From 0da49b5926b678b2ec35fabe37034f3d2e8385f4 Mon Sep 17 00:00:00 2001
From: Johnson Lau <jl2012@xbt.hk>
Date: Wed, 18 Jan 2017 16:12:26 +0800
Subject: [PATCH] Skip precompute sighash for transactions without witness

---
 src/script/interpreter.cpp | 17 +++++++++++------
 src/script/interpreter.h   |  1 +
 2 files changed, 12 insertions(+), 6 deletions(-)

diff --git a/src/script/interpreter.cpp b/src/script/interpreter.cpp
index f9b7835882..7d5d2092f8 100644
--- a/src/script/interpreter.cpp
+++ b/src/script/interpreter.cpp
@@ -1170,9 +1170,13 @@ uint256 GetOutputsHash(const CTransaction& txTo) {
 
 PrecomputedTransactionData::PrecomputedTransactionData(const CTransaction& txTo)
 {
-    hashPrevouts = GetPrevoutHash(txTo);
-    hashSequence = GetSequenceHash(txTo);
-    hashOutputs = GetOutputsHash(txTo);
+    // Cache is calculated only for transactions with witness
+    if (txTo.HasWitness()) {
+        hashPrevouts = GetPrevoutHash(txTo);
+        hashSequence = GetSequenceHash(txTo);
+        hashOutputs = GetOutputsHash(txTo);
+        ready = true;
+    }
 }
 
 uint256 SignatureHash(const CScript& scriptCode, const CTransaction& txTo, unsigned int nIn, int nHashType, const CAmount& amount, SigVersion sigversion, const PrecomputedTransactionData* cache)
@@ -1181,18 +1185,19 @@ uint256 SignatureHash(const CScript& scriptCode, const CTransaction& txTo, unsig
         uint256 hashPrevouts;
         uint256 hashSequence;
         uint256 hashOutputs;
+        const bool cacheready = cache && cache->ready;
 
         if (!(nHashType & SIGHASH_ANYONECANPAY)) {
-            hashPrevouts = cache ? cache->hashPrevouts : GetPrevoutHash(txTo);
+            hashPrevouts = cacheready ? cache->hashPrevouts : GetPrevoutHash(txTo);
         }
 
         if (!(nHashType & SIGHASH_ANYONECANPAY) && (nHashType & 0x1f) != SIGHASH_SINGLE && (nHashType & 0x1f) != SIGHASH_NONE) {
-            hashSequence = cache ? cache->hashSequence : GetSequenceHash(txTo);
+            hashSequence = cacheready ? cache->hashSequence : GetSequenceHash(txTo);
         }
 
 
         if ((nHashType & 0x1f) != SIGHASH_SINGLE && (nHashType & 0x1f) != SIGHASH_NONE) {
-            hashOutputs = cache ? cache->hashOutputs : GetOutputsHash(txTo);
+            hashOutputs = cacheready ? cache->hashOutputs : GetOutputsHash(txTo);
         } else if ((nHashType & 0x1f) == SIGHASH_SINGLE && nIn < txTo.vout.size()) {
             CHashWriter ss(SER_GETHASH, 0);
             ss << txTo.vout[nIn];
diff --git a/src/script/interpreter.h b/src/script/interpreter.h
index 79894c5300..c6385cb519 100644
--- a/src/script/interpreter.h
+++ b/src/script/interpreter.h
@@ -113,6 +113,7 @@ bool CheckSignatureEncoding(const std::vector<unsigned char> &vchSig, unsigned i
 struct PrecomputedTransactionData
 {
     uint256 hashPrevouts, hashSequence, hashOutputs;
+    bool ready = false;
 
     PrecomputedTransactionData(const CTransaction& tx);
 };