Precompute sighashes

Original version by Nicolas Dorier. Precomputing version by Pieter Wuille.

1 files changed, 13 insertions, 9 deletions

diff --git a/src/main.cpp b/src/main.cpp
index 6e784c508d..5a9691474f 100644
--- a/src/main.cpp
+++ b/src/main.cpp
@@ -1497,12 +1497,13 @@ 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.
-        if (!CheckInputs(tx, state, view, true, scriptVerifyFlags, true)) {
+        PrecomputedTransactionData txdata(tx);
+        if (!CheckInputs(tx, state, view, true, scriptVerifyFlags, true, 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.
-            if (CheckInputs(tx, state, view, true, scriptVerifyFlags & ~(SCRIPT_VERIFY_WITNESS | SCRIPT_VERIFY_CLEANSTACK), true) &&
-                !CheckInputs(tx, state, view, true, scriptVerifyFlags & ~SCRIPT_VERIFY_CLEANSTACK, true)) {
+            if (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)) {
                 // Only the witness is wrong, so the transaction itself may be fine.
                 state.SetCorruptionPossible();
             }
@@ -1518,7 +1519,7 @@ 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))
+        if (!CheckInputs(tx, state, view, true, MANDATORY_SCRIPT_VERIFY_FLAGS, true, txdata))
         {
             return error("%s: BUG! PLEASE REPORT THIS! ConnectInputs failed against MANDATORY but not STANDARD flags %s, %s",
                 __func__, hash.ToString(), FormatStateMessage(state));
@@ -1915,7 +1916,7 @@ void UpdateCoins(const CTransaction& tx, CCoinsViewCache& inputs, int nHeight)
 bool CScriptCheck::operator()() {
     const CScript &scriptSig = ptxTo->vin[nIn].scriptSig;
     const CScriptWitness *witness = (nIn < ptxTo->wit.vtxinwit.size()) ? &ptxTo->wit.vtxinwit[nIn].scriptWitness : NULL;
-    if (!VerifyScript(scriptSig, scriptPubKey, witness, nFlags, CachingTransactionSignatureChecker(ptxTo, nIn, amount, cacheStore), &error)) {
+    if (!VerifyScript(scriptSig, scriptPubKey, witness, nFlags, CachingTransactionSignatureChecker(ptxTo, nIn, amount, cacheStore, *txdata), &error)) {
         return false;
     }
     return true;
@@ -1974,7 +1975,7 @@ 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, 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)
 {
     if (!tx.IsCoinBase())
     {
@@ -2001,7 +2002,7 @@ bool CheckInputs(const CTransaction& tx, CValidationState &state, const CCoinsVi
                 assert(coins);
 
                 // Verify signature
-                CScriptCheck check(*coins, tx, i, flags, cacheStore);
+                CScriptCheck check(*coins, tx, i, flags, cacheStore, &txdata);
                 if (pvChecks) {
                     pvChecks->push_back(CScriptCheck());
                     check.swap(pvChecks->back());
@@ -2014,7 +2015,7 @@ bool CheckInputs(const CTransaction& tx, CValidationState &state, const CCoinsVi
                         // avoid splitting the network between upgraded and
                         // non-upgraded nodes.
                         CScriptCheck check2(*coins, tx, i,
-                                flags & ~STANDARD_NOT_MANDATORY_VERIFY_FLAGS, cacheStore);
+                                flags & ~STANDARD_NOT_MANDATORY_VERIFY_FLAGS, cacheStore, &txdata);
                         if (check2())
                             return state.Invalid(false, REJECT_NONSTANDARD, strprintf("non-mandatory-script-verify-flag (%s)", ScriptErrorString(check.GetScriptError())));
                     }
@@ -2412,6 +2413,8 @@ bool ConnectBlock(const CBlock& block, CValidationState& state, CBlockIndex* pin
     std::vector<std::pair<uint256, CDiskTxPos> > vPos;
     vPos.reserve(block.vtx.size());
     blockundo.vtxundo.reserve(block.vtx.size() - 1);
+    std::vector<PrecomputedTransactionData> txdata;
+    txdata.reserve(block.vtx.size()); // Required so that pointers to individual PrecomputedTransactionData don't get invalidated
     for (unsigned int i = 0; i < block.vtx.size(); i++)
     {
         const CTransaction &tx = block.vtx[i];
@@ -2458,13 +2461,14 @@ bool ConnectBlock(const CBlock& block, CValidationState& state, CBlockIndex* pin
             return state.DoS(100, error("ConnectBlock(): too many sigops"),
                              REJECT_INVALID, "bad-blk-sigops");
 
+        txdata.emplace_back(tx);
         if (!tx.IsCoinBase())
         {
             nFees += view.GetValueIn(tx)-tx.GetValueOut();
 
             std::vector<CScriptCheck> vChecks;
             bool fCacheResults = fJustCheck; /* Don't cache results if we're actually connecting blocks (still consult the cache, though) */
-            if (!CheckInputs(tx, state, view, fScriptChecks, flags, fCacheResults, nScriptCheckThreads ? &vChecks : NULL))
+            if (!CheckInputs(tx, state, view, fScriptChecks, flags, fCacheResults, txdata[i], nScriptCheckThreads ? &vChecks : NULL))
                 return error("ConnectBlock(): CheckInputs on %s failed with %s",
                     tx.GetHash().ToString(), FormatStateMessage(state));
             control.Add(vChecks);