lib/platform/MSWindowsWatchdog.cpp

/*
 * synergy -- mouse and keyboard sharing utility
 * Copyright (C) 2012-2016 Symless Ltd.
 * Copyright (C) 2009 Chris Schoeneman
 *
 * This package is free software; you can redistribute it and/or
 * modify it under the terms of the GNU General Public License
 * found in the file LICENSE that should have accompanied this file.
 *
 * This package is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program.  If not, see <http://www.gnu.org/licenses/>.
 */

#include "platform/MSWindowsWatchdog.h"

#include "ipc/IpcLogOutputter.h"
#include "ipc/IpcServer.h"
#include "ipc/IpcMessage.h"
#include "ipc/Ipc.h"
#include "synergy/App.h"
#include "synergy/ArgsBase.h"
#include "mt/Thread.h"
#include "arch/win32/ArchDaemonWindows.h"
#include "arch/win32/XArchWindows.h"
#include "arch/Arch.h"
#include "base/log_outputters.h"
#include "base/TMethodJob.h"
#include "base/Log.h"
#include "common/Version.h"

#include <sstream>
#include <UserEnv.h>
#include <Shellapi.h>

#define CURRENT_PROCESS_ID 0
#define MAXIMUM_WAIT_TIME 3
enum {
    kOutputBufferSize = 4096
};

typedef VOID (WINAPI *SendSas)(BOOL asUser);

const char g_activeDesktop[] = {"activeDesktop:"};

MSWindowsWatchdog::MSWindowsWatchdog(
    bool autoDetectCommand,
    IpcServer& ipcServer,
    IpcLogOutputter& ipcLogOutputter,
	bool foreground) :
    m_thread(NULL),
    m_autoDetectCommand(autoDetectCommand),
    m_monitoring(true),
    m_commandChanged(false),
    m_stdOutWrite(NULL),
    m_stdOutRead(NULL),
    m_ipcServer(ipcServer),
    m_ipcLogOutputter(ipcLogOutputter),
    m_elevateProcess(false),
    m_processFailures(0),
    m_processRunning(false),
    m_fileLogOutputter(NULL),
    m_autoElevated(false),
    m_ready(false),
	m_foreground(foreground)
{
    m_mutex = ARCH->newMutex();
    m_condVar = ARCH->newCondVar();
}

MSWindowsWatchdog::~MSWindowsWatchdog()
{
    if (m_condVar != NULL) {
        ARCH->closeCondVar(m_condVar);
    }

    if (m_mutex != NULL) {
        ARCH->closeMutex(m_mutex);
    }
}

void
MSWindowsWatchdog::startAsync()
{
    m_thread = new Thread(new TMethodJob<MSWindowsWatchdog>(
        this, &MSWindowsWatchdog::mainLoop, nullptr));

    m_outputThread = new Thread(new TMethodJob<MSWindowsWatchdog>(
        this, &MSWindowsWatchdog::outputLoop, nullptr));
}

void
MSWindowsWatchdog::stop()
{
    m_monitoring = false;

    m_thread->wait(5);
    delete m_thread;

    m_outputThread->wait(5);
    delete m_outputThread;
}

HANDLE
MSWindowsWatchdog::duplicateProcessToken(HANDLE process, LPSECURITY_ATTRIBUTES security)
{
	HANDLE sourceToken;

	BOOL tokenRet = OpenProcessToken(
		process,
		TOKEN_ASSIGN_PRIMARY | TOKEN_ALL_ACCESS,
		&sourceToken);

	if (!tokenRet) {
		LOG((CLOG_ERR "could not open token, process handle: %d", process));
		throw XArch(new XArchEvalWindows());
	}

	LOG((CLOG_DEBUG "got token %i, duplicating", sourceToken));

	HANDLE newToken;
	BOOL duplicateRet = DuplicateTokenEx(
		sourceToken, TOKEN_ASSIGN_PRIMARY | TOKEN_ALL_ACCESS, security,
		SecurityImpersonation, TokenPrimary, &newToken);

	if (!duplicateRet) {
		LOG((CLOG_ERR "could not duplicate token %i", sourceToken));
		throw XArch(new XArchEvalWindows());
	}

	LOG((CLOG_DEBUG "duplicated, new token: %i", newToken));
	return newToken;
}

HANDLE
MSWindowsWatchdog::getUserToken(LPSECURITY_ATTRIBUTES security)
{
	// always elevate if we are at the vista/7 login screen. we could also
	// elevate for the uac dialog (consent.exe) but this would be pointless,
	// since synergy would re-launch as non-elevated after the desk switch,
	// and so would be unusable with the new elevated process taking focus.
	if (m_elevateProcess
		|| m_autoElevated
		|| m_session.isProcessInSession("logonui.exe", NULL)) {

		LOG((CLOG_DEBUG "getting elevated token, %s",
			(m_elevateProcess ? "elevation required" : "at login screen")));

		HANDLE process;
		if (!m_session.isProcessInSession("winlogon.exe", &process)) {
			throw XMSWindowsWatchdogError("cannot get user token without winlogon.exe");
		}

		return duplicateProcessToken(process, security);
	}
	else {
		LOG((CLOG_DEBUG "getting non-elevated token"));
		return m_session.getUserToken(security);
	}
}

void
MSWindowsWatchdog::mainLoop(void*)
{
	shutdownExistingProcesses();

	SendSas sendSasFunc = NULL;
	HINSTANCE sasLib = LoadLibrary("sas.dll");
	if (sasLib) {
		LOG((CLOG_DEBUG "found sas.dll"));
		sendSasFunc = (SendSas)GetProcAddress(sasLib, "SendSAS");
	}

	SECURITY_ATTRIBUTES saAttr;
	saAttr.nLength = sizeof(SECURITY_ATTRIBUTES);
	saAttr.bInheritHandle = TRUE;
	saAttr.lpSecurityDescriptor = NULL;

	if (!CreatePipe(&m_stdOutRead, &m_stdOutWrite, &saAttr, 0)) {
		throw XArch(new XArchEvalWindows());
	}

	ZeroMemory(&m_processInfo, sizeof(PROCESS_INFORMATION));

	while (m_monitoring) {
		try {

			if (m_processRunning && getCommand().empty()) {
				LOG((CLOG_INFO "process started but command is empty, shutting down"));
				shutdownExistingProcesses();
				m_processRunning = false;
				continue;
			}

			if (m_processFailures != 0) {
				// increasing backoff period, maximum of 10 seconds.
				int timeout = (m_processFailures * 2) < 10 ? (m_processFailures * 2) : 10;
				LOG((CLOG_INFO "backing off, wait=%ds, failures=%d", timeout, m_processFailures));
				ARCH->sleep(timeout);
			}

			if (!getCommand().empty()) {
				bool startNeeded = false;

				if (m_processFailures != 0) {
					startNeeded = true;
				}
				else if (!m_foreground && m_session.hasChanged()) {
					startNeeded = true;
				}
				else if (m_commandChanged) {
					startNeeded = true;
				}

				if (startNeeded) {
					startProcess();
				}
			}

            if (m_processRunning && !isProcessActive()) {

                m_processFailures++;
                m_processRunning = false;

                LOG((CLOG_WARN "detected application not running, pid=%d",
                    m_processInfo.dwProcessId));
            }

            if (sendSasFunc != NULL) {

                HANDLE sendSasEvent = CreateEvent(NULL, FALSE, FALSE, "Global\\SendSAS");
                if (sendSasEvent != NULL) {

                    // use SendSAS event to wait for next session (timeout 1 second).
                    if (WaitForSingleObject(sendSasEvent, 1000) == WAIT_OBJECT_0) {
                        LOG((CLOG_DEBUG "calling SendSAS"));
                        sendSasFunc(FALSE);
                    }

                    CloseHandle(sendSasEvent);
                    continue;
                }
            }

            // if the sas event failed, wait by sleeping.
            ARCH->sleep(1);

        }
        catch (std::exception& e) {
            LOG((CLOG_ERR "failed to launch, error: %s", e.what()));
            m_processFailures++;
            m_processRunning = false;
            continue;
        }
        catch (...) {
            LOG((CLOG_ERR "failed to launch, unknown error."));
            m_processFailures++;
            m_processRunning = false;
            continue;
        }
    }

    if (m_processRunning) {
        LOG((CLOG_DEBUG "terminated running process on exit"));
        shutdownProcess(m_processInfo.hProcess, m_processInfo.dwProcessId, 20);
    }

    LOG((CLOG_DEBUG "watchdog main thread finished"));
}

bool
MSWindowsWatchdog::isProcessActive()
{
    DWORD exitCode;
    GetExitCodeProcess(m_processInfo.hProcess, &exitCode);
    return exitCode == STILL_ACTIVE;
}

void
MSWindowsWatchdog::setFileLogOutputter(FileLogOutputter* outputter)
{
    m_fileLogOutputter = outputter;
}

void
MSWindowsWatchdog::startProcess()
{
    if (m_command.empty()) {
        throw XMSWindowsWatchdogError("cannot start process, command is empty");
    }

    m_commandChanged = false;

    if (m_processRunning) {
        LOG((CLOG_DEBUG "closing existing process to make way for new one"));
        shutdownProcess(m_processInfo.hProcess, m_processInfo.dwProcessId, 20);
        m_processRunning = false;
    }

	BOOL createRet;
	if (m_foreground) {
		LOG((CLOG_DEBUG "starting command in foreground"));
		createRet = startProcessInForeground(m_command);
	}
	else {
		LOG((CLOG_DEBUG "starting command as session user"));
		m_session.updateActiveSession();

		SECURITY_ATTRIBUTES sa;
		ZeroMemory(&sa, sizeof(SECURITY_ATTRIBUTES));

		getActiveDesktop(&sa);

		ZeroMemory(&sa, sizeof(SECURITY_ATTRIBUTES));
		HANDLE userToken = getUserToken(&sa);
		m_elevateProcess = m_autoElevated ? m_autoElevated : m_elevateProcess;
		m_autoElevated = false;

		// patch by Jack Zhou and Henry Tung
		// set UIAccess to fix Windows 8 GUI interaction
		DWORD uiAccess = 1;
		SetTokenInformation(userToken, TokenUIAccess, &uiAccess, sizeof(DWORD));

		createRet = startProcessAsUser(m_command, userToken, &sa);
	}

    if (!createRet) {
        LOG((CLOG_ERR "could not launch command"));
        DWORD exitCode = 0;
        GetExitCodeProcess(m_processInfo.hProcess, &exitCode);
        LOG((CLOG_ERR "exit code: %d", exitCode));
        throw XArch(new XArchEvalWindows);
    }
    else {
        // wait for program to fail.
        ARCH->sleep(1);
        if (!isProcessActive()) {
            closeProcessHandles(m_processInfo.dwProcessId);
            throw XMSWindowsWatchdogError("process immediately stopped");
        }

        m_processRunning = true;
        m_processFailures = 0;

        LOG((CLOG_DEBUG "started process, session=%i, elevated: %s, command=%s",
            m_session.getActiveSessionId(),
            m_elevateProcess ? "yes" : "no",
            m_command.c_str()));
    }
}

void
MSWindowsWatchdog::setStartupInfo(STARTUPINFO& si)
{
	ZeroMemory(&si, sizeof(STARTUPINFO));
	si.cb = sizeof(STARTUPINFO);
	si.lpDesktop = "winsta0\\Default"; // TODO: maybe this should be \winlogon if we have logonui.exe?
	si.hStdError = m_stdOutWrite;
	si.hStdOutput = m_stdOutWrite;
	si.dwFlags |= STARTF_USESTDHANDLES;
}

BOOL
MSWindowsWatchdog::startProcessInForeground(String& command)
{
	// clear, as we're reusing process info struct
	ZeroMemory(&m_processInfo, sizeof(PROCESS_INFORMATION));

	// show the console window when in foreground mode,
	// so we can close it gracefully, but minimize it
	// so it doesn't get in the way.
	STARTUPINFO si;
	setStartupInfo(si);
	si.dwFlags |= STARTF_USESHOWWINDOW;
	si.wShowWindow = SW_MINIMIZE;

	BOOL result =  CreateProcess(
		NULL, LPSTR(command.c_str()), NULL, NULL,
		TRUE, 0, NULL, NULL, &si, &m_processInfo);

    m_children.insert(std::make_pair(m_processInfo.dwProcessId, m_processInfo));

    return result;
}

BOOL
MSWindowsWatchdog::startProcessAsUser(String& command, HANDLE userToken, LPSECURITY_ATTRIBUTES sa)
{
    // clear, as we're reusing process info struct
    ZeroMemory(&m_processInfo, sizeof(PROCESS_INFORMATION));

    STARTUPINFO si;
	setStartupInfo(si);

    LPVOID environment;
    BOOL blockRet = CreateEnvironmentBlock(&environment, userToken, FALSE);
    if (!blockRet) {
        LOG((CLOG_ERR "could not create environment block"));
        throw XArch(new XArchEvalWindows);
    }

    DWORD creationFlags =
        NORMAL_PRIORITY_CLASS |
        CREATE_NO_WINDOW |
        CREATE_UNICODE_ENVIRONMENT;

    // re-launch in current active user session
    LOG((CLOG_INFO "starting new process"));
    BOOL createRet = CreateProcessAsUser(
        userToken, NULL, LPSTR(command.c_str()),
        sa, NULL, TRUE, creationFlags,
        environment, NULL, &si, &m_processInfo);

    m_children.insert(std::make_pair(m_processInfo.dwProcessId, m_processInfo));

    DestroyEnvironmentBlock(environment);
    CloseHandle(userToken);

    return createRet;
}

void
MSWindowsWatchdog::setCommand(const std::string& command, bool elevate)
{
    LOG((CLOG_INFO "service command updated"));
    m_command = command;
    m_elevateProcess = elevate;
    m_commandChanged = true;
    m_processFailures = 0;
}

std::string
MSWindowsWatchdog::getCommand() const
{
    if (!m_autoDetectCommand) {
        return m_command;
    }

    // seems like a fairly convoluted way to get the process name
    const char* launchName = App::instance().argsBase().m_pname;
    std::string args = ARCH->commandLine();

    // build up a full command line
    std::stringstream cmdTemp;
    cmdTemp << launchName << args;

    std::string cmd = cmdTemp.str();

    size_t i;
    std::string find = "--relaunch";
    while ((i = cmd.find(find)) != std::string::npos) {
        cmd.replace(i, find.length(), "");
    }

    return cmd;
}

void
MSWindowsWatchdog::outputLoop(void*)
{
    // +1 char for \0
    CHAR buffer[kOutputBufferSize + 1];

    while (m_monitoring) {

        DWORD bytesRead;
        BOOL success = ReadFile(m_stdOutRead, buffer, kOutputBufferSize, &bytesRead, NULL);

        // assume the process has gone away? slow down
        // the reads until another one turns up.
        if (!success || bytesRead == 0) {
            ARCH->sleep(1);
        }
        else {
            buffer[bytesRead] = '\0';

            testOutput(buffer);

            m_ipcLogOutputter.write(kINFO, buffer);

            if (m_fileLogOutputter != NULL) {
                m_fileLogOutputter->write(kINFO, buffer);
            }

#if SYSAPI_WIN32
			if (m_foreground) {
				// when in foreground mode (useful for debugging), send the core
				// process output to the VS debug output window.
				// we could use the MSWindowsDebugOutputter, but it's really fiddly to so,
				// and there doesn't seem to be an advantage of doing that.
				OutputDebugString(buffer);
			}
#endif
        }
    }
}

void
MSWindowsWatchdog::shutdownProcess(HANDLE handle, DWORD pid, int timeout)
{
    DWORD exitCode;
    GetExitCodeProcess(handle, &exitCode);
    if (exitCode != STILL_ACTIVE) {
        return;
    }

    IpcShutdownMessage shutdown;
    m_ipcServer.send(shutdown, kIpcClientNode);

    // wait for process to exit gracefully.
    double start = ARCH->time();
    while (true) {

        GetExitCodeProcess(handle, &exitCode);
        if (exitCode != STILL_ACTIVE) {
            // yay, we got a graceful shutdown. there should be no hook in use errors!
            LOG((CLOG_DEBUG "process %d was shutdown gracefully", pid));
            break;
        }
        else {

            double elapsed = (ARCH->time() - start);
            if (elapsed > timeout) {
                // if timeout reached, kill forcefully.
                // calling TerminateProcess on synergy is very bad!
                // it causes the hook DLL to stay loaded in some apps,
                // making it impossible to start synergy again.
                LOG((CLOG_WARN "shutdown timed out after %d secs, forcefully terminating", (int)elapsed));
                TerminateProcess(handle, kExitSuccess);
                break;
            }

            ARCH->sleep(1);
        }
    }

    closeProcessHandles(pid);
}

void
MSWindowsWatchdog::shutdownExistingProcesses()
{
    // first we need to take a snapshot of the running processes
    HANDLE snapshot = CreateToolhelp32Snapshot(TH32CS_SNAPPROCESS, CURRENT_PROCESS_ID);
    if (snapshot == INVALID_HANDLE_VALUE) {
        LOG((CLOG_ERR "could not get process snapshot"));
        throw XArch(new XArchEvalWindows);
    }

    PROCESSENTRY32 entry;
    entry.dwSize = sizeof(PROCESSENTRY32);

    // get the first process, and if we can't do that then it's
    // unlikely we can go any further
    BOOL gotEntry = Process32First(snapshot, &entry);
    if (!gotEntry) {
        LOG((CLOG_ERR "could not get first process entry"));
        throw XArch(new XArchEvalWindows);
    }

    // now just iterate until we can find winlogon.exe pid
    DWORD pid = 0;
    while (gotEntry) {

        // make sure we're not checking the system process
        if (entry.th32ProcessID != 0) {

            if (_stricmp(entry.szExeFile, "synergyc.exe") == 0 ||
                _stricmp(entry.szExeFile, "synergys.exe") == 0) {

                HANDLE handle = OpenProcess(PROCESS_ALL_ACCESS, FALSE, entry.th32ProcessID);
                shutdownProcess(handle, entry.th32ProcessID, 10);
                CloseHandle(handle);
            }
        }

        // now move on to the next entry (if we're not at the end)
        gotEntry = Process32Next(snapshot, &entry);
        if (!gotEntry) {

            DWORD err = GetLastError();
            if (err != ERROR_NO_MORE_FILES) {

                // only worry about error if it's not the end of the snapshot
                LOG((CLOG_ERR "could not get subsiquent process entry"));
                throw XArch(new XArchEvalWindows);
            }
        }
    }

    clearAllChildren();
    CloseHandle(snapshot);
    m_processRunning = false;
}

void
MSWindowsWatchdog::getActiveDesktop(LPSECURITY_ATTRIBUTES security)
{
    String installedDir = ARCH->getInstalledDirectory();
    if (!installedDir.empty()) {
        String syntoolCommand;
        syntoolCommand.append("\"").append(installedDir).append("\\").append("syntool").append("\"");
        syntoolCommand.append(" --get-active-desktop");

        m_session.updateActiveSession();
        bool elevateProcess = m_elevateProcess;
        m_elevateProcess = true;
        HANDLE userToken = getUserToken(security);
        m_elevateProcess = elevateProcess;

        BOOL createRet = startProcessAsUser(syntoolCommand, userToken, security);
        auto pid = m_processInfo.dwProcessId;
        if (!createRet) {
            DWORD rc = GetLastError();
            RevertToSelf();
        }
        else {
            LOG((CLOG_DEBUG "launched syntool to check active desktop"));
        }

        ARCH->lockMutex(m_mutex);
        int waitTime = 0;
        while (!m_ready) {
            if (waitTime >= MAXIMUM_WAIT_TIME) {
                break;
            }

            ARCH->waitCondVar(m_condVar, m_mutex, 1.0);
            waitTime++;
        }
        m_ready = false;
        ARCH->unlockMutex(m_mutex);
        closeProcessHandles(pid);
    }
}

void
MSWindowsWatchdog::testOutput(String buffer)
{
    // HACK: check standard output seems hacky.
    size_t i = buffer.find(g_activeDesktop);
    if (i != String::npos) {
        size_t s = sizeof(g_activeDesktop);
        String defaultDesktop("Default");
        String sub = buffer.substr(i + s - 1, defaultDesktop.size());
        if (sub != defaultDesktop) {
            m_autoElevated = true;
        }

        ARCH->lockMutex(m_mutex);
        m_ready = true;
        ARCH->broadcastCondVar(m_condVar);
        ARCH->unlockMutex(m_mutex);
    }
}

void MSWindowsWatchdog::closeProcessHandles(unsigned long pid, bool removeFromMap) {
    auto processInfo = m_children.find(pid);
    if (processInfo != m_children.end()) {
        CloseHandle(processInfo->second.hProcess);
        CloseHandle(processInfo->second.hThread);
        if(removeFromMap) {
            m_children.erase(processInfo);
        }
    }
}

void MSWindowsWatchdog::clearAllChildren() {
    for (auto it = m_children.begin(); it != m_children.end(); ++it)
    {
        closeProcessHandles(it->second.dwThreadId, false);
    }
    m_children.clear();
}