tests: Add fuzzing harness for functions in timedata.h

Author: practicalswift

src/Makefile.test.include

@@ -98,6 +98,7 @@ FUZZ_TARGETS = \
   test/fuzz/string \
   test/fuzz/strprintf \
   test/fuzz/sub_net_deserialize \
+  test/fuzz/timedata \
   test/fuzz/transaction \
   test/fuzz/tx_in \
   test/fuzz/tx_in_deserialize \
@@ -853,6 +854,12 @@ test_fuzz_sub_net_deserialize_LDADD = $(FUZZ_SUITE_LD_COMMON)
 test_fuzz_sub_net_deserialize_LDFLAGS = $(RELDFLAGS) $(AM_LDFLAGS) $(LIBTOOL_APP_LDFLAGS)
 test_fuzz_sub_net_deserialize_SOURCES = $(FUZZ_SUITE) test/fuzz/deserialize.cpp
 
+test_fuzz_timedata_CPPFLAGS = $(AM_CPPFLAGS) $(BITCOIN_INCLUDES)
+test_fuzz_timedata_CXXFLAGS = $(AM_CXXFLAGS) $(PIE_FLAGS)
+test_fuzz_timedata_LDADD = $(FUZZ_SUITE_LD_COMMON)
+test_fuzz_timedata_LDFLAGS = $(RELDFLAGS) $(AM_LDFLAGS) $(LIBTOOL_APP_LDFLAGS)
+test_fuzz_timedata_SOURCES = $(FUZZ_SUITE) test/fuzz/timedata.cpp
+
 test_fuzz_transaction_CPPFLAGS = $(AM_CPPFLAGS) $(BITCOIN_INCLUDES)
 test_fuzz_transaction_CXXFLAGS = $(AM_CXXFLAGS) $(PIE_FLAGS)
 test_fuzz_transaction_LDADD = $(FUZZ_SUITE_LD_COMMON)

src/test/fuzz/timedata.cpp

@@ -0,0 +1,29 @@
+// 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 <test/fuzz/FuzzedDataProvider.h>
+#include <test/fuzz/fuzz.h>
+#include <test/fuzz/util.h>
+#include <timedata.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 unsigned int max_size = fuzzed_data_provider.ConsumeIntegralInRange<unsigned int>(0, 1000);
+    // Divide by 2 to avoid signed integer overflow in .median()
+    const int64_t initial_value = fuzzed_data_provider.ConsumeIntegral<int64_t>() / 2;
+    CMedianFilter<int64_t> median_filter{max_size, initial_value};
+    while (fuzzed_data_provider.remaining_bytes() > 0) {
+        (void)median_filter.median();
+        assert(median_filter.size() > 0);
+        assert(static_cast<size_t>(median_filter.size()) == median_filter.sorted().size());
+        assert(static_cast<unsigned int>(median_filter.size()) <= max_size || max_size == 0);
+        // Divide by 2 to avoid signed integer overflow in .median()
+        median_filter.input(fuzzed_data_provider.ConsumeIntegral<int64_t>() / 2);
+    }
+}