Class: Rex::Assembly::Nasm

Inherits:
Object
  • Object
show all
Defined in:
lib/rex/assembly/nasm.rb

Overview

This class uses nasm to assemble and disassemble stuff.

Defined Under Namespace

Classes: UnitTest

Constant Summary collapse

@@nasm_path = 
'nasm'
@@ndisasm_path = 
'ndisasm'

Class Method Summary collapse

Class Method Details

.assemble(assembly, bits = 32) ⇒ Object

Assembles the supplied assembly and returns the raw opcodes.



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# File 'lib/rex/assembly/nasm.rb', line 41

def self.assemble(assembly, bits=32)
	check

	# Open the temporary file
	tmp = Tempfile.new('nasmXXXX')
	tmp.binmode
	
	tpath = tmp.path
	opath = tmp.path + '.out'

	# Write the assembly data to a file
	tmp.write("BITS #{bits}\n" + assembly)
	tmp.flush()
	tmp.seek(0)

	# Run nasm
	if (system(@@nasm_path, '-f', 'bin', '-o', opath, tpath) == false)
		raise RuntimeError, "Assembler did not complete successfully: #{$?.exitstatus}"
	end

	# Read the assembled text
	rv = ::IO.read(opath)

	# Remove temporary files
	File.unlink(opath)
	tmp.close(true)

	rv
end

.check ⇒ Object

Ensures that the nasm environment is sane.



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# File 'lib/rex/assembly/nasm.rb', line 24

def self.check
	@@nasm_path =
		Rex::FileUtils.find_full_path('nasm')      ||
		Rex::FileUtils.find_full_path('nasm.exe')  ||
		Rex::FileUtils.find_full_path('nasmw.exe') ||
		raise(RuntimeError, "No nasm installation was found.")

	@@ndisasm_path =
		Rex::FileUtils.find_full_path('ndisasm')      ||
		Rex::FileUtils.find_full_path('ndisasm.exe')  ||
		Rex::FileUtils.find_full_path('ndisasmw.exe') ||
		raise(RuntimeError, "No ndisasm installation was found.")
end

.disassemble(raw, bits = 32) ⇒ Object

Disassembles the supplied raw opcodes



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# File 'lib/rex/assembly/nasm.rb', line 74

def self.disassemble(raw, bits=32)
	check

	tmp = Tempfile.new('nasmout')
	tmp.binmode
	
	tfd = File.open(tmp.path, "wb")

	tfd.write(raw)
	tfd.flush()
	tfd.close

	p = ::IO.popen("\"#{@@ndisasm_path}\" -b #{bits} \"#{tmp.path}\"")
	o = ''

	begin
		until p.eof?
			o += p.read
		end
	ensure
		p.close
	end

	tmp.close(true)

	o
end