http2: limit number of rejected stream openings

Limit the number of streams that are rejected upon creation. Since
each such rejection is associated with an `NGHTTP2_ENHANCE_YOUR_CALM`
error that should tell the peer to not open any more streams,
continuing to open streams should be read as a sign of a misbehaving
peer. The limit is currently set to 100 but could be changed or made
configurable.

This is intended to mitigate CVE-2019-9514.

PR-URL: https://github.com/nodejs/node/pull/29122
Reviewed-By: Rich Trott <rtrott@gmail.com>
Reviewed-By: James M Snell <jasnell@gmail.com>

1 files changed, 5 insertions, 0 deletions

diff --git a/src/node_http2.h b/src/node_http2.h
index 47d25f2b07..1739a29b25 100644
--- a/src/node_http2.h
+++ b/src/node_http2.h
@@ -1005,6 +1005,11 @@ class Http2Session : public AsyncWrap, public StreamListener {
   std::vector<nghttp2_stream_write> outgoing_buffers_;
   std::vector<uint8_t> outgoing_storage_;
   std::vector<int32_t> pending_rst_streams_;
+  // Count streams that have been rejected while being opened. Exceeding a fixed
+  // limit will result in the session being destroyed, as an indication of a
+  // misbehaving peer. This counter is reset once new streams are being
+  // accepted again.
+  int32_t rejected_stream_count_ = 0;
 
   void CopyDataIntoOutgoing(const uint8_t* src, size_t src_length);
   void ClearOutgoing(int status);