1 files changed, 23 insertions, 21 deletions

diff --git a/src/validation.cpp b/src/validation.cpp
index 5db0ec5d96..755f8d43f9 100644
--- a/src/validation.cpp
+++ b/src/validation.cpp
@@ -1,5 +1,5 @@
 // Copyright (c) 2009-2010 Satoshi Nakamoto
-// Copyright (c) 2009-2018 The Bitcoin Core developers
+// 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.
 
@@ -180,7 +180,7 @@ std::unique_ptr<CBlockTreeDB> pblocktree;
 // See definition for documentation
 static void FindFilesToPruneManual(std::set<int>& setFilesToPrune, int nManualPruneHeight);
 static void FindFilesToPrune(std::set<int>& setFilesToPrune, uint64_t nPruneAfterHeight);
-bool CheckInputs(const CTransaction& tx, TxValidationState &state, const CCoinsViewCache &inputs, unsigned int flags, bool cacheSigStore, bool cacheFullScriptStore, PrecomputedTransactionData& txdata, std::vector<CScriptCheck> *pvChecks = nullptr);
+bool CheckInputScripts(const CTransaction& tx, TxValidationState &state, const CCoinsViewCache &inputs, unsigned int flags, bool cacheSigStore, bool cacheFullScriptStore, PrecomputedTransactionData& txdata, std::vector<CScriptCheck> *pvChecks = nullptr);
 static FILE* OpenUndoFile(const FlatFilePos &pos, bool fReadOnly = false);
 static FlatFileSeq BlockFileSeq();
 static FlatFileSeq UndoFileSeq();
@@ -396,19 +396,19 @@ static bool CheckInputsFromMempoolAndCache(const CTransaction& tx, TxValidationS
 
     // pool.cs should be locked already, but go ahead and re-take the lock here
     // to enforce that mempool doesn't change between when we check the view
-    // and when we actually call through to CheckInputs
+    // and when we actually call through to CheckInputScripts
     LOCK(pool.cs);
 
     assert(!tx.IsCoinBase());
     for (const CTxIn& txin : tx.vin) {
         const Coin& coin = view.AccessCoin(txin.prevout);
 
-        // At this point we haven't actually checked if the coins are all
-        // available (or shouldn't assume we have, since CheckInputs does).
-        // So we just return failure if the inputs are not available here,
-        // and then only have to check equivalence for available inputs.
+        // AcceptToMemoryPoolWorker has already checked that the coins are
+        // available, so this shouldn't fail. If the inputs are not available
+        // here then return false.
         if (coin.IsSpent()) return false;
 
+        // Check equivalence for available inputs.
         const CTransactionRef& txFrom = pool.get(txin.prevout.hash);
         if (txFrom) {
             assert(txFrom->GetHash() == txin.prevout.hash);
@@ -421,8 +421,8 @@ static bool CheckInputsFromMempoolAndCache(const CTransaction& tx, TxValidationS
         }
     }
 
-    // Call CheckInputs() to cache signature and script validity against current tip consensus rules.
-    return CheckInputs(tx, state, view, flags, /* cacheSigStore = */ true, /* cacheFullSciptStore = */ true, txdata);
+    // Call CheckInputScripts() to cache signature and script validity against current tip consensus rules.
+    return CheckInputScripts(tx, state, view, flags, /* cacheSigStore = */ true, /* cacheFullSciptStore = */ true, txdata);
 }
 
 namespace {
@@ -906,20 +906,20 @@ bool MemPoolAccept::PolicyScriptChecks(ATMPArgs& args, Workspace& ws, Precompute
 
     constexpr unsigned int scriptVerifyFlags = STANDARD_SCRIPT_VERIFY_FLAGS;
 
-    // Check against previous transactions
+    // Check input scripts and signatures.
     // This is done last to help prevent CPU exhaustion denial-of-service attacks.
-    if (!CheckInputs(tx, state, m_view, scriptVerifyFlags, true, false, txdata)) {
+    if (!CheckInputScripts(tx, state, m_view, scriptVerifyFlags, true, false, txdata)) {
         // 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.
-        TxValidationState state_dummy; // Want reported failures to be from first CheckInputs
-        if (!tx.HasWitness() && CheckInputs(tx, state_dummy, m_view, scriptVerifyFlags & ~(SCRIPT_VERIFY_WITNESS | SCRIPT_VERIFY_CLEANSTACK), true, false, txdata) &&
-                !CheckInputs(tx, state_dummy, m_view, scriptVerifyFlags & ~SCRIPT_VERIFY_CLEANSTACK, true, false, txdata)) {
+        TxValidationState state_dummy; // Want reported failures to be from first CheckInputScripts
+        if (!tx.HasWitness() && CheckInputScripts(tx, state_dummy, m_view, scriptVerifyFlags & ~(SCRIPT_VERIFY_WITNESS | SCRIPT_VERIFY_CLEANSTACK), true, false, txdata) &&
+                !CheckInputScripts(tx, state_dummy, m_view, scriptVerifyFlags & ~SCRIPT_VERIFY_CLEANSTACK, true, false, txdata)) {
             // Only the witness is missing, so the transaction itself may be fine.
             state.Invalid(TxValidationResult::TX_WITNESS_MUTATED,
                     state.GetRejectReason(), state.GetDebugMessage());
         }
-        return false; // state filled in by CheckInputs
+        return false; // state filled in by CheckInputScripts
     }
 
     return true;
@@ -950,7 +950,7 @@ bool MemPoolAccept::ConsensusScriptChecks(ATMPArgs& args, Workspace& ws, Precomp
     // transactions into the mempool can be exploited as a DoS attack.
     unsigned int currentBlockScriptVerifyFlags = GetBlockScriptFlags(::ChainActive().Tip(), chainparams.GetConsensus());
     if (!CheckInputsFromMempoolAndCache(tx, state, m_view, m_pool, currentBlockScriptVerifyFlags, txdata)) {
-        return error("%s: BUG! PLEASE REPORT THIS! CheckInputs failed against latest-block but not STANDARD flags %s, %s",
+        return error("%s: BUG! PLEASE REPORT THIS! CheckInputScripts failed against latest-block but not STANDARD flags %s, %s",
                 __func__, hash.ToString(), FormatStateMessage(state));
     }
 
@@ -1466,8 +1466,10 @@ void InitScriptExecutionCache() {
 }
 
 /**
- * Check whether all inputs of this transaction are valid (no double spends, scripts & sigs, amounts)
- * This does not modify the UTXO set.
+ * Check whether all of this transaction's input scripts succeed.
+ *
+ * This involves ECDSA signature checks so can be computationally intensive. This function should
+ * only be called after the cheap sanity checks in CheckTxInputs passed.
  *
  * If pvChecks is not nullptr, script checks are pushed onto it instead of being performed inline. Any
  * script checks which are not necessary (eg due to script execution cache hits) are, obviously,
@@ -1482,7 +1484,7 @@ void InitScriptExecutionCache() {
  *
  * Non-static (and re-declared) in src/test/txvalidationcache_tests.cpp
  */
-bool CheckInputs(const CTransaction& tx, TxValidationState &state, const CCoinsViewCache &inputs, unsigned int flags, bool cacheSigStore, bool cacheFullScriptStore, PrecomputedTransactionData& txdata, std::vector<CScriptCheck> *pvChecks) EXCLUSIVE_LOCKS_REQUIRED(cs_main)
+bool CheckInputScripts(const CTransaction& tx, TxValidationState &state, const CCoinsViewCache &inputs, unsigned int flags, bool cacheSigStore, bool cacheFullScriptStore, PrecomputedTransactionData& txdata, std::vector<CScriptCheck> *pvChecks) EXCLUSIVE_LOCKS_REQUIRED(cs_main)
 {
     if (tx.IsCoinBase()) return true;
 
@@ -2129,11 +2131,11 @@ bool CChainState::ConnectBlock(const CBlock& block, BlockValidationState& state,
             std::vector<CScriptCheck> vChecks;
             bool fCacheResults = fJustCheck; /* Don't cache results if we're actually connecting blocks (still consult the cache, though) */
             TxValidationState tx_state;
-            if (fScriptChecks && !CheckInputs(tx, tx_state, view, flags, fCacheResults, fCacheResults, txdata[i], g_parallel_script_checks ? &vChecks : nullptr)) {
+            if (fScriptChecks && !CheckInputScripts(tx, tx_state, view, flags, fCacheResults, fCacheResults, txdata[i], g_parallel_script_checks ? &vChecks : nullptr)) {
                 // Any transaction validation failure in ConnectBlock is a block consensus failure
                 state.Invalid(BlockValidationResult::BLOCK_CONSENSUS,
                               tx_state.GetRejectReason(), tx_state.GetDebugMessage());
-                return error("ConnectBlock(): CheckInputs on %s failed with %s",
+                return error("ConnectBlock(): CheckInputScripts on %s failed with %s",
                     tx.GetHash().ToString(), FormatStateMessage(state));
             }
             control.Add(vChecks);