Only relay Taproot spends if next block has it active

Author: sipa

src/bench/ccoins_caching.cpp

@@ -45,7 +45,7 @@ static void CCoinsCaching(benchmark::Bench& bench)
     // Benchmark.
     const CTransaction tx_1(t1);
     bench.run([&] {
-        bool success = AreInputsStandard(tx_1, coins);
+        bool success = AreInputsStandard(tx_1, coins, false);
         assert(success);
     });
     ECC_Stop();

src/policy/policy.cpp

@@ -155,7 +155,7 @@ bool IsStandardTx(const CTransaction& tx, bool permit_bare_multisig, const CFeeR
  *
  * Note that only the non-witness portion of the transaction is checked here.
  */
-bool AreInputsStandard(const CTransaction& tx, const CCoinsViewCache& mapInputs)
+bool AreInputsStandard(const CTransaction& tx, const CCoinsViewCache& mapInputs, bool taproot_active)
 {
     if (tx.IsCoinBase())
         return true; // Coinbases don't use vin normally
@@ -183,6 +183,9 @@ bool AreInputsStandard(const CTransaction& tx, const CCoinsViewCache& mapInputs)
             if (subscript.GetSigOpCount(true) > MAX_P2SH_SIGOPS) {
                 return false;
             }
+        } else if (whichType == TxoutType::WITNESS_V1_TAPROOT) {
+            // Don't allow Taproot spends unless Taproot is active.
+            if (!taproot_active) return false;
         }
     }
 

src/policy/policy.h

@@ -95,10 +95,11 @@ bool IsStandard(const CScript& scriptPubKey, TxoutType& whichType);
 bool IsStandardTx(const CTransaction& tx, bool permit_bare_multisig, const CFeeRate& dust_relay_fee, std::string& reason);
     /**
      * Check for standard transaction types
-     * @param[in] mapInputs    Map of previous transactions that have outputs we're spending
+     * @param[in] mapInputs       Map of previous transactions that have outputs we're spending
+     * @param[in] taproot_active  Whether or taproot consensus rules are active (used to decide whether spends of them are permitted)
      * @return True if all inputs (scriptSigs) use only standard transaction forms
      */
-bool AreInputsStandard(const CTransaction& tx, const CCoinsViewCache& mapInputs);
+bool AreInputsStandard(const CTransaction& tx, const CCoinsViewCache& mapInputs, bool taproot_active);
     /**
      * Check if the transaction is over standard P2WSH resources limit:
      * 3600bytes witnessScript size, 80bytes per witness stack element, 100 witness stack elements

src/test/fuzz/coins_view.cpp

@@ -229,7 +229,8 @@ void test_one_input(const std::vector<uint8_t>& buffer)
             break;
         }
         case 1: {
-            (void)AreInputsStandard(CTransaction{random_mutable_transaction}, coins_view_cache);
+            (void)AreInputsStandard(CTransaction{random_mutable_transaction}, coins_view_cache, false);
+            (void)AreInputsStandard(CTransaction{random_mutable_transaction}, coins_view_cache, true);
             break;
         }
         case 2: {

src/test/fuzz/transaction.cpp

@@ -95,7 +95,8 @@ void test_one_input(const std::vector<uint8_t>& buffer)
 
     CCoinsView coins_view;
     const CCoinsViewCache coins_view_cache(&coins_view);
-    (void)AreInputsStandard(tx, coins_view_cache);
+    (void)AreInputsStandard(tx, coins_view_cache, false);
+    (void)AreInputsStandard(tx, coins_view_cache, true);
     (void)IsWitnessStandard(tx, coins_view_cache);
 
     UniValue u(UniValue::VOBJ);

src/test/script_p2sh_tests.cpp

@@ -343,7 +343,7 @@ BOOST_AUTO_TEST_CASE(AreInputsStandard)
     txTo.vin[3].scriptSig << OP_11 << OP_11 << std::vector<unsigned char>(oneAndTwo.begin(), oneAndTwo.end());
     txTo.vin[4].scriptSig << std::vector<unsigned char>(fifteenSigops.begin(), fifteenSigops.end());
 
-    BOOST_CHECK(::AreInputsStandard(CTransaction(txTo), coins));
+    BOOST_CHECK(::AreInputsStandard(CTransaction(txTo), coins, false));
     // 22 P2SH sigops for all inputs (1 for vin[0], 6 for vin[3], 15 for vin[4]
     BOOST_CHECK_EQUAL(GetP2SHSigOpCount(CTransaction(txTo), coins), 22U);
 
@@ -356,7 +356,7 @@ BOOST_AUTO_TEST_CASE(AreInputsStandard)
     txToNonStd1.vin[0].prevout.hash = txFrom.GetHash();
     txToNonStd1.vin[0].scriptSig << std::vector<unsigned char>(sixteenSigops.begin(), sixteenSigops.end());
 
-    BOOST_CHECK(!::AreInputsStandard(CTransaction(txToNonStd1), coins));
+    BOOST_CHECK(!::AreInputsStandard(CTransaction(txToNonStd1), coins, false));
     BOOST_CHECK_EQUAL(GetP2SHSigOpCount(CTransaction(txToNonStd1), coins), 16U);
 
     CMutableTransaction txToNonStd2;
@@ -368,7 +368,7 @@ BOOST_AUTO_TEST_CASE(AreInputsStandard)
     txToNonStd2.vin[0].prevout.hash = txFrom.GetHash();
     txToNonStd2.vin[0].scriptSig << std::vector<unsigned char>(twentySigops.begin(), twentySigops.end());
 
-    BOOST_CHECK(!::AreInputsStandard(CTransaction(txToNonStd2), coins));
+    BOOST_CHECK(!::AreInputsStandard(CTransaction(txToNonStd2), coins, false));
     BOOST_CHECK_EQUAL(GetP2SHSigOpCount(CTransaction(txToNonStd2), coins), 20U);
 }
 

src/test/transaction_tests.cpp

@@ -305,7 +305,7 @@ BOOST_AUTO_TEST_CASE(test_Get)
     t1.vout[0].nValue = 90*CENT;
     t1.vout[0].scriptPubKey << OP_1;
 
-    BOOST_CHECK(AreInputsStandard(CTransaction(t1), coins));
+    BOOST_CHECK(AreInputsStandard(CTransaction(t1), coins, false));
 }
 
 static void CreateCreditAndSpend(const FillableSigningProvider& keystore, const CScript& outscript, CTransactionRef& output, CMutableTransaction& input, bool success = true)

src/validation.cpp

@@ -690,7 +690,9 @@ bool MemPoolAccept::PreChecks(ATMPArgs& args, Workspace& ws)
     }
 
     // Check for non-standard pay-to-script-hash in inputs
-    if (fRequireStandard && !AreInputsStandard(tx, m_view)) {
+    const auto& params = args.m_chainparams.GetConsensus();
+    auto taproot_state = VersionBitsState(::ChainActive().Tip(), params, Consensus::DEPLOYMENT_TAPROOT, versionbitscache);
+    if (fRequireStandard && !AreInputsStandard(tx, m_view, taproot_state == ThresholdState::ACTIVE)) {
         return state.Invalid(TxValidationResult::TX_INPUTS_NOT_STANDARD, "bad-txns-nonstandard-inputs");
     }
 

test/functional/feature_taproot.py

@@ -1129,13 +1129,13 @@ def spenders_taproot_inactive():
     ]
     tap = taproot_construct(pub, scripts)
 
-    # Test that keypath spending is valid & standard if compliant, but valid and nonstandard otherwise.
-    add_spender(spenders, "inactive/keypath_valid", key=sec, tap=tap)
+    # Test that keypath spending is valid & non-standard, regardless of validity.
+    add_spender(spenders, "inactive/keypath_valid", key=sec, tap=tap, standard=False)
     add_spender(spenders, "inactive/keypath_invalidsig", key=sec, tap=tap, standard=False, sighash=bitflipper(default_sighash))
     add_spender(spenders, "inactive/keypath_empty", key=sec, tap=tap, standard=False, witness=[])
 
-    # Same for scriptpath spending (but using future features like annex, leaf versions, or OP_SUCCESS is nonstandard).
-    add_spender(spenders, "inactive/scriptpath_valid", key=sec, tap=tap, leaf="pk", inputs=[getter("sign")])
+    # Same for scriptpath spending (and features like annex, leaf versions, or OP_SUCCESS don't change this)
+    add_spender(spenders, "inactive/scriptpath_valid", key=sec, tap=tap, leaf="pk", standard=False, inputs=[getter("sign")])
     add_spender(spenders, "inactive/scriptpath_invalidsig", key=sec, tap=tap, leaf="pk", standard=False, inputs=[getter("sign")], sighash=bitflipper(default_sighash))
     add_spender(spenders, "inactive/scriptpath_invalidcb", key=sec, tap=tap, leaf="pk", standard=False, inputs=[getter("sign")], controlblock=bitflipper(default_controlblock))
     add_spender(spenders, "inactive/scriptpath_valid_unkleaf", key=sec, tap=tap, leaf="future_leaf", standard=False, inputs=[getter("sign")])