nss: upgrade to release 3.73

[LibreOffice.git] / onlineupdate / source / update / common / updatehelper.cxx

/* This Source Code Form is subject to the terms of the Mozilla Public
 * License, v. 2.0. If a copy of the MPL was not distributed with this
 * file, You can obtain one at http://mozilla.org/MPL/2.0/. */

#ifdef _WIN32
#include <windows.h>

// Needed for CreateToolhelp32Snapshot
#include <tlhelp32.h>
#ifndef ONLY_SERVICE_LAUNCHING

#include <stdio.h>
#include "shlobj.h"
#include "updatehelper.h"
#include "uachelper.h"
#include "pathhash.h"

#include <memory>

// Needed for PathAppendW
#include <shlwapi.h>

BOOL PathAppendSafe(LPWSTR base, LPCWSTR extra);

/**
 * Obtains the path of a file in the same directory as the specified file.
 *
 * @param  destinationBuffer A buffer of size MAX_PATH + 1 to store the result.
 * @param  siblingFIlePath   The path of another file in the same directory
 * @param  newFileName       The filename of another file in the same directory
 * @return TRUE if successful
 */
BOOL
PathGetSiblingFilePath(LPWSTR destinationBuffer,
                       LPCWSTR siblingFilePath,
                       LPCWSTR newFileName)
{
    if (wcslen(siblingFilePath) >= MAX_PATH)
    {
        return FALSE;
    }

    wcsncpy(destinationBuffer, siblingFilePath, MAX_PATH);
    if (!PathRemoveFileSpecW(destinationBuffer))
    {
        return FALSE;
    }

    if (wcslen(destinationBuffer) + wcslen(newFileName) >= MAX_PATH)
    {
        return FALSE;
    }

    return PathAppendSafe(destinationBuffer, newFileName);
}

/**
 * Launch the post update application as the specified user (helper.exe).
 * It takes in the path of the callback application to calculate the path
 * of helper.exe.  For service updates this is called from both the system
 * account and the current user account.
 *
 * @param  installationDir The path to the callback application binary.
 * @param  updateInfoDir   The directory where update info is stored.
 * @param  forceSync       If true even if the ini file specifies async, the
 *                         process will wait for termination of PostUpdate.
 * @param  userToken       The user token to run as, if nullptr the current
 *                         user will be used.
 * @return TRUE if there was no error starting the process.
 */
BOOL
LaunchWinPostProcess(const WCHAR *installationDir,
                     const WCHAR *updateInfoDir,
                     bool forceSync,
                     HANDLE userToken)
{
    WCHAR workingDirectory[MAX_PATH + 1] = { L'\0' };
    wcsncpy(workingDirectory, installationDir, MAX_PATH);

    // Launch helper.exe to perform post processing (e.g. registry and log file
    // modifications) for the update.
    WCHAR inifile[MAX_PATH + 1] = { L'\0' };
    wcsncpy(inifile, installationDir, MAX_PATH);
    if (!PathAppendSafe(inifile, L"updater.ini"))
    {
        return FALSE;
    }

    WCHAR exefile[MAX_PATH + 1];
    WCHAR exearg[MAX_PATH + 1];
    WCHAR exeasync[10];
    bool async = true;
    if (!GetPrivateProfileStringW(L"PostUpdateWin", L"ExeRelPath", nullptr,
                                  exefile, MAX_PATH + 1, inifile))
    {
        return FALSE;
    }

    if (!GetPrivateProfileStringW(L"PostUpdateWin", L"ExeArg", nullptr, exearg,
                                  MAX_PATH + 1, inifile))
    {
        return FALSE;
    }

    if (!GetPrivateProfileStringW(L"PostUpdateWin", L"ExeAsync", L"TRUE",
                                  exeasync,
                                  sizeof(exeasync)/sizeof(exeasync[0]),
                                  inifile))
    {
        return FALSE;
    }

    WCHAR exefullpath[MAX_PATH + 1] = { L'\0' };
    wcsncpy(exefullpath, installationDir, MAX_PATH);
    if (!PathAppendSafe(exefullpath, exefile))
    {
        return false;
    }

    WCHAR dlogFile[MAX_PATH + 1];
    if (!PathGetSiblingFilePath(dlogFile, exefullpath, L"uninstall.update"))
    {
        return FALSE;
    }

    WCHAR slogFile[MAX_PATH + 1] = { L'\0' };
    wcsncpy(slogFile, updateInfoDir, MAX_PATH);
    if (!PathAppendSafe(slogFile, L"update.log"))
    {
        return FALSE;
    }

    WCHAR dummyArg[14] = { L'\0' };
    wcsncpy(dummyArg, L"argv0ignored ", sizeof(dummyArg) / sizeof(dummyArg[0]) - 1);

    size_t len = wcslen(exearg) + wcslen(dummyArg);
    WCHAR *cmdline = (WCHAR *) malloc((len + 1) * sizeof(WCHAR));
    if (!cmdline)
    {
        return FALSE;
    }

    wcsncpy(cmdline, dummyArg, len);
    wcscat(cmdline, exearg);

    if (forceSync ||
            !_wcsnicmp(exeasync, L"false", 6) ||
            !_wcsnicmp(exeasync, L"0", 2))
    {
        async = false;
    }

    // We want to launch the post update helper app to update the Windows
    // registry even if there is a failure with removing the uninstall.update
    // file or copying the update.log file.
    CopyFileW(slogFile, dlogFile, false);

    STARTUPINFOW si = {sizeof(si), 0};
    si.lpDesktop = L"";
    PROCESS_INFORMATION pi = {0};

    bool ok;
    if (userToken)
    {
        ok = CreateProcessAsUserW(userToken,
                                  exefullpath,
                                  cmdline,
                                  nullptr,  // no special security attributes
                                  nullptr,  // no special thread attributes
                                  false,    // don't inherit filehandles
                                  0,        // No special process creation flags
                                  nullptr,  // inherit my environment
                                  workingDirectory,
                                  &si,
                                  &pi);
    }
    else
    {
        ok = CreateProcessW(exefullpath,
                            cmdline,
                            nullptr,  // no special security attributes
                            nullptr,  // no special thread attributes
                            false,    // don't inherit filehandles
                            0,        // No special process creation flags
                            nullptr,  // inherit my environment
                            workingDirectory,
                            &si,
                            &pi);
    }
    free(cmdline);
    if (ok)
    {
        if (!async)
            WaitForSingleObject(pi.hProcess, INFINITE);
        CloseHandle(pi.hProcess);
        CloseHandle(pi.hThread);
    }
    return ok;
}

/**
 * Starts the upgrade process for update of the service if it is
 * already installed.
 *
 * @param  installDir the installation directory where
 *         maintenanceservice_installer.exe is located.
 * @return TRUE if successful
 */
BOOL
StartServiceUpdate(LPCWSTR installDir)
{
    // Get a handle to the local computer SCM database
    SC_HANDLE manager = OpenSCManager(nullptr, nullptr,
                                      SC_MANAGER_ALL_ACCESS);
    if (!manager)
    {
        return FALSE;
    }

    // Open the service
    SC_HANDLE svc = OpenServiceW(manager, SVC_NAME,
                                 SERVICE_ALL_ACCESS);
    if (!svc)
    {
        CloseServiceHandle(manager);
        return FALSE;
    }

    // If we reach here, then the service is installed, so
    // proceed with upgrading it.

    CloseServiceHandle(manager);

    // The service exists and we opened it, get the config bytes needed
    DWORD bytesNeeded;
    if (!QueryServiceConfigW(svc, nullptr, 0, &bytesNeeded) &&
            GetLastError() != ERROR_INSUFFICIENT_BUFFER)
    {
        CloseServiceHandle(svc);
        return FALSE;
    }

    // Get the service config information, in particular we want the binary
    // path of the service.
    std::unique_ptr<char[]> serviceConfigBuffer = std::make_unique<char[]>(bytesNeeded);
    if (!QueryServiceConfigW(svc,
                             reinterpret_cast<QUERY_SERVICE_CONFIGW*>(serviceConfigBuffer.get()),
                             bytesNeeded, &bytesNeeded))
    {
        CloseServiceHandle(svc);
        return FALSE;
    }

    CloseServiceHandle(svc);

    QUERY_SERVICE_CONFIGW &serviceConfig =
        *reinterpret_cast<QUERY_SERVICE_CONFIGW*>(serviceConfigBuffer.get());

    PathUnquoteSpacesW(serviceConfig.lpBinaryPathName);

    // Obtain the temp path of the maintenance service binary
    WCHAR tmpService[MAX_PATH + 1] = { L'\0' };
    if (!PathGetSiblingFilePath(tmpService, serviceConfig.lpBinaryPathName,
                                L"maintenanceservice_tmp.exe"))
    {
        return FALSE;
    }

    // Get the new maintenance service path from the install dir
    WCHAR newMaintServicePath[MAX_PATH + 1] = { L'\0' };
    wcsncpy(newMaintServicePath, installDir, MAX_PATH);
    PathAppendSafe(newMaintServicePath,
                   L"maintenanceservice.exe");

    // Copy the temp file in alongside the maintenance service.
    // This is a requirement for maintenance service upgrades.
    if (!CopyFileW(newMaintServicePath, tmpService, FALSE))
    {
        return FALSE;
    }

    // Start the upgrade comparison process
    STARTUPINFOW si = {0};
    si.cb = sizeof(STARTUPINFOW);
    // No particular desktop because no UI
    si.lpDesktop = L"";
    PROCESS_INFORMATION pi = {0};
    WCHAR cmdLine[64] = { '\0' };
    wcsncpy(cmdLine, L"dummyparam.exe upgrade",
            sizeof(cmdLine) / sizeof(cmdLine[0]) - 1);
    BOOL svcUpdateProcessStarted = CreateProcessW(tmpService,
                                   cmdLine,
                                   nullptr, nullptr, FALSE,
                                   0,
                                   nullptr, installDir, &si, &pi);
    if (svcUpdateProcessStarted)
    {
        CloseHandle(pi.hProcess);
        CloseHandle(pi.hThread);
    }
    return svcUpdateProcessStarted;
}

#endif

/**
 * Executes a maintenance service command
 *
 * @param  argc    The total number of arguments in argv
 * @param  argv    An array of null terminated strings to pass to the service,
 * @return ERROR_SUCCESS if the service command was started.
 *         Less than 16000, a windows system error code from StartServiceW
 *         More than 20000, 20000 + the last state of the service constant if
 *         the last state is something other than stopped.
 *         17001 if the SCM could not be opened
 *         17002 if the service could not be opened
*/
DWORD
StartServiceCommand(int argc, LPCWSTR* argv)
{
    DWORD lastState = WaitForServiceStop(SVC_NAME, 5);
    if (lastState != SERVICE_STOPPED)
    {
        return 20000 + lastState;
    }

    // Get a handle to the SCM database.
    SC_HANDLE serviceManager = OpenSCManager(nullptr, nullptr,
                               SC_MANAGER_CONNECT |
                               SC_MANAGER_ENUMERATE_SERVICE);
    if (!serviceManager)
    {
        return 17001;
    }

    // Get a handle to the service.
    SC_HANDLE service = OpenServiceW(serviceManager,
                                     SVC_NAME,
                                     SERVICE_START);
    if (!service)
    {
        CloseServiceHandle(serviceManager);
        return 17002;
    }

    // Wait at most 5 seconds trying to start the service in case of errors
    // like ERROR_SERVICE_DATABASE_LOCKED or ERROR_SERVICE_REQUEST_TIMEOUT.
    const DWORD maxWaitMS = 5000;
    DWORD currentWaitMS = 0;
    DWORD lastError = ERROR_SUCCESS;
    while (currentWaitMS < maxWaitMS)
    {
        BOOL result = StartServiceW(service, argc, argv);
        if (result)
        {
            lastError = ERROR_SUCCESS;
            break;
        }
        else
        {
            lastError = GetLastError();
        }
        Sleep(100);
        currentWaitMS += 100;
    }
    CloseServiceHandle(service);
    CloseServiceHandle(serviceManager);
    return lastError;
}

#ifndef ONLY_SERVICE_LAUNCHING

/**
 * Launch a service initiated action for a software update with the
 * specified arguments.
 *
 * @param  exePath The path of the executable to run
 * @param  argc    The total number of arguments in argv
 * @param  argv    An array of null terminated strings to pass to the exePath,
 *                 argv[0] must be the path to the updater.exe
 * @return ERROR_SUCCESS if successful
 */
DWORD
LaunchServiceSoftwareUpdateCommand(int argc, LPCWSTR* argv)
{
    // The service command is the same as the updater.exe command line except
    // it has 2 extra args: 1) The Path to updater.exe, and 2) the command
    // being executed which is "software-update"
    LPCWSTR *updaterServiceArgv = new LPCWSTR[argc + 2];
    updaterServiceArgv[0] = L"MozillaMaintenance";
    updaterServiceArgv[1] = L"software-update";

    for (int i = 0; i < argc; ++i)
    {
        updaterServiceArgv[i + 2] = argv[i];
    }

    // Execute the service command by starting the service with
    // the passed in arguments.
    DWORD ret = StartServiceCommand(argc + 2, updaterServiceArgv);
    delete[] updaterServiceArgv;
    return ret;
}

/**
 * Joins a base directory path with a filename.
 *
 * @param  base  The base directory path of size MAX_PATH + 1
 * @param  extra The filename to append
 * @return TRUE if the file name was successful appended to base
 */
BOOL
PathAppendSafe(LPWSTR base, LPCWSTR extra)
{
    if (wcslen(base) + wcslen(extra) >= MAX_PATH)
    {
        return FALSE;
    }

    return PathAppendW(base, extra);
}

/**
 * Sets update.status to pending so that the next startup will not use
 * the service and instead will attempt an update the with a UAC prompt.
 *
 * @param  updateDirPath The path of the update directory
 * @return TRUE if successful
 */
BOOL
WriteStatusPending(LPCWSTR updateDirPath)
{
    WCHAR updateStatusFilePath[MAX_PATH + 1] = { L'\0' };
    wcsncpy(updateStatusFilePath, updateDirPath, MAX_PATH);
    if (!PathAppendSafe(updateStatusFilePath, L"update.status"))
    {
        return FALSE;
    }

    const char pending[] = "pending";
    HANDLE statusFile = CreateFileW(updateStatusFilePath, GENERIC_WRITE, 0,
                                    nullptr, CREATE_ALWAYS, 0, nullptr);
    if (statusFile == INVALID_HANDLE_VALUE)
    {
        return FALSE;
    }

    DWORD wrote;
    BOOL ok = WriteFile(statusFile, pending,
                        sizeof(pending) - 1, &wrote, nullptr);
    CloseHandle(statusFile);
    return ok && (wrote == sizeof(pending) - 1);
}

/**
 * Sets update.status to a specific failure code
 *
 * @param  updateDirPath The path of the update directory
 * @return TRUE if successful
 */
BOOL
WriteStatusFailure(LPCWSTR updateDirPath, int errorCode)
{
    WCHAR updateStatusFilePath[MAX_PATH + 1] = { L'\0' };
    wcsncpy(updateStatusFilePath, updateDirPath, MAX_PATH);
    if (!PathAppendSafe(updateStatusFilePath, L"update.status"))
    {
        return FALSE;
    }

    HANDLE statusFile = CreateFileW(updateStatusFilePath, GENERIC_WRITE, 0,
                                    nullptr, CREATE_ALWAYS, 0, nullptr);
    if (statusFile == INVALID_HANDLE_VALUE)
    {
        return FALSE;
    }
    char failure[32];
    sprintf(failure, "failed: %d", errorCode);

    DWORD toWrite = strlen(failure);
    DWORD wrote;
    BOOL ok = WriteFile(statusFile, failure,
                        toWrite, &wrote, nullptr);
    CloseHandle(statusFile);
    return ok && wrote == toWrite;
}

#endif

/**
 * Waits for a service to enter a stopped state.
 * This function does not stop the service, it just blocks until the service
 * is stopped.
 *
 * @param  serviceName     The service to wait for.
 * @param  maxWaitSeconds  The maximum number of seconds to wait
 * @return state of the service after a timeout or when stopped.
 *         A value of 255 is returned for an error. Typical values are:
 *         SERVICE_STOPPED 0x00000001
 *         SERVICE_START_PENDING 0x00000002
 *         SERVICE_STOP_PENDING 0x00000003
 *         SERVICE_RUNNING 0x00000004
 *         SERVICE_CONTINUE_PENDING 0x00000005
 *         SERVICE_PAUSE_PENDING 0x00000006
 *         SERVICE_PAUSED 0x00000007
 *         last status not set 0x000000CF
 *         Could no query status 0x000000DF
 *         Could not open service, access denied 0x000000EB
 *         Could not open service, invalid handle 0x000000EC
 *         Could not open service, invalid name 0x000000ED
 *         Could not open service, does not exist 0x000000EE
 *         Could not open service, other error 0x000000EF
 *         Could not open SCM, access denied 0x000000FD
 *         Could not open SCM, database does not exist 0x000000FE;
 *         Could not open SCM, other error 0x000000FF;
 * Note: The strange choice of error codes above SERVICE_PAUSED are chosen
 * in case Windows comes out with other service stats higher than 7, they
 * would likely call it 8 and above.  JS code that uses this in TestAUSHelper
 * only handles values up to 255 so that's why we don't use GetLastError
 * directly.
 */
DWORD
WaitForServiceStop(LPCWSTR serviceName, DWORD maxWaitSeconds)
{
    // 0x000000CF is defined above to be not set
    DWORD lastServiceState = 0x000000CF;

    // Get a handle to the SCM database.
    SC_HANDLE serviceManager = OpenSCManager(nullptr, nullptr,
                               SC_MANAGER_CONNECT |
                               SC_MANAGER_ENUMERATE_SERVICE);
    if (!serviceManager)
    {
        DWORD lastError = GetLastError();
        switch (lastError)
        {
            case ERROR_ACCESS_DENIED:
                return 0x000000FD;
            case ERROR_DATABASE_DOES_NOT_EXIST:
                return 0x000000FE;
            default:
                return 0x000000FF;
        }
    }

    // Get a handle to the service.
    SC_HANDLE service = OpenServiceW(serviceManager,
                                     serviceName,
                                     SERVICE_QUERY_STATUS);
    if (!service)
    {
        DWORD lastError = GetLastError();
        CloseServiceHandle(serviceManager);
        switch (lastError)
        {
            case ERROR_ACCESS_DENIED:
                return 0x000000EB;
            case ERROR_INVALID_HANDLE:
                return 0x000000EC;
            case ERROR_INVALID_NAME:
                return 0x000000ED;
            case ERROR_SERVICE_DOES_NOT_EXIST:
                return 0x000000EE;
            default:
                return 0x000000EF;
        }
    }

    DWORD currentWaitMS = 0;
    SERVICE_STATUS_PROCESS ssp;
    ssp.dwCurrentState = lastServiceState;
    while (currentWaitMS < maxWaitSeconds * 1000)
    {
        DWORD bytesNeeded;
        if (!QueryServiceStatusEx(service, SC_STATUS_PROCESS_INFO, (LPBYTE)&ssp,
                                  sizeof(SERVICE_STATUS_PROCESS), &bytesNeeded))
        {
            DWORD lastError = GetLastError();
            switch (lastError)
            {
                case ERROR_INVALID_HANDLE:
                    ssp.dwCurrentState = 0x000000D9;
                    break;
                case ERROR_ACCESS_DENIED:
                    ssp.dwCurrentState = 0x000000DA;
                    break;
                case ERROR_INSUFFICIENT_BUFFER:
                    ssp.dwCurrentState = 0x000000DB;
                    break;
                case ERROR_INVALID_PARAMETER:
                    ssp.dwCurrentState = 0x000000DC;
                    break;
                case ERROR_INVALID_LEVEL:
                    ssp.dwCurrentState = 0x000000DD;
                    break;
                case ERROR_SHUTDOWN_IN_PROGRESS:
                    ssp.dwCurrentState = 0x000000DE;
                    break;
                // These 3 errors can occur when the service is not yet stopped but
                // it is stopping.
                case ERROR_INVALID_SERVICE_CONTROL:
                case ERROR_SERVICE_CANNOT_ACCEPT_CTRL:
                case ERROR_SERVICE_NOT_ACTIVE:
                    currentWaitMS += 50;
                    Sleep(50);
                    continue;
                default:
                    ssp.dwCurrentState = 0x000000DF;
            }

            // We couldn't query the status so just break out
            break;
        }

        // The service is already in use.
        if (ssp.dwCurrentState == SERVICE_STOPPED)
        {
            break;
        }
        currentWaitMS += 50;
        Sleep(50);
    }

    lastServiceState = ssp.dwCurrentState;
    CloseServiceHandle(service);
    CloseServiceHandle(serviceManager);
    return lastServiceState;
}

#ifndef ONLY_SERVICE_LAUNCHING

/**
 * Determines if there is at least one process running for the specified
 * application. A match will be found across any session for any user.
 *
 * @param process The process to check for existence
 * @return ERROR_NOT_FOUND if the process was not found
 *         ERROR_SUCCESS if the process was found and there were no errors
 *         Other Win32 system error code for other errors
**/
DWORD
IsProcessRunning(LPCWSTR filename)
{
    // Take a snapshot of all processes in the system.
    HANDLE snapshot = CreateToolhelp32Snapshot(TH32CS_SNAPPROCESS, 0);
    if (INVALID_HANDLE_VALUE == snapshot)
    {
        return GetLastError();
    }

    PROCESSENTRY32W processEntry;
    processEntry.dwSize = sizeof(PROCESSENTRY32W);
    if (!Process32FirstW(snapshot, &processEntry))
    {
        DWORD lastError = GetLastError();
        CloseHandle(snapshot);
        return lastError;
    }

    do
    {
        if (wcsicmp(filename, processEntry.szExeFile) == 0)
        {
            CloseHandle(snapshot);
            return ERROR_SUCCESS;
        }
    }
    while (Process32NextW(snapshot, &processEntry));
    CloseHandle(snapshot);
    return ERROR_NOT_FOUND;
}

/**
 * Waits for the specified application to exit.
 *
 * @param filename   The application to wait for.
 * @param maxSeconds The maximum amount of seconds to wait for all
 *                   instances of the application to exit.
 * @return  ERROR_SUCCESS if no instances of the application exist
 *          WAIT_TIMEOUT if the process is still running after maxSeconds.
 *          Any other Win32 system error code.
*/
DWORD
WaitForProcessExit(LPCWSTR filename, DWORD maxSeconds)
{
    DWORD applicationRunningError = WAIT_TIMEOUT;
    for (DWORD i = 0; i < maxSeconds; i++)
    {
        applicationRunningError = IsProcessRunning(filename);
        if (ERROR_NOT_FOUND == applicationRunningError)
        {
            return ERROR_SUCCESS;
        }
        Sleep(1000);
    }

    if (ERROR_SUCCESS == applicationRunningError)
    {
        return WAIT_TIMEOUT;
    }

    return applicationRunningError;
}

/**
 *  Determines if the fallback key exists or not
 *
 *  @return TRUE if the fallback key exists and there was no error checking
*/
BOOL
DoesFallbackKeyExist()
{
    HKEY testOnlyFallbackKey;
    if (RegOpenKeyExW(HKEY_LOCAL_MACHINE,
                      TEST_ONLY_FALLBACK_KEY_PATH, 0,
                      KEY_READ | KEY_WOW64_64KEY,
                      &testOnlyFallbackKey) != ERROR_SUCCESS)
    {
        return FALSE;
    }

    RegCloseKey(testOnlyFallbackKey);
    return TRUE;
}

#endif

/**
 * Determines if the file system for the specified file handle is local
 * @param file path to check the filesystem type for, must be at most MAX_PATH
 * @param isLocal out parameter which will hold TRUE if the drive is local
 * @return TRUE if the call succeeded
*/
BOOL
IsLocalFile(LPCWSTR file, BOOL &isLocal)
{
    WCHAR rootPath[MAX_PATH + 1] = { L'\0' };
    if (wcslen(file) > MAX_PATH)
    {
        return FALSE;
    }

    wcsncpy(rootPath, file, MAX_PATH);
    PathStripToRootW(rootPath);
    isLocal = GetDriveTypeW(rootPath) == DRIVE_FIXED;
    return TRUE;
}


/**
 * Determines the DWORD value of a registry key value
 *
 * @param key       The base key to where the value name exists
 * @param valueName The name of the value
 * @param retValue  Out parameter which will hold the value
 * @return TRUE on success
*/
static BOOL
GetDWORDValue(HKEY key, LPCWSTR valueName, DWORD &retValue)
{
    DWORD regDWORDValueSize = sizeof(DWORD);
    LONG retCode = RegQueryValueExW(key, valueName, 0, nullptr,
                                    reinterpret_cast<LPBYTE>(&retValue),
                                    &regDWORDValueSize);
    return ERROR_SUCCESS == retCode;
}

/**
 * Determines if the system's elevation type allows
 * unprompted elevation.
 *
 * @param isUnpromptedElevation Out parameter which specifies if unprompted
 *                              elevation is allowed.
 * @return TRUE if the user can actually elevate and the value was obtained
 *         successfully.
*/
BOOL
IsUnpromptedElevation(BOOL &isUnpromptedElevation)
{
    if (!UACHelper::CanUserElevate())
    {
        return FALSE;
    }

    LPCWSTR UACBaseRegKey =
        L"SOFTWARE\\Microsoft\\Windows\\CurrentVersion\\Policies\\System";
    HKEY baseKey;
    LONG retCode = RegOpenKeyExW(HKEY_LOCAL_MACHINE,
                                 UACBaseRegKey, 0,
                                 KEY_READ, &baseKey);
    if (retCode != ERROR_SUCCESS)
    {
        return FALSE;
    }

    DWORD consent;
    DWORD secureDesktop = 0;
    BOOL success = GetDWORDValue(baseKey, L"ConsentPromptBehaviorAdmin",
                                 consent);
    success = success &&
              GetDWORDValue(baseKey, L"PromptOnSecureDesktop", secureDesktop);
    isUnpromptedElevation = !consent && !secureDesktop;

    RegCloseKey(baseKey);
    return success;
}
#endif