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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: #29122
Reviewed-By: Rich Trott <rtrott@gmail.com>
Reviewed-By: James M Snell <jasnell@gmail.com>
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addaleax authored and targos committed Aug 10, 2019
1 parent 88726f2 commit 4570ed10d7f642882097b23172e87b4e4cde6e9b
Showing with 16 additions and 1 deletion.
  1. +7 −0 src/node_http2.cc
  2. +5 −0 src/node_http2.h
  3. +4 −1 src/node_revert.h
@@ -6,6 +6,7 @@
#include "node_http2.h"
#include "node_http2_state.h"
#include "node_perf.h"
#include "node_revert.h"
#include "util-inl.h"

#include <algorithm>
@@ -921,11 +922,17 @@ int Http2Session::OnBeginHeadersCallback(nghttp2_session* handle,
if (UNLIKELY(!session->CanAddStream() ||
Http2Stream::New(session, id, frame->headers.cat) ==
nullptr)) {
if (session->rejected_stream_count_++ > 100 &&
!IsReverted(SECURITY_REVERT_CVE_2019_9514)) {
return NGHTTP2_ERR_CALLBACK_FAILURE;
}
// Too many concurrent streams being opened
nghttp2_submit_rst_stream(**session, NGHTTP2_FLAG_NONE, id,
NGHTTP2_ENHANCE_YOUR_CALM);
return NGHTTP2_ERR_TEMPORAL_CALLBACK_FAILURE;
}

session->rejected_stream_count_ = 0;
} else if (!stream->IsDestroyed()) {
stream->StartHeaders(frame->headers.cat);
}
@@ -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);
@@ -15,8 +15,11 @@
**/
namespace node {

#define SECURITY_REVERSIONS(XX)
#define SECURITY_REVERSIONS(XX) \
XX(CVE_2019_9514, "CVE-2019-9514", "HTTP/2 Reset Flood") \
// 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.

enum reversion {
#define V(code, ...) SECURITY_REVERT_##code,

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