test: add small signet fuzzer

src/Makefile.test.include

@@ -134,6 +134,7 @@ FUZZ_TARGETS = \
   test/fuzz/scriptnum_ops \
   test/fuzz/service_deserialize \
   test/fuzz/signature_checker \
+  test/fuzz/signet \
   test/fuzz/snapshotmetadata_deserialize \
   test/fuzz/span \
   test/fuzz/spanparsing \
@@ -1106,6 +1107,12 @@ test_fuzz_signature_checker_LDADD = $(FUZZ_SUITE_LD_COMMON)
 test_fuzz_signature_checker_LDFLAGS = $(RELDFLAGS) $(AM_LDFLAGS) $(LIBTOOL_APP_LDFLAGS)
 test_fuzz_signature_checker_SOURCES = test/fuzz/signature_checker.cpp
 
+test_fuzz_signet_CPPFLAGS = $(AM_CPPFLAGS) $(BITCOIN_INCLUDES)
+test_fuzz_signet_CXXFLAGS = $(AM_CXXFLAGS) $(PIE_FLAGS)
+test_fuzz_signet_LDADD = $(FUZZ_SUITE_LD_COMMON)
+test_fuzz_signet_LDFLAGS = $(RELDFLAGS) $(AM_LDFLAGS) $(LIBTOOL_APP_LDFLAGS)
+test_fuzz_signet_SOURCES = test/fuzz/signet.cpp
+
 test_fuzz_snapshotmetadata_deserialize_CPPFLAGS = $(AM_CPPFLAGS) $(BITCOIN_INCLUDES) -DSNAPSHOTMETADATA_DESERIALIZE=1
 test_fuzz_snapshotmetadata_deserialize_CXXFLAGS = $(AM_CXXFLAGS) $(PIE_FLAGS)
 test_fuzz_snapshotmetadata_deserialize_LDADD = $(FUZZ_SUITE_LD_COMMON)

src/test/fuzz/signet.cpp

@@ -0,0 +1,34 @@
+// Copyright (c) 2020 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 <chainparams.h>
+#include <consensus/validation.h>
+#include <primitives/block.h>
+#include <signet.h>
+#include <streams.h>
+#include <test/fuzz/fuzz.h>
+#include <test/fuzz/FuzzedDataProvider.h>
+#include <test/fuzz/util.h>
+
+#include <cstdint>
+#include <optional>
+#include <vector>
+
+void initialize()
+{
+    InitializeFuzzingContext(CBaseChainParams::SIGNET);
+}
+
+void test_one_input(const std::vector<uint8_t>& buffer)
+{
+    FuzzedDataProvider fuzzed_data_provider{buffer.data(), buffer.size()};
+    const std::optional<CBlock> block = ConsumeDeserializable<CBlock>(fuzzed_data_provider);
+    if (!block) {
+        return;
+    }
+    (void)CheckSignetBlockSolution(*block, Params().GetConsensus());
+    if (GetWitnessCommitmentIndex(*block) != NO_WITNESS_COMMITMENT) {
+        (void)SignetTxs(*block, ConsumeScript(fuzzed_data_provider));
+    }
+}