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 75

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 89

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 79

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 54

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 97

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 "wtf"
			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