fuzz: [refactor] Use IsValidFlagCombination in signature_checker fuzz target

Can be reviewed with --color-moved=dimmed-zebra

Author: MarcoFalke

src/Makefile.test_util.include

@@ -26,6 +26,7 @@ libtest_util_a_SOURCES = \
   test/util/logging.cpp \
   test/util/mining.cpp \
   test/util/net.cpp \
+  test/util/script.cpp \
   test/util/setup_common.cpp \
   test/util/str.cpp \
   test/util/transaction_utils.cpp \

src/test/fuzz/script_flags.cpp

@@ -5,13 +5,11 @@
 #include <pubkey.h>
 #include <script/interpreter.h>
 #include <streams.h>
+#include <test/util/script.h>
 #include <version.h>
 
 #include <test/fuzz/fuzz.h>
 
-/** Flags that are not forbidden by an assert */
-static bool IsValidFlagCombination(unsigned flags);
-
 void initialize_script_flags()
 {
     static const ECCVerifyHandle verify_handle;
@@ -74,10 +72,3 @@ FUZZ_TARGET_INIT(script_flags, initialize_script_flags)
         return;
     }
 }
-
-static bool IsValidFlagCombination(unsigned flags)
-{
-    if (flags & SCRIPT_VERIFY_CLEANSTACK && ~flags & (SCRIPT_VERIFY_P2SH | SCRIPT_VERIFY_WITNESS)) return false;
-    if (flags & SCRIPT_VERIFY_WITNESS && ~flags & SCRIPT_VERIFY_P2SH) return false;
-    return true;
-}

src/test/fuzz/signature_checker.cpp

@@ -7,6 +7,7 @@
 #include <test/fuzz/FuzzedDataProvider.h>
 #include <test/fuzz/fuzz.h>
 #include <test/fuzz/util.h>
+#include <test/util/script.h>
 
 #include <cstdint>
 #include <limits>
@@ -61,10 +62,7 @@ FUZZ_TARGET_INIT(signature_checker, initialize_signature_checker)
     const auto script_2 = ConsumeScript(fuzzed_data_provider, 65536);
     std::vector<std::vector<unsigned char>> stack;
     (void)EvalScript(stack, script_1, flags, FuzzedSignatureChecker(fuzzed_data_provider), sig_version, nullptr);
-    if ((flags & SCRIPT_VERIFY_CLEANSTACK) != 0 && ((flags & SCRIPT_VERIFY_P2SH) == 0 || (flags & SCRIPT_VERIFY_WITNESS) == 0)) {
-        return;
-    }
-    if ((flags & SCRIPT_VERIFY_WITNESS) != 0 && (flags & SCRIPT_VERIFY_P2SH) == 0) {
+    if (!IsValidFlagCombination(flags)) {
         return;
     }
     (void)VerifyScript(script_1, script_2, nullptr, flags, FuzzedSignatureChecker(fuzzed_data_provider), nullptr);

src/test/util/script.cpp

@@ -0,0 +1,13 @@
+// Copyright (c) 2021 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 <script/interpreter.h>
+#include <test/util/script.h>
+
+bool IsValidFlagCombination(unsigned flags)
+{
+    if (flags & SCRIPT_VERIFY_CLEANSTACK && ~flags & (SCRIPT_VERIFY_P2SH | SCRIPT_VERIFY_WITNESS)) return false;
+    if (flags & SCRIPT_VERIFY_WITNESS && ~flags & SCRIPT_VERIFY_P2SH) return false;
+    return true;
+}

src/test/util/script.h

@@ -18,4 +18,7 @@ static const CScript P2WSH_OP_TRUE{
            return hash;
        }())};
 
+/** Flags that are not forbidden by an assert in script validation */
+bool IsValidFlagCombination(unsigned flags);
+
 #endif // BITCOIN_TEST_UTIL_SCRIPT_H