Merge pull request #133 from phoreproject/fix-block-spam

Fix block spam

src/main.cpp

@@ -71,6 +71,14 @@ CCriticalSection cs_main;
 BlockMap mapBlockIndex;
 map<uint256, uint256> mapProofOfStake;
 set<pair<COutPoint, unsigned int> > setStakeSeen;
+
+// maps any spent outputs in the past maxreorgdepth blocks to the height it was spent
+// this means for incoming blocks, we can check that their stake output was not spent before
+// the incoming block tried to use it as a staking input. We can also prevent block spam
+// attacks because then we can check that either the staking input is available in the current
+// active chain, or the staking input was spent in the past 100 blocks after the height
+// of the incoming block.
+map<COutPoint, int> mapStakeSpent;
 map<unsigned int, unsigned int> mapHashedBlocks;
 CChain chainActive;
 CBlockIndex* pindexBestHeader = NULL;
@@ -948,7 +956,7 @@ int GetZerocoinStartHeight()
 }
 
 libzerocoin::ZerocoinParams* GetZerocoinParams(int nHeight) {
-    return nHeight > Params().Zerocoin_LastOldParams() ? Params().Zerocoin_Params() : Params().OldZerocoin_Params(); 
+    return nHeight > Params().Zerocoin_LastOldParams() ? Params().Zerocoin_Params() : Params().OldZerocoin_Params();
 }
 
 void FindMints(vector<CMintMeta> vMintsToFind, vector<CMintMeta>& vMintsToUpdate, vector<CMintMeta>& vMissingMints)
@@ -1714,7 +1722,7 @@ bool AcceptToMemoryPool(CTxMemPool& pool, CValidationState& state, const CTransa
                 hash.ToString(),
                 nFees, ::minRelayTxFee.GetFee(nSize) * 10000);
 
-        
+
         unsigned int scriptVerifyFlags = STANDARD_SCRIPT_VERIFY_FLAGS;
         if (!Params().RequireStandard()) {
             scriptVerifyFlags = GetArg("-promiscuousmempoolflags", scriptVerifyFlags);
@@ -1836,7 +1844,7 @@ bool AcceptableInputs(CTxMemPool& pool, CValidationState& state, const CTransact
             }
         }
     }
-    
+
     // Check for conflicts with in-memory transactions
     if (!tx.IsZerocoinSpend()) {
         LOCK(pool.cs); // protect pool.mapNextTx
@@ -2550,6 +2558,9 @@ bool DisconnectBlock(CBlock& block, CValidationState& state, CBlockIndex* pindex
                 if (coins->vout.size() < out.n + 1)
                     coins->vout.resize(out.n + 1);
                 coins->vout[out.n] = undo.txout;
+
+                // erase the spent input
+                mapStakeSpent.erase(out);
             }
         }
     }
@@ -3010,7 +3021,7 @@ bool ConnectBlock(const CBlock& block, CValidationState& state, CBlockIndex* pin
             if (!view.HaveInputs(tx))
                 return state.DoS(100, error("ConnectBlock() : inputs missing/spent"),
                     REJECT_INVALID, "bad-txns-inputs-missingorspent");
-            
+
             // Check that zPHR mints are not already known
             if (tx.IsZerocoinMint()) {
                 for (auto& out : tx.vout) {
@@ -3181,6 +3192,22 @@ bool ConnectBlock(const CBlock& block, CValidationState& state, CBlockIndex* pin
         if (!pblocktree->AddAddrIndex(vPosAddrid))
             return state.Error("Failed to write address index");
 
+    // add new entries
+    for (const CTransaction tx: block.vtx) {
+        if (tx.IsCoinBase() || tx.IsZerocoinSpend())
+            continue;
+        for (const CTxIn in: tx.vin) {
+            mapStakeSpent.insert(std::make_pair(in.prevout, pindex->nHeight));
+        }
+    }
+
+    // delete old entries
+    for (auto it = mapStakeSpent.begin(); it != mapStakeSpent.end(); ++it) {
+        if (it->second < pindex->nHeight - Params().MaxReorganizationDepth()) {
+            mapStakeSpent.erase(it->first);
+        }
+    }
+
     // add this block to the view's block chain
     view.SetBestBlock(pindex->GetBlockHash());
 
@@ -4328,7 +4355,7 @@ bool ContextualCheckBlock(const CBlock& block, CValidationState& state, CBlockIn
         if(block.nVersion < Params().Zerocoin_HeaderVersion())
             return state.DoS(50, error("CheckBlockHeader() : block version must be above 4 after ZerocoinStartHeight"),
             REJECT_INVALID, "block-version");
-        
+
         vector<CBigNum> vBlockSerials;
         for (const CTransaction& tx : block.vtx) {
             if (!CheckTransaction(tx, true, chainActive.Height() + 1 >= Params().Zerocoin_StartHeight(), state, GetSporkValue(SPORK_17_SEGWIT_ACTIVATION) < block.nTime))
@@ -4540,6 +4567,54 @@ bool AcceptBlock(CBlock& block, CValidationState& state, CBlockIndex** ppindex,
 
     int nHeight = pindex->nHeight;
 
+    if (block.IsProofOfStake()) {
+        LOCK(cs_main);
+
+        CCoinsViewCache coins(pcoinsTip);
+
+        if (!coins.HaveInputs(block.vtx[1])) {
+            // the inputs are spent at the chain tip so we should look at the recently spent outputs
+
+            for (CTxIn in : block.vtx[1].vin) {
+                auto it = mapStakeSpent.find(in.prevout);
+                if (it == mapStakeSpent.end()) {
+                    return false;
+                }
+                if (it->second <= pindexPrev->nHeight) {
+                    return false;
+                }
+            }
+        }
+
+        // if this is on a fork
+        if (!chainActive.Contains(pindexPrev)) {
+            // start at the block we're adding on to
+            CBlockIndex *last = pindexPrev;
+
+            // while that block is not on the main chain
+            while (!chainActive.Contains(last)) {
+                CBlock bl;
+                ReadBlockFromDisk(bl, last);
+                // loop through every spent input from said block
+                for (CTransaction t : bl.vtx) {
+                    for (CTxIn in: t.vin) {
+                        // loop through every spent input in the staking transaction of the new block
+                        for (CTxIn stakeIn : block.vtx[1].vin) {
+                            // if they spend the same input
+                            if (stakeIn.prevout == in.prevout) {
+                                // reject the block
+                                return false;
+                            }
+                        }
+                    }
+                }
+
+                // go to the parent block
+                last = pindexPrev->pprev;
+            }
+        }
+    }
+
     // Write block to history file
     try {
         unsigned int nBlockSize = ::GetSerializeSize(block, SER_DISK, CLIENT_VERSION);