refactor: mmap asar files

lib/common/asar.js

@@ -520,17 +520,12 @@
         return fs.readFile(realPath, options, callback);
       }
 
-      const buffer = Buffer.alloc(info.size);
-      const fd = archive.getFd();
-      if (!(fd >= 0)) {
-        const error = createError(AsarError.NOT_FOUND, { asarPath, filePath });
-        nextTick(callback, [error]);
-        return;
-      }
-
       logASARAccess(asarPath, filePath, info.offset);
-      fs.read(fd, buffer, 0, info.size, info.offset, error => {
-        callback(error, encoding ? buffer.toString(encoding) : buffer);
+      archive.read(info.offset, info.size).then((buf) => {
+        const buffer = Buffer.from(buf);
+        callback(null, encoding ? buffer.toString(encoding) : buffer);
+      }, (err) => {
+        callback(err);
       });
     };
 
@@ -562,13 +557,10 @@
       }
 
       const { encoding } = options;
-      const buffer = Buffer.alloc(info.size);
-      const fd = archive.getFd();
-      if (!(fd >= 0)) throw createError(AsarError.NOT_FOUND, { asarPath, filePath });
 
       logASARAccess(asarPath, filePath, info.offset);
-      fs.readSync(fd, buffer, 0, info.size, info.offset);
-      return (encoding) ? buffer.toString(encoding) : buffer;
+      const buffer = Buffer.from(archive.readSync(info.offset, info.size));
+      return encoding ? buffer.toString(encoding) : buffer;
     };
 
     const { readdir } = fs;
@@ -664,12 +656,8 @@
         return fs.readFileSync(realPath, { encoding: 'utf8' });
       }
 
-      const buffer = Buffer.alloc(info.size);
-      const fd = archive.getFd();
-      if (!(fd >= 0)) return;
-
       logASARAccess(asarPath, filePath, info.offset);
-      fs.readSync(fd, buffer, 0, info.size, info.offset);
+      const buffer = Buffer.from(archive.readSync(info.offset, info.size));
       return buffer.toString('utf8');
     };
 

shell/common/api/electron_api_asar.cc

@@ -6,15 +6,18 @@
 
 #include <vector>
 
+#include "base/numerics/safe_math.h"
 #include "shell/common/asar/archive.h"
 #include "shell/common/asar/asar_util.h"
 #include "shell/common/gin_converters/callback_converter.h"
 #include "shell/common/gin_converters/file_path_converter.h"
 #include "shell/common/gin_helper/dictionary.h"
 #include "shell/common/gin_helper/object_template_builder.h"
+#include "shell/common/gin_helper/promise.h"
 #include "shell/common/gin_helper/wrappable.h"
 #include "shell/common/node_includes.h"
 #include "shell/common/node_util.h"
+
 namespace {
 
 class Archive : public gin_helper::Wrappable<Archive> {
@@ -37,7 +40,8 @@ class Archive : public gin_helper::Wrappable<Archive> {
         .SetMethod("readdir", &Archive::Readdir)
         .SetMethod("realpath", &Archive::Realpath)
         .SetMethod("copyFileOut", &Archive::CopyFileOut)
-        .SetMethod("getFd", &Archive::GetFD);
+        .SetMethod("read", &Archive::Read)
+        .SetMethod("readSync", &Archive::ReadSync);
   }
 
  protected:
@@ -103,15 +107,67 @@ class Archive : public gin_helper::Wrappable<Archive> {
     return gin::ConvertToV8(isolate, new_path);
   }
 
-  // Return the file descriptor.
-  int GetFD() const {
-    if (!archive_)
-      return -1;
-    return archive_->GetFD();
+  v8::Local<v8::ArrayBuffer> ReadSync(gin_helper::ErrorThrower thrower,
+                                      uint64_t offset,
+                                      uint64_t length) {
+    base::CheckedNumeric<uint64_t> safe_offset(offset);
+    base::CheckedNumeric<uint64_t> safe_end = safe_offset + length;
+    if (!safe_end.IsValid() ||
+        safe_end.ValueOrDie() > archive_->file()->length()) {
+      thrower.ThrowError("Out of bounds read requested in ASAR");
+      return v8::Local<v8::ArrayBuffer>();
+    }
+    auto array_buffer = v8::ArrayBuffer::New(thrower.isolate(), length);
+    auto backing_store = array_buffer->GetBackingStore();
+    memcpy(backing_store->Data(), archive_->file()->data() + offset, length);
+    return array_buffer;
+  }
+
+  v8::Local<v8::Promise> Read(gin_helper::ErrorThrower thrower,
+                              uint64_t offset,
+                              uint64_t length) {
+    gin_helper::Promise<v8::Local<v8::ArrayBuffer>> promise(thrower.isolate());
+    v8::Local<v8::Promise> handle = promise.GetHandle();
+
+    base::CheckedNumeric<uint64_t> safe_offset(offset);
+    base::CheckedNumeric<uint64_t> safe_end = safe_offset + length;
+    if (!safe_end.IsValid() ||
+        safe_end.ValueOrDie() > archive_->file()->length()) {
+      thrower.ThrowError("Out of bounds read requested in ASAR");
+      return v8::Local<v8::Promise>();
+    }
+
+    base::ThreadPool::PostTaskAndReplyWithResult(
+        FROM_HERE, {base::MayBlock(), base::TaskPriority::USER_VISIBLE},
+        base::BindOnce(&Archive::ReadOnIO, thrower.isolate(), archive_, offset,
+                       length),
+        base::BindOnce(&Archive::ResolveReadOnUI, std::move(promise)));
+
+    return handle;
   }
 
  private:
-  std::unique_ptr<asar::Archive> archive_;
+  static std::unique_ptr<v8::BackingStore> ReadOnIO(
+      v8::Isolate* isolate,
+      std::shared_ptr<asar::Archive> archive,
+      uint64_t offset,
+      uint64_t length) {
+    auto backing_store = v8::ArrayBuffer::NewBackingStore(isolate, length);
+    memcpy(backing_store->Data(), archive->file()->data() + offset, length);
+    return backing_store;
+  }
+
+  static void ResolveReadOnUI(
+      gin_helper::Promise<v8::Local<v8::ArrayBuffer>> promise,
+      std::unique_ptr<v8::BackingStore> backing_store) {
+    v8::HandleScope scope(promise.isolate());
+    v8::Context::Scope context_scope(promise.GetContext());
+    auto array_buffer =
+        v8::ArrayBuffer::New(promise.isolate(), std::move(backing_store));
+    promise.Resolve(array_buffer);
+  }
+
+  std::shared_ptr<asar::Archive> archive_;
 
   DISALLOW_COPY_AND_ASSIGN(Archive);
 };

shell/common/asar/archive.cc

@@ -117,78 +117,51 @@ bool FillFileInfoWithNode(Archive::FileInfo* info,
 
 }  // namespace
 
-Archive::Archive(const base::FilePath& path)
-    : path_(path), file_(base::File::FILE_OK) {
+Archive::Archive(const base::FilePath& path) : path_(path) {
   base::ThreadRestrictions::ScopedAllowIO allow_io;
-  file_.Initialize(path_, base::File::FLAG_OPEN | base::File::FLAG_READ);
-#if defined(OS_WIN)
-  fd_ = _open_osfhandle(reinterpret_cast<intptr_t>(file_.GetPlatformFile()), 0);
-#elif defined(OS_POSIX)
-  fd_ = file_.GetPlatformFile();
-#endif
-}
-
-Archive::~Archive() {
-#if defined(OS_WIN)
-  if (fd_ != -1) {
-    _close(fd_);
-    // Don't close the handle since we already closed the fd.
-    file_.TakePlatformFile();
+  if (!file_.Initialize(path_)) {
+    LOG(ERROR) << "Failed to open ASAR archive at '" << path_.value() << "'";
   }
-#endif
-  base::ThreadRestrictions::ScopedAllowIO allow_io;
-  file_.Close();
 }
 
+Archive::~Archive() {}
+
 bool Archive::Init() {
   if (!file_.IsValid()) {
-    if (file_.error_details() != base::File::FILE_ERROR_NOT_FOUND) {
-      LOG(WARNING) << "Opening " << path_.value() << ": "
-                   << base::File::ErrorToString(file_.error_details());
-    }
     return false;
   }
 
-  std::vector<char> buf;
-  int len;
-
-  buf.resize(8);
-  {
-    base::ThreadRestrictions::ScopedAllowIO allow_io;
-    len = file_.ReadAtCurrentPos(buf.data(), buf.size());
-  }
-  if (len != static_cast<int>(buf.size())) {
-    PLOG(ERROR) << "Failed to read header size from " << path_.value();
+  if (file_.length() < 8) {
+    LOG(ERROR) << "Malformed ASAR file at '" << path_.value()
+               << "' (too short)";
     return false;
   }
 
   uint32_t size;
-  if (!base::PickleIterator(base::Pickle(buf.data(), buf.size()))
-           .ReadUInt32(&size)) {
-    LOG(ERROR) << "Failed to parse header size from " << path_.value();
+  base::PickleIterator size_pickle(
+      base::Pickle(reinterpret_cast<const char*>(file_.data()), 8));
+  if (!size_pickle.ReadUInt32(&size)) {
+    LOG(ERROR) << "Failed to read header size at '" << path_.value() << "'";
     return false;
   }
 
-  buf.resize(size);
-  {
-    base::ThreadRestrictions::ScopedAllowIO allow_io;
-    len = file_.ReadAtCurrentPos(buf.data(), buf.size());
-  }
-  if (len != static_cast<int>(buf.size())) {
-    PLOG(ERROR) << "Failed to read header from " << path_.value();
+  if (file_.length() - 8 < size) {
+    LOG(ERROR) << "Malformed ASAR file at '" << path_.value()
+               << "' (incorrect header)";
     return false;
   }
 
+  base::PickleIterator header_pickle(
+      base::Pickle(reinterpret_cast<const char*>(file_.data() + 8), size));
   std::string header;
-  if (!base::PickleIterator(base::Pickle(buf.data(), buf.size()))
-           .ReadString(&header)) {
-    LOG(ERROR) << "Failed to parse header from " << path_.value();
+  if (!header_pickle.ReadString(&header)) {
+    LOG(ERROR) << "Failed to read header string at '" << path_.value() << "'";
     return false;
   }
 
   base::Optional<base::Value> value = base::JSONReader::Read(header);
   if (!value || !value->is_dict()) {
-    LOG(ERROR) << "Failed to parse header";
+    LOG(ERROR) << "Header was not valid JSON at '" << path_.value() << "'";
     return false;
   }
 
@@ -291,11 +264,24 @@ bool Archive::CopyFileOut(const base::FilePath& path, base::FilePath* out) {
     return true;
   }
 
+  base::CheckedNumeric<uint64_t> safe_offset(info.offset);
+  auto safe_end = safe_offset + info.size;
+  if (!safe_end.IsValid() || safe_end.ValueOrDie() > file_.length())
+    return false;
+
   auto temp_file = std::make_unique<ScopedTemporaryFile>();
   base::FilePath::StringType ext = path.Extension();
-  if (!temp_file->InitFromFile(&file_, ext, info.offset, info.size))
+  if (!temp_file->Init(ext))
     return false;
 
+  base::File dest(temp_file->path(),
+                  base::File::FLAG_OPEN | base::File::FLAG_WRITE);
+  if (!dest.IsValid())
+    return false;
+
+  dest.WriteAtCurrentPos(
+      reinterpret_cast<const char*>(file_.data() + info.offset), info.size);
+
 #if defined(OS_POSIX)
   if (info.executable) {
     // chmod a+x temp_file;
@@ -308,8 +294,4 @@ bool Archive::CopyFileOut(const base::FilePath& path, base::FilePath* out) {
   return true;
 }
 
-int Archive::GetFD() const {
-  return fd_;
-}
-
 }  // namespace asar

shell/common/asar/archive.h

@@ -11,6 +11,7 @@
 
 #include "base/files/file.h"
 #include "base/files/file_path.h"
+#include "base/files/memory_mapped_file.h"
 
 namespace base {
 class DictionaryValue;
@@ -61,16 +62,13 @@ class Archive {
   // For unpacked file, this method will return its real path.
   bool CopyFileOut(const base::FilePath& path, base::FilePath* out);
 
-  // Returns the file's fd.
-  int GetFD() const;
-
+  base::MemoryMappedFile* file() { return &file_; }
   base::FilePath path() const { return path_; }
   base::DictionaryValue* header() const { return header_.get(); }
 
  private:
   base::FilePath path_;
-  base::File file_;
-  int fd_ = -1;
+  base::MemoryMappedFile file_;
   uint32_t header_size_ = 0;
   std::unique_ptr<base::DictionaryValue> header_;
 

shell/common/asar/scoped_temporary_file.cc

@@ -48,27 +48,4 @@ bool ScopedTemporaryFile::Init(const base::FilePath::StringType& ext) {
   return true;
 }
 
-bool ScopedTemporaryFile::InitFromFile(base::File* src,
-                                       const base::FilePath::StringType& ext,
-                                       uint64_t offset,
-                                       uint64_t size) {
-  if (!src->IsValid())
-    return false;
-
-  if (!Init(ext))
-    return false;
-
-  std::vector<char> buf(size);
-  int len = src->Read(offset, buf.data(), buf.size());
-  if (len != static_cast<int>(size))
-    return false;
-
-  base::File dest(path_, base::File::FLAG_OPEN | base::File::FLAG_WRITE);
-  if (!dest.IsValid())
-    return false;
-
-  return dest.WriteAtCurrentPos(buf.data(), buf.size()) ==
-         static_cast<int>(size);
-}
-
 }  // namespace asar

shell/common/asar/scoped_temporary_file.h

@@ -25,12 +25,6 @@ class ScopedTemporaryFile {
   // Init an empty temporary file with a certain extension.
   bool Init(const base::FilePath::StringType& ext);
 
-  // Init an temporary file and fill it with content of |path|.
-  bool InitFromFile(base::File* src,
-                    const base::FilePath::StringType& ext,
-                    uint64_t offset,
-                    uint64_t size);
-
   base::FilePath path() const { return path_; }
 
  private: