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