tests: Add fuzzing harness for CBufferedFile (streams.h)

Author: practicalswift

src/Makefile.test.include

@@ -30,6 +30,7 @@ FUZZ_TARGETS = \
   test/fuzz/blockundo_deserialize \
   test/fuzz/bloom_filter \
   test/fuzz/bloomfilter_deserialize \
+  test/fuzz/buffered_file \
   test/fuzz/chain \
   test/fuzz/checkqueue \
   test/fuzz/coins_deserialize \
@@ -471,6 +472,12 @@ test_fuzz_bloomfilter_deserialize_LDADD = $(FUZZ_SUITE_LD_COMMON)
 test_fuzz_bloomfilter_deserialize_LDFLAGS = $(RELDFLAGS) $(AM_LDFLAGS) $(LIBTOOL_APP_LDFLAGS)
 test_fuzz_bloomfilter_deserialize_SOURCES = test/fuzz/deserialize.cpp
 
+test_fuzz_buffered_file_CPPFLAGS = $(AM_CPPFLAGS) $(BITCOIN_INCLUDES)
+test_fuzz_buffered_file_CXXFLAGS = $(AM_CXXFLAGS) $(PIE_FLAGS)
+test_fuzz_buffered_file_LDADD = $(FUZZ_SUITE_LD_COMMON)
+test_fuzz_buffered_file_LDFLAGS = $(RELDFLAGS) $(AM_LDFLAGS) $(LIBTOOL_APP_LDFLAGS)
+test_fuzz_buffered_file_SOURCES = test/fuzz/buffered_file.cpp
+
 test_fuzz_chain_CPPFLAGS = $(AM_CPPFLAGS) $(BITCOIN_INCLUDES)
 test_fuzz_chain_CXXFLAGS = $(AM_CXXFLAGS) $(PIE_FLAGS)
 test_fuzz_chain_LDADD = $(FUZZ_SUITE_LD_COMMON)

src/test/fuzz/buffered_file.cpp

@@ -0,0 +1,64 @@
+// 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 <optional.h>
+#include <streams.h>
+#include <test/fuzz/FuzzedDataProvider.h>
+#include <test/fuzz/fuzz.h>
+#include <test/fuzz/util.h>
+
+#include <array>
+#include <cstdint>
+#include <iostream>
+#include <optional>
+#include <string>
+#include <vector>
+
+void test_one_input(const std::vector<uint8_t>& buffer)
+{
+    FuzzedDataProvider fuzzed_data_provider{buffer.data(), buffer.size()};
+    FuzzedFileProvider fuzzed_file_provider = ConsumeFile(fuzzed_data_provider);
+    std::optional<CBufferedFile> opt_buffered_file;
+    FILE* fuzzed_file = fuzzed_file_provider.open();
+    try {
+        opt_buffered_file.emplace(fuzzed_file, fuzzed_data_provider.ConsumeIntegralInRange<uint64_t>(0, 4096), fuzzed_data_provider.ConsumeIntegralInRange<uint64_t>(0, 4096), fuzzed_data_provider.ConsumeIntegral<int>(), fuzzed_data_provider.ConsumeIntegral<int>());
+    } catch (const std::ios_base::failure&) {
+        if (fuzzed_file != nullptr) {
+            fclose(fuzzed_file);
+        }
+    }
+    if (opt_buffered_file && fuzzed_file != nullptr) {
+        while (fuzzed_data_provider.ConsumeBool()) {
+            switch (fuzzed_data_provider.ConsumeIntegralInRange<int>(0, 4)) {
+            case 0: {
+                std::array<uint8_t, 4096> arr{};
+                try {
+                    opt_buffered_file->read((char*)arr.data(), fuzzed_data_provider.ConsumeIntegralInRange<size_t>(0, 4096));
+                } catch (const std::ios_base::failure&) {
+                }
+                break;
+            }
+            case 1: {
+                opt_buffered_file->Seek(fuzzed_data_provider.ConsumeIntegralInRange<uint64_t>(0, 4096));
+                break;
+            }
+            case 2: {
+                opt_buffered_file->SetLimit(fuzzed_data_provider.ConsumeIntegralInRange<uint64_t>(0, 4096));
+                break;
+            }
+            case 3: {
+                try {
+                    opt_buffered_file->FindByte(fuzzed_data_provider.ConsumeIntegral<char>());
+                } catch (const std::ios_base::failure&) {
+                }
+                break;
+            }
+            case 4: {
+                ReadFromStream(fuzzed_data_provider, *opt_buffered_file);
+                break;
+            }
+            }
+        }
+    }
+}