barrier/src/lib/platform/MSWindowsSession.cpp

/*
 * barrier -- mouse and keyboard sharing utility
 * Copyright (C) 2013-2016 Symless Ltd.
 * 
 * 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/MSWindowsSession.h"

#include "arch/win32/XArchWindows.h"
#include "barrier/XBarrier.h"
#include "base/Log.h"

#include <Wtsapi32.h>

MSWindowsSession::MSWindowsSession() :
    m_activeSessionId(-1)
{
}

MSWindowsSession::~MSWindowsSession()
{
}

bool
MSWindowsSession::isProcessInSession(const char* name, PHANDLE process = NULL)
{
    // first we need to take a snapshot of the running processes
    HANDLE snapshot = CreateToolhelp32Snapshot(TH32CS_SNAPPROCESS, 0);
    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());
    }

    // used to record process names for debug info
    std::list<std::string> nameList;

    // 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) {

            DWORD processSessionId;
            BOOL pidToSidRet = ProcessIdToSessionId(
                entry.th32ProcessID, &processSessionId);

            if (!pidToSidRet) {
                // if we can not acquire session associated with a specified process,
                // simply ignore it
                LOG((CLOG_ERR "could not get session id for process id %i", entry.th32ProcessID));
                gotEntry = nextProcessEntry(snapshot, &entry);
                continue;
            }
            else {
                // only pay attention to processes in the active session
                if (processSessionId == m_activeSessionId) {

                    // store the names so we can record them for debug
                    nameList.push_back(entry.szExeFile);

                    if (_stricmp(entry.szExeFile, name) == 0) {
                        pid = entry.th32ProcessID;
                    }
                }
            }

        }

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

    std::string nameListJoin;
    for(std::list<std::string>::iterator it = nameList.begin();
        it != nameList.end(); it++) {
            nameListJoin.append(*it);
            nameListJoin.append(", ");
    }

    LOG((CLOG_DEBUG "processes in session %d: %s",
        m_activeSessionId, nameListJoin.c_str()));

    CloseHandle(snapshot);

    if (pid) {
        if (process != NULL) {
            // now get the process, which we'll use to get the process token.
            LOG((CLOG_DEBUG "found %s in session %i", name, m_activeSessionId));
            *process = OpenProcess(MAXIMUM_ALLOWED, FALSE, pid);
        }
        return true;
    }
    else {
        LOG((CLOG_DEBUG "did not find %s in session %i", name, m_activeSessionId));
        return false;
    }
}

HANDLE 
MSWindowsSession::getUserToken(LPSECURITY_ATTRIBUTES security)
{
    HANDLE sourceToken;
    if (!WTSQueryUserToken(m_activeSessionId, &sourceToken)) {
        LOG((CLOG_ERR "could not get token from session %d", m_activeSessionId));
        throw XArch(new XArchEvalWindows);
    }
    
    HANDLE newToken;
    if (!DuplicateTokenEx(
        sourceToken, TOKEN_ASSIGN_PRIMARY | TOKEN_ALL_ACCESS, security,
        SecurityImpersonation, TokenPrimary, &newToken)) {

        LOG((CLOG_ERR "could not duplicate token"));
        throw XArch(new XArchEvalWindows);
    }
    
    LOG((CLOG_DEBUG "duplicated, new token: %i", newToken));
    return newToken;
}

BOOL
MSWindowsSession::hasChanged()
{
    return (m_activeSessionId != WTSGetActiveConsoleSessionId());
}

void
MSWindowsSession::updateActiveSession()
{
    m_activeSessionId = WTSGetActiveConsoleSessionId();
}


BOOL
MSWindowsSession::nextProcessEntry(HANDLE snapshot, LPPROCESSENTRY32 entry)
{
    BOOL 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 next process entry"));
            throw XArch(new XArchEvalWindows());
        }
    }

    return gotEntry;
}

std::string MSWindowsSession::getActiveDesktopName()
{
    std::string result;
    try {
        HDESK hd = OpenInputDesktop(0, TRUE, GENERIC_READ);
        if (hd != NULL) {
            DWORD size;
            GetUserObjectInformation(hd, UOI_NAME, NULL, 0, &size);
            TCHAR* name = (TCHAR*)alloca(size + sizeof(TCHAR));
            GetUserObjectInformation(hd, UOI_NAME, name, size, &size);
            result = name;
            CloseDesktop(hd);
        }
    }
    catch (std::exception& error) {
        LOG((CLOG_ERR "failed to get active desktop name: %s", error.what()));
    }

    return result;
}