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/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
/* vim: set ts=8 sts=2 et sw=2 tw=80: */
/* 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 */
#include "nsAnonymousTemporaryFile.h"
#include "nsXULAppAPI.h"
#include "nsCOMPtr.h"
#include "nsString.h"
#include "prio.h"
#include "SpecialSystemDirectory.h"
#ifdef XP_WIN
# include "nsIObserver.h"
# include "nsIObserverService.h"
# include "mozilla/ResultExtensions.h"
# include "mozilla/Services.h"
# include "nsIUserIdleService.h"
# include "nsISimpleEnumerator.h"
# include "nsIFile.h"
# include "nsITimer.h"
# include "nsCRT.h"
using namespace mozilla;
// We store the temp files in the system temp dir.
// On Windows systems in particular we use a sub-directory of the temp
// directory, because:
// 1. DELETE_ON_CLOSE is unreliable on Windows, in particular if we power
// cycle (and perhaps if we crash) the files are not deleted. We store
// the temporary files in a known sub-dir so that we can find and delete
// them easily and quickly.
// 2. On Windows NT the system temp dir is in the user's $HomeDir/AppData,
// so we can be sure the user always has write privileges to that
// directory; if the sub-dir for our temp files was in some shared location
// and was created by a privileged user, it's possible that other users
// wouldn't have write access to that sub-dir. (Non-Windows systems
// don't store their temp files in a sub-dir, so this isn't an issue on
// those platforms).
// 3. Content processes can access the system temp dir
// (NS_GetSpecialDirectory fails on NS_APP_USER_PROFILE_LOCAL_50_DIR
// for content process for example, which is where we previously stored
// temp files on Windows). This argument applies to all platforms, not
// just Windows.
static nsresult GetTempDir(nsIFile** aTempDir) {
if (NS_WARN_IF(!aTempDir)) {
nsCOMPtr<nsIFile> tmpFile;
nsresult rv =
GetSpecialSystemDirectory(OS_TemporaryDirectory, getter_AddRefs(tmpFile));
if (NS_WARN_IF(NS_FAILED(rv))) {
return rv;
#ifdef XP_WIN
// On windows DELETE_ON_CLOSE is unreliable, so we store temporary files
// in a subdir of the temp dir and delete that in an idle service observer
// to ensure it's been cleared.
rv = tmpFile->AppendNative(nsDependentCString("mozilla-temp-files"));
if (NS_WARN_IF(NS_FAILED(rv))) {
return rv;
rv = tmpFile->Create(nsIFile::DIRECTORY_TYPE, 0700);
return rv;
return NS_OK;
nsresult NS_OpenAnonymousTemporaryNsIFile(nsIFile** aFile) {
if (NS_WARN_IF(!aFile)) {
nsresult rv;
nsCOMPtr<nsIFile> tmpFile;
rv = GetTempDir(getter_AddRefs(tmpFile));
if (NS_WARN_IF(NS_FAILED(rv))) {
return rv;
// Give the temp file a name with a random element. CreateUnique will also
// append a counter to the name if it encounters a name collision. Adding
// a random element to the name reduces the likelihood of a name collision,
// so that CreateUnique() doesn't end up trying a lot of name variants in
// its "try appending an incrementing counter" loop, as file IO can be
// expensive on some mobile flash drives.
nsAutoCString name("mozilla-temp-");
rv = tmpFile->AppendNative(name);
if (NS_WARN_IF(NS_FAILED(rv))) {
return rv;
rv = tmpFile->CreateUnique(nsIFile::NORMAL_FILE_TYPE, 0600);
if (NS_WARN_IF(NS_FAILED(rv))) {
return rv;
return NS_OK;
nsresult NS_OpenAnonymousTemporaryFile(PRFileDesc** aOutFileDesc) {
nsCOMPtr<nsIFile> tmpFile;
nsresult rv = NS_OpenAnonymousTemporaryNsIFile(getter_AddRefs(tmpFile));
if (NS_WARN_IF(NS_FAILED(rv))) {
return rv;
rv = tmpFile->OpenNSPRFileDesc(PR_RDWR | nsIFile::DELETE_ON_CLOSE, PR_IRWXU,
return rv;
#ifdef XP_WIN
// On Windows we have an idle service observer that runs some time after
// startup and deletes any stray anonymous temporary files...
// Duration of idle time before we'll get a callback whereupon we attempt to
// remove any stray and unused anonymous temp files.
// The nsAnonTempFileRemover is created in a timer, which sets an idle observer.
// This is expiration time (in ms) which initial timer is set for (3 minutes).
# define SCHEDULE_TIMEOUT_MS 3 * 60 * 1000
# define XPCOM_SHUTDOWN_TOPIC "xpcom-shutdown"
// This class adds itself as an idle observer. When the application has
// been idle for about 30 seconds we'll get a notification, whereupon we'll
// attempt to delete ${TempDir}/mozilla-temp-files/. This is to ensure all
// temp files that were supposed to be deleted on application exit were actually
// deleted, as they may not be if we previously crashed. See bugs 572579 and
// 785662. This is only needed on some versions of Windows,
// nsIFile::DELETE_ON_CLOSE works on other platforms.
// This class adds itself as a shutdown observer so that it can cancel the
// idle observer and its timer on shutdown. Note: the observer and idle
// services hold references to instances of this object, and those references
// are what keep this object alive.
class nsAnonTempFileRemover final : public nsIObserver {
nsAnonTempFileRemover() {}
nsresult Init() {
// We add the idle observer in a timer, so that the app has enough
// time to start up before we add the idle observer. If we register the
// idle observer too early, it will be registered before the fake idle
// service is installed when running in xpcshell, and this interferes with
// the fake idle service, causing xpcshell-test failures.
MOZ_TRY_VAR(mTimer, NS_NewTimerWithObserver(this, SCHEDULE_TIMEOUT_MS,
// Register shutdown observer so we can cancel the timer if we shutdown
// before the timer runs.
nsCOMPtr<nsIObserverService> obsSrv = services::GetObserverService();
if (NS_WARN_IF(!obsSrv)) {
return obsSrv->AddObserver(this, XPCOM_SHUTDOWN_TOPIC, false);
void Cleanup() {
// Cancel timer.
if (mTimer) {
mTimer = nullptr;
// Remove idle service observer.
nsCOMPtr<nsIUserIdleService> idleSvc =
if (idleSvc) {
idleSvc->RemoveIdleObserver(this, TEMP_FILE_IDLE_TIME_S);
// Remove shutdown observer.
nsCOMPtr<nsIObserverService> obsSrv = services::GetObserverService();
if (obsSrv) {
obsSrv->RemoveObserver(this, XPCOM_SHUTDOWN_TOPIC);
NS_IMETHODIMP Observe(nsISupports* aSubject, const char* aTopic,
const char16_t* aData) {
if (nsCRT::strcmp(aTopic, NS_TIMER_CALLBACK_TOPIC) == 0 &&
NS_FAILED(RegisterIdleObserver())) {
} else if (nsCRT::strcmp(aTopic, OBSERVER_TOPIC_IDLE) == 0) {
// The user has been idle for a while, clean up the temp files.
// The idle service will drop its reference to this object after
// we exit, destroying this object.
} else if (nsCRT::strcmp(aTopic, XPCOM_SHUTDOWN_TOPIC) == 0) {
return NS_OK;
nsresult RegisterIdleObserver() {
// Add this as an idle observer. When we've been idle for
// TEMP_FILE_IDLE_TIME_S seconds, we'll get a notification, and we'll then
// try to delete any stray temp files.
nsCOMPtr<nsIUserIdleService> idleSvc =
if (!idleSvc) {
return idleSvc->AddIdleObserver(this, TEMP_FILE_IDLE_TIME_S);
void RemoveAnonTempFileFiles() {
nsCOMPtr<nsIFile> tmpDir;
nsresult rv = GetTempDir(getter_AddRefs(tmpDir));
if (NS_WARN_IF(NS_FAILED(rv))) {
// Remove the directory recursively.
~nsAnonTempFileRemover() {}
nsCOMPtr<nsITimer> mTimer;
NS_IMPL_ISUPPORTS(nsAnonTempFileRemover, nsIObserver)
nsresult CreateAnonTempFileRemover() {
// Create a temp file remover. If Init() succeeds, the temp file remover is
// kept alive by a reference held by the observer service, since the temp file
// remover is a shutdown observer. We only create the temp file remover if
// we're running in the main process; there's no point in doing the temp file
// removal multiple times per startup.
if (!XRE_IsParentProcess()) {
return NS_OK;
RefPtr<nsAnonTempFileRemover> tempRemover = new nsAnonTempFileRemover();
return tempRemover->Init();