Merge #10699: Make all script validation flags backward compatible

01013f5 Simplify tx validation tests (Pieter Wuille)
2dd6f80 Add a test that all flags are softforks (Pieter Wuille)
2851b77 Make all script verification flags softforks (Pieter Wuille)

Pull request description:

  This change makes `SCRIPT_VERIFY_UPGRADABLE_NOPS` not apply to `OP_CHECKLOCKTIMEVERIFY` and `OP_CHECKSEQUENCEVERIFY`. This is a no-op as `UPGRADABLE_NOPS` is only set for mempool transactions, and those always have `SCRIPT_VERIFY_CHECKLOCKTIMEVERIFY` and `SCRIPT_VERIFY_CHECKSEQUENCEVERIFY` set as well. The advantage is that setting more flags now always results in a reduction in acceptable scripts (=softfork).

  This results in a nice and testable property for validation, for which a new test is added.

  This also means that the introduction of a new definition for a NOP or witness version will likely need the following procedure (example OP_NOP8 here)
  * Remove OP_NOP8 from being affected by `SCRIPT_VERIFY_DISCOURAGE_UPGRADABLE_NOPS`.
  * Add a `SCRIPT_VERIFY_DISCOURAGE_NOP8`, which only applies to `OP_NOP8`.
  * Add a `SCRIPT_VERIFY_NOP8` which implements the new consensus logic.
  * Before activation, add `SCRIPT_VERIFY_DISCOURAGE_NOP8` to the mempool flags.
  * After activation, add `SCRIPT_VERIFY_NOP8` to both the mempool and consensus flags.

Tree-SHA512: d3b4538986ecf646aac9dba13a8d89318baf9e308e258547ca3b99e7c0509747f323edac6b1fea4e87e7d3c01b71193794b41679ae4f86f6e11ed6be3fd62c72

1 files changed, 11 insertions, 0 deletions

diff --git a/src/test/script_tests.cpp b/src/test/script_tests.cpp
index 57b3e501af..f96d867bc6 100644
--- a/src/test/script_tests.cpp
+++ b/src/test/script_tests.cpp
@@ -166,6 +166,17 @@ void DoTest(const CScript& scriptPubKey, const CScript& scriptSig, const CScript
     CMutableTransaction tx2 = tx;
     BOOST_CHECK_MESSAGE(VerifyScript(scriptSig, scriptPubKey, &scriptWitness, flags, MutableTransactionSignatureChecker(&tx, 0, txCredit.vout[0].nValue), &err) == expect, message);
     BOOST_CHECK_MESSAGE(err == scriptError, std::string(FormatScriptError(err)) + " where " + std::string(FormatScriptError((ScriptError_t)scriptError)) + " expected: " + message);
+
+    // Verify that removing flags from a passing test or adding flags to a failing test does not change the result.
+    for (int i = 0; i < 16; ++i) {
+        int extra_flags = InsecureRandBits(16);
+        int combined_flags = expect ? (flags & ~extra_flags) : (flags | extra_flags);
+        // Weed out some invalid flag combinations.
+        if (combined_flags & SCRIPT_VERIFY_CLEANSTACK && ~combined_flags & (SCRIPT_VERIFY_P2SH | SCRIPT_VERIFY_WITNESS)) continue;
+        if (combined_flags & SCRIPT_VERIFY_WITNESS && ~combined_flags & SCRIPT_VERIFY_P2SH) continue;
+        BOOST_CHECK_MESSAGE(VerifyScript(scriptSig, scriptPubKey, &scriptWitness, combined_flags, MutableTransactionSignatureChecker(&tx, 0, txCredit.vout[0].nValue), &err) == expect, message + strprintf(" (with flags %x)", combined_flags));
+    }
+
 #if defined(HAVE_CONSENSUS_LIB)
     CDataStream stream(SER_NETWORK, PROTOCOL_VERSION);
     stream << tx2;