Consensus: finding the best way to create a history of block executions results

src/DBFTPlugin/Consensus/ConsensusService.OnMessage.cs

@@ -10,15 +10,14 @@
 
 using Akka.Actor;
 using Neo.Cryptography;
-using Neo.IO;
 using Neo.Ledger;
 using Neo.Network.P2P;
 using Neo.Network.P2P.Payloads;
 using Neo.SmartContract;
 using Neo.SmartContract.Native;
-using Neo.Wallets;
 using System;
 using System.Collections.Generic;
+using System.IO;
 using System.Linq;
 
 namespace Neo.Consensus
@@ -76,6 +75,12 @@ private void OnConsensusPayload(ExtensiblePayload payload)
 
         private void OnPrepareRequestReceived(ExtensiblePayload payload, PrepareRequest message)
         {
+            if (!File.Exists("prestatehash") || File.ReadAllText("prestatehash") != message.PreStateHash.ToString())
+            {
+                Log($"Invalid request: previous state hash does not match", LogLevel.Warning);
+                return;
+            }
+
             if (context.RequestSentOrReceived || context.NotAcceptingPayloadsDueToViewChanging) return;
             if (message.ValidatorIndex != context.Block.PrimaryIndex || message.ViewNumber != context.ViewNumber) return;
             if (message.Version != context.Block.Version || message.PrevHash != context.Block.PrevHash) return;

src/DBFTPlugin/DBFTPlugin.cs

@@ -8,10 +8,17 @@
 // Redistribution and use in source and binary forms with or without
 // modifications are permitted.
 
+using System.Collections.Generic;
+using System;
+using System.IO;
+using System.Security.Cryptography;
 using Akka.Actor;
 using Neo.ConsoleService;
+using System.Text.Json;
+using Neo.Ledger;
 using Neo.Network.P2P;
 using Neo.Network.P2P.Payloads;
+using Neo.Persistence;
 using Neo.Plugins;
 using Neo.Wallets;
 
@@ -30,6 +37,7 @@ public class DBFTPlugin : Plugin
         public DBFTPlugin()
         {
             RemoteNode.MessageReceived += RemoteNode_MessageReceived;
+            Blockchain.Committing += OnCommitting;
         }
 
         public DBFTPlugin(Settings settings) : this()
@@ -96,5 +104,18 @@ private bool RemoteNode_MessageReceived(NeoSystem system, Message message)
             }
             return true;
         }
+
+        private static void OnCommitting(NeoSystem system, Block block, DataCache snapshot, IReadOnlyList<Blockchain.ApplicationExecuted> applicationExecutedList)
+        {
+            var serializedData = JsonSerializer.SerializeToUtf8Bytes(applicationExecutedList);
+            var hash = ComputeSha256Hash(serializedData);
+            File.WriteAllText("prestatehash", hash);
+        }
+
+        private static string ComputeSha256Hash(byte[] rawData)
+        {
+            var bytes = SHA256.HashData(rawData);
+            return BitConverter.ToString(bytes).Replace("-", "").ToLower();
+        }
     }
 }

src/DBFTPlugin/Messages/PrepareRequest.cs

@@ -19,13 +19,17 @@ public class PrepareRequest : ConsensusMessage
     {
         public uint Version;
         public UInt256 PrevHash;
+        // The execution result hash of the previous block transactions
+        // since we do not need to update it or search it, no merkel tree is needed
+        public UInt256 PreStateHash;
         public ulong Timestamp;
         public ulong Nonce;
         public UInt256[] TransactionHashes;
 
         public override int Size => base.Size
             + sizeof(uint)                      //Version
             + UInt256.Length                    //PrevHash
+            + UInt256.Length                    //PreStateHash
             + sizeof(ulong)                     //Timestamp
             + sizeof(ulong)                     // Nonce
             + TransactionHashes.GetVarSize();   //TransactionHashes
@@ -37,6 +41,7 @@ public override void Deserialize(ref MemoryReader reader)
             base.Deserialize(ref reader);
             Version = reader.ReadUInt32();
             PrevHash = reader.ReadSerializable<UInt256>();
+            PreStateHash = reader.ReadSerializable<UInt256>();
             Timestamp = reader.ReadUInt64();
             Nonce = reader.ReadUInt64();
             TransactionHashes = reader.ReadSerializableArray<UInt256>(ushort.MaxValue);
@@ -55,6 +60,7 @@ public override void Serialize(BinaryWriter writer)
             base.Serialize(writer);
             writer.Write(Version);
             writer.Write(PrevHash);
+            writer.Write(PreStateHash);
             writer.Write(Timestamp);
             writer.Write(Nonce);
             writer.Write(TransactionHashes);