Only allow mappings for ICU initialization. (#8656)

If the mapping callback is not set or it the callback returns invalid data, ICU initialization will be embedder responsibility.

This affects all embedders and the following have been audited:
* Android: Via a symbol mapping.
* iOS: Via a file mapping.
* Embedder: Via a file mapping.
* Fuchsia: Via a VMO mapping
* Test shells and Flutter tester: Via file mapping with ICU data needing to be next to the executable.

Author: chinmaygarde

benchmarking/benchmarking.cc

@@ -10,7 +10,8 @@ namespace benchmarking {
 
 int Main(int argc, char** argv) {
   benchmark::Initialize(&argc, argv);
-  fml::icu::InitializeICU("icudtl.dat");
+  fml::icu::InitializeICU(fml::FileMapping::CreateReadOnly(
+      fml::OpenDirectoryOfExecutable(), "icudtl.dat"));
   ::benchmark::RunSpecifiedBenchmarks();
   return 0;
 }

common/settings.h

@@ -132,12 +132,6 @@ struct Settings {
   bool verbose_logging = false;
   std::string log_tag = "flutter";
 
-  // The icu_initialization_required setting does not have a corresponding
-  // switch because it is intended to be decided during build time, not runtime.
-  // Some companies apply source modification here because their build system
-  // brings its own ICU data files.
-  bool icu_initialization_required = true;
-  std::string icu_data_path;
   MappingCallback icu_mapper;
 
   // Assets settings

fml/file.cc

@@ -5,6 +5,7 @@
 #include "flutter/fml/file.h"
 
 #include "flutter/fml/logging.h"
+#include "flutter/fml/paths.h"
 
 namespace fml {
 
@@ -58,4 +59,14 @@ ScopedTemporaryDirectory::~ScopedTemporaryDirectory() {
   }
 }
 
+fml::UniqueFD OpenDirectoryOfExecutable() {
+  auto result = paths::GetExecutableDirectoryPath();
+
+  if (!result.first) {
+    return {};
+  }
+
+  return OpenFile(result.second.c_str(), false, FilePermission::kRead);
+}
+
 }  // namespace fml

fml/file.h

@@ -46,6 +46,8 @@ fml::UniqueFD OpenDirectory(const fml::UniqueFD& base_directory,
                             bool create_if_necessary,
                             FilePermission permission);
 
+fml::UniqueFD OpenDirectoryOfExecutable();
+
 fml::UniqueFD Duplicate(fml::UniqueFD::element_type descriptor);
 
 bool IsDirectory(const fml::UniqueFD& directory);

fml/icu_util.cc

@@ -4,115 +4,24 @@
 
 #include "flutter/fml/icu_util.h"
 
-#include <memory>
 #include <mutex>
 
-#include "flutter/fml/build_config.h"
 #include "flutter/fml/logging.h"
-#include "flutter/fml/mapping.h"
-#include "flutter/fml/native_library.h"
-#include "flutter/fml/paths.h"
 #include "third_party/icu/source/common/unicode/udata.h"
 
 namespace fml {
 namespace icu {
 
-class ICUContext {
- public:
-  ICUContext(const std::string& icu_data_path) : valid_(false) {
-    valid_ = SetupMapping(icu_data_path) && SetupICU();
+void InitializeICU(std::unique_ptr<const Mapping> mapping) {
+  if (mapping == nullptr || mapping->GetSize() == 0) {
+    return;
   }
-
-  ICUContext(std::unique_ptr<Mapping> mapping) : mapping_(std::move(mapping)) {
-    valid_ = SetupICU();
-  }
-
-  ~ICUContext() = default;
-
-  bool SetupMapping(const std::string& icu_data_path) {
-    // Check if the path exists and it readable directly.
-    auto fd =
-        fml::OpenFile(icu_data_path.c_str(), false, fml::FilePermission::kRead);
-
-    // Check the path relative to the current executable.
-    if (!fd.is_valid()) {
-      auto directory = fml::paths::GetExecutableDirectoryPath();
-
-      if (!directory.first) {
-        return false;
-      }
-
-      std::string path_relative_to_executable =
-          paths::JoinPaths({directory.second, icu_data_path});
-
-      fd = fml::OpenFile(path_relative_to_executable.c_str(), false,
-                         fml::FilePermission::kRead);
-    }
-
-    if (!fd.is_valid()) {
-      return false;
-    }
-
-    std::initializer_list<FileMapping::Protection> protection = {
-        fml::FileMapping::Protection::kRead};
-
-    auto file_mapping =
-        std::make_unique<FileMapping>(fd, std::move(protection));
-
-    if (file_mapping->GetSize() != 0) {
-      mapping_ = std::move(file_mapping);
-      return true;
-    }
-
-    return false;
-  }
-
-  bool SetupICU() {
-    if (GetSize() == 0) {
-      return false;
-    }
-
-    UErrorCode err_code = U_ZERO_ERROR;
-    udata_setCommonData(GetMapping(), &err_code);
-    return (err_code == U_ZERO_ERROR);
-  }
-
-  const uint8_t* GetMapping() const {
-    return mapping_ ? mapping_->GetMapping() : nullptr;
-  }
-
-  size_t GetSize() const { return mapping_ ? mapping_->GetSize() : 0; }
-
-  bool IsValid() const { return valid_; }
-
- private:
-  bool valid_;
-  std::unique_ptr<Mapping> mapping_;
-
-  FML_DISALLOW_COPY_AND_ASSIGN(ICUContext);
-};
-
-void InitializeICUOnce(const std::string& icu_data_path) {
-  static ICUContext* context = new ICUContext(icu_data_path);
-  FML_CHECK(context->IsValid())
-      << "Must be able to initialize the ICU context. Tried: " << icu_data_path;
-}
-
-std::once_flag g_icu_init_flag;
-void InitializeICU(const std::string& icu_data_path) {
-  std::call_once(g_icu_init_flag,
-                 [&icu_data_path]() { InitializeICUOnce(icu_data_path); });
-}
-
-void InitializeICUFromMappingOnce(std::unique_ptr<Mapping> mapping) {
-  static ICUContext* context = new ICUContext(std::move(mapping));
-  FML_CHECK(context->IsValid())
-      << "Unable to initialize the ICU context from a mapping.";
-}
-
-void InitializeICUFromMapping(std::unique_ptr<Mapping> mapping) {
+  static std::once_flag g_icu_init_flag;
   std::call_once(g_icu_init_flag, [mapping = std::move(mapping)]() mutable {
-    InitializeICUFromMappingOnce(std::move(mapping));
+    static auto icu_mapping = std::move(mapping);
+    UErrorCode err_code = U_ZERO_ERROR;
+    udata_setCommonData(icu_mapping->GetMapping(), &err_code);
+    FML_CHECK(err_code == U_ZERO_ERROR) << "Must be able to initialize ICU.";
   });
 }
 

fml/icu_util.h

@@ -13,9 +13,7 @@
 namespace fml {
 namespace icu {
 
-void InitializeICU(const std::string& icu_data_path = "");
-
-void InitializeICUFromMapping(std::unique_ptr<Mapping> mapping);
+void InitializeICU(std::unique_ptr<const Mapping> mapping);
 
 }  // namespace icu
 }  // namespace fml

shell/common/shell.cc

@@ -193,14 +193,8 @@ static void PerformInitializationTasks(const Settings& settings) {
       FML_DLOG(INFO) << "Skia deterministic rendering is enabled.";
     }
 
-    if (settings.icu_initialization_required) {
-      if (settings.icu_data_path.size() != 0) {
-        fml::icu::InitializeICU(settings.icu_data_path);
-      } else if (settings.icu_mapper) {
-        fml::icu::InitializeICUFromMapping(settings.icu_mapper());
-      } else {
-        FML_DLOG(WARNING) << "Skipping ICU initialization in the shell.";
-      }
+    if (settings.icu_mapper) {
+      fml::icu::InitializeICU(settings.icu_mapper());
     }
   });
 }

shell/common/switches.cc

@@ -242,9 +242,20 @@ Settings SettingsFromCommandLine(const fml::CommandLine& command_line) {
   command_line.GetOptionValue(FlagForSwitch(Switch::CacheDirPath),
                               &settings.temp_directory_path);
 
-  if (settings.icu_initialization_required) {
+  {
+    // ICU from a data file.
+    std::string icu_data_path;
     command_line.GetOptionValue(FlagForSwitch(Switch::ICUDataFilePath),
-                                &settings.icu_data_path);
+                                &icu_data_path);
+    if (icu_data_path.size() > 0) {
+      settings.icu_mapper = [icu_data_path]() {
+        return fml::FileMapping::CreateReadOnly(icu_data_path);
+      };
+    }
+  }
+
+  {
+    // ICU from a symbol in a dynamic library
     if (command_line.HasOption(FlagForSwitch(Switch::ICUSymbolPrefix))) {
       std::string icu_symbol_prefix, native_lib_path;
       command_line.GetOptionValue(FlagForSwitch(Switch::ICUSymbolPrefix),

shell/platform/darwin/ios/framework/Source/FlutterDartProject.mm

@@ -59,10 +59,13 @@
   // defaults.
 
   // Flutter ships the ICU data file in the the bundle of the engine. Look for it there.
-  if (settings.icu_data_path.size() == 0) {
+  if (!settings.icu_mapper) {
     NSString* icuDataPath = [engineBundle pathForResource:@"icudtl" ofType:@"dat"];
     if (icuDataPath.length > 0) {
-      settings.icu_data_path = icuDataPath.UTF8String;
+      auto icu_data_path = std::string{icuDataPath.UTF8String};
+      settings.icu_mapper = [icu_data_path]() {
+        return fml::FileMapping::CreateReadOnly(icu_data_path);
+      };
     }
   }
 

shell/platform/embedder/embedder.cc

@@ -370,7 +370,12 @@ FlutterEngineResult FlutterEngineRun(size_t version,
 
   PopulateSnapshotMappingCallbacks(args, settings);
 
-  settings.icu_data_path = icu_data_path;
+  if (!settings.icu_mapper) {
+    settings.icu_mapper = [icu_data_path]() {
+      return fml::FileMapping::CreateReadOnly(icu_data_path);
+    };
+  }
+
   settings.assets_path = args->assets_path;
 
   if (!flutter::DartVM::IsRunningPrecompiledCode()) {