Allow MessageFilters to restrict listening to specific message classes

ipc/ipc_channel_proxy.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 "base/bind.h"
 #include "base/compiler_specific.h"
 #include "base/debug/trace_event.h"
 #include "base/location.h"
 #include "base/memory/ref_counted.h"
 #include "base/memory/scoped_ptr.h"
 #include "base/single_thread_task_runner.h"
 #include "base/thread_task_runner_handle.h"
 #include "ipc/ipc_channel_proxy.h"
 #include "ipc/ipc_listener.h"
 #include "ipc/ipc_logging.h"
 #include "ipc/ipc_message_macros.h"
 #include "ipc/ipc_message_utils.h"
 
 namespace IPC {
+namespace {
+bool EraseFilter(const ChannelProxy::MessageFilter* filter,
+                 std::vector<ChannelProxy::MessageFilter*>& filters) {
+  std::vector<ChannelProxy::MessageFilter*>::iterator it =
+      std::find(filters.begin(), filters.end(), filter);
+  if (it == filters.end())
+    return false;
+
+  filters.erase(it);
+  return true;
+}
+
+bool ApplyFilters(std::vector<ChannelProxy::MessageFilter*>& filters,
+                  const IPC::Message& message,
+                  const std::string& channel_id) {
+#ifdef IPC_MESSAGE_LOG_ENABLED
+  Logging* logger = Logging::GetInstance();
+#endif
+
+  for (size_t i = 0; i < filters.size(); ++i) {
+    if (filters[i]->OnMessageReceived(message)) {
+#ifdef IPC_MESSAGE_LOG_ENABLED
+      if (logger->Enabled())
+        logger->OnPostDispatchMessage(message, channel_id);
+#endif
+      return true;
+    }
+  }
+  return false;
+}
+
+}  // namespace
 
 //------------------------------------------------------------------------------
 
 ChannelProxy::MessageFilter::MessageFilter() {}
 
 void ChannelProxy::MessageFilter::OnFilterAdded(Channel* channel) {}
 
 void ChannelProxy::MessageFilter::OnFilterRemoved() {}
 
 void ChannelProxy::MessageFilter::OnChannelConnected(int32 peer_pid) {}
 
 void ChannelProxy::MessageFilter::OnChannelError() {}
 
 void ChannelProxy::MessageFilter::OnChannelClosing() {}
 
 bool ChannelProxy::MessageFilter::OnMessageReceived(const Message& message) {
   return false;
 }
 
+bool ChannelProxy::MessageFilter::GetSupportedMessageClasses(
+    std::vector<uint32>* /*supported_message_classes*/) const {
+  return false;
+}
+
 ChannelProxy::MessageFilter::~MessageFilter() {}
 
 //------------------------------------------------------------------------------
 
 ChannelProxy::Context::Context(Listener* listener,
                                base::SingleThreadTaskRunner* ipc_task_runner)
     : listener_task_runner_(base::ThreadTaskRunnerHandle::Get()),
       listener_(listener),
       ipc_task_runner_(ipc_task_runner),
       channel_connected_called_(false),
@@ skipping 15 matching lines @@
   channel_.reset(new Channel(handle, mode, this));
 }
 
 bool ChannelProxy::Context::TryFilters(const Message& message) {
 #ifdef IPC_MESSAGE_LOG_ENABLED
   Logging* logger = Logging::GetInstance();
   if (logger->Enabled())
     logger->OnPreDispatchMessage(message);
 #endif
 
-  for (size_t i = 0; i < filters_.size(); ++i) {
-    if (filters_[i]->OnMessageReceived(message)) {
-#ifdef IPC_MESSAGE_LOG_ENABLED
-      if (logger->Enabled())
-        logger->OnPostDispatchMessage(message, channel_id_);
-#endif
-      return true;
-    }
+  if (ApplyFilters(message_global_filters_, message, channel_id_))
+    return true;
+
+  MessageClassFilterMap::iterator message_class_filter_it =
+      message_class_filters_.find(IPC_MESSAGE_CLASS(message));
+  if (message_class_filter_it != message_class_filters_.end() &&
+      ApplyFilters(message_class_filter_it->second, message, channel_id_)) {
+    return true;
   }

[piman, 2014/02/11 21:48:46]

So, there is an assumption that filters are run in the order they are added.
I suspect we mostly don't rely on that but we should audit to make sure, since
we're changing the order here.

[jdduke (slow), 2014/02/11 23:01:48]

Good call.  I *think* we're OK in our current form, as all BrowserMessageFilters
will only exist in |message_class_filters_|, and message filter order for any
given class is preserved with respect to |AddFilter()|.  That may be a gotcha
for other ChanneProxy instances where some filters are global and others not.

+
   return false;
 }
 
 // Called on the IPC::Channel thread
 bool ChannelProxy::Context::OnMessageReceived(const Message& message) {
   // First give a chance to the filters to process this message.
   if (!TryFilters(message))
     OnMessageReceivedNoFilter(message);
   return true;
 }
 
 // Called on the IPC::Channel thread
 bool ChannelProxy::Context::OnMessageReceivedNoFilter(const Message& message) {
   listener_task_runner_->PostTask(
       FROM_HERE, base::Bind(&Context::OnDispatchMessage, this, message));
   return true;
 }
 
 // Called on the IPC::Channel thread
 void ChannelProxy::Context::OnChannelConnected(int32 peer_pid) {
   // Add any pending filters.  This avoids a race condition where someone
   // creates a ChannelProxy, calls AddFilter, and then right after starts the
   // peer process.  The IO thread could receive a message before the task to add
   // the filter is run on the IO thread.
   OnAddFilter();
 
   // We cache off the peer_pid so it can be safely accessed from both threads.
   peer_pid_ = channel_->peer_pid();
-  for (size_t i = 0; i < filters_.size(); ++i)
-    filters_[i]->OnChannelConnected(peer_pid);
+  for (size_t i = 0; i < all_filters_.size(); ++i)
+    all_filters_[i]->OnChannelConnected(peer_pid);
 
   // See above comment about using listener_task_runner_ here.
   listener_task_runner_->PostTask(
       FROM_HERE, base::Bind(&Context::OnDispatchConnected, this));
 }
 
 // Called on the IPC::Channel thread
 void ChannelProxy::Context::OnChannelError() {
-  for (size_t i = 0; i < filters_.size(); ++i)
-    filters_[i]->OnChannelError();
+  for (size_t i = 0; i < all_filters_.size(); ++i)
+    all_filters_[i]->OnChannelError();
 
   // See above comment about using listener_task_runner_ here.
   listener_task_runner_->PostTask(
       FROM_HERE, base::Bind(&Context::OnDispatchError, this));
 }
 
 // Called on the IPC::Channel thread
 void ChannelProxy::Context::OnChannelOpened() {
   DCHECK(channel_ != NULL);
 
   // Assume a reference to ourselves on behalf of this thread.  This reference
   // will be released when we are closed.
   AddRef();
 
   if (!channel_->Connect()) {
     OnChannelError();
     return;
   }
 
-  for (size_t i = 0; i < filters_.size(); ++i)
-    filters_[i]->OnFilterAdded(channel_.get());
+  for (size_t i = 0; i < all_filters_.size(); ++i)
+    all_filters_[i]->OnFilterAdded(channel_.get());
 }
 
 // Called on the IPC::Channel thread
 void ChannelProxy::Context::OnChannelClosed() {
   // It's okay for IPC::ChannelProxy::Close to be called more than once, which
   // would result in this branch being taken.
   if (!channel_.get())
     return;
 
-  for (size_t i = 0; i < filters_.size(); ++i) {
-    filters_[i]->OnChannelClosing();
-    filters_[i]->OnFilterRemoved();
+  for (size_t i = 0; i < all_filters_.size(); ++i) {
+    all_filters_[i]->OnChannelClosing();
+    all_filters_[i]->OnFilterRemoved();
   }
 
   // We don't need the filters anymore.
-  filters_.clear();
+  all_filters_.clear();
+  message_global_filters_.clear();
+  message_class_filters_.clear();
 
   channel_.reset();
 
   // Balance with the reference taken during startup.  This may result in
   // self-destruction.
   Release();
 }
 
 void ChannelProxy::Context::Clear() {
   listener_ = NULL;
@@ skipping 10 matching lines @@
 }
 
 // Called on the IPC::Channel thread
 void ChannelProxy::Context::OnAddFilter() {
   std::vector<scoped_refptr<MessageFilter> > new_filters;
   {
     base::AutoLock auto_lock(pending_filters_lock_);
     new_filters.swap(pending_filters_);
   }
 
+  std::vector<uint32> supported_message_classes;
   for (size_t i = 0; i < new_filters.size(); ++i) {
-    filters_.push_back(new_filters[i]);
+    all_filters_.push_back(new_filters[i]);
+
+    // Determine if the filter should be applied to all messages, or only
+    // messages of a certain class.
+    MessageFilter* filter = new_filters[i].get();
+    if (filter->GetSupportedMessageClasses(&supported_message_classes)) {
+      DCHECK(!supported_message_classes.empty());
+      for (size_t i = 0; i < supported_message_classes.size(); ++i)
+        message_class_filters_[supported_message_classes[i]].push_back(filter);
+    } else {
+      message_global_filters_.push_back(filter);
+    }
+    supported_message_classes.clear();
 
     // If the channel has already been created, then we need to send this
     // message so that the filter gets access to the Channel.
     if (channel_.get())
-      new_filters[i]->OnFilterAdded(channel_.get());
+      filter->OnFilterAdded(channel_.get());
     // Ditto for if the channel has been connected.
     if (peer_pid_)
-      new_filters[i]->OnChannelConnected(peer_pid_);
+      filter->OnChannelConnected(peer_pid_);
   }
 }
 
 // Called on the IPC::Channel thread
 void ChannelProxy::Context::OnRemoveFilter(MessageFilter* filter) {
   if (!channel_.get())
     return;  // The filters have already been deleted.
 
-  for (size_t i = 0; i < filters_.size(); ++i) {
-    if (filters_[i].get() == filter) {
+  bool filter_exists = false;
+  for (size_t i = 0; i < all_filters_.size(); ++i) {
+    if (all_filters_[i].get() == filter) {
       filter->OnFilterRemoved();
-      filters_.erase(filters_.begin() + i);
-      return;
+      all_filters_.erase(all_filters_.begin() + i);
+      filter_exists = true;
+      break;
     }
   }
 
-  NOTREACHED() << "filter to be removed not found";
+  if (!filter_exists) {
+    NOTREACHED() << "filter to be removed not found";
+    return;
+  }
+
+  if (EraseFilter(filter, message_global_filters_))
+    return;
+
+  for (MessageClassFilterMap::iterator it = message_class_filters_.begin();
+       it != message_class_filters_.end();
+       ++it) {
+    EraseFilter(filter, it->second);
+  }
 }
 
 // Called on the listener's thread
 void ChannelProxy::Context::AddFilter(MessageFilter* filter) {
   base::AutoLock auto_lock(pending_filters_lock_);
   pending_filters_.push_back(make_scoped_refptr(filter));
   ipc_task_runner_->PostTask(
       FROM_HERE, base::Bind(&Context::OnAddFilter, this));
 }
 
@@ skipping 184 matching lines @@
   Channel* channel = context_.get()->channel_.get();
   // Channel must have been created first.
   DCHECK(channel) << context_.get()->channel_id_;
   return channel->GetPeerEuid(peer_euid);
 }
 #endif
 
 //-----------------------------------------------------------------------------
 
 }  // namespace IPC