Stricter handling of orphan transactions

Prevent denial-of-service attacks by banning
peers that send us invalid orphan transactions
and only storing orphan transactions given to
us by a peer while the peer is connected.

src/main.cpp

@@ -63,8 +63,13 @@ struct COrphanBlock {
 map<uint256, COrphanBlock*> mapOrphanBlocks;
 multimap<uint256, COrphanBlock*> mapOrphanBlocksByPrev;
 
-map<uint256, CTransaction> mapOrphanTransactions;
+struct COrphanTx {
+    CTransaction tx;
+    NodeId fromPeer;
+};
+map<uint256, COrphanTx> mapOrphanTransactions;
 map<uint256, set<uint256> > mapOrphanTransactionsByPrev;
+void EraseOrphansFor(NodeId peer);
 
 // Constant stuff for coinbase transactions we create:
 CScript COINBASE_FLAGS;
@@ -264,6 +269,7 @@ void FinalizeNode(NodeId nodeid) {
         mapBlocksInFlight.erase(entry.hash);
     BOOST_FOREACH(const uint256& hash, state->vBlocksToDownload)
         mapBlocksToDownload.erase(hash);
+    EraseOrphansFor(nodeid);
 
     mapNodeState.erase(nodeid);
 }
@@ -461,7 +467,7 @@ CBlockTreeDB *pblocktree = NULL;
 // mapOrphanTransactions
 //
 
-bool AddOrphanTx(const CTransaction& tx)
+bool AddOrphanTx(const CTransaction& tx, NodeId peer)
 {
     uint256 hash = tx.GetHash();
     if (mapOrphanTransactions.count(hash))
@@ -481,21 +487,22 @@ bool AddOrphanTx(const CTransaction& tx)
         return false;
     }
 
-    mapOrphanTransactions[hash] = tx;
+    mapOrphanTransactions[hash].tx = tx;
+    mapOrphanTransactions[hash].fromPeer = peer;
     BOOST_FOREACH(const CTxIn& txin, tx.vin)
         mapOrphanTransactionsByPrev[txin.prevout.hash].insert(hash);
 
-    LogPrint("mempool", "stored orphan tx %s (mapsz %u)\n", hash.ToString(),
-        mapOrphanTransactions.size());
+    LogPrint("mempool", "stored orphan tx %s (mapsz %u prevsz %u)\n", hash.ToString(),
+             mapOrphanTransactions.size(), mapOrphanTransactionsByPrev.size());
     return true;
 }
 
 void static EraseOrphanTx(uint256 hash)
 {
-    map<uint256, CTransaction>::iterator it = mapOrphanTransactions.find(hash);
+    map<uint256, COrphanTx>::iterator it = mapOrphanTransactions.find(hash);
     if (it == mapOrphanTransactions.end())
         return;
-    BOOST_FOREACH(const CTxIn& txin, it->second.vin)
+    BOOST_FOREACH(const CTxIn& txin, it->second.tx.vin)
     {
         map<uint256, set<uint256> >::iterator itPrev = mapOrphanTransactionsByPrev.find(txin.prevout.hash);
         if (itPrev == mapOrphanTransactionsByPrev.end())
@@ -507,6 +514,23 @@ void static EraseOrphanTx(uint256 hash)
     mapOrphanTransactions.erase(it);
 }
 
+void EraseOrphansFor(NodeId peer)
+{
+    int nErased = 0;
+    map<uint256, COrphanTx>::iterator iter = mapOrphanTransactions.begin();
+    while (iter != mapOrphanTransactions.end())
+    {
+        map<uint256, COrphanTx>::iterator maybeErase = iter++; // increment to avoid iterator becoming invalid
+        if (maybeErase->second.fromPeer == peer)
+        {
+            EraseOrphanTx(maybeErase->second.tx.GetHash());
+            ++nErased;
+        }
+    }
+    if (nErased > 0) LogPrint("mempool", "Erased %d orphan tx from peer %d\n", nErased, peer);
+}
+
+
 unsigned int LimitOrphanTxSize(unsigned int nMaxOrphans)
 {
     unsigned int nEvicted = 0;
@@ -514,7 +538,7 @@ unsigned int LimitOrphanTxSize(unsigned int nMaxOrphans)
     {
         // Evict a random orphan:
         uint256 randomhash = GetRandHash();
-        map<uint256, CTransaction>::iterator it = mapOrphanTransactions.lower_bound(randomhash);
+        map<uint256, COrphanTx>::iterator it = mapOrphanTransactions.lower_bound(randomhash);
         if (it == mapOrphanTransactions.end())
             it = mapOrphanTransactions.begin();
         EraseOrphanTx(it->first);
@@ -3777,6 +3801,7 @@ bool static ProcessMessage(CNode* pfrom, string strCommand, CDataStream& vRecv,
                 mempool.mapTx.size());
 
             // Recursively process any orphan transactions that depended on this one
+            set<NodeId> setMisbehaving;
             for (unsigned int i = 0; i < vWorkQueue.size(); i++)
             {
                 map<uint256, set<uint256> >::iterator itByPrev = mapOrphanTransactionsByPrev.find(vWorkQueue[i]);
@@ -3787,25 +3812,36 @@ bool static ProcessMessage(CNode* pfrom, string strCommand, CDataStream& vRecv,
                      ++mi)
                 {
                     const uint256& orphanHash = *mi;
-                    const CTransaction& orphanTx = mapOrphanTransactions[orphanHash];
+                    const CTransaction& orphanTx = mapOrphanTransactions[orphanHash].tx;
+                    NodeId fromPeer = mapOrphanTransactions[orphanHash].fromPeer;
                     bool fMissingInputs2 = false;
                     // Use a dummy CValidationState so someone can't setup nodes to counter-DoS based on orphan
                     // resolution (that is, feeding people an invalid transaction based on LegitTxX in order to get
                     // anyone relaying LegitTxX banned)
                     CValidationState stateDummy;
 
+                    vEraseQueue.push_back(orphanHash);
+
+                    if (setMisbehaving.count(fromPeer))
+                        continue;
                     if (AcceptToMemoryPool(mempool, stateDummy, orphanTx, true, &fMissingInputs2))
                     {
                         LogPrint("mempool", "   accepted orphan tx %s\n", orphanHash.ToString());
                         RelayTransaction(orphanTx);
                         mapAlreadyAskedFor.erase(CInv(MSG_TX, orphanHash));
                         vWorkQueue.push_back(orphanHash);
-                        vEraseQueue.push_back(orphanHash);
                     }
                     else if (!fMissingInputs2)
                     {
-                        // invalid or too-little-fee orphan
-                        vEraseQueue.push_back(orphanHash);
+                        int nDos = 0;
+                        if (stateDummy.IsInvalid(nDos) && nDos > 0)
+                        {
+                            // Punish peer that gave us an invalid orphan tx
+                            Misbehaving(fromPeer, nDos);
+                            setMisbehaving.insert(fromPeer);
+                            LogPrint("mempool", "   invalid orphan tx %s\n", orphanHash.ToString());
+                        }
+                        // too-little-fee orphan
                         LogPrint("mempool", "   removed orphan tx %s\n", orphanHash.ToString());
                     }
                     mempool.check(pcoinsTip);
@@ -3817,7 +3853,7 @@ bool static ProcessMessage(CNode* pfrom, string strCommand, CDataStream& vRecv,
         }
         else if (fMissingInputs)
         {
-            AddOrphanTx(tx);
+            AddOrphanTx(tx, pfrom->GetId());
 
             // DoS prevention: do not allow mapOrphanTransactions to grow unbounded
             unsigned int nEvicted = LimitOrphanTxSize(MAX_ORPHAN_TRANSACTIONS);
@@ -4324,7 +4360,9 @@ bool SendMessages(CNode* pto, bool fSendTrickle)
                 if (pto->addr.IsLocal())
                     LogPrintf("Warning: not banning local peer %s!\n", pto->addr.ToString());
                 else
+                {
                     CNode::Ban(pto->addr);
+                }
             }
             state.fShouldBan = false;
         }
@@ -4538,5 +4576,6 @@ public:
 
         // orphan transactions
         mapOrphanTransactions.clear();
+        mapOrphanTransactionsByPrev.clear();
     }
 } instance_of_cmaincleanup;

src/test/DoS_tests.cpp

@@ -24,7 +24,8 @@
 #include <boost/test/unit_test.hpp>
 
 // Tests this internal-to-main.cpp method:
-extern bool AddOrphanTx(const CTransaction& tx);
+extern bool AddOrphanTx(const CTransaction& tx, NodeId peer);
+extern void EraseOrphansFor(NodeId peer);
 extern unsigned int LimitOrphanTxSize(unsigned int nMaxOrphans);
 extern std::map<uint256, CTransaction> mapOrphanTransactions;
 extern std::map<uint256, std::set<uint256> > mapOrphanTransactionsByPrev;
@@ -174,7 +175,7 @@ BOOST_AUTO_TEST_CASE(DoS_mapOrphans)
         tx.vout[0].nValue = 1*CENT;
         tx.vout[0].scriptPubKey.SetDestination(key.GetPubKey().GetID());
 
-        AddOrphanTx(tx);
+        AddOrphanTx(tx, i);
     }
 
     // ... and 50 that depend on other orphans:
@@ -191,7 +192,7 @@ BOOST_AUTO_TEST_CASE(DoS_mapOrphans)
         tx.vout[0].scriptPubKey.SetDestination(key.GetPubKey().GetID());
         SignSignature(keystore, txPrev, tx, 0);
 
-        AddOrphanTx(tx);
+        AddOrphanTx(tx, i);
     }
 
     // This really-big orphan should be ignored:
@@ -215,7 +216,15 @@ BOOST_AUTO_TEST_CASE(DoS_mapOrphans)
         for (unsigned int j = 1; j < tx.vin.size(); j++)
             tx.vin[j].scriptSig = tx.vin[0].scriptSig;
 
-        BOOST_CHECK(!AddOrphanTx(tx));
+        BOOST_CHECK(!AddOrphanTx(tx, i));
+    }
+
+    // Test EraseOrphansFor:
+    for (NodeId i = 0; i < 3; i++)
+    {
+        size_t sizeBefore = mapOrphanTransactions.size();
+        EraseOrphansFor(i);
+        BOOST_CHECK(mapOrphanTransactions.size() < sizeBefore);
     }
 
     // Test LimitOrphanTxSize() function: