fuzz: add extended fuzzer using FuzzedDataProvider

Similar in nature to fuzz_target.cc but adds the difference of a random
iv constructed by way of fuzzer data.

fuzz/fuzz_target_fdp.cc

@@ -0,0 +1,98 @@
+#include <string>
+#include <vector>
+#include <fuzzer/FuzzedDataProvider.h>
+
+#include <nghttp2/nghttp2.h>
+
+namespace {
+int on_frame_recv_callback(nghttp2_session *session, const nghttp2_frame *frame,
+                           void *user_data) {
+  return 0;
+}
+} // namespace
+
+namespace {
+int on_begin_headers_callback(nghttp2_session *session,
+                              const nghttp2_frame *frame, void *user_data) {
+  return 0;
+}
+} // namespace
+
+namespace {
+int on_header_callback2(nghttp2_session *session, const nghttp2_frame *frame,
+                        nghttp2_rcbuf *name, nghttp2_rcbuf *value,
+                        uint8_t flags, void *user_data) {
+  return 0;
+}
+} // namespace
+
+namespace {
+int before_frame_send_callback(nghttp2_session *session,
+                               const nghttp2_frame *frame, void *user_data) {
+  return 0;
+}
+} // namespace
+
+namespace {
+int on_frame_send_callback(nghttp2_session *session, const nghttp2_frame *frame,
+                           void *user_data) {
+  return 0;
+}
+} // namespace
+
+namespace {
+void send_pending(nghttp2_session *session) {
+  for (;;) {
+    const uint8_t *data;
+    auto n = nghttp2_session_mem_send(session, &data);
+    if (n == 0) {
+      return;
+    }
+  }
+}
+} // namespace
+
+extern "C" int LLVMFuzzerTestOneInput(const uint8_t *data, size_t size) {
+  nghttp2_session *session;
+  nghttp2_session_callbacks *callbacks;
+
+  nghttp2_session_callbacks_new(&callbacks);
+  nghttp2_session_callbacks_set_on_frame_recv_callback(callbacks,
+                                                       on_frame_recv_callback);
+  nghttp2_session_callbacks_set_on_begin_headers_callback(
+      callbacks, on_begin_headers_callback);
+  nghttp2_session_callbacks_set_on_header_callback2(callbacks,
+                                                    on_header_callback2);
+  nghttp2_session_callbacks_set_before_frame_send_callback(
+      callbacks, before_frame_send_callback);
+  nghttp2_session_callbacks_set_on_frame_send_callback(callbacks,
+                                                       on_frame_send_callback);
+
+  nghttp2_session_server_new(&session, callbacks, nullptr);
+  nghttp2_session_callbacks_del(callbacks);
+
+  FuzzedDataProvider data_provider(data, size);
+
+  /* Initialise a random iv */
+  nghttp2_settings_entry *iv;
+  int size_of_iv = data_provider.ConsumeIntegralInRange(1, 10);
+  iv = (nghttp2_settings_entry*)malloc(sizeof(nghttp2_settings_entry)*size_of_iv);
+  for (int i = 0; i < size_of_iv; i++) {
+    iv[i].settings_id = data_provider.ConsumeIntegralInRange(0, 1000);
+    iv[i].value = data_provider.ConsumeIntegralInRange(0, 1000);
+  }
+
+  nghttp2_submit_settings(session, NGHTTP2_FLAG_NONE, iv, size_of_iv);
+  send_pending(session);
+
+  std::vector<uint8_t> d = data_provider.ConsumeRemainingBytes<uint8_t>();
+  nghttp2_session_mem_recv(session, d.data(), d.size());
+
+  send_pending(session);
+
+  nghttp2_session_del(session);
+
+  free(iv);
+
+  return 0;
+}