private bool Matches(StoredBlock block1, StoredBlock block2)
{
if (block1 == null || block2 == null)
{
return false;
}
return block1.Hash.SequenceEqual(block2.Hash);
}
public void Append(StoredBlock block)
{
//todo: add XMLDOC
StoredBlock lastBlock = blocks.Last();
if (!lastBlock.Hash.SequenceEqual(block.Header.PrevBlock))
{
throw new ArgumentException($"Added block should reference last block in the {nameof(Subchain)}.", nameof(block));
}
blocks.Add(block);
}
/// <summary>
/// Returns an updated state, with replaced blocks.
/// </summary>
/// <param name="oldBlock">The block to replace.</param>
/// <param name="newBlock">The replacing block.</param>
/// <returns> If replacement affects state, then a new state instance is returned; otherwise, current instance is returned.</returns>
public BlockchainState Update(StoredBlock oldBlock, StoredBlock newBlock)
{
if (Contains(oldBlock))
{
return new BlockchainState(
Matches(BestHeader, oldBlock) ? newBlock : BestHeader,
Matches(BestChain, oldBlock) ? newBlock : BestChain);
}
return this;
}
public static UnspentOutput Create(StoredBlock block, Tx transaction, int outputNumber)
{
TxOut output = transaction.Outputs[outputNumber];
return new UnspentOutput(
block.Height,
CryptoUtils.DoubleSha256(BitcoinStreamWriter.GetBytes(transaction.Write)),
outputNumber,
output.Value,
output.PubkeyScript);
}
public void AddBlock(StoredBlock block)
{
transactionalResource.Enlist();
storage.AddBlock(block);
//todo: add tests
if (lastChain != null)
{
lastChain.Append(block);
lastChain.Truncate(CachedChainMinLength, CachedChainMaxLength);
}
}
/// <summary>
/// Checks that the nBits field of a block follow protocol rules.
/// </summary>
internal static bool IsNBitsValid(StoredBlock block, Subchain parentChain)
{
//todo: add test for this method
StoredBlock parentBlock = parentChain.GetBlockByOffset(0);
BigInteger blockDifficultyTarget = DifficultyUtils.NBitsToTarget(block.Header.NBits);
if (block.Height%DifficultyUtils.DifficultyAdjustmentIntervalInBlocks != 0)
{
BigInteger parentBlockDifficultyTarget = DifficultyUtils.NBitsToTarget(parentBlock.Header.NBits);
if (blockDifficultyTarget != parentBlockDifficultyTarget)
{
return false;
}
}
else
{
StoredBlock baseBlock = parentChain.GetBlockByHeight(block.Height - DifficultyUtils.DifficultyAdjustmentIntervalInBlocks);
// todo: check against non-bugged value and allow some percent-based difference?
// Note: There is a known bug here. It known as "off-by-one" or "Time Warp Bug".
// Bug Description: http://bitcoin.stackexchange.com/questions/20597/where-exactly-is-the-off-by-one-difficulty-bug
// Related Attack Description: https://bitcointalk.org/index.php?topic=43692.msg521772#msg521772
uint timeSpent = parentBlock.Header.Timestamp - baseBlock.Header.Timestamp;
BigInteger oldTarget = DifficultyUtils.NBitsToTarget(parentBlock.Header.NBits);
var newTarget = DifficultyUtils.CalculateNewTarget(timeSpent, oldTarget);
// this rounds newTarget value to a value that would fit into NBits
uint newNBits = DifficultyUtils.TargetToNBits(newTarget);
newTarget = DifficultyUtils.NBitsToTarget(newNBits);
if (blockDifficultyTarget != newTarget)
{
return false;
}
}
return true;
}
private StoredBlock SetIsInBestHeaderChain(StoredBlock block, bool val)
{
StoredBlockBuilder builder = new StoredBlockBuilder(block);
builder.IsInBestHeaderChain = val;
StoredBlock newBlock = builder.Build();
currentState = currentState.Update(block, newBlock);
return newBlock;
}
private UnspentOutputsUpdate PrepareUnspentOutputsUpdate(StoredBlock block, BlockMessage blockMessage)
{
ScriptParser parser = new ScriptParser();
ulong inputsSum = GetBlockReward(block);
ulong outputsSum = 0;
UnspentOutputsUpdate update = new UnspentOutputsUpdate(storage);
for (int transactionNumber = 0; transactionNumber < blockMessage.Transactions.Length; transactionNumber++)
{
Tx transaction = blockMessage.Transactions[transactionNumber];
ulong transactionInputsSum = 0;
ulong transactionOutputsSum = 0;
byte[] transactionHash = CryptoUtils.DoubleSha256(BitcoinStreamWriter.GetBytes(transaction.Write));
List<UnspentOutput> unspentOutputs = update.FindUnspentOutputs(transactionHash);
if (unspentOutputs.Any())
{
//todo: use network settings
if (block.Height == 91842 || block.Height == 91880)
{
// this blocks are exceptions from BIP-30
foreach (UnspentOutput unspentOutput in unspentOutputs)
{
update.Spend(unspentOutput.TransactionHash, unspentOutput.OutputNumber, block);
}
}
else
{
throw new BitcoinProtocolViolationException(
$"The transaction '{BitConverter.ToString(transactionHash)}'" +
$" in block '{BitConverter.ToString(block.Hash)}'" +
$" has same hash as an existing unspent transaction (see BIP-30).");
}
}
//todo: check transaction hash against genesis block transaction hash
if (transactionNumber != 0)
{
foreach (TxIn input in transaction.Inputs)
{
UnspentOutput output = update.FindUnspentOutput(input.PreviousOutput.Hash, input.PreviousOutput.Index);
if (output == null)
{
throw new BitcoinProtocolViolationException(
$"The input of the transaction '{BitConverter.ToString(transactionHash)}'" +
$" in block '{BitConverter.ToString(block.Hash)}'" +
$" has been already spent or did not exist.");
}
//todo: check for overflow
transactionInputsSum += output.Sum;
List<ScriptCommand> inputCommands;
if (!parser.TryParse(input.SignatureScript, out inputCommands))
{
throw new BitcoinProtocolViolationException(
$"The transaction '{BitConverter.ToString(transactionHash)}'" +
$" in block '{BitConverter.ToString(block.Hash)}'" +
$" has an invalid signature script.");
}
if (inputCommands.Any(c => !IsValidSignatureCommand(c.Code)))
{
throw new BitcoinProtocolViolationException(
$"The transaction '{BitConverter.ToString(transactionHash)}'" +
$" in block '{BitConverter.ToString(block.Hash)}'" +
$" has forbidden commands in the signature script.");
}
//todo: check signature for the output
update.Spend(output.TransactionHash, output.OutputNumber, block);
}
}
for (int outputNumber = 0; outputNumber < transaction.Outputs.Length; outputNumber++)
{
TxOut output = transaction.Outputs[outputNumber];
//todo: check for overflow
transactionOutputsSum += output.Value;
List<ScriptCommand> commands;
if (!parser.TryParse(output.PubkeyScript, out commands))
{
//todo: how Bitcoin Core works in this scenario?
throw new BitcoinProtocolViolationException(
$"The output of transaction '{BitConverter.ToString(transactionHash)}'" +
$" in block '{BitConverter.ToString(block.Hash)}'" +
$" has an invalid pubkey script script.");
}
UnspentOutput unspentOutput = UnspentOutput.Create(block, transaction, outputNumber);
update.Add(unspentOutput);
}
if (transactionNumber != 0 && transactionInputsSum < transactionOutputsSum)
{
// for coinbase transaction output sum is checked later as part of total block inputs, outputs and reward sums equation
throw new BitcoinProtocolViolationException(
$"The sum of the inputs in the transaction '{BitConverter.ToString(transactionHash)}'" +
$" in block '{BitConverter.ToString(block.Hash)}'" +
$" is less than the sum of the outputs.");
}
//todo: check for overflow
inputsSum += transactionInputsSum;
//todo: check for overflow
outputsSum += transactionOutputsSum;
}
if (inputsSum != outputsSum)
{
throw new BitcoinProtocolViolationException(
$"The sum of the inputs and the reward" +
$" in the block '{BitConverter.ToString(block.Hash)}'" +
$" does not match the sum of the outputs.");
}
return update;
}
private bool IsBetterHeaderThan(StoredBlock block1, StoredBlock block2)
{
//todo: are there any other conditions?
if (block1.TotalWork > block2.TotalWork)
{
return true;
}
if (block1.TotalWork < block2.TotalWork)
{
return false;
}
return block1.Header.Timestamp < block2.Header.Timestamp;
}
private ulong GetBlockReward(StoredBlock block)
{
//todo: use network settings
ulong reward = 5000000000;
int height = block.Height;
//todo: use network settings
while (height >= 210000)
{
height -= 210000;
reward /= 2;
}
return reward;
}
private StoredBlock AddHeader(StoredBlock block)
{
StoredBlock storedBlock = storage.FindBlockByHash(block.Hash);
if (storedBlock != null)
{
return storedBlock;
}
Subchain parentChain = storage.FindSubchain(block.Header.PrevBlock, Blockchain.AnalyzedSubchainLength);
if (parentChain == null)
{
return block;
}
StoredBlock parentBlock = parentChain.GetBlockByOffset(0);
block = block.AppendAfter(parentBlock);
if (!BlockHeaderValidator.IsValid(block, parentChain))
{
throw new BitcoinProtocolViolationException("An invalid header was received.");
}
storage.AddBlock(block);
UpdateBestHeadersChain(block);
return block;
}
public StoredBlockBuilder(StoredBlock block)
{
Header = block.Header;
Hash = block.Hash;
Height = block.Height;
TotalWork = block.TotalWork;
HasContent = block.HasContent;
IsInBestHeaderChain = block.IsInBestHeaderChain;
IsInBestBlockChain = block.IsInBestBlockChain;
}
private bool Contains(StoredBlock block)
{
return Matches(BestHeader, block) || Matches(BestChain, block);
}
public static bool IsValid(StoredBlock block, Subchain parentChain)
{
return IsTimeStampValid(block, parentChain) && IsNBitsValid(block, parentChain);
}
public static bool IsValid(StoredBlock storedBlock, BlockMessage block)
{
//todo: add other validations, recheck each field constraints
return IsValidCoinbaseTransaction(block);
}
public BlockchainState SetBestHeader(StoredBlock newBestHeader)
{
return new BlockchainState(newBestHeader, BestChain);
}
//todo: make this class internal and move related generic storage tests to TestUtils or make Blockchain.State public
public BlockchainState(StoredBlock bestHeader, StoredBlock bestChain)
{
BestHeader = bestHeader;
BestChain = bestChain;
}
private void UpdateBestHeadersChain(StoredBlock block)
{
if (!IsBetterHeaderThan(block, currentState.BestHeader))
{
return;
}
StoredBlock newHead = block;
StoredBlock oldHead = currentState.BestHeader;
//todo: this code should be wrapped in transaction, init should be called on failure
while (!newHead.Hash.SequenceEqual(oldHead.Hash))
{
bool markNewHead = newHead.Height >= oldHead.Height;
bool markOldHead = oldHead.Height >= newHead.Height;
if (markNewHead)
{
newHead = SetIsInBestHeaderChain(newHead, true);
storage.UpdateBlock(newHead);
newHead = storage.FindBlockByHash(newHead.Header.PrevBlock);
}
if (markOldHead)
{
oldHead = SetIsInBestHeaderChain(oldHead, false);
storage.UpdateBlock(oldHead);
oldHead = storage.FindBlockByHash(oldHead.Header.PrevBlock);
}
}
currentState = currentState.SetBestHeader(block);
}
public void UpdateBlock(StoredBlock block)
{
transactionalResource.Enlist();
storage.UpdateBlock(block);
if (lastChain != null)
{
//todo: cashing is a little bit ugly
List<StoredBlock> chainBlocks = new List<StoredBlock>(lastChain.Length);
for (int i = lastChain.Length - 1; i >= 0; i--)
{
StoredBlock chainBlock = lastChain.GetBlockByOffset(i);
if (chainBlock.Hash.SequenceEqual(block.Hash))
{
chainBlocks.Add(block);
}
else
{
chainBlocks.Add(chainBlock);
}
}
lastChain = new Subchain(chainBlocks);
}
}
/// <summary>
/// Checks that timestamp of the block is after median time of the last 11 blocks.
/// </summary>
internal static bool IsTimeStampValid(StoredBlock block, Subchain parentChain)
{
//todo: use network settings
const int medianBlockCount = 11;
List<uint> oldTimestamps = new List<uint>(medianBlockCount);
for (int i = 0; i < medianBlockCount && i < parentChain.Length; i++)
{
oldTimestamps.Add(parentChain.GetBlockByOffset(i).Header.Timestamp);
}
oldTimestamps.Sort();
uint medianTimestamp = oldTimestamps[oldTimestamps.Count/2];
return block.Header.Timestamp > medianTimestamp;
}
/// <summary>
/// Returns a copy of this block with the <see cref="Height"/> and <see cref="TotalWork"/> properties based on the given parent block.
/// </summary>
/// <param name="parentBlock">The parent block.</param>
public StoredBlock AppendAfter(StoredBlock parentBlock)
{
double blockWork = DifficultyUtils.DifficultyTargetToWork(DifficultyUtils.NBitsToTarget(Header.NBits));
StoredBlockBuilder builder = new StoredBlockBuilder(this);
builder.Height = parentBlock.Height + 1;
builder.TotalWork = parentBlock.TotalWork + blockWork;
return builder.Build();
}
