Windows下后台服务程序启动前台可交互界面程序
有时在我们编写的前台程序需要开机运行，当有后台程序时可以注册服务方式进行启动(system权限)，前台程序的启动需要等待用户登录到桌面后运行(涉及界面交互等)，前台程序的启动主要有几种方式：
1. 写入启动项注册表进行自动启动，这时启动的程序是以当前用户权限运行，弊端是权限低且不安全，用户可人为或被其他安全软件禁用；
2. 创建计划任务方式启动，计划任务属性中可设置以最高权限运行，相当于管理员权限运行前台程序，可设置任何时间段运行程序，弊端也是不安全，人为或其他安全软件可禁用计划任务；
3. 通过后台服务拉前台程序，这种是最安全的方式(后台服务也可实时守护该程序运行)，也是大多数安装软件所使用的，主要有两种方式启动：
(1) 绕过UAC以最高权限启动
自Vista操作系统之后，微软考虑到安全因素，在系统管理员账户和标准用户之间创出了UAC(用户账户控制)。当标准用户启动需管理员权限的操作时要弹框让用户确认，这样可防止恶意软件或间谍软件随意修改系统造成破坏。
但对于必须要通过最高权限运行交互进程来说就造成问题，微软API接口提供CreateProcessAsUser函数用于在后台服务程序中启动前台进程，但启动时要请求UAC权限(由于后台服务是最高权限启动，其创建的子进程也继承最高权限)，这时后台UAC窗口无法显示在前台界面上，造成程序永远等待无法启动。
vista之后，微软会为每个登录用户分配一个会话，后台服务在系统启动时最先启动，分配的会话ID为0，其后每登录一个用户会话ID加1：
问题来了，由于有会话隔离，我们无法在一个会话程序中直接启动另一会话的程序。但微软有一个特殊的进程，对于每个会话会有一个对应的进程，这个进程就是winlogin.exe：
winlogin进程的作用
Winlogon.exe进程是微软公司为其Windows操作系统定义的一个非常重要的系统核心进程，被称为“Windows登陆应用程序”，它会随着系统启动而启动并一直运行。通常情况下此进程应该是安全的，并且只占用很少的CPU及内存资源，如果资源占用过多则很有可能被病毒“劫持”。
请不要尝试将本进程终止（也无法在任务管理器将其终止）或将此进程从系统中删除，这会导致你的系统无法正常运行。因为Winlogon.exe进程为系统提供了有以下4项重要的功能：
- 在登录系统时加载的用户配置文件，以及执行注销用户与锁定计算机；
- 负责处理Ctrl+Alt+Del快捷键（SAS）的功能；
- 监控键盘和鼠标使用情况来决定什么时候启动屏幕保护程序；
- 检验Windows操作系统激活密钥是否为合法许可；
可以发现winlogin进程是后台服务进程，但所属登录用户会话，那是不是可以通过这个进程来达到我们绕过UAC的限制启动前台交互程序呢？没错！！！
有了winlogin进程，我们可以在后台服务中先查询到winlogin进程信息，获取其访问令牌，最后通过CreateProcessAsUser将进程启动到活动登录用户当前活动会话。由于和前台界面所属同一会话，启动后的程序便可以进行交互。Exciting！！！
好了，来看看代码吧：
1. C++代码
BOOL LaunchAppIntoDifferentSession()
{
PROCESS_INFORMATION pi;
STARTUPINFO si;
BOOL bResult = FALSE;
DWORD dwSessionId,winlogonPid;
HANDLE hUserToken,hUserTokenDup,hPToken,hProcess;
DWORD dwCreationFlags;
// Log the client on to the local computer.
dwSessionId = WTSGetActiveConsoleSessionId();
//////////////////////////////////////////
// Find the winlogon process
////////////////////////////////////////
PROCESSENTRY32 procEntry;
HANDLE hSnap = CreateToolhelp32Snapshot(TH32CS_SNAPPROCESS, 0);
if (hSnap == INVALID_HANDLE_VALUE)
{
return 1 ;
}
procEntry.dwSize = sizeof(PROCESSENTRY32);
if (!Process32First(hSnap, &procEntry))
{
return 1 ;
}
do
{
if (_wcsicmp(procEntry.szExeFile, L"winlogon.exe") == 0)
{
// We found a winlogon process...
// make sure it's running in the console session
DWORD winlogonSessId = 0;
if (ProcessIdToSessionId(procEntry.th32ProcessID, &winlogonSessId)
&& winlogonSessId == dwSessionId)
{
winlogonPid = procEntry.th32ProcessID;
break;
}
}
} while (Process32Next(hSnap, &procEntry));
////////////////////////////////////////////////////////////////////////
WTSQueryUserToken(dwSessionId,&hUserToken);
dwCreationFlags = NORMAL_PRIORITY_CLASS|CREATE_NEW_CONSOLE;
ZeroMemory(&si, sizeof(STARTUPINFO));
si.cb= sizeof(STARTUPINFO);
si.lpDesktop = L"winsta0\\default";
ZeroMemory(&pi, sizeof(pi));
TOKEN_PRIVILEGES tp;
LUID luid;
hProcess = OpenProcess(MAXIMUM_ALLOWED,FALSE,winlogonPid);
if(!::OpenProcessToken(hProcess,TOKEN_ADJUST_PRIVILEGES|TOKEN_QUERY
|TOKEN_DUPLICATE|TOKEN_ASSIGN_PRIMARY|TOKEN_ADJUST_SESSIONID
|TOKEN_READ|TOKEN_WRITE,&hPToken))
{
int abcd = GetLastError();
printf("Process token open Error: %u\n",GetLastError());
}
if (!LookupPrivilegeValue(NULL,SE_DEBUG_NAME,&luid))
{
printf("Lookup Privilege value Error: %u\n",GetLastError());
}
tp.PrivilegeCount =1;
tp.Privileges[0].Luid =luid;
tp.Privileges[0].Attributes =SE_PRIVILEGE_ENABLED;
DuplicateTokenEx(hPToken,MAXIMUM_ALLOWED,NULL,
SecurityIdentification,TokenPrimary,&hUserTokenDup);
int dup = GetLastError();
//Adjust Token privilege
SetTokenInformation(hUserTokenDup,
TokenSessionId,(void*)dwSessionId,sizeof(DWORD));
if (!AdjustTokenPrivileges(hUserTokenDup,FALSE,&tp,sizeof(TOKEN_PRIVILEGES),
(PTOKEN_PRIVILEGES)NULL,NULL))
{
int abc =GetLastError();
printf("Adjust Privilege value Error: %u\n",GetLastError());
}
if (GetLastError()== ERROR_NOT_ALL_ASSIGNED)
{
printf("Token does not have the provilege\n");
}
LPVOID pEnv =NULL;
if(CreateEnvironmentBlock(&pEnv,hUserTokenDup,TRUE))
{
dwCreationFlags|=CREATE_UNICODE_ENVIRONMENT;
}
else
pEnv=NULL;
// Launch the process in the client's logon session.
bResult = CreateProcessAsUser(
hUserTokenDup, // client's access token
_T("cmd.exe"), // file to execute
NULL, // command line
NULL, // pointer to process SECURITY_ATTRIBUTES
NULL, // pointer to thread SECURITY_ATTRIBUTES
FALSE, // handles are not inheritable
dwCreationFlags, // creation flags
pEnv, // pointer to new environment block
NULL, // name of current directory
&si, // pointer to STARTUPINFO structure
&pi // receives information about new process
);
// End impersonation of client.
//GetLastError Shud be 0
int iResultOfCreateProcessAsUser = GetLastError();
//Perform All the Close Handles tasks
CloseHandle(hProcess);
CloseHandle(hUserToken);
CloseHandle(hUserTokenDup);
CloseHandle(hPToken);
return 0;
}简单讲解一下：
(1)通过WTSGetActiveConsoleSessionId获取当前活动会话；
(2)通过CreateToolhelp32Snapshot获取当前所有活动进程，查找到当前活动会话的winlogin进程信息(pid)；
(3)通过WTSQueryUserToken，OpenProcessToken等复制winlogin进程的访问令牌信息；
(4)通过LookupPrivilegeValue，AdjustTokenPrivileges等进行提权操作；
(5)最后通过CreateProcessAsUser启动交互式进程。
关于参数中"@"winsta0\default""：这是一个硬编码string，微软任意选择向操作系统表明我们即将产生的进程CreateProcessAsUser应该具有对交互式windowstation和桌面的完全访问权限，这基本上意味着它允许在桌面上显示UI元素。
2. C#代码
public static bool StartProcessAndBypassUAC(String applicationName, out PROCESS_INFORMATION procInfo)
{
uint winlogonPid = 0;
IntPtr hUserTokenDup = IntPtr.Zero, hPToken = IntPtr.Zero, hProcess = IntPtr.Zero;
procInfo = new PROCESS_INFORMATION();
// obtain the currently active session id; every logged on user in the system has a unique session id
uint dwSessionId = WTSGetActiveConsoleSessionId();
// obtain the process id of the winlogon process that is running within the currently active session
Process[] processes = Process.GetProcessesByName("winlogon");
foreach (Process p in processes)
{
if ((uint)p.SessionId == dwSessionId)
{
winlogonPid = (uint)p.Id;
}
}
// obtain a handle to the winlogon process
hProcess = OpenProcess(MAXIMUM_ALLOWED, false, winlogonPid);
// obtain a handle to the access token of the winlogon process
if (!OpenProcessToken(hProcess, TOKEN_DUPLICATE, ref hPToken))
{
CloseHandle(hProcess);
return false;
}
// Security attibute structure used in DuplicateTokenEx and CreateProcessAsUser
// I would prefer to not have to use a security attribute variable and to just
// simply pass null and inherit (by default) the security attributes
// of the existing token. However, in C# structures are value types and therefore
// cannot be assigned the null value.
SECURITY_ATTRIBUTES sa = new SECURITY_ATTRIBUTES();
sa.Length = Marshal.SizeOf(sa);
// copy the access token of the winlogon process; the newly created token will be a primary token
if (!DuplicateTokenEx(hPToken, MAXIMUM_ALLOWED, ref sa, (int)SECURITY_IMPERSONATION_LEVEL.SecurityIdentification, (int)TOKEN_TYPE.TokenPrimary, ref hUserTokenDup))
{
CloseHandle(hProcess);
CloseHandle(hPToken);
return false;
}
// By default CreateProcessAsUser creates a process on a non-interactive window station, meaning
// the window station has a desktop that is invisible and the process is incapable of receiving
// user input. To remedy this we set the lpDesktop parameter to indicate we want to enable user
// interaction with the new process.
STARTUPINFO si = new STARTUPINFO();
si.cb = (int)Marshal.SizeOf(si);
si.lpDesktop = @"winsta0\default"; // interactive window station parameter; basically this indicates that the process created can display a GUI on the desktop
// flags that specify the priority and creation method of the process
int dwCreationFlags = NORMAL_PRIORITY_CLASS | CREATE_NEW_CONSOLE;
// create a new process in the current user's logon session
bool result = CreateProcessAsUser(hUserTokenDup, // client's access token
null, // file to execute
applicationName, // command line
ref sa, // pointer to process SECURITY_ATTRIBUTES
ref sa, // pointer to thread SECURITY_ATTRIBUTES
false, // handles are not inheritable
dwCreationFlags, // creation flags
IntPtr.Zero, // pointer to new environment block
null, // name of current directory
ref si, // pointer to STARTUPINFO structure
out procInfo // receives information about new process
);
// invalidate the handles
CloseHandle(hProcess);
CloseHandle(hPToken);
CloseHandle(hUserTokenDup);
return result; // return the result
}参考：https://www.codeproject.com/Articles/35773/Subverting-Vista-UAC-in-Both-32-and-64-bit-Archite
https://www.codeproject.com/Articles/18367/Launch-your-application-in-Vista-under-the-local-s
（2）获取explorer进程的令牌信息保证前台进程以低权限方式运行
用户登录后，explorer管理器会启动，且是基于当前用户权限的，所以获取explorer令牌的方式启动的前台进程也是基于当前用户权限，这种方式和直接手动运行前台程序效果一样，弊端就是当程序中含有高权限操作(如对系统目录/注册表等写操作)会出现权限不足而失败，所以当出现这类操作时最好使用上面的启动方式。
BOOL CreateProcessByExplorer(LPCWSTR process, LPCWSTR cmd)
{
BOOL ret = FALSE;
HANDLE hProcess = 0, hToken = 0, hDuplicatedToken = 0;
LPVOID lpEnv = NULL;
do
{
DWORD explorerPid = GetActiveProcessId(L"explorer.exe", TRUE); // 获取explorer进程号，自行实现
if (explorerPid == -1)
break;
hProcess = OpenProcess(PROCESS_QUERY_INFORMATION, TRUE, explorerPid);
if (INVALID_HANDLE_VALUE == hProcess)
break;
if (!OpenProcessToken(hProcess, TOKEN_ALL_ACCESS, &hToken))
break;
DuplicateTokenEx(hToken, MAXIMUM_ALLOWED, NULL, SecurityIdentification, TokenPrimary, &hDuplicatedToken);
CreateEnvironmentBlock(&lpEnv, hDuplicatedToken, FALSE);
wstring processCmd = L"\"";
processCmd += process;
if (NULL != cmd)
processCmd += wstring(L"\" \"") + cmd;
processCmd += L"\"";
STARTUPINFO si = {0};
PROCESS_INFORMATION pi = {0};
si.cb = sizeof(STARTUPINFO);
si.lpDesktop = L"winsta0\\default";
si.dwFlags = STARTF_USESHOWWINDOW;
si.wShowWindow = SW_HIDE;
if (!CreateProcessAsUser(hToken, NULL, const_cast(processCmd.c_str()), 0, 0, FALSE, CREATE_UNICODE_ENVIRONMENT, lpEnv, 0, &si, &pi))
break;
ret = TRUE;
} while (0);
if (INVALID_HANDLE_VALUE != hProcess)
CloseHandle(hProcess);
if (INVALID_HANDLE_VALUE != hToken)
CloseHandle(hToken);
if (INVALID_HANDLE_VALUE != hDuplicatedToken)
CloseHandle(hDuplicatedToken);
if (NULL != lpEnv)
DestroyEnvironmentBlock(lpEnv);
return ret;
} 调用方式：
CreateProcessByExplorer(L"test.exe", NULL);参考：
https://blog.csdn.net/huanglong8/article/details/53574120