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package evidence
import (
"bytes"
"errors"
"fmt"
"sync"
"sync/atomic"
"time"
"github.com/gogo/protobuf/proto"
gogotypes "github.com/gogo/protobuf/types"
"github.com/google/orderedcode"
dbm "github.com/tendermint/tm-db"
clist "github.com/tendermint/tendermint/internal/libs/clist"
sm "github.com/tendermint/tendermint/internal/state"
"github.com/tendermint/tendermint/libs/log"
tmproto "github.com/tendermint/tendermint/proto/tendermint/types"
"github.com/tendermint/tendermint/types"
)
const (
// prefixes are unique across all tm db's
prefixCommitted = int64(9)
prefixPending = int64(10)
)
// Pool maintains a pool of valid evidence to be broadcasted and committed
type Pool struct {
logger log.Logger
evidenceStore dbm.DB
evidenceList *clist.CList // concurrent linked-list of evidence
evidenceSize uint32 // amount of pending evidence
// needed to load validators to verify evidence
stateDB sm.Store
// needed to load headers and commits to verify evidence
blockStore BlockStore
mtx sync.Mutex
// latest state
state sm.State
// evidence from consensus is buffered to this slice, awaiting until the next height
// before being flushed to the pool. This prevents broadcasting and proposing of
// evidence before the height with which the evidence happened is finished.
consensusBuffer []duplicateVoteSet
pruningHeight int64
pruningTime time.Time
}
// NewPool creates an evidence pool. If using an existing evidence store,
// it will add all pending evidence to the concurrent list.
func NewPool(logger log.Logger, evidenceDB dbm.DB, stateDB sm.Store, blockStore BlockStore) (*Pool, error) {
state, err := stateDB.Load()
if err != nil {
return nil, fmt.Errorf("failed to load state: %w", err)
}
pool := &Pool{
stateDB: stateDB,
blockStore: blockStore,
state: state,
logger: logger,
evidenceStore: evidenceDB,
evidenceList: clist.New(),
consensusBuffer: make([]duplicateVoteSet, 0),
}
// If pending evidence already in db, in event of prior failure, then check
// for expiration, update the size and load it back to the evidenceList.
pool.pruningHeight, pool.pruningTime = pool.removeExpiredPendingEvidence()
evList, _, err := pool.listEvidence(prefixPending, -1)
if err != nil {
return nil, err
}
atomic.StoreUint32(&pool.evidenceSize, uint32(len(evList)))
for _, ev := range evList {
pool.evidenceList.PushBack(ev)
}
return pool, nil
}
// PendingEvidence is used primarily as part of block proposal and returns up to
// maxNum of uncommitted evidence.
func (evpool *Pool) PendingEvidence(maxBytes int64) ([]types.Evidence, int64) {
if evpool.Size() == 0 {
return []types.Evidence{}, 0
}
evidence, size, err := evpool.listEvidence(prefixPending, maxBytes)
if err != nil {
evpool.logger.Error("failed to retrieve pending evidence", "err", err)
}
return evidence, size
}
// Update takes both the new state and the evidence committed at that height and performs
// the following operations:
// 1. Take any conflicting votes from consensus and use the state's LastBlockTime to form
// DuplicateVoteEvidence and add it to the pool.
// 2. Update the pool's state which contains evidence params relating to expiry.
// 3. Moves pending evidence that has now been committed into the committed pool.
// 4. Removes any expired evidence based on both height and time.
func (evpool *Pool) Update(state sm.State, ev types.EvidenceList) {
// sanity check
if state.LastBlockHeight <= evpool.state.LastBlockHeight {
panic(fmt.Sprintf(
"failed EvidencePool.Update new state height is less than or equal to previous state height: %d <= %d",
state.LastBlockHeight,
evpool.state.LastBlockHeight,
))
}
evpool.logger.Debug(
"updating evidence pool",
"last_block_height", state.LastBlockHeight,
"last_block_time", state.LastBlockTime,
)
// flush conflicting vote pairs from the buffer, producing DuplicateVoteEvidence and
// adding it to the pool
evpool.processConsensusBuffer(state)
// update state
evpool.updateState(state)
// move committed evidence out from the pending pool and into the committed pool
evpool.markEvidenceAsCommitted(ev, state.LastBlockHeight)
// Prune pending evidence when it has expired. This also updates when the next
// evidence will expire.
if evpool.Size() > 0 && state.LastBlockHeight > evpool.pruningHeight &&
state.LastBlockTime.After(evpool.pruningTime) {
evpool.pruningHeight, evpool.pruningTime = evpool.removeExpiredPendingEvidence()
}
}
// AddEvidence checks the evidence is valid and adds it to the pool.
func (evpool *Pool) AddEvidence(ev types.Evidence) error {
evpool.logger.Debug("attempting to add evidence", "evidence", ev)
// We have already verified this piece of evidence - no need to do it again
if evpool.isPending(ev) {
evpool.logger.Debug("evidence already pending; ignoring", "evidence", ev)
return nil
}
// check that the evidence isn't already committed
if evpool.isCommitted(ev) {
// This can happen if the peer that sent us the evidence is behind so we
// shouldn't punish the peer.
evpool.logger.Debug("evidence was already committed; ignoring", "evidence", ev)
return nil
}
// 1) Verify against state.
if err := evpool.verify(ev); err != nil {
return err
}
// 2) Save to store.
if err := evpool.addPendingEvidence(ev); err != nil {
return fmt.Errorf("failed to add evidence to pending list: %w", err)
}
// 3) Add evidence to clist.
evpool.evidenceList.PushBack(ev)
evpool.logger.Info("verified new evidence of byzantine behavior", "evidence", ev)
return nil
}
// ReportConflictingVotes takes two conflicting votes and forms duplicate vote evidence,
// adding it eventually to the evidence pool.
//
// Duplicate vote attacks happen before the block is committed and the timestamp is
// finalized, thus the evidence pool holds these votes in a buffer, forming the
// evidence from them once consensus at that height has been reached and `Update()` with
// the new state called.
//
// Votes are not verified.
func (evpool *Pool) ReportConflictingVotes(voteA, voteB *types.Vote) {
evpool.mtx.Lock()
defer evpool.mtx.Unlock()
evpool.consensusBuffer = append(evpool.consensusBuffer, duplicateVoteSet{
VoteA: voteA,
VoteB: voteB,
})
}
// CheckEvidence takes an array of evidence from a block and verifies all the evidence there.
// If it has already verified the evidence then it jumps to the next one. It ensures that no
// evidence has already been committed or is being proposed twice. It also adds any
// evidence that it doesn't currently have so that it can quickly form ABCI Evidence later.
func (evpool *Pool) CheckEvidence(evList types.EvidenceList) error {
hashes := make([][]byte, len(evList))
for idx, ev := range evList {
_, isLightEv := ev.(*types.LightClientAttackEvidence)
// We must verify light client attack evidence regardless because there could be a
// different conflicting block with the same hash.
if isLightEv || !evpool.isPending(ev) {
// check that the evidence isn't already committed
if evpool.isCommitted(ev) {
return &types.ErrInvalidEvidence{Evidence: ev, Reason: errors.New("evidence was already committed")}
}
err := evpool.verify(ev)
if err != nil {
return err
}
if err := evpool.addPendingEvidence(ev); err != nil {
// Something went wrong with adding the evidence but we already know it is valid
// hence we log an error and continue
evpool.logger.Error("failed to add evidence to pending list", "err", err, "evidence", ev)
}
evpool.logger.Info("check evidence: verified evidence of byzantine behavior", "evidence", ev)
}
// check for duplicate evidence. We cache hashes so we don't have to work them out again.
hashes[idx] = ev.Hash()
for i := idx - 1; i >= 0; i-- {
if bytes.Equal(hashes[i], hashes[idx]) {
return &types.ErrInvalidEvidence{Evidence: ev, Reason: errors.New("duplicate evidence")}
}
}
}
return nil
}
// EvidenceFront goes to the first evidence in the clist
func (evpool *Pool) EvidenceFront() *clist.CElement {
return evpool.evidenceList.Front()
}
// EvidenceWaitChan is a channel that closes once the first evidence in the list
// is there. i.e Front is not nil.
func (evpool *Pool) EvidenceWaitChan() <-chan struct{} {
return evpool.evidenceList.WaitChan()
}
// Size returns the number of evidence in the pool.
func (evpool *Pool) Size() uint32 {
return atomic.LoadUint32(&evpool.evidenceSize)
}
// State returns the current state of the evpool.
func (evpool *Pool) State() sm.State {
evpool.mtx.Lock()
defer evpool.mtx.Unlock()
return evpool.state
}
func (evpool *Pool) Close() error {
return evpool.evidenceStore.Close()
}
// IsExpired checks whether evidence or a polc is expired by checking whether a height and time is older
// than set by the evidence consensus parameters
func (evpool *Pool) isExpired(height int64, time time.Time) bool {
var (
params = evpool.State().ConsensusParams.Evidence
ageDuration = evpool.State().LastBlockTime.Sub(time)
ageNumBlocks = evpool.State().LastBlockHeight - height
)
return ageNumBlocks > params.MaxAgeNumBlocks &&
ageDuration > params.MaxAgeDuration
}
// IsCommitted returns true if we have already seen this exact evidence and it is already marked as committed.
func (evpool *Pool) isCommitted(evidence types.Evidence) bool {
key := keyCommitted(evidence)
ok, err := evpool.evidenceStore.Has(key)
if err != nil {
evpool.logger.Error("failed to find committed evidence", "err", err)
}
return ok
}
// IsPending checks whether the evidence is already pending. DB errors are passed to the logger.
func (evpool *Pool) isPending(evidence types.Evidence) bool {
key := keyPending(evidence)
ok, err := evpool.evidenceStore.Has(key)
if err != nil {
evpool.logger.Error("failed to find pending evidence", "err", err)
}
return ok
}
func (evpool *Pool) addPendingEvidence(ev types.Evidence) error {
evpb, err := types.EvidenceToProto(ev)
if err != nil {
return fmt.Errorf("failed to convert to proto: %w", err)
}
evBytes, err := evpb.Marshal()
if err != nil {
return fmt.Errorf("failed to marshal evidence: %w", err)
}
key := keyPending(ev)
err = evpool.evidenceStore.Set(key, evBytes)
if err != nil {
return fmt.Errorf("failed to persist evidence: %w", err)
}
atomic.AddUint32(&evpool.evidenceSize, 1)
return nil
}
// markEvidenceAsCommitted processes all the evidence in the block, marking it as
// committed and removing it from the pending database.
func (evpool *Pool) markEvidenceAsCommitted(evidence types.EvidenceList, height int64) {
blockEvidenceMap := make(map[string]struct{}, len(evidence))
batch := evpool.evidenceStore.NewBatch()
defer batch.Close()
for _, ev := range evidence {
if evpool.isPending(ev) {
if err := batch.Delete(keyPending(ev)); err != nil {
evpool.logger.Error("failed to batch delete pending evidence", "err", err)
}
blockEvidenceMap[evMapKey(ev)] = struct{}{}
}
// Add evidence to the committed list. As the evidence is stored in the block store
// we only need to record the height that it was saved at.
key := keyCommitted(ev)
h := gogotypes.Int64Value{Value: height}
evBytes, err := proto.Marshal(&h)
if err != nil {
evpool.logger.Error("failed to marshal committed evidence", "key(height/hash)", key, "err", err)
continue
}
if err := evpool.evidenceStore.Set(key, evBytes); err != nil {
evpool.logger.Error("failed to save committed evidence", "key(height/hash)", key, "err", err)
}
evpool.logger.Debug("marked evidence as committed", "evidence", ev)
}
// check if we need to remove any pending evidence
if len(blockEvidenceMap) == 0 {
return
}
// remove committed evidence from pending bucket
if err := batch.WriteSync(); err != nil {
evpool.logger.Error("failed to batch delete pending evidence", "err", err)
return
}
// remove committed evidence from the clist
evpool.removeEvidenceFromList(blockEvidenceMap)
// update the evidence size
atomic.AddUint32(&evpool.evidenceSize, ^uint32(len(blockEvidenceMap)-1))
}
// listEvidence retrieves lists evidence from oldest to newest within maxBytes.
// If maxBytes is -1, there's no cap on the size of returned evidence.
func (evpool *Pool) listEvidence(prefixKey int64, maxBytes int64) ([]types.Evidence, int64, error) {
var (
evSize int64
totalSize int64
evidence []types.Evidence
evList tmproto.EvidenceList // used for calculating the bytes size
)
iter, err := dbm.IteratePrefix(evpool.evidenceStore, prefixToBytes(prefixKey))
if err != nil {
return nil, totalSize, fmt.Errorf("database error: %w", err)
}
defer iter.Close()
for ; iter.Valid(); iter.Next() {
var evpb tmproto.Evidence
if err := evpb.Unmarshal(iter.Value()); err != nil {
return evidence, totalSize, err
}
evList.Evidence = append(evList.Evidence, evpb)
evSize = int64(evList.Size())
if maxBytes != -1 && evSize > maxBytes {
if err := iter.Error(); err != nil {
return evidence, totalSize, err
}
return evidence, totalSize, nil
}
ev, err := types.EvidenceFromProto(&evpb)
if err != nil {
return nil, totalSize, err
}
totalSize = evSize
evidence = append(evidence, ev)
}
if err := iter.Error(); err != nil {
return evidence, totalSize, err
}
return evidence, totalSize, nil
}
func (evpool *Pool) removeExpiredPendingEvidence() (int64, time.Time) {
batch := evpool.evidenceStore.NewBatch()
defer batch.Close()
height, time, blockEvidenceMap := evpool.batchExpiredPendingEvidence(batch)
// if we haven't removed any evidence then return early
if len(blockEvidenceMap) == 0 {
return height, time
}
evpool.logger.Debug("removing expired evidence",
"height", evpool.State().LastBlockHeight,
"time", evpool.State().LastBlockTime,
"expired evidence", len(blockEvidenceMap),
)
// remove expired evidence from pending bucket
if err := batch.WriteSync(); err != nil {
evpool.logger.Error("failed to batch delete pending evidence", "err", err)
return evpool.State().LastBlockHeight, evpool.State().LastBlockTime
}
// remove evidence from the clist
evpool.removeEvidenceFromList(blockEvidenceMap)
// update the evidence size
atomic.AddUint32(&evpool.evidenceSize, ^uint32(len(blockEvidenceMap)-1))
return height, time
}
func (evpool *Pool) batchExpiredPendingEvidence(batch dbm.Batch) (int64, time.Time, map[string]struct{}) {
blockEvidenceMap := make(map[string]struct{})
iter, err := dbm.IteratePrefix(evpool.evidenceStore, prefixToBytes(prefixPending))
if err != nil {
evpool.logger.Error("failed to iterate over pending evidence", "err", err)
return evpool.State().LastBlockHeight, evpool.State().LastBlockTime, blockEvidenceMap
}
defer iter.Close()
for ; iter.Valid(); iter.Next() {
ev, err := bytesToEv(iter.Value())
if err != nil {
evpool.logger.Error("failed to transition evidence from protobuf", "err", err, "ev", ev)
continue
}
// if true, we have looped through all expired evidence
if !evpool.isExpired(ev.Height(), ev.Time()) {
// Return the height and time with which this evidence will have expired
// so we know when to prune next.
return ev.Height() + evpool.State().ConsensusParams.Evidence.MaxAgeNumBlocks + 1,
ev.Time().Add(evpool.State().ConsensusParams.Evidence.MaxAgeDuration).Add(time.Second),
blockEvidenceMap
}
// else add to the batch
if err := batch.Delete(iter.Key()); err != nil {
evpool.logger.Error("failed to batch delete evidence", "err", err, "ev", ev)
continue
}
// and add to the map to remove the evidence from the clist
blockEvidenceMap[evMapKey(ev)] = struct{}{}
}
return evpool.State().LastBlockHeight, evpool.State().LastBlockTime, blockEvidenceMap
}
func (evpool *Pool) removeEvidenceFromList(
blockEvidenceMap map[string]struct{}) {
for e := evpool.evidenceList.Front(); e != nil; e = e.Next() {
// Remove from clist
ev := e.Value.(types.Evidence)
if _, ok := blockEvidenceMap[evMapKey(ev)]; ok {
evpool.evidenceList.Remove(e)
e.DetachPrev()
}
}
}
func (evpool *Pool) updateState(state sm.State) {
evpool.mtx.Lock()
defer evpool.mtx.Unlock()
evpool.state = state
}
// processConsensusBuffer converts all the duplicate votes witnessed from consensus
// into DuplicateVoteEvidence. It sets the evidence timestamp to the block height
// from the most recently committed block.
// Evidence is then added to the pool so as to be ready to be broadcasted and proposed.
func (evpool *Pool) processConsensusBuffer(state sm.State) {
evpool.mtx.Lock()
defer evpool.mtx.Unlock()
for _, voteSet := range evpool.consensusBuffer {
// Check the height of the conflicting votes and fetch the corresponding time and validator set
// to produce the valid evidence
var (
dve *types.DuplicateVoteEvidence
err error
)
switch {
case voteSet.VoteA.Height == state.LastBlockHeight:
dve, err = types.NewDuplicateVoteEvidence(
voteSet.VoteA,
voteSet.VoteB,
state.LastBlockTime,
state.LastValidators,
)
case voteSet.VoteA.Height < state.LastBlockHeight:
valSet, dbErr := evpool.stateDB.LoadValidators(voteSet.VoteA.Height)
if dbErr != nil {
evpool.logger.Error("failed to load validator set for conflicting votes",
"height", voteSet.VoteA.Height, "err", err)
continue
}
blockMeta := evpool.blockStore.LoadBlockMeta(voteSet.VoteA.Height)
if blockMeta == nil {
evpool.logger.Error("failed to load block time for conflicting votes", "height", voteSet.VoteA.Height)
continue
}
dve, err = types.NewDuplicateVoteEvidence(
voteSet.VoteA,
voteSet.VoteB,
blockMeta.Header.Time,
valSet,
)
default:
// evidence pool shouldn't expect to get votes from consensus of a height that is above the current
// state. If this error is seen then perhaps consider keeping the votes in the buffer and retry
// in following heights
evpool.logger.Error("inbound duplicate votes from consensus are of a greater height than current state",
"duplicate vote height", voteSet.VoteA.Height,
"state.LastBlockHeight", state.LastBlockHeight)
continue
}
if err != nil {
evpool.logger.Error("error in generating evidence from votes", "err", err)
continue
}
// check if we already have this evidence
if evpool.isPending(dve) {
evpool.logger.Debug("evidence already pending; ignoring", "evidence", dve)
continue
}
// check that the evidence is not already committed on chain
if evpool.isCommitted(dve) {
evpool.logger.Debug("evidence already committed; ignoring", "evidence", dve)
continue
}
if err := evpool.addPendingEvidence(dve); err != nil {
evpool.logger.Error("failed to flush evidence from consensus buffer to pending list: %w", err)
continue
}
evpool.evidenceList.PushBack(dve)
evpool.logger.Info("verified new evidence of byzantine behavior", "evidence", dve)
}
// reset consensus buffer
evpool.consensusBuffer = make([]duplicateVoteSet, 0)
}
type duplicateVoteSet struct {
VoteA *types.Vote
VoteB *types.Vote
}
func bytesToEv(evBytes []byte) (types.Evidence, error) {
var evpb tmproto.Evidence
err := evpb.Unmarshal(evBytes)
if err != nil {
return &types.DuplicateVoteEvidence{}, err
}
return types.EvidenceFromProto(&evpb)
}
func evMapKey(ev types.Evidence) string {
return string(ev.Hash())
}
func prefixToBytes(prefix int64) []byte {
key, err := orderedcode.Append(nil, prefix)
if err != nil {
panic(err)
}
return key
}
func keyCommitted(evidence types.Evidence) []byte {
height := evidence.Height()
key, err := orderedcode.Append(nil, prefixCommitted, height, string(evidence.Hash()))
if err != nil {
panic(err)
}
return key
}
func keyPending(evidence types.Evidence) []byte {
height := evidence.Height()
key, err := orderedcode.Append(nil, prefixPending, height, string(evidence.Hash()))
if err != nil {
panic(err)
}
return key
}