Class: Rex::MachScan::Scanner::JmpRegScanner

Inherits:
Generic
  • Object
show all
Defined in:
lib/rex/machscan/scanner.rb

Direct Known Subclasses

PopPopRetScanner, RegexScanner

Instance Attribute Summary

Attributes inherited from Generic

#fat, #mach, #regex

Instance Method Summary collapse

Methods inherited from Generic

#initialize, #scan

Constructor Details

This class inherits a constructor from Rex::MachScan::Scanner::Generic

Instance Method Details

#_build_byte_list(base, regnums) ⇒ Object

build a list for regex of the possible bytes, based on a base byte and a list of register numbers..



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# File 'lib/rex/machscan/scanner.rb', line 74

def _build_byte_list(base, regnums)
  regnums.collect { |regnum| Regexp.escape((base | regnum).chr) }.join('')
end

#_parse_ret(data) ⇒ Object 



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# File 'lib/rex/machscan/scanner.rb', line 88

def _parse_ret(data)
  if data.length == 1
    return "ret"
  else
    return "retn 0x%04x" % data[1, 2].unpack('v')[0]
  end
end

#_ret_size(offset) ⇒ Object 



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# File 'lib/rex/machscan/scanner.rb', line 78

def _ret_size(offset)
  case mach.read(offset, 1)
  when "\xc3"
      return 1
  when "\xc2"
      return 3
  end
  $stderr.puts("Invalid return instruction")
end

#config(param) ⇒ Object 



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# File 'lib/rex/machscan/scanner.rb', line 53

def config(param)
  regnums = param['args']

  # build a list of the call bytes
  calls  = _build_byte_list(0xd0, regnums - [4]) # note call esp's don't work..
  jmps   = _build_byte_list(0xe0, regnums)
  pushs1 = _build_byte_list(0x50, regnums)
  pushs2 = _build_byte_list(0xf0, regnums)

  regexstr = '('
  if !calls.empty?
      regexstr += "\xff[#{calls}]|"
  end

  regexstr += "\xff[#{jmps}]|([#{pushs1}]|\xff[#{pushs2}])(\xc3|\xc2..))"

  self.regex = Regexp.new(regexstr, nil, 'n')
end

#scan_segment(segment, param = {}) ⇒ Object 



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# File 'lib/rex/machscan/scanner.rb', line 96

def scan_segment(segment, param={})
  base_addr = segment.vmaddr
  segment_offset = segment.fileoff
  offset = segment_offset

  hits = []

  while (offset = mach.index(regex, offset)) != nil

    vaddr = base_addr + (offset - segment_offset)
    message = ''

    parse_ret = false

    byte1 = mach.read(offset, 1).unpack("C*")[0]

    if byte1 == 0xff
      byte2   = mach.read(offset+1, 1).unpack("C*")[0]
      regname = Rex::Arch::X86.reg_name32(byte2 & 0x7)

      case byte2 & 0xf8
      when 0xd0
          message = "call #{regname}"
          offset += 2
      when 0xe0
          message = "jmp #{regname}"
          offset += 2
      when 0xf0
          retsize = _ret_size(offset+2)
          message = "push #{regname}; " + _parse_ret(mach.read(offset+2, retsize))
          offset += 2 + retsize
      else
          raise "Unexpected value at offset: #{offset}"
      end
    else
      regname = Rex::Arch::X86.reg_name32(byte1 & 0x7)
      retsize = _ret_size(offset+1)
      message = "push #{regname}; " + _parse_ret(mach.read(offset+1, retsize))
      offset += 1 + retsize
    end

    hits << [ vaddr, message ]
  end

  return hits
end