PPCoin: Check stake target and signature for all accepted block

[novacoin.git] / src / main.cpp

diff --git a/src/main.cpp b/src/main.cpp
index 3bc0983..803cd79 100644 (file)
--- a/src/main.cpp
+++ b/src/main.cpp
@@ -710,10 +710,10 @@ int64 GetProofOfStakeReward(int64 nCoinAge)
     return nSubsidy;
 }
 
-static const int64 nTargetTimespan = 7 * 24 * 60 * 60; // one week
-static const int64 nTargetSpacing = 10 * 60;
-static const int64 nInterval = nTargetTimespan / nTargetSpacing;
-static const int64 nMaxClockDrift = 2 * 60 * 60; // 2 hours
+static const int64 nTargetTimespan = 7 * 24 * 60 * 60;  // one week
+static const int64 nTargetSpacingStake = 10 * 60;       // ten minutes
+static const int64 nTargetSpacingWorkMax = 2 * 60 * 60; // two hours
+static const int64 nMaxClockDrift = 2 * 60 * 60;        // two hours
 
 //
 // minimum amount of work that could possibly be required nTime after
@@ -761,6 +761,8 @@ unsigned int static GetNextTargetRequired(const CBlockIndex* pindexLast, bool fP
     // ppcoin: retarget with exponential moving toward target spacing
     CBigNum bnNew;
     bnNew.SetCompact(pindexPrev->nBits);
+    int64 nTargetSpacing = fProofOfStake? nTargetSpacingStake : min(nTargetSpacingWorkMax, nTargetSpacingStake * (1 + pindexLast->nHeight - pindexPrev->nHeight));
+    int64 nInterval = nTargetTimespan / nTargetSpacing;
     bnNew *= ((nInterval - 1) * nTargetSpacing + nActualSpacing + nActualSpacing);
     bnNew /= ((nInterval + 1) * nTargetSpacing);
 
@@ -1079,10 +1081,6 @@ bool CBlock::ConnectBlock(CTxDB& txdb, CBlockIndex* pindex)
     if (!CheckBlock())
         return false;
 
-    // ppcoin: coin stake tx must meet target protocol
-    if (IsProofOfStake() && !vtx[1].CheckProofOfStake(txdb, nBits))
-        return error("ConnectBlock() : Block %s unable to meet hash target for coinstake", GetHash().ToString().c_str());
-
     //// issue here: it doesn't know the version
     unsigned int nTxPos = pindex->nBlockPos + ::GetSerializeSize(CBlock(), SER_DISK) - (2 * GetSizeOfCompactSize(0)) + GetSizeOfCompactSize(vtx.size());
 
@@ -1306,7 +1304,7 @@ bool CBlock::SetBestChain(CTxDB& txdb, CBlockIndex* pindexNew)
 //   quantities so as to generate blocks faster, degrading the system back into
 //   a proof-of-work situation.
 //
-bool CTransaction::CheckProofOfStake(CTxDB& txdb, unsigned int nBits) const
+bool CTransaction::CheckProofOfStake(unsigned int nBits) const
 {
     CBigNum bnTargetPerCoinDay;
     bnTargetPerCoinDay.SetCompact(nBits);
@@ -1318,13 +1316,19 @@ bool CTransaction::CheckProofOfStake(CTxDB& txdb, unsigned int nBits) const
     const CTxIn& txin = vin[0];
 
     // First try finding the previous transaction in database
+    CTxDB txdb("r");
     CTransaction txPrev;
     CTxIndex txindex;
     if (!txPrev.ReadFromDisk(txdb, txin.prevout, txindex))
         return false;  // previous transaction not in main chain
+    txdb.Close();
     if (nTime < txPrev.nTime)
         return false;  // Transaction timestamp violation
 
+    // Verify signature
+    if (!VerifySignature(txPrev, *this, 0))
+        return DoS(100, error("CheckProofOfStake() : VerifySignature failed on coinstake %s", GetHash().ToString().c_str()));
+
     // Read block header
     CBlock block;
     if (!block.ReadFromDisk(txindex.pos.nFile, txindex.pos.nBlockPos, false))
@@ -1340,7 +1344,7 @@ bool CTransaction::CheckProofOfStake(CTxDB& txdb, unsigned int nBits) const
     if (CBigNum(Hash(ss.begin(), ss.end())) <= bnCoinDay * bnTargetPerCoinDay)
         return true;
     else
-        return false;
+        return DoS(100, error("CheckProofOfStake() : check target failed on coinstake %s", GetHash().ToString().c_str()));
 }
 
 // ppcoin: total coin age spent in transaction, in the unit of coin-days.
@@ -1549,19 +1553,14 @@ bool CBlock::AcceptBlock()
     CBlockIndex* pindexPrev = (*mi).second;
     int nHeight = pindexPrev->nHeight+1;
 
-    // ppcoin: check for coinstake duplicate
-    if (IsProofOfStake())
-    {   // check if coinstake is already connected; that would imply the owner
-        // of the coinstake sent multiple blocks with the same coinstake
-        CTxIndex txindex;
-        if (CTxDB("r").ReadTxIndex(vtx[1].GetHash(), txindex))
-            return error("AcceptBlock() : block %s has duplicate coinstake %s", hash.ToString().c_str(), vtx[1].GetHash().ToString().c_str());
-    }
-
     // Check proof-of-work or proof-of-stake
     if (nBits != GetNextTargetRequired(pindexPrev, IsProofOfStake()))
         return DoS(100, error("AcceptBlock() : incorrect proof-of-work/proof-of-stake"));
 
+    // ppcoin: coinstake tx must meet target protocol
+    if (IsProofOfStake() && !vtx[1].CheckProofOfStake(nBits))
+        return error("AcceptBlock() : Block %s unable to meet hash target for coinstake", GetHash().ToString().c_str());
+
     // Check timestamp against prev
     if (GetBlockTime() <= pindexPrev->GetMedianTimePast() || GetBlockTime() + nMaxClockDrift < pindexPrev->GetBlockTime())
         return error("AcceptBlock() : block's timestamp is too early");
@@ -1609,7 +1608,9 @@ bool ProcessBlock(CNode* pfrom, CBlock* pblock)
         return error("ProcessBlock() : already have block (orphan) %s", hash.ToString().substr(0,20).c_str());
 
     // ppcoin: check proof-of-stake
-    if (pblock->IsProofOfStake() && setStakeSeen.count(pblock->GetProofOfStake()))
+    // Limited duplicity on stake: prevents block flood attack
+    // Duplicate stake allowed only when there is orphan child block
+    if (pblock->IsProofOfStake() && setStakeSeen.count(pblock->GetProofOfStake()) && !mapOrphanBlocksByPrev.count(hash))
         return error("ProcessBlock() : duplicate proof-of-stake (%s) for block %s", pblock->GetProofOfStake().ToString().c_str(), hash.ToString().c_str());
 
     // Preliminary checks
@@ -1646,7 +1647,9 @@ bool ProcessBlock(CNode* pfrom, CBlock* pblock)
         // ppcoin: check proof-of-stake
         if (pblock2->IsProofOfStake())
         {
-            if (setStakeSeenOrphan.count(pblock2->GetProofOfStake()))
+            // Limited duplicity on stake: prevents block flood attack
+            // Duplicate stake allowed only when there is orphan child block
+            if (setStakeSeenOrphan.count(pblock2->GetProofOfStake()) && !mapOrphanBlocksByPrev.count(hash))
                 return error("ProcessBlock() : duplicate proof-of-stake (%s) for orphan block %s", pblock2->GetProofOfStake().ToString().c_str(), hash.ToString().c_str());
             else
                 setStakeSeenOrphan.insert(pblock2->GetProofOfStake());
@@ -1830,6 +1833,13 @@ bool LoadBlockIndex(bool fAllowNew)
             return error("LoadBlockIndex() : writing genesis block to disk failed");
         if (!block.AddToBlockIndex(nFile, nBlockPos))
             return error("LoadBlockIndex() : genesis block not accepted");
+
+        // ppcoin: initialize synchronized checkpoint
+        CTxDB txdbc;
+        if (!txdbc.WriteSyncCheckpoint(hashGenesisBlock))
+            return error("LoadBlockIndex() : failed to init sync checkpoint");
+        txdbc.Close();
+        Checkpoints::hashSyncCheckpoint = hashGenesisBlock;
     }
 
     return true;