tests: Add fuzzing harness for Bech32 encoding/decoding

src/Makefile.test.include

@@ -7,6 +7,7 @@ FUZZ_TARGETS = \
   test/fuzz/address_deserialize \
   test/fuzz/addrman_deserialize \
   test/fuzz/banentry_deserialize \
+  test/fuzz/bech32 \
   test/fuzz/block_deserialize \
   test/fuzz/blockheader_deserialize \
   test/fuzz/blocklocator_deserialize \
@@ -65,11 +66,13 @@ BITCOIN_TEST_SUITE = \
   test/util/str.cpp
 
 FUZZ_SUITE = \
-  test/setup_common.h \
-  test/setup_common.cpp \
   test/fuzz/fuzz.cpp \
   test/fuzz/fuzz.h \
-  test/fuzz/FuzzedDataProvider.h
+  test/fuzz/FuzzedDataProvider.h \
+  test/setup_common.cpp \
+  test/setup_common.h \
+  test/util/str.cpp \
+  test/util/str.h
 
 FUZZ_SUITE_LD_COMMON = \
  $(LIBBITCOIN_SERVER) \
@@ -242,6 +245,12 @@ test_fuzz_banentry_deserialize_CXXFLAGS = $(AM_CXXFLAGS) $(PIE_FLAGS)
 test_fuzz_banentry_deserialize_LDFLAGS = $(RELDFLAGS) $(AM_LDFLAGS) $(LIBTOOL_APP_LDFLAGS)
 test_fuzz_banentry_deserialize_LDADD = $(FUZZ_SUITE_LD_COMMON)
 
+test_fuzz_bech32_SOURCES = $(FUZZ_SUITE) test/fuzz/bech32.cpp
+test_fuzz_bech32_CPPFLAGS = $(AM_CPPFLAGS) $(BITCOIN_INCLUDES)
+test_fuzz_bech32_CXXFLAGS = $(AM_CXXFLAGS) $(PIE_FLAGS)
+test_fuzz_bech32_LDFLAGS = $(RELDFLAGS) $(AM_LDFLAGS) $(LIBTOOL_APP_LDFLAGS)
+test_fuzz_bech32_LDADD = $(FUZZ_SUITE_LD_COMMON)
+
 test_fuzz_txundo_deserialize_SOURCES = $(FUZZ_SUITE) test/fuzz/deserialize.cpp
 test_fuzz_txundo_deserialize_CPPFLAGS = $(AM_CPPFLAGS) $(BITCOIN_INCLUDES) -DTXUNDO_DESERIALIZE=1
 test_fuzz_txundo_deserialize_CXXFLAGS = $(AM_CXXFLAGS) $(PIE_FLAGS)

src/test/fuzz/bech32.cpp

@@ -0,0 +1,43 @@
+// Copyright (c) 2019 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 <bech32.h>
+#include <test/fuzz/fuzz.h>
+#include <test/util/str.h>
+#include <util/strencodings.h>
+
+#include <cassert>
+#include <cstdint>
+#include <string>
+#include <utility>
+#include <vector>
+
+void test_one_input(const std::vector<uint8_t>& buffer)
+{
+    const std::string random_string(buffer.begin(), buffer.end());
+    const std::pair<std::string, std::vector<uint8_t>> r1 = bech32::Decode(random_string);
+    if (r1.first.empty()) {
+        assert(r1.second.empty());
+    } else {
+        const std::string& hrp = r1.first;
+        const std::vector<uint8_t>& data = r1.second;
+        const std::string reencoded = bech32::Encode(hrp, data);
+        assert(CaseInsensitiveEqual(random_string, reencoded));
+    }
+
+    std::vector<unsigned char> input;
+    ConvertBits<8, 5, true>([&](unsigned char c) { input.push_back(c); }, buffer.begin(), buffer.end());
+    const std::string encoded = bech32::Encode("bc", input);
+    assert(!encoded.empty());
+
+    const std::pair<std::string, std::vector<uint8_t>> r2 = bech32::Decode(encoded);
+    if (r2.first.empty()) {
+        assert(r2.second.empty());
+    } else {
+        const std::string& hrp = r2.first;
+        const std::vector<uint8_t>& data = r2.second;
+        assert(hrp == "bc");
+        assert(data == input);
+    }
+}