ipc/file_descriptor_set_posix.cc

   1 // Copyright (c) 2011 The Chromium Authors. All rights reserved.
   2 // Use of this source code is governed by a BSD-style license that can be
   3 // found in the LICENSE file.
   4
   5 #include "ipc/file_descriptor_set_posix.h"
   6
   7 #include <sys/types.h>
   8 #include <sys/stat.h>
   9 #include <unistd.h>
  10
  11 #include "base/logging.h"
  12 #include "base/posix/eintr_wrapper.h"
  13
  14 FileDescriptorSet::FileDescriptorSet()
  15     : consumed_descriptor_highwater_(0) {
  16 }
  17
  18 FileDescriptorSet::~FileDescriptorSet() {
  19   if (consumed_descriptor_highwater_ == descriptors_.size())
  20     return;
  21
  22   LOG(WARNING) << "FileDescriptorSet destroyed with unconsumed descriptors";
  23   // We close all the descriptors where the close flag is set. If this
  24   // message should have been transmitted, then closing those with close
  25   // flags set mirrors the expected behaviour.
  26   //
  27   // If this message was received with more descriptors than expected
  28   // (which could a DOS against the browser by a rogue renderer) then all
  29   // the descriptors have their close flag set and we free all the extra
  30   // kernel resources.
  31   for (unsigned i = consumed_descriptor_highwater_;
  32        i < descriptors_.size(); ++i) {
  33     if (descriptors_[i].auto_close)
  34       if (HANDLE_EINTR(close(descriptors_[i].fd)) < 0)
  35         PLOG(ERROR) << "close";
  36   }
  37 }
  38
  39 bool FileDescriptorSet::Add(int fd) {
  40   if (descriptors_.size() == kMaxDescriptorsPerMessage)
  41     return false;
  42
  43   struct base::FileDescriptor sd;
  44   sd.fd = fd;
  45   sd.auto_close = false;
  46   descriptors_.push_back(sd);
  47   return true;
  48 }
  49
  50 bool FileDescriptorSet::AddAndAutoClose(int fd) {
  51   if (descriptors_.size() == kMaxDescriptorsPerMessage)
  52     return false;
  53
  54   struct base::FileDescriptor sd;
  55   sd.fd = fd;
  56   sd.auto_close = true;
  57   descriptors_.push_back(sd);
  58   DCHECK(descriptors_.size() <= kMaxDescriptorsPerMessage);
  59   return true;
  60 }
  61
  62 int FileDescriptorSet::GetDescriptorAt(unsigned index) const {
  63   if (index >= descriptors_.size())
  64     return -1;
  65
  66   // We should always walk the descriptors in order, so it's reasonable to
  67   // enforce this. Consider the case where a compromised renderer sends us
  68   // the following message:
  69   //
  70   //   ExampleMsg:
  71   //     num_fds:2 msg:FD(index = 1) control:SCM_RIGHTS {n, m}
  72   //
  73   // Here the renderer sent us a message which should have a descriptor, but
  74   // actually sent two in an attempt to fill our fd table and kill us. By
  75   // setting the index of the descriptor in the message to 1 (it should be
  76   // 0), we would record a highwater of 1 and then consider all the
  77   // descriptors to have been used.
  78   //
  79   // So we can either track of the use of each descriptor in a bitset, or we
  80   // can enforce that we walk the indexes strictly in order.
  81   //
  82   // There's one more wrinkle: When logging messages, we may reparse them. So
  83   // we have an exception: When the consumed_descriptor_highwater_ is at the
  84   // end of the array and index 0 is requested, we reset the highwater value.
  85   if (index == 0 && consumed_descriptor_highwater_ == descriptors_.size())
  86     consumed_descriptor_highwater_ = 0;
  87
  88   if (index != consumed_descriptor_highwater_)
  89     return -1;
  90
  91   consumed_descriptor_highwater_ = index + 1;
  92   return descriptors_[index].fd;
  93 }
  94
  95 void FileDescriptorSet::GetDescriptors(int* buffer) const {
  96   for (std::vector<base::FileDescriptor>::const_iterator
  97        i = descriptors_.begin(); i != descriptors_.end(); ++i) {
  98     *(buffer++) = i->fd;
  99   }
 100 }
 101
 102 bool FileDescriptorSet::ContainsDirectoryDescriptor() const {
 103   struct stat st;
 104
 105   for (std::vector<base::FileDescriptor>::const_iterator
 106        i = descriptors_.begin(); i != descriptors_.end(); ++i) {
 107     if (fstat(i->fd, &st) == 0 && S_ISDIR(st.st_mode))
 108       return true;
 109   }
 110
 111   return false;
 112 }
 113
 114 void FileDescriptorSet::CommitAll() {
 115   for (std::vector<base::FileDescriptor>::iterator
 116        i = descriptors_.begin(); i != descriptors_.end(); ++i) {
 117     if (i->auto_close)
 118       if (HANDLE_EINTR(close(i->fd)) < 0)
 119         PLOG(ERROR) << "close";
 120   }
 121   descriptors_.clear();
 122   consumed_descriptor_highwater_ = 0;
 123 }
 124
 125 void FileDescriptorSet::SetDescriptors(const int* buffer, unsigned count) {
 126   DCHECK(count <= kMaxDescriptorsPerMessage);
 127   DCHECK_EQ(descriptors_.size(), 0u);
 128   DCHECK_EQ(consumed_descriptor_highwater_, 0u);
 129
 130   descriptors_.reserve(count);
 131   for (unsigned i = 0; i < count; ++i) {
 132     struct base::FileDescriptor sd;
 133     sd.fd = buffer[i];
 134     sd.auto_close = true;
 135     descriptors_.push_back(sd);
 136   }
 137 }