Class: Rex::ElfScan::Scanner::JmpRegScanner

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

Direct Known Subclasses

PopPopRetScanner, RegexScanner

Instance Attribute Summary

Attributes inherited from Generic

#elf, #regex

Instance Method Summary collapse

Methods inherited from Generic

#initialize, #scan

Constructor Details

This class inherits a constructor from Rex::ElfScan::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/elfscan/scanner.rb', line 66

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/elfscan/scanner.rb', line 81

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/elfscan/scanner.rb', line 70

def _ret_size(offset)
	case elf.read(offset, 1)
		when "\xc3"
			return 1
		when "\xc2"
			return 3
	end

	raise "wtf"
end

#config(param) ⇒ Object 



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# File 'lib/rex/elfscan/scanner.rb', line 45

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(program_header, param = {}) ⇒ Object 



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# File 'lib/rex/elfscan/scanner.rb', line 90

def scan_segment(program_header, param={})
	offset = program_header.p_offset

	hits = []

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

		rva     = elf.offset_to_rva(offset)
		message = ''

		parse_ret = false

		byte1 = elf.read(offset, 1).unpack('C')[0]

		if byte1 == 0xff
			byte2   = elf.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(elf.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(elf.read(offset+1, retsize))
			offset += 1 + retsize
		end

		hits << [ rva, message ]
	end

	return hits
end