Separates ipc code from common (http://crbug.com/16829)

ipc/file_descriptor_set_posix.cc

+// Copyright (c) 2006-2008 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 "ipc/file_descriptor_set_posix.h"
+
+#include "base/eintr_wrapper.h"
+#include "base/logging.h"
+
+FileDescriptorSet::FileDescriptorSet()
+    : consumed_descriptor_highwater_(0) {
+}
+
+FileDescriptorSet::~FileDescriptorSet() {
+  if (consumed_descriptor_highwater_ == descriptors_.size())
+    return;
+
+  LOG(WARNING) << "FileDescriptorSet destroyed with unconsumed descriptors";
+  // We close all the descriptors where the close flag is set. If this
+  // message should have been transmitted, then closing those with close
+  // flags set mirrors the expected behaviour.
+  //
+  // If this message was received with more descriptors than expected
+  // (which could a DOS against the browser by a rogue renderer) then all
+  // the descriptors have their close flag set and we free all the extra
+  // kernel resources.
+  for (unsigned i = consumed_descriptor_highwater_;
+       i < descriptors_.size(); ++i) {
+    if (descriptors_[i].auto_close)
+      HANDLE_EINTR(close(descriptors_[i].fd));
+  }
+}
+
+bool FileDescriptorSet::Add(int fd) {
+  if (descriptors_.size() == MAX_DESCRIPTORS_PER_MESSAGE)
+    return false;
+
+  struct base::FileDescriptor sd;
+  sd.fd = fd;
+  sd.auto_close = false;
+  descriptors_.push_back(sd);
+  return true;
+}
+
+bool FileDescriptorSet::AddAndAutoClose(int fd) {
+  if (descriptors_.size() == MAX_DESCRIPTORS_PER_MESSAGE)
+    return false;
+
+  struct base::FileDescriptor sd;
+  sd.fd = fd;
+  sd.auto_close = true;
+  descriptors_.push_back(sd);
+  DCHECK(descriptors_.size() <= MAX_DESCRIPTORS_PER_MESSAGE);
+  return true;
+}
+
+int FileDescriptorSet::GetDescriptorAt(unsigned index) const {
+  if (index >= descriptors_.size())
+    return -1;
+
+  // We should always walk the descriptors in order, so it's reasonable to
+  // enforce this. Consider the case where a compromised renderer sends us
+  // the following message:
+  //
+  //   ExampleMsg:
+  //     num_fds:2 msg:FD(index = 1) control:SCM_RIGHTS {n, m}
+  //
+  // Here the renderer sent us a message which should have a descriptor, but
+  // actually sent two in an attempt to fill our fd table and kill us. By
+  // setting the index of the descriptor in the message to 1 (it should be
+  // 0), we would record a highwater of 1 and then consider all the
+  // descriptors to have been used.
+  //
+  // So we can either track of the use of each descriptor in a bitset, or we
+  // can enforce that we walk the indexes strictly in order.
+  //
+  // There's one more wrinkle: When logging messages, we may reparse them. So
+  // we have an exception: When the consumed_descriptor_highwater_ is at the
+  // end of the array and index 0 is requested, we reset the highwater value.
+  if (index == 0 && consumed_descriptor_highwater_ == descriptors_.size())
+    consumed_descriptor_highwater_ = 0;
+
+  if (index != consumed_descriptor_highwater_)
+    return -1;
+
+  consumed_descriptor_highwater_ = index + 1;
+  return descriptors_[index].fd;
+}
+
+void FileDescriptorSet::GetDescriptors(int* buffer) const {
+  for (std::vector<base::FileDescriptor>::const_iterator
+       i = descriptors_.begin(); i != descriptors_.end(); ++i) {
+    *(buffer++) = i->fd;
+  }
+}
+
+void FileDescriptorSet::CommitAll() {
+  for (std::vector<base::FileDescriptor>::iterator
+       i = descriptors_.begin(); i != descriptors_.end(); ++i) {
+    if (i->auto_close)
+      HANDLE_EINTR(close(i->fd));
+  }
+  descriptors_.clear();
+  consumed_descriptor_highwater_ = 0;
+}
+
+void FileDescriptorSet::SetDescriptors(const int* buffer, unsigned count) {
+  DCHECK_LE(count, MAX_DESCRIPTORS_PER_MESSAGE);
+  DCHECK_EQ(descriptors_.size(), 0u);
+  DCHECK_EQ(consumed_descriptor_highwater_, 0u);
+
+  descriptors_.reserve(count);
+  for (unsigned i = 0; i < count; ++i) {
+    struct base::FileDescriptor sd;
+    sd.fd = buffer[i];
+    sd.auto_close = true;
+    descriptors_.push_back(sd);
+  }
+}