From 57a552c88aba409414750e670f00104181a863ab Mon Sep 17 00:00:00 2001
From: Jeffrey Quesnelle <jq@jeffq.com>
Date: Thu, 5 Oct 2017 16:21:21 -0400
Subject: [PATCH 1/2] support Segregated Witness transactions

---
 .../BitcoinBlockchain.csproj                  |  2 +-
 Sources/BitcoinBlockchain/Data/Transaction.cs | 29 ++++++
 Sources/BitcoinBlockchain/Data/Witness.cs     | 23 +++++
 .../Parser/BlockchainParser.cs                | 92 +++++++++++++++----
 4 files changed, 128 insertions(+), 18 deletions(-)
 create mode 100644 Sources/BitcoinBlockchain/Data/Witness.cs

diff --git a/Sources/BitcoinBlockchain/BitcoinBlockchain.csproj b/Sources/BitcoinBlockchain/BitcoinBlockchain.csproj
index 25df07d..1a20e64 100644
--- a/Sources/BitcoinBlockchain/BitcoinBlockchain.csproj
+++ b/Sources/BitcoinBlockchain/BitcoinBlockchain.csproj
@@ -50,6 +50,7 @@
     <Reference Include="System.Xml" />
   </ItemGroup>
   <ItemGroup>
+    <Compile Include="Data\Witness.cs" />
     <Compile Include="Parser\ByteArrayExtension.cs" />
     <Compile Include="Parser\BinaryReaderExtension.cs" />
     <Compile Include="Data\BlockchainFile.cs" />
@@ -75,7 +76,6 @@
     <CodeAnalysisDictionary Include="CustomDictionary.xml" />
   </ItemGroup>
   <Import Project="$(MSBuildToolsPath)\Microsoft.CSharp.targets" />
-  <Import Project="$(ProgramFiles)\MSBuild\StyleCop\v4.7\StyleCop.targets" />
   <!-- To modify your build process, add your task inside one of the targets below and uncomment it. 
        Other similar extension points exist, see Microsoft.Common.targets.
   <Target Name="BeforeBuild">
diff --git a/Sources/BitcoinBlockchain/Data/Transaction.cs b/Sources/BitcoinBlockchain/Data/Transaction.cs
index 6a3f722..935b1b9 100644
--- a/Sources/BitcoinBlockchain/Data/Transaction.cs
+++ b/Sources/BitcoinBlockchain/Data/Transaction.cs
@@ -26,6 +26,11 @@ public class Transaction
         /// </summary>
         private readonly List<TransactionOutput> transactionOutputs;
 
+        /// <summary>
+        /// Witness data, one for each txin
+        /// </summary>
+        private readonly List<Witness> transactionWitness;
+
         /// <summary>
         /// Initializes a new instance of the <see cref="Transaction" /> class.
         /// </summary>
@@ -33,9 +38,11 @@ public Transaction()
         {
             this.transactionInputs = new List<TransactionInput>();
             this.transactionOutputs = new List<TransactionOutput>();
+            this.transactionWitness = new List<Witness>();
 
             this.Inputs = new ReadOnlyCollection<TransactionInput>(this.transactionInputs);
             this.Outputs = new ReadOnlyCollection<TransactionOutput>(this.transactionOutputs);
+            this.Witness = new ReadOnlyCollection<Witness>(this.transactionWitness);
         }
 
         /// <summary>
@@ -70,6 +77,16 @@ public Transaction()
         /// </summary>
         public ReadOnlyCollection<TransactionOutput> Outputs { get; private set; }
 
+        /// <summary>
+        /// Gets the read-only collection witness data
+        /// </summary>
+        public ReadOnlyCollection<Witness> Witness { get; private set; }
+
+        /// <summary>
+        /// Gets if the transaction has any any witness data (SegWit)
+        /// </summary>
+        public bool HasWitnessData { get { return transactionWitness.Count != 0; } }
+
         /// <summary>
         /// Adds a new input to the list of transaction inputs.
         /// </summary>
@@ -81,6 +98,18 @@ public void AddInput(TransactionInput transactionInput)
             this.transactionInputs.Add(transactionInput);
         }
 
+        /// <summary>
+        /// Adds witness data to the list of transaction witnesses
+        /// There should be one Witness object for each txin
+        /// </summary>
+        /// <param name="witness">
+        /// The witness that should be added to the list of witnesses.
+        /// </param>
+        public void AddWitness(Witness witness)
+        {
+            this.transactionWitness.Add(witness);
+        }
+
         /// <summary>
         /// Adds a new output to the list of transaction outputs.
         /// </summary>
diff --git a/Sources/BitcoinBlockchain/Data/Witness.cs b/Sources/BitcoinBlockchain/Data/Witness.cs
new file mode 100644
index 0000000..df83eb3
--- /dev/null
+++ b/Sources/BitcoinBlockchain/Data/Witness.cs
@@ -0,0 +1,23 @@
+//-----------------------------------------------------------------------
+// <copyright file="Witness.cs">
+// Copyright © Jeffrey Quesnelle. All rights reserved.
+// </copyright>
+//-----------------------------------------------------------------------
+
+namespace BitcoinBlockchain.Data
+{
+    using System.Collections.Generic;
+
+    /// <summary>
+    /// Contains witness data for transaction inputs. Currently the witness data itself is unparsed
+    /// For more information see:
+    /// <c>https://bitcoincore.org/en/segwit_wallet_dev/</c>
+    /// </summary>
+    public class Witness
+    {
+        /// <summary>
+        /// Witness data stack
+        /// </summary>
+        public List<ByteArray> WitnessStack { get; set; }
+    }
+}
diff --git a/Sources/BitcoinBlockchain/Parser/BlockchainParser.cs b/Sources/BitcoinBlockchain/Parser/BlockchainParser.cs
index 2ef6475..e8bc8b9 100644
--- a/Sources/BitcoinBlockchain/Parser/BlockchainParser.cs
+++ b/Sources/BitcoinBlockchain/Parser/BlockchainParser.cs
@@ -152,20 +152,11 @@ private static BlockHeader ParseBlockHeader(BlockMemoryStreamReader blockMemoryS
 
             //// TODO: We need to understand better what is different in V2 and V3.
 
-            if (blockHeader.BlockVersion != 1 &&
-                blockHeader.BlockVersion != 2 &&
-                blockHeader.BlockVersion != 3 &&
-                blockHeader.BlockVersion != 0x20000007 &&
-                blockHeader.BlockVersion != 0x30000000 &&
-                blockHeader.BlockVersion != 4 &&
-                blockHeader.BlockVersion != 0x20000000 &&
-                blockHeader.BlockVersion != 0x20000001 &&
-                blockHeader.BlockVersion != 0x30000001 &&
-                blockHeader.BlockVersion != 0x08000004 &&
-                blockHeader.BlockVersion != 0x20000002 &&
-                blockHeader.BlockVersion != 0x30000007 &&
-                blockHeader.BlockVersion != 0x20000004)
-            {
+            if (   blockHeader.BlockVersion               != 1 &&                                  // original version
+                   blockHeader.BlockVersion               != 2 && blockHeader.BlockVersion != 3 && // used by BIP 34/65/66
+                 ((blockHeader.BlockVersion & 0xE0000000) != 0x20000000)                           // BIP 9 signaling
+               )
+            { 
                 throw new UnknownBlockVersionException(string.Format(CultureInfo.InvariantCulture, "Unknown block version: {0} ({0:X}).", blockHeader.BlockVersion));
             }
 
@@ -250,6 +241,22 @@ private static TransactionOutput ParseTransactionOutput(BlockMemoryStreamReader
             return transactionOutput;
         }
 
+        private static Witness ParseWitness(BlockMemoryStreamReader blockMemoryStreamReader)
+        {
+            Witness witness = new Witness();
+
+            int witnessStackCount = (int)blockMemoryStreamReader.ReadVariableLengthInteger();
+            witness.WitnessStack = new List<ByteArray>();
+
+            for (int witnessStackIndex = 0; witnessStackIndex < witnessStackCount; witnessStackIndex++)
+            {
+                int witnessSize = (int)blockMemoryStreamReader.ReadVariableLengthInteger();
+                witness.WitnessStack.Add(new ByteArray(blockMemoryStreamReader.ReadBytes(witnessSize)));
+            }
+
+            return witness;
+        }
+
         /// <summary>
         /// Parses a Bitcoin transaction.
         /// </summary>
@@ -269,6 +276,19 @@ private static Transaction ParseTransaction(BlockMemoryStreamReader blockMemoryS
 
             int inputsCount = (int)blockMemoryStreamReader.ReadVariableLengthInteger();
 
+            bool isSegWit = false;
+            if (inputsCount == 0)
+            {
+                byte flag = blockMemoryStreamReader.ReadByte();
+                if (flag != 0x01)
+                {
+                    throw new InvalidBlockchainContentException(string.Format(CultureInfo.InvariantCulture,
+                        "Unknown transaction serialization. No input transactions, but SegWit flag was {0} instead of 1.", flag));
+                }
+                inputsCount = (int)blockMemoryStreamReader.ReadVariableLengthInteger();
+                isSegWit = true;
+            }
+
             for (int inputIndex = 0; inputIndex < inputsCount; inputIndex++)
             {
                 TransactionInput transactionInput = BlockchainParser.ParseTransactionInput(blockMemoryStreamReader);
@@ -283,6 +303,17 @@ private static Transaction ParseTransaction(BlockMemoryStreamReader blockMemoryS
                 transaction.AddOutput(transactionOutput);
             }
 
+            int positionInBaseStreamAfterTxOuts = (int)blockMemoryStreamReader.BaseStream.Position;
+
+            if (isSegWit)
+            {
+                for (int inputIndex = 0; inputIndex < inputsCount; inputIndex++)
+                {
+                    Witness witness = BlockchainParser.ParseWitness(blockMemoryStreamReader);
+                    transaction.AddWitness(witness);
+                }
+            }
+
             // TODO: Need to find out more details about the semantic of TransactionLockTime.
             transaction.TransactionLockTime = blockMemoryStreamReader.ReadUInt32();
 
@@ -295,10 +326,37 @@ private static Transaction ParseTransaction(BlockMemoryStreamReader blockMemoryS
                 //// Here we take advantage of the fact that the entire block was loaded as an in-memory buffer.
                 //// The base stream of blockMemoryStreamReader is that in-memory buffer.
 
-                byte[] baseBuffer = blockMemoryStreamReader.GetBuffer();
-                int transactionBufferSize = positionInBaseStreamAfterTransactionEnd - positionInBaseStreamAtTransactionStart;
+                byte[] baseBuffer = blockMemoryStreamReader.GetBuffer(), hash1 = null;
+
+                if (isSegWit)
+                {
+                    using (SHA256Managed innerSHA256 = new SHA256Managed())
+                    {
+                        //// SegWit transactions are still identified by their txid, which is double SHA256 of the old
+                        //// serialization format (i.e. no marker, flag, or witness). So, we need to calculate the txid by 
+                        //// recreating the old format as the input to the hash algorithm.
+
+                        // First, the version number
+                        innerSHA256.TransformBlock(baseBuffer, positionInBaseStreamAtTransactionStart, 4, baseBuffer, positionInBaseStreamAtTransactionStart);
+
+                        // Skip the marker and flag (each one byte), then read in txins and txouts (starting with txin count)
+                        int txStart = positionInBaseStreamAtTransactionStart + 6;
+                        int txSize = positionInBaseStreamAfterTxOuts - txStart;
+                        innerSHA256.TransformBlock(baseBuffer, txStart, txSize, baseBuffer, txStart);
+
+                        ///// After the transactions comes the segregated witness data, which is not included in the txid.
+                        ///// The only thing left to add to calcualte the txid is nLockTime located in the last 4 bytes
+                        int lockTimeStart = positionInBaseStreamAfterTransactionEnd - 4;
+                        innerSHA256.TransformFinalBlock(baseBuffer, lockTimeStart, 4);
+                        hash1 = innerSHA256.Hash;
+                    }
+                }
+                else
+                {
+                    int transactionBufferSize = positionInBaseStreamAfterTransactionEnd - positionInBaseStreamAtTransactionStart;
+                    hash1 = sha256.ComputeHash(baseBuffer, positionInBaseStreamAtTransactionStart, transactionBufferSize);
+                }
 
-                byte[] hash1 = sha256.ComputeHash(baseBuffer, positionInBaseStreamAtTransactionStart, transactionBufferSize);
                 transaction.TransactionHash = new ByteArray(sha256.ComputeHash(hash1).ReverseByteArray());
             }
 

From 84d00b6a96830b872baad596116d3534b19f8c28 Mon Sep 17 00:00:00 2001
From: Jeffrey Quesnelle <jq@jeffq.com>
Date: Fri, 6 Oct 2017 09:51:52 -0400
Subject: [PATCH 2/2] fixes version handling

---
 .../Parser/BlockchainParser.cs                 | 18 ++++++++++--------
 1 file changed, 10 insertions(+), 8 deletions(-)

diff --git a/Sources/BitcoinBlockchain/Parser/BlockchainParser.cs b/Sources/BitcoinBlockchain/Parser/BlockchainParser.cs
index e8bc8b9..045564e 100644
--- a/Sources/BitcoinBlockchain/Parser/BlockchainParser.cs
+++ b/Sources/BitcoinBlockchain/Parser/BlockchainParser.cs
@@ -150,14 +150,16 @@ private static BlockHeader ParseBlockHeader(BlockMemoryStreamReader blockMemoryS
 
             blockHeader.BlockVersion = blockMemoryStreamReader.ReadUInt32();
 
-            //// TODO: We need to understand better what is different in V2 and V3.
-
-            if (   blockHeader.BlockVersion               != 1 &&                                  // original version
-                   blockHeader.BlockVersion               != 2 && blockHeader.BlockVersion != 3 && // used by BIP 34/65/66
-                 ((blockHeader.BlockVersion & 0xE0000000) != 0x20000000)                           // BIP 9 signaling
-               )
-            { 
-                throw new UnknownBlockVersionException(string.Format(CultureInfo.InvariantCulture, "Unknown block version: {0} ({0:X}).", blockHeader.BlockVersion));
+            switch (blockHeader.BlockVersion)
+            {
+                case 1: case 2: case 3: case 4: // original block version and BIP 34/65/66
+                    break;
+                default: 
+                    if ((blockHeader.BlockVersion & 0xE0000000) != 0x20000000 && // BIP 9 signaling
+                        (blockHeader.BlockVersion & 0x08000000) != 0x08000000    // BitPay adaptive block size HF signaling
+                       ) 
+                        throw new UnknownBlockVersionException(string.Format(CultureInfo.InvariantCulture, "Unknown block version: {0} ({0:X}).", blockHeader.BlockVersion));
+                    break;
             }
 
             blockHeader.PreviousBlockHash = new ByteArray(blockMemoryStreamReader.ReadBytes(32).ReverseByteArray());