http2: consider 0-length non-end DATA frames an error

This is intended to mitigate CVE-2019-9518.

Backport-PR-URL: #29123
PR-URL: #29122
Reviewed-By: Rich Trott <rtrott@gmail.com>
Reviewed-By: James M Snell <jasnell@gmail.com>

Author: addaleax

src/node_http2.cc

@@ -980,8 +980,7 @@ int Http2Session::OnFrameReceive(nghttp2_session* handle,
         frame->hd.type);
   switch (frame->hd.type) {
     case NGHTTP2_DATA:
-      session->HandleDataFrame(frame);
-      break;
+      return session->HandleDataFrame(frame);
     case NGHTTP2_PUSH_PROMISE:
       // Intentional fall-through, handled just like headers frames
     case NGHTTP2_HEADERS:
@@ -1398,13 +1397,18 @@ void Http2Session::HandlePriorityFrame(const nghttp2_frame* frame) {
 // Called by OnFrameReceived when a complete DATA frame has been received.
 // If we know that this was the last DATA frame (because the END_STREAM flag
 // is set), then we'll terminate the readable side of the StreamBase.
-void Http2Session::HandleDataFrame(const nghttp2_frame* frame) {
+int Http2Session::HandleDataFrame(const nghttp2_frame* frame) {
   int32_t id = GetFrameID(frame);
   Debug(this, "handling data frame for stream %d", id);
   Http2Stream* stream = FindStream(id);
 
-  if (!stream->IsDestroyed() && frame->hd.flags & NGHTTP2_FLAG_END_STREAM)
+  if (!stream->IsDestroyed() && frame->hd.flags & NGHTTP2_FLAG_END_STREAM) {
     stream->EmitRead(UV_EOF);
+  } else if (frame->hd.length == 0 &&
+           !IsReverted(SECURITY_REVERT_CVE_2019_9518)) {
+    return 1;  // Consider 0-length frame without END_STREAM an error.
+  }
+  return 0;
 }
 
 

src/node_http2.h

@@ -889,7 +889,7 @@ class Http2Session : public AsyncWrap, public StreamListener {
                             size_t maxPayloadLen);
 
   // Frame Handler
-  void HandleDataFrame(const nghttp2_frame* frame);
+  int HandleDataFrame(const nghttp2_frame* frame);
   void HandleGoawayFrame(const nghttp2_frame* frame);
   void HandleHeadersFrame(const nghttp2_frame* frame);
   void HandlePriorityFrame(const nghttp2_frame* frame);

src/node_revert.h

@@ -18,6 +18,7 @@ namespace node {
 #define SECURITY_REVERSIONS(XX)                                            \
   XX(CVE_2019_9514, "CVE-2019-9514", "HTTP/2 Reset Flood")                 \
   XX(CVE_2019_9516, "CVE-2019-9516", "HTTP/2 0-Length Headers Leak")       \
+  XX(CVE_2019_9518, "CVE-2019-9518", "HTTP/2 Empty DATA Frame Flooding")   \
 //  XX(CVE_2016_PEND, "CVE-2016-PEND", "Vulnerability Title")
   // TODO(addaleax): Remove all of the above before Node.js 13 as the comment
   // at the start of the file indicates.