tests: Add fuzzing harness for classes/functions in blockfilter.h

Author: practicalswift

src/Makefile.test.include

@@ -17,6 +17,7 @@ FUZZ_TARGETS = \
   test/fuzz/block_filter_deserialize \
   test/fuzz/block_header \
   test/fuzz/block_header_and_short_txids_deserialize \
+  test/fuzz/blockfilter \
   test/fuzz/blockheader_deserialize \
   test/fuzz/blocklocator_deserialize \
   test/fuzz/blockmerkleroot \
@@ -369,6 +370,12 @@ test_fuzz_block_header_and_short_txids_deserialize_LDADD = $(FUZZ_SUITE_LD_COMMO
 test_fuzz_block_header_and_short_txids_deserialize_LDFLAGS = $(RELDFLAGS) $(AM_LDFLAGS) $(LIBTOOL_APP_LDFLAGS)
 test_fuzz_block_header_and_short_txids_deserialize_SOURCES = $(FUZZ_SUITE) test/fuzz/deserialize.cpp
 
+test_fuzz_blockfilter_CPPFLAGS = $(AM_CPPFLAGS) $(BITCOIN_INCLUDES)
+test_fuzz_blockfilter_CXXFLAGS = $(AM_CXXFLAGS) $(PIE_FLAGS)
+test_fuzz_blockfilter_LDADD = $(FUZZ_SUITE_LD_COMMON)
+test_fuzz_blockfilter_LDFLAGS = $(RELDFLAGS) $(AM_LDFLAGS) $(LIBTOOL_APP_LDFLAGS)
+test_fuzz_blockfilter_SOURCES = $(FUZZ_SUITE) test/fuzz/blockfilter.cpp
+
 test_fuzz_blockheader_deserialize_CPPFLAGS = $(AM_CPPFLAGS) $(BITCOIN_INCLUDES) -DBLOCKHEADER_DESERIALIZE=1
 test_fuzz_blockheader_deserialize_CXXFLAGS = $(AM_CXXFLAGS) $(PIE_FLAGS)
 test_fuzz_blockheader_deserialize_LDADD = $(FUZZ_SUITE_LD_COMMON)

src/test/fuzz/blockfilter.cpp

@@ -0,0 +1,44 @@
+// 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 <blockfilter.h>
+#include <optional.h>
+#include <test/fuzz/FuzzedDataProvider.h>
+#include <test/fuzz/fuzz.h>
+#include <test/fuzz/util.h>
+
+#include <cstdint>
+#include <string>
+#include <vector>
+
+void test_one_input(const std::vector<uint8_t>& buffer)
+{
+    FuzzedDataProvider fuzzed_data_provider(buffer.data(), buffer.size());
+    const Optional<BlockFilter> block_filter = ConsumeDeserializable<BlockFilter>(fuzzed_data_provider);
+    if (!block_filter) {
+        return;
+    }
+    {
+        (void)block_filter->ComputeHeader(ConsumeUInt256(fuzzed_data_provider));
+        (void)block_filter->GetBlockHash();
+        (void)block_filter->GetEncodedFilter();
+        (void)block_filter->GetHash();
+    }
+    {
+        const BlockFilterType block_filter_type = block_filter->GetFilterType();
+        (void)BlockFilterTypeName(block_filter_type);
+    }
+    {
+        const GCSFilter gcs_filter = block_filter->GetFilter();
+        (void)gcs_filter.GetN();
+        (void)gcs_filter.GetParams();
+        (void)gcs_filter.GetEncoded();
+        (void)gcs_filter.Match(ConsumeRandomLengthByteVector(fuzzed_data_provider));
+        GCSFilter::ElementSet element_set;
+        while (fuzzed_data_provider.ConsumeBool()) {
+            element_set.insert(ConsumeRandomLengthByteVector(fuzzed_data_provider));
+            gcs_filter.MatchAny(element_set);
+        }
+    }
+}

src/test/fuzz/util.h

@@ -13,6 +13,7 @@
 #include <streams.h>
 #include <test/fuzz/FuzzedDataProvider.h>
 #include <test/fuzz/fuzz.h>
+#include <uint256.h>
 #include <version.h>
 
 #include <cstdint>
@@ -70,6 +71,15 @@ NODISCARD inline CScriptNum ConsumeScriptNum(FuzzedDataProvider& fuzzed_data_pro
     return CScriptNum{fuzzed_data_provider.ConsumeIntegral<int64_t>()};
 }
 
+NODISCARD inline uint256 ConsumeUInt256(FuzzedDataProvider& fuzzed_data_provider) noexcept
+{
+    const std::vector<unsigned char> v256 = fuzzed_data_provider.ConsumeBytes<unsigned char>(sizeof(uint256));
+    if (v256.size() != sizeof(uint256)) {
+        return {};
+    }
+    return uint256{v256};
+}
+
 template <typename T>
 bool MultiplicationOverflow(T i, T j)
 {