Permalink
Switch branches/tags
Nothing to show
Find file Copy path
Fetching contributors…
Cannot retrieve contributors at this time
95 lines (81 sloc) 2.61 KB
#include <stdio.h>
#include <windows.h>
#include "peconv.h"
const size_t g_flagLen = 26;
char g_flag[g_flagLen + 1] = { 0 };
int my_index()
{
static int index = 0;
return (index++) % g_flagLen;
}
int _stdcall my_MessageBoxA(
_In_opt_ HWND hWnd,
_In_opt_ LPCSTR lpText,
_In_opt_ LPCSTR lpCaption,
_In_ UINT uType)
{
int key_part = 0;
int key_id = 0;
sscanf(lpText,"key[%d] = %x;", &key_id, &key_part);
g_flag[key_id] = key_part;
return 0;
}
DWORD exec_func(HMODULE loaded_pe, char *checked_str)
{
DWORD (*exported_func) (DWORD arg0, DWORD arg1, LPSTR str, DWORD arg3) = NULL;
exported_func = (DWORD (*) (DWORD, DWORD, LPSTR, DWORD))
peconv::get_exported_func(loaded_pe, MAKEINTRESOURCE(1));
if (exported_func == NULL) {
return -1;
}
exported_func(0, 0, checked_str, 0);
return 0;
}
bool load_next_char(const char *path)
{
peconv::hooking_func_resolver my_res;
my_res.add_hook("MessageBoxA", (FARPROC) &my_MessageBoxA);
size_t v_size = 0;
BYTE* loaded_pe = peconv::load_pe_executable(
path, v_size,
(peconv::t_function_resolver*) &my_res
);
if (!loaded_pe) {
printf("Loading module failed!\n");
return false;
}
ULONGLONG func_offset = (ULONGLONG)loaded_pe + 0x5D30;
ULONGLONG srand_offset = (ULONGLONG)loaded_pe + 0x7900;
ULONGLONG rand_offset = (ULONGLONG)loaded_pe + 0x78D4;
ULONGLONG calc_index_offset = (ULONGLONG)loaded_pe + 0x4710;
peconv::redirect_to_local64((void*)srand_offset, (ULONGLONG)&srand);
peconv::redirect_to_local64((void*)rand_offset, (ULONGLONG)&rand);
peconv::redirect_to_local64((void*)calc_index_offset, (ULONGLONG)&my_index);
__int64 (__fastcall *to_overwrite_mem)(__int64 a1) = NULL;
to_overwrite_mem = ( __int64 (__fastcall *)(__int64 ))func_offset;
__int64 ret = to_overwrite_mem(0);
std::vector<std::string> names_vec;
if (peconv::get_exported_names(loaded_pe, names_vec) > 0) {
const char *first_name = names_vec[0].c_str();
exec_func((HMODULE)loaded_pe, const_cast<char *>(first_name));
}
peconv::free_pe_buffer(loaded_pe, v_size);
return true;
}
int main(int argc, char *argv[])
{
char *path = NULL; //i.e. "C:\\FlareOn2017\\payload.dll"
if (argc < 2) {
printf("Args: <path>\n");
printf("path: path to the crackme (FlareOn2017 chall6: payload.dll)\n");
system("pause");
return -1;
}
path = argv[1];
for (int i = 0; i < 26; i++) {
if (!load_next_char(path)) break;
}
printf("Flag:\n%s\n", g_flag);
system("pause");
return 0;
}