// disconnectTransactions updates the passed map by undoing transaction and
// spend information for all transactions in the passed block. Only
// transactions in the passed map are updated.
func disconnectTransactions(txStore TxStore, block *btcutil.Block) error {
// Loop through all of the transactions in the block to see if any of
// them are ones that need to be undone based on the transaction store.
for _, tx := range block.Transactions() {
// Clear this transaction from the transaction store if needed.
// Only clear it rather than deleting it because the transaction
// connect code relies on its presence to decide whether or not
// to update the store and any transactions which exist on both
// sides of a fork would otherwise not be updated.
if txD, exists := txStore[*tx.Sha()]; exists {
txD.Tx = nil
txD.BlockHeight = 0
txD.Spent = nil
txD.Err = database.ErrTxShaMissing
}
// Unspend the origin transaction output.
for _, txIn := range tx.MsgTx().TxIn {
originHash := &txIn.PreviousOutPoint.Hash
originIndex := txIn.PreviousOutPoint.Index
originTx, exists := txStore[*originHash]
if exists && originTx.Tx != nil && originTx.Err == nil {
if originIndex > uint32(len(originTx.Spent)) {
continue
}
originTx.Spent[originIndex] = false
}
}
}
return nil
}
// checkBlockScripts executes and validates the scripts for all transactions in
// the passed block using multiple goroutines.
func checkBlockScripts(block *btcutil.Block, utxoView *UtxoViewpoint, scriptFlags txscript.ScriptFlags, sigCache *txscript.SigCache) error {
// Collect all of the transaction inputs and required information for
// validation for all transactions in the block into a single slice.
numInputs := 0
for _, tx := range block.Transactions() {
numInputs += len(tx.MsgTx().TxIn)
}
txValItems := make([]*txValidateItem, 0, numInputs)
for _, tx := range block.Transactions() {
for txInIdx, txIn := range tx.MsgTx().TxIn {
// Skip coinbases.
if txIn.PreviousOutPoint.Index == math.MaxUint32 {
continue
}
txVI := &txValidateItem{
txInIndex: txInIdx,
txIn: txIn,
tx: tx,
}
txValItems = append(txValItems, txVI)
}
}
// Validate all of the inputs.
validator := newTxValidator(utxoView, scriptFlags, sigCache)
return validator.Validate(txValItems)
}
// indexBlock extract all of the standard addresses from all of the transactions
// in the passed block and maps each of them to the assocaited transaction using
// the passed map.
func (idx *AddrIndex) indexBlock(data writeIndexData, block *btcutil.Block, view *blockchain.UtxoViewpoint) {
for txIdx, tx := range block.Transactions() {
// Coinbases do not reference any inputs. Since the block is
// required to have already gone through full validation, it has
// already been proven on the first transaction in the block is
// a coinbase.
if txIdx != 0 {
for _, txIn := range tx.MsgTx().TxIn {
// The view should always have the input since
// the index contract requires it, however, be
// safe and simply ignore any missing entries.
origin := &txIn.PreviousOutPoint
entry := view.LookupEntry(&origin.Hash)
if entry == nil {
continue
}
pkScript := entry.PkScriptByIndex(origin.Index)
idx.indexPkScript(data, pkScript, txIdx)
}
}
for _, txOut := range tx.MsgTx().TxOut {
idx.indexPkScript(data, txOut.PkScript, txIdx)
}
}
}
// checkProofOfWork ensures the block header bits which indicate the target
// difficulty is in min/max range and that the block hash is less than the
// target difficulty as claimed.
//
//
// The flags modify the behavior of this function as follows:
// - BFNoPoWCheck: The check to ensure the block hash is less than the target
// difficulty is not performed.
func checkProofOfWork(block *btcutil.Block, powLimit *big.Int, flags BehaviorFlags) error {
// The target difficulty must be larger than zero.
target := CompactToBig(block.MsgBlock().Header.Bits)
if target.Sign() <= 0 {
str := fmt.Sprintf("block target difficulty of %064x is too low",
target)
return ruleError(ErrUnexpectedDifficulty, str)
}
// The target difficulty must be less than the maximum allowed.
if target.Cmp(powLimit) > 0 {
str := fmt.Sprintf("block target difficulty of %064x is "+
"higher than max of %064x", target, powLimit)
return ruleError(ErrUnexpectedDifficulty, str)
}
// The block hash must be less than the claimed target unless the flag
// to avoid proof of work checks is set.
if flags&BFNoPoWCheck != BFNoPoWCheck {
// The block hash must be less than the claimed target.
blockHash, err := block.Sha()
if err != nil {
return err
}
hashNum := ShaHashToBig(blockHash)
if hashNum.Cmp(target) > 0 {
str := fmt.Sprintf("block hash of %064x is higher than "+
"expected max of %064x", hashNum, target)
return ruleError(ErrHighHash, str)
}
}
return nil
}
// getPrevNodeFromBlock returns a block node for the block previous to the
// passed block (the passed block's parent). When it is already in the memory
// block chain, it simply returns it. Otherwise, it loads the previous block
// from the block database, creates a new block node from it, and returns it.
// The returned node will be nil if the genesis block is passed.
func (b *BlockChain) getPrevNodeFromBlock(block *btcutil.Block) (*blockNode, error) {
// Genesis block.
prevHash := &block.MsgBlock().Header.PrevBlock
if prevHash.IsEqual(zeroHash) {
return nil, nil
}
// Latest checkpoint block
if prevHash.IsEqual(b.chainParams.Checkpoints[len(b.chainParams.Checkpoints)-1].Hash) {
return nil, nil
}
// Return the existing previous block node if it's already there.
if bn, ok := b.index[*prevHash]; ok {
return bn, nil
}
// Dynamically load the previous block from the block database, create
// a new block node for it, and update the memory chain accordingly.
prevBlockNode, err := b.loadBlockNode(prevHash)
if err != nil {
return nil, err
}
return prevBlockNode, nil
}
// checkBIP0030 ensures blocks do not contain duplicate transactions which
// 'overwrite' older transactions that are not fully spent. This prevents an
// attack where a coinbase and all of its dependent transactions could be
// duplicated to effectively revert the overwritten transactions to a single
// confirmation thereby making them vulnerable to a double spend.
//
// For more details, see https://en.bitcoin.it/wiki/BIP_0030 and
// http://r6.ca/blog/20120206T005236Z.html.
//
// This function MUST be called with the chain state lock held (for reads).
func (b *BlockChain) checkBIP0030(node *blockNode, block *btcutil.Block, view *UtxoViewpoint) error {
// Fetch utxo details for all of the transactions in this block.
// Typically, there will not be any utxos for any of the transactions.
fetchSet := make(map[chainhash.Hash]struct{})
for _, tx := range block.Transactions() {
fetchSet[*tx.Hash()] = struct{}{}
}
err := view.fetchUtxos(b.db, fetchSet)
if err != nil {
return err
}
// Duplicate transactions are only allowed if the previous transaction
// is fully spent.
for _, tx := range block.Transactions() {
txEntry := view.LookupEntry(tx.Hash())
if txEntry != nil && !txEntry.IsFullySpent() {
str := fmt.Sprintf("tried to overwrite transaction %v "+
"at block height %d that is not fully spent",
tx.Hash(), txEntry.blockHeight)
return ruleError(ErrOverwriteTx, str)
}
}
return nil
}
// ConnectBlock is invoked by the index manager when a new block has been
// connected to the main chain. This indexer adds a mapping for each address
// the transactions in the block involve.
//
// This is part of the Indexer interface.
func (idx *AddrIndex) ConnectBlock(dbTx database.Tx, block *btcutil.Block, view *blockchain.UtxoViewpoint) error {
// The offset and length of the transactions within the serialized
// block.
txLocs, err := block.TxLoc()
if err != nil {
return err
}
// Get the internal block ID associated with the block.
blockID, err := dbFetchBlockIDByHash(dbTx, block.Hash())
if err != nil {
return err
}
// Build all of the address to transaction mappings in a local map.
addrsToTxns := make(writeIndexData)
idx.indexBlock(addrsToTxns, block, view)
// Add all of the index entries for each address.
addrIdxBucket := dbTx.Metadata().Bucket(addrIndexKey)
for addrKey, txIdxs := range addrsToTxns {
for _, txIdx := range txIdxs {
err := dbPutAddrIndexEntry(addrIdxBucket, addrKey,
blockID, txLocs[txIdx])
if err != nil {
return err
}
}
}
return nil
}
// makeUtxoView creates a mock unspent transaction output view by using the
// transaction index in order to look up all inputs referenced by the
// transactions in the block. This is sometimes needed when catching indexes up
// because many of the txouts could actually already be spent however the
// associated scripts are still required to index them.
func makeUtxoView(dbTx database.Tx, block *btcutil.Block) (*blockchain.UtxoViewpoint, error) {
view := blockchain.NewUtxoViewpoint()
for txIdx, tx := range block.Transactions() {
// Coinbases do not reference any inputs. Since the block is
// required to have already gone through full validation, it has
// already been proven on the first transaction in the block is
// a coinbase.
if txIdx == 0 {
continue
}
// Use the transaction index to load all of the referenced
// inputs and add their outputs to the view.
for _, txIn := range tx.MsgTx().TxIn {
originOut := &txIn.PreviousOutPoint
originTx, err := dbFetchTx(dbTx, &originOut.Hash)
if err != nil {
return nil, err
}
view.AddTxOuts(btcutil.NewTx(originTx), 0)
}
}
return view, nil
}
// connectBlock handles connecting the passed node/block to the end of the main
// (best) chain.
func (b *BlockChain) connectBlock(node *blockNode, block *btcutil.Block) error {
// Make sure it's extending the end of the best chain.
prevHash := &block.MsgBlock().Header.PrevBlock
if b.bestChain != nil && !prevHash.IsEqual(b.bestChain.hash) {
return fmt.Errorf("connectBlock must be called with a block " +
"that extends the main chain")
}
// Insert the block into the database which houses the main chain.
_, err := b.db.InsertBlock(block)
if err != nil {
return err
}
// Add the new node to the memory main chain indices for faster
// lookups.
node.inMainChain = true
b.index[*node.hash] = node
b.depNodes[*prevHash] = append(b.depNodes[*prevHash], node)
// This node is now the end of the best chain.
b.bestChain = node
// Notify the caller that the block was connected to the main chain.
// The caller would typically want to react with actions such as
// updating wallets.
b.sendNotification(NTBlockConnected, block)
return nil
}
// connectTransactions updates the passed map by applying transaction and
// spend information for all the transactions in the passed block. Only
// transactions in the passed map are updated.
func connectTransactions(txStore TxStore, block *btcutil.Block) error {
// Loop through all of the transactions in the block to see if any of
// them are ones we need to update and spend based on the results map.
for _, tx := range block.Transactions() {
// Update the transaction store with the transaction information
// if it's one of the requested transactions.
msgTx := tx.MsgTx()
if txD, exists := txStore[*tx.Sha()]; exists {
txD.Tx = tx
txD.BlockHeight = block.Height()
txD.Spent = make([]bool, len(msgTx.TxOut))
txD.Err = nil
}
// Spend the origin transaction output.
for _, txIn := range msgTx.TxIn {
originHash := &txIn.PreviousOutPoint.Hash
originIndex := txIn.PreviousOutPoint.Index
if originTx, exists := txStore[*originHash]; exists {
if originIndex > uint32(len(originTx.Spent)) {
continue
}
originTx.Spent[originIndex] = true
}
}
}
return nil
}
// dbRemoveTxIndexEntries uses an existing database transaction to remove the
// latest transaction entry for every transaction in the passed block.
func dbRemoveTxIndexEntries(dbTx database.Tx, block *btcutil.Block) error {
for _, tx := range block.Transactions() {
err := dbRemoveTxIndexEntry(dbTx, tx.Hash())
if err != nil {
return err
}
}
return nil
}
// DropAfterBlockBySha will remove any blocks from the database after
// the given block.
func (db *LevelDb) DropAfterBlockBySha(sha *wire.ShaHash) (rerr error) {
db.dbLock.Lock()
defer db.dbLock.Unlock()
defer func() {
if rerr == nil {
rerr = db.processBatches()
} else {
db.lBatch().Reset()
}
}()
startheight := db.nextBlock - 1
keepidx, err := db.getBlkLoc(sha)
if err != nil {
// should the error here be normalized ?
log.Tracef("block loc failed %v ", sha)
return err
}
for height := startheight; height > keepidx; height = height - 1 {
var blk *btcutil.Block
blksha, buf, err := db.getBlkByHeight(height)
if err != nil {
return err
}
blk, err = btcutil.NewBlockFromBytes(buf)
if err != nil {
return err
}
for _, tx := range blk.MsgBlock().Transactions {
err = db.unSpend(tx)
if err != nil {
return err
}
}
// rather than iterate the list of tx backward, do it twice.
for _, tx := range blk.Transactions() {
var txUo txUpdateObj
txUo.delete = true
db.txUpdateMap[*tx.Sha()] = &txUo
}
db.lBatch().Delete(shaBlkToKey(blksha))
db.lBatch().Delete(int64ToKey(height))
}
// update the last block cache
db.lastBlkShaCached = true
db.lastBlkSha = *sha
db.lastBlkIdx = keepidx
db.nextBlock = keepidx + 1
return nil
}
// SubmitBlockAsync returns an instance of a type that can be used to get the
// result of the RPC at some future time by invoking the Receive function on the
// returned instance.
//
// See SubmitBlock for the blocking version and more details.
func (c *Client) SubmitBlockAsync(block *btcutil.Block, options *btcjson.SubmitBlockOptions) FutureSubmitBlockResult {
blockHex := ""
if block != nil {
blockBytes, err := block.Bytes()
if err != nil {
return newFutureError(err)
}
blockHex = hex.EncodeToString(blockBytes)
}
cmd := btcjson.NewSubmitBlockCmd(blockHex, options)
return c.sendCmd(cmd)
}
// dbIndexDisconnectBlock removes all of the index entries associated with the
// given block using the provided indexer and updates the tip of the indexer
// accordingly. An error will be returned if the current tip for the indexer is
// not the passed block.
func dbIndexDisconnectBlock(dbTx database.Tx, indexer Indexer, block *btcutil.Block, view *blockchain.UtxoViewpoint) error {
// Assert that the block being disconnected is the current tip of the
// index.
idxKey := indexer.Key()
curTipHash, _, err := dbFetchIndexerTip(dbTx, idxKey)
if err != nil {
return err
}
if !curTipHash.IsEqual(block.Sha()) {
return AssertError(fmt.Sprintf("dbIndexDisconnectBlock must "+
"be called with the block at the current index tip "+
"(%s, tip %s, block %s)", indexer.Name(),
curTipHash, block.Sha()))
}
// Notify the indexer with the disconnected block so it can remove all
// of the appropriate entries.
if err := indexer.DisconnectBlock(dbTx, block, view); err != nil {
return err
}
// Update the current index tip.
prevHash := &block.MsgBlock().Header.PrevBlock
return dbPutIndexerTip(dbTx, idxKey, prevHash, block.Height()-1)
}
// DisconnectBlock is invoked by the index manager when a block has been
// disconnected from the main chain. This indexer removes the
// hash-to-transaction mapping for every transaction in the block.
//
// This is part of the Indexer interface.
func (idx *TxIndex) DisconnectBlock(dbTx database.Tx, block *btcutil.Block, view *blockchain.UtxoViewpoint) error {
// Remove all of the transactions in the block from the index.
if err := dbRemoveTxIndexEntries(dbTx, block); err != nil {
return err
}
// Remove the block ID index entry for the block being disconnected and
// decrement the current internal block ID to account for it.
if err := dbRemoveBlockIDIndexEntry(dbTx, block.Hash()); err != nil {
return err
}
idx.curBlockID--
return nil
}
// fetchInputUtxos loads utxo details about the input transactions referenced
// by the transactions in the given block into the view from the database as
// needed. In particular, referenced entries that are earlier in the block are
// added to the view and entries that are already in the view are not modified.
func (view *UtxoViewpoint) fetchInputUtxos(db database.DB, block *btcutil.Block) error {
// Build a map of in-flight transactions because some of the inputs in
// this block could be referencing other transactions earlier in this
// block which are not yet in the chain.
txInFlight := map[wire.ShaHash]int{}
transactions := block.Transactions()
for i, tx := range transactions {
txInFlight[*tx.Sha()] = i
}
// Loop through all of the transaction inputs (except for the coinbase
// which has no inputs) collecting them into sets of what is needed and
// what is already known (in-flight).
txNeededSet := make(map[wire.ShaHash]struct{})
for i, tx := range transactions[1:] {
for _, txIn := range tx.MsgTx().TxIn {
// It is acceptable for a transaction input to reference
// the output of another transaction in this block only
// if the referenced transaction comes before the
// current one in this block. Add the outputs of the
// referenced transaction as available utxos when this
// is the case. Otherwise, the utxo details are still
// needed.
//
// NOTE: The >= is correct here because i is one less
// than the actual position of the transaction within
// the block due to skipping the coinbase.
originHash := &txIn.PreviousOutPoint.Hash
if inFlightIndex, ok := txInFlight[*originHash]; ok &&
i >= inFlightIndex {
originTx := transactions[inFlightIndex]
view.AddTxOuts(originTx, block.Height())
continue
}
// Don't request entries that are already in the view
// from the database.
if _, ok := view.entries[*originHash]; ok {
continue
}
txNeededSet[*originHash] = struct{}{}
}
}
// Request the input utxos from the database.
return view.fetchUtxosMain(db, txNeededSet)
}
// CheckConnectBlock performs several checks to confirm connecting the passed
// block to the main chain does not violate any rules. An example of some of
// the checks performed are ensuring connecting the block would not cause any
// duplicate transaction hashes for old transactions that aren't already fully
// spent, double spends, exceeding the maximum allowed signature operations
// per block, invalid values in relation to the expected block subsidy, or fail
// transaction script validation.
//
// This function is safe for concurrent access.
func (b *BlockChain) CheckConnectBlock(block *btcutil.Block) error {
b.chainLock.Lock()
defer b.chainLock.Unlock()
prevNode := b.bestNode
newNode := newBlockNode(&block.MsgBlock().Header, block.Hash(),
prevNode.height+1)
newNode.parent = prevNode
newNode.workSum.Add(prevNode.workSum, newNode.workSum)
// Leave the spent txouts entry nil in the state since the information
// is not needed and thus extra work can be avoided.
view := NewUtxoViewpoint()
view.SetBestHash(prevNode.hash)
return b.checkConnectBlock(newNode, block, view, nil)
}
// addOrphanBlock adds the passed block (which is already determined to be
// an orphan prior calling this function) to the orphan pool. It lazily cleans
// up any expired blocks so a separate cleanup poller doesn't need to be run.
// It also imposes a maximum limit on the number of outstanding orphan
// blocks and will remove the oldest received orphan block if the limit is
// exceeded.
func (b *BlockChain) addOrphanBlock(block *btcutil.Block) {
// Remove expired orphan blocks.
for _, oBlock := range b.orphans {
if time.Now().After(oBlock.expiration) {
b.removeOrphanBlock(oBlock)
continue
}
// Update the oldest orphan block pointer so it can be discarded
// in case the orphan pool fills up.
if b.oldestOrphan == nil || oBlock.expiration.Before(b.oldestOrphan.expiration) {
b.oldestOrphan = oBlock
}
}
// Limit orphan blocks to prevent memory exhaustion.
if len(b.orphans)+1 > maxOrphanBlocks {
// Remove the oldest orphan to make room for the new one.
b.removeOrphanBlock(b.oldestOrphan)
b.oldestOrphan = nil
}
// Get the block sha. It is safe to ignore the error here since any
// errors would've been caught prior to calling this function.
blockSha, _ := block.Sha()
// Protect concurrent access. This is intentionally done here instead
// of near the top since removeOrphanBlock does its own locking and
// the range iterator is not invalidated by removing map entries.
b.orphanLock.Lock()
defer b.orphanLock.Unlock()
// Insert the block into the orphan map with an expiration time
// 1 hour from now.
expiration := time.Now().Add(time.Hour)
oBlock := &orphanBlock{
block: block,
expiration: expiration,
}
b.orphans[*blockSha] = oBlock
// Add to previous hash lookup index for faster dependency lookups.
prevHash := &block.MsgBlock().Header.PrevBlock
b.prevOrphans[*prevHash] = append(b.prevOrphans[*prevHash], oBlock)
return
}
// ConnectBlock is invoked by the index manager when a new block has been
// connected to the main chain. This indexer adds a hash-to-transaction mapping
// for every transaction in the passed block.
//
// This is part of the Indexer interface.
func (idx *TxIndex) ConnectBlock(dbTx database.Tx, block *btcutil.Block, view *blockchain.UtxoViewpoint) error {
// Increment the internal block ID to use for the block being connected
// and add all of the transactions in the block to the index.
newBlockID := idx.curBlockID + 1
if err := dbAddTxIndexEntries(dbTx, block, newBlockID); err != nil {
return err
}
// Add the new block ID index entry for the block being connected and
// update the current internal block ID accordingly.
err := dbPutBlockIDIndexEntry(dbTx, block.Hash(), newBlockID)
if err != nil {
return err
}
idx.curBlockID = newBlockID
return nil
}
// indexBlockAddrs returns a populated index of the all the transactions in the
// passed block based on the addresses involved in each transaction.
func (a *addrIndexer) indexBlockAddrs(blk *btcutil.Block) (database.BlockAddrIndex, error) {
addrIndex := make(database.BlockAddrIndex)
txLocs, err := blk.TxLoc()
if err != nil {
return nil, err
}
for txIdx, tx := range blk.Transactions() {
// Tx's offset and length in the block.
locInBlock := &txLocs[txIdx]
// Coinbases don't have any inputs.
if !blockchain.IsCoinBase(tx) {
// Index the SPK's of each input's previous outpoint
// transaction.
for _, txIn := range tx.MsgTx().TxIn {
// Lookup and fetch the referenced output's tx.
prevOut := txIn.PreviousOutPoint
txList, err := a.server.db.FetchTxBySha(&prevOut.Hash)
if len(txList) == 0 {
return nil, fmt.Errorf("transaction %v not found",
prevOut.Hash)
}
if err != nil {
adxrLog.Errorf("Error fetching tx %v: %v",
prevOut.Hash, err)
return nil, err
}
prevOutTx := txList[len(txList)-1]
inputOutPoint := prevOutTx.Tx.TxOut[prevOut.Index]
indexScriptPubKey(addrIndex, inputOutPoint.PkScript, locInBlock)
}
}
for _, txOut := range tx.MsgTx().TxOut {
indexScriptPubKey(addrIndex, txOut.PkScript, locInBlock)
}
}
return addrIndex, nil
}
// LogBlockHeight logs a new block height as an information message to show
// progress to the user. In order to prevent spam, it limits logging to one
// message every 10 seconds with duration and totals included.
func (b *blockProgressLogger) LogBlockHeight(block *btcutil.Block) {
b.Lock()
defer b.Unlock()
b.receivedLogBlocks++
b.receivedLogTx += int64(len(block.MsgBlock().Transactions))
now := time.Now()
duration := now.Sub(b.lastBlockLogTime)
if duration < time.Second*10 {
return
}
// Truncate the duration to 10s of milliseconds.
durationMillis := int64(duration / time.Millisecond)
tDuration := 10 * time.Millisecond * time.Duration(durationMillis/10)
// Log information about new block height.
blockStr := "blocks"
if b.receivedLogBlocks == 1 {
blockStr = "block"
}
txStr := "transactions"
if b.receivedLogTx == 1 {
txStr = "transaction"
}
b.subsystemLogger.Infof("%s %d %s in the last %s (%d %s, height %d, %s)",
b.progressAction, b.receivedLogBlocks, blockStr, tDuration, b.receivedLogTx,
txStr, block.Height(), block.MsgBlock().Header.Timestamp)
b.receivedLogBlocks = 0
b.receivedLogTx = 0
b.lastBlockLogTime = now
}
// dbAddTxIndexEntries uses an existing database transaction to add a
// transaction index entry for every transaction in the passed block.
func dbAddTxIndexEntries(dbTx database.Tx, block *btcutil.Block, blockID uint32) error {
// The offset and length of the transactions within the serialized
// block.
txLocs, err := block.TxLoc()
if err != nil {
return err
}
// As an optimization, allocate a single slice big enough to hold all
// of the serialized transaction index entries for the block and
// serialize them directly into the slice. Then, pass the appropriate
// subslice to the database to be written. This approach significantly
// cuts down on the number of required allocations.
offset := 0
serializedValues := make([]byte, len(block.Transactions())*txEntrySize)
for i, tx := range block.Transactions() {
putTxIndexEntry(serializedValues[offset:], blockID, txLocs[i])
endOffset := offset + txEntrySize
err := dbPutTxIndexEntry(dbTx, tx.Hash(),
serializedValues[offset:endOffset:endOffset])
if err != nil {
return err
}
offset += txEntrySize
}
return nil
}
// checkBIP0030 ensures blocks do not contain duplicate transactions which
// 'overwrite' older transactions that are not fully spent. This prevents an
// attack where a coinbase and all of its dependent transactions could be
// duplicated to effectively revert the overwritten transactions to a single
// confirmation thereby making them vulnerable to a double spend.
//
// For more details, see https://en.bitcoin.it/wiki/BIP_0030 and
// http://r6.ca/blog/20120206T005236Z.html.
func (b *BlockChain) checkBIP0030(node *blockNode, block *btcutil.Block) error {
// Attempt to fetch duplicate transactions for all of the transactions
// in this block from the point of view of the parent node.
fetchSet := make(map[wire.ShaHash]struct{})
for _, tx := range block.Transactions() {
fetchSet[*tx.Sha()] = struct{}{}
}
txResults, err := b.fetchTxStore(node, fetchSet)
if err != nil {
return err
}
// Examine the resulting data about the requested transactions.
for _, txD := range txResults {
switch txD.Err {
// A duplicate transaction was not found. This is the most
// common case.
case database.ErrTxShaMissing:
continue
// A duplicate transaction was found. This is only allowed if
// the duplicate transaction is fully spent.
case nil:
if !isTransactionSpent(txD) {
str := fmt.Sprintf("tried to overwrite "+
"transaction %v at block height %d "+
"that is not fully spent", txD.Hash,
txD.BlockHeight)
return ruleError(ErrOverwriteTx, str)
}
// Some other unexpected error occurred. Return it now.
default:
return txD.Err
}
}
return nil
}
// createBlock creates a new block building from the previous block.
func createBlock(prevBlock *btcutil.Block, inclusionTxs []*btcutil.Tx,
blockVersion int32, blockTime time.Time,
miningAddr btcutil.Address, net *chaincfg.Params) (*btcutil.Block, error) {
prevHash := prevBlock.Hash()
blockHeight := prevBlock.Height() + 1
// If a target block time was specified, then use that as the header's
// timestamp. Otherwise, add one second to the previous block unless
// it's the genesis block in which case use the current time.
var ts time.Time
switch {
case !blockTime.IsZero():
ts = blockTime
default:
ts = prevBlock.MsgBlock().Header.Timestamp.Add(time.Second)
}
extraNonce := uint64(0)
coinbaseScript, err := standardCoinbaseScript(blockHeight, extraNonce)
if err != nil {
return nil, err
}
coinbaseTx, err := createCoinbaseTx(coinbaseScript, blockHeight,
miningAddr, net)
if err != nil {
return nil, err
}
// Create a new block ready to be solved.
blockTxns := []*btcutil.Tx{coinbaseTx}
if inclusionTxs != nil {
blockTxns = append(blockTxns, inclusionTxs...)
}
merkles := blockchain.BuildMerkleTreeStore(blockTxns)
var block wire.MsgBlock
block.Header = wire.BlockHeader{
Version: blockVersion,
PrevBlock: *prevHash,
MerkleRoot: *merkles[len(merkles)-1],
Timestamp: ts,
Bits: net.PowLimitBits,
}
for _, tx := range blockTxns {
if err := block.AddTransaction(tx.MsgTx()); err != nil {
return nil, err
}
}
found := solveBlock(&block.Header, net.PowLimit)
if !found {
return nil, errors.New("Unable to solve block")
}
utilBlock := btcutil.NewBlock(&block)
utilBlock.SetHeight(blockHeight)
return utilBlock, nil
}
// maybeAcceptBlock potentially accepts a block into the block chain and, if
// accepted, returns whether or not it is on the main chain. It performs
// several validation checks which depend on its position within the block chain
// before adding it. The block is expected to have already gone through
// ProcessBlock before calling this function with it.
//
// The flags modify the behavior of this function as follows:
// - BFDryRun: The memory chain index will not be pruned and no accept
// notification will be sent since the block is not being accepted.
//
// The flags are also passed to checkBlockContext and connectBestChain. See
// their documentation for how the flags modify their behavior.
//
// This function MUST be called with the chain state lock held (for writes).
func (b *BlockChain) maybeAcceptBlock(block *btcutil.Block, flags BehaviorFlags) (bool, error) {
dryRun := flags&BFDryRun == BFDryRun
// Get a block node for the block previous to this one. Will be nil
// if this is the genesis block.
prevNode, err := b.getPrevNodeFromBlock(block)
if err != nil {
log.Errorf("getPrevNodeFromBlock: %v", err)
return false, err
}
// The height of this block is one more than the referenced previous
// block.
blockHeight := int32(0)
if prevNode != nil {
blockHeight = prevNode.height + 1
}
block.SetHeight(blockHeight)
// The block must pass all of the validation rules which depend on the
// position of the block within the block chain.
err = b.checkBlockContext(block, prevNode, flags)
if err != nil {
return false, err
}
// Create a new block node for the block and add it to the in-memory
// block chain (could be either a side chain or the main chain).
blockHeader := &block.MsgBlock().Header
newNode := newBlockNode(blockHeader, block.Hash(), blockHeight)
if prevNode != nil {
newNode.parent = prevNode
newNode.height = blockHeight
newNode.workSum.Add(prevNode.workSum, newNode.workSum)
}
// Connect the passed block to the chain while respecting proper chain
// selection according to the chain with the most proof of work. This
// also handles validation of the transaction scripts.
isMainChain, err := b.connectBestChain(newNode, block, flags)
if err != nil {
return false, err
}
// Notify the caller that the new block was accepted into the block
// chain. The caller would typically want to react by relaying the
// inventory to other peers.
if !dryRun {
b.chainLock.Unlock()
b.sendNotification(NTBlockAccepted, block)
b.chainLock.Lock()
}
return isMainChain, nil
}
// CheckConnectBlock performs several checks to confirm connecting the passed
// block to the main chain does not violate any rules. An example of some of
// the checks performed are ensuring connecting the block would not cause any
// duplicate transaction hashes for old transactions that aren't already fully
// spent, double spends, exceeding the maximum allowed signature operations
// per block, invalid values in relation to the expected block subsidy, or fail
// transaction script validation.
//
// This function is NOT safe for concurrent access.
func (b *BlockChain) CheckConnectBlock(block *btcutil.Block) error {
prevNode := b.bestChain
newNode := newBlockNode(&block.MsgBlock().Header, block.Sha(),
block.Height())
if prevNode != nil {
newNode.parent = prevNode
newNode.workSum.Add(prevNode.workSum, newNode.workSum)
}
return b.checkConnectBlock(newNode, block)
}
// connectTransactions updates the view by adding all new utxos created by all
// of the transactions in the passed block, marking all utxos the transactions
// spend as spent, and setting the best hash for the view to the passed block.
// In addition, when the 'stxos' argument is not nil, it will be updated to
// append an entry for each spent txout.
func (view *UtxoViewpoint) connectTransactions(block *btcutil.Block, stxos *[]spentTxOut) error {
for _, tx := range block.Transactions() {
err := view.connectTransaction(tx, block.Height(), stxos)
if err != nil {
return err
}
}
// Update the best hash for view to include this block since all of its
// transactions have been connected.
view.SetBestHash(block.Sha())
return nil
}
// checkBlockContext peforms several validation checks on the block which depend
// on its position within the block chain.
//
// The flags modify the behavior of this function as follows:
// - BFFastAdd: The transaction are not checked to see if they are finalized
// and the somewhat expensive BIP0034 validation is not performed.
//
// The flags are also passed to checkBlockHeaderContext. See its documentation
// for how the flags modify its behavior.
//
// This function MUST be called with the chain state lock held (for writes).
func (b *BlockChain) checkBlockContext(block *btcutil.Block, prevNode *blockNode, flags BehaviorFlags) error {
// The genesis block is valid by definition.
if prevNode == nil {
return nil
}
// Perform all block header related validation checks.
header := &block.MsgBlock().Header
err := b.checkBlockHeaderContext(header, prevNode, flags)
if err != nil {
return err
}
fastAdd := flags&BFFastAdd == BFFastAdd
if !fastAdd {
// The height of this block is one more than the referenced
// previous block.
blockHeight := prevNode.height + 1
// Ensure all transactions in the block are finalized.
for _, tx := range block.Transactions() {
if !IsFinalizedTransaction(tx, blockHeight,
header.Timestamp) {
str := fmt.Sprintf("block contains unfinalized "+
"transaction %v", tx.Hash())
return ruleError(ErrUnfinalizedTx, str)
}
}
// Ensure coinbase starts with serialized block heights for
// blocks whose version is the serializedHeightVersion or newer
// once a majority of the network has upgraded. This is part of
// BIP0034.
if ShouldHaveSerializedBlockHeight(header) &&
b.isMajorityVersion(serializedHeightVersion, prevNode,
b.chainParams.BlockEnforceNumRequired) {
coinbaseTx := block.Transactions()[0]
err := checkSerializedHeight(coinbaseTx, blockHeight)
if err != nil {
return err
}
}
}
return nil
}
// dbIndexConnectBlock adds all of the index entries associated with the
// given block using the provided indexer and updates the tip of the indexer
// accordingly. An error will be returned if the current tip for the indexer is
// not the previous block for the passed block.
func dbIndexConnectBlock(dbTx database.Tx, indexer Indexer, block *btcutil.Block, view *blockchain.UtxoViewpoint) error {
// Assert that the block being connected properly connects to the
// current tip of the index.
idxKey := indexer.Key()
curTipHash, _, err := dbFetchIndexerTip(dbTx, idxKey)
if err != nil {
return err
}
if !curTipHash.IsEqual(&block.MsgBlock().Header.PrevBlock) {
return AssertError(fmt.Sprintf("dbIndexConnectBlock must be "+
"called with a block that extends the current index "+
"tip (%s, tip %s, block %s)", indexer.Name(),
curTipHash, block.Sha()))
}
// Notify the indexer with the connected block so it can index it.
if err := indexer.ConnectBlock(dbTx, block, view); err != nil {
return err
}
// Update the current index tip.
return dbPutIndexerTip(dbTx, idxKey, block.Sha(), block.Height())
}
// submitBlock submits the passed block to network after ensuring it passes all
// of the consensus validation rules.
func (m *CPUMiner) submitBlock(block *btcutil.Block) bool {
m.submitBlockLock.Lock()
defer m.submitBlockLock.Unlock()
// Ensure the block is not stale since a new block could have shown up
// while the solution was being found. Typically that condition is
// detected and all work on the stale block is halted to start work on
// a new block, but the check only happens periodically, so it is
// possible a block was found and submitted in between.
latestHash, _ := m.server.blockManager.chainState.Best()
msgBlock := block.MsgBlock()
if !msgBlock.Header.PrevBlock.IsEqual(latestHash) {
minrLog.Debugf("Block submitted via CPU miner with previous "+
"block %s is stale", msgBlock.Header.PrevBlock)
return false
}
// Process this block using the same rules as blocks coming from other
// nodes. This will in turn relay it to the network like normal.
isOrphan, err := m.server.blockManager.ProcessBlock(block, blockchain.BFNone)
if err != nil {
// Anything other than a rule violation is an unexpected error,
// so log that error as an internal error.
if _, ok := err.(blockchain.RuleError); !ok {
minrLog.Errorf("Unexpected error while processing "+
"block submitted via CPU miner: %v", err)
return false
}
minrLog.Debugf("Block submitted via CPU miner rejected: %v", err)
return false
}
if isOrphan {
minrLog.Debugf("Block submitted via CPU miner is an orphan")
return false
}
// The block was accepted.
blockSha, _ := block.Sha()
coinbaseTx := block.MsgBlock().Transactions[0].TxOut[0]
minrLog.Infof("Block submitted via CPU miner accepted (hash %s, "+
"amount %v)", blockSha, btcutil.Amount(coinbaseTx.Value))
return true
}
