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package lite
import (
"bytes"
"fmt"
"sync"
log "github.com/tendermint/tendermint/libs/log"
lerr "github.com/tendermint/tendermint/lite/errors"
"github.com/tendermint/tendermint/types"
)
const sizeOfPendingMap = 1024
var _ Verifier = (*DynamicVerifier)(nil)
// DynamicVerifier implements an auto-updating Verifier. It uses a
// "source" provider to obtain the needed FullCommits to securely sync with
// validator set changes. It stores properly validated data on the
// "trusted" local system.
// TODO: make this single threaded and create a new
// ConcurrentDynamicVerifier that wraps it with concurrency.
// see https://github.com/tendermint/tendermint/issues/3170
type DynamicVerifier struct {
chainID string
logger log.Logger
// Already validated, stored locally
trusted PersistentProvider
// New info, like a node rpc, or other import method.
source Provider
// pending map to synchronize concurrent verification requests
mtx sync.Mutex
pendingVerifications map[int64]chan struct{}
}
// NewDynamicVerifier returns a new DynamicVerifier. It uses the
// trusted provider to store validated data and the source provider to
// obtain missing data (e.g. FullCommits).
//
// The trusted provider should be a DBProvider.
// The source provider should be a client.HTTPProvider.
func NewDynamicVerifier(chainID string, trusted PersistentProvider, source Provider) *DynamicVerifier {
return &DynamicVerifier{
logger: log.NewNopLogger(),
chainID: chainID,
trusted: trusted,
source: source,
pendingVerifications: make(map[int64]chan struct{}, sizeOfPendingMap),
}
}
func (dv *DynamicVerifier) SetLogger(logger log.Logger) {
logger = logger.With("module", "lite")
dv.logger = logger
dv.trusted.SetLogger(logger)
dv.source.SetLogger(logger)
}
// Implements Verifier.
func (dv *DynamicVerifier) ChainID() string {
return dv.chainID
}
// Implements Verifier.
//
// If the validators have changed since the last known time, it looks to
// dv.trusted and dv.source to prove the new validators. On success, it will
// try to store the SignedHeader in dv.trusted if the next
// validator can be sourced.
func (dv *DynamicVerifier) Verify(shdr types.SignedHeader) error {
// Performs synchronization for multi-threads verification at the same height.
dv.mtx.Lock()
if pending := dv.pendingVerifications[shdr.Height]; pending != nil {
dv.mtx.Unlock()
<-pending // pending is chan struct{}
} else {
pending := make(chan struct{})
dv.pendingVerifications[shdr.Height] = pending
defer func() {
close(pending)
dv.mtx.Lock()
delete(dv.pendingVerifications, shdr.Height)
dv.mtx.Unlock()
}()
dv.mtx.Unlock()
}
//Get the exact trusted commit for h, and if it is
// equal to shdr, then it's already trusted, so
// just return nil.
trustedFCSameHeight, err := dv.trusted.LatestFullCommit(dv.chainID, shdr.Height, shdr.Height)
if err == nil {
// If loading trust commit successfully, and trust commit equal to shdr, then don't verify it,
// just return nil.
if bytes.Equal(trustedFCSameHeight.SignedHeader.Hash(), shdr.Hash()) {
dv.logger.Info(fmt.Sprintf("Load full commit at height %d from cache, there is not need to verify.", shdr.Height))
return nil
}
} else if !lerr.IsErrCommitNotFound(err) {
// Return error if it is not CommitNotFound error
dv.logger.Info(fmt.Sprintf("Encountered unknown error in loading full commit at height %d.", shdr.Height))
return err
}
// Get the latest known full commit <= h-1 from our trusted providers.
// The full commit at h-1 contains the valset to sign for h.
prevHeight := shdr.Height - 1
trustedFC, err := dv.trusted.LatestFullCommit(dv.chainID, 1, prevHeight)
if err != nil {
return err
}
// sync up to the prevHeight and assert our latest NextValidatorSet
// is the ValidatorSet for the SignedHeader
if trustedFC.Height() == prevHeight {
// Return error if valset doesn't match.
if !bytes.Equal(
trustedFC.NextValidators.Hash(),
shdr.Header.ValidatorsHash) {
return lerr.ErrUnexpectedValidators(
trustedFC.NextValidators.Hash(),
shdr.Header.ValidatorsHash)
}
} else {
// If valset doesn't match, try to update
if !bytes.Equal(
trustedFC.NextValidators.Hash(),
shdr.Header.ValidatorsHash) {
// ... update.
trustedFC, err = dv.updateToHeight(prevHeight)
if err != nil {
return err
}
// Return error if valset _still_ doesn't match.
if !bytes.Equal(trustedFC.NextValidators.Hash(),
shdr.Header.ValidatorsHash) {
return lerr.ErrUnexpectedValidators(
trustedFC.NextValidators.Hash(),
shdr.Header.ValidatorsHash)
}
}
}
// Verify the signed header using the matching valset.
cert := NewBaseVerifier(dv.chainID, trustedFC.Height()+1, trustedFC.NextValidators)
err = cert.Verify(shdr)
if err != nil {
return err
}
// By now, the SignedHeader is fully validated and we're synced up to
// SignedHeader.Height - 1. To sync to SignedHeader.Height, we need
// the validator set at SignedHeader.Height + 1 so we can verify the
// SignedHeader.NextValidatorSet.
// TODO: is the ValidateFull below mostly redundant with the BaseVerifier.Verify above?
// See https://github.com/tendermint/tendermint/issues/3174.
// Get the next validator set.
nextValset, err := dv.source.ValidatorSet(dv.chainID, shdr.Height+1)
if lerr.IsErrUnknownValidators(err) {
// Ignore this error.
return nil
} else if err != nil {
return err
}
// Create filled FullCommit.
nfc := FullCommit{
SignedHeader: shdr,
Validators: trustedFC.NextValidators,
NextValidators: nextValset,
}
// Validate the full commit. This checks the cryptographic
// signatures of Commit against Validators.
if err := nfc.ValidateFull(dv.chainID); err != nil {
return err
}
// Trust it.
return dv.trusted.SaveFullCommit(nfc)
}
// verifyAndSave will verify if this is a valid source full commit given the
// best match trusted full commit, and if good, persist to dv.trusted.
// Returns ErrTooMuchChange when >2/3 of trustedFC did not sign sourceFC.
// Panics if trustedFC.Height() >= sourceFC.Height().
func (dv *DynamicVerifier) verifyAndSave(trustedFC, sourceFC FullCommit) error {
if trustedFC.Height() >= sourceFC.Height() {
panic("should not happen")
}
err := trustedFC.NextValidators.VerifyFutureCommit(
sourceFC.Validators,
dv.chainID, sourceFC.SignedHeader.Commit.BlockID,
sourceFC.SignedHeader.Height, sourceFC.SignedHeader.Commit,
)
if err != nil {
return err
}
return dv.trusted.SaveFullCommit(sourceFC)
}
// updateToHeight will use divide-and-conquer to find a path to h.
// Returns nil error iff we successfully verify and persist a full commit
// for height h, using repeated applications of bisection if necessary.
//
// Returns ErrCommitNotFound if source provider doesn't have the commit for h.
func (dv *DynamicVerifier) updateToHeight(h int64) (FullCommit, error) {
// Fetch latest full commit from source.
sourceFC, err := dv.source.LatestFullCommit(dv.chainID, h, h)
if err != nil {
return FullCommit{}, err
}
// If sourceFC.Height() != h, we can't do it.
if sourceFC.Height() != h {
return FullCommit{}, lerr.ErrCommitNotFound()
}
// Validate the full commit. This checks the cryptographic
// signatures of Commit against Validators.
if err := sourceFC.ValidateFull(dv.chainID); err != nil {
return FullCommit{}, err
}
// Verify latest FullCommit against trusted FullCommits
FOR_LOOP:
for {
// Fetch latest full commit from trusted.
trustedFC, err := dv.trusted.LatestFullCommit(dv.chainID, 1, h)
if err != nil {
return FullCommit{}, err
}
// We have nothing to do.
if trustedFC.Height() == h {
return trustedFC, nil
}
// Try to update to full commit with checks.
err = dv.verifyAndSave(trustedFC, sourceFC)
if err == nil {
// All good!
return sourceFC, nil
}
// Handle special case when err is ErrTooMuchChange.
if types.IsErrTooMuchChange(err) {
// Divide and conquer.
start, end := trustedFC.Height(), sourceFC.Height()
if !(start < end) {
panic("should not happen")
}
mid := (start + end) / 2
_, err = dv.updateToHeight(mid)
if err != nil {
return FullCommit{}, err
}
// If we made it to mid, we retry.
continue FOR_LOOP
}
return FullCommit{}, err
}
}
func (dv *DynamicVerifier) LastTrustedHeight() int64 {
fc, err := dv.trusted.LatestFullCommit(dv.chainID, 1, 1<<63-1)
if err != nil {
panic("should not happen")
}
return fc.Height()
}
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