Logoff interactive users in Windows from a service
I'm trying to figure out a way to log off users in local Windows sessions from a Windows Service written in C#.
Here's the background to the problem: I need to manage the computer usage time of a set of users; when their allotted time expires I want to log them off. This is in the context of a W2K8 domain. Unfortunately the login time controls in Windows simply disconnect the user from server resources; there is no way to force their sessions to terminate via this method.
My approach is to build a Windows Service that I will deploy across the domain; the service will run on every client computer. At regular intervals the service will enumerate logged-in users on the computer, call out to a database to add the logged-in time since the last call to the total for the day, and if they have reached their maximum, log them out (with a five minute warning). Note - these are NOT terminal services sessions, they are regular local interactive logons. Note also that there may be multiple logons on a machine due to the "switch user" functionality in Win7 & Vista. All my client PCs will be running Win7. The Windows Service will be running as Local System so privileges should not be a problem.
I can successfully construct a list of logged-in users on the machine by user name using WMI. Here's a snippet of that code:
List<string> loggedInUsers = new List<string>();
ManagementClass mc = new ManagementClass("Win32_Process");
ManagementObjectCollection moc = mc.GetInstances();
foreach (ManagementObject mo in moc)
{
ROOT.CIMV2.Process process = new ROOT.CIMV2.Process(mo);
string domain, user;
uint pid;
process.GetOwner(out domain, out user);
pid = process.ProcessId;
if (process.Name.Trim().ToLower() == "explorer.exe")
loggedInUsers.Add(user);
}
return loggedInUsers;
However, I am struggling to find a method that will allow me to log off a selected user's session. I know I can shut down the machine, but I don't want that - that will kill all users' sessions.
Any ideas anyone? Thanks for reading this lengthy post!
Answer
You could use following P/Invoke calls to achieve this. Below sample works only with Admin Rights
[DllImport("wtsapi32.dll", SetLastError = true)]
static extern bool WTSLogoffSession(IntPtr hServer, int SessionId, bool bWait);
[DllImport("Wtsapi32.dll")]
static extern bool WTSQuerySessionInformation(
System.IntPtr hServer, int sessionId, WTS_INFO_CLASS wtsInfoClass, out System.IntPtr ppBuffer, out uint pBytesReturned);
[DllImport("wtsapi32.dll", SetLastError = true)]
static extern IntPtr WTSOpenServer([MarshalAs(UnmanagedType.LPStr)] String pServerName);
[DllImport("wtsapi32.dll")]
static extern void WTSCloseServer(IntPtr hServer);
[DllImport("wtsapi32.dll", SetLastError = true)]
static extern Int32 WTSEnumerateSessions(IntPtr hServer, [MarshalAs(UnmanagedType.U4)] Int32 Reserved, [MarshalAs(UnmanagedType.U4)] Int32 Version, ref IntPtr ppSessionInfo, [MarshalAs(UnmanagedType.U4)] ref Int32 pCount);
[DllImport("wtsapi32.dll")]
static extern void WTSFreeMemory(IntPtr pMemory);
Here is a sample implementation to lookup all the users and their sessions, and then logging off one of the user.
using System;
using System.Collections.Generic;
using System.Runtime.InteropServices;
namespace ConsoleApplication1
{
[StructLayout(LayoutKind.Sequential)]
internal struct WTS_SESSION_INFO
{
public Int32 SessionID;
[MarshalAs(UnmanagedType.LPStr)]
public String pWinStationName;
public WTS_CONNECTSTATE_CLASS State;
}
internal enum WTS_CONNECTSTATE_CLASS
{
WTSActive,
WTSConnected,
WTSConnectQuery,
WTSShadow,
WTSDisconnected,
WTSIdle,
WTSListen,
WTSReset,
WTSDown,
WTSInit
}
internal enum WTS_INFO_CLASS
{
WTSInitialProgram,
WTSApplicationName,
WTSWorkingDirectory,
WTSOEMId,
WTSSessionId,
WTSUserName,
WTSWinStationName,
WTSDomainName,
WTSConnectState,
WTSClientBuildNumber,
WTSClientName,
WTSClientDirectory,
WTSClientProductId,
WTSClientHardwareId,
WTSClientAddress,
WTSClientDisplay,
WTSClientProtocolType,
WTSIdleTime,
WTSLogonTime,
WTSIncomingBytes,
WTSOutgoingBytes,
WTSIncomingFrames,
WTSOutgoingFrames,
WTSClientInfo,
WTSSessionInfo
}
class Program
{
[DllImport("wtsapi32.dll", SetLastError = true)]
static extern bool WTSLogoffSession(IntPtr hServer, int SessionId, bool bWait);
[DllImport("Wtsapi32.dll")]
static extern bool WTSQuerySessionInformation(
System.IntPtr hServer, int sessionId, WTS_INFO_CLASS wtsInfoClass, out System.IntPtr ppBuffer, out uint pBytesReturned);
[DllImport("wtsapi32.dll", SetLastError = true)]
static extern IntPtr WTSOpenServer([MarshalAs(UnmanagedType.LPStr)] String pServerName);
[DllImport("wtsapi32.dll")]
static extern void WTSCloseServer(IntPtr hServer);
[DllImport("wtsapi32.dll", SetLastError = true)]
static extern Int32 WTSEnumerateSessions(IntPtr hServer, [MarshalAs(UnmanagedType.U4)] Int32 Reserved, [MarshalAs(UnmanagedType.U4)] Int32 Version, ref IntPtr ppSessionInfo, [MarshalAs(UnmanagedType.U4)] ref Int32 pCount);
[DllImport("wtsapi32.dll")]
static extern void WTSFreeMemory(IntPtr pMemory);
internal static List<int> GetSessionIDs(IntPtr server)
{
List<int> sessionIds = new List<int>();
IntPtr buffer = IntPtr.Zero;
int count = 0;
int retval = WTSEnumerateSessions(server, 0, 1, ref buffer, ref count);
int dataSize = Marshal.SizeOf(typeof(WTS_SESSION_INFO));
Int64 current = (int)buffer;
if (retval != 0)
{
for (int i = 0; i < count; i++)
{
WTS_SESSION_INFO si = (WTS_SESSION_INFO)Marshal.PtrToStructure((IntPtr)current, typeof(WTS_SESSION_INFO));
current += dataSize;
sessionIds.Add(si.SessionID);
}
WTSFreeMemory(buffer);
}
return sessionIds;
}
internal static bool LogOffUser(string userName, IntPtr server)
{
userName = userName.Trim().ToUpper();
List<int> sessions = GetSessionIDs(server);
Dictionary<string, int> userSessionDictionary = GetUserSessionDictionary(server, sessions);
if (userSessionDictionary.ContainsKey(userName))
return WTSLogoffSession(server, userSessionDictionary[userName], true);
else
return false;
}
private static Dictionary<string, int> GetUserSessionDictionary(IntPtr server, List<int> sessions)
{
Dictionary<string, int> userSession = new Dictionary<string, int>();
foreach (var sessionId in sessions)
{
string uName = GetUserName(sessionId, server);
if (!string.IsNullOrWhiteSpace(uName))
userSession.Add(uName, sessionId);
}
return userSession;
}
internal static string GetUserName(int sessionId, IntPtr server)
{
IntPtr buffer = IntPtr.Zero;
uint count = 0;
string userName = string.Empty;
try
{
WTSQuerySessionInformation(server, sessionId, WTS_INFO_CLASS.WTSUserName, out buffer, out count);
userName = Marshal.PtrToStringAnsi(buffer).ToUpper().Trim();
}
finally
{
WTSFreeMemory(buffer);
}
return userName;
}
static void Main(string[] args)
{
string input = string.Empty;
Console.Write("Enter ServerName<Enter 0 to default to local>:");
input = Console.ReadLine();
IntPtr server = WTSOpenServer(input.Trim()[0] == '0' ? Environment.MachineName : input.Trim());
try
{
do
{
Console.WriteLine("Please Enter L => list sessions, G => Logoff a user, END => exit.");
input = Console.ReadLine();
if (string.IsNullOrWhiteSpace(input))
continue;
else if (input.ToUpper().Trim()[0] == 'L')
{
Dictionary<string, int> userSessionDict = GetUserSessionDictionary(server, GetSessionIDs(server));
foreach (var userSession in userSessionDict)
{
Console.WriteLine(string.Format("{0} is logged in {1} session", userSession.Key, userSession.Value));
}
}
else if (input.ToUpper().Trim()[0] == 'G')
{
Console.Write("Enter UserName:");
input = Console.ReadLine();
LogOffUser(input, server);
}
} while (input.ToUpper() != "END");
}
finally
{
WTSCloseServer(server);
}
}
}
}