Merge #15399: fuzz: Script validation flags

fab15ff70e fuzz: Script validation flags (MarcoFalke)
fabcfa5f0c fuzz: Move deserialize tests to test/fuzz/deserialize.cpp (MarcoFalke)

Pull request description:

Tree-SHA512: 83c0cfeae0771b7ffe14e6b0eaeda06602b91f5bf4aa2f54fd4f7ef2350299679fd2d9339b02e43309bfddccc01d3aef25ce1a3d2c4f9b54f26e16e1249e05db

3 files changed, 110 insertions, 20 deletions

diff --git a/src/Makefile.test.include b/src/Makefile.test.include
index f40a205a73..84bc326cfe 100644
--- a/src/Makefile.test.include
+++ b/src/Makefile.test.include
@@ -20,6 +20,7 @@ FUZZ_TARGETS = \
   test/fuzz/inv_deserialize \
   test/fuzz/messageheader_deserialize \
   test/fuzz/netaddr_deserialize \
+  test/fuzz/script_flags \
   test/fuzz/service_deserialize \
   test/fuzz/transaction_deserialize \
   test/fuzz/txoutcompressor_deserialize \
@@ -172,7 +173,7 @@ test_test_bitcoin_LDADD += $(ZMQ_LIBS)
 endif
 
 if ENABLE_FUZZ
-test_fuzz_block_deserialize_SOURCES = $(FUZZ_SUITE) test/test_bitcoin_fuzzy.cpp
+test_fuzz_block_deserialize_SOURCES = $(FUZZ_SUITE) test/fuzz/deserialize.cpp
 test_fuzz_block_deserialize_CPPFLAGS = $(AM_CPPFLAGS) $(BITCOIN_INCLUDES) -DBLOCK_DESERIALIZE=1
 test_fuzz_block_deserialize_CXXFLAGS = $(AM_CXXFLAGS) $(PIE_FLAGS)
 test_fuzz_block_deserialize_LDFLAGS = $(RELDFLAGS) $(AM_LDFLAGS) $(LIBTOOL_APP_LDFLAGS)
@@ -189,7 +190,7 @@ test_fuzz_block_deserialize_LDADD = \
  $(LIBSECP256K1)
 test_fuzz_block_deserialize_LDADD += $(BOOST_LIBS) $(CRYPTO_LIBS)
 
-test_fuzz_transaction_deserialize_SOURCES = $(FUZZ_SUITE) test/test_bitcoin_fuzzy.cpp
+test_fuzz_transaction_deserialize_SOURCES = $(FUZZ_SUITE) test/fuzz/deserialize.cpp
 test_fuzz_transaction_deserialize_CPPFLAGS = $(AM_CPPFLAGS) $(BITCOIN_INCLUDES) -DTRANSACTION_DESERIALIZE=1
 test_fuzz_transaction_deserialize_CXXFLAGS = $(AM_CXXFLAGS) $(PIE_FLAGS)
 test_fuzz_transaction_deserialize_LDFLAGS = $(RELDFLAGS) $(AM_LDFLAGS) $(LIBTOOL_APP_LDFLAGS)
@@ -206,7 +207,7 @@ test_fuzz_transaction_deserialize_LDADD = \
  $(LIBSECP256K1)
 test_fuzz_transaction_deserialize_LDADD += $(BOOST_LIBS) $(CRYPTO_LIBS)
 
-test_fuzz_blocklocator_deserialize_SOURCES = $(FUZZ_SUITE) test/test_bitcoin_fuzzy.cpp
+test_fuzz_blocklocator_deserialize_SOURCES = $(FUZZ_SUITE) test/fuzz/deserialize.cpp
 test_fuzz_blocklocator_deserialize_CPPFLAGS = $(AM_CPPFLAGS) $(BITCOIN_INCLUDES) -DBLOCKLOCATOR_DESERIALIZE=1
 test_fuzz_blocklocator_deserialize_CXXFLAGS = $(AM_CXXFLAGS) $(PIE_FLAGS)
 test_fuzz_blocklocator_deserialize_LDFLAGS = $(RELDFLAGS) $(AM_LDFLAGS) $(LIBTOOL_APP_LDFLAGS)
@@ -223,7 +224,7 @@ test_fuzz_blocklocator_deserialize_LDADD = \
  $(LIBSECP256K1)
 test_fuzz_blocklocator_deserialize_LDADD += $(BOOST_LIBS) $(CRYPTO_LIBS)
 
-test_fuzz_blockmerkleroot_SOURCES = $(FUZZ_SUITE) test/test_bitcoin_fuzzy.cpp
+test_fuzz_blockmerkleroot_SOURCES = $(FUZZ_SUITE) test/fuzz/deserialize.cpp
 test_fuzz_blockmerkleroot_CPPFLAGS = $(AM_CPPFLAGS) $(BITCOIN_INCLUDES) -DBLOCKMERKLEROOT=1
 test_fuzz_blockmerkleroot_CXXFLAGS = $(AM_CXXFLAGS) $(PIE_FLAGS)
 test_fuzz_blockmerkleroot_LDFLAGS = $(RELDFLAGS) $(AM_LDFLAGS) $(LIBTOOL_APP_LDFLAGS)
@@ -240,7 +241,7 @@ test_fuzz_blockmerkleroot_LDADD = \
  $(LIBSECP256K1)
 test_fuzz_blockmerkleroot_LDADD += $(BOOST_LIBS) $(CRYPTO_LIBS)
 
-test_fuzz_addrman_deserialize_SOURCES = $(FUZZ_SUITE) test/test_bitcoin_fuzzy.cpp
+test_fuzz_addrman_deserialize_SOURCES = $(FUZZ_SUITE) test/fuzz/deserialize.cpp
 test_fuzz_addrman_deserialize_CPPFLAGS = $(AM_CPPFLAGS) $(BITCOIN_INCLUDES) -DADDRMAN_DESERIALIZE=1
 test_fuzz_addrman_deserialize_CXXFLAGS = $(AM_CXXFLAGS) $(PIE_FLAGS)
 test_fuzz_addrman_deserialize_LDFLAGS = $(RELDFLAGS) $(AM_LDFLAGS) $(LIBTOOL_APP_LDFLAGS)
@@ -257,7 +258,7 @@ test_fuzz_addrman_deserialize_LDADD = \
  $(LIBSECP256K1)
 test_fuzz_addrman_deserialize_LDADD += $(BOOST_LIBS) $(CRYPTO_LIBS)
 
-test_fuzz_blockheader_deserialize_SOURCES = $(FUZZ_SUITE) test/test_bitcoin_fuzzy.cpp
+test_fuzz_blockheader_deserialize_SOURCES = $(FUZZ_SUITE) test/fuzz/deserialize.cpp
 test_fuzz_blockheader_deserialize_CPPFLAGS = $(AM_CPPFLAGS) $(BITCOIN_INCLUDES) -DBLOCKHEADER_DESERIALIZE=1
 test_fuzz_blockheader_deserialize_CXXFLAGS = $(AM_CXXFLAGS) $(PIE_FLAGS)
 test_fuzz_blockheader_deserialize_LDFLAGS = $(RELDFLAGS) $(AM_LDFLAGS) $(LIBTOOL_APP_LDFLAGS)
@@ -274,7 +275,7 @@ test_fuzz_blockheader_deserialize_LDADD = \
  $(LIBSECP256K1)
 test_fuzz_blockheader_deserialize_LDADD += $(BOOST_LIBS) $(CRYPTO_LIBS)
 
-test_fuzz_banentry_deserialize_SOURCES = $(FUZZ_SUITE) test/test_bitcoin_fuzzy.cpp
+test_fuzz_banentry_deserialize_SOURCES = $(FUZZ_SUITE) test/fuzz/deserialize.cpp
 test_fuzz_banentry_deserialize_CPPFLAGS = $(AM_CPPFLAGS) $(BITCOIN_INCLUDES) -DBANENTRY_DESERIALIZE=1
 test_fuzz_banentry_deserialize_CXXFLAGS = $(AM_CXXFLAGS) $(PIE_FLAGS)
 test_fuzz_banentry_deserialize_LDFLAGS = $(RELDFLAGS) $(AM_LDFLAGS) $(LIBTOOL_APP_LDFLAGS)
@@ -291,7 +292,7 @@ test_fuzz_banentry_deserialize_LDADD = \
  $(LIBSECP256K1)
 test_fuzz_banentry_deserialize_LDADD += $(BOOST_LIBS) $(CRYPTO_LIBS)
 
-test_fuzz_txundo_deserialize_SOURCES = $(FUZZ_SUITE) test/test_bitcoin_fuzzy.cpp
+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)
 test_fuzz_txundo_deserialize_LDFLAGS = $(RELDFLAGS) $(AM_LDFLAGS) $(LIBTOOL_APP_LDFLAGS)
@@ -308,7 +309,7 @@ test_fuzz_txundo_deserialize_LDADD = \
  $(LIBSECP256K1)
 test_fuzz_txundo_deserialize_LDADD += $(BOOST_LIBS) $(CRYPTO_LIBS)
 
-test_fuzz_blockundo_deserialize_SOURCES = $(FUZZ_SUITE) test/test_bitcoin_fuzzy.cpp
+test_fuzz_blockundo_deserialize_SOURCES = $(FUZZ_SUITE) test/fuzz/deserialize.cpp
 test_fuzz_blockundo_deserialize_CPPFLAGS = $(AM_CPPFLAGS) $(BITCOIN_INCLUDES) -DBLOCKUNDO_DESERIALIZE=1
 test_fuzz_blockundo_deserialize_CXXFLAGS = $(AM_CXXFLAGS) $(PIE_FLAGS)
 test_fuzz_blockundo_deserialize_LDFLAGS = $(RELDFLAGS) $(AM_LDFLAGS) $(LIBTOOL_APP_LDFLAGS)
@@ -325,7 +326,7 @@ test_fuzz_blockundo_deserialize_LDADD = \
  $(LIBSECP256K1)
 test_fuzz_blockundo_deserialize_LDADD += $(BOOST_LIBS) $(CRYPTO_LIBS)
 
-test_fuzz_coins_deserialize_SOURCES = $(FUZZ_SUITE) test/test_bitcoin_fuzzy.cpp
+test_fuzz_coins_deserialize_SOURCES = $(FUZZ_SUITE) test/fuzz/deserialize.cpp
 test_fuzz_coins_deserialize_CPPFLAGS = $(AM_CPPFLAGS) $(BITCOIN_INCLUDES) -DCOINS_DESERIALIZE=1
 test_fuzz_coins_deserialize_CXXFLAGS = $(AM_CXXFLAGS) $(PIE_FLAGS)
 test_fuzz_coins_deserialize_LDFLAGS = $(RELDFLAGS) $(AM_LDFLAGS) $(LIBTOOL_APP_LDFLAGS)
@@ -342,7 +343,7 @@ test_fuzz_coins_deserialize_LDADD = \
  $(LIBSECP256K1)
 test_fuzz_coins_deserialize_LDADD += $(BOOST_LIBS) $(CRYPTO_LIBS)
 
-test_fuzz_netaddr_deserialize_SOURCES = $(FUZZ_SUITE) test/test_bitcoin_fuzzy.cpp
+test_fuzz_netaddr_deserialize_SOURCES = $(FUZZ_SUITE) test/fuzz/deserialize.cpp
 test_fuzz_netaddr_deserialize_CPPFLAGS = $(AM_CPPFLAGS) $(BITCOIN_INCLUDES) -DNETADDR_DESERIALIZE=1
 test_fuzz_netaddr_deserialize_CXXFLAGS = $(AM_CXXFLAGS) $(PIE_FLAGS)
 test_fuzz_netaddr_deserialize_LDFLAGS = $(RELDFLAGS) $(AM_LDFLAGS) $(LIBTOOL_APP_LDFLAGS)
@@ -359,7 +360,24 @@ test_fuzz_netaddr_deserialize_LDADD = \
  $(LIBSECP256K1)
 test_fuzz_netaddr_deserialize_LDADD += $(BOOST_LIBS) $(CRYPTO_LIBS)
 
-test_fuzz_service_deserialize_SOURCES = $(FUZZ_SUITE) test/test_bitcoin_fuzzy.cpp
+test_fuzz_script_flags_SOURCES = $(FUZZ_SUITE) test/fuzz/script_flags.cpp
+test_fuzz_script_flags_CPPFLAGS = $(AM_CPPFLAGS) $(BITCOIN_INCLUDES)
+test_fuzz_script_flags_CXXFLAGS = $(AM_CXXFLAGS) $(PIE_FLAGS)
+test_fuzz_script_flags_LDFLAGS = $(RELDFLAGS) $(AM_LDFLAGS) $(LIBTOOL_APP_LDFLAGS)
+test_fuzz_script_flags_LDADD = \
+ $(LIBUNIVALUE) \
+ $(LIBBITCOIN_SERVER) \
+ $(LIBBITCOIN_COMMON) \
+ $(LIBBITCOIN_UTIL) \
+ $(LIBBITCOIN_CONSENSUS) \
+ $(LIBBITCOIN_CRYPTO) \
+ $(LIBBITCOIN_CRYPTO_SSE41) \
+ $(LIBBITCOIN_CRYPTO_AVX2) \
+ $(LIBBITCOIN_CRYPTO_SHANI) \
+ $(LIBSECP256K1)
+test_fuzz_script_flags_LDADD += $(BOOST_LIBS) $(CRYPTO_LIBS)
+
+test_fuzz_service_deserialize_SOURCES = $(FUZZ_SUITE) test/fuzz/deserialize.cpp
 test_fuzz_service_deserialize_CPPFLAGS = $(AM_CPPFLAGS) $(BITCOIN_INCLUDES) -DSERVICE_DESERIALIZE=1
 test_fuzz_service_deserialize_CXXFLAGS = $(AM_CXXFLAGS) $(PIE_FLAGS)
 test_fuzz_service_deserialize_LDFLAGS = $(RELDFLAGS) $(AM_LDFLAGS) $(LIBTOOL_APP_LDFLAGS)
@@ -376,7 +394,7 @@ test_fuzz_service_deserialize_LDADD = \
  $(LIBSECP256K1)
 test_fuzz_service_deserialize_LDADD += $(BOOST_LIBS) $(CRYPTO_LIBS)
 
-test_fuzz_messageheader_deserialize_SOURCES = $(FUZZ_SUITE) test/test_bitcoin_fuzzy.cpp
+test_fuzz_messageheader_deserialize_SOURCES = $(FUZZ_SUITE) test/fuzz/deserialize.cpp
 test_fuzz_messageheader_deserialize_CPPFLAGS = $(AM_CPPFLAGS) $(BITCOIN_INCLUDES) -DMESSAGEHEADER_DESERIALIZE=1
 test_fuzz_messageheader_deserialize_CXXFLAGS = $(AM_CXXFLAGS) $(PIE_FLAGS)
 test_fuzz_messageheader_deserialize_LDFLAGS = $(RELDFLAGS) $(AM_LDFLAGS) $(LIBTOOL_APP_LDFLAGS)
@@ -393,7 +411,7 @@ test_fuzz_messageheader_deserialize_LDADD = \
  $(LIBSECP256K1)
 test_fuzz_messageheader_deserialize_LDADD += $(BOOST_LIBS) $(CRYPTO_LIBS)
 
-test_fuzz_address_deserialize_SOURCES = $(FUZZ_SUITE) test/test_bitcoin_fuzzy.cpp
+test_fuzz_address_deserialize_SOURCES = $(FUZZ_SUITE) test/fuzz/deserialize.cpp
 test_fuzz_address_deserialize_CPPFLAGS = $(AM_CPPFLAGS) $(BITCOIN_INCLUDES) -DADDRESS_DESERIALIZE=1
 test_fuzz_address_deserialize_CXXFLAGS = $(AM_CXXFLAGS) $(PIE_FLAGS)
 test_fuzz_address_deserialize_LDFLAGS = $(RELDFLAGS) $(AM_LDFLAGS) $(LIBTOOL_APP_LDFLAGS)
@@ -410,7 +428,7 @@ test_fuzz_address_deserialize_LDADD = \
  $(LIBSECP256K1)
 test_fuzz_address_deserialize_LDADD += $(BOOST_LIBS) $(CRYPTO_LIBS)
 
-test_fuzz_inv_deserialize_SOURCES = $(FUZZ_SUITE) test/test_bitcoin_fuzzy.cpp
+test_fuzz_inv_deserialize_SOURCES = $(FUZZ_SUITE) test/fuzz/deserialize.cpp
 test_fuzz_inv_deserialize_CPPFLAGS = $(AM_CPPFLAGS) $(BITCOIN_INCLUDES) -DINV_DESERIALIZE=1
 test_fuzz_inv_deserialize_CXXFLAGS = $(AM_CXXFLAGS) $(PIE_FLAGS)
 test_fuzz_inv_deserialize_LDFLAGS = $(RELDFLAGS) $(AM_LDFLAGS) $(LIBTOOL_APP_LDFLAGS)
@@ -427,7 +445,7 @@ test_fuzz_inv_deserialize_LDADD = \
  $(LIBSECP256K1)
 test_fuzz_inv_deserialize_LDADD += $(BOOST_LIBS) $(CRYPTO_LIBS)
 
-test_fuzz_bloomfilter_deserialize_SOURCES = $(FUZZ_SUITE) test/test_bitcoin_fuzzy.cpp
+test_fuzz_bloomfilter_deserialize_SOURCES = $(FUZZ_SUITE) test/fuzz/deserialize.cpp
 test_fuzz_bloomfilter_deserialize_CPPFLAGS = $(AM_CPPFLAGS) $(BITCOIN_INCLUDES) -DBLOOMFILTER_DESERIALIZE=1
 test_fuzz_bloomfilter_deserialize_CXXFLAGS = $(AM_CXXFLAGS) $(PIE_FLAGS)
 test_fuzz_bloomfilter_deserialize_LDFLAGS = $(RELDFLAGS) $(AM_LDFLAGS) $(LIBTOOL_APP_LDFLAGS)
@@ -444,7 +462,7 @@ test_fuzz_bloomfilter_deserialize_LDADD = \
  $(LIBSECP256K1)
 test_fuzz_bloomfilter_deserialize_LDADD += $(BOOST_LIBS) $(CRYPTO_LIBS)
 
-test_fuzz_diskblockindex_deserialize_SOURCES = $(FUZZ_SUITE) test/test_bitcoin_fuzzy.cpp
+test_fuzz_diskblockindex_deserialize_SOURCES = $(FUZZ_SUITE) test/fuzz/deserialize.cpp
 test_fuzz_diskblockindex_deserialize_CPPFLAGS = $(AM_CPPFLAGS) $(BITCOIN_INCLUDES) -DDISKBLOCKINDEX_DESERIALIZE=1
 test_fuzz_diskblockindex_deserialize_CXXFLAGS = $(AM_CXXFLAGS) $(PIE_FLAGS)
 test_fuzz_diskblockindex_deserialize_LDFLAGS = $(RELDFLAGS) $(AM_LDFLAGS) $(LIBTOOL_APP_LDFLAGS)
@@ -461,7 +479,7 @@ test_fuzz_diskblockindex_deserialize_LDADD = \
  $(LIBSECP256K1)
 test_fuzz_diskblockindex_deserialize_LDADD += $(BOOST_LIBS) $(CRYPTO_LIBS)
 
-test_fuzz_txoutcompressor_deserialize_SOURCES = $(FUZZ_SUITE) test/test_bitcoin_fuzzy.cpp
+test_fuzz_txoutcompressor_deserialize_SOURCES = $(FUZZ_SUITE) test/fuzz/deserialize.cpp
 test_fuzz_txoutcompressor_deserialize_CPPFLAGS = $(AM_CPPFLAGS) $(BITCOIN_INCLUDES) -DTXOUTCOMPRESSOR_DESERIALIZE=1
 test_fuzz_txoutcompressor_deserialize_CXXFLAGS = $(AM_CXXFLAGS) $(PIE_FLAGS)
 test_fuzz_txoutcompressor_deserialize_LDFLAGS = $(RELDFLAGS) $(AM_LDFLAGS) $(LIBTOOL_APP_LDFLAGS)
@@ -478,7 +496,7 @@ test_fuzz_txoutcompressor_deserialize_LDADD = \
  $(LIBSECP256K1)
 test_fuzz_txoutcompressor_deserialize_LDADD += $(BOOST_LIBS) $(CRYPTO_LIBS)
 
-test_fuzz_blocktransactions_deserialize_SOURCES = $(FUZZ_SUITE) test/test_bitcoin_fuzzy.cpp
+test_fuzz_blocktransactions_deserialize_SOURCES = $(FUZZ_SUITE) test/fuzz/deserialize.cpp
 test_fuzz_blocktransactions_deserialize_CPPFLAGS = $(AM_CPPFLAGS) $(BITCOIN_INCLUDES) -DBLOCKTRANSACTIONS_DESERIALIZE=1
 test_fuzz_blocktransactions_deserialize_CXXFLAGS = $(AM_CXXFLAGS) $(PIE_FLAGS)
 test_fuzz_blocktransactions_deserialize_LDFLAGS = $(RELDFLAGS) $(AM_LDFLAGS) $(LIBTOOL_APP_LDFLAGS)
@@ -495,7 +513,7 @@ test_fuzz_blocktransactions_deserialize_LDADD = \
  $(LIBSECP256K1)
 test_fuzz_blocktransactions_deserialize_LDADD += $(BOOST_LIBS) $(CRYPTO_LIBS)
 
-test_fuzz_blocktransactionsrequest_deserialize_SOURCES = $(FUZZ_SUITE) test/test_bitcoin_fuzzy.cpp
+test_fuzz_blocktransactionsrequest_deserialize_SOURCES = $(FUZZ_SUITE) test/fuzz/deserialize.cpp
 test_fuzz_blocktransactionsrequest_deserialize_CPPFLAGS = $(AM_CPPFLAGS) $(BITCOIN_INCLUDES) -DBLOCKTRANSACTIONSREQUEST_DESERIALIZE=1
 test_fuzz_blocktransactionsrequest_deserialize_CXXFLAGS = $(AM_CXXFLAGS) $(PIE_FLAGS)
 test_fuzz_blocktransactionsrequest_deserialize_LDFLAGS = $(RELDFLAGS) $(AM_LDFLAGS) $(LIBTOOL_APP_LDFLAGS)
diff --git a/src/test/test_bitcoin_fuzzy.cpp b/src/test/fuzz/deserialize.cpp
index 859fba0bdc..859fba0bdc 100644
--- a/src/test/test_bitcoin_fuzzy.cpp
+++ b/src/test/fuzz/deserialize.cpp
diff --git a/src/test/fuzz/script_flags.cpp b/src/test/fuzz/script_flags.cpp
new file mode 100644
index 0000000000..2c0bfa360c
--- /dev/null
+++ b/src/test/fuzz/script_flags.cpp
@@ -0,0 +1,72 @@
+// Copyright (c) 2009-2019 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 <script/interpreter.h>
+#include <script/script.h>
+#include <streams.h>
+#include <version.h>
+
+#include <test/fuzz/fuzz.h>
+
+/** Flags that are not forbidden by an assert */
+static bool IsValidFlagCombination(unsigned flags);
+
+void test_one_input(std::vector<uint8_t> buffer)
+{
+    CDataStream ds(buffer, SER_NETWORK, INIT_PROTO_VERSION);
+    try {
+        int nVersion;
+        ds >> nVersion;
+        ds.SetVersion(nVersion);
+    } catch (const std::ios_base::failure&) {
+        return;
+    }
+
+    try {
+        const CTransaction tx(deserialize, ds);
+        const PrecomputedTransactionData txdata(tx);
+
+        unsigned int verify_flags;
+        ds >> verify_flags;
+
+        if (!IsValidFlagCombination(verify_flags)) return;
+
+        unsigned int fuzzed_flags;
+        ds >> fuzzed_flags;
+
+        for (unsigned i = 0; i < tx.vin.size(); ++i) {
+            CTxOut prevout;
+            ds >> prevout;
+
+            const TransactionSignatureChecker checker{&tx, i, prevout.nValue, txdata};
+
+            ScriptError serror;
+            const bool ret = VerifyScript(tx.vin.at(i).scriptSig, prevout.scriptPubKey, &tx.vin.at(i).scriptWitness, verify_flags, checker, &serror);
+            assert(ret == (serror == SCRIPT_ERR_OK));
+
+            // Verify that removing flags from a passing test or adding flags to a failing test does not change the result
+            if (ret) {
+                verify_flags &= ~fuzzed_flags;
+            } else {
+                verify_flags |= fuzzed_flags;
+            }
+            if (!IsValidFlagCombination(verify_flags)) return;
+
+            ScriptError serror_fuzzed;
+            const bool ret_fuzzed = VerifyScript(tx.vin.at(i).scriptSig, prevout.scriptPubKey, &tx.vin.at(i).scriptWitness, verify_flags, checker, &serror_fuzzed);
+            assert(ret_fuzzed == (serror_fuzzed == SCRIPT_ERR_OK));
+
+            assert(ret_fuzzed == ret);
+        }
+    } catch (const std::ios_base::failure&) {
+        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;
+}