Linux Unified Key Setup: Python parsing library

Linux Unified Key Setup (LUKS) is a format specification for storing disk encryption parameters and up to 8 user keys (which can unlock the master key).

KS implementation details

License: CC0-1.0

References

This page hosts a formal specification of Linux Unified Key Setup 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 = Luks.from_file("path/to/local/file.Linux Unified Key Setup")

Or parse structure from a bytes:

from kaitaistruct import KaitaiStream, BytesIO

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

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

data.partition_header # => get partition header

Python source code to parse Linux Unified Key Setup

luks.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 Luks(KaitaiStruct):
    """Linux Unified Key Setup (LUKS) is a format specification for storing disk
    encryption parameters and up to 8 user keys (which can unlock the master key).
    
    .. seealso::
       Source - https://gitlab.com/cryptsetup/cryptsetup/wikis/LUKS-standard/on-disk-format.pdf
    """
    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.partition_header = Luks.PartitionHeader(self._io, self, self._root)

    class PartitionHeader(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(6)
            if not self.magic == b"\x4C\x55\x4B\x53\xBA\xBE":
                raise kaitaistruct.ValidationNotEqualError(b"\x4C\x55\x4B\x53\xBA\xBE", self.magic, self._io, u"/types/partition_header/seq/0")
            self.version = self._io.read_bytes(2)
            if not self.version == b"\x00\x01":
                raise kaitaistruct.ValidationNotEqualError(b"\x00\x01", self.version, self._io, u"/types/partition_header/seq/1")
            self.cipher_name_specification = (self._io.read_bytes(32)).decode(u"ASCII")
            self.cipher_mode_specification = (self._io.read_bytes(32)).decode(u"ASCII")
            self.hash_specification = (self._io.read_bytes(32)).decode(u"ASCII")
            self.payload_offset = self._io.read_u4be()
            self.number_of_key_bytes = self._io.read_u4be()
            self.master_key_checksum = self._io.read_bytes(20)
            self.master_key_salt_parameter = self._io.read_bytes(32)
            self.master_key_iterations_parameter = self._io.read_u4be()
            self.uuid = (self._io.read_bytes(40)).decode(u"ASCII")
            self.key_slots = [None] * (8)
            for i in range(8):
                self.key_slots[i] = Luks.PartitionHeader.KeySlot(self._io, self, self._root)


        class KeySlot(KaitaiStruct):

            class KeySlotStates(Enum):
                disabled_key_slot = 57005
                enabled_key_slot = 11301363
            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.state_of_key_slot = KaitaiStream.resolve_enum(Luks.PartitionHeader.KeySlot.KeySlotStates, self._io.read_u4be())
                self.iteration_parameter = self._io.read_u4be()
                self.salt_parameter = self._io.read_bytes(32)
                self.start_sector_of_key_material = self._io.read_u4be()
                self.number_of_anti_forensic_stripes = self._io.read_u4be()

            @property
            def key_material(self):
                if hasattr(self, '_m_key_material'):
                    return self._m_key_material if hasattr(self, '_m_key_material') else None

                _pos = self._io.pos()
                self._io.seek((self.start_sector_of_key_material * 512))
                self._m_key_material = self._io.read_bytes((self._parent.number_of_key_bytes * self.number_of_anti_forensic_stripes))
                self._io.seek(_pos)
                return self._m_key_material if hasattr(self, '_m_key_material') else None



    @property
    def payload(self):
        if hasattr(self, '_m_payload'):
            return self._m_payload if hasattr(self, '_m_payload') else None

        _pos = self._io.pos()
        self._io.seek((self.partition_header.payload_offset * 512))
        self._m_payload = self._io.read_bytes_full()
        self._io.seek(_pos)
        return self._m_payload if hasattr(self, '_m_payload') else None