tests: Add fuzzing harness for functions in script/sigcache.h

src/test/fuzz/script_sigcache.cpp

@@ -0,0 +1,45 @@
+// 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 <chainparams.h>
+#include <chainparamsbase.h>
+#include <key.h>
+#include <pubkey.h>
+#include <script/sigcache.h>
+#include <test/fuzz/FuzzedDataProvider.h>
+#include <test/fuzz/fuzz.h>
+#include <test/fuzz/util.h>
+
+#include <cstdint>
+#include <optional>
+#include <string>
+#include <vector>
+
+void initialize()
+{
+    static const ECCVerifyHandle ecc_verify_handle;
+    ECC_Start();
+    SelectParams(CBaseChainParams::REGTEST);
+    InitSignatureCache();
+}
+
+void test_one_input(const std::vector<uint8_t>& buffer)
+{
+    FuzzedDataProvider fuzzed_data_provider(buffer.data(), buffer.size());
+
+    const std::optional<CMutableTransaction> mutable_transaction = ConsumeDeserializable<CMutableTransaction>(fuzzed_data_provider);
+    const CTransaction tx = mutable_transaction ? CTransaction{*mutable_transaction} : CTransaction{};
+    const unsigned int n_in = fuzzed_data_provider.ConsumeIntegral<unsigned int>();
+    const CAmount amount = ConsumeMoney(fuzzed_data_provider);
+    const bool store = fuzzed_data_provider.ConsumeBool();
+    PrecomputedTransactionData tx_data;
+    CachingTransactionSignatureChecker caching_transaction_signature_checker{mutable_transaction ? &tx : nullptr, n_in, amount, store, tx_data};
+    const std::optional<CPubKey> pub_key = ConsumeDeserializable<CPubKey>(fuzzed_data_provider);
+    if (pub_key) {
+        const std::vector<uint8_t> random_bytes = ConsumeRandomLengthByteVector(fuzzed_data_provider);
+        if (!random_bytes.empty()) {
+            (void)caching_transaction_signature_checker.VerifySignature(random_bytes, *pub_key, ConsumeUInt256(fuzzed_data_provider));
+        }
+    }
+}