PoW Spam protection (TX V2)

First draft of PoW spam protection - neo-project#414 (comment) - neo-project#408
shargon · Nov 1, 2018 · b6f33df · b6f33df
1 parent fd5e3c6
commit b6f33df
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Showing 12 changed files with 69 additions and 34 deletions.
diff --git a/neo/Consensus/ConsensusService.cs b/neo/Consensus/ConsensusService.cs
@@ -34,7 +34,8 @@ public ConsensusService(NeoSystem system, Wallet wallet)
 
         private bool AddTransaction(Transaction tx, bool verify)
         {
-            if (context.Snapshot.ContainsTransaction(tx.Hash) ||
+            if (tx.Version < 2 || // Don't accept TX without PoW spam protection
+                context.Snapshot.ContainsTransaction(tx.Hash) ||
                 (verify && !tx.Verify(context.Snapshot, context.Transactions.Values)) ||
                 !Plugin.CheckPolicy(tx))
             {
@@ -114,37 +115,23 @@ private void FillContext()
                 Value = amount_netfee,
                 ScriptHash = wallet.GetChangeAddress()
             } };
-            while (true)
+
+            MinerTransaction tx = new MinerTransaction
             {
-                ulong nonce = GetNonce();
-                MinerTransaction tx = new MinerTransaction
-                {
-                    Nonce = (uint)(nonce % (uint.MaxValue + 1ul)),
-                    Attributes = new TransactionAttribute[0],
-                    Inputs = new CoinReference[0],
-                    Outputs = outputs,
-                    Witnesses = new Witness[0]
-                };
-                if (!context.Snapshot.ContainsTransaction(tx.Hash))
-                {
-                    context.Nonce = nonce;
-                    transactions.Insert(0, tx);
-                    break;
-                }
-            }
+                Attributes = new TransactionAttribute[0],
+                Inputs = new CoinReference[0],
+                Outputs = outputs,
+                Witnesses = new Witness[0]
+            };
+
+            tx.ComputeNonce(ntx => !context.Snapshot.ContainsTransaction(ntx.Hash));
+            transactions.Insert(0, tx);
+
             context.TransactionHashes = transactions.Select(p => p.Hash).ToArray();
             context.Transactions = transactions.ToDictionary(p => p.Hash);
             context.NextConsensus = Blockchain.GetConsensusAddress(context.Snapshot.GetValidators(transactions).ToArray());
         }
 
-        private static ulong GetNonce()
-        {
-            byte[] nonce = new byte[sizeof(ulong)];
-            Random rand = new Random();
-            rand.NextBytes(nonce);
-            return nonce.ToUInt64(0);
-        }
-
         private void InitializeConsensus(byte view_number)
         {
             if (view_number == 0)

diff --git a/neo/Network/P2P/Payloads/ClaimTransaction.cs b/neo/Network/P2P/Payloads/ClaimTransaction.cs
@@ -24,7 +24,7 @@ public ClaimTransaction()
 
         protected override void DeserializeExclusiveData(BinaryReader reader)
         {
-            if (Version != 0) throw new FormatException();
+            if (Version > 2) throw new FormatException();
             Claims = reader.ReadSerializableArray<CoinReference>();
             if (Claims.Length == 0) throw new FormatException();
         }

diff --git a/neo/Network/P2P/Payloads/ContractTransaction.cs b/neo/Network/P2P/Payloads/ContractTransaction.cs
@@ -12,7 +12,7 @@ public ContractTransaction()
 
         protected override void DeserializeExclusiveData(BinaryReader reader)
         {
-            if (Version != 0) throw new FormatException();
+            if (Version > 2) throw new FormatException();
         }
     }
 }
diff --git a/neo/Network/P2P/Payloads/InvocationTransaction.cs b/neo/Network/P2P/Payloads/InvocationTransaction.cs
@@ -23,7 +23,7 @@ public InvocationTransaction()
 
         protected override void DeserializeExclusiveData(BinaryReader reader)
         {
-            if (Version > 1) throw new FormatException();
+            if (Version > 2) throw new FormatException();
             Script = reader.ReadVarBytes(65536);
             if (Script.Length == 0) throw new FormatException();
             if (Version >= 1)

diff --git a/neo/Network/P2P/Payloads/IssueTransaction.cs b/neo/Network/P2P/Payloads/IssueTransaction.cs
@@ -27,7 +27,7 @@ public IssueTransaction()
 
         protected override void DeserializeExclusiveData(BinaryReader reader)
         {
-            if (Version > 1) throw new FormatException();
+            if (Version > 2) throw new FormatException();
         }
 
         public override UInt160[] GetScriptHashesForVerifying(Snapshot snapshot)

diff --git a/neo/Network/P2P/Payloads/MinerTransaction.cs b/neo/Network/P2P/Payloads/MinerTransaction.cs
@@ -8,8 +8,6 @@ namespace Neo.Network.P2P.Payloads
 {
     public class MinerTransaction : Transaction
     {
-        public uint Nonce;
-
         public override Fixed8 NetworkFee => Fixed8.Zero;
 
         public override int Size => base.Size + sizeof(uint);

diff --git a/neo/Network/P2P/Payloads/Transaction.cs b/neo/Network/P2P/Payloads/Transaction.cs
@@ -34,6 +34,9 @@ public abstract class Transaction : IEquatable<Transaction>, IInventory
         public TransactionOutput[] Outputs;
         public Witness[] Witnesses { get; set; }
 
+        public uint CreationHeight;
+        public uint Nonce;
+
         private UInt256 _hash = null;
         public UInt256 Hash
         {
@@ -97,6 +100,8 @@ public IReadOnlyDictionary<CoinReference, TransactionOutput> References
 
         public virtual Fixed8 SystemFee => Settings.Default.SystemFee.TryGetValue(Type, out Fixed8 fee) ? fee : Fixed8.Zero;
 
+        public uint Difficult => (uint)BitConverter.ToInt32(Hash.ToArray().Take(4).Reverse().ToArray(), 0);
+
         protected Transaction(TransactionType type)
         {
             this.Type = type;
@@ -109,6 +114,20 @@ void ISerializable.Deserialize(BinaryReader reader)
             OnDeserialized();
         }
 
+        public void ComputeNonce(uint difficult) => ComputeNonce(tx => tx.Difficult <= difficult);
+
+        public void ComputeNonce(Func<Transaction, bool> condition)
+        {
+            var rand = new Random(Environment.TickCount);
+
+            do
+            {
+                _hash = null;
+                Nonce = (uint)rand.Next();
+            }
+            while (!condition(this));
+        }
+
         protected virtual void DeserializeExclusiveData(BinaryReader reader)
         {
         }
@@ -148,6 +167,12 @@ private void DeserializeUnsignedWithoutType(BinaryReader reader)
             Attributes = reader.ReadSerializableArray<TransactionAttribute>(MaxTransactionAttributes);
             Inputs = reader.ReadSerializableArray<CoinReference>();
             Outputs = reader.ReadSerializableArray<TransactionOutput>(ushort.MaxValue + 1);
+
+            if (Version >= 2)
+            {
+                CreationHeight = reader.ReadUInt32();
+                Nonce = reader.ReadUInt32();
+            }
         }
 
         public bool Equals(Transaction other)
@@ -229,6 +254,12 @@ void IVerifiable.SerializeUnsigned(BinaryWriter writer)
             writer.Write(Attributes);
             writer.Write(Inputs);
             writer.Write(Outputs);
+
+            if (Version >= 2)
+            {
+                writer.Write(CreationHeight);
+                writer.Write(Nonce);
+            }
         }
 
         public virtual JObject ToJson()

diff --git a/neo/Network/P2P/RemoteNode.cs b/neo/Network/P2P/RemoteNode.cs
@@ -142,6 +142,16 @@ private void OnSend(IInventory inventory)
             if (Version?.Relay != true) return;
             if (inventory.InventoryType == InventoryType.TX)
             {
+                if (inventory is Transaction tx && tx.Version >= 2)
+                {
+                    // Check PoW spam protection for drop TX
+
+                    if (tx.Difficult > Settings.Default.TransactionDifficult)
+                    {
+                        return;
+                    }
+                }
+
                 if (bloom_filter != null && !bloom_filter.Test((Transaction)inventory))
                     return;
             }

diff --git a/neo/Network/RPC/RpcServer.cs b/neo/Network/RPC/RpcServer.cs
@@ -90,7 +90,7 @@ private JObject GetInvokeResult(byte[] script)
             {
                 InvocationTransaction tx = new InvocationTransaction
                 {
-                    Version = 1,
+                    Version = 2,
                     Script = json["script"].AsString().HexToBytes(),
                     Gas = Fixed8.Parse(json["gas_consumed"].AsString())
                 };

diff --git a/neo/Settings.cs b/neo/Settings.cs
@@ -15,6 +15,7 @@ internal class Settings
         public IReadOnlyDictionary<TransactionType, Fixed8> SystemFee { get; private set; }
         public Fixed8 LowPriorityThreshold { get; private set; }
         public uint SecondsPerBlock { get; private set; }
+        public uint TransactionDifficult { get; private set; }
 
         public static Settings Default { get; private set; }
 
@@ -32,6 +33,7 @@ public Settings(IConfigurationSection section)
             this.SeedList = section.GetSection("SeedList").GetChildren().Select(p => p.Value).ToArray();
             this.SystemFee = section.GetSection("SystemFee").GetChildren().ToDictionary(p => (TransactionType)Enum.Parse(typeof(TransactionType), p.Key, true), p => Fixed8.Parse(p.Value));
             this.SecondsPerBlock = GetValueOrDefault(section.GetSection("SecondsPerBlock"), 15u, p => uint.Parse(p));
+            this.TransactionDifficult = GetValueOrDefault(section.GetSection("TransactionDifficult"), (uint)ushort.MaxValue, p => uint.Parse(p));
             this.LowPriorityThreshold = GetValueOrDefault(section.GetSection("LowPriorityThreshold"), Fixed8.FromDecimal(0.001m), p => Fixed8.Parse(p));
         }
 

diff --git a/neo/Wallets/Helper.cs b/neo/Wallets/Helper.cs
@@ -10,6 +10,13 @@ public static class Helper
     {
         public static byte[] Sign(this IVerifiable verifiable, KeyPair key)
         {
+            if (verifiable is Transaction tx)
+            {
+                // Compute a small PoW spam protection => hash should start with 0x0000
+
+                tx.ComputeNonce(Settings.Default.TransactionDifficult);
+            }
+
             return Crypto.Default.Sign(verifiable.GetHashData(), key.PrivateKey, key.PublicKey.EncodePoint(false).Skip(1).ToArray());
         }
 

diff --git a/neo/Wallets/Wallet.cs b/neo/Wallets/Wallet.cs
@@ -350,7 +350,7 @@ public virtual WalletAccount Import(string nep2, string passphrase)
                     sb.Emit(OpCode.RET, nonce);
                     tx = new InvocationTransaction
                     {
-                        Version = 1,
+                        Version = 2,
                         Script = sb.ToArray()
                     };
                 }