Add --file-url-path-alias.

--file-url-path-alias=/alias=/replacements will result in  all file://
URLs with root paths beginning with /alias to be replaced with
/replacement.

For IPC fuzzer builds, this is automatically populated with
/gen=BUILD_DIR/gen.

Bug: 839228
Change-Id: I935278d8b11369efc9b98281a5a8056cee8e579d
Reviewed-on: https://chromium-review.googlesource.com/1119727
Commit-Queue: Oliver Chang <ochang@chromium.org>
Reviewed-by: Alex Moshchuk <alexmos@chromium.org>
Reviewed-by: Ken Rockot <rockot@chromium.org>
Cr-Commit-Position: refs/heads/master@{#572434}

content/browser/browser_main_loop.cc

@@ -27,6 +27,7 @@
 #include "base/metrics/field_trial.h"
 #include "base/metrics/histogram_macros.h"
 #include "base/metrics/user_metrics.h"
+#include "base/path_service.h"
 #include "base/pending_task.h"
 #include "base/power_monitor/power_monitor.h"
 #include "base/power_monitor/power_monitor_device_source.h"
@@ -233,6 +234,10 @@
 #include "crypto/nss_util.h"
 #endif
 
+#if defined(ENABLE_IPC_FUZZER) && defined(OS_MACOSX)
+#include "base/mac/foundation_util.h"
+#endif
+
 // One of the linux specific headers defines this as a macro.
 #ifdef DestroyAll
 #undef DestroyAll
@@ -397,6 +402,40 @@ void InitDefaultJob() {
 }
 #endif  // defined(OS_FUCHSIA)
 
+#if defined(ENABLE_IPC_FUZZER)
+bool GetBuildDirectory(base::FilePath* result) {
+  if (!base::PathService::Get(base::DIR_EXE, result))
+    return false;
+
+#if defined(OS_MACOSX)
+  if (base::mac::AmIBundled()) {
+    // The bundled app executables (Chromium, TestShell, etc) live three
+    // levels down from the build directory, eg:
+    // Chromium.app/Contents/MacOS/Chromium
+    *result = result->DirName().DirName().DirName();
+  }
+#endif
+  return true;
+}
+
+void SetFileUrlPathAliasForIpcFuzzer() {
+  if (base::CommandLine::ForCurrentProcess()->HasSwitch(
+          switches::kFileUrlPathAlias))
+    return;
+
+  base::FilePath build_directory;
+  if (!GetBuildDirectory(&build_directory)) {
+    LOG(ERROR) << "Failed to get build directory for /gen path alias.";
+    return;
+  }
+
+  const base::CommandLine::StringType alias_switch =
+      FILE_PATH_LITERAL("/gen=") + build_directory.AppendASCII("gen").value();
+  base::CommandLine::ForCurrentProcess()->AppendSwitchNative(
+      switches::kFileUrlPathAlias, alias_switch);
+}
+#endif
+
 }  // namespace
 
 #if defined(USE_X11)
@@ -1422,6 +1461,9 @@ int BrowserMainLoop::BrowserThreadsStarted() {
   media::SetMediaDrmBridgeClient(GetContentClient()->GetMediaDrmBridgeClient());
 #endif
 
+#if defined(ENABLE_IPC_FUZZER)
+  SetFileUrlPathAliasForIpcFuzzer();
+#endif
   return result_code_;
 }
 

content/browser/renderer_host/render_process_host_impl.cc

@@ -2781,6 +2781,7 @@ void RenderProcessHostImpl::PropagateBrowserCommandLineToRenderer(
     switches::kEnableWebGLImageChromium,
     switches::kEnableWebVR,
     switches::kExplicitlyAllowedPorts,
+    switches::kFileUrlPathAlias,
     switches::kFMPNetworkQuietTimeout,
     switches::kForceColorProfile,
     switches::kForceDeviceScaleFactor,

content/public/common/content_switches.cc

@@ -476,6 +476,11 @@ const char kExplicitlyAllowedPorts[]        = "explicitly-allowed-ports";
 // shared memory segment as a string.
 const char kFieldTrialHandle[] = "field-trial-handle";
 
+// Define an alias root directory which is replaced with the replacement string
+// in file URLs. The format is "/alias=/replacement", which would turn
+// file:///alias/some/path.html into file:///replacement/some/path.html.
+const char kFileUrlPathAlias[] = "file-url-path-alias";
+
 // Always use the Skia GPU backend for drawing layer tiles. Only valid with GPU
 // accelerated compositing + impl-side painting. Overrides the
 // kEnableGpuRasterization flag.

content/public/common/content_switches.h

@@ -148,6 +148,7 @@ CONTENT_EXPORT extern const char kEnableWebVR[];
 CONTENT_EXPORT extern const char kEnableZeroCopy[];
 CONTENT_EXPORT extern const char kExplicitlyAllowedPorts[];
 CONTENT_EXPORT extern const char kFieldTrialHandle[];
+CONTENT_EXPORT extern const char kFileUrlPathAlias[];
 CONTENT_EXPORT extern const char kForceDisplayList2dCanvas[];
 CONTENT_EXPORT extern const char kForceGpuRasterization[];
 CONTENT_EXPORT extern const char kDisableOopRasterization[];

content/renderer/render_frame_impl.cc

@@ -35,6 +35,8 @@
 #include "base/stl_util.h"
 #include "base/strings/string16.h"
 #include "base/strings/string_piece.h"
+#include "base/strings/string_split.h"
+#include "base/strings/string_util.h"
 #include "base/strings/utf_string_conversions.h"
 #include "base/task_runner_util.h"
 #include "base/task_scheduler/post_task.h"
@@ -872,6 +874,41 @@ std::unique_ptr<DocumentState> BuildDocumentStateFromPending(
   return document_state;
 }
 
+void ApplyFilePathAlias(blink::WebURLRequest* request) {
+  const base::CommandLine::StringType file_url_path_alias =
+      base::CommandLine::ForCurrentProcess()->GetSwitchValueNative(
+          switches::kFileUrlPathAlias);
+  if (file_url_path_alias.empty())
+    return;
+
+  const auto alias_mapping =
+      base::SplitString(file_url_path_alias, FILE_PATH_LITERAL("="),
+                        base::TRIM_WHITESPACE, base::SPLIT_WANT_NONEMPTY);
+  if (alias_mapping.size() != 2) {
+    LOG(ERROR) << "Invalid file path alias format.";
+    return;
+  }
+
+#if defined(OS_WIN)
+  base::string16 path = request->Url().GetString().Utf16();
+  const base::string16 file_prefix =
+      base::ASCIIToUTF16(url::kFileScheme) +
+      base::ASCIIToUTF16(url::kStandardSchemeSeparator);
+#else
+  std::string path = request->Url().GetString().Utf8();
+  const std::string file_prefix =
+      std::string(url::kFileScheme) + url::kStandardSchemeSeparator;
+#endif
+  if (!base::StartsWith(path, file_prefix + alias_mapping[0],
+                        base::CompareCase::SENSITIVE)) {
+    return;
+  }
+
+  base::ReplaceFirstSubstringAfterOffset(&path, 0, alias_mapping[0],
+                                         alias_mapping[1]);
+  request->SetURL(blink::WebURL(GURL(path)));
+}
+
 }  // namespace
 
 class RenderFrameImpl::FrameURLLoaderFactory
@@ -4727,6 +4764,7 @@ void RenderFrameImpl::WillSendRequest(blink::WebURLRequest& request) {
         transition_type | ui::PAGE_TRANSITION_CLIENT_REDIRECT);
   }
 
+  ApplyFilePathAlias(&request);
   GURL new_url;
   bool attach_same_site_cookies = false;
   base::Optional<url::Origin> initiator_origin =

content/renderer/render_frame_impl_browsertest.cc

@@ -19,6 +19,7 @@
 #include "content/common/frame_owner_properties.h"
 #include "content/common/renderer.mojom.h"
 #include "content/common/view_messages.h"
+#include "content/public/common/content_switches.h"
 #include "content/public/common/previews_state.h"
 #include "content/public/renderer/content_renderer_client.h"
 #include "content/public/renderer/document_state.h"
@@ -621,6 +622,29 @@ TEST_F(RenderFrameImplTest, AutoplayFlags_WrongOrigin) {
             AutoplayFlagsForFrame(GetMainRenderFrame()));
 }
 
+TEST_F(RenderFrameImplTest, FileUrlPathAlias) {
+  const struct {
+    const char* original;
+    const char* transformed;
+  } kTestCases[] = {
+      {"file:///alias", "file:///replacement"},
+      {"file:///alias/path/to/file", "file:///replacement/path/to/file"},
+      {"file://alias/path/to/file", "file://alias/path/to/file"},
+      {"file:///notalias/path/to/file", "file:///notalias/path/to/file"},
+      {"file:///root/alias/path/to/file", "file:///root/alias/path/to/file"},
+      {"file:///", "file:///"},
+  };
+  base::CommandLine::ForCurrentProcess()->AppendSwitchASCII(
+      switches::kFileUrlPathAlias, "/alias=/replacement");
+
+  for (const auto& test_case : kTestCases) {
+    WebURLRequest request;
+    request.SetURL(GURL(test_case.original));
+    GetMainRenderFrame()->WillSendRequest(request);
+    EXPECT_EQ(test_case.transformed, request.Url().GetString().Utf8());
+  }
+}
+
 // RenderFrameRemoteInterfacesTest ------------------------------------
 
 namespace {