Enforce mandatory softfork flags for segwit block/tx

src/main.cpp

@@ -1122,6 +1122,8 @@ bool AcceptToMemoryPoolWorker(CTxMemPool& pool, CValidationState& state, const C
                               std::vector<uint256>& vHashTxnToUncache)
 {
     const uint256 hash = tx.GetHash();
+    const bool fHaveWitness = !tx.wit.IsNull();
+    unsigned int mandatoryScriptVerifyFlags = fHaveWitness ? MANDATORY_SEGWIT_SCRIPT_VERIFY_FLAGS : MANDATORY_SCRIPT_VERIFY_FLAGS;
     AssertLockHeld(cs_main);
     if (pfMissingInputs)
         *pfMissingInputs = false;
@@ -1497,12 +1499,12 @@ bool AcceptToMemoryPoolWorker(CTxMemPool& pool, CValidationState& state, const C
         // Check against previous transactions
         // This is done last to help prevent CPU exhaustion denial-of-service attacks.
         PrecomputedTransactionData txdata(tx);
-        if (!CheckInputs(tx, state, view, true, scriptVerifyFlags, true, txdata)) {
+        if (!CheckInputs(tx, state, view, true, scriptVerifyFlags, true, txdata, NULL, fHaveWitness)) {
             // SCRIPT_VERIFY_CLEANSTACK requires SCRIPT_VERIFY_WITNESS, so we
             // need to turn both off, and compare against just turning off CLEANSTACK
             // to see if the failure is specifically due to witness validation.
-            if (tx.wit.IsNull() && CheckInputs(tx, state, view, true, scriptVerifyFlags & ~(SCRIPT_VERIFY_WITNESS | SCRIPT_VERIFY_CLEANSTACK), true, txdata) &&
-                !CheckInputs(tx, state, view, true, scriptVerifyFlags & ~SCRIPT_VERIFY_CLEANSTACK, true, txdata)) {
+            if (tx.wit.IsNull() && CheckInputs(tx, state, view, true, scriptVerifyFlags & ~(SCRIPT_VERIFY_WITNESS | SCRIPT_VERIFY_CLEANSTACK), true, txdata, NULL, fHaveWitness) &&
+                !CheckInputs(tx, state, view, true, scriptVerifyFlags & ~SCRIPT_VERIFY_CLEANSTACK, true, txdata, NULL, fHaveWitness)) {
                 // Only the witness is missing, so the transaction itself may be fine.
                 state.SetCorruptionPossible();
             }
@@ -1518,7 +1520,7 @@ bool AcceptToMemoryPoolWorker(CTxMemPool& pool, CValidationState& state, const C
         // There is a similar check in CreateNewBlock() to prevent creating
         // invalid blocks, however allowing such transactions into the mempool
         // can be exploited as a DoS attack.
-        if (!CheckInputs(tx, state, view, true, MANDATORY_SCRIPT_VERIFY_FLAGS, true, txdata))
+        if (!CheckInputs(tx, state, view, true, mandatoryScriptVerifyFlags, true, txdata, NULL, fHaveWitness))
         {
             return error("%s: BUG! PLEASE REPORT THIS! ConnectInputs failed against MANDATORY but not STANDARD flags %s, %s",
                 __func__, hash.ToString(), FormatStateMessage(state));
@@ -1974,7 +1976,7 @@ bool CheckTxInputs(const CTransaction& tx, CValidationState& state, const CCoins
 }
 }// namespace Consensus
 
-bool CheckInputs(const CTransaction& tx, CValidationState &state, const CCoinsViewCache &inputs, bool fScriptChecks, unsigned int flags, bool cacheStore, PrecomputedTransactionData& txdata, std::vector<CScriptCheck> *pvChecks)
+bool CheckInputs(const CTransaction& tx, CValidationState &state, const CCoinsViewCache &inputs, bool fScriptChecks, unsigned int flags, bool cacheStore, PrecomputedTransactionData& txdata, std::vector<CScriptCheck> *pvChecks, const bool fHaveWitness)
 {
     if (!tx.IsCoinBase())
     {
@@ -2006,15 +2008,16 @@ bool CheckInputs(const CTransaction& tx, CValidationState &state, const CCoinsVi
                     pvChecks->push_back(CScriptCheck());
                     check.swap(pvChecks->back());
                 } else if (!check()) {
-                    if (flags & STANDARD_NOT_MANDATORY_VERIFY_FLAGS) {
+                    unsigned int notMandatoryScriptVerifyFlags = fHaveWitness ? STANDARD_NOT_MANDATORY_SEGWIT_VERIFY_FLAGS : STANDARD_NOT_MANDATORY_VERIFY_FLAGS;
+                    if (flags & notMandatoryScriptVerifyFlags) {
                         // Check whether the failure was caused by a
                         // non-mandatory script verification check, such as
                         // non-standard DER encodings or non-null dummy
                         // arguments; if so, don't trigger DoS protection to
                         // avoid splitting the network between upgraded and
                         // non-upgraded nodes.
                         CScriptCheck check2(*coins, tx, i,
-                                flags & ~STANDARD_NOT_MANDATORY_VERIFY_FLAGS, cacheStore, &txdata);
+                                flags & ~notMandatoryScriptVerifyFlags, cacheStore, &txdata);
                         if (check2())
                             return state.Invalid(false, REJECT_NONSTANDARD, strprintf("non-mandatory-script-verify-flag (%s)", ScriptErrorString(check.GetScriptError())));
                     }

src/main.h

@@ -348,7 +348,7 @@ int64_t GetTransactionSigOpCost(const CTransaction& tx, const CCoinsViewCache& i
  * instead of being performed inline.
  */
 bool CheckInputs(const CTransaction& tx, CValidationState &state, const CCoinsViewCache &view, bool fScriptChecks,
-                 unsigned int flags, bool cacheStore, PrecomputedTransactionData& txdata, std::vector<CScriptCheck> *pvChecks = NULL);
+                 unsigned int flags, bool cacheStore, PrecomputedTransactionData& txdata, std::vector<CScriptCheck> *pvChecks = NULL, const bool fHaveWitness = false);
 
 /** Apply the effects of this transaction on the UTXO set represented by view */
 void UpdateCoins(const CTransaction& tx, CCoinsViewCache& inputs, int nHeight);

src/policy/policy.h

@@ -51,6 +51,8 @@ static const unsigned int STANDARD_SCRIPT_VERIFY_FLAGS = MANDATORY_SCRIPT_VERIFY
 /** For convenience, standard but not mandatory verify flags. */
 static const unsigned int STANDARD_NOT_MANDATORY_VERIFY_FLAGS = STANDARD_SCRIPT_VERIFY_FLAGS & ~MANDATORY_SCRIPT_VERIFY_FLAGS;
 
+static const unsigned int STANDARD_NOT_MANDATORY_SEGWIT_VERIFY_FLAGS = STANDARD_SCRIPT_VERIFY_FLAGS & ~MANDATORY_SEGWIT_SCRIPT_VERIFY_FLAGS;
+
 /** Used as the flags parameter to sequence and nLocktime checks in non-consensus code. */
 static const unsigned int STANDARD_LOCKTIME_VERIFY_FLAGS = LOCKTIME_VERIFY_SEQUENCE |
                                                            LOCKTIME_MEDIAN_TIME_PAST;

src/script/standard.h

@@ -42,6 +42,16 @@ extern unsigned nMaxDatacarrierBytes;
  */
 static const unsigned int MANDATORY_SCRIPT_VERIFY_FLAGS = SCRIPT_VERIFY_P2SH;
 
+/**
+ * If a transaction contains any witness data, it must comply with
+ * all known soft-fork rules at the time of segwit activation.
+ */
+static const unsigned int MANDATORY_SEGWIT_SCRIPT_VERIFY_FLAGS = MANDATORY_SCRIPT_VERIFY_FLAGS |
+                                                                 SCRIPT_VERIFY_DERSIG |
+                                                                 SCRIPT_VERIFY_CHECKLOCKTIMEVERIFY |
+                                                                 SCRIPT_VERIFY_CHECKSEQUENCEVERIFY |
+                                                                 SCRIPT_VERIFY_WITNESS;
+
 enum txnouttype
 {
     TX_NONSTANDARD,