blockchain: Allow adding additional checkpoints

Introduces a `--checkpoint` flag that allows the user to specify
additional checkpoints or override the default ones provided in the
chain params.

blockchain/chain.go

@@ -158,6 +158,7 @@ type BlockChain struct {
 	// The following fields are set when the instance is created and can't
 	// be changed afterwards, so there is no need to protect them with a
 	// separate mutex.
+	checkpoints         []chaincfg.Checkpoint
 	checkpointsByHeight map[int32]*chaincfg.Checkpoint
 	db                  database.DB
 	chainParams         *chaincfg.Params
@@ -188,8 +189,7 @@ type BlockChain struct {
 
 	// These fields are configuration parameters that can be toggled at
 	// runtime.  They are protected by the chain lock.
-	noVerify      bool
-	noCheckpoints bool
+	noVerify bool
 
 	// These fields are related to the memory block index.  They are
 	// protected by the chain lock.
@@ -1569,7 +1569,7 @@ func (b *BlockChain) connectBestChain(node *blockNode, block *btcutil.Block, fla
 func (b *BlockChain) isCurrent() bool {
 	// Not current if the latest main (best) chain height is before the
 	// latest known good checkpoint (when checkpoints are enabled).
-	checkpoint := b.latestCheckpoint()
+	checkpoint := b.LatestCheckpoint()
 	if checkpoint != nil && b.bestNode.height < checkpoint.Height {
 		return false
 	}
@@ -1640,6 +1640,12 @@ type Config struct {
 	// This field is required.
 	ChainParams *chaincfg.Params
 
+	// Checkpoints hold caller-defined checkpoints that should be added to the
+	// default checkpoints in ChainParams. Checkpoints must be sorted by height.
+	//
+	// This field can be nil if the caller did not specify any checkpoints.
+	Checkpoints []chaincfg.Checkpoint
+
 	// TimeSource defines the median time source to use for things such as
 	// block processing and determining whether or not the chain is current.
 	//
@@ -1688,20 +1694,21 @@ func New(config *Config) (*BlockChain, error) {
 	}
 
 	// Generate a checkpoint by height map from the provided checkpoints.
-	params := config.ChainParams
 	var checkpointsByHeight map[int32]*chaincfg.Checkpoint
-	if len(params.Checkpoints) > 0 {
+	if len(config.Checkpoints) > 0 {
 		checkpointsByHeight = make(map[int32]*chaincfg.Checkpoint)
-		for i := range params.Checkpoints {
-			checkpoint := &params.Checkpoints[i]
+		for i := range config.Checkpoints {
+			checkpoint := &config.Checkpoints[i]
 			checkpointsByHeight[checkpoint.Height] = checkpoint
 		}
 	}
 
+	params := config.ChainParams
 	targetTimespan := int64(params.TargetTimespan)
 	targetTimePerBlock := int64(params.TargetTimePerBlock)
 	adjustmentFactor := params.RetargetAdjustmentFactor
 	b := BlockChain{
+		checkpoints:         config.Checkpoints,
 		checkpointsByHeight: checkpointsByHeight,
 		db:                  config.DB,
 		chainParams:         params,

blockchain/chain_test.go

@@ -43,9 +43,7 @@ func TestHaveBlock(t *testing.T) {
 	}
 	defer teardownFunc()
 
-	// Since we're not dealing with the real block chain, disable
-	// checkpoints and set the coinbase maturity to 1.
-	chain.DisableCheckpoints(true)
+	// Since we're not dealing with the real block chain, set the coinbase maturity to 1.
 	chain.TstSetCoinbaseMaturity(1)
 
 	for i := 1; i < len(blocks); i++ {
@@ -131,9 +129,7 @@ func TestCalcSequenceLock(t *testing.T) {
 	}
 	defer teardownFunc()
 
-	// Since we're not dealing with the real block chain, disable
-	// checkpoints and set the coinbase maturity to 1.
-	chain.DisableCheckpoints(true)
+	// Since we're not dealing with the real block chain, set the coinbase maturity to 1.
 	chain.TstSetCoinbaseMaturity(1)
 
 	// Load all the blocks into our test chain.

blockchain/checkpoints.go

@@ -27,66 +27,39 @@ func newHashFromStr(hexStr string) *chainhash.Hash {
 	return hash
 }
 
-// DisableCheckpoints provides a mechanism to disable validation against
-// checkpoints which you DO NOT want to do in production.  It is provided only
-// for debug purposes.
-//
-// This function is safe for concurrent access.
-func (b *BlockChain) DisableCheckpoints(disable bool) {
-	b.chainLock.Lock()
-	b.noCheckpoints = disable
-	b.chainLock.Unlock()
-}
-
 // Checkpoints returns a slice of checkpoints (regardless of whether they are
-// already known).  When checkpoints are disabled or there are no checkpoints
-// for the active network, it will return nil.
+// already known).
+// When there are no checkpoints for the chain, it will return nil.
 //
 // This function is safe for concurrent access.
 func (b *BlockChain) Checkpoints() []chaincfg.Checkpoint {
-	b.chainLock.RLock()
-	defer b.chainLock.RUnlock()
-
-	if b.noCheckpoints || len(b.chainParams.Checkpoints) == 0 {
-		return nil
-	}
-
-	return b.chainParams.Checkpoints
+	return b.checkpoints
 }
 
-// latestCheckpoint returns the most recent checkpoint (regardless of whether it
-// is already known).  When checkpoints are disabled or there are no checkpoints
-// for the active network, it will return nil.
+// HasCheckpoints returns whether this BlockChain has checkpoints defined.
 //
-// This function MUST be called with the chain state lock held (for reads).
-func (b *BlockChain) latestCheckpoint() *chaincfg.Checkpoint {
-	if b.noCheckpoints || len(b.chainParams.Checkpoints) == 0 {
-		return nil
-	}
-
-	checkpoints := b.chainParams.Checkpoints
-	return &checkpoints[len(checkpoints)-1]
+// This function is safe for concurrent access.
+func (b *BlockChain) HasCheckpoints() bool {
+	return len(b.checkpoints) > 0
 }
 
-// LatestCheckpoint returns the most recent checkpoint (regardless of whether it
-// is already known).  When checkpoints are disabled or there are no checkpoints
-// for the active network, it will return nil.
+// LatestCheckpoint returns the most recent checkpoint (regardless of whether they
+// are already known). When there are no defined checkpoints for the active chain
+// instance, it will return nil.
 //
 // This function is safe for concurrent access.
 func (b *BlockChain) LatestCheckpoint() *chaincfg.Checkpoint {
-	b.chainLock.RLock()
-	checkpoint := b.latestCheckpoint()
-	b.chainLock.RUnlock()
-	return checkpoint
+	if !b.HasCheckpoints() {
+		return nil
+	}
+	return &b.checkpoints[len(b.checkpoints)-1]
 }
 
 // verifyCheckpoint returns whether the passed block height and hash combination
-// match the hard-coded checkpoint data.  It also returns true if there is no
-// checkpoint data for the passed block height.
-//
-// This function MUST be called with the chain lock held (for reads).
+// match the checkpoint data. It also returns true if there is no checkpoint
+// data for the passed block height.
 func (b *BlockChain) verifyCheckpoint(height int32, hash *chainhash.Hash) bool {
-	if b.noCheckpoints || len(b.chainParams.Checkpoints) == 0 {
+	if !b.HasCheckpoints() {
 		return true
 	}
 
@@ -112,14 +85,14 @@ func (b *BlockChain) verifyCheckpoint(height int32, hash *chainhash.Hash) bool {
 //
 // This function MUST be called with the chain lock held (for reads).
 func (b *BlockChain) findPreviousCheckpoint() (*btcutil.Block, error) {
-	if b.noCheckpoints || len(b.chainParams.Checkpoints) == 0 {
+	if !b.HasCheckpoints() {
 		return nil, nil
 	}
 
-	// No checkpoints.
-	checkpoints := b.chainParams.Checkpoints
+	checkpoints := b.checkpoints
 	numCheckpoints := len(checkpoints)
 	if numCheckpoints == 0 {
+		// No checkpoints.
 		return nil, nil
 	}
 
@@ -261,11 +234,6 @@ func (b *BlockChain) IsCheckpointCandidate(block *btcutil.Block) (bool, error) {
 	b.chainLock.RLock()
 	defer b.chainLock.RUnlock()
 
-	// Checkpoints must be enabled.
-	if b.noCheckpoints {
-		return false, fmt.Errorf("checkpoints are disabled")
-	}
-
 	var isCandidate bool
 	err := b.db.View(func(dbTx database.Tx) error {
 		// A checkpoint must be in the main chain.

blockchain/common_test.go

@@ -116,6 +116,7 @@ func chainSetup(dbName string, params *chaincfg.Params) (*blockchain.BlockChain,
 	chain, err := blockchain.New(&blockchain.Config{
 		DB:          db,
 		ChainParams: &paramsCopy,
+		Checkpoints: nil,
 		TimeSource:  blockchain.NewMedianTime(),
 		SigCache:    txscript.NewSigCache(1000),
 	})

blockchain/reorganization_test.go

@@ -52,9 +52,7 @@ func TestReorganization(t *testing.T) {
 	}
 	defer teardownFunc()
 
-	// Since we're not dealing with the real block chain, disable
-	// checkpoints and set the coinbase maturity to 1.
-	chain.DisableCheckpoints(true)
+	// Since we're not dealing with the real block chain set the coinbase maturity to 1.
 	chain.TstSetCoinbaseMaturity(1)
 
 	expectedOrphans := map[int]struct{}{5: {}, 6: {}}

blockchain/validate.go

@@ -1107,7 +1107,7 @@ func (b *BlockChain) checkConnectBlock(node *blockNode, block *btcutil.Block, vi
 	// 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()
+	checkpoint := b.LatestCheckpoint()
 	runScripts := !b.noVerify
 	if checkpoint != nil && node.height <= checkpoint.Height {
 		runScripts = false

blockmanager.go

@@ -9,6 +9,7 @@ import (
 	"net"
 	"os"
 	"path/filepath"
+	"sort"
 	"sync"
 	"sync/atomic"
 	"time"
@@ -182,7 +183,7 @@ func (b *blockManager) findNextHeaderCheckpoint(height int32) *chaincfg.Checkpoi
 	if cfg.DisableCheckpoints {
 		return nil
 	}
-	checkpoints := b.server.chainParams.Checkpoints
+	checkpoints := b.chain.Checkpoints()
 	if len(checkpoints) == 0 {
 		return nil
 	}
@@ -1324,6 +1325,57 @@ func (b *blockManager) Pause() chan<- struct{} {
 	return c
 }
 
+// checkpointSorter implements sort.Interface to allow a slice of checkpoints to
+// be sorted.
+type checkpointSorter []chaincfg.Checkpoint
+
+// Len returns the number of checkpoints in the slice.  It is part of the
+// sort.Interface implementation.
+func (s checkpointSorter) Len() int {
+	return len(s)
+}
+
+// Swap swaps the checkpoints at the passed indices.  It is part of the
+// sort.Interface implementation.
+func (s checkpointSorter) Swap(i, j int) {
+	s[i], s[j] = s[j], s[i]
+}
+
+// Less returns whether the checkpoint with index i should sort before the
+// checkpoint with index j.  It is part of the sort.Interface implementation.
+func (s checkpointSorter) Less(i, j int) bool {
+	return s[i].Height < s[j].Height
+}
+
+// mergeCheckpoints returns two slices of checkpoints merged into one slice
+// such that the checkpoints are sorted by height.  In the case the additional
+// checkpoints contain a checkpoint with the same height as a checkpoint in the
+// default checkpoints, the additional checkpoint will take precedence and
+// overwrite the default one.
+func mergeCheckpoints(defaultCheckpoints, additional []chaincfg.Checkpoint) []chaincfg.Checkpoint {
+	// Create a map of the additional checkpoint heights to detect
+	// duplicates.
+	additionalHeights := make(map[int32]struct{})
+	for _, checkpoint := range additional {
+		additionalHeights[checkpoint.Height] = struct{}{}
+	}
+
+	// Add all default checkpoints that do not have an override in the
+	// additional checkpoints.
+	numDefault := len(defaultCheckpoints)
+	checkpoints := make([]chaincfg.Checkpoint, 0, numDefault+len(additional))
+	for _, checkpoint := range defaultCheckpoints {
+		if _, exists := additionalHeights[checkpoint.Height]; !exists {
+			checkpoints = append(checkpoints, checkpoint)
+		}
+	}
+
+	// Append the additional checkpoints and return the sorted results.
+	checkpoints = append(checkpoints, additional...)
+	sort.Sort(checkpointSorter(checkpoints))
+	return checkpoints
+}
+
 // newBlockManager returns a new bitcoin block manager.
 // Use Start to begin processing asynchronous block and inv updates.
 func newBlockManager(s *server, indexManager blockchain.IndexManager) (*blockManager, error) {
@@ -1338,11 +1390,18 @@ func newBlockManager(s *server, indexManager blockchain.IndexManager) (*blockMan
 		quit:            make(chan struct{}),
 	}
 
+	// Merge given checkpoints with the default ones unless they are disabled.
+	var checkpoints []chaincfg.Checkpoint
+	if !cfg.DisableCheckpoints {
+		checkpoints = mergeCheckpoints(s.chainParams.Checkpoints, cfg.addCheckpoints)
+	}
+
 	// Create a new block chain instance with the appropriate configuration.
 	var err error
 	bm.chain, err = blockchain.New(&blockchain.Config{
 		DB:            s.db,
 		ChainParams:   s.chainParams,
+		Checkpoints:   checkpoints,
 		TimeSource:    s.timeSource,
 		Notifications: bm.handleNotifyMsg,
 		SigCache:      s.sigCache,
@@ -1352,7 +1411,6 @@ func newBlockManager(s *server, indexManager blockchain.IndexManager) (*blockMan
 		return nil, err
 	}
 	best := bm.chain.BestSnapshot()
-	bm.chain.DisableCheckpoints(cfg.DisableCheckpoints)
 	if !cfg.DisableCheckpoints {
 		// Initialize the next checkpoint based on the current height.
 		bm.nextCheckpoint = bm.findNextHeaderCheckpoint(best.Height)

config.go

@@ -20,6 +20,8 @@ import (
 	"strings"
 	"time"
 
+	"github.com/btcsuite/btcd/chaincfg"
+	"github.com/btcsuite/btcd/chaincfg/chainhash"
 	"github.com/btcsuite/btcd/connmgr"
 	"github.com/btcsuite/btcd/database"
 	_ "github.com/btcsuite/btcd/database/ffldb"
@@ -123,6 +125,7 @@ type config struct {
 	TestNet3             bool          `long:"testnet" description:"Use the test network"`
 	RegressionTest       bool          `long:"regtest" description:"Use the regression test network"`
 	SimNet               bool          `long:"simnet" description:"Use the simulation test network"`
+	AddCheckpoints       []string      `long:"addcheckpoint" description:"Add a custom checkpoint. Format: '<height>:<hash>'"`
 	DisableCheckpoints   bool          `long:"nocheckpoints" description:"Disable built-in checkpoints.  Don't do this unless you know what you're doing."`
 	DbType               string        `long:"dbtype" description:"Database backend to use for the Block Chain"`
 	Profile              string        `long:"profile" description:"Enable HTTP profiling on given port -- NOTE port must be between 1024 and 65536"`
@@ -150,6 +153,7 @@ type config struct {
 	lookup               func(string) ([]net.IP, error)
 	oniondial            func(string, string, time.Duration) (net.Conn, error)
 	dial                 func(string, string, time.Duration) (net.Conn, error)
+	addCheckpoints       []chaincfg.Checkpoint
 	miningAddrs          []btcutil.Address
 	minRelayTxFee        btcutil.Amount
 }
@@ -303,6 +307,49 @@ func normalizeAddresses(addrs []string, defaultPort string) []string {
 	return removeDuplicateAddresses(addrs)
 }
 
+// newCheckpointFromStr parses checkpoints in the '<height>:<hash>' format.
+func newCheckpointFromStr(checkpoint string) (chaincfg.Checkpoint, error) {
+	parts := strings.Split(checkpoint, ":")
+	if len(parts) != 2 {
+		return chaincfg.Checkpoint{}, errors.New("checkpoints must use the " +
+			"syntax '<height>:<hash>'")
+	}
+
+	height, err := strconv.ParseInt(parts[0], 10, 32)
+	if err != nil {
+		return chaincfg.Checkpoint{}, fmt.Errorf("unable to parse checkpoint "+
+			"due to malformed height: %s", parts[0])
+	}
+
+	hash, err := chainhash.NewHashFromStr(parts[1])
+	if err != nil {
+		return chaincfg.Checkpoint{}, fmt.Errorf("unable to parse checkpoint "+
+			"due to malformed hash: %s", parts[1])
+	}
+
+	return chaincfg.Checkpoint{
+		Height: int32(height),
+		Hash:   hash,
+	}, nil
+}
+
+// parseCheckpoints checks the checkpoint strings for valid syntax
+// ('<height>:<hash>') and parses them to chaincfg.Checkpoint instances.
+func parseCheckpoints(checkpointStrings []string) ([]chaincfg.Checkpoint, error) {
+	if len(checkpointStrings) == 0 {
+		return nil, nil
+	}
+	checkpoints := make([]chaincfg.Checkpoint, len(checkpointStrings))
+	for i, cpString := range checkpointStrings {
+		checkpoint, err := newCheckpointFromStr(cpString)
+		if err != nil {
+			return nil, err
+		}
+		checkpoints[i] = checkpoint
+	}
+	return checkpoints, nil
+}
+
 // filesExists reports whether the named file or directory exists.
 func fileExists(name string) bool {
 	if _, err := os.Stat(name); err != nil {
@@ -804,6 +851,16 @@ func loadConfig() (*config, []string, error) {
 		return nil, nil, err
 	}
 
+	// Check the checkpoints for syntax errors.
+	cfg.addCheckpoints, err = parseCheckpoints(cfg.AddCheckpoints)
+	if err != nil {
+		str := "%s: Error parsing checkpoints: %v"
+		err := fmt.Errorf(str, funcName, err)
+		fmt.Fprintln(os.Stderr, err)
+		fmt.Fprintln(os.Stderr, usageMessage)
+		return nil, nil, err
+	}
+
 	// Tor stream isolation requires either proxy or onion proxy to be set.
 	if cfg.TorIsolation && cfg.Proxy == "" && cfg.OnionProxy == "" {
 		str := "%s: Tor stream isolation requires either proxy or " +

doc.go

@@ -74,6 +74,8 @@ Application Options:
       --testnet             Use the test network
       --regtest             Use the regression test network
       --simnet              Use the simulation test network
+      --addcheckpoint=      Add ad additional checkpoint.
+                            Format: '<height>:<hash>'
       --nocheckpoints       Disable built-in checkpoints.  Don't do this unless
                             you know what you're doing.
       --dbtype=             Database backend to use for the Block Chain (ffldb)

sample-btcd.conf

@@ -153,6 +153,9 @@
 ; Disable peer bloom filtering.  See BIP0111.
 ; nopeerbloomfilters=1
 
+; Add additional checkpoints. Format: '<height>:<hash>'
+; addcheckpoint=<height>:<hash>
+
 
 ; ------------------------------------------------------------------------------
 ; RPC server options - The following options control the built-in RPC server