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.
All parsing code for Ruby generated by Kaitai Struct depends on the Ruby runtime library. You have to install it before you can parse data.
The Ruby runtime library can be installed from RubyGems:
gem install kaitai-structParse a local file and get structure in memory:
data = AndroidImg.from_file("path/to/local/file.img")
Or parse structure from a string of bytes:
bytes = "\x00\x01\x02..."
data = AndroidImg.new(Kaitai::Struct::Stream.new(bytes))
After that, one can get various attributes from the structure by invoking getter methods like:
data.base # => base loading address
# This is a generated file! Please edit source .ksy file and use kaitai-struct-compiler to rebuild
require 'kaitai/struct/struct'
unless Gem::Version.new(Kaitai::Struct::VERSION) >= Gem::Version.new('0.9')
raise "Incompatible Kaitai Struct Ruby API: 0.9 or later is required, but you have #{Kaitai::Struct::VERSION}"
end
##
# @see https://source.android.com/docs/core/architecture/bootloader/boot-image-header Source
class AndroidImg < Kaitai::Struct::Struct
def initialize(_io, _parent = nil, _root = self)
super(_io, _parent, _root)
_read
end
def _read
@magic = @_io.read_bytes(8)
raise Kaitai::Struct::ValidationNotEqualError.new([65, 78, 68, 82, 79, 73, 68, 33].pack('C*'), magic, _io, "/seq/0") if not magic == [65, 78, 68, 82, 79, 73, 68, 33].pack('C*')
@kernel = Load.new(@_io, self, @_root)
@ramdisk = Load.new(@_io, self, @_root)
@second = Load.new(@_io, self, @_root)
@tags_load = @_io.read_u4le
@page_size = @_io.read_u4le
@header_version = @_io.read_u4le
@os_version = OsVersion.new(@_io, self, @_root)
@name = (Kaitai::Struct::Stream::bytes_terminate(@_io.read_bytes(16), 0, false)).force_encoding("ASCII")
@cmdline = (Kaitai::Struct::Stream::bytes_terminate(@_io.read_bytes(512), 0, false)).force_encoding("ASCII")
@sha = @_io.read_bytes(32)
@extra_cmdline = (Kaitai::Struct::Stream::bytes_terminate(@_io.read_bytes(1024), 0, false)).force_encoding("ASCII")
if header_version > 0
@recovery_dtbo = SizeOffset.new(@_io, self, @_root)
end
if header_version > 0
@boot_header_size = @_io.read_u4le
end
if header_version > 1
@dtb = LoadLong.new(@_io, self, @_root)
end
self
end
class Load < Kaitai::Struct::Struct
def initialize(_io, _parent = nil, _root = self)
super(_io, _parent, _root)
_read
end
def _read
@size = @_io.read_u4le
@addr = @_io.read_u4le
self
end
attr_reader :size
attr_reader :addr
end
class LoadLong < Kaitai::Struct::Struct
def initialize(_io, _parent = nil, _root = self)
super(_io, _parent, _root)
_read
end
def _read
@size = @_io.read_u4le
@addr = @_io.read_u8le
self
end
attr_reader :size
attr_reader :addr
end
class SizeOffset < Kaitai::Struct::Struct
def initialize(_io, _parent = nil, _root = self)
super(_io, _parent, _root)
_read
end
def _read
@size = @_io.read_u4le
@offset = @_io.read_u8le
self
end
attr_reader :size
attr_reader :offset
end
class OsVersion < Kaitai::Struct::Struct
def initialize(_io, _parent = nil, _root = self)
super(_io, _parent, _root)
_read
end
def _read
@version = @_io.read_u4le
self
end
def month
return @month unless @month.nil?
@month = (version & 15)
@month
end
def patch
return @patch unless @patch.nil?
@patch = ((version >> 11) & 127)
@patch
end
def year
return @year unless @year.nil?
@year = (((version >> 4) & 127) + 2000)
@year
end
def major
return @major unless @major.nil?
@major = ((version >> 25) & 127)
@major
end
def minor
return @minor unless @minor.nil?
@minor = ((version >> 18) & 127)
@minor
end
attr_reader :version
end
def kernel_img
return @kernel_img unless @kernel_img.nil?
_pos = @_io.pos
@_io.seek(page_size)
@kernel_img = @_io.read_bytes(kernel.size)
@_io.seek(_pos)
@kernel_img
end
##
# tags offset from base
def tags_offset
return @tags_offset unless @tags_offset.nil?
@tags_offset = (tags_load - base)
@tags_offset
end
##
# ramdisk offset from base
def ramdisk_offset
return @ramdisk_offset unless @ramdisk_offset.nil?
@ramdisk_offset = (ramdisk.addr > 0 ? (ramdisk.addr - base) : 0)
@ramdisk_offset
end
##
# 2nd bootloader offset from base
def second_offset
return @second_offset unless @second_offset.nil?
@second_offset = (second.addr > 0 ? (second.addr - base) : 0)
@second_offset
end
##
# kernel offset from base
def kernel_offset
return @kernel_offset unless @kernel_offset.nil?
@kernel_offset = (kernel.addr - base)
@kernel_offset
end
##
# dtb offset from base
def dtb_offset
return @dtb_offset unless @dtb_offset.nil?
if header_version > 1
@dtb_offset = (dtb.addr > 0 ? (dtb.addr - base) : 0)
end
@dtb_offset
end
def dtb_img
return @dtb_img unless @dtb_img.nil?
if ((header_version > 1) && (dtb.size > 0))
_pos = @_io.pos
@_io.seek(((((((((page_size + kernel.size) + ramdisk.size) + second.size) + recovery_dtbo.size) + page_size) - 1) / page_size) * page_size))
@dtb_img = @_io.read_bytes(dtb.size)
@_io.seek(_pos)
end
@dtb_img
end
def ramdisk_img
return @ramdisk_img unless @ramdisk_img.nil?
if ramdisk.size > 0
_pos = @_io.pos
@_io.seek((((((page_size + kernel.size) + page_size) - 1) / page_size) * page_size))
@ramdisk_img = @_io.read_bytes(ramdisk.size)
@_io.seek(_pos)
end
@ramdisk_img
end
def recovery_dtbo_img
return @recovery_dtbo_img unless @recovery_dtbo_img.nil?
if ((header_version > 0) && (recovery_dtbo.size > 0))
_pos = @_io.pos
@_io.seek(recovery_dtbo.offset)
@recovery_dtbo_img = @_io.read_bytes(recovery_dtbo.size)
@_io.seek(_pos)
end
@recovery_dtbo_img
end
def second_img
return @second_img unless @second_img.nil?
if second.size > 0
_pos = @_io.pos
@_io.seek(((((((page_size + kernel.size) + ramdisk.size) + page_size) - 1) / page_size) * page_size))
@second_img = @_io.read_bytes(second.size)
@_io.seek(_pos)
end
@second_img
end
##
# base loading address
def base
return @base unless @base.nil?
@base = (kernel.addr - 32768)
@base
end
attr_reader :magic
attr_reader :kernel
attr_reader :ramdisk
attr_reader :second
attr_reader :tags_load
attr_reader :page_size
attr_reader :header_version
attr_reader :os_version
attr_reader :name
attr_reader :cmdline
attr_reader :sha
attr_reader :extra_cmdline
attr_reader :recovery_dtbo
attr_reader :boot_header_size
attr_reader :dtb
end