穿透Session 0 隔离（二）
上一篇我们已经对Session 0 隔离有了进一步认识，如果在开发过程中确实需要服务与桌面用户进行交互，可以通过远程桌面服务的API 绕过Session 0 的隔离完成交互操作。
对于简单的交互，服务可以通过WTSSendMessage 函数，在用户Session 上显示消息窗口。对于一些复杂的UI 交互，必须调用CreateProcessAsUser 或其他方法（WCF、.NET远程处理等）进行跨Session 通信，在桌面用户上创建一个应用程序界面。
WTSSendMessage 函数
如果服务只是简单的向桌面用户Session 发送消息窗口，则可以使用WTSSendMessage 函数实现。首先，在上一篇下载的代码中加入一个Interop.cs 类，并在类中加入如下代码：
public static IntPtr WTS_CURRENT_SERVER_HANDLE = IntPtr.Zero; public static void ShowMessageBox(string message, string title) { int resp = 0; WTSSendMessage( WTS_CURRENT_SERVER_HANDLE, WTSGetActiveConsoleSessionId(), title, title.Length, message, message.Length, 0, 0, out resp, false); } [DllImport("kernel32.dll", SetLastError = true)] public static extern int WTSGetActiveConsoleSessionId(); [DllImport("wtsapi32.dll", SetLastError = true)] public static extern bool WTSSendMessage( IntPtr hServer, int SessionId, String pTitle, int TitleLength, String pMessage, int MessageLength, int Style, int Timeout, out int pResponse, bool bWait);
在ShowMessageBox 函数中调用了WTSSendMessage 来发送信息窗口，这样我们就可以在Service 的OnStart 函数中使用，打开Service1.cs 加入下面代码：
protected override void OnStart(string[] args) { Interop.ShowMessageBox("This a message from AlertService.",
"AlertService Message"); }
编译程序后在服务管理器中重新启动AlertService 服务，从下图中可以看到消息窗口是在当前用户桌面显示的，而不是Session 0 中。
CreateProcessAsUser 函数
如果想通过服务向桌面用户Session 创建一个复杂UI 程序界面，则需要使用CreateProcessAsUser 函数为用户创建一个新进程用来运行相应的程序。打开Interop 类继续添加下面代码：
public static void CreateProcess(string app, string path) { bool result; IntPtr hToken = WindowsIdentity.GetCurrent().Token; IntPtr hDupedToken = IntPtr.Zero; PROCESS_INFORMATION pi = new PROCESS_INFORMATION(); SECURITY_ATTRIBUTES sa = new SECURITY_ATTRIBUTES(); sa.Length = Marshal.SizeOf(sa); STARTUPINFO si = new STARTUPINFO(); si.cb = Marshal.SizeOf(si); int dwSessionID = WTSGetActiveConsoleSessionId(); result = WTSQueryUserToken(dwSessionID, out hToken); if (!result) { ShowMessageBox("WTSQueryUserToken failed", "AlertService Message"); } result = DuplicateTokenEx( hToken, GENERIC_ALL_ACCESS, ref sa, (int)SECURITY_IMPERSONATION_LEVEL.SecurityIdentification, (int)TOKEN_TYPE.TokenPrimary, ref hDupedToken ); if (!result) { ShowMessageBox("DuplicateTokenEx failed" ,"AlertService Message"); } IntPtr lpEnvironment = IntPtr.Zero; result = CreateEnvironmentBlock(out lpEnvironment, hDupedToken, false); if (!result) { ShowMessageBox("CreateEnvironmentBlock failed", "AlertService Message"); } result = CreateProcessAsUser( hDupedToken, app, String.Empty, ref sa, ref sa, false, 0, IntPtr.Zero, path, ref si, ref pi); if (!result) { int error = Marshal.GetLastWin32Error(); string message = String.Format("CreateProcessAsUser Error: {0}", error); ShowMessageBox(message, "AlertService Message"); } if (pi.hProcess != IntPtr.Zero) CloseHandle(pi.hProcess); if (pi.hThread != IntPtr.Zero) CloseHandle(pi.hThread); if (hDupedToken != IntPtr.Zero) CloseHandle(hDupedToken); } [StructLayout(LayoutKind.Sequential)] public struct STARTUPINFO { public Int32 cb; public string lpReserved; public string lpDesktop; public string lpTitle; public Int32 dwX; public Int32 dwY; public Int32 dwXSize; public Int32 dwXCountChars; public Int32 dwYCountChars; public Int32 dwFillAttribute; public Int32 dwFlags; public Int16 wShowWindow; public Int16 cbReserved2; public IntPtr lpReserved2; public IntPtr hStdInput; public IntPtr hStdOutput; public IntPtr hStdError; } [StructLayout(LayoutKind.Sequential)] public struct PROCESS_INFORMATION { public IntPtr hProcess; public IntPtr hThread; public Int32 dwProcessID; public Int32 dwThreadID; } [StructLayout(LayoutKind.Sequential)] public struct SECURITY_ATTRIBUTES { public Int32 Length; public IntPtr lpSecurityDescriptor; public bool bInheritHandle; } public enum SECURITY_IMPERSONATION_LEVEL { SecurityAnonymous, SecurityIdentification, SecurityImpersonation, SecurityDelegation } public enum TOKEN_TYPE { TokenPrimary = 1, TokenImpersonation } public const int GENERIC_ALL_ACCESS = 0x10000000; [DllImport("kernel32.dll", SetLastError = true, CharSet = CharSet.Auto, CallingConvention = CallingConvention.StdCall)] public static extern bool CloseHandle(IntPtr handle); [DllImport("advapi32.dll", SetLastError = true, CharSet = CharSet.Ansi, CallingConvention = CallingConvention.StdCall)] public static extern bool CreateProcessAsUser( IntPtr hToken, string lpApplicationName, string lpCommandLine, ref SECURITY_ATTRIBUTES lpProcessAttributes, ref SECURITY_ATTRIBUTES lpThreadAttributes, bool bInheritHandle, Int32 dwCreationFlags, IntPtr lpEnvrionment, string lpCurrentDirectory, ref STARTUPINFO lpStartupInfo, ref PROCESS_INFORMATION lpProcessInformation); [DllImport("advapi32.dll", SetLastError = true)] public static extern bool DuplicateTokenEx( IntPtr hExistingToken, Int32 dwDesiredAccess, ref SECURITY_ATTRIBUTES lpThreadAttributes, Int32 ImpersonationLevel, Int32 dwTokenType, ref IntPtr phNewToken); [DllImport("wtsapi32.dll", SetLastError=true)] public static extern bool WTSQueryUserToken( Int32 sessionId, out IntPtr Token); [DllImport("userenv.dll", SetLastError = true)] static extern bool CreateEnvironmentBlock( out IntPtr lpEnvironment, IntPtr hToken, bool bInherit);
在CreateProcess 函数中同时也涉及到DuplicateTokenEx、WTSQueryUserToken、CreateEnvironmentBlock 函数的使用，有兴趣的朋友可通过MSDN 进行学习。完成CreateProcess 函数创建后，就可以真正的通过它来调用应用程序了，回到Service1.cs 修改一下OnStart 我们来打开一个CMD 窗口。如下代码：
protected override void OnStart(string[] args) { Interop.CreateProcess("cmd.exe",@"C:\Windows\System32\"); }
重新编译程序，启动AlertService 服务便可看到下图界面。至此，我们已经可以通过一些简单的方法对Session 0 隔离问题进行解决。大家也可以通过WCF 等技术完成一些更复杂的跨Session 通信方式，实现在Windows 7 及Vista 系统中服务与桌面用户的交互操作。
参考资料
1. WTSSendMessage Function
http://msdn.microsoft.com/en-us/library/aa383842(VS.85).aspx
2. CreateProcessAsUser Function
http://msdn.microsoft.com/en-us/library/ms682429(v=VS.85).aspx
3. WTSSendMessage (wtsapi32)
http://www.pinvoke.net/default.aspx/wtsapi32/WTSSendMessage.html
4. WTSQueryUserToken Function
http://msdn.microsoft.com/en-us/library/aa383840(VS.85).aspx
5. http://www.pinvoke.net/