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// Copyright 2005-2019 The Mumble Developers. All rights reserved.
// Use of this source code is governed by a BSD-style license
// that can be found in the LICENSE file at the root of the
// Mumble source tree or at <https://www.mumble.info/LICENSE>.
#include "win.h"
#include <string>
#include <shlwapi.h>
#include <stdio.h>
#include <sddl.h>
// Alert shows a fatal error dialog and waits for the user to click OK.
static void Alert(LPCWSTR title, LPCWSTR msg) {
MessageBox(NULL, msg, title, MB_OK|MB_ICONERROR);
}
// GetExecutablePath returns the path to mumble.exe.
static const std::wstring GetExecutablePath() {
wchar_t path[MAX_PATH];
if (GetModuleFileNameW(NULL, path, MAX_PATH) == 0)
return std::wstring();
std::wstring exe_path(path);
return exe_path;
}
// UIAccessDisabledViaConfig queries the configuration store, and returns
// whether UIAccess has been disabled by the user via the
// "shortcut/windows/uiaccess/enable" config option.
static bool UIAccessDisabledViaConfig() {
// RegQueryValueEx only zero-terminates if the registry value's type is
// one of the Windows registry's string types. Because of this, we have
// to use a buffer of 7 elements in order to query for the string "false".
//
// If the value's type is string, we'll end up with "false\0\0", because we
// always zero-pad.
//
// But that's better than ending up in an infinite loop because we failed
// to zero-terminate.
wchar_t buf[7];
memset(&buf, 0, sizeof(buf));
DWORD sz = sizeof(buf) - 1*sizeof(wchar_t);
HKEY key = NULL;
bool success = (RegOpenKeyExW(HKEY_CURRENT_USER, L"Software\\Mumble\\Mumble\\shortcut\\windows\\uiaccess", 0, KEY_READ, &key) == ERROR_SUCCESS) &&
(RegQueryValueExW(key, L"enable" , NULL, NULL, (LPBYTE)&buf, &sz) == ERROR_SUCCESS);
if (success && _wcsicmp(buf, L"false") == 0) {
return true;
}
return false;
}
// ProcessHasUIAccess returns true if the current process has UIAccess enabled.
static bool ProcessHasUIAccess() {
HANDLE token = NULL;
if (!OpenProcessToken(GetCurrentProcess(), TOKEN_QUERY, &token)) {
return false;
}
DWORD ui_access = 0;
DWORD ui_access_size = sizeof(ui_access);
if (!GetTokenInformation(token, TokenUIAccess, &ui_access, sizeof(ui_access), &ui_access_size)) {
CloseHandle(token);
return false;
}
CloseHandle(token);
return ui_access != 0;
}
// RelaunchWithoutUIAccessIfNecessary relaunches the process
// without UIAccess, if necessary.
//
// If a relaunch of Mumble is necessary, the new process is
// spawned and the existing process is terminated. In that
// situation, this function will not return to the caller.
static bool RelaunchWithoutUIAccessIfNecessary() {
if (!ProcessHasUIAccess()) {
return true;
}
if (!UIAccessDisabledViaConfig()) {
return true;
}
STARTUPINFO startup_info;
memset(&startup_info, 0, sizeof(startup_info));
GetStartupInfo(&startup_info);
PROCESS_INFORMATION process_info;
memset(&process_info, 0, sizeof(process_info));
// Store the original value of __COMPAT_LAYER so we can
// restore it (which may be equivalent to not setting it all)
// once we've been relaunched.
const wchar_t *compat_layer_env = _wgetenv(L"__COMPAT_LAYER");
if (compat_layer_env == NULL) {
compat_layer_env = L"mumble_exe_none";
}
_wputenv_s(L"mumble_exe_prev_compat_layer", compat_layer_env);
// The only way we have found thus far to ignore the executable's
// manifest when calling CreateProcess, is to use the __COMPAT_LAYER
// environment variable.
//
// Setting this to RunAsInvoker seemingly ignores the application's
// manifest. RunAsInvoker is the default execution level for Windows
// programs.
_wputenv_s(L"__COMPAT_LAYER", L"RunAsInvoker");
std::wstring exe_path = GetExecutablePath();
if (exe_path.empty()) {
return false;
}
if (!CreateProcessW(exe_path.c_str(),
GetCommandLineW(),
NULL,
NULL,
FALSE,
0,
NULL,
NULL,
&startup_info,
&process_info)) {
return false;
}
exit(0);
}
// CleanupEnvironmentVariables cleans up any
// unnecessary environment variables.
//
// For now, this function cleans up any environment
// variables set by RelaunchWithoutUIAccessIfNecessary.
static void CleanupEnvironmentVariables() {
wchar_t *prev_compat_layer_env = _wgetenv(L"mumble_exe_prev_compat_layer");
if (prev_compat_layer_env != NULL) {
if (wcscmp(prev_compat_layer_env, L"mumble_exe_none") == 0) {
_wputenv_s(L"__COMPAT_LAYER", L"");
} else {
_wputenv_s(L"__COMPAT_LAYER", prev_compat_layer_env);
}
}
}
int os_early_init() {
CleanupEnvironmentVariables();
if (!RelaunchWithoutUIAccessIfNecessary()) {
Alert(L"Mumble Early Init Error 50", L"Unable to complete RelaunchWithoutUIAccessIfNecessary");
return 50;
}
return 0;
}
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