Android Boot Image: Python parsing library

File extension

img

KS implementation details

License: CC0-1.0

This page hosts a formal specification of Android Boot Image 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 = AndroidImg.from_file("path/to/local/file.img")

Or parse structure from a bytes:

from kaitaistruct import KaitaiStream, BytesIO

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

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

data.base # => base loading address

Python source code to parse Android Boot Image

android_img.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


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 AndroidImg(KaitaiStruct):
    """
    .. seealso::
       Source - https://source.android.com/devices/bootloader/boot-image-header
    """
    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(8)
        if not self.magic == b"\x41\x4E\x44\x52\x4F\x49\x44\x21":
            raise kaitaistruct.ValidationNotEqualError(b"\x41\x4E\x44\x52\x4F\x49\x44\x21", self.magic, self._io, u"/seq/0")
        self.kernel = AndroidImg.Load(self._io, self, self._root)
        self.ramdisk = AndroidImg.Load(self._io, self, self._root)
        self.second = AndroidImg.Load(self._io, self, self._root)
        self.tags_load = self._io.read_u4le()
        self.page_size = self._io.read_u4le()
        self.header_version = self._io.read_u4le()
        self.os_version = AndroidImg.OsVersion(self._io, self, self._root)
        self.name = (KaitaiStream.bytes_terminate(self._io.read_bytes(16), 0, False)).decode(u"ASCII")
        self.cmdline = (KaitaiStream.bytes_terminate(self._io.read_bytes(512), 0, False)).decode(u"ASCII")
        self.sha = self._io.read_bytes(32)
        self.extra_cmdline = (KaitaiStream.bytes_terminate(self._io.read_bytes(1024), 0, False)).decode(u"ASCII")
        if self.header_version > 0:
            self.recovery_dtbo = AndroidImg.SizeOffset(self._io, self, self._root)

        if self.header_version > 0:
            self.boot_header_size = self._io.read_u4le()

        if self.header_version > 1:
            self.dtb = AndroidImg.LoadLong(self._io, self, self._root)


    class Load(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.size = self._io.read_u4le()
            self.addr = self._io.read_u4le()


    class LoadLong(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.size = self._io.read_u4le()
            self.addr = self._io.read_u8le()


    class SizeOffset(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.size = self._io.read_u4le()
            self.offset = self._io.read_u8le()


    class OsVersion(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.version = self._io.read_u4le()

        @property
        def month(self):
            if hasattr(self, '_m_month'):
                return self._m_month if hasattr(self, '_m_month') else None

            self._m_month = (self.version & 15)
            return self._m_month if hasattr(self, '_m_month') else None

        @property
        def patch(self):
            if hasattr(self, '_m_patch'):
                return self._m_patch if hasattr(self, '_m_patch') else None

            self._m_patch = ((self.version >> 11) & 127)
            return self._m_patch if hasattr(self, '_m_patch') else None

        @property
        def year(self):
            if hasattr(self, '_m_year'):
                return self._m_year if hasattr(self, '_m_year') else None

            self._m_year = (((self.version >> 4) & 127) + 2000)
            return self._m_year if hasattr(self, '_m_year') else None

        @property
        def major(self):
            if hasattr(self, '_m_major'):
                return self._m_major if hasattr(self, '_m_major') else None

            self._m_major = ((self.version >> 25) & 127)
            return self._m_major if hasattr(self, '_m_major') else None

        @property
        def minor(self):
            if hasattr(self, '_m_minor'):
                return self._m_minor if hasattr(self, '_m_minor') else None

            self._m_minor = ((self.version >> 18) & 127)
            return self._m_minor if hasattr(self, '_m_minor') else None


    @property
    def kernel_img(self):
        if hasattr(self, '_m_kernel_img'):
            return self._m_kernel_img if hasattr(self, '_m_kernel_img') else None

        _pos = self._io.pos()
        self._io.seek(self.page_size)
        self._m_kernel_img = self._io.read_bytes(self.kernel.size)
        self._io.seek(_pos)
        return self._m_kernel_img if hasattr(self, '_m_kernel_img') else None

    @property
    def tags_offset(self):
        """tags offset from base."""
        if hasattr(self, '_m_tags_offset'):
            return self._m_tags_offset if hasattr(self, '_m_tags_offset') else None

        self._m_tags_offset = (self.tags_load - self.base)
        return self._m_tags_offset if hasattr(self, '_m_tags_offset') else None

    @property
    def ramdisk_offset(self):
        """ramdisk offset from base."""
        if hasattr(self, '_m_ramdisk_offset'):
            return self._m_ramdisk_offset if hasattr(self, '_m_ramdisk_offset') else None

        self._m_ramdisk_offset = ((self.ramdisk.addr - self.base) if self.ramdisk.addr > 0 else 0)
        return self._m_ramdisk_offset if hasattr(self, '_m_ramdisk_offset') else None

    @property
    def second_offset(self):
        """2nd bootloader offset from base."""
        if hasattr(self, '_m_second_offset'):
            return self._m_second_offset if hasattr(self, '_m_second_offset') else None

        self._m_second_offset = ((self.second.addr - self.base) if self.second.addr > 0 else 0)
        return self._m_second_offset if hasattr(self, '_m_second_offset') else None

    @property
    def kernel_offset(self):
        """kernel offset from base."""
        if hasattr(self, '_m_kernel_offset'):
            return self._m_kernel_offset if hasattr(self, '_m_kernel_offset') else None

        self._m_kernel_offset = (self.kernel.addr - self.base)
        return self._m_kernel_offset if hasattr(self, '_m_kernel_offset') else None

    @property
    def dtb_offset(self):
        """dtb offset from base."""
        if hasattr(self, '_m_dtb_offset'):
            return self._m_dtb_offset if hasattr(self, '_m_dtb_offset') else None

        if self.header_version > 1:
            self._m_dtb_offset = ((self.dtb.addr - self.base) if self.dtb.addr > 0 else 0)

        return self._m_dtb_offset if hasattr(self, '_m_dtb_offset') else None

    @property
    def dtb_img(self):
        if hasattr(self, '_m_dtb_img'):
            return self._m_dtb_img if hasattr(self, '_m_dtb_img') else None

        if  ((self.header_version > 1) and (self.dtb.size > 0)) :
            _pos = self._io.pos()
            self._io.seek((((((((self.page_size + self.kernel.size) + self.ramdisk.size) + self.second.size) + self.recovery_dtbo.size) + self.page_size) - 1) // self.page_size * self.page_size))
            self._m_dtb_img = self._io.read_bytes(self.dtb.size)
            self._io.seek(_pos)

        return self._m_dtb_img if hasattr(self, '_m_dtb_img') else None

    @property
    def ramdisk_img(self):
        if hasattr(self, '_m_ramdisk_img'):
            return self._m_ramdisk_img if hasattr(self, '_m_ramdisk_img') else None

        if self.ramdisk.size > 0:
            _pos = self._io.pos()
            self._io.seek(((((self.page_size + self.kernel.size) + self.page_size) - 1) // self.page_size * self.page_size))
            self._m_ramdisk_img = self._io.read_bytes(self.ramdisk.size)
            self._io.seek(_pos)

        return self._m_ramdisk_img if hasattr(self, '_m_ramdisk_img') else None

    @property
    def recovery_dtbo_img(self):
        if hasattr(self, '_m_recovery_dtbo_img'):
            return self._m_recovery_dtbo_img if hasattr(self, '_m_recovery_dtbo_img') else None

        if  ((self.header_version > 0) and (self.recovery_dtbo.size > 0)) :
            _pos = self._io.pos()
            self._io.seek(self.recovery_dtbo.offset)
            self._m_recovery_dtbo_img = self._io.read_bytes(self.recovery_dtbo.size)
            self._io.seek(_pos)

        return self._m_recovery_dtbo_img if hasattr(self, '_m_recovery_dtbo_img') else None

    @property
    def second_img(self):
        if hasattr(self, '_m_second_img'):
            return self._m_second_img if hasattr(self, '_m_second_img') else None

        if self.second.size > 0:
            _pos = self._io.pos()
            self._io.seek((((((self.page_size + self.kernel.size) + self.ramdisk.size) + self.page_size) - 1) // self.page_size * self.page_size))
            self._m_second_img = self._io.read_bytes(self.second.size)
            self._io.seek(_pos)

        return self._m_second_img if hasattr(self, '_m_second_img') else None

    @property
    def base(self):
        """base loading address."""
        if hasattr(self, '_m_base'):
            return self._m_base if hasattr(self, '_m_base') else None

        self._m_base = (self.kernel.addr - 32768)
        return self._m_base if hasattr(self, '_m_base') else None