// 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
}
// NotifyBlockConnected creates and marshalls a JSON message to notify
// of a new block connected to the main chain. The notification is sent
// to each connected wallet.
func (s *rpcServer) NotifyBlockConnected(block *btcutil.Block) {
hash, err := block.Sha()
if err != nil {
rpcsLog.Error("Bad block; connected block notification dropped.")
return
}
// TODO: remove int32 type conversion.
ntfn := btcws.NewBlockConnectedNtfn(hash.String(),
int32(block.Height()))
mntfn, _ := json.Marshal(ntfn)
s.ws.walletNotificationMaster <- mntfn
// Inform any interested parties about txs mined in this block.
s.ws.Lock()
for _, tx := range block.Transactions() {
if clist, ok := s.ws.minedTxNotifications[*tx.Sha()]; ok {
var enext *list.Element
for e := clist.Front(); e != nil; e = enext {
enext = e.Next()
c := e.Value.(walletChan)
// TODO: remove int32 type conversion after
// the int64 -> int32 switch is made.
ntfn := btcws.NewTxMinedNtfn(tx.Sha().String(),
hash.String(), int32(block.Height()),
block.MsgBlock().Header.Timestamp.Unix(),
tx.Index())
mntfn, _ := json.Marshal(ntfn)
c <- mntfn
s.ws.removeMinedTxRequest(c, tx.Sha())
}
}
}
s.ws.Unlock()
}
// 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 = btcdb.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
}
// NotifyBlockTXs creates and marshals a JSON message to notify wallets
// of new transactions (with both spent and unspent outputs) for a watched
// address.
func (s *rpcServer) NotifyBlockTXs(db btcdb.Db, block *btcutil.Block) {
// Build a map of in-flight transactions to see if any of the inputs in
// this block are referencing other transactions earlier in this block.
txInFlight := map[btcwire.ShaHash]int{}
transactions := block.Transactions()
spent := make([][]bool, len(transactions))
for i, tx := range transactions {
spent[i] = make([]bool, len(tx.MsgTx().TxOut))
txInFlight[*tx.Sha()] = i
}
// The newBlockNotifyCheckTxOut current needs spent data. This can
// this can ultimately be optimized out by making sure the notifications
// are in order. For now, just create the spent data.
for i, tx := range transactions[1:] {
for _, txIn := range tx.MsgTx().TxIn {
originHash := &txIn.PreviousOutpoint.Hash
if inFlightIndex, ok := txInFlight[*originHash]; ok &&
i >= inFlightIndex {
prevIndex := txIn.PreviousOutpoint.Index
spent[inFlightIndex][prevIndex] = true
}
}
}
for i, tx := range transactions {
go s.newBlockNotifyCheckTxIn(tx)
go s.newBlockNotifyCheckTxOut(block, tx, spent[i])
}
}
// DropAfterBlockBySha will remove any blocks from the database after
// the given block.
func (db *LevelDb) DropAfterBlockBySha(sha *btcwire.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))
}
db.nextBlock = keepidx + 1
return nil
}
// NewMerkleBlock returns a new *btcwire.MsgMerkleBlock and an array of the matched
// transaction hashes based on the passed block and filter.
func NewMerkleBlock(block *btcutil.Block, filter *Filter) (*btcwire.MsgMerkleBlock, []*btcwire.ShaHash) {
numTx := uint32(len(block.Transactions()))
mBlock := merkleBlock{
numTx: numTx,
allHashes: make([]*btcwire.ShaHash, 0, numTx),
matchedBits: make([]byte, 0, numTx),
}
// Find and keep track of any transactions that match the filter.
var matchedHashes []*btcwire.ShaHash
for _, tx := range block.Transactions() {
if filter.MatchTxAndUpdate(tx) {
mBlock.matchedBits = append(mBlock.matchedBits, 0x01)
matchedHashes = append(matchedHashes, tx.Sha())
} else {
mBlock.matchedBits = append(mBlock.matchedBits, 0x00)
}
mBlock.allHashes = append(mBlock.allHashes, tx.Sha())
}
// Calculate the number of merkle branches (height) in the tree.
height := uint32(0)
for mBlock.calcTreeWidth(height) > 1 {
height++
}
// Build the depth-first partial merkle tree.
mBlock.traverseAndBuild(height, 0)
// Create and return the merkle block.
msgMerkleBlock := btcwire.MsgMerkleBlock{
Header: block.MsgBlock().Header,
Transactions: uint32(mBlock.numTx),
Hashes: make([]*btcwire.ShaHash, 0, len(mBlock.finalHashes)),
Flags: make([]byte, (len(mBlock.bits)+7)/8),
}
for _, sha := range mBlock.finalHashes {
msgMerkleBlock.AddTxHash(sha)
}
for i := uint32(0); i < uint32(len(mBlock.bits)); i++ {
msgMerkleBlock.Flags[i/8] |= mBlock.bits[i] << (i % 8)
}
return &msgMerkleBlock, matchedHashes
}
func MakeBlock(block *btcutil.Block, previous *Block) *Block {
transactions := make([]ads.ADS, 0)
for _, transaction := range block.Transactions() {
t := &Transaction{
MsgTx: *transaction.MsgTx(),
}
t.SetCachedHash(sha.Hash(*transaction.Sha()))
transactions = append(transactions, t)
}
b := &Block{
Header: block.MsgBlock().Header,
Previous: previous,
Transactions: transactions,
}
hash, _ := block.Sha()
b.SetCachedHash(sha.Hash(*hash))
return b
}
// 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[btcwire.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 btcdb.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
}
// checkBlockScripts executes and validates the scripts for all transactions in
// the passed block.
func checkBlockScripts(block *btcutil.Block, txStore TxStore) error {
// Setup the script validation flags. Blocks created after the BIP0016
// activation time need to have the pay-to-script-hash checks enabled.
var flags btcscript.ScriptFlags
if block.MsgBlock().Header.Timestamp.After(btcscript.Bip16Activation) {
flags |= btcscript.ScriptBip16
}
// 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(txStore, flags)
if err := validator.Validate(txValItems); err != nil {
return err
}
return nil
}
func GetExodusTransactions(block *btcutil.Block) []*btcutil.Tx {
var txs []*btcutil.Tx
for _, tx := range block.Transactions() {
mtx := tx.MsgTx()
for _, txOut := range mtx.TxOut {
// Extract the address from the script pub key
addrs, _ := GetAddrs(txOut.PkScript)
// Check each output address and if there's an address going to the exodus address
// we add it to tx slice
for _, addr := range addrs {
if addr.Addr == ExodusAddress {
txs = append(txs, tx)
// Continue, we don't care if there are more exodus addresses
continue
}
}
}
}
return txs
}
// BuildMerkleTreeStore creates a merkle tree from block, stores it using a
// linear array, and returns a slice of the backing array. A linear array was
// chosen as opposed to an actual tree structure since it uses about half as
// much memory. The following describes a merkle tree and how it is stored in
// a linear array.
//
// A merkle tree is a tree in which every non-leaf node is the hash of its
// children nodes. A diagram depicting how this works for bitcoin transactions
// where h(x) is a double sha256 follows:
//
// root = h1234 = h(h12 + h34)
// / \
// h12 = h(h1 + h2) h34 = h(h3 + h4)
// / \ / \
// h1 = h(tx1) h2 = h(tx2) h3 = h(tx3) h4 = h(tx4)
//
// The above stored as a linear array is as follows:
//
// [h1 h2 h3 h4 h12 h34 root]
//
// As the above shows, the merkle root is always the last element in the array.
//
// The number of inputs is not always a power of two which results in a
// balanced tree structure as above. In that case, parent nodes with no
// children are also zero and parent nodes with only a single left node
// are calculated by concatenating the left node with itself before hashing.
// Since this function uses nodes that are pointers to the hashes, empty nodes
// will be nil.
func BuildMerkleTreeStore(block *btcutil.Block) []*btcwire.ShaHash {
// Calculate how many entries are required to hold the binary merkle
// tree as a linear array and create an array of that size.
nextPoT := nextPowerOfTwo(len(block.Transactions()))
arraySize := nextPoT*2 - 1
merkles := make([]*btcwire.ShaHash, arraySize)
// Create the base transaction shas and populate the array with them.
for i, tx := range block.Transactions() {
merkles[i] = tx.Sha()
}
// Start the array offset after the last transaction and adjusted to the
// next power of two.
offset := nextPoT
for i := 0; i < arraySize-1; i += 2 {
switch {
// When there is no left child node, the parent is nil too.
case merkles[i] == nil:
merkles[offset] = nil
// When there is no right child, the parent is generated by
// hashing the concatenation of the left child with itself.
case merkles[i+1] == nil:
newSha := hashMerkleBranches(merkles[i], merkles[i])
merkles[offset] = newSha
// The normal case sets the parent node to the double sha256
// of the concatentation of the left and right children.
default:
newSha := hashMerkleBranches(merkles[i], merkles[i+1])
merkles[offset] = newSha
}
offset++
}
return merkles
}
// rescanBlock rescans all transactions in a single block. This is a
// helper function for handleRescan.
func rescanBlock(s *rpcServer, cmd *btcws.RescanCmd, c handlerChans, blk *btcutil.Block) {
for _, tx := range blk.Transactions() {
var txReply *btcdb.TxListReply
txouts:
for txOutIdx, txout := range tx.MsgTx().TxOut {
_, addrs, _, err := btcscript.ExtractPkScriptAddrs(
txout.PkScript, s.server.btcnet)
if err != nil {
continue txouts
}
for _, addr := range addrs {
encodedAddr := addr.EncodeAddress()
if _, ok := cmd.Addresses[encodedAddr]; !ok {
continue
}
// TODO(jrick): This lookup is expensive and can be avoided
// if the wallet is sent the previous outpoints for all inputs
// of the tx, so any can removed from the utxo set (since
// they are, as of this tx, now spent).
if txReply == nil {
txReplyList, err := s.server.db.FetchTxBySha(tx.Sha())
if err != nil {
rpcsLog.Errorf("Tx Sha %v not found by db", tx.Sha())
continue txouts
}
for i := range txReplyList {
if txReplyList[i].Height == blk.Height() {
txReply = txReplyList[i]
break
}
}
}
// Sha never errors.
blksha, _ := blk.Sha()
ntfn := &btcws.ProcessedTxNtfn{
Receiver: encodedAddr,
Amount: txout.Value,
TxID: tx.Sha().String(),
TxOutIndex: uint32(txOutIdx),
PkScript: hex.EncodeToString(txout.PkScript),
BlockHash: blksha.String(),
BlockHeight: int32(blk.Height()),
BlockIndex: tx.Index(),
BlockTime: blk.MsgBlock().Header.Timestamp.Unix(),
Spent: txReply.TxSpent[txOutIdx],
}
select {
case <-c.disconnected:
return
default:
c.n <- ntfn
}
}
}
}
}
// IsCheckpointCandidate returns whether or not the passed block is a good
// checkpoint candidate.
//
// The factors used to determine a good checkpoint are:
// - The block must be in the main chain
// - The block must be at least 'CheckpointConfirmations' blocks prior to the
// current end of the main chain
// - The timestamps for the blocks before and after the checkpoint must have
// timestamps which are also before and after the checkpoint, respectively
// (due to the median time allowance this is not always the case)
// - The block must not contain any strange transaction such as those with
// nonstandard scripts
func (b *BlockChain) IsCheckpointCandidate(block *btcutil.Block) (bool, error) {
// Checkpoints must be enabled.
if b.noCheckpoints {
return false, fmt.Errorf("checkpoints are disabled")
}
blockHash, err := block.Sha()
if err != nil {
return false, err
}
// A checkpoint must be in the main chain.
if !b.db.ExistsSha(blockHash) {
return false, nil
}
// A checkpoint must be at least CheckpointConfirmations blocks before
// the end of the main chain.
blockHeight := block.Height()
_, mainChainHeight, err := b.db.NewestSha()
if err != nil {
return false, err
}
if blockHeight > (mainChainHeight - CheckpointConfirmations) {
return false, nil
}
// Get the previous block.
prevHash := &block.MsgBlock().Header.PrevBlock
prevBlock, err := b.db.FetchBlockBySha(prevHash)
if err != nil {
return false, err
}
// Get the next block.
nextHash, err := b.db.FetchBlockShaByHeight(blockHeight + 1)
if err != nil {
return false, err
}
nextBlock, err := b.db.FetchBlockBySha(nextHash)
if err != nil {
return false, err
}
// A checkpoint must have timestamps for the block and the blocks on
// either side of it in order (due to the median time allowance this is
// not always the case).
prevTime := prevBlock.MsgBlock().Header.Timestamp
curTime := block.MsgBlock().Header.Timestamp
nextTime := nextBlock.MsgBlock().Header.Timestamp
if prevTime.After(curTime) || nextTime.Before(curTime) {
return false, nil
}
// A checkpoint must have transactions that only contain standard
// scripts.
for _, tx := range block.Transactions() {
if isNonstandardTransaction(tx) {
return false, nil
}
}
return true, nil
}
// NotifyBlockTXs creates and marshals a JSON message to notify wallets
// of new transactions (with both spent and unspent outputs) for a watched
// address.
func (s *rpcServer) NotifyBlockTXs(db btcdb.Db, block *btcutil.Block) {
for _, tx := range block.Transactions() {
s.newBlockNotifyCheckTxIn(tx)
s.NotifyForTxOuts(tx, block)
}
}
// checkBlockSanity performs some preliminary checks on a block to ensure it is
// sane before continuing with block processing. These checks are context free.
//
// The flags do not modify the behavior of this function directly, however they
// are needed to pass along to checkProofOfWork.
func checkBlockSanity(block *btcutil.Block, powLimit *big.Int, flags BehaviorFlags) error {
// A block must have at least one transaction.
msgBlock := block.MsgBlock()
numTx := len(msgBlock.Transactions)
if numTx == 0 {
return ruleError(ErrNoTransactions, "block does not contain "+
"any transactions")
}
// A block must not have more transactions than the max block payload.
if numTx > btcwire.MaxBlockPayload {
str := fmt.Sprintf("block contains too many transactions - "+
"got %d, max %d", numTx, btcwire.MaxBlockPayload)
return ruleError(ErrTooManyTransactions, str)
}
// A block must not exceed the maximum allowed block payload when
// serialized.
serializedSize := msgBlock.SerializeSize()
if serializedSize > btcwire.MaxBlockPayload {
str := fmt.Sprintf("serialized block is too big - got %d, "+
"max %d", serializedSize, btcwire.MaxBlockPayload)
return ruleError(ErrBlockTooBig, str)
}
// Ensure the proof of work bits in the block header is in min/max range
// and the block hash is less than the target value described by the
// bits.
err := checkProofOfWork(block, powLimit, flags)
if err != nil {
return err
}
// A block timestamp must not have a greater precision than one second.
// This check is necessary because Go time.Time values support
// nanosecond precision whereas the consensus rules only apply to
// seconds and it's much nicer to deal with standard Go time values
// instead of converting to seconds everywhere.
header := &block.MsgBlock().Header
if !header.Timestamp.Equal(time.Unix(header.Timestamp.Unix(), 0)) {
str := fmt.Sprintf("block timestamp of %v has a higher "+
"precision than one second", header.Timestamp)
return ruleError(ErrInvalidTime, str)
}
// Ensure the block time is not too far in the future.
maxTimestamp := time.Now().Add(time.Second * MaxTimeOffsetSeconds)
if header.Timestamp.After(maxTimestamp) {
str := fmt.Sprintf("block timestamp of %v is too far in the "+
"future", header.Timestamp)
return ruleError(ErrTimeTooNew, str)
}
// The first transaction in a block must be a coinbase.
transactions := block.Transactions()
if !IsCoinBase(transactions[0]) {
return ruleError(ErrFirstTxNotCoinbase, "first transaction in "+
"block is not a coinbase")
}
// A block must not have more than one coinbase.
for i, tx := range transactions[1:] {
if IsCoinBase(tx) {
str := fmt.Sprintf("block contains second coinbase at "+
"index %d", i)
return ruleError(ErrMultipleCoinbases, str)
}
}
// Do some preliminary checks on each transaction to ensure they are
// sane before continuing.
for _, tx := range transactions {
err := CheckTransactionSanity(tx)
if err != nil {
return err
}
}
// Build merkle tree and ensure the calculated merkle root matches the
// entry in the block header. This also has the effect of caching all
// of the transaction hashes in the block to speed up future hash
// checks. Bitcoind builds the tree here and checks the merkle root
// after the following checks, but there is no reason not to check the
// merkle root matches here.
merkles := BuildMerkleTreeStore(block.Transactions())
calculatedMerkleRoot := merkles[len(merkles)-1]
if !header.MerkleRoot.IsEqual(calculatedMerkleRoot) {
str := fmt.Sprintf("block merkle root is invalid - block "+
"header indicates %v, but calculated value is %v",
header.MerkleRoot, calculatedMerkleRoot)
return ruleError(ErrBadMerkleRoot, str)
}
// Check for duplicate transactions. This check will be fairly quick
// since the transaction hashes are already cached due to building the
// merkle tree above.
existingTxHashes := make(map[btcwire.ShaHash]struct{})
for _, tx := range transactions {
hash := tx.Sha()
if _, exists := existingTxHashes[*hash]; exists {
str := fmt.Sprintf("block contains duplicate "+
"transaction %v", hash)
return ruleError(ErrDuplicateTx, str)
}
existingTxHashes[*hash] = struct{}{}
}
// The number of signature operations must be less than the maximum
// allowed per block.
totalSigOps := 0
for _, tx := range transactions {
// We could potentially overflow the accumulator so check for
// overflow.
lastSigOps := totalSigOps
totalSigOps += CountSigOps(tx)
if totalSigOps < lastSigOps || totalSigOps > MaxSigOpsPerBlock {
str := fmt.Sprintf("block contains too many signature "+
"operations - got %v, max %v", totalSigOps,
MaxSigOpsPerBlock)
return ruleError(ErrTooManySigOps, str)
}
}
return nil
}
// maybeAcceptBlock potentially accepts a block into the memory block 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:
// - BFFastAdd: The somewhat expensive BIP0034 validation is not performed.
// - BFDryRun: The memory chain index will not be pruned and no accept
// notification will be sent since the block is not being accepted.
func (b *BlockChain) maybeAcceptBlock(block *btcutil.Block, flags BehaviorFlags) error {
fastAdd := flags&BFFastAdd == BFFastAdd
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 err
}
// The height of this block is one more than the referenced previous
// block.
blockHeight := int64(0)
if prevNode != nil {
blockHeight = prevNode.height + 1
}
block.SetHeight(blockHeight)
blockHeader := &block.MsgBlock().Header
if !fastAdd {
// Ensure the difficulty specified in the block header matches
// the calculated difficulty based on the previous block and
// difficulty retarget rules.
expectedDifficulty, err := b.calcNextRequiredDifficulty(prevNode,
block.MsgBlock().Header.Timestamp)
if err != nil {
return err
}
blockDifficulty := blockHeader.Bits
if blockDifficulty != expectedDifficulty {
str := "block difficulty of %d is not the expected value of %d"
str = fmt.Sprintf(str, blockDifficulty, expectedDifficulty)
return ruleError(ErrUnexpectedDifficulty, str)
}
// Ensure the timestamp for the block header is after the
// median time of the last several blocks (medianTimeBlocks).
medianTime, err := b.calcPastMedianTime(prevNode)
if err != nil {
log.Errorf("calcPastMedianTime: %v", err)
return err
}
if !blockHeader.Timestamp.After(medianTime) {
str := "block timestamp of %v is not after expected %v"
str = fmt.Sprintf(str, blockHeader.Timestamp,
medianTime)
return ruleError(ErrTimeTooOld, str)
}
// Ensure all transactions in the block are finalized.
for _, tx := range block.Transactions() {
if !IsFinalizedTransaction(tx, blockHeight,
blockHeader.Timestamp) {
str := fmt.Sprintf("block contains "+
"unfinalized transaction %v", tx.Sha())
return ruleError(ErrUnfinalizedTx, str)
}
}
}
// Ensure chain matches up to predetermined checkpoints.
// It's safe to ignore the error on Sha since it's already cached.
blockHash, _ := block.Sha()
if !b.verifyCheckpoint(blockHeight, blockHash) {
str := fmt.Sprintf("block at height %d does not match "+
"checkpoint hash", blockHeight)
return ruleError(ErrBadCheckpoint, str)
}
// Find the previous checkpoint and prevent blocks which fork the main
// chain before it. This prevents storage of new, otherwise valid,
// blocks which build off of old blocks that are likely at a much easier
// difficulty and therefore could be used to waste cache and disk space.
checkpointBlock, err := b.findPreviousCheckpoint()
if err != nil {
return err
}
if checkpointBlock != nil && blockHeight < checkpointBlock.Height() {
str := fmt.Sprintf("block at height %d forks the main chain "+
"before the previous checkpoint at height %d",
blockHeight, checkpointBlock.Height())
return ruleError(ErrForkTooOld, str)
}
if !fastAdd {
// Reject version 1 blocks once a majority of the network has
// upgraded. This is part of BIP0034.
if blockHeader.Version < 2 {
if b.isMajorityVersion(2, prevNode,
b.netParams.BlockV1RejectNumRequired,
b.netParams.BlockV1RejectNumToCheck) {
str := "new blocks with version %d are no " +
"longer valid"
str = fmt.Sprintf(str, blockHeader.Version)
return ruleError(ErrBlockVersionTooOld, 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 blockHeader.Version >= serializedHeightVersion {
if b.isMajorityVersion(serializedHeightVersion,
prevNode,
b.netParams.CoinbaseBlockHeightNumRequired,
b.netParams.CoinbaseBlockHeightNumToCheck) {
expectedHeight := int64(0)
if prevNode != nil {
expectedHeight = prevNode.height + 1
}
coinbaseTx := block.Transactions()[0]
err := checkSerializedHeight(coinbaseTx,
expectedHeight)
if err != nil {
return err
}
}
}
}
// Prune block nodes which are no longer needed before creating
// a new node.
if !dryRun {
err = b.pruneBlockNodes()
if err != nil {
return 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).
newNode := newBlockNode(blockHeader, blockHash, 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.
err = b.connectBestChain(newNode, block, flags)
if err != nil {
return 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.sendNotification(NTBlockAccepted, block)
}
return nil
}
// maybeAcceptBlock potentially accepts a block into the memory block 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 fastAdd argument modifies the behavior of the function by avoiding the
// somewhat expensive operation: BIP34 validation, it also passes the argument
// down to connectBestChain()
func (b *BlockChain) maybeAcceptBlock(block *btcutil.Block, fastAdd bool) error {
// 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 err
}
// The height of this block is one more than the referenced previous
// block.
blockHeight := int64(0)
if prevNode != nil {
blockHeight = prevNode.height + 1
}
block.SetHeight(blockHeight)
blockHeader := &block.MsgBlock().Header
if !fastAdd {
// Ensure the difficulty specified in the block header matches
// the calculated difficulty based on the previous block and
// difficulty retarget rules.
expectedDifficulty, err := b.calcNextRequiredDifficulty(prevNode, block)
if err != nil {
return err
}
blockDifficulty := blockHeader.Bits
if blockDifficulty != expectedDifficulty {
str := "block difficulty of %d is not the expected value of %d"
str = fmt.Sprintf(str, blockDifficulty, expectedDifficulty)
return RuleError(str)
}
// Ensure the timestamp for the block header is after the
// median time of the last several blocks (medianTimeBlocks).
medianTime, err := b.calcPastMedianTime(prevNode)
if err != nil {
log.Errorf("calcPastMedianTime: %v", err)
return err
}
if !blockHeader.Timestamp.After(medianTime) {
str := "block timestamp of %v is not after expected %v"
str = fmt.Sprintf(str, blockHeader.Timestamp,
medianTime)
return RuleError(str)
}
// Ensure all transactions in the block are finalized.
for _, tx := range block.Transactions() {
if !IsFinalizedTransaction(tx, blockHeight,
blockHeader.Timestamp) {
str := fmt.Sprintf("block contains "+
"unfinalized transaction %v", tx.Sha())
return RuleError(str)
}
}
}
// Ensure chain matches up to predetermined checkpoints.
// It's safe to ignore the error on Sha since it's already cached.
blockHash, _ := block.Sha()
if !b.verifyCheckpoint(blockHeight, blockHash) {
// TODO(davec): This should probably be a distinct error type
// (maybe CheckpointError). Since this error shouldn't happen
// unless the peer is connected to a rogue network serving up an
// alternate chain, the caller would likely need to react by
// disconnecting peers and rolling back the chain to the last
// known good point.
str := fmt.Sprintf("block at height %d does not match "+
"checkpoint hash", blockHeight)
return RuleError(str)
}
if !fastAdd {
// Reject version 1 blocks once a majority of the network has
// upgraded.
// Rules:
// 95% (950 / 1000) for main network
// 75% (75 / 100) for the test network
// This is part of BIP_0034.
if blockHeader.Version == 1 {
minRequired := uint64(950)
numToCheck := uint64(1000)
if b.btcnet == btcwire.TestNet3 || b.btcnet ==
btcwire.TestNet {
minRequired = 75
numToCheck = 100
}
if b.isMajorityVersion(2, prevNode, minRequired,
numToCheck) {
str := "new blocks with version %d are no longer valid"
str = fmt.Sprintf(str, blockHeader.Version)
return RuleError(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.
// Rules:
// 75% (750 / 1000) for main network
// 51% (51 / 100) for the test network
// This is part of BIP_0034.
if blockHeader.Version >= serializedHeightVersion {
minRequired := uint64(750)
numToCheck := uint64(1000)
if b.btcnet == btcwire.TestNet3 || b.btcnet ==
btcwire.TestNet {
minRequired = 51
numToCheck = 100
}
if b.isMajorityVersion(serializedHeightVersion,
prevNode, minRequired, numToCheck) {
expectedHeight := int64(0)
if prevNode != nil {
expectedHeight = prevNode.height + 1
}
coinbaseTx := block.Transactions()[0]
err := checkSerializedHeight(coinbaseTx,
expectedHeight)
if err != nil {
return err
}
}
}
}
// Prune block nodes which are no longer needed before creating
// a new node.
err = b.pruneBlockNodes()
if err != nil {
return 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).
newNode := newBlockNode(blockHeader, blockHash, 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.
err = b.connectBestChain(newNode, block, fastAdd)
if err != nil {
return 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.
b.sendNotification(NTBlockAccepted, block)
return nil
}
// InsertBlock inserts raw block and transaction data from a block into the
// database. The first block inserted into the database will be treated as the
// genesis block. Every subsequent block insert requires the referenced parent
// block to already exist. This is part of the btcdb.Db interface
// implementation.
func (db *MemDb) InsertBlock(block *btcutil.Block) (int64, error) {
db.Lock()
defer db.Unlock()
if db.closed {
return 0, ErrDbClosed
}
blockHash, err := block.Sha()
if err != nil {
return 0, err
}
// Reject the insert if the previously reference block does not exist
// except in the case there are no blocks inserted yet where the first
// inserted block is assumed to be a genesis block.
msgBlock := block.MsgBlock()
if _, exists := db.blocksBySha[msgBlock.Header.PrevBlock]; !exists {
if len(db.blocks) > 0 {
return 0, btcdb.ErrPrevShaMissing
}
}
// 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[btcwire.ShaHash]int{}
transactions := block.Transactions()
for i, tx := range transactions {
txInFlight[*tx.Sha()] = i
}
// Loop through all transactions and inputs to ensure there are no error
// conditions that would prevent them from be inserted into the db.
// Although these checks could could be done in the loop below, checking
// for error conditions up front means the code below doesn't have to
// deal with rollback on errors.
newHeight := int64(len(db.blocks))
for i, tx := range transactions {
// Two old blocks contain duplicate transactions due to being
// mined by faulty miners and accepted by the origin Satoshi
// client. Rules have since been added to the ensure this
// problem can no longer happen, but the two duplicate
// transactions which were originally accepted are forever in
// the block chain history and must be dealth with specially.
// http://blockexplorer.com/b/91842
// http://blockexplorer.com/b/91880
if newHeight == 91842 && tx.Sha().IsEqual(dupTxHash91842) {
continue
}
if newHeight == 91880 && tx.Sha().IsEqual(dupTxHash91880) {
continue
}
for _, txIn := range tx.MsgTx().TxIn {
if isCoinbaseInput(txIn) {
continue
}
// 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.
prevOut := &txIn.PreviousOutPoint
if inFlightIndex, ok := txInFlight[prevOut.Hash]; ok {
if i <= inFlightIndex {
log.Warnf("InsertBlock: requested hash "+
" of %s does not exist in-flight",
tx.Sha())
return 0, btcdb.ErrTxShaMissing
}
} else {
originTxns, exists := db.txns[prevOut.Hash]
if !exists {
log.Warnf("InsertBlock: requested hash "+
"of %s by %s does not exist",
prevOut.Hash, tx.Sha())
return 0, btcdb.ErrTxShaMissing
}
originTxD := originTxns[len(originTxns)-1]
if prevOut.Index > uint32(len(originTxD.spentBuf)) {
log.Warnf("InsertBlock: requested hash "+
"of %s with index %d does not "+
"exist", tx.Sha(), prevOut.Index)
return 0, btcdb.ErrTxShaMissing
}
}
}
// Prevent duplicate transactions in the same block.
if inFlightIndex, exists := txInFlight[*tx.Sha()]; exists &&
inFlightIndex < i {
log.Warnf("Block contains duplicate transaction %s",
tx.Sha())
return 0, btcdb.ErrDuplicateSha
}
// Prevent duplicate transactions unless the old one is fully
// spent.
if txns, exists := db.txns[*tx.Sha()]; exists {
txD := txns[len(txns)-1]
if !isFullySpent(txD) {
log.Warnf("Attempt to insert duplicate "+
"transaction %s", tx.Sha())
return 0, btcdb.ErrDuplicateSha
}
}
}
db.blocks = append(db.blocks, msgBlock)
db.blocksBySha[*blockHash] = newHeight
// Insert information about eacj transaction and spend all of the
// outputs referenced by the inputs to the transactions.
for i, tx := range block.Transactions() {
// Insert the transaction data.
txD := tTxInsertData{
blockHeight: newHeight,
offset: i,
spentBuf: make([]bool, len(tx.MsgTx().TxOut)),
}
db.txns[*tx.Sha()] = append(db.txns[*tx.Sha()], &txD)
// Spend all of the inputs.
for _, txIn := range tx.MsgTx().TxIn {
// Coinbase transaction has no inputs.
if isCoinbaseInput(txIn) {
continue
}
// Already checked for existing and valid ranges above.
prevOut := &txIn.PreviousOutPoint
originTxns := db.txns[prevOut.Hash]
originTxD := originTxns[len(originTxns)-1]
originTxD.spentBuf[prevOut.Index] = true
}
}
return newHeight, nil
}
// CheckBlockSanity performs some preliminary checks on a block to ensure it is
// sane before continuing with block processing. These checks are context free.
func CheckBlockSanity(block *btcutil.Block, powLimit *big.Int) error {
// NOTE: bitcoind does size limits checking here, but the size limits
// have already been checked by btcwire for incoming blocks. Also,
// btcwire checks the size limits on send too, so there is no need
// to double check it here.
// Ensure the proof of work bits in the block header is in min/max range
// and the block hash is less than the target value described by the
// bits.
err := checkProofOfWork(block, powLimit)
if err != nil {
return err
}
// Ensure the block time is not more than 2 hours in the future.
header := &block.MsgBlock().Header
if header.Timestamp.After(time.Now().Add(time.Hour * 2)) {
str := fmt.Sprintf("block timestamp of %v is too far in the "+
"future", header.Timestamp)
return RuleError(str)
}
// A block must have at least one transaction.
transactions := block.Transactions()
if len(transactions) == 0 {
return RuleError("block does not contain any transactions")
}
// The first transaction in a block must be a coinbase.
if !IsCoinBase(transactions[0]) {
return RuleError("first transaction in block is not a coinbase")
}
// A block must not have more than one coinbase.
for i, tx := range transactions[1:] {
if IsCoinBase(tx) {
str := fmt.Sprintf("block contains second coinbase at "+
"index %d", i)
return RuleError(str)
}
}
// Do some preliminary checks on each transaction to ensure they are
// sane before continuing.
for _, tx := range transactions {
err := CheckTransactionSanity(tx)
if err != nil {
return err
}
}
// Build merkle tree and ensure the calculated merkle root matches the
// entry in the block header. This also has the effect of caching all
// of the transaction hashes in the block to speed up future hash
// checks. Bitcoind builds the tree here and checks the merkle root
// after the following checks, but there is no reason not to check the
// merkle root matches here.
merkles := BuildMerkleTreeStore(block)
calculatedMerkleRoot := merkles[len(merkles)-1]
if !header.MerkleRoot.IsEqual(calculatedMerkleRoot) {
str := fmt.Sprintf("block merkle root is invalid - block "+
"header indicates %v, but calculated value is %v",
header.MerkleRoot, calculatedMerkleRoot)
return RuleError(str)
}
// Check for duplicate transactions. This check will be fairly quick
// since the transaction hashes are already cached due to building the
// merkle tree above.
existingTxHashes := make(map[btcwire.ShaHash]bool)
for _, tx := range transactions {
hash := tx.Sha()
if _, exists := existingTxHashes[*hash]; exists {
str := fmt.Sprintf("block contains duplicate "+
"transaction %v", hash)
return RuleError(str)
}
existingTxHashes[*hash] = true
}
// The number of signature operations must be less than the maximum
// allowed per block.
totalSigOps := 0
for _, tx := range transactions {
// We could potentially overflow the accumulator so check for
// overflow.
lastSigOps := totalSigOps
totalSigOps += countSigOps(tx)
if totalSigOps < lastSigOps || totalSigOps > maxSigOpsPerBlock {
str := fmt.Sprintf("block contains too many signature "+
"operations - got %v, max %v", totalSigOps,
maxSigOpsPerBlock)
return RuleError(str)
}
}
return nil
}
// checkConnectBlock performs several checks to confirm connecting the passed
// block to the main chain (including whatever reorganization might be necessary
// to get this node to the main chain) does not violate any rules.
func (b *BlockChain) checkConnectBlock(node *blockNode, block *btcutil.Block) error {
// If the side chain blocks end up in the database, a call to
// checkBlockSanity should be done here in case a previous version
// allowed a block that is no longer valid. However, since the
// implementation only currently uses memory for the side chain blocks,
// it isn't currently necessary.
// TODO(davec): Keep a flag if this has already been done to avoid
// multiple runs.
// The coinbase for the Genesis block is not spendable, so just return
// now.
if node.hash.IsEqual(b.chainParams().GenesisHash) {
return nil
}
// BIP0030 added a rule to prevent blocks which contain duplicate
// transactions that 'overwrite' older transactions which are not fully
// spent. See the documentation for checkBIP0030 for more details.
//
// There are two blocks in the chain which violate this
// rule, so the check must be skipped for those blocks. The
// isBIP0030Node function is used to determine if this block is one
// of the two blocks that must be skipped.
enforceBIP0030 := !isBIP0030Node(node)
if enforceBIP0030 {
err := b.checkBIP0030(node, block)
if err != nil {
return err
}
}
// Request a map that contains all input transactions for the block from
// the point of view of its position within the block chain. These
// transactions are needed for verification of things such as
// transaction inputs, counting pay-to-script-hashes, and scripts.
txInputStore, err := b.fetchInputTransactions(node, block)
if err != nil {
return err
}
// BIP0016 describes a pay-to-script-hash type that is considered a
// "standard" type. The rules for this BIP only apply to transactions
// after the timestmap defined by btcscript.Bip16Activation. See
// https://en.bitcoin.it/wiki/BIP_0016 for more details.
enforceBIP0016 := false
if node.timestamp.After(btcscript.Bip16Activation) {
enforceBIP0016 = true
}
// The number of signature operations must be less than the maximum
// allowed per block. Note that the preliminary sanity checks on a
// block also include a check similar to this one, but this check
// expands the count to include a precise count of pay-to-script-hash
// signature operations in each of the input transaction public key
// scripts.
transactions := block.Transactions()
totalSigOps := 0
for i, tx := range transactions {
numsigOps := countSigOps(tx)
if enforceBIP0016 {
// Since the first (and only the first) transaction has
// already been verified to be a coinbase transaction,
// use i == 0 as an optimization for the flag to
// countP2SHSigOps for whether or not the transaction is
// a coinbase transaction rather than having to do a
// full coinbase check again.
numP2SHSigOps, err := countP2SHSigOps(tx, i == 0,
txInputStore)
if err != nil {
return err
}
numsigOps += numP2SHSigOps
}
// Check for overflow or going over the limits. We have to do
// this on every loop iteration to avoid overflow.
lastSigops := totalSigOps
totalSigOps += numsigOps
if totalSigOps < lastSigops || totalSigOps > maxSigOpsPerBlock {
str := fmt.Sprintf("block contains too many "+
"signature operations - got %v, max %v",
totalSigOps, maxSigOpsPerBlock)
return RuleError(str)
}
}
// Perform several checks on the inputs for each transaction. Also
// accumulate the total fees. This could technically be combined with
// the loop above instead of running another loop over the transactions,
// but by separating it we can avoid running the more expensive (though
// still relatively cheap as compared to running the scripts) checks
// against all the inputs when the signature operations are out of
// bounds.
var totalFees int64
for _, tx := range transactions {
txFee, err := CheckTransactionInputs(tx, node.height, txInputStore)
if err != nil {
return err
}
// Sum the total fees and ensure we don't overflow the
// accumulator.
lastTotalFees := totalFees
totalFees += txFee
if totalFees < lastTotalFees {
return RuleError("total fees for block overflows " +
"accumulator")
}
}
// The total output values of the coinbase transaction must not exceed
// the expected subsidy value plus total transaction fees gained from
// mining the block. It is safe to ignore overflow and out of range
// errors here because those error conditions would have already been
// caught by checkTransactionSanity.
var totalSatoshiOut int64
for _, txOut := range transactions[0].MsgTx().TxOut {
totalSatoshiOut += txOut.Value
}
expectedSatoshiOut := calcBlockSubsidy(node.height) + totalFees
if totalSatoshiOut > expectedSatoshiOut {
str := fmt.Sprintf("coinbase transaction for block pays %v "+
"which is more than expected value of %v",
totalSatoshiOut, expectedSatoshiOut)
return RuleError(str)
}
// Don't run scripts if this node is before the latest known good
// checkpoint since the validity is verified via the checkpoints (all
// transactions are included in the merkle root hash and any changes
// will therefore be detected by the next checkpoint). This is a huge
// optimization because running the scripts is the most time consuming
// portion of block handling.
checkpoint := b.LatestCheckpoint()
runScripts := !b.noVerify
if checkpoint != nil && node.height <= checkpoint.Height {
runScripts = false
}
// Now that the inexpensive checks are done and have passed, verify the
// transactions are actually allowed to spend the coins by running the
// expensive ECDSA signature check scripts. Doing this last helps
// prevent CPU exhaustion attacks.
if runScripts {
err := checkBlockScripts(block, txInputStore)
if err != nil {
return err
}
}
return nil
}
// fetchInputTransactions fetches the input transactions referenced by the
// transactions in the given block from its point of view. See fetchTxList
// for more details on what the point of view entails.
func (b *BlockChain) fetchInputTransactions(node *blockNode, block *btcutil.Block) (TxStore, 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[btcwire.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[btcwire.ShaHash]struct{})
txStore := make(TxStore)
for i, tx := range transactions[1:] {
for _, txIn := range tx.MsgTx().TxIn {
// Add an entry to the transaction store for the needed
// transaction with it set to missing by default.
originHash := &txIn.PreviousOutPoint.Hash
txD := &TxData{Hash: originHash, Err: btcdb.ErrTxShaMissing}
txStore[*originHash] = txD
// 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. Update the transaction
// store acccordingly when this is the case. Otherwise,
// we still need the transaction.
//
// 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.
if inFlightIndex, ok := txInFlight[*originHash]; ok &&
i >= inFlightIndex {
originTx := transactions[inFlightIndex]
txD.Tx = originTx
txD.BlockHeight = node.height
txD.Spent = make([]bool, len(originTx.MsgTx().TxOut))
txD.Err = nil
} else {
txNeededSet[*originHash] = struct{}{}
}
}
}
// Request the input transactions from the point of view of the node.
txNeededStore, err := b.fetchTxStore(node, txNeededSet)
if err != nil {
return nil, err
}
// Merge the results of the requested transactions and the in-flight
// transactions.
for _, txD := range txNeededStore {
txStore[*txD.Hash] = txD
}
return txStore, nil
}
