http2: limit number of invalid incoming frames

Limit the number of invalid input frames, as they may be pointing towards a
misbehaving peer. The limit is currently set to 1000 but could be changed or
made configurable.

This is intended to mitigate CVE-2019-9514.

[This commit differs from the v12.x one due to the lack of
libuv/libuv@ee24ce900e5714c950b248da2b.
See the comment in the test for more details.]

Backport-PR-URL: #29124
PR-URL: #29122
Reviewed-By: Rich Trott <[email protected]>
Reviewed-By: James M Snell <[email protected]>

Author: addaleax

src/node_http2.cc

@@ -1070,6 +1070,10 @@ inline int Http2Session::OnInvalidFrame(nghttp2_session* handle,
 
   DEBUG_HTTP2SESSION2(session, "invalid frame received, code: %d",
                       lib_error_code);
+  if (session->invalid_frame_count_++ > 1000 &&
+      !IsReverted(SECURITY_REVERT_CVE_2019_9514)) {
+    return 1;
+  }
 
   // If the error is fatal or if error code is ERR_STREAM_CLOSED... emit error
   if (nghttp2_is_fatal(lib_error_code) ||

src/node_http2.h

@@ -1076,6 +1076,8 @@ class Http2Session : public AsyncWrap {
   // misbehaving peer. This counter is reset once new streams are being
   // accepted again.
   int32_t rejected_stream_count_ = 0;
+  // Also use the invalid frame count as a measure for rejecting input frames.
+  int32_t invalid_frame_count_ = 0;
 
   void CopyDataIntoOutgoing(const uint8_t* src, size_t src_length);
   void ClearOutgoing(int status);

test/parallel/test-http2-reset-flood.js

@@ -0,0 +1,94 @@
+'use strict';
+const common = require('../common');
+if (!common.hasCrypto)
+  common.skip('missing crypto');
+
+const child_process = require('child_process');
+const http2 = require('http2');
+const net = require('net');
+
+// Verify that creating a number of invalid HTTP/2 streams will eventually
+// result in the peer closing the session.
+// This test uses separate processes for client and server to avoid
+// the two event loops intermixing, as we are writing in a busy loop here.
+
+if (process.argv[2] === 'child') {
+  const server = http2.createServer();
+  server.on('stream', (stream) => {
+    stream.respond({
+      'content-type': 'text/plain',
+      ':status': 200
+    });
+    stream.end('Hello, world!\n');
+  });
+  server.listen(0, () => {
+    process.stdout.write(`${server.address().port}`);
+  });
+  return;
+}
+
+const child = child_process.spawn(process.execPath, [__filename, 'child'], {
+  stdio: ['inherit', 'pipe', 'inherit']
+});
+child.stdout.on('data', common.mustCall((port) => {
+  const h2header = Buffer.alloc(9);
+  const conn = net.connect(+port);
+
+  conn.write('PRI * HTTP/2.0\r\n\r\nSM\r\n\r\n');
+
+  h2header[3] = 4;  // Send a settings frame.
+  conn.write(Buffer.from(h2header));
+
+  let inbuf = Buffer.alloc(0);
+  let state = 'settingsHeader';
+  let settingsFrameLength;
+  conn.on('data', (chunk) => {
+    inbuf = Buffer.concat([inbuf, chunk]);
+    switch (state) {
+      case 'settingsHeader':
+        if (inbuf.length < 9) return;
+        settingsFrameLength = inbuf.readIntBE(0, 3);
+        inbuf = inbuf.slice(9);
+        state = 'readingSettings';
+        // Fallthrough
+      case 'readingSettings':
+        if (inbuf.length < settingsFrameLength) return;
+        inbuf = inbuf.slice(settingsFrameLength);
+        h2header[3] = 4;  // Send a settings ACK.
+        h2header[4] = 1;
+        conn.write(Buffer.from(h2header));
+        state = 'ignoreInput';
+        writeRequests();
+    }
+  });
+
+  let gotError = false;
+
+  let i = 1;
+  function writeRequests() {
+    for (; !gotError; i += 2) {
+      h2header[3] = 1;  // HEADERS
+      h2header[4] = 0x5;  // END_HEADERS|END_STREAM
+      h2header.writeIntBE(1, 0, 3);  // Length: 1
+      h2header.writeIntBE(i, 5, 4);  // Stream ID
+      // 0x88 = :status: 200
+      conn.write(Buffer.concat([h2header, Buffer.from([0x88])]));
+
+      if (i % 1000 === 1) {
+        // Delay writing a bit so we get the chance to actually observe
+        // an error. This is not necessary on master/v12.x, because there
+        // conn.write() can fail directly when writing to a connection
+        // that was closed by the remote peer due to
+        // https://github.com/libuv/libuv/commit/ee24ce900e5714c950b248da2b
+        i += 2;
+        return setImmediate(writeRequests);
+      }
+    }
+  }
+
+  conn.once('error', common.mustCall(() => {
+    gotError = true;
+    child.kill();
+    conn.destroy();
+  }));
+}));