fuzz: Add fuzz test for v2 transport {de}serialization

Author: dhruv

src/Makefile.test.include

@@ -261,6 +261,7 @@ test_fuzz_fuzz_SOURCES = \
  test/fuzz/netbase_dns_lookup.cpp \
  test/fuzz/node_eviction.cpp \
  test/fuzz/p2p_transport_serialization.cpp \
+ test/fuzz/p2p_v2_transport_serialization.cpp \
  test/fuzz/parse_hd_keypath.cpp \
  test/fuzz/parse_iso8601.cpp \
  test/fuzz/parse_numbers.cpp \

src/test/fuzz/p2p_v2_transport_serialization.cpp

@@ -0,0 +1,44 @@
+// Copyright (c) 2019-2021 The Bitcoin Core developers
+// Distributed under the MIT software license, see the accompanying
+// file COPYING or http://www.opensource.org/licenses/mit-license.php.
+
+#include <crypto/chacha_poly_aead.h>
+#include <key.h>
+#include <net.h>
+#include <netmessagemaker.h>
+#include <test/fuzz/fuzz.h>
+
+#include <cassert>
+
+FUZZ_TARGET(p2p_v2_transport_serialization)
+{
+    const CPrivKey k1(32, 0);
+    const CPrivKey k2(32, 0);
+
+    // Construct deserializer, with a dummy NodeId
+    V2TransportDeserializer deserializer{(NodeId)0, k1, k2};
+    V2TransportSerializer serializer{k1, k2};
+
+    while (buffer.size() > 0) {
+        const int handled = deserializer.Read(buffer);
+        if (handled < 0) {
+            break;
+        }
+        if (deserializer.Complete()) {
+            const std::chrono::microseconds m_time{std::numeric_limits<int64_t>::max()};
+            bool reject_message{true};
+            bool disconnect{true};
+            CNetMessage result{deserializer.GetMessage(m_time, reject_message, disconnect)};
+            if (!reject_message) {
+                assert(result.m_command.size() <= CMessageHeader::COMMAND_SIZE);
+                assert(result.m_raw_message_size <= buffer.size());
+                assert(result.m_raw_message_size == CHACHA20_POLY1305_AEAD_AAD_LEN + result.m_message_size + CHACHA20_POLY1305_AEAD_TAG_LEN);
+                assert(result.m_time == m_time);
+
+                std::vector<unsigned char> header;
+                auto msg = CNetMsgMaker{result.m_recv.GetVersion()}.Make(result.m_command, MakeUCharSpan(result.m_recv));
+                serializer.prepareForTransport(msg, header);
+            }
+        }
+    }
+}