Class: MachO::MachOFile

Inherits:
Object
  • Object
show all
Defined in:
lib/macho/macho_file.rb

Overview

Represents a Mach-O file, which contains a header and load commands as well as binary executable instructions. Mach-O binaries are architecture specific.

See Also:

Instance Attribute Summary collapse

Class Method Summary collapse

Instance Method Summary collapse

Constructor Details

#initialize(filename) ⇒ MachOFile

TODO:

document all the exceptions propagated here

Creates a new FatFile from the given filename.

Parameters:

  • filename (String) —

    the Mach-O file to load from

Raises:

  • (ArgumentError) 


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# File 'lib/macho/macho_file.rb', line 28

def initialize(filename)
	raise ArgumentError.new("filename must be a String") unless filename.is_a? String

	@filename = filename
	@raw_data = open(@filename, "rb") { |f| f.read }
	@header = get_mach_header
	@load_commands = get_load_commands
end

Instance Attribute Details

#header ⇒ MachO::MachHeader, MachO::MachHeader64 (readonly)

Returns:



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# File 'lib/macho/macho_file.rb', line 10

def header
  @header
end

#load_commands ⇒ Array<MachO::LoadCommand> (readonly)

Returns an array of the file’s load commands.

Returns:



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# File 'lib/macho/macho_file.rb', line 13

def load_commands
  @load_commands
end

Class Method Details

.new_from_bin(bin) ⇒ MachO::MachOFile

Creates a new MachOFile instance from a binary string.

Parameters:

  • bin (String) —

    a binary string containing raw Mach-O data

Returns:



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# File 'lib/macho/macho_file.rb', line 18

def self.new_from_bin(bin)
	instance = allocate
	instance.initialize_from_bin(bin)

	instance
end

Instance Method Details

#bundle? ⇒ Boolean

Returns true if the Mach-O is of type ‘MH_BUNDLE`, false otherwise.

Returns:

  • (Boolean) —

    true if the Mach-O is of type ‘MH_BUNDLE`, false otherwise



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# File 'lib/macho/macho_file.rb', line 72

def bundle?
	header[:filetype] == MH_BUNDLE
end

#change_install_name(old_name, new_name) ⇒ void Also known as: change_dylib

TODO:

refactor

This method returns an undefined value.

Raises:



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# File 'lib/macho/macho_file.rb', line 259

def change_install_name(old_name, new_name)
	idx = linked_dylibs.index(old_name)
	raise DylibUnknownError.new(old_name) if idx.nil?

	# this is a bit of a hack - since there is a 1-1 ordered association
	# between linked_dylibs and command('LC_LOAD_DYLIB'), we can use
	# their indices interchangeably to avoid having to loop.
	dylib_cmd = command('LC_LOAD_DYLIB')[idx]

	if magic32?
		cmd_round = 4
	else
		cmd_round = 8
	end

	new_sizeofcmds = header[:sizeofcmds]
	old_install_name = old_name.dup
	new_install_name = new_name.dup

	old_pad = MachO.round(old_install_name.size, cmd_round) - old_install_name.size
	new_pad = MachO.round(new_install_name.size, cmd_round) - new_install_name.size

	old_install_name << "\x00" * old_pad
	new_install_name << "\x00" * new_pad

	new_size = DylibCommand.bytesize + new_install_name.size
	new_sizeofcmds += new_size - dylib_cmd.cmdsize

	low_fileoff = 2**64

	segments.each do |seg|
		sections(seg).each do |sect|
			if sect.size != 0 && !sect.flag?(S_ZEROFILL) &&
					!sect.flag?(S_THREAD_LOCAL_ZEROFILL) &&
					sect.offset < low_fileoff

				low_fileoff = sect.offset
			end
		end
	end

	if new_sizeofcmds + header.bytesize > low_fileoff
		raise HeaderPadError.new(@filename)
	end

	set_sizeofcmds(new_sizeofcmds)

	@raw_data[dylib_cmd.offset + 4, 4] = [new_size].pack("V")

	@raw_data.slice!(dylib_cmd.offset + dylib_cmd.name...dylib_cmd.offset + dylib_cmd.class.bytesize + old_install_name.size)

	@raw_data.insert(dylib_cmd.offset + dylib_cmd.name, new_install_name)

	null_pad = old_install_name.size - new_install_name.size

	if null_pad < 0
		@raw_data.slice!(new_sizeofcmds + header.bytesize, null_pad.abs)
	else
		@raw_data.insert(new_sizeofcmds + header.bytesize, "\x00" * null_pad)
	end

	header = get_mach_header
	load_commands = get_load_commands
end

#command(name) ⇒ Array<MachO::LoadCommand> Also known as: []

All load commands of a given name.

Examples:

file.command("LC_LOAD_DYLIB")
file["LC_LOAD_DYLIB"]

Returns:



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# File 'lib/macho/macho_file.rb', line 121

def command(name)
	load_commands.select { |lc| lc.to_s == name }
end

#cpusubtype ⇒ String

Returns a string representation of the Mach-O’s CPU subtype.

Returns:

  • (String) —

    a string representation of the Mach-O’s CPU subtype



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# File 'lib/macho/macho_file.rb', line 97

def cpusubtype
	CPU_SUBTYPES[header[:cpusubtype]]
end

#cputype ⇒ String

Returns a string representation of the Mach-O’s CPU type.

Returns:

  • (String) —

    a string representation of the Mach-O’s CPU type



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# File 'lib/macho/macho_file.rb', line 92

def cputype
	CPU_TYPES[header[:cputype]]
end

#dylib? ⇒ Boolean

Returns true if the Mach-O is of type ‘MH_DYLIB`, false otherwise.

Returns:

  • (Boolean) —

    true if the Mach-O is of type ‘MH_DYLIB`, false otherwise



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# File 'lib/macho/macho_file.rb', line 67

def dylib?
	header[:filetype] == MH_DYLIB
end

#dylib_id ⇒ String

The Mach-O’s dylib ID, or ‘nil` if not a dylib.

Examples:

file.dylib_id # => 'libBar.dylib'

Returns:

  • (String) —

    the Mach-O’s dylib ID



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# File 'lib/macho/macho_file.rb', line 142

def dylib_id
	if !dylib?
		return nil
	end

	dylib_id_cmd = command('LC_ID_DYLIB').first

	cmdsize = dylib_id_cmd.cmdsize
	offset = dylib_id_cmd.offset
	stroffset = dylib_id_cmd.name

	dylib_id = @raw_data.slice(offset + stroffset...offset + cmdsize).unpack("Z*").first

	dylib_id.delete("\x00")
end

#dylib_id=(new_id) ⇒ void

TODO:

refactor

This method returns an undefined value.

Changes the Mach-O’s dylib ID to ‘new_id`. Does nothing if not a dylib.

Examples:

file.dylib_id = "libFoo.dylib"


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# File 'lib/macho/macho_file.rb', line 163

def dylib_id=(new_id)
	if !new_id.is_a?(String)
		raise ArgumentError.new("argument must be a String")
	end

	if !dylib?
		return nil
	end

	if magic32?
		cmd_round = 4
	else
		cmd_round = 8
	end

	new_sizeofcmds = header[:sizeofcmds]
	dylib_id_cmd = command('LC_ID_DYLIB').first
	old_id = dylib_id
	new_id = new_id.dup

	new_pad = MachO.round(new_id.size, cmd_round) - new_id.size
	old_pad = MachO.round(old_id.size, cmd_round) - old_id.size

	# pad the old and new IDs with null bytes to meet command bounds
	old_id << "\x00" * old_pad
	new_id << "\x00" * new_pad

	# calculate the new size of the DylibCommand and sizeofcmds in MH
	new_size = DylibCommand.bytesize + new_id.size
	new_sizeofcmds += new_size - dylib_id_cmd.cmdsize

	# calculate the low file offset (offset to first section data)
	low_fileoff = 2**64 # ULLONGMAX

	segments.each do |seg|
		sections(seg).each do |sect|
			if sect.size != 0 && !sect.flag?(S_ZEROFILL) &&
					!sect.flag?(S_THREAD_LOCAL_ZEROFILL) &&
					sect.offset < low_fileoff

				low_fileoff = sect.offset
			end
		end
	end

	if new_sizeofcmds + header.bytesize > low_fileoff
		raise HeaderPadError.new(@filename)
	end

	# update sizeofcmds in mach_header
	set_sizeofcmds(new_sizeofcmds)

	# update cmdsize in the dylib_command
	@raw_data[dylib_id_cmd.offset + 4, 4] = [new_size].pack("V")

	# delete the old id
	@raw_data.slice!(dylib_id_cmd.offset + dylib_id_cmd.name...dylib_id_cmd.offset + dylib_id_cmd.class.bytesize + old_id.size)

	# insert the new id
	@raw_data.insert(dylib_id_cmd.offset + dylib_id_cmd.name, new_id)

	# pad/unpad after new_sizeofcmds until offsets are corrected
	null_pad = old_id.size - new_id.size

	if null_pad < 0
		@raw_data.slice!(new_sizeofcmds + header.bytesize, null_pad.abs)
	else
		@raw_data.insert(new_sizeofcmds + header.bytesize, "\x00" * null_pad)
	end

	# synchronize fields with the raw data
	header = get_mach_header
	load_commands = get_load_commands
end

#executable? ⇒ Boolean

Returns true if the Mach-O is of type ‘MH_EXECUTE`, false otherwise.

Returns:

  • (Boolean) —

    true if the Mach-O is of type ‘MH_EXECUTE`, false otherwise



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# File 'lib/macho/macho_file.rb', line 62

def executable?
	header[:filetype] == MH_EXECUTE
end

#filetype ⇒ String

Returns a string representation of the Mach-O’s filetype.

Returns:

  • (String) —

    a string representation of the Mach-O’s filetype



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# File 'lib/macho/macho_file.rb', line 87

def filetype
	MH_FILETYPES[header[:filetype]]
end

#flags ⇒ Fixnum

Returns execution flags set by the linker.

Returns:

  • (Fixnum) —

    execution flags set by the linker



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# File 'lib/macho/macho_file.rb', line 112

def flags
	header[:flags]
end

#initialize_from_bin(bin) ⇒ Object 



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# File 'lib/macho/macho_file.rb', line 38

def initialize_from_bin(bin)
	@filename = nil
	@raw_data = bin
	@header = get_mach_header
	@load_commands = get_load_commands
end

#linked_dylibs ⇒ Array<String>

All shared libraries linked to the Mach-O.

Returns:

  • (Array<String>) —

    an array of all shared libraries



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# File 'lib/macho/macho_file.rb', line 240

def linked_dylibs
	dylibs = []
	dylib_cmds = command('LC_LOAD_DYLIB')

	dylib_cmds.each do |dylib_cmd|
		cmdsize = dylib_cmd.cmdsize
		offset = dylib_cmd.offset
		stroffset = dylib_cmd.name

		dylib = @raw_data.slice(offset + stroffset...offset + cmdsize).unpack("Z*").first

		dylibs << dylib
	end

	dylibs
end

#magic ⇒ Fixnum

Returns the Mach-O’s magic number.

Returns:

  • (Fixnum) —

    the Mach-O’s magic number



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# File 'lib/macho/macho_file.rb', line 77

def magic
	header[:magic]
end

#magic32? ⇒ Boolean

Returns true if the Mach-O has 32-bit magic, false otherwise.

Returns:

  • (Boolean) —

    true if the Mach-O has 32-bit magic, false otherwise



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# File 'lib/macho/macho_file.rb', line 52

def magic32?
	MachO.magic32?(header[:magic])
end

#magic64? ⇒ Boolean

Returns true if the Mach-O has 64-bit magic, false otherwise.

Returns:

  • (Boolean) —

    true if the Mach-O has 64-bit magic, false otherwise



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# File 'lib/macho/macho_file.rb', line 57

def magic64?
	MachO.magic64?(header[:magic])
end

#magic_string ⇒ String

Returns a string representation of the Mach-O’s magic number.

Returns:

  • (String) —

    a string representation of the Mach-O’s magic number



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# File 'lib/macho/macho_file.rb', line 82

def magic_string
	MH_MAGICS[header[:magic]]
end

#ncmds ⇒ Fixnum

Returns the number of load commands in the Mach-O’s header.

Returns:

  • (Fixnum) —

    the number of load commands in the Mach-O’s header



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# File 'lib/macho/macho_file.rb', line 102

def ncmds
	header[:ncmds]
end

#sections(segment) ⇒ Array<MachO::Section>, Array<MachO::Section64>

All sections of the segment ‘segment`.

Returns:



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# File 'lib/macho/macho_file.rb', line 329

def sections(segment)
	sections = []

	if !segment.is_a?(SegmentCommand) && !segment.is_a?(SegmentCommand64)
		raise ArgumentError.new("not a valid segment")
	end

	if segment.nsects.zero?
		return sections
	end

	offset = segment.offset + segment.class.bytesize

	segment.nsects.times do
		if segment.is_a? SegmentCommand
			sections << Section.new_from_bin(@raw_data.slice(offset, Section.bytesize))
			offset += Section.bytesize
		else
			sections << Section64.new_from_bin(@raw_data.slice(offset, Section64.bytesize))
			offset += Section64.bytesize
		end
	end

	sections
end

#segments ⇒ Array<MachO::SegmentCommand>, Array<MachO::SegmentCommand64>

All segment load commands in the Mach-O.

Returns:



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# File 'lib/macho/macho_file.rb', line 130

def segments
	if magic32?
		command("LC_SEGMENT")
	else
		command("LC_SEGMENT_64")
	end
end

#serialize ⇒ String

The file’s raw Mach-O data.

Returns:

  • (String) —

    the raw Mach-O data



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# File 'lib/macho/macho_file.rb', line 47

def serialize
	@raw_data
end

#sizeofcmds ⇒ Fixnum

Returns the size of all load commands, in bytes.

Returns:

  • (Fixnum) —

    the size of all load commands, in bytes



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# File 'lib/macho/macho_file.rb', line 107

def sizeofcmds
	header[:sizeofcmds]
end

#write(filename) ⇒ void

This method returns an undefined value.

Write all Mach-O data to the given filename.

Parameters:

  • filename (String) —

    the file to write to



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# File 'lib/macho/macho_file.rb', line 358

def write(filename)
	File.open(filename, "wb") { |f| f.write(@raw_data) }
end

#write! ⇒ void

Note:

Overwrites all data in the file!

This method returns an undefined value.

Write all Mach-O data to the file used to initialize the instance.

Raises:

  • (MachOError) —

    if the instance was created from a binary string



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# File 'lib/macho/macho_file.rb', line 366

def write!
	if @filename.nil?
		raise MachOError.new("cannot write to a default file when initialized from a binary string")
	else
		File.open(@filename, "wb") { |f| f.write(@raw_data) }
	end
end