dbus: revamp fd passing for i/o restrictions

dbus/message.cc

 // Copyright (c) 2012 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "dbus/message.h"
 
 #include <string>
 
 #include "base/basictypes.h"
 #include "base/format_macros.h"
 #include "base/logging.h"
-#include "base/platform_file.h"
 #include "base/stringprintf.h"
 #include "dbus/object_path.h"
 #include "third_party/protobuf/src/google/protobuf/message_lite.h"
 
 namespace {
 
 // Appends the header name and the value to |output|, if the value is
 // not empty.
 static void AppendStringHeader(const std::string& header_name,
                                const std::string& header_value,
@@ skipping 661 matching lines @@
   const std::string signature = base::StringPrintf("%c", dbus_type);
   MessageWriter variant_writer(message_);
   OpenVariant(signature, &variant_writer);
   variant_writer.AppendBasic(dbus_type, value);
   CloseContainer(&variant_writer);
 }
 
 void MessageWriter::AppendFileDescriptor(const FileDescriptor& value) {
   CHECK(kDBusTypeUnixFdIsSupported);
 
-  base::PlatformFileInfo info;
-  int fd = value.value();
-  bool ok = base::GetPlatformFileInfo(fd, &info);
-  if (!ok || info.is_directory) {
+  if (!value.is_valid()) {
     // NB: sending a directory potentially enables sandbox escape
     LOG(FATAL) << "Attempt to pass invalid file descriptor";
   }
+  int fd = value.value();
   AppendBasic(DBUS_TYPE_UNIX_FD, &fd);
 }
 
 //
 // MessageReader implementation.
 //
 
 MessageReader::MessageReader(Message* message)
     : message_(message) {
   memset(&raw_message_iter_, 0, sizeof(raw_message_iter_));
@@ skipping 250 matching lines @@
 }
 
 bool MessageReader::PopFileDescriptor(FileDescriptor* value) {
   CHECK(kDBusTypeUnixFdIsSupported);
 
   int fd = -1;
   const bool success = PopBasic(DBUS_TYPE_UNIX_FD, &fd);
   if (!success)
     return false;
 
-  base::PlatformFileInfo info;
-  bool ok = base::GetPlatformFileInfo(fd, &info);
-  if (!ok || info.is_directory) {
-    base::ClosePlatformFile(fd);
-    // NB: receiving a directory potentially enables sandbox escape
-    LOG(FATAL) << "Attempt to receive invalid file descriptor";
-    return false;  // NB: not reached
-  }
   value->PutValue(fd);
+  // NB: the caller must check validity before using the value
   return true;
 }
 
 }  // namespace dbus