DOS MZ file format is a traditional format for executables in MS-DOS environment. Many modern formats (i.e. Windows PE) still maintain compatibility stub with this format.
As opposed to .com file format (which basically sports one 64K code segment of raw CPU instructions), DOS MZ .exe file format allowed more flexible memory management, loading of larger programs and added support for relocations.
This page hosts a formal specification of DOS MZ executable using Kaitai Struct. This specification can be automatically translated into a variety of programming languages to get a parsing 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 kaitaistructParse a local file and get structure in memory:
data = DosMz.from_file("path/to/local/file.exe")
Or parse structure from a bytes:
from kaitaistruct import KaitaiStream, BytesIO
raw = b"\x00\x01\x02..."
data = DosMz(KaitaiStream(BytesIO(raw)))
After that, one can get various attributes from the structure by invoking getter methods like:
data.header # => get header
# This is a generated file! Please edit source .ksy file and use kaitai-struct-compiler to rebuild
import kaitaistruct
from kaitaistruct import KaitaiStruct, KaitaiStream, BytesIO
if getattr(kaitaistruct, 'API_VERSION', (0, 9)) < (0, 9):
raise Exception("Incompatible Kaitai Struct Python API: 0.9 or later is required, but you have %s" % (kaitaistruct.__version__))
class DosMz(KaitaiStruct):
"""DOS MZ file format is a traditional format for executables in MS-DOS
environment. Many modern formats (i.e. Windows PE) still maintain
compatibility stub with this format.
As opposed to .com file format (which basically sports one 64K code
segment of raw CPU instructions), DOS MZ .exe file format allowed
more flexible memory management, loading of larger programs and
added support for relocations.
.. seealso::
Source - http://www.delorie.com/djgpp/doc/exe/
"""
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.header = DosMz.ExeHeader(self._io, self, self._root)
self.body = self._io.read_bytes(self.header.len_body)
class ExeHeader(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.mz = DosMz.MzHeader(self._io, self, self._root)
self.rest_of_header = self._io.read_bytes((self.mz.len_header - 28))
@property
def len_body(self):
if hasattr(self, '_m_len_body'):
return self._m_len_body
self._m_len_body = (((self.mz.num_pages * 512) if self.mz.last_page_extra_bytes == 0 else (((self.mz.num_pages - 1) * 512) + self.mz.last_page_extra_bytes)) - self.mz.len_header)
return getattr(self, '_m_len_body', None)
class MzHeader(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.magic = (self._io.read_bytes(2)).decode(u"ASCII")
if not ((self.magic == u"MZ") or (self.magic == u"ZM")) :
raise kaitaistruct.ValidationNotAnyOfError(self.magic, self._io, u"/types/mz_header/seq/0")
self.last_page_extra_bytes = self._io.read_u2le()
self.num_pages = self._io.read_u2le()
self.num_relocations = self._io.read_u2le()
self.header_size = self._io.read_u2le()
self.min_allocation = self._io.read_u2le()
self.max_allocation = self._io.read_u2le()
self.initial_ss = self._io.read_u2le()
self.initial_sp = self._io.read_u2le()
self.checksum = self._io.read_u2le()
self.initial_ip = self._io.read_u2le()
self.initial_cs = self._io.read_u2le()
self.ofs_relocations = self._io.read_u2le()
self.overlay_id = self._io.read_u2le()
@property
def len_header(self):
if hasattr(self, '_m_len_header'):
return self._m_len_header
self._m_len_header = (self.header_size * 16)
return getattr(self, '_m_len_header', None)
class Relocation(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.ofs = self._io.read_u2le()
self.seg = self._io.read_u2le()
@property
def relocations(self):
if hasattr(self, '_m_relocations'):
return self._m_relocations
if self.header.mz.ofs_relocations != 0:
io = self.header._io
_pos = io.pos()
io.seek(self.header.mz.ofs_relocations)
self._m_relocations = []
for i in range(self.header.mz.num_relocations):
self._m_relocations.append(DosMz.Relocation(io, self, self._root))
io.seek(_pos)
return getattr(self, '_m_relocations', None)