109 lines
1.9 KiB
NASM
109 lines
1.9 KiB
NASM
format PE console
|
|
entry start
|
|
include 'C:\\Projects/asm/INCLUDE/win32a.inc'
|
|
include 'C:\\Projects/asm/std.inc'
|
|
|
|
section '.mrph' code readable executable writeable
|
|
mrph:
|
|
|
|
file 'base_block.bin'
|
|
|
|
|
|
section '.stat' code readable executable
|
|
|
|
data import
|
|
library msvcrt, 'msvcrt.dll'
|
|
import msvcrt, \
|
|
printf , 'printf', \
|
|
puts , 'puts', \
|
|
scanf , 'scanf', \
|
|
sin , 'sin', \
|
|
cos , 'cos', \
|
|
tan , 'tan', \
|
|
asin , 'asin', \
|
|
acos , 'acos', \
|
|
atan , 'atan', \
|
|
malloc , 'malloc', \
|
|
free , 'free', \
|
|
getchar , 'getchar'
|
|
end data
|
|
|
|
do_morph:
|
|
push ebp
|
|
mov eax, 1
|
|
mov edx, dword [num_block]
|
|
lea ecx, [block_ptrs + 4*edx]
|
|
mov ecx, dword [ecx]
|
|
|
|
cmp ecx, 0 ; If the block ptr is null return
|
|
jz .finish
|
|
|
|
inc edx
|
|
mov dword [num_block], edx
|
|
lea edx, [ecx+512]
|
|
mov edi, mrph
|
|
|
|
.mod:
|
|
cmp ecx, edx
|
|
jz .finish
|
|
movzx eax, byte [ecx]
|
|
movzx ebp, byte [edi]
|
|
xor eax, ebp
|
|
mov byte [edi], al
|
|
inc edi
|
|
inc ecx
|
|
xor eax, eax
|
|
jmp .mod
|
|
|
|
.finish:
|
|
pop ebp
|
|
ret
|
|
|
|
; No args, flushes input.
|
|
flush_inp:
|
|
call [getchar]
|
|
cmp eax, -1
|
|
jz .finish
|
|
cmp eax, ENDL
|
|
jnz flush_inp
|
|
.finish:
|
|
ret
|
|
|
|
; On entrance to each shellcode segment the ebx register will be a vtable of std funcs
|
|
; esi contains the base address of the shellcode segment
|
|
; edi contains the address of the part of the flag that this segment fills
|
|
; edx contains the number of the block
|
|
run_morphed:
|
|
mov esi, mrph
|
|
mov edx, dword [num_block]
|
|
dec edx
|
|
lea edi, [flag + 4*edx]
|
|
mov ebx, func_vtable
|
|
call mrph
|
|
ret
|
|
|
|
start:
|
|
call do_morph
|
|
cmp eax, 0
|
|
jnz .finish
|
|
call run_morphed
|
|
call flush_inp
|
|
jmp start
|
|
|
|
.finish:
|
|
ret
|
|
|
|
section '.dat' data readable writeable
|
|
|
|
num_block dd 0
|
|
|
|
func_vtable dd printf, puts, scanf, sin, cos, tan, asin, acos, atan, malloc, free, 0
|
|
|
|
flag db 64 dup (0)
|
|
|
|
b0.bin: file 'b0.bin'
|
|
b1.bin: file 'b1.bin'
|
|
b2.bin: file 'b2.bin'
|
|
b3.bin: file 'b3.bin'
|
|
b4.bin: file 'b4.bin'
|
|
block_ptrs dd b0.bin, b1.bin, b2.bin, b3.bin, b4.bin, 0
|