Merge #19247: tests: Add fuzzing harness for {Read,Write}{LE,BE}{16,32,64} (crypto/common.h)

cf5b8f64b3fef053035fa11231601b79bfa53aff tests: Add fuzzing harness for {Read,Write}{LE,BE}{16,32,64} (crypto/common.h) (practicalswift)
4a8181b303218683d014e8e79a172ea8ccccc4dd tests: Add std::vector<uint8_t> ConsumeFixedLengthByteVector(FuzzedDataProvider& fuzzed_data_provider, const size_t length) (practicalswift)

Pull request description:

  Add fuzzing harness for `{Read,Write}{LE,BE}{16,32,64}` (`crypto/common.h`).

  See [`doc/fuzzing.md`](https://github.com/bitcoin/bitcoin/blob/master/doc/fuzzing.md) for information on how to fuzz Bitcoin Core. Don't forget to contribute any coverage increasing inputs you find to the [Bitcoin Core fuzzing corpus repo](https://github.com/bitcoin-core/qa-assets).

  Happy fuzzing :)

ACKs for top commit:
  MarcoFalke:
    ACK cf5b8f64b3fef053035fa11231601b79bfa53aff

Tree-SHA512: 26412daa6987add1c721ad0348a5a894d68a646e724f328f2db6d9c9358a533481d8888b89d4b0743e9d1c11aa4e0e5341eb4c0d05a4da77b15ab75489327749

3 files changed, 91 insertions, 0 deletions

diff --git a/src/Makefile.test.include b/src/Makefile.test.include
index 7909cb4a0f..03cd9133c8 100644
--- a/src/Makefile.test.include
+++ b/src/Makefile.test.include
@@ -32,6 +32,7 @@ FUZZ_TARGETS = \
   test/fuzz/checkqueue \
   test/fuzz/coins_deserialize \
   test/fuzz/coins_view \
+  test/fuzz/crypto_common \
   test/fuzz/cuckoocache \
   test/fuzz/decode_tx \
   test/fuzz/descriptor_parse \
@@ -478,6 +479,12 @@ test_fuzz_coins_view_LDADD = $(FUZZ_SUITE_LD_COMMON)
 test_fuzz_coins_view_LDFLAGS = $(RELDFLAGS) $(AM_LDFLAGS) $(LIBTOOL_APP_LDFLAGS)
 test_fuzz_coins_view_SOURCES = test/fuzz/coins_view.cpp
 
+test_fuzz_crypto_common_CPPFLAGS = $(AM_CPPFLAGS) $(BITCOIN_INCLUDES)
+test_fuzz_crypto_common_CXXFLAGS = $(AM_CXXFLAGS) $(PIE_FLAGS)
+test_fuzz_crypto_common_LDADD = $(FUZZ_SUITE_LD_COMMON)
+test_fuzz_crypto_common_LDFLAGS = $(RELDFLAGS) $(AM_LDFLAGS) $(LIBTOOL_APP_LDFLAGS)
+test_fuzz_crypto_common_SOURCES = test/fuzz/crypto_common.cpp
+
 test_fuzz_cuckoocache_CPPFLAGS = $(AM_CPPFLAGS) $(BITCOIN_INCLUDES)
 test_fuzz_cuckoocache_CXXFLAGS = $(AM_CXXFLAGS) $(PIE_FLAGS)
 test_fuzz_cuckoocache_LDADD = $(FUZZ_SUITE_LD_COMMON)
diff --git a/src/test/fuzz/crypto_common.cpp b/src/test/fuzz/crypto_common.cpp
new file mode 100644
index 0000000000..7ccb125216
--- /dev/null
+++ b/src/test/fuzz/crypto_common.cpp
@@ -0,0 +1,70 @@
+// 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 <crypto/common.h>
+#include <test/fuzz/FuzzedDataProvider.h>
+#include <test/fuzz/fuzz.h>
+#include <test/fuzz/util.h>
+
+#include <array>
+#include <cassert>
+#include <cstdint>
+#include <cstring>
+#include <vector>
+
+void test_one_input(const std::vector<uint8_t>& buffer)
+{
+    FuzzedDataProvider fuzzed_data_provider{buffer.data(), buffer.size()};
+    const uint16_t random_u16 = fuzzed_data_provider.ConsumeIntegral<uint16_t>();
+    const uint32_t random_u32 = fuzzed_data_provider.ConsumeIntegral<uint32_t>();
+    const uint64_t random_u64 = fuzzed_data_provider.ConsumeIntegral<uint64_t>();
+    const std::vector<uint8_t> random_bytes_2 = ConsumeFixedLengthByteVector(fuzzed_data_provider, 2);
+    const std::vector<uint8_t> random_bytes_4 = ConsumeFixedLengthByteVector(fuzzed_data_provider, 4);
+    const std::vector<uint8_t> random_bytes_8 = ConsumeFixedLengthByteVector(fuzzed_data_provider, 8);
+
+    std::array<uint8_t, 2> writele16_arr;
+    WriteLE16(writele16_arr.data(), random_u16);
+    assert(ReadLE16(writele16_arr.data()) == random_u16);
+
+    std::array<uint8_t, 4> writele32_arr;
+    WriteLE32(writele32_arr.data(), random_u32);
+    assert(ReadLE32(writele32_arr.data()) == random_u32);
+
+    std::array<uint8_t, 8> writele64_arr;
+    WriteLE64(writele64_arr.data(), random_u64);
+    assert(ReadLE64(writele64_arr.data()) == random_u64);
+
+    std::array<uint8_t, 4> writebe32_arr;
+    WriteBE32(writebe32_arr.data(), random_u32);
+    assert(ReadBE32(writebe32_arr.data()) == random_u32);
+
+    std::array<uint8_t, 8> writebe64_arr;
+    WriteBE64(writebe64_arr.data(), random_u64);
+    assert(ReadBE64(writebe64_arr.data()) == random_u64);
+
+    const uint16_t readle16_result = ReadLE16(random_bytes_2.data());
+    std::array<uint8_t, 2> readle16_arr;
+    WriteLE16(readle16_arr.data(), readle16_result);
+    assert(std::memcmp(random_bytes_2.data(), readle16_arr.data(), 2) == 0);
+
+    const uint32_t readle32_result = ReadLE32(random_bytes_4.data());
+    std::array<uint8_t, 4> readle32_arr;
+    WriteLE32(readle32_arr.data(), readle32_result);
+    assert(std::memcmp(random_bytes_4.data(), readle32_arr.data(), 4) == 0);
+
+    const uint64_t readle64_result = ReadLE64(random_bytes_8.data());
+    std::array<uint8_t, 8> readle64_arr;
+    WriteLE64(readle64_arr.data(), readle64_result);
+    assert(std::memcmp(random_bytes_8.data(), readle64_arr.data(), 8) == 0);
+
+    const uint32_t readbe32_result = ReadBE32(random_bytes_4.data());
+    std::array<uint8_t, 4> readbe32_arr;
+    WriteBE32(readbe32_arr.data(), readbe32_result);
+    assert(std::memcmp(random_bytes_4.data(), readbe32_arr.data(), 4) == 0);
+
+    const uint64_t readbe64_result = ReadBE64(random_bytes_8.data());
+    std::array<uint8_t, 8> readbe64_arr;
+    WriteBE64(readbe64_arr.data(), readbe64_result);
+    assert(std::memcmp(random_bytes_8.data(), readbe64_arr.data(), 8) == 0);
+}
diff --git a/src/test/fuzz/util.h b/src/test/fuzz/util.h
index f26878a704..1c1b2cd254 100644
--- a/src/test/fuzz/util.h
+++ b/src/test/fuzz/util.h
@@ -214,4 +214,18 @@ NODISCARD inline bool ContainsSpentInput(const CTransaction& tx, const CCoinsVie
     return false;
 }
 
+/**
+ * Returns a byte vector of specified size regardless of the number of remaining bytes available
+ * from the fuzzer. Pads with zero value bytes if needed to achieve the specified size.
+ */
+NODISCARD inline std::vector<uint8_t> ConsumeFixedLengthByteVector(FuzzedDataProvider& fuzzed_data_provider, const size_t length) noexcept
+{
+    std::vector<uint8_t> result(length);
+    const std::vector<uint8_t> random_bytes = fuzzed_data_provider.ConsumeBytes<uint8_t>(length);
+    if (!random_bytes.empty()) {
+        std::memcpy(result.data(), random_bytes.data(), random_bytes.size());
+    }
+    return result;
+}
+
 #endif // BITCOIN_TEST_FUZZ_UTIL_H