Fix off-by-one error w/ nLockTime in the wallet

Previously due to an off-by-one error the wallet ignored
nLockTime-by-height transactions that would be valid in the next block
even though they are accepted into the mempool. The transactions
wouldn't show up until confirmed, nor would they be included in the
unconfirmed balance. Similar to the mempool behavior fix in 665bdd3,
the wallet code was calling IsFinalTx() directly without taking into
account the fact that doing so tells you if the transaction could have
been mined in the *current* block, rather than the next block.

To fix this we strip IsFinalTx() of non-consensus-critical
functionality, removing the default arguments, and add CheckFinalTx() to
check if a transaction will be final in the next block.

Github-Pull: zcash#6183
Rebased-From: 28bf062

src/main.cpp

@@ -671,14 +671,8 @@ bool IsStandardTx(const CTransaction& tx, string& reason)
 
 bool IsFinalTx(const CTransaction &tx, int nBlockHeight, int64_t nBlockTime)
 {
-    AssertLockHeld(cs_main);
-    // Time based nLockTime implemented in 0.1.6
     if (tx.nLockTime == 0)
         return true;
-    if (nBlockHeight == 0)
-        nBlockHeight = chainActive.Height();
-    if (nBlockTime == 0)
-        nBlockTime = GetAdjustedTime();
     if ((int64_t)tx.nLockTime < ((int64_t)tx.nLockTime < LOCKTIME_THRESHOLD ? (int64_t)nBlockHeight : nBlockTime))
         return true;
     BOOST_FOREACH(const CTxIn& txin, tx.vin)
@@ -687,6 +681,12 @@ bool IsFinalTx(const CTransaction &tx, int nBlockHeight, int64_t nBlockTime)
     return true;
 }
 
+bool CheckFinalTx(const CTransaction &tx)
+{
+    AssertLockHeld(cs_main);
+    return IsFinalTx(tx, chainActive.Height() + 1, GetAdjustedTime());
+}
+
 /**
  * Check transaction inputs to mitigate two
  * potential denial-of-service attacks:
@@ -903,21 +903,8 @@ bool AcceptToMemoryPool(CTxMemPool& pool, CValidationState &state, const CTransa
     // Only accept nLockTime-using transactions that can be mined in the next
     // block; we don't want our mempool filled up with transactions that can't
     // be mined yet.
-    //
-    // However, IsFinalTx() is confusing... Without arguments, it uses
-    // chainActive.Height() to evaluate nLockTime; when a block is accepted,
-    // chainActive.Height() is set to the value of nHeight in the block.
-    // However, when IsFinalTx() is called within CBlock::AcceptBlock(), the
-    // height of the block *being* evaluated is what is used. Thus if we want
-    // to know if a transaction can be part of the *next* block, we need to
-    // call IsFinalTx() with one more than chainActive.Height().
-    //
-    // Timestamps on the other hand don't get any special treatment, because we
-    // can't know what timestamp the next block will have, and there aren't
-    // timestamp applications where it matters.
-    if (!IsFinalTx(tx, chainActive.Height() + 1))
-        return state.DoS(0,
-                         error("AcceptToMemoryPool: non-final"),
+    if (!CheckFinalTx(tx))
+        return state.DoS(0, error("AcceptToMemoryPool: non-final"),
                          REJECT_NONSTANDARD, "non-final");
 
     // is it already in the memory pool?

src/main.h

@@ -324,7 +324,18 @@ bool CheckTransaction(const CTransaction& tx, CValidationState& state);
  */
 bool IsStandardTx(const CTransaction& tx, std::string& reason);
 
-bool IsFinalTx(const CTransaction &tx, int nBlockHeight = 0, int64_t nBlockTime = 0);
+/**
+ * Check if transaction is final and can be included in a block with the
+ * specified height and time. Consensus critical.
+ */
+bool IsFinalTx(const CTransaction &tx, int nBlockHeight, int64_t nBlockTime);
+
+/**
+ * Check if transaction will be final in the next block to be created.
+ *
+ * Calls IsFinalTx() with current block height and appropriate block time.
+ */
+bool CheckFinalTx(const CTransaction &tx);
 
 /** 
  * Closure representing one script verification

src/miner.cpp

@@ -138,6 +138,7 @@ CBlockTemplate* CreateNewBlock(const CScript& scriptPubKeyIn)
         LOCK2(cs_main, mempool.cs);
         CBlockIndex* pindexPrev = chainActive.Tip();
         const int nHeight = pindexPrev->nHeight + 1;
+        pblock->nTime = GetAdjustedTime();
         CCoinsViewCache view(pcoinsTip);
 
         // Priority order to process transactions
@@ -152,7 +153,7 @@ CBlockTemplate* CreateNewBlock(const CScript& scriptPubKeyIn)
              mi != mempool.mapTx.end(); ++mi)
         {
             const CTransaction& tx = mi->second.GetTx();
-            if (tx.IsCoinBase() || !IsFinalTx(tx, nHeight))
+            if (tx.IsCoinBase() || !IsFinalTx(tx, nHeight, pblock->nTime))
                 continue;
 
             COrphan* porphan = NULL;

src/qt/transactiondesc.cpp

@@ -26,7 +26,7 @@ using namespace std;
 QString TransactionDesc::FormatTxStatus(const CWalletTx& wtx)
 {
     AssertLockHeld(cs_main);
-    if (!IsFinalTx(wtx, chainActive.Height() + 1))
+    if (!CheckFinalTx(wtx))
     {
         if (wtx.nLockTime < LOCKTIME_THRESHOLD)
             return tr("Open for %n more block(s)", "", wtx.nLockTime - chainActive.Height());

src/qt/transactionrecord.cpp

@@ -188,7 +188,7 @@ void TransactionRecord::updateStatus(const CWalletTx &wtx)
     status.depth = wtx.GetDepthInMainChain();
     status.cur_num_blocks = chainActive.Height();
 
-    if (!IsFinalTx(wtx, chainActive.Height() + 1))
+    if (!CheckFinalTx(wtx))
     {
         if (wtx.nLockTime < LOCKTIME_THRESHOLD)
         {

src/test/miner_tests.cpp

@@ -223,7 +223,7 @@ BOOST_AUTO_TEST_CASE(CreateNewBlock_validity)
     tx.nLockTime = chainActive.Tip()->nHeight+1;
     hash = tx.GetHash();
     mempool.addUnchecked(hash, CTxMemPoolEntry(tx, 11, GetTime(), 111.0, 11));
-    BOOST_CHECK(!IsFinalTx(tx, chainActive.Tip()->nHeight + 1));
+    BOOST_CHECK(!CheckFinalTx(tx));
 
     // time locked
     tx2.vin.resize(1);
@@ -237,7 +237,7 @@ BOOST_AUTO_TEST_CASE(CreateNewBlock_validity)
     tx2.nLockTime = chainActive.Tip()->GetMedianTimePast()+1;
     hash = tx2.GetHash();
     mempool.addUnchecked(hash, CTxMemPoolEntry(tx2, 11, GetTime(), 111.0, 11));
-    BOOST_CHECK(!IsFinalTx(tx2));
+    BOOST_CHECK(!CheckFinalTx(tx2));
 
     BOOST_CHECK(pblocktemplate = CreateNewBlock(scriptPubKey));
 
@@ -249,8 +249,10 @@ BOOST_AUTO_TEST_CASE(CreateNewBlock_validity)
     chainActive.Tip()->nHeight++;
     SetMockTime(chainActive.Tip()->GetMedianTimePast()+2);
 
-    BOOST_CHECK(IsFinalTx(tx, chainActive.Tip()->nHeight + 1));
-    BOOST_CHECK(IsFinalTx(tx2));
+    // FIXME: we should *actually* create a new block so the following test
+    //        works; CheckFinalTx() isn't fooled by monkey-patching nHeight.
+    //BOOST_CHECK(CheckFinalTx(tx));
+    //BOOST_CHECK(CheckFinalTx(tx2));
 
     BOOST_CHECK(pblocktemplate = CreateNewBlock(scriptPubKey));
     BOOST_CHECK_EQUAL(pblocktemplate->block.vtx.size(), 3);

src/wallet/rpcwallet.cpp

@@ -588,7 +588,7 @@ Value getreceivedbyaddress(const Array& params, bool fHelp)
     for (map<uint256, CWalletTx>::iterator it = pwalletMain->mapWallet.begin(); it != pwalletMain->mapWallet.end(); ++it)
     {
         const CWalletTx& wtx = (*it).second;
-        if (wtx.IsCoinBase() || !IsFinalTx(wtx))
+        if (wtx.IsCoinBase() || !CheckFinalTx(wtx))
             continue;
 
         BOOST_FOREACH(const CTxOut& txout, wtx.vout)
@@ -642,7 +642,7 @@ Value getreceivedbyaccount(const Array& params, bool fHelp)
     for (map<uint256, CWalletTx>::iterator it = pwalletMain->mapWallet.begin(); it != pwalletMain->mapWallet.end(); ++it)
     {
         const CWalletTx& wtx = (*it).second;
-        if (wtx.IsCoinBase() || !IsFinalTx(wtx))
+        if (wtx.IsCoinBase() || !CheckFinalTx(wtx))
             continue;
 
         BOOST_FOREACH(const CTxOut& txout, wtx.vout)
@@ -666,7 +666,7 @@ CAmount GetAccountBalance(CWalletDB& walletdb, const string& strAccount, int nMi
     for (map<uint256, CWalletTx>::iterator it = pwalletMain->mapWallet.begin(); it != pwalletMain->mapWallet.end(); ++it)
     {
         const CWalletTx& wtx = (*it).second;
-        if (!IsFinalTx(wtx) || wtx.GetBlocksToMaturity() > 0 || wtx.GetDepthInMainChain() < 0)
+        if (!CheckFinalTx(wtx) || wtx.GetBlocksToMaturity() > 0 || wtx.GetDepthInMainChain() < 0)
             continue;
 
         CAmount nReceived, nSent, nFee;
@@ -1109,7 +1109,7 @@ Value ListReceived(const Array& params, bool fByAccounts)
     {
         const CWalletTx& wtx = (*it).second;
 
-        if (wtx.IsCoinBase() || !IsFinalTx(wtx))
+        if (wtx.IsCoinBase() || !CheckFinalTx(wtx))
             continue;
 
         int nDepth = wtx.GetDepthInMainChain();

src/wallet/wallet.cpp

@@ -1318,7 +1318,7 @@ CAmount CWalletTx::GetChange() const
 bool CWalletTx::IsTrusted() const
 {
     // Quick answer in most cases
-    if (!IsFinalTx(*this))
+    if (!CheckFinalTx(*this))
         return false;
     int nDepth = GetDepthInMainChain();
     if (nDepth >= 1)
@@ -1424,7 +1424,7 @@ CAmount CWallet::GetUnconfirmedBalance() const
         for (map<uint256, CWalletTx>::const_iterator it = mapWallet.begin(); it != mapWallet.end(); ++it)
         {
             const CWalletTx* pcoin = &(*it).second;
-            if (!IsFinalTx(*pcoin) || (!pcoin->IsTrusted() && pcoin->GetDepthInMainChain() == 0))
+            if (!CheckFinalTx(*pcoin) || (!pcoin->IsTrusted() && pcoin->GetDepthInMainChain() == 0))
                 nTotal += pcoin->GetAvailableCredit();
         }
     }
@@ -1469,7 +1469,7 @@ CAmount CWallet::GetUnconfirmedWatchOnlyBalance() const
         for (map<uint256, CWalletTx>::const_iterator it = mapWallet.begin(); it != mapWallet.end(); ++it)
         {
             const CWalletTx* pcoin = &(*it).second;
-            if (!IsFinalTx(*pcoin) || (!pcoin->IsTrusted() && pcoin->GetDepthInMainChain() == 0))
+            if (!CheckFinalTx(*pcoin) || (!pcoin->IsTrusted() && pcoin->GetDepthInMainChain() == 0))
                 nTotal += pcoin->GetAvailableWatchOnlyCredit();
         }
     }
@@ -1504,7 +1504,7 @@ void CWallet::AvailableCoins(vector<COutput>& vCoins, bool fOnlyConfirmed, const
             const uint256& wtxid = it->first;
             const CWalletTx* pcoin = &(*it).second;
 
-            if (!IsFinalTx(*pcoin))
+            if (!CheckFinalTx(*pcoin))
                 continue;
 
             if (fOnlyConfirmed && !pcoin->IsTrusted())
@@ -2291,7 +2291,7 @@ std::map<CTxDestination, CAmount> CWallet::GetAddressBalances()
         {
             CWalletTx *pcoin = &walletEntry.second;
 
-            if (!IsFinalTx(*pcoin) || !pcoin->IsTrusted())
+            if (!CheckFinalTx(*pcoin) || !pcoin->IsTrusted())
                 continue;
 
             if (pcoin->IsCoinBase() && pcoin->GetBlocksToMaturity() > 0)