ipc/ipc_message_attachment_set.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/ipc_message_attachment_set.h"
   6
   7 #include <algorithm>
   8 #include "base/logging.h"
   9 #include "base/posix/eintr_wrapper.h"
  10 #include "ipc/ipc_message_attachment.h"
  11
  12 #if defined(OS_POSIX)
  13 #include <sys/types.h>
  14 #include <sys/stat.h>
  15 #include <unistd.h>
  16 #include "ipc/ipc_platform_file_attachment_posix.h"
  17 #endif // OS_POSIX
  18
  19 namespace IPC {
  20
  21 MessageAttachmentSet::MessageAttachmentSet()
  22     : consumed_descriptor_highwater_(0) {
  23 }
  24
  25 MessageAttachmentSet::~MessageAttachmentSet() {
  26   if (consumed_descriptor_highwater_ == size())
  27     return;
  28
  29   // We close all the owning descriptors. If this message should have
  30   // been transmitted, then closing those with close flags set mirrors
  31   // the expected behaviour.
  32   //
  33   // If this message was received with more descriptors than expected
  34   // (which could a DOS against the browser by a rogue renderer) then all
  35   // the descriptors have their close flag set and we free all the extra
  36   // kernel resources.
  37   LOG(WARNING) << "MessageAttachmentSet destroyed with unconsumed descriptors: "
  38                << consumed_descriptor_highwater_ << "/" << size();
  39 }
  40
  41 unsigned MessageAttachmentSet::num_descriptors() const {
  42   return std::count_if(attachments_.begin(), attachments_.end(),
  43                        [](scoped_refptr<MessageAttachment> i) {
  44     return i->GetType() == MessageAttachment::TYPE_PLATFORM_FILE;
  45   });
  46 }
  47
  48 unsigned MessageAttachmentSet::size() const {
  49   return static_cast<unsigned>(attachments_.size());
  50 }
  51
  52 bool MessageAttachmentSet::AddAttachment(
  53     scoped_refptr<MessageAttachment> attachment) {
  54 #if defined(OS_POSIX)
  55   if (attachment->GetType() != MessageAttachment::TYPE_PLATFORM_FILE ||
  56       num_descriptors() == kMaxDescriptorsPerMessage) {
  57     DLOG(WARNING) << "Cannot add file descriptor. MessageAttachmentSet full.";
  58     return false;
  59   }
  60 #endif
  61
  62   attachments_.push_back(attachment);
  63   return true;
  64 }
  65
  66 scoped_refptr<MessageAttachment> MessageAttachmentSet::GetAttachmentAt(
  67     unsigned index) {
  68   if (index >= size()) {
  69     DLOG(WARNING) << "Accessing out of bound index:" << index << "/" << size();
  70     return scoped_refptr<MessageAttachment>();
  71   }
  72
  73   // We should always walk the descriptors in order, so it's reasonable to
  74   // enforce this. Consider the case where a compromised renderer sends us
  75   // the following message:
  76   //
  77   //   ExampleMsg:
  78   //     num_fds:2 msg:FD(index = 1) control:SCM_RIGHTS {n, m}
  79   //
  80   // Here the renderer sent us a message which should have a descriptor, but
  81   // actually sent two in an attempt to fill our fd table and kill us. By
  82   // setting the index of the descriptor in the message to 1 (it should be
  83   // 0), we would record a highwater of 1 and then consider all the
  84   // descriptors to have been used.
  85   //
  86   // So we can either track of the use of each descriptor in a bitset, or we
  87   // can enforce that we walk the indexes strictly in order.
  88   //
  89   // There's one more wrinkle: When logging messages, we may reparse them. So
  90   // we have an exception: When the consumed_descriptor_highwater_ is at the
  91   // end of the array and index 0 is requested, we reset the highwater value.
  92   // TODO(morrita): This is absurd. This "wringle" disallow to introduce clearer
  93   // ownership model. Only client is NaclIPCAdapter. See crbug.com/415294
  94   if (index == 0 && consumed_descriptor_highwater_ == size())
  95     consumed_descriptor_highwater_ = 0;
  96
  97   if (index != consumed_descriptor_highwater_)
  98     return scoped_refptr<MessageAttachment>();
  99
 100   consumed_descriptor_highwater_ = index + 1;
 101
 102   return attachments_[index];
 103 }
 104
 105 #if defined(OS_POSIX)
 106
 107 void MessageAttachmentSet::PeekDescriptors(base::PlatformFile* buffer) const {
 108   for (size_t i = 0; i != attachments_.size(); ++i)
 109     buffer[i] = internal::GetPlatformFile(attachments_[i]);
 110 }
 111
 112 bool MessageAttachmentSet::ContainsDirectoryDescriptor() const {
 113   struct stat st;
 114
 115   for (auto i = attachments_.begin(); i != attachments_.end(); ++i) {
 116     if (fstat(internal::GetPlatformFile(*i), &st) == 0 && S_ISDIR(st.st_mode))
 117       return true;
 118   }
 119
 120   return false;
 121 }
 122
 123 void MessageAttachmentSet::CommitAll() {
 124   attachments_.clear();
 125   consumed_descriptor_highwater_ = 0;
 126 }
 127
 128 void MessageAttachmentSet::ReleaseFDsToClose(
 129     std::vector<base::PlatformFile>* fds) {
 130   for (size_t i = 0; i < attachments_.size(); ++i) {
 131     internal::PlatformFileAttachment* file =
 132         static_cast<internal::PlatformFileAttachment*>(attachments_[i].get());
 133     if (file->Owns())
 134       fds->push_back(file->TakePlatformFile());
 135   }
 136
 137   CommitAll();
 138 }
 139
 140 void MessageAttachmentSet::AddDescriptorsToOwn(const base::PlatformFile* buffer,
 141                                                unsigned count) {
 142   DCHECK(count <= kMaxDescriptorsPerMessage);
 143   DCHECK_EQ(num_descriptors(), 0u);
 144   DCHECK_EQ(consumed_descriptor_highwater_, 0u);
 145
 146   attachments_.reserve(count);
 147   for (unsigned i = 0; i < count; ++i)
 148     AddAttachment(
 149         new internal::PlatformFileAttachment(base::ScopedFD(buffer[i])));
 150 }
 151
 152 #endif  // OS_POSIX
 153
 154 }  // namespace IPC
 155
 156