Use MIDIMessageQueue/IsValidWebMIDIData for MIDI byte stream validation

content/browser/renderer_host/media/midi_host.cc

Index: content/browser/renderer_host/media/midi_host.cc
diff --git a/content/browser/renderer_host/media/midi_host.cc b/content/browser/renderer_host/media/midi_host.cc
index 934d5a21f1839fa97a5740fc60d28bba1936a05a..d6781f61df56e2bb27d04fe0f31dfcd82f3839ea 100644
--- a/content/browser/renderer_host/media/midi_host.cc
+++ b/content/browser/renderer_host/media/midi_host.cc
@@ -16,26 +16,41 @@
 #include "content/public/browser/media_observer.h"
 #include "content/public/browser/user_metrics.h"
 #include "media/midi/midi_manager.h"
+#include "media/midi/midi_message_queue.h"
+#include "media/midi/midi_message_util.h"
 
 using media::MIDIManager;
 using media::MIDIPortInfoList;
 
+namespace content {
+namespace {
+
 // The total number of bytes which we're allowed to send to the OS
 // before knowing that they have been successfully sent.
-static const size_t kMaxInFlightBytes = 10 * 1024 * 1024;  // 10 MB.
+const size_t kMaxInFlightBytes = 10 * 1024 * 1024;  // 10 MB.
 
 // We keep track of the number of bytes successfully sent to
 // the hardware.  Every once in a while we report back to the renderer
 // the number of bytes sent since the last report. This threshold determines
 // how many bytes will be sent before reporting back to the renderer.
-static const size_t kAcknowledgementThresholdBytes = 1024 * 1024;  // 1 MB.
+const size_t kAcknowledgementThresholdBytes = 1024 * 1024;  // 1 MB.
 
-static const uint8 kSysExMessage = 0xf0;
+const uint8 kSysExMessage = 0xf0;
+const uint8 kEndOfSysExMessage = 0xf7;
 
-namespace content {
+bool IsDataByte(uint8 data) {
+  return (data & 0x80) == 0;
+}
+
+bool IsSystemRealTimeMessage(uint8 data) {
+  return 0xf8 <= data && data <= 0xff;
+}
+
+}  // namespace
 
 MIDIHost::MIDIHost(int renderer_process_id, media::MIDIManager* midi_manager)
     : renderer_process_id_(renderer_process_id),
+      has_sys_ex_permission_(false),
       midi_manager_(midi_manager),
       sent_bytes_in_flight_(0),
       bytes_sent_since_last_acknowledgement_(0) {
@@ -75,6 +90,12 @@ void MIDIHost::OnStartSession(int client_id) {
     if (success) {
       input_ports = midi_manager_->input_ports();
       output_ports = midi_manager_->output_ports();
+      received_messages_queues_.clear();
+      received_messages_queues_.resize(input_ports.size());
+      // ChildSecurityPolicy is set just before OnStartSession by
+      // MIDIDispatcherHost. So we can safely cache the policy.
+      has_sys_ex_permission_ = ChildProcessSecurityPolicyImpl::GetInstance()->
+          CanSendMIDISysExMessage(renderer_process_id_);
     }
   }
 
@@ -94,32 +115,26 @@ void MIDIHost::OnSendData(uint32 port,
   if (data.empty())
     return;
 
-  base::AutoLock auto_lock(in_flight_lock_);
-
-  // Sanity check that we won't send too much.
-  if (sent_bytes_in_flight_ > kMaxInFlightBytes ||
-      data.size() > kMaxInFlightBytes ||
-      data.size() + sent_bytes_in_flight_ > kMaxInFlightBytes)
+  // Blink running in a renderer checks permission to raise a SecurityError
+  // in JavaScript. The actual permission check for security purposes
+  // happens here in the browser process.
+  if (!has_sys_ex_permission_ &&
+      (std::find(data.begin(), data.end(), kSysExMessage) != data.end())) {
+    RecordAction(UserMetricsAction("BadMessageTerminate_MIDI"));
+    BadMessageReceived();
     return;
-
-  if (data[0] >= kSysExMessage) {
-    // Blink running in a renderer checks permission to raise a SecurityError in
-    // JavaScript. The actual permission check for security perposes happens
-    // here in the browser process.
-    if (!ChildProcessSecurityPolicyImpl::GetInstance()->CanSendMIDISysExMessage(
-        renderer_process_id_)) {
-      RecordAction(UserMetricsAction("BadMessageTerminate_MIDI"));
-      BadMessageReceived();
-      return;
-    }
   }
 
-  midi_manager_->DispatchSendMIDIData(
-      this,
-      port,
-      data,
-      timestamp);
+  if (!IsValidWebMIDIData(data))
+    return;
 
+  base::AutoLock auto_lock(in_flight_lock_);
+  // Sanity check that we won't send too much data.
+  // TODO(yukawa): Consider to send an error event back to the renderer
+  // after some future discussion in W3C.
+  if (data.size() + sent_bytes_in_flight_ > kMaxInFlightBytes)
+    return;
+  midi_manager_->DispatchSendMIDIData(this, port, data, timestamp);
   sent_bytes_in_flight_ += data.size();
 }
 
@@ -130,20 +145,29 @@ void MIDIHost::ReceiveMIDIData(
     double timestamp) {
   TRACE_EVENT0("midi", "MIDIHost::ReceiveMIDIData");
 
-  // Check a process security policy to receive a system exclusive message.
-  if (length > 0 && data[0] >= kSysExMessage) {
-    if (!ChildProcessSecurityPolicyImpl::GetInstance()->CanSendMIDISysExMessage(
-        renderer_process_id_)) {
-      // MIDI devices may send a system exclusive messages even if the renderer
-      // doesn't have a permission to receive it. Don't kill the renderer as
-      // OnSendData() does.
-      return;
-    }
-  }
+  if (received_messages_queues_.size() <= port)
+    return;
 
-  // Send to the renderer.
-  std::vector<uint8> v(data, data + length);
-  Send(new MIDIMsg_DataReceived(port, v, timestamp));
+  // Lazy initialization
+  if (received_messages_queues_[port] == NULL)
+    received_messages_queues_[port] = new media::MIDIMessageQueue(true);
+
+  received_messages_queues_[port]->Add(data, length);
+  std::vector<uint8> message;
+  while (true) {
+    received_messages_queues_[port]->Get(&message);
+    if (message.empty())
+      break;
+
+    // MIDI devices may send a system exclusive messages even if the renderer
+    // doesn't have a permission to receive it. Don't kill the renderer as
+    // OnSendData() does.
+    if (message[0] == kSysExMessage && !has_sys_ex_permission_)
+      continue;
+
+    // Send to the renderer.
+    Send(new MIDIMsg_DataReceived(port, message, timestamp));
+  }
 }
 
 void MIDIHost::AccumulateMIDIBytesSent(size_t n) {
@@ -165,4 +189,37 @@ void MIDIHost::AccumulateMIDIBytesSent(size_t n) {
   }
 }
 
+// static
+bool MIDIHost::IsValidWebMIDIData(const std::vector<uint8>& data) {
+  bool in_sysex = false;
+  size_t waiting_data_length = 0;
+  for (size_t i = 0; i < data.size(); ++i) {
+    const uint8 current = data[i];
+    if (IsSystemRealTimeMessage(current))
+      continue;  // Real time message can be placed at any point.
+    if (waiting_data_length > 0) {
+      if (!IsDataByte(current))
+        return false;  // Error: |current| should have been data byte.
+      --waiting_data_length;
+      continue;  // Found data byte as expected.
+    }
+    if (in_sysex) {
+      if (data[i] == kEndOfSysExMessage)
+        in_sysex = false;
+      else if (!IsDataByte(current))
+        return false;  // Error: |current| should have been data byte.
+      continue;  // Found data byte as expected.
+    }
+    if (current == kSysExMessage) {
+      in_sysex = true;
+      continue;  // Found SysEX
+    }
+    waiting_data_length = media::GetMIDIMessageLength(current);
+    if (waiting_data_length == 0)
+      return false;  // Error: |current| should have been a valid status byte.
+    --waiting_data_length;  // Found status byte
+  }
+  return waiting_data_length == 0 && !in_sysex;
+}
+
 }  // namespace content