lnd.xprv/watchtower/wtdb/tower_db.go

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package wtdb
import (
"bytes"
"errors"
"github.com/btcsuite/btcd/chaincfg/chainhash"
"github.com/lightningnetwork/lnd/chainntnfs"
"github.com/lightningnetwork/lnd/channeldb/kvdb"
"github.com/lightningnetwork/lnd/watchtower/blob"
)
const (
// towerDBName is the filename of tower database.
towerDBName = "watchtower.db"
)
var (
// sessionsBkt is a bucket containing all negotiated client sessions.
// session id -> session
sessionsBkt = []byte("sessions-bucket")
// updatesBkt is a bucket containing all state updates sent by clients.
// The updates are further bucketed by session id to prevent clients
// from overwrite each other.
// hint => session id -> update
updatesBkt = []byte("updates-bucket")
// updateIndexBkt is a bucket that indexes all state updates by their
// overarching session id. This allows for efficient lookup of updates
// by their session id, which is currently used to aide deletion
// performance.
// session id => hint1 -> []byte{}
// => hint2 -> []byte{}
updateIndexBkt = []byte("update-index-bucket")
// lookoutTipBkt is a bucket containing the last block epoch processed
// by the lookout subsystem. It has one key, lookoutTipKey.
// lookoutTipKey -> block epoch
lookoutTipBkt = []byte("lookout-tip-bucket")
// lookoutTipKey is a static key used to retrieve lookout tip's block
// epoch from the lookoutTipBkt.
lookoutTipKey = []byte("lookout-tip")
// ErrNoSessionHintIndex signals that an active session does not have an
// initialized index for tracking its own state updates.
ErrNoSessionHintIndex = errors.New("session hint index missing")
// ErrInvalidBlobSize indicates that the encrypted blob provided by the
// client is not valid according to the blob type of the session.
ErrInvalidBlobSize = errors.New("invalid blob size")
)
// TowerDB is single database providing a persistent storage engine for the
// wtserver and lookout subsystems.
type TowerDB struct {
db kvdb.Backend
dbPath string
}
// OpenTowerDB opens the tower database given the path to the database's
// directory. If no such database exists, this method will initialize a fresh
// one using the latest version number and bucket structure. If a database
// exists but has a lower version number than the current version, any necessary
// migrations will be applied before returning. Any attempt to open a database
// with a version number higher that the latest version will fail to prevent
// accidental reversion.
func OpenTowerDB(dbPath string) (*TowerDB, error) {
bdb, firstInit, err := createDBIfNotExist(dbPath, towerDBName)
if err != nil {
return nil, err
}
towerDB := &TowerDB{
db: bdb,
dbPath: dbPath,
}
err = initOrSyncVersions(towerDB, firstInit, towerDBVersions)
if err != nil {
bdb.Close()
return nil, err
}
// Now that the database version fully consistent with our latest known
// version, ensure that all top-level buckets known to this version are
// initialized. This allows us to assume their presence throughout all
// operations. If an known top-level bucket is expected to exist but is
// missing, this will trigger a ErrUninitializedDB error.
err = kvdb.Update(towerDB.db, initTowerDBBuckets)
if err != nil {
bdb.Close()
return nil, err
}
return towerDB, nil
}
// initTowerDBBuckets creates all top-level buckets required to handle database
// operations required by the latest version.
func initTowerDBBuckets(tx kvdb.RwTx) error {
buckets := [][]byte{
sessionsBkt,
updateIndexBkt,
updatesBkt,
lookoutTipBkt,
}
for _, bucket := range buckets {
_, err := tx.CreateTopLevelBucket(bucket)
if err != nil {
return err
}
}
return nil
}
// bdb returns the backing bbolt.DB instance.
//
// NOTE: Part of the versionedDB interface.
func (t *TowerDB) bdb() kvdb.Backend {
return t.db
}
// Version returns the database's current version number.
//
// NOTE: Part of the versionedDB interface.
func (t *TowerDB) Version() (uint32, error) {
var version uint32
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err := kvdb.View(t.db, func(tx kvdb.RTx) error {
var err error
version, err = getDBVersion(tx)
return err
})
if err != nil {
return 0, err
}
return version, nil
}
// Close closes the underlying database.
func (t *TowerDB) Close() error {
return t.db.Close()
}
// GetSessionInfo retrieves the session for the passed session id. An error is
// returned if the session could not be found.
func (t *TowerDB) GetSessionInfo(id *SessionID) (*SessionInfo, error) {
var session *SessionInfo
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err := kvdb.View(t.db, func(tx kvdb.RTx) error {
sessions := tx.ReadBucket(sessionsBkt)
if sessions == nil {
return ErrUninitializedDB
}
var err error
session, err = getSession(sessions, id[:])
return err
})
if err != nil {
return nil, err
}
return session, nil
}
// InsertSessionInfo records a negotiated session in the tower database. An
// error is returned if the session already exists.
func (t *TowerDB) InsertSessionInfo(session *SessionInfo) error {
return kvdb.Update(t.db, func(tx kvdb.RwTx) error {
sessions := tx.ReadWriteBucket(sessionsBkt)
if sessions == nil {
return ErrUninitializedDB
}
updateIndex := tx.ReadWriteBucket(updateIndexBkt)
if updateIndex == nil {
return ErrUninitializedDB
}
dbSession, err := getSession(sessions, session.ID[:])
switch {
case err == ErrSessionNotFound:
// proceed.
case err != nil:
return err
case dbSession.LastApplied > 0:
return ErrSessionAlreadyExists
}
// Perform a quick sanity check on the session policy before
// accepting.
if err := session.Policy.Validate(); err != nil {
return err
}
err = putSession(sessions, session)
if err != nil {
return err
}
// Initialize the session-hint index which will be used to track
// all updates added for this session. Upon deletion, we will
// consult the index to determine exactly which updates should
// be deleted without needing to iterate over the entire
// database.
return touchSessionHintBkt(updateIndex, &session.ID)
})
}
// InsertStateUpdate stores an update sent by the client after validating that
// the update is well-formed in the context of other updates sent for the same
// session. This include verifying that the sequence number is incremented
// properly and the last applied values echoed by the client are sane.
func (t *TowerDB) InsertStateUpdate(update *SessionStateUpdate) (uint16, error) {
var lastApplied uint16
err := kvdb.Update(t.db, func(tx kvdb.RwTx) error {
sessions := tx.ReadWriteBucket(sessionsBkt)
if sessions == nil {
return ErrUninitializedDB
}
updates := tx.ReadWriteBucket(updatesBkt)
if updates == nil {
return ErrUninitializedDB
}
updateIndex := tx.ReadWriteBucket(updateIndexBkt)
if updateIndex == nil {
return ErrUninitializedDB
}
// Fetch the session corresponding to the update's session id.
// This will be used to validate that the update's sequence
// number and last applied values are sane.
session, err := getSession(sessions, update.ID[:])
if err != nil {
return err
}
// Assert that the blob is the correct size for the session's
// blob type.
expBlobSize := blob.Size(session.Policy.BlobType)
if len(update.EncryptedBlob) != expBlobSize {
return ErrInvalidBlobSize
}
// Validate the update against the current state of the session.
err = session.AcceptUpdateSequence(
update.SeqNum, update.LastApplied,
)
if err != nil {
return err
}
// Validation succeeded, therefore the update is committed and
// the session's last applied value is equal to the update's
// sequence number.
lastApplied = session.LastApplied
// Store the updated session to persist the updated last applied
// values.
err = putSession(sessions, session)
if err != nil {
return err
}
// Create or load the hint bucket for this state update's hint
// and write the given update.
hints, err := updates.CreateBucketIfNotExists(update.Hint[:])
if err != nil {
return err
}
var b bytes.Buffer
err = update.Encode(&b)
if err != nil {
return err
}
err = hints.Put(update.ID[:], b.Bytes())
if err != nil {
return err
}
// Finally, create an entry in the update index to track this
// hint under its session id. This will allow us to delete the
// entries efficiently if the session is ever removed.
return putHintForSession(updateIndex, &update.ID, update.Hint)
})
if err != nil {
return 0, err
}
return lastApplied, nil
}
// DeleteSession removes all data associated with a particular session id from
// the tower's database.
func (t *TowerDB) DeleteSession(target SessionID) error {
return kvdb.Update(t.db, func(tx kvdb.RwTx) error {
sessions := tx.ReadWriteBucket(sessionsBkt)
if sessions == nil {
return ErrUninitializedDB
}
updates := tx.ReadWriteBucket(updatesBkt)
if updates == nil {
return ErrUninitializedDB
}
updateIndex := tx.ReadWriteBucket(updateIndexBkt)
if updateIndex == nil {
return ErrUninitializedDB
}
// Fail if the session doesn't exit.
_, err := getSession(sessions, target[:])
if err != nil {
return err
}
// Remove the target session.
err = sessions.Delete(target[:])
if err != nil {
return err
}
// Next, check the update index for any hints that were added
// under this session.
hints, err := getHintsForSession(updateIndex, &target)
if err != nil {
return err
}
for _, hint := range hints {
// Remove the state updates for any blobs stored under
// the target session identifier.
updatesForHint := updates.NestedReadWriteBucket(hint[:])
if updatesForHint == nil {
continue
}
update := updatesForHint.Get(target[:])
if update == nil {
continue
}
err := updatesForHint.Delete(target[:])
if err != nil {
return err
}
// If this was the last state update, we can also remove
// the hint that would map to an empty set.
err = isBucketEmpty(updatesForHint)
switch {
// Other updates exist for this hint, keep the bucket.
case err == errBucketNotEmpty:
continue
// Unexpected error.
case err != nil:
return err
// No more updates for this hint, prune hint bucket.
default:
err = updates.DeleteNestedBucket(hint[:])
if err != nil {
return err
}
}
}
// Finally, remove this session from the update index, which
// also removes any of the indexed hints beneath it.
return removeSessionHintBkt(updateIndex, &target)
})
}
// QueryMatches searches against all known state updates for any that match the
// passed breachHints. More than one Match will be returned for a given hint if
// they exist in the database.
func (t *TowerDB) QueryMatches(breachHints []blob.BreachHint) ([]Match, error) {
var matches []Match
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err := kvdb.View(t.db, func(tx kvdb.RTx) error {
sessions := tx.ReadBucket(sessionsBkt)
if sessions == nil {
return ErrUninitializedDB
}
updates := tx.ReadBucket(updatesBkt)
if updates == nil {
return ErrUninitializedDB
}
// Iterate through the target breach hints, appending any
// matching updates to the set of matches.
for _, hint := range breachHints {
// If a bucket does not exist for this hint, no matches
// are known.
updatesForHint := updates.NestedReadBucket(hint[:])
if updatesForHint == nil {
continue
}
// Otherwise, iterate through all (session id, update)
// pairs, creating a Match for each.
err := updatesForHint.ForEach(func(k, v []byte) error {
// Load the session via the session id for this
// update. The session info contains further
// instructions for how to process the state
// update.
session, err := getSession(sessions, k)
switch {
case err == ErrSessionNotFound:
log.Warnf("Missing session=%x for "+
"matched state update hint=%x",
k, hint)
return nil
case err != nil:
return err
}
// Decode the state update containing the
// encrypted blob.
update := &SessionStateUpdate{}
err = update.Decode(bytes.NewReader(v))
if err != nil {
return err
}
var id SessionID
copy(id[:], k)
// Construct the final match using the found
// update and its session info.
match := Match{
ID: id,
SeqNum: update.SeqNum,
Hint: hint,
EncryptedBlob: update.EncryptedBlob,
SessionInfo: session,
}
matches = append(matches, match)
return nil
})
if err != nil {
return err
}
}
return nil
})
if err != nil {
return nil, err
}
return matches, nil
}
// SetLookoutTip stores the provided epoch as the latest lookout tip epoch in
// the tower database.
func (t *TowerDB) SetLookoutTip(epoch *chainntnfs.BlockEpoch) error {
return kvdb.Update(t.db, func(tx kvdb.RwTx) error {
lookoutTip := tx.ReadWriteBucket(lookoutTipBkt)
if lookoutTip == nil {
return ErrUninitializedDB
}
return putLookoutEpoch(lookoutTip, epoch)
})
}
// GetLookoutTip retrieves the current lookout tip block epoch from the tower
// database.
func (t *TowerDB) GetLookoutTip() (*chainntnfs.BlockEpoch, error) {
var epoch *chainntnfs.BlockEpoch
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err := kvdb.View(t.db, func(tx kvdb.RTx) error {
lookoutTip := tx.ReadBucket(lookoutTipBkt)
if lookoutTip == nil {
return ErrUninitializedDB
}
epoch = getLookoutEpoch(lookoutTip)
return nil
})
if err != nil {
return nil, err
}
return epoch, nil
}
// getSession retrieves the session info from the sessions bucket identified by
// its session id. An error is returned if the session is not found or a
// deserialization error occurs.
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func getSession(sessions kvdb.RBucket, id []byte) (*SessionInfo, error) {
sessionBytes := sessions.Get(id)
if sessionBytes == nil {
return nil, ErrSessionNotFound
}
var session SessionInfo
err := session.Decode(bytes.NewReader(sessionBytes))
if err != nil {
return nil, err
}
return &session, nil
}
// putSession stores the session info in the sessions bucket identified by its
// session id. An error is returned if a serialization error occurs.
func putSession(sessions kvdb.RwBucket, session *SessionInfo) error {
var b bytes.Buffer
err := session.Encode(&b)
if err != nil {
return err
}
return sessions.Put(session.ID[:], b.Bytes())
}
// touchSessionHintBkt initializes the session-hint bucket for a particular
// session id. This ensures that future calls to getHintsForSession or
// putHintForSession can rely on the bucket already being created, and fail if
// index has not been initialized as this points to improper usage.
func touchSessionHintBkt(updateIndex kvdb.RwBucket, id *SessionID) error {
_, err := updateIndex.CreateBucketIfNotExists(id[:])
return err
}
// removeSessionHintBkt prunes the session-hint bucket for the given session id
// and all of the hints contained inside. This should be used to clean up the
// index upon session deletion.
func removeSessionHintBkt(updateIndex kvdb.RwBucket, id *SessionID) error {
return updateIndex.DeleteNestedBucket(id[:])
}
// getHintsForSession returns all known hints belonging to the given session id.
// If the index for the session has not been initialized, this method returns
// ErrNoSessionHintIndex.
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func getHintsForSession(updateIndex kvdb.RBucket,
id *SessionID) ([]blob.BreachHint, error) {
sessionHints := updateIndex.NestedReadBucket(id[:])
if sessionHints == nil {
return nil, ErrNoSessionHintIndex
}
var hints []blob.BreachHint
err := sessionHints.ForEach(func(k, _ []byte) error {
if len(k) != blob.BreachHintSize {
return nil
}
var hint blob.BreachHint
copy(hint[:], k)
hints = append(hints, hint)
return nil
})
if err != nil {
return nil, err
}
return hints, nil
}
// putHintForSession inserts a record into the update index for a given
// (session, hint) pair. The hints are coalesced under a bucket for the target
// session id, and used to perform efficient removal of updates. If the index
// for the session has not been initialized, this method returns
// ErrNoSessionHintIndex.
func putHintForSession(updateIndex kvdb.RwBucket, id *SessionID,
hint blob.BreachHint) error {
sessionHints := updateIndex.NestedReadWriteBucket(id[:])
if sessionHints == nil {
return ErrNoSessionHintIndex
}
return sessionHints.Put(hint[:], []byte{})
}
// putLookoutEpoch stores the given lookout tip block epoch in provided bucket.
func putLookoutEpoch(bkt kvdb.RwBucket, epoch *chainntnfs.BlockEpoch) error {
epochBytes := make([]byte, 36)
copy(epochBytes, epoch.Hash[:])
byteOrder.PutUint32(epochBytes[32:], uint32(epoch.Height))
return bkt.Put(lookoutTipKey, epochBytes)
}
// getLookoutEpoch retrieves the lookout tip block epoch from the given bucket.
// A nil epoch is returned if no update exists.
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func getLookoutEpoch(bkt kvdb.RBucket) *chainntnfs.BlockEpoch {
epochBytes := bkt.Get(lookoutTipKey)
if len(epochBytes) != 36 {
return nil
}
var hash chainhash.Hash
copy(hash[:], epochBytes[:32])
height := byteOrder.Uint32(epochBytes[32:])
return &chainntnfs.BlockEpoch{
Hash: &hash,
Height: int32(height),
}
}
// errBucketNotEmpty is a helper error returned when testing whether a bucket is
// empty or not.
var errBucketNotEmpty = errors.New("bucket not empty")
// isBucketEmpty returns errBucketNotEmpty if the bucket is not empty.
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func isBucketEmpty(bkt kvdb.RBucket) error {
return bkt.ForEach(func(_, _ []byte) error {
return errBucketNotEmpty
})
}