[backports] tests: Skip unnecessary fuzzer initialisation. Hold ECCVe…

…rifyHandle only when needed.

Summary:
This diff squashes three Core PRs into one. The reason is that [[bitcoin/bitcoin#17235 | PR17235]] introduces a bug, and [[bitcoin/bitcoin#17274 | PR17274]] and [[bitcoin/bitcoin#17685 | PR17685]] both fix it, so our fuzzing test setup isn't broken at any point.

---

c2f964a6745be085f2891c909d6c998687de9080 tests: Remove Cygwin WinMain workaround (practicalswift)
db4bd32cc31789fc017f5db0b86a69ee43e41575 tests: Skip unnecessary fuzzer initialisation. Hold ECCVerifyHandle only when needed. (practicalswift)

Pull request description:

  Skip unnecessary fuzzer initialisation. Hold `ECCVerifyHandle` only when needed.

  As suggested by MarcoFalke in bitcoin/bitcoin#17018 (comment).

---

Merge #17274: tests: Fix fuzzers eval_script and script_flags by re-adding ECCVerifyHandle dependency

9cae3d5e94f4481e0d251c924314e57187a07a60 tests: Add fuzzer initialization (hold ECCVerifyHandle) (practicalswift)

Pull request description:

  The fuzzers `eval_script` and `script_flags` require holding `ECCVerifyHandle`.

  This is a follow-up to #17235 which accidentally broke those two fuzzers.

  Sorry about the temporary breakage my fuzzing friends: it took a while to fuzz before reaching these code paths. That's why this wasn't immediately caught. Sorry.

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Merge #17685: tests: Fix bug in the descriptor parsing fuzzing harness (descriptor_parse)

6338c0203416a5f86e9422b6cd479da8af277f2f tests: Fix fuzzing harness for descriptor parsing (descriptor_parse) (practicalswift)

Pull request description:

  Fix bug in the descriptor parsing fuzzing harness (`descriptor_parse`) by making sure `secp256k1_context_verify` is properly initialized (via `ECCVerifyHandle`).

  Background:

  When fuzzing `Parse(…)` with `libFuzzer` I eventually reached the test case `combo(020000000000000000000000000000000000000000000000000000000000000000)`. That input triggers a call to `CPubKey::IsFullyValid()` which in turns requires an initialized `secp256k1_context_verify`.

  The fuzzing harness did not fulfil that pre-condition prior to this commit (sorry, my fault!) :)

---

Depends on D6881

Backport of Core [[bitcoin/bitcoin#17235 | PR17235]], [[bitcoin/bitcoin#17274 | PR17274]] and [[bitcoin/bitcoin#17685 | PR17685]]

Test Plan:
  cmake -GNinja .. -DENABLE_SANITIZERS="address;fuzzer" -DCMAKE_C_COMPILER=clang -DCMAKE_CXX_COMPILER=clang++
  ninja bitcoin-fuzzers link-fuzz-test_runner.py
  ./test/fuzz/test-runner.py -l DEBUG <path-to-corpus>

Reviewers: #bitcoin_abc, Fabien

Reviewed By: #bitcoin_abc, Fabien

Differential Revision: https://reviews.bitcoinabc.org/D6883

src/test/fuzz/descriptor_parse.cpp

@@ -3,10 +3,14 @@
 // file COPYING or http://www.opensource.org/licenses/mit-license.php.
 
 #include <chainparams.h>
+#include <pubkey.h>
 #include <script/descriptor.h>
 #include <test/fuzz/fuzz.h>
 
+#include <memory>
+
 void initialize() {
+    static const auto verify_handle = std::make_unique<ECCVerifyHandle>();
     SelectParams(CBaseChainParams::REGTEST);
 }
 

src/test/fuzz/deserialize.cpp

@@ -12,6 +12,7 @@
 #include <net.h>
 #include <primitives/block.h>
 #include <protocol.h>
+#include <pubkey.h>
 #include <streams.h>
 #include <undo.h>
 #include <version.h>
@@ -22,6 +23,11 @@
 #include <unistd.h>
 #include <vector>
 
+void initialize() {
+    // Fuzzers using pubkey must hold an ECCVerifyHandle.
+    static const auto verify_handle = std::make_unique<ECCVerifyHandle>();
+}
+
 void test_one_input(const std::vector<uint8_t> &buffer) {
     CDataStream ds(buffer, SER_NETWORK, INIT_PROTO_VERSION);
     try {

src/test/fuzz/eval_script.cpp

@@ -2,11 +2,17 @@
 // Distributed under the MIT software license, see the accompanying
 // file COPYING or http://www.opensource.org/licenses/mit-license.php.
 
+#include <pubkey.h>
 #include <script/interpreter.h>
 #include <test/fuzz/FuzzedDataProvider.h>
 #include <test/fuzz/fuzz.h>
 
 #include <limits>
+#include <memory>
+
+void initialize() {
+    static const auto verify_handle = std::make_unique<ECCVerifyHandle>();
+}
 
 void test_one_input(const std::vector<uint8_t> &buffer) {
     FuzzedDataProvider fuzzed_data_provider(buffer.data(), buffer.size());

src/test/fuzz/fuzz.cpp

@@ -4,10 +4,9 @@
 
 #include <test/fuzz/fuzz.h>
 
-#include <pubkey.h>
-
-#include <memory>
+#include <cstdint>
 #include <unistd.h>
+#include <vector>
 
 static bool read_stdin(std::vector<uint8_t> &data) {
     uint8_t buffer[1024];
@@ -23,9 +22,7 @@ static bool read_stdin(std::vector<uint8_t> &data) {
 }
 
 // Default initialization: Override using a non-weak initialize().
-__attribute__((weak)) void initialize() {
-    const static auto verify_handle = std::make_unique<ECCVerifyHandle>();
-}
+__attribute__((weak)) void initialize() {}
 
 // This function is used by libFuzzer
 extern "C" int LLVMFuzzerTestOneInput(const uint8_t *data, size_t size) {
@@ -40,13 +37,9 @@ extern "C" int LLVMFuzzerInitialize(int *argc, char ***argv) {
     return 0;
 }
 
-// Disabled under WIN32 due to clash with Cygwin's WinMain.
-#ifndef WIN32
 // Declare main(...) "weak" to allow for libFuzzer linking. libFuzzer provides
 // the main(...) function.
-__attribute__((weak))
-#endif
-int main(int argc, char **argv) {
+__attribute__((weak)) int main(int argc, char **argv) {
     initialize();
 #ifdef __AFL_INIT
     // Enable AFL deferred forkserver mode. Requires compilation using

src/test/fuzz/script_flags.cpp

@@ -2,15 +2,22 @@
 // Distributed under the MIT software license, see the accompanying
 // file COPYING or http://www.opensource.org/licenses/mit-license.php.
 
+#include <pubkey.h>
 #include <script/interpreter.h>
 #include <streams.h>
 #include <version.h>
 
 #include <test/fuzz/fuzz.h>
 
+#include <memory>
+
 /** Flags that are not forbidden by an assert */
 static bool IsValidFlagCombination(uint32_t flags);
 
+void initialize() {
+    static const auto verify_handle = std::make_unique<ECCVerifyHandle>();
+}
+
 void test_one_input(const std::vector<uint8_t> &buffer) {
     CDataStream ds(buffer, SER_NETWORK, INIT_PROTO_VERSION);
     try {