chrome/browser/download/download_target_determiner.cc

   1 // Copyright 2013 The Chromium Authors. All rights reserved.
   2 // Use of this source code is governed by a BSD-style license that can be
   3 // found in the LICENSE file.
   4
   5 #include "chrome/browser/download/download_target_determiner.h"
   6
   7 #include "base/prefs/pref_service.h"
   8 #include "base/rand_util.h"
   9 #include "base/strings/stringprintf.h"
  10 #include "base/time/time.h"
  11 #include "chrome/browser/download/chrome_download_manager_delegate.h"
  12 #include "chrome/browser/download/download_crx_util.h"
  13 #include "chrome/browser/download/download_extensions.h"
  14 #include "chrome/browser/download/download_prefs.h"
  15 #include "chrome/browser/extensions/webstore_installer.h"
  16 #include "chrome/browser/history/history_service.h"
  17 #include "chrome/browser/history/history_service_factory.h"
  18 #include "chrome/browser/profiles/profile.h"
  19 #include "chrome/common/pref_names.h"
  20 #include "content/public/browser/browser_context.h"
  21 #include "content/public/browser/browser_thread.h"
  22 #include "content/public/browser/download_interrupt_reasons.h"
  23 #include "extensions/common/constants.h"
  24 #include "extensions/common/feature_switch.h"
  25 #include "grit/generated_resources.h"
  26 #include "net/base/mime_util.h"
  27 #include "net/base/net_util.h"
  28 #include "ui/base/l10n/l10n_util.h"
  29
  30 #if defined(ENABLE_PLUGINS)
  31 #include "chrome/browser/plugins/plugin_prefs.h"
  32 #include "content/public/browser/plugin_service.h"
  33 #include "content/public/common/webplugininfo.h"
  34 #endif
  35
  36 using content::BrowserThread;
  37 using content::DownloadItem;
  38
  39 namespace {
  40
  41 const base::FilePath::CharType kCrdownloadSuffix[] =
  42     FILE_PATH_LITERAL(".crdownload");
  43
  44 // Condenses the results from HistoryService::GetVisibleVisitCountToHost() to a
  45 // single bool. A host is considered visited before if prior visible visits were
  46 // found in history and the first such visit was earlier than the most recent
  47 // midnight.
  48 void VisitCountsToVisitedBefore(
  49     const base::Callback<void(bool)>& callback,
  50     HistoryService::Handle unused_handle,
  51     bool found_visits,
  52     int count,
  53     base::Time first_visit) {
  54   callback.Run(
  55       found_visits && count > 0 &&
  56       (first_visit.LocalMidnight() < base::Time::Now().LocalMidnight()));
  57 }
  58
  59 } // namespace
  60
  61 DownloadTargetInfo::DownloadTargetInfo()
  62     : is_filetype_handled_safely(false) {}
  63
  64 DownloadTargetInfo::~DownloadTargetInfo() {}
  65
  66 DownloadTargetDeterminerDelegate::~DownloadTargetDeterminerDelegate() {
  67 }
  68
  69 DownloadTargetDeterminer::DownloadTargetDeterminer(
  70     DownloadItem* download,
  71     const base::FilePath& initial_virtual_path,
  72     DownloadPrefs* download_prefs,
  73     DownloadTargetDeterminerDelegate* delegate,
  74     const CompletionCallback& callback)
  75     : next_state_(STATE_GENERATE_TARGET_PATH),
  76       should_prompt_(false),
  77       should_notify_extensions_(false),
  78       create_target_directory_(false),
  79       conflict_action_(DownloadPathReservationTracker::OVERWRITE),
  80       danger_type_(download->GetDangerType()),
  81       virtual_path_(initial_virtual_path),
  82       is_filetype_handled_safely_(false),
  83       download_(download),
  84       is_resumption_(download_->GetLastReason() !=
  85                          content::DOWNLOAD_INTERRUPT_REASON_NONE &&
  86                      !initial_virtual_path.empty()),
  87       download_prefs_(download_prefs),
  88       delegate_(delegate),
  89       completion_callback_(callback),
  90       weak_ptr_factory_(this) {
  91   DCHECK(BrowserThread::CurrentlyOn(BrowserThread::UI));
  92   DCHECK(download_);
  93   DCHECK(delegate);
  94   download_->AddObserver(this);
  95
  96   DoLoop();
  97 }
  98
  99 DownloadTargetDeterminer::~DownloadTargetDeterminer() {
 100   DCHECK(BrowserThread::CurrentlyOn(BrowserThread::UI));
 101   DCHECK(download_);
 102   DCHECK(completion_callback_.is_null());
 103   download_->RemoveObserver(this);
 104 }
 105
 106 void DownloadTargetDeterminer::DoLoop() {
 107   Result result = CONTINUE;
 108   do {
 109     State current_state = next_state_;
 110     next_state_ = STATE_NONE;
 111
 112     switch (current_state) {
 113       case STATE_GENERATE_TARGET_PATH:
 114         result = DoGenerateTargetPath();
 115         break;
 116       case STATE_NOTIFY_EXTENSIONS:
 117         result = DoNotifyExtensions();
 118         break;
 119       case STATE_RESERVE_VIRTUAL_PATH:
 120         result = DoReserveVirtualPath();
 121         break;
 122       case STATE_PROMPT_USER_FOR_DOWNLOAD_PATH:
 123         result = DoPromptUserForDownloadPath();
 124         break;
 125       case STATE_DETERMINE_LOCAL_PATH:
 126         result = DoDetermineLocalPath();
 127         break;
 128       case STATE_DETERMINE_MIME_TYPE:
 129         result = DoDetermineMimeType();
 130         break;
 131       case STATE_DETERMINE_IF_HANDLED_SAFELY_BY_BROWSER:
 132         result = DoDetermineIfHandledSafely();
 133         break;
 134       case STATE_CHECK_DOWNLOAD_URL:
 135         result = DoCheckDownloadUrl();
 136         break;
 137       case STATE_DETERMINE_INTERMEDIATE_PATH:
 138         result = DoDetermineIntermediatePath();
 139         break;
 140       case STATE_CHECK_VISITED_REFERRER_BEFORE:
 141         result = DoCheckVisitedReferrerBefore();
 142         break;
 143       case STATE_NONE:
 144         NOTREACHED();
 145         return;
 146     }
 147   } while (result == CONTINUE);
 148   // Note that if a callback completes synchronously, the handler will still
 149   // return QUIT_DOLOOP. In this case, an inner DoLoop() may complete the target
 150   // determination and delete |this|.
 151
 152   if (result == COMPLETE)
 153     ScheduleCallbackAndDeleteSelf();
 154 }
 155
 156 DownloadTargetDeterminer::Result
 157     DownloadTargetDeterminer::DoGenerateTargetPath() {
 158   DCHECK(BrowserThread::CurrentlyOn(BrowserThread::UI));
 159   DCHECK(local_path_.empty());
 160   DCHECK(!should_prompt_);
 161   DCHECK(!should_notify_extensions_);
 162   DCHECK_EQ(DownloadPathReservationTracker::OVERWRITE, conflict_action_);
 163   bool is_forced_path = !download_->GetForcedFilePath().empty();
 164
 165   next_state_ = STATE_NOTIFY_EXTENSIONS;
 166
 167   if (!virtual_path_.empty() && HasPromptedForPath() && !is_forced_path) {
 168     // The download is being resumed and the user has already been prompted for
 169     // a path. Assume that it's okay to overwrite the file if there's a conflict
 170     // and reuse the selection.
 171     should_prompt_ = ShouldPromptForDownload(virtual_path_);
 172   } else if (!is_forced_path) {
 173     // If we don't have a forced path, we should construct a path for the
 174     // download. Forced paths are only specified for programmatic downloads
 175     // (WebStore, Drag&Drop). Treat the path as a virtual path. We will
 176     // eventually determine whether this is a local path and if not, figure out
 177     // a local path.
 178     std::string default_filename(
 179         l10n_util::GetStringUTF8(IDS_DEFAULT_DOWNLOAD_FILENAME));
 180     base::FilePath generated_filename = net::GenerateFileName(
 181         download_->GetURL(),
 182         download_->GetContentDisposition(),
 183         GetProfile()->GetPrefs()->GetString(prefs::kDefaultCharset),
 184         download_->GetSuggestedFilename(),
 185         download_->GetMimeType(),
 186         default_filename);
 187     should_prompt_ = ShouldPromptForDownload(generated_filename);
 188     base::FilePath target_directory;
 189     if (should_prompt_) {
 190       DCHECK(!download_prefs_->IsDownloadPathManaged());
 191       // If the user is going to be prompted and the user has been prompted
 192       // before, then always prefer the last directory that the user selected.
 193       target_directory = download_prefs_->SaveFilePath();
 194     } else {
 195       target_directory = download_prefs_->DownloadPath();
 196     }
 197     virtual_path_ = target_directory.Append(generated_filename);
 198     conflict_action_ = DownloadPathReservationTracker::UNIQUIFY;
 199     should_notify_extensions_ = true;
 200   } else {
 201     virtual_path_ = download_->GetForcedFilePath();
 202     // If this is a resumed download which was previously interrupted due to an
 203     // issue with the forced path, the user is still not prompted. If the path
 204     // supplied to a programmatic download is invalid, then the caller needs to
 205     // intervene.
 206   }
 207   DCHECK(virtual_path_.IsAbsolute());
 208   DVLOG(20) << "Generated virtual path: " << virtual_path_.AsUTF8Unsafe();
 209
 210   // If the download is DOA, don't bother going any further. This would be the
 211   // case for a download that failed to initialize (e.g. the initial temporary
 212   // file couldn't be created because both the downloads directory and the
 213   // temporary directory are unwriteable).
 214   //
 215   // A virtual path is determined for DOA downloads for display purposes. This
 216   // is why this check is performed here instead of at the start.
 217   if (download_->GetState() != DownloadItem::IN_PROGRESS)
 218     return COMPLETE;
 219   return CONTINUE;
 220 }
 221
 222 DownloadTargetDeterminer::Result
 223     DownloadTargetDeterminer::DoNotifyExtensions() {
 224   DCHECK(BrowserThread::CurrentlyOn(BrowserThread::UI));
 225   DCHECK(!virtual_path_.empty());
 226
 227   next_state_ = STATE_RESERVE_VIRTUAL_PATH;
 228
 229   if (!should_notify_extensions_)
 230     return CONTINUE;
 231
 232   delegate_->NotifyExtensions(download_, virtual_path_,
 233       base::Bind(&DownloadTargetDeterminer::NotifyExtensionsDone,
 234                  weak_ptr_factory_.GetWeakPtr()));
 235   return QUIT_DOLOOP;
 236 }
 237
 238 void DownloadTargetDeterminer::NotifyExtensionsDone(
 239     const base::FilePath& suggested_path,
 240     DownloadPathReservationTracker::FilenameConflictAction conflict_action) {
 241   DCHECK(BrowserThread::CurrentlyOn(BrowserThread::UI));
 242   DVLOG(20) << "Extension suggested path: " << suggested_path.AsUTF8Unsafe();
 243
 244   if (!suggested_path.empty()) {
 245     // If an extension overrides the filename, then the target directory will be
 246     // forced to download_prefs_->DownloadPath() since extensions cannot place
 247     // downloaded files anywhere except there. This prevents subdirectories from
 248     // accumulating: if an extension is allowed to say that a file should go in
 249     // last_download_path/music/foo.mp3, then last_download_path will accumulate
 250     // the subdirectory /music/ so that the next download may end up in
 251     // Downloads/music/music/music/bar.mp3.
 252     base::FilePath new_path(download_prefs_->DownloadPath().Append(
 253         suggested_path).NormalizePathSeparators());
 254     // Do not pass a mime type to GenerateSafeFileName so that it does not force
 255     // the filename to have an extension if the (Chrome) extension does not
 256     // suggest it.
 257     net::GenerateSafeFileName(std::string(), false, &new_path);
 258     virtual_path_ = new_path;
 259     create_target_directory_ = true;
 260     conflict_action_ = conflict_action;
 261   }
 262
 263   DoLoop();
 264 }
 265
 266 DownloadTargetDeterminer::Result
 267     DownloadTargetDeterminer::DoReserveVirtualPath() {
 268   DCHECK(BrowserThread::CurrentlyOn(BrowserThread::UI));
 269   DCHECK(!virtual_path_.empty());
 270
 271   next_state_ = STATE_PROMPT_USER_FOR_DOWNLOAD_PATH;
 272
 273   delegate_->ReserveVirtualPath(
 274       download_, virtual_path_, create_target_directory_, conflict_action_,
 275       base::Bind(&DownloadTargetDeterminer::ReserveVirtualPathDone,
 276                  weak_ptr_factory_.GetWeakPtr()));
 277   return QUIT_DOLOOP;
 278 }
 279
 280 void DownloadTargetDeterminer::ReserveVirtualPathDone(
 281     const base::FilePath& path, bool verified) {
 282   DCHECK(BrowserThread::CurrentlyOn(BrowserThread::UI));
 283   DVLOG(20) << "Reserved path: " << path.AsUTF8Unsafe()
 284             << " Verified:" << verified;
 285   should_prompt_ = (should_prompt_ || !verified);
 286   virtual_path_ = path;
 287   DoLoop();
 288 }
 289
 290 DownloadTargetDeterminer::Result
 291     DownloadTargetDeterminer::DoPromptUserForDownloadPath() {
 292   DCHECK(BrowserThread::CurrentlyOn(BrowserThread::UI));
 293   DCHECK(!virtual_path_.empty());
 294
 295   next_state_ = STATE_DETERMINE_LOCAL_PATH;
 296
 297   if (should_prompt_) {
 298     delegate_->PromptUserForDownloadPath(
 299         download_,
 300         virtual_path_,
 301         base::Bind(&DownloadTargetDeterminer::PromptUserForDownloadPathDone,
 302                    weak_ptr_factory_.GetWeakPtr()));
 303     return QUIT_DOLOOP;
 304   }
 305   return CONTINUE;
 306 }
 307
 308 void DownloadTargetDeterminer::PromptUserForDownloadPathDone(
 309     const base::FilePath& virtual_path) {
 310   DCHECK(BrowserThread::CurrentlyOn(BrowserThread::UI));
 311   DVLOG(20) << "User selected path:" << virtual_path.AsUTF8Unsafe();
 312   if (virtual_path.empty()) {
 313     CancelOnFailureAndDeleteSelf();
 314     return;
 315   }
 316   virtual_path_ = virtual_path;
 317   download_prefs_->SetSaveFilePath(virtual_path_.DirName());
 318   DoLoop();
 319 }
 320
 321 DownloadTargetDeterminer::Result
 322     DownloadTargetDeterminer::DoDetermineLocalPath() {
 323   DCHECK(BrowserThread::CurrentlyOn(BrowserThread::UI));
 324   DCHECK(!virtual_path_.empty());
 325   DCHECK(local_path_.empty());
 326
 327   next_state_ = STATE_DETERMINE_MIME_TYPE;
 328
 329   delegate_->DetermineLocalPath(
 330       download_,
 331       virtual_path_,
 332       base::Bind(&DownloadTargetDeterminer::DetermineLocalPathDone,
 333                  weak_ptr_factory_.GetWeakPtr()));
 334   return QUIT_DOLOOP;
 335 }
 336
 337 void DownloadTargetDeterminer::DetermineLocalPathDone(
 338     const base::FilePath& local_path) {
 339   DCHECK(BrowserThread::CurrentlyOn(BrowserThread::UI));
 340   DVLOG(20) << "Local path: " << local_path.AsUTF8Unsafe();
 341   if (local_path.empty()) {
 342     // Path subsitution failed.
 343     CancelOnFailureAndDeleteSelf();
 344     return;
 345   }
 346   local_path_ = local_path;
 347   DoLoop();
 348 }
 349
 350 DownloadTargetDeterminer::Result
 351     DownloadTargetDeterminer::DoDetermineMimeType() {
 352   DCHECK(BrowserThread::CurrentlyOn(BrowserThread::UI));
 353   DCHECK(!virtual_path_.empty());
 354   DCHECK(!local_path_.empty());
 355   DCHECK(mime_type_.empty());
 356
 357   next_state_ = STATE_DETERMINE_IF_HANDLED_SAFELY_BY_BROWSER;
 358
 359   if (virtual_path_ == local_path_) {
 360     delegate_->GetFileMimeType(
 361         local_path_,
 362         base::Bind(&DownloadTargetDeterminer::DetermineMimeTypeDone,
 363                    weak_ptr_factory_.GetWeakPtr()));
 364     return QUIT_DOLOOP;
 365   }
 366   return CONTINUE;
 367 }
 368
 369 void DownloadTargetDeterminer::DetermineMimeTypeDone(
 370     const std::string& mime_type) {
 371   DCHECK(BrowserThread::CurrentlyOn(BrowserThread::UI));
 372   DVLOG(20) << "MIME type: " << mime_type;
 373   mime_type_ = mime_type;
 374   DoLoop();
 375 }
 376
 377 #if defined(ENABLE_PLUGINS)
 378 // The code below is used by DoDetermineIfHandledSafely to determine if the
 379 // file type is handled by a sandboxed plugin.
 380 namespace {
 381
 382 void InvokeClosureAfterGetPluginCallback(
 383     const base::Closure& closure,
 384     const std::vector<content::WebPluginInfo>& unused) {
 385   closure.Run();
 386 }
 387
 388 enum ActionOnStalePluginList {
 389   RETRY_IF_STALE_PLUGIN_LIST,
 390   IGNORE_IF_STALE_PLUGIN_LIST
 391 };
 392
 393 void IsHandledBySafePlugin(content::ResourceContext* resource_context,
 394                            const GURL& url,
 395                            const std::string& mime_type,
 396                            ActionOnStalePluginList stale_plugin_action,
 397                            const base::Callback<void(bool)>& callback) {
 398   DCHECK(BrowserThread::CurrentlyOn(BrowserThread::IO));
 399   DCHECK(!mime_type.empty());
 400   using content::WebPluginInfo;
 401
 402   std::string actual_mime_type;
 403   bool is_stale = false;
 404   WebPluginInfo plugin_info;
 405
 406   content::PluginService* plugin_service =
 407       content::PluginService::GetInstance();
 408   bool plugin_found = plugin_service->GetPluginInfo(-1, -1, resource_context,
 409                                                     url, GURL(), mime_type,
 410                                                     false, &is_stale,
 411                                                     &plugin_info,
 412                                                     &actual_mime_type);
 413   if (is_stale && stale_plugin_action == RETRY_IF_STALE_PLUGIN_LIST) {
 414     // The GetPlugins call causes the plugin list to be refreshed. Once that's
 415     // done we can retry the GetPluginInfo call. We break out of this cycle
 416     // after a single retry in order to avoid retrying indefinitely.
 417     plugin_service->GetPlugins(
 418         base::Bind(&InvokeClosureAfterGetPluginCallback,
 419                    base::Bind(&IsHandledBySafePlugin,
 420                               resource_context,
 421                               url,
 422                               mime_type,
 423                               IGNORE_IF_STALE_PLUGIN_LIST,
 424                               callback)));
 425     return;
 426   }
 427   // In practice, we assume that retrying once is enough.
 428   DCHECK(!is_stale);
 429   bool is_handled_safely =
 430       plugin_found &&
 431       (plugin_info.type == WebPluginInfo::PLUGIN_TYPE_PEPPER_IN_PROCESS ||
 432        plugin_info.type == WebPluginInfo::PLUGIN_TYPE_PEPPER_OUT_OF_PROCESS);
 433   BrowserThread::PostTask(
 434       BrowserThread::UI, FROM_HERE, base::Bind(callback, is_handled_safely));
 435 }
 436
 437 } // namespace
 438 #endif  // ENABLE_PLUGINS
 439
 440 DownloadTargetDeterminer::Result
 441     DownloadTargetDeterminer::DoDetermineIfHandledSafely() {
 442   DCHECK(BrowserThread::CurrentlyOn(BrowserThread::UI));
 443   DCHECK(!virtual_path_.empty());
 444   DCHECK(!local_path_.empty());
 445   DCHECK(!is_filetype_handled_safely_);
 446
 447   next_state_ = STATE_CHECK_DOWNLOAD_URL;
 448
 449   if (mime_type_.empty())
 450     return CONTINUE;
 451
 452   if (net::IsSupportedMimeType(mime_type_)) {
 453     is_filetype_handled_safely_ = true;
 454     return CONTINUE;
 455   }
 456
 457 #if defined(ENABLE_PLUGINS)
 458   BrowserThread::PostTask(
 459       BrowserThread::IO,
 460       FROM_HERE,
 461       base::Bind(
 462           &IsHandledBySafePlugin,
 463           GetProfile()->GetResourceContext(),
 464           net::FilePathToFileURL(local_path_),
 465           mime_type_,
 466           RETRY_IF_STALE_PLUGIN_LIST,
 467           base::Bind(&DownloadTargetDeterminer::DetermineIfHandledSafelyDone,
 468                      weak_ptr_factory_.GetWeakPtr())));
 469   return QUIT_DOLOOP;
 470 #else
 471   return CONTINUE;
 472 #endif
 473 }
 474
 475 void DownloadTargetDeterminer::DetermineIfHandledSafelyDone(
 476     bool is_handled_safely) {
 477   DCHECK(BrowserThread::CurrentlyOn(BrowserThread::UI));
 478   is_filetype_handled_safely_ = is_handled_safely;
 479   DVLOG(20) << "Is file type handled safely: " << is_filetype_handled_safely_;
 480   DoLoop();
 481 }
 482
 483 DownloadTargetDeterminer::Result
 484     DownloadTargetDeterminer::DoCheckDownloadUrl() {
 485   DCHECK(BrowserThread::CurrentlyOn(BrowserThread::UI));
 486   DCHECK(!virtual_path_.empty());
 487   next_state_ = STATE_CHECK_VISITED_REFERRER_BEFORE;
 488   delegate_->CheckDownloadUrl(
 489       download_,
 490       virtual_path_,
 491       base::Bind(&DownloadTargetDeterminer::CheckDownloadUrlDone,
 492                  weak_ptr_factory_.GetWeakPtr()));
 493   return QUIT_DOLOOP;
 494 }
 495
 496 void DownloadTargetDeterminer::CheckDownloadUrlDone(
 497     content::DownloadDangerType danger_type) {
 498   DCHECK(BrowserThread::CurrentlyOn(BrowserThread::UI));
 499   DVLOG(20) << "URL Check Result:" << danger_type;
 500   danger_type_ = danger_type;
 501   DoLoop();
 502 }
 503
 504 DownloadTargetDeterminer::Result
 505     DownloadTargetDeterminer::DoCheckVisitedReferrerBefore() {
 506   DCHECK(BrowserThread::CurrentlyOn(BrowserThread::UI));
 507
 508   next_state_ = STATE_DETERMINE_INTERMEDIATE_PATH;
 509
 510   // Checking if there are prior visits to the referrer is only necessary if the
 511   // danger level of the download depends on the file type. This excludes cases
 512   // where the download has already been deemed dangerous, or where the user is
 513   // going to be prompted or where this is a programmatic download.
 514   if (danger_type_ != content::DOWNLOAD_DANGER_TYPE_NOT_DANGEROUS)
 515     return CONTINUE;
 516
 517   // Assume that:
 518   // IsDangerousFile(VISITED_REFERRER) => IsDangerousFile(NO_VISITS_...)
 519   // I.e. having visited a referrer only lowers a file's danger level.
 520   if (IsDangerousFile(NO_VISITS_TO_REFERRER)) {
 521     // Only need to ping the history DB if the download would be considered safe
 522     // if there are prior visits and is considered dangerous otherwise.
 523     if (!IsDangerousFile(VISITED_REFERRER)) {
 524       // HistoryServiceFactory redirects incognito profiles to on-record
 525       // profiles.  There's no history for on-record profiles in unit_tests.
 526       HistoryService* history_service = HistoryServiceFactory::GetForProfile(
 527           GetProfile(), Profile::EXPLICIT_ACCESS);
 528
 529       if (history_service && download_->GetReferrerUrl().is_valid()) {
 530         history_service->GetVisibleVisitCountToHost(
 531             download_->GetReferrerUrl(), &history_consumer_,
 532             base::Bind(&VisitCountsToVisitedBefore, base::Bind(
 533                 &DownloadTargetDeterminer::CheckVisitedReferrerBeforeDone,
 534                 weak_ptr_factory_.GetWeakPtr())));
 535         return QUIT_DOLOOP;
 536       }
 537     }
 538
 539     // If the danger level doesn't depend on having visited the refererrer URL
 540     // or if original profile doesn't have a HistoryService or the referrer url
 541     // is invalid, then assume the referrer has not been visited before.
 542     danger_type_ = content::DOWNLOAD_DANGER_TYPE_DANGEROUS_FILE;
 543   }
 544   return CONTINUE;
 545 }
 546
 547 void DownloadTargetDeterminer::CheckVisitedReferrerBeforeDone(
 548     bool visited_referrer_before) {
 549   DCHECK(BrowserThread::CurrentlyOn(BrowserThread::UI));
 550   if (IsDangerousFile(
 551           visited_referrer_before ? VISITED_REFERRER : NO_VISITS_TO_REFERRER))
 552     danger_type_ = content::DOWNLOAD_DANGER_TYPE_DANGEROUS_FILE;
 553   DoLoop();
 554 }
 555
 556 DownloadTargetDeterminer::Result
 557     DownloadTargetDeterminer::DoDetermineIntermediatePath() {
 558   DCHECK(BrowserThread::CurrentlyOn(BrowserThread::UI));
 559   DCHECK(!virtual_path_.empty());
 560   DCHECK(!local_path_.empty());
 561   DCHECK(intermediate_path_.empty());
 562   DCHECK(!virtual_path_.MatchesExtension(kCrdownloadSuffix));
 563   DCHECK(!local_path_.MatchesExtension(kCrdownloadSuffix));
 564
 565   next_state_ = STATE_NONE;
 566
 567   // Note that the intermediate filename is always uniquified (i.e. if a file by
 568   // the same name exists, it is never overwritten). Therefore the code below
 569   // does not attempt to find a name that doesn't conflict with an existing
 570   // file.
 571
 572   // If the actual target of the download is a virtual path, then the local path
 573   // is considered to point to a temporary path. A separate intermediate path is
 574   // unnecessary since the local path already serves that purpose.
 575   if (virtual_path_.BaseName() != local_path_.BaseName()) {
 576     intermediate_path_ = local_path_;
 577     return COMPLETE;
 578   }
 579
 580   // If the download has a forced path and is safe, then just use the
 581   // target path. In practice the temporary download file that was created prior
 582   // to download filename determination is already named
 583   // download_->GetForcedFilePath().
 584   if (danger_type_ == content::DOWNLOAD_DANGER_TYPE_NOT_DANGEROUS &&
 585       !download_->GetForcedFilePath().empty()) {
 586     DCHECK_EQ(download_->GetForcedFilePath().value(), local_path_.value());
 587     intermediate_path_ = local_path_;
 588     return COMPLETE;
 589   }
 590
 591   // Other safe downloads get a .crdownload suffix for their intermediate name.
 592   if (danger_type_ == content::DOWNLOAD_DANGER_TYPE_NOT_DANGEROUS) {
 593     intermediate_path_ = GetCrDownloadPath(local_path_);
 594     return COMPLETE;
 595   }
 596
 597   // If this is a resumed download, then re-use the existing intermediate path
 598   // if one is available. A resumed download shouldn't cause a non-dangerous
 599   // download to be considered dangerous upon resumption. Therefore the
 600   // intermediate file should already be in the correct form.
 601   if (is_resumption_ && !download_->GetFullPath().empty() &&
 602       local_path_.DirName() == download_->GetFullPath().DirName()) {
 603     DCHECK_NE(content::DOWNLOAD_DANGER_TYPE_NOT_DANGEROUS,
 604               download_->GetDangerType());
 605     DCHECK_EQ(kCrdownloadSuffix, download_->GetFullPath().Extension());
 606     intermediate_path_ = download_->GetFullPath();
 607     return COMPLETE;
 608   }
 609
 610   // Dangerous downloads receive a random intermediate name that looks like:
 611   // 'Unconfirmed <random>.crdownload'.
 612   const base::FilePath::CharType kUnconfirmedFormatSuffix[] =
 613       FILE_PATH_LITERAL(" %d.crdownload");
 614   // Range of the <random> uniquifier.
 615   const int kUnconfirmedUniquifierRange = 1000000;
 616 #if defined(OS_WIN)
 617   base::string16 unconfirmed_format =
 618       l10n_util::GetStringUTF16(IDS_DOWNLOAD_UNCONFIRMED_PREFIX);
 619 #else
 620   std::string unconfirmed_format =
 621       l10n_util::GetStringUTF8(IDS_DOWNLOAD_UNCONFIRMED_PREFIX);
 622 #endif
 623   unconfirmed_format.append(kUnconfirmedFormatSuffix);
 624
 625   base::FilePath::StringType file_name = base::StringPrintf(
 626       unconfirmed_format.c_str(),
 627       base::RandInt(0, kUnconfirmedUniquifierRange));
 628   intermediate_path_ = local_path_.DirName().Append(file_name);
 629   return COMPLETE;
 630 }
 631
 632 void DownloadTargetDeterminer::ScheduleCallbackAndDeleteSelf() {
 633   DCHECK(download_);
 634   DVLOG(20) << "Scheduling callback. Virtual:" << virtual_path_.AsUTF8Unsafe()
 635             << " Local:" << local_path_.AsUTF8Unsafe()
 636             << " Intermediate:" << intermediate_path_.AsUTF8Unsafe()
 637             << " Should prompt:" << should_prompt_
 638             << " Danger type:" << danger_type_;
 639   scoped_ptr<DownloadTargetInfo> target_info(new DownloadTargetInfo);
 640
 641   target_info->target_path = local_path_;
 642   target_info->target_disposition =
 643       (HasPromptedForPath() || should_prompt_
 644            ? DownloadItem::TARGET_DISPOSITION_PROMPT
 645            : DownloadItem::TARGET_DISPOSITION_OVERWRITE);
 646   target_info->danger_type = danger_type_;
 647   target_info->intermediate_path = intermediate_path_;
 648   target_info->mime_type = mime_type_;
 649   target_info->is_filetype_handled_safely = is_filetype_handled_safely_;
 650
 651   base::MessageLoop::current()->PostTask(
 652       FROM_HERE, base::Bind(completion_callback_, base::Passed(&target_info)));
 653   completion_callback_.Reset();
 654   delete this;
 655 }
 656
 657 void DownloadTargetDeterminer::CancelOnFailureAndDeleteSelf() {
 658   // Path substitution failed.
 659   virtual_path_.clear();
 660   local_path_.clear();
 661   intermediate_path_.clear();
 662   ScheduleCallbackAndDeleteSelf();
 663 }
 664
 665 Profile* DownloadTargetDeterminer::GetProfile() {
 666   DCHECK(download_->GetBrowserContext());
 667   return Profile::FromBrowserContext(download_->GetBrowserContext());
 668 }
 669
 670 bool DownloadTargetDeterminer::ShouldPromptForDownload(
 671     const base::FilePath& filename) const {
 672   if (is_resumption_) {
 673     // For resumed downloads, if the target disposition or prefs require
 674     // prompting, the user has already been prompted. Try to respect the user's
 675     // selection, unless we've discovered that the target path cannot be used
 676     // for some reason.
 677     content::DownloadInterruptReason reason = download_->GetLastReason();
 678     return (reason == content::DOWNLOAD_INTERRUPT_REASON_FILE_ACCESS_DENIED ||
 679             reason == content::DOWNLOAD_INTERRUPT_REASON_FILE_NO_SPACE ||
 680             reason == content::DOWNLOAD_INTERRUPT_REASON_FILE_TOO_LARGE);
 681   }
 682
 683   // If the download path is forced, don't prompt.
 684   if (!download_->GetForcedFilePath().empty()) {
 685     // 'Save As' downloads shouldn't have a forced path.
 686     DCHECK(DownloadItem::TARGET_DISPOSITION_PROMPT !=
 687            download_->GetTargetDisposition());
 688     return false;
 689   }
 690
 691   // Don't ask where to save if the download path is managed. Even if the user
 692   // wanted to be prompted for "all" downloads, or if this was a 'Save As'
 693   // download.
 694   if (download_prefs_->IsDownloadPathManaged())
 695     return false;
 696
 697   // Prompt if this is a 'Save As' download.
 698   if (download_->GetTargetDisposition() ==
 699       DownloadItem::TARGET_DISPOSITION_PROMPT)
 700     return true;
 701
 702   // Check if the user has the "Always prompt for download location" preference
 703   // set. If so we prompt for most downloads except for the following scenarios:
 704   // 1) Extension installation. Note that we only care here about the case where
 705   //    an extension is installed, not when one is downloaded with "save as...".
 706   // 2) Filetypes marked "always open." If the user just wants this file opened,
 707   //    don't bother asking where to keep it.
 708   if (download_prefs_->PromptForDownload() &&
 709       !download_crx_util::IsExtensionDownload(*download_) &&
 710       !filename.MatchesExtension(extensions::kExtensionFileExtension) &&
 711       !download_prefs_->IsAutoOpenEnabledBasedOnExtension(filename))
 712     return true;
 713
 714   // Otherwise, don't prompt. Note that the user might still be prompted if
 715   // there are unresolved conflicts during path reservation (e.g. due to the
 716   // target path being unwriteable or because there are too many conflicting
 717   // files), or if an extension signals that the user be prompted on a filename
 718   // conflict.
 719   return false;
 720 }
 721
 722 bool DownloadTargetDeterminer::HasPromptedForPath() const {
 723   return (is_resumption_ && download_->GetTargetDisposition() ==
 724                                 DownloadItem::TARGET_DISPOSITION_PROMPT);
 725 }
 726
 727 bool DownloadTargetDeterminer::IsDangerousFile(PriorVisitsToReferrer visits) {
 728   DCHECK(BrowserThread::CurrentlyOn(BrowserThread::UI));
 729
 730   // If the user has has been prompted or will be, assume that the user has
 731   // approved the download. A programmatic download is considered safe unless it
 732   // contains malware.
 733   if (HasPromptedForPath() || should_prompt_ ||
 734       !download_->GetForcedFilePath().empty())
 735     return false;
 736
 737   const bool is_extension_download =
 738       download_crx_util::IsExtensionDownload(*download_);
 739
 740   // User-initiated extension downloads from pref-whitelisted sources are not
 741   // considered dangerous.
 742   if (download_->HasUserGesture() &&
 743       is_extension_download &&
 744       download_crx_util::OffStoreInstallAllowedByPrefs(
 745           GetProfile(), *download_)) {
 746     return false;
 747   }
 748
 749   // Extensions that are not from the gallery are considered dangerous.
 750   // When off-store install is disabled we skip this, since in this case, we
 751   // will not offer to install the extension.
 752   if (extensions::FeatureSwitch::easy_off_store_install()->IsEnabled() &&
 753       is_extension_download &&
 754       !extensions::WebstoreInstaller::GetAssociatedApproval(*download_)) {
 755     return true;
 756   }
 757
 758   // Anything the user has marked auto-open is OK if it's user-initiated.
 759   if (download_prefs_->IsAutoOpenEnabledBasedOnExtension(virtual_path_) &&
 760       download_->HasUserGesture())
 761     return false;
 762
 763   switch (download_util::GetFileDangerLevel(virtual_path_.BaseName())) {
 764     case download_util::NOT_DANGEROUS:
 765       return false;
 766
 767     case download_util::ALLOW_ON_USER_GESTURE:
 768       // "Allow on user gesture" is OK when we have a user gesture and the
 769       // hosting page has been visited before today.
 770       if (download_->GetTransitionType() &
 771           content::PAGE_TRANSITION_FROM_ADDRESS_BAR) {
 772         return false;
 773       }
 774       return !download_->HasUserGesture() || visits == NO_VISITS_TO_REFERRER;
 775
 776     case download_util::DANGEROUS:
 777       return true;
 778   }
 779   NOTREACHED();
 780   return false;
 781 }
 782
 783 void DownloadTargetDeterminer::OnDownloadDestroyed(
 784     DownloadItem* download) {
 785   DCHECK(BrowserThread::CurrentlyOn(BrowserThread::UI));
 786   DCHECK_EQ(download_, download);
 787   CancelOnFailureAndDeleteSelf();
 788 }
 789
 790 // static
 791 void DownloadTargetDeterminer::Start(content::DownloadItem* download,
 792                                      const base::FilePath& initial_virtual_path,
 793                                      DownloadPrefs* download_prefs,
 794                                      DownloadTargetDeterminerDelegate* delegate,
 795                                      const CompletionCallback& callback) {
 796   // DownloadTargetDeterminer owns itself and will self destruct when the job is
 797   // complete or the download item is destroyed. The callback is always invoked
 798   // asynchronously.
 799   new DownloadTargetDeterminer(download, initial_virtual_path, download_prefs,
 800                                delegate, callback);
 801 }
 802
 803 // static
 804 base::FilePath DownloadTargetDeterminer::GetCrDownloadPath(
 805     const base::FilePath& suggested_path) {
 806   return base::FilePath(suggested_path.value() + kCrdownloadSuffix);
 807 }