translated into a variety of programming languages to get a parsing library.

Usage

Runtime library

All parsing code for Python generated by Kaitai Struct depends on the Python runtime library. You have to install it before you can parse data.

The Python runtime library can be installed from PyPI:

python3 -m pip install kaitaistruct

Code

Parse a local file and get structure in memory:

data = Ext2.from_file("path/to/local/file.ext2 filesystem")

Or parse structure from a bytes:

from kaitaistruct import KaitaiStream, BytesIO

raw = b"\x00\x01\x02..."
data = Ext2(KaitaiStream(BytesIO(raw)))

After that, one can get various attributes from the structure by invoking getter methods like:

data.bg1 # => get bg1

Python source code to parse ext2 filesystem

ext2.py

# This is a generated file! Please edit source .ksy file and use kaitai-struct-compiler to rebuild

from pkg_resources import parse_version
import kaitaistruct
from kaitaistruct import KaitaiStruct, KaitaiStream, BytesIO
from enum import Enum


if parse_version(kaitaistruct.__version__) < parse_version('0.9'):
    raise Exception("Incompatible Kaitai Struct Python API: 0.9 or later is required, but you have %s" % (kaitaistruct.__version__))

class Ext2(KaitaiStruct):
    def __init__(self, _io, _parent=None, _root=None):
        self._io = _io
        self._parent = _parent
        self._root = _root if _root else self
        self._read()

    def _read(self):
        pass

    class SuperBlockStruct(KaitaiStruct):

        class StateEnum(Enum):
            valid_fs = 1
            error_fs = 2

        class ErrorsEnum(Enum):
            act_continue = 1
            act_ro = 2
            act_panic = 3
        def __init__(self, _io, _parent=None, _root=None):
            self._io = _io
            self._parent = _parent
            self._root = _root if _root else self
            self._read()

        def _read(self):
            self.inodes_count = self._io.read_u4le()
            self.blocks_count = self._io.read_u4le()
            self.r_blocks_count = self._io.read_u4le()
            self.free_blocks_count = self._io.read_u4le()
            self.free_inodes_count = self._io.read_u4le()
            self.first_data_block = self._io.read_u4le()
            self.log_block_size = self._io.read_u4le()
            self.log_frag_size = self._io.read_u4le()
            self.blocks_per_group = self._io.read_u4le()
            self.frags_per_group = self._io.read_u4le()
            self.inodes_per_group = self._io.read_u4le()
            self.mtime = self._io.read_u4le()
            self.wtime = self._io.read_u4le()
            self.mnt_count = self._io.read_u2le()
            self.max_mnt_count = self._io.read_u2le()
            self.magic = self._io.read_bytes(2)
            if not self.magic == b"\x53\xEF":
                raise kaitaistruct.ValidationNotEqualError(b"\x53\xEF", self.magic, self._io, u"/types/super_block_struct/seq/15")
            self.state = KaitaiStream.resolve_enum(Ext2.SuperBlockStruct.StateEnum, self._io.read_u2le())
            self.errors = KaitaiStream.resolve_enum(Ext2.SuperBlockStruct.ErrorsEnum, self._io.read_u2le())
            self.minor_rev_level = self._io.read_u2le()
            self.lastcheck = self._io.read_u4le()
            self.checkinterval = self._io.read_u4le()
            self.creator_os = self._io.read_u4le()
            self.rev_level = self._io.read_u4le()
            self.def_resuid = self._io.read_u2le()
            self.def_resgid = self._io.read_u2le()
            self.first_ino = self._io.read_u4le()
            self.inode_size = self._io.read_u2le()
            self.block_group_nr = self._io.read_u2le()
            self.feature_compat = self._io.read_u4le()
            self.feature_incompat = self._io.read_u4le()
            self.feature_ro_compat = self._io.read_u4le()
            self.uuid = self._io.read_bytes(16)
            self.volume_name = self._io.read_bytes(16)
            self.last_mounted = self._io.read_bytes(64)
            self.algo_bitmap = self._io.read_u4le()
            self.prealloc_blocks = self._io.read_u1()
            self.prealloc_dir_blocks = self._io.read_u1()
            self.padding1 = self._io.read_bytes(2)
            self.journal_uuid = self._io.read_bytes(16)
            self.journal_inum = self._io.read_u4le()
            self.journal_dev = self._io.read_u4le()
            self.last_orphan = self._io.read_u4le()
            self.hash_seed = [None] * (4)
            for i in range(4):
                self.hash_seed[i] = self._io.read_u4le()

            self.def_hash_version = self._io.read_u1()

        @property
        def block_size(self):
            if hasattr(self, '_m_block_size'):
                return self._m_block_size if hasattr(self, '_m_block_size') else None

            self._m_block_size = (1024 << self.log_block_size)
            return self._m_block_size if hasattr(self, '_m_block_size') else None

        @property
        def block_group_count(self):
            if hasattr(self, '_m_block_group_count'):
                return self._m_block_group_count if hasattr(self, '_m_block_group_count') else None

            self._m_block_group_count = self.blocks_count // self.blocks_per_group
            return self._m_block_group_count if hasattr(self, '_m_block_group_count') else None


    class DirEntry(KaitaiStruct):

        class FileTypeEnum(Enum):
            unknown = 0
            reg_file = 1
            dir = 2
            chrdev = 3
            blkdev = 4
            fifo = 5
            sock = 6
            symlink = 7
        def __init__(self, _io, _parent=None, _root=None):
            self._io = _io
            self._parent = _parent
            self._root = _root if _root else self
            self._read()

        def _read(self):
            self.inode_ptr = self._io.read_u4le()
            self.rec_len = self._io.read_u2le()
            self.name_len = self._io.read_u1()
            self.file_type = KaitaiStream.resolve_enum(Ext2.DirEntry.FileTypeEnum, self._io.read_u1())
            self.name = (self._io.read_bytes(self.name_len)).decode(u"UTF-8")
            self.padding = self._io.read_bytes(((self.rec_len - self.name_len) - 8))

        @property
        def inode(self):
            if hasattr(self, '_m_inode'):
                return self._m_inode if hasattr(self, '_m_inode') else None

            self._m_inode = self._root.bg1.block_groups[(self.inode_ptr - 1) // self._root.bg1.super_block.inodes_per_group].inodes[((self.inode_ptr - 1) % self._root.bg1.super_block.inodes_per_group)]
            return self._m_inode if hasattr(self, '_m_inode') else None


    class Inode(KaitaiStruct):
        def __init__(self, _io, _parent=None, _root=None):
            self._io = _io
            self._parent = _parent
            self._root = _root if _root else self
            self._read()

        def _read(self):
            self.mode = self._io.read_u2le()
            self.uid = self._io.read_u2le()
            self.size = self._io.read_u4le()
            self.atime = self._io.read_u4le()
            self.ctime = self._io.read_u4le()
            self.mtime = self._io.read_u4le()
            self.dtime = self._io.read_u4le()
            self.gid = self._io.read_u2le()
            self.links_count = self._io.read_u2le()
            self.blocks = self._io.read_u4le()
            self.flags = self._io.read_u4le()
            self.osd1 = self._io.read_u4le()
            self.block = [None] * (15)
            for i in range(15):
                self.block[i] = Ext2.BlockPtr(self._io, self, self._root)

            self.generation = self._io.read_u4le()
            self.file_acl = self._io.read_u4le()
            self.dir_acl = self._io.read_u4le()
            self.faddr = self._io.read_u4le()
            self.osd2 = self._io.read_bytes(12)

        @property
        def as_dir(self):
            if hasattr(self, '_m_as_dir'):
                return self._m_as_dir if hasattr(self, '_m_as_dir') else None

            io = self.block[0].body._io
            _pos = io.pos()
            io.seek(0)
            self._m_as_dir = Ext2.Dir(io, self, self._root)
            io.seek(_pos)
            return self._m_as_dir if hasattr(self, '_m_as_dir') else None


    class BlockPtr(KaitaiStruct):
        def __init__(self, _io, _parent=None, _root=None):
            self._io = _io
            self._parent = _parent
            self._root = _root if _root else self
            self._read()

        def _read(self):
            self.ptr = self._io.read_u4le()

        @property
        def body(self):
            if hasattr(self, '_m_body'):
                return self._m_body if hasattr(self, '_m_body') else None

            _pos = self._io.pos()
            self._io.seek((self.ptr * self._root.bg1.super_block.block_size))
            self._raw__m_body = self._io.read_bytes(self._root.bg1.super_block.block_size)
            _io__raw__m_body = KaitaiStream(BytesIO(self._raw__m_body))
            self._m_body = Ext2.RawBlock(_io__raw__m_body, self, self._root)
            self._io.seek(_pos)
            return self._m_body if hasattr(self, '_m_body') else None


    class Dir(KaitaiStruct):
        def __init__(self, _io, _parent=None, _root=None):
            self._io = _io
            self._parent = _parent
            self._root = _root if _root else self
            self._read()

        def _read(self):
            self.entries = []
            i = 0
            while not self._io.is_eof():
                self.entries.append(Ext2.DirEntry(self._io, self, self._root))
                i += 1



    class BlockGroup(KaitaiStruct):
        def __init__(self, _io, _parent=None, _root=None):
            self._io = _io
            self._parent = _parent
            self._root = _root if _root else self
            self._read()

        def _read(self):
            self._raw_super_block = self._io.read_bytes(1024)
            _io__raw_super_block = KaitaiStream(BytesIO(self._raw_super_block))
            self.super_block = Ext2.SuperBlockStruct(_io__raw_super_block, self, self._root)
            self.block_groups = [None] * (self.super_block.block_group_count)
            for i in range(self.super_block.block_group_count):
                self.block_groups[i] = Ext2.Bgd(self._io, self, self._root)



    class Bgd(KaitaiStruct):
        def __init__(self, _io, _parent=None, _root=None):
            self._io = _io
            self._parent = _parent
            self._root = _root if _root else self
            self._read()

        def _read(self):
            self.block_bitmap_block = self._io.read_u4le()
            self.inode_bitmap_block = self._io.read_u4le()
            self.inode_table_block = self._io.read_u4le()
            self.free_blocks_count = self._io.read_u2le()
            self.free_inodes_count = self._io.read_u2le()
            self.used_dirs_count = self._io.read_u2le()
            self.pad_reserved = self._io.read_bytes((2 + 12))

        @property
        def block_bitmap(self):
            if hasattr(self, '_m_block_bitmap'):
                return self._m_block_bitmap if hasattr(self, '_m_block_bitmap') else None

            _pos = self._io.pos()
            self._io.seek((self.block_bitmap_block * self._root.bg1.super_block.block_size))
            self._m_block_bitmap = self._io.read_bytes(1024)
            self._io.seek(_pos)
            return self._m_block_bitmap if hasattr(self, '_m_block_bitmap') else None

        @property
        def inode_bitmap(self):
            if hasattr(self, '_m_inode_bitmap'):
                return self._m_inode_bitmap if hasattr(self, '_m_inode_bitmap') else None

            _pos = self._io.pos()
            self._io.seek((self.inode_bitmap_block * self._root.bg1.super_block.block_size))
            self._m_inode_bitmap = self._io.read_bytes(1024)
            self._io.seek(_pos)
            return self._m_inode_bitmap if hasattr(self, '_m_inode_bitmap') else None

        @property
        def inodes(self):
            if hasattr(self, '_m_inodes'):
                return self._m_inodes if hasattr(self, '_m_inodes') else None

            _pos = self._io.pos()
            self._io.seek((self.inode_table_block * self._root.bg1.super_block.block_size))
            self._m_inodes = [None] * (self._root.bg1.super_block.inodes_per_group)
            for i in range(self._root.bg1.super_block.inodes_per_group):
                self._m_inodes[i] = Ext2.Inode(self._io, self, self._root)

            self._io.seek(_pos)
            return self._m_inodes if hasattr(self, '_m_inodes') else None


    class RawBlock(KaitaiStruct):
        def __init__(self, _io, _parent=None, _root=None):
            self._io = _io
            self._parent = _parent
            self._root = _root if _root else self
            self._read()

        def _read(self):
            self.body = self._io.read_bytes(self._root.bg1.super_block.block_size)


    @property
    def bg1(self):
        if hasattr(self, '_m_bg1'):
            return self._m_bg1 if hasattr(self, '_m_bg1') else None

        _pos = self._io.pos()
        self._io.seek(1024)
        self._m_bg1 = Ext2.BlockGroup(self._io, self, self._root)
        self._io.seek(_pos)
        return self._m_bg1 if hasattr(self, '_m_bg1') else None

    @property
    def root_dir(self):
        if hasattr(self, '_m_root_dir'):
            return self._m_root_dir if hasattr(self, '_m_root_dir') else None

        self._m_root_dir = self.bg1.block_groups[0].inodes[1].as_dir
        return self._m_root_dir if hasattr(self, '_m_root_dir') else None