-
Notifications
You must be signed in to change notification settings - Fork 181
/
client.go
1113 lines (968 loc) · 35.2 KB
/
client.go
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
552
553
554
555
556
557
558
559
560
561
562
563
564
565
566
567
568
569
570
571
572
573
574
575
576
577
578
579
580
581
582
583
584
585
586
587
588
589
590
591
592
593
594
595
596
597
598
599
600
601
602
603
604
605
606
607
608
609
610
611
612
613
614
615
616
617
618
619
620
621
622
623
624
625
626
627
628
629
630
631
632
633
634
635
636
637
638
639
640
641
642
643
644
645
646
647
648
649
650
651
652
653
654
655
656
657
658
659
660
661
662
663
664
665
666
667
668
669
670
671
672
673
674
675
676
677
678
679
680
681
682
683
684
685
686
687
688
689
690
691
692
693
694
695
696
697
698
699
700
701
702
703
704
705
706
707
708
709
710
711
712
713
714
715
716
717
718
719
720
721
722
723
724
725
726
727
728
729
730
731
732
733
734
735
736
737
738
739
740
741
742
743
744
745
746
747
748
749
750
751
752
753
754
755
756
757
758
759
760
761
762
763
764
765
766
767
768
769
770
771
772
773
774
775
776
777
778
779
780
781
782
783
784
785
786
787
788
789
790
791
792
793
794
795
796
797
798
799
800
801
802
803
804
805
806
807
808
809
810
811
812
813
814
815
816
817
818
819
820
821
822
823
824
825
826
827
828
829
830
831
832
833
834
835
836
837
838
839
840
841
842
843
844
845
846
847
848
849
850
851
852
853
854
855
856
857
858
859
860
861
862
863
864
865
866
867
868
869
870
871
872
873
874
875
876
877
878
879
880
881
882
883
884
885
886
887
888
889
890
891
892
893
894
895
896
897
898
899
900
901
902
903
904
905
906
907
908
909
910
911
912
913
914
915
916
917
918
919
920
921
922
923
924
925
926
927
928
929
930
931
932
933
934
935
936
937
938
939
940
941
942
943
944
945
946
947
948
949
950
951
952
953
954
955
956
957
958
959
960
961
962
963
964
965
966
967
968
969
970
971
972
973
974
975
976
977
978
979
980
981
982
983
984
985
986
987
988
989
990
991
992
993
994
995
996
997
998
999
1000
package lite
import (
"bytes"
"fmt"
"math/rand"
"sync"
"time"
"github.com/pkg/errors"
"github.com/okex/exchain/libs/tendermint/libs/log"
tmmath "github.com/okex/exchain/libs/tendermint/libs/math"
"github.com/okex/exchain/libs/tendermint/lite2/provider"
"github.com/okex/exchain/libs/tendermint/lite2/store"
"github.com/okex/exchain/libs/tendermint/types"
)
type mode byte
const (
sequential mode = iota + 1
skipping
defaultPruningSize = 1000
defaultMaxRetryAttempts = 10
// For bisection, when using the cache of headers from the previous batch,
// they will always be at a height greater than 1/2 (normal bisection) so to
// find something in between the range, 9/16 is used.
bisectionNumerator = 9
bisectionDenominator = 16
// 10s should cover most of the clients.
// References:
// - http://vancouver-webpages.com/time/web.html
// - https://blog.codinghorror.com/keeping-time-on-the-pc/
defaultMaxClockDrift = 10 * time.Second
)
// Option sets a parameter for the light client.
type Option func(*Client)
// SequentialVerification option configures the light client to sequentially
// check the headers (every header, in ascending height order). Note this is
// much slower than SkippingVerification, albeit more secure.
func SequentialVerification() Option {
return func(c *Client) {
c.verificationMode = sequential
}
}
// SkippingVerification option configures the light client to skip headers as
// long as {trustLevel} of the old validator set signed the new header. The
// bisection algorithm from the specification is used for finding the minimal
// "trust path".
//
// trustLevel - fraction of the old validator set (in terms of voting power),
// which must sign the new header in order for us to trust it. NOTE this only
// applies to non-adjacent headers. For adjacent headers, sequential
// verification is used.
func SkippingVerification(trustLevel tmmath.Fraction) Option {
return func(c *Client) {
c.verificationMode = skipping
c.trustLevel = trustLevel
}
}
// PruningSize option sets the maximum amount of headers & validator set pairs
// that the light client stores. When Prune() is run, all headers (along with
// the associated validator sets) that are earlier than the h amount of headers
// will be removed from the store. Default: 1000. A pruning size of 0 will not
// prune the lite client at all.
func PruningSize(h uint16) Option {
return func(c *Client) {
c.pruningSize = h
}
}
// ConfirmationFunction option can be used to prompt to confirm an action. For
// example, remove newer headers if the light client is being reset with an
// older header. No confirmation is required by default!
func ConfirmationFunction(fn func(action string) bool) Option {
return func(c *Client) {
c.confirmationFn = fn
}
}
// Logger option can be used to set a logger for the client.
func Logger(l log.Logger) Option {
return func(c *Client) {
c.logger = l
}
}
// MaxRetryAttempts option can be used to set max attempts before replacing
// primary with a witness.
func MaxRetryAttempts(max uint16) Option {
return func(c *Client) {
c.maxRetryAttempts = max
}
}
// MaxClockDrift defines how much new (untrusted) header's Time can drift into
// the future. Default: 10s.
func MaxClockDrift(d time.Duration) Option {
return func(c *Client) {
c.maxClockDrift = d
}
}
// Client represents a light client, connected to a single chain, which gets
// headers from a primary provider, verifies them either sequentially or by
// skipping some and stores them in a trusted store (usually, a local FS).
//
// Default verification: SkippingVerification(DefaultTrustLevel)
type Client struct {
chainID string
trustingPeriod time.Duration // see TrustOptions.Period
verificationMode mode
trustLevel tmmath.Fraction
maxRetryAttempts uint16 // see MaxRetryAttempts option
maxClockDrift time.Duration
// Mutex for locking during changes of the lite clients providers
providerMutex sync.Mutex
// Primary provider of new headers.
primary provider.Provider
// See Witnesses option
witnesses []provider.Provider
// Where trusted headers are stored.
trustedStore store.Store
// Highest trusted header from the store (height=H).
latestTrustedHeader *types.SignedHeader
// Highest validator set from the store (height=H).
latestTrustedVals *types.ValidatorSet
// See RemoveNoLongerTrustedHeadersPeriod option
pruningSize uint16
// See ConfirmationFunction option
confirmationFn func(action string) bool
quit chan struct{}
logger log.Logger
}
// NewClient returns a new light client. It returns an error if it fails to
// obtain the header & vals from the primary or they are invalid (e.g. trust
// hash does not match with the one from the header).
//
// Witnesses are providers, which will be used for cross-checking the primary
// provider. At least one witness must be given. A witness can become a primary
// iff the current primary is unavailable.
//
// See all Option(s) for the additional configuration.
func NewClient(
chainID string,
trustOptions TrustOptions,
primary provider.Provider,
witnesses []provider.Provider,
trustedStore store.Store,
options ...Option) (*Client, error) {
if err := trustOptions.ValidateBasic(); err != nil {
return nil, fmt.Errorf("invalid TrustOptions: %w", err)
}
c, err := NewClientFromTrustedStore(chainID, trustOptions.Period, primary, witnesses, trustedStore, options...)
if err != nil {
return nil, err
}
if c.latestTrustedHeader != nil {
c.logger.Info("Checking trusted header using options")
if err := c.checkTrustedHeaderUsingOptions(trustOptions); err != nil {
return nil, err
}
}
if c.latestTrustedHeader == nil || c.latestTrustedHeader.Height < trustOptions.Height {
c.logger.Info("Downloading trusted header using options")
if err := c.initializeWithTrustOptions(trustOptions); err != nil {
return nil, err
}
}
return c, err
}
// NewClientFromTrustedStore initializes existing client from the trusted store.
//
// See NewClient
func NewClientFromTrustedStore(
chainID string,
trustingPeriod time.Duration,
primary provider.Provider,
witnesses []provider.Provider,
trustedStore store.Store,
options ...Option) (*Client, error) {
c := &Client{
chainID: chainID,
trustingPeriod: trustingPeriod,
verificationMode: skipping,
trustLevel: DefaultTrustLevel,
maxRetryAttempts: defaultMaxRetryAttempts,
maxClockDrift: defaultMaxClockDrift,
primary: primary,
witnesses: witnesses,
trustedStore: trustedStore,
pruningSize: defaultPruningSize,
confirmationFn: func(action string) bool { return true },
quit: make(chan struct{}),
logger: log.NewNopLogger(),
}
for _, o := range options {
o(c)
}
// Validate the number of witnesses.
if len(c.witnesses) < 1 {
return nil, errNoWitnesses{}
}
// Verify witnesses are all on the same chain.
for i, w := range witnesses {
if w.ChainID() != chainID {
return nil, fmt.Errorf("witness #%d: %v is on another chain %s, expected %s",
i, w, w.ChainID(), chainID)
}
}
// Validate trust level.
if err := ValidateTrustLevel(c.trustLevel); err != nil {
return nil, err
}
if err := c.restoreTrustedHeaderAndVals(); err != nil {
return nil, err
}
return c, nil
}
// restoreTrustedHeaderAndVals loads trustedHeader and trustedVals from
// trustedStore.
func (c *Client) restoreTrustedHeaderAndVals() error {
lastHeight, err := c.trustedStore.LastSignedHeaderHeight()
if err != nil {
return fmt.Errorf("can't get last trusted header height: %w", err)
}
if lastHeight > 0 {
trustedHeader, err := c.trustedStore.SignedHeader(lastHeight)
if err != nil {
return fmt.Errorf("can't get last trusted header: %w", err)
}
trustedVals, err := c.trustedStore.ValidatorSet(lastHeight)
if err != nil {
return fmt.Errorf("can't get last trusted validators: %w", err)
}
c.latestTrustedHeader = trustedHeader
c.latestTrustedVals = trustedVals
c.logger.Info("Restored trusted header and vals", "height", lastHeight)
}
return nil
}
// if options.Height:
//
// 1) ahead of trustedHeader.Height => fetch header (same height as
// trustedHeader) from primary provider and check it's hash matches the
// trustedHeader's hash (if not, remove trustedHeader and all the headers
// before)
//
// 2) equals trustedHeader.Height => check options.Hash matches the
// trustedHeader's hash (if not, remove trustedHeader and all the headers
// before)
//
// 3) behind trustedHeader.Height => remove all the headers between
// options.Height and trustedHeader.Height, update trustedHeader, then
// check options.Hash matches the trustedHeader's hash (if not, remove
// trustedHeader and all the headers before)
//
// The intuition here is the user is always right. I.e. if she decides to reset
// the light client with an older header, there must be a reason for it.
func (c *Client) checkTrustedHeaderUsingOptions(options TrustOptions) error {
var primaryHash []byte
switch {
case options.Height > c.latestTrustedHeader.Height:
h, err := c.signedHeaderFromPrimary(c.latestTrustedHeader.Height)
if err != nil {
return err
}
primaryHash = h.Hash()
case options.Height == c.latestTrustedHeader.Height:
primaryHash = options.Hash
case options.Height < c.latestTrustedHeader.Height:
c.logger.Info("Client initialized with old header (trusted is more recent)",
"old", options.Height,
"trustedHeight", c.latestTrustedHeader.Height,
"trustedHash", hash2str(c.latestTrustedHeader.Hash()))
action := fmt.Sprintf(
"Rollback to %d (%X)? Note this will remove newer headers up to %d (%X)",
options.Height, options.Hash,
c.latestTrustedHeader.Height, c.latestTrustedHeader.Hash())
if c.confirmationFn(action) {
// remove all the headers (options.Height, trustedHeader.Height]
err := c.cleanupAfter(options.Height)
if err != nil {
return fmt.Errorf("cleanupAfter(%d): %w", options.Height, err)
}
c.logger.Info("Rolled back to older header (newer headers were removed)",
"old", options.Height)
} else {
return nil
}
primaryHash = options.Hash
}
if !bytes.Equal(primaryHash, c.latestTrustedHeader.Hash()) {
c.logger.Info("Prev. trusted header's hash (h1) doesn't match hash from primary provider (h2)",
"h1", hash2str(c.latestTrustedHeader.Hash()), "h2", hash2str(primaryHash))
action := fmt.Sprintf(
"Prev. trusted header's hash %X doesn't match hash %X from primary provider. Remove all the stored headers?",
c.latestTrustedHeader.Hash(), primaryHash)
if c.confirmationFn(action) {
err := c.Cleanup()
if err != nil {
return fmt.Errorf("failed to cleanup: %w", err)
}
} else {
return errors.New("refused to remove the stored headers despite hashes mismatch")
}
}
return nil
}
// initializeWithTrustOptions fetches the weakly-trusted header and vals from
// primary provider. The header is cross-checked with witnesses for additional
// security.
func (c *Client) initializeWithTrustOptions(options TrustOptions) error {
// 1) Fetch and verify the header.
h, err := c.signedHeaderFromPrimary(options.Height)
if err != nil {
return err
}
// NOTE: - Verify func will check if it's expired or not.
// - h.Time is not being checked against time.Now() because we don't
// want to add yet another argument to NewClient* functions.
if err := h.ValidateBasic(c.chainID); err != nil {
return err
}
if !bytes.Equal(h.Hash(), options.Hash) {
return fmt.Errorf("expected header's hash %X, but got %X", options.Hash, h.Hash())
}
err = c.compareNewHeaderWithWitnesses(h)
if err != nil {
return err
}
// 2) Fetch and verify the vals.
vals, err := c.validatorSetFromPrimary(options.Height)
if err != nil {
return err
}
if !bytes.Equal(h.ValidatorsHash, vals.Hash()) {
return fmt.Errorf("expected header's validators (%X) to match those that were supplied (%X)",
h.ValidatorsHash,
vals.Hash(),
)
}
// Ensure that +2/3 of validators signed correctly.
err = vals.VerifyCommitLight(c.chainID, h.Commit.BlockID, h.Height, h.Commit)
if err != nil {
return fmt.Errorf("invalid commit: %w", err)
}
// 3) Persist both of them and continue.
return c.updateTrustedHeaderAndVals(h, vals)
}
// TrustedHeader returns a trusted header at the given height (0 - the latest).
//
// Headers along with validator sets, which can't be trusted anymore, are
// removed once a day (can be changed with RemoveNoLongerTrustedHeadersPeriod
// option).
// .
// height must be >= 0.
//
// It returns an error if:
// - there are some issues with the trusted store, although that should not
// happen normally;
// - negative height is passed;
// - header has not been verified yet and is therefore not in the store
//
// Safe for concurrent use by multiple goroutines.
func (c *Client) TrustedHeader(height int64) (*types.SignedHeader, error) {
height, err := c.compareWithLatestHeight(height)
if err != nil {
return nil, err
}
return c.trustedStore.SignedHeader(height)
}
// TrustedValidatorSet returns a trusted validator set at the given height (0 -
// latest). The second return parameter is the height used (useful if 0 was
// passed; otherwise can be ignored).
//
// height must be >= 0.
//
// Headers along with validator sets are
// removed once a day (can be changed with RemoveNoLongerTrustedHeadersPeriod
// option).
//
// Function returns an error if:
// - there are some issues with the trusted store, although that should not
// happen normally;
// - negative height is passed;
// - header signed by that validator set has not been verified yet
//
// Safe for concurrent use by multiple goroutines.
func (c *Client) TrustedValidatorSet(height int64) (valSet *types.ValidatorSet, heightUsed int64, err error) {
heightUsed, err = c.compareWithLatestHeight(height)
if err != nil {
return nil, heightUsed, err
}
valSet, err = c.trustedStore.ValidatorSet(heightUsed)
if err != nil {
return nil, heightUsed, err
}
return valSet, heightUsed, err
}
func (c *Client) compareWithLatestHeight(height int64) (int64, error) {
latestHeight, err := c.LastTrustedHeight()
if err != nil {
return 0, fmt.Errorf("can't get last trusted height: %w", err)
}
if latestHeight == -1 {
return 0, errors.New("no headers exist")
}
switch {
case height > latestHeight:
return 0, fmt.Errorf("unverified header/valset requested (latest: %d)", latestHeight)
case height == 0:
return latestHeight, nil
case height < 0:
return 0, errors.New("negative height")
}
return height, nil
}
// VerifyHeaderAtHeight fetches header and validators at the given height
// and calls VerifyHeader. It returns header immediately if such exists in
// trustedStore (no verification is needed).
//
// height must be > 0.
//
// It returns provider.ErrSignedHeaderNotFound if header is not found by
// primary.
func (c *Client) VerifyHeaderAtHeight(height int64, now time.Time) (*types.SignedHeader, error) {
if height <= 0 {
return nil, errors.New("negative or zero height")
}
// Check if header already verified.
h, err := c.TrustedHeader(height)
if err == nil {
c.logger.Info("Header has already been verified", "height", height, "hash", hash2str(h.Hash()))
// Return already trusted header
return h, nil
}
// Request the header and the vals.
newHeader, newVals, err := c.fetchHeaderAndValsAtHeight(height)
if err != nil {
return nil, err
}
return newHeader, c.verifyHeader(newHeader, newVals, now)
}
// VerifyHeader verifies new header against the trusted state. It returns
// immediately if newHeader exists in trustedStore (no verification is
// needed). Else it performs one of the two types of verification:
//
// SequentialVerification: verifies that 2/3 of the trusted validator set has
// signed the new header. If the headers are not adjacent, **all** intermediate
// headers will be requested. Intermediate headers are not saved to database.
//
// SkippingVerification(trustLevel): verifies that {trustLevel} of the trusted
// validator set has signed the new header. If it's not the case and the
// headers are not adjacent, bisection is performed and necessary (not all)
// intermediate headers will be requested. See the specification for details.
// Intermediate headers are not saved to database.
// https://github.com/tendermint/spec/blob/master/spec/consensus/light-client.md
//
// If the header, which is older than the currently trusted header, is
// requested and the light client does not have it, VerifyHeader will perform:
// a) bisection verification if nearest trusted header is found & not expired
// b) backwards verification in all other cases
//
// It returns ErrOldHeaderExpired if the latest trusted header expired.
//
// If the primary provides an invalid header (ErrInvalidHeader), it is rejected
// and replaced by another provider until all are exhausted.
//
// If, at any moment, SignedHeader or ValidatorSet are not found by the primary
// provider, provider.ErrSignedHeaderNotFound /
// provider.ErrValidatorSetNotFound error is returned.
func (c *Client) VerifyHeader(newHeader *types.SignedHeader, newVals *types.ValidatorSet, now time.Time) error {
if newHeader.Height <= 0 {
return errors.New("negative or zero height")
}
// Check if newHeader already verified.
h, err := c.TrustedHeader(newHeader.Height)
if err == nil {
// Make sure it's the same header.
if !bytes.Equal(h.Hash(), newHeader.Hash()) {
return fmt.Errorf("existing trusted header %X does not match newHeader %X", h.Hash(), newHeader.Hash())
}
c.logger.Info("Header has already been verified",
"height", newHeader.Height, "hash", hash2str(newHeader.Hash()))
return nil
}
return c.verifyHeader(newHeader, newVals, now)
}
func (c *Client) verifyHeader(newHeader *types.SignedHeader, newVals *types.ValidatorSet, now time.Time) error {
c.logger.Info("VerifyHeader", "height", newHeader.Height, "hash", hash2str(newHeader.Hash()),
"vals", hash2str(newVals.Hash()))
var err error
// 1) If going forward, perform either bisection or sequential verification.
if newHeader.Height >= c.latestTrustedHeader.Height {
switch c.verificationMode {
case sequential:
err = c.sequence(c.latestTrustedHeader, newHeader, newVals, now)
case skipping:
err = c.bisection(c.latestTrustedHeader, c.latestTrustedVals, newHeader, newVals, now)
default:
panic(fmt.Sprintf("Unknown verification mode: %b", c.verificationMode))
}
} else {
// 2) If verifying before the first trusted header, perform backwards
// verification.
var (
closestHeader *types.SignedHeader
firstHeaderHeight int64
)
firstHeaderHeight, err = c.FirstTrustedHeight()
if err != nil {
return fmt.Errorf("can't get first header height: %w", err)
}
if newHeader.Height < firstHeaderHeight {
closestHeader, err = c.TrustedHeader(firstHeaderHeight)
if err != nil {
return fmt.Errorf("can't get first signed header: %w", err)
}
if HeaderExpired(closestHeader, c.trustingPeriod, now) {
closestHeader = c.latestTrustedHeader
}
err = c.backwards(closestHeader, newHeader, now)
} else {
// 3) OR if between trusted headers where the nearest has not expired,
// perform bisection verification, else backwards.
closestHeader, err = c.trustedStore.SignedHeaderBefore(newHeader.Height)
if err != nil {
return fmt.Errorf("can't get signed header before height %d: %w", newHeader.Height, err)
}
var closestValidatorSet *types.ValidatorSet
if c.verificationMode == sequential || HeaderExpired(closestHeader, c.trustingPeriod, now) {
err = c.backwards(c.latestTrustedHeader, newHeader, now)
} else {
closestValidatorSet, _, err = c.TrustedValidatorSet(closestHeader.Height)
if err != nil {
return fmt.Errorf("can't get validator set at height %d: %w", closestHeader.Height, err)
}
err = c.bisection(closestHeader, closestValidatorSet, newHeader, newVals, now)
}
}
}
if err != nil {
c.logger.Error("Can't verify", "err", err)
return err
}
// 4) Compare header with other witnesses
if err := c.compareNewHeaderWithWitnesses(newHeader); err != nil {
c.logger.Error("Error when comparing new header with witnesses", "err", err)
return err
}
// 5) Once verified, save and return
return c.updateTrustedHeaderAndVals(newHeader, newVals)
}
// see VerifyHeader
func (c *Client) sequence(
initiallyTrustedHeader *types.SignedHeader,
newHeader *types.SignedHeader,
newVals *types.ValidatorSet,
now time.Time) error {
var (
trustedHeader = initiallyTrustedHeader
interimHeader *types.SignedHeader
interimVals *types.ValidatorSet
err error
)
for height := initiallyTrustedHeader.Height + 1; height <= newHeader.Height; height++ {
// 1) Fetch interim headers and vals if needed.
if height == newHeader.Height { // last header
interimHeader, interimVals = newHeader, newVals
} else { // intermediate headers
interimHeader, interimVals, err = c.fetchHeaderAndValsAtHeight(height)
if err != nil {
return err
}
}
// 2) Verify them
c.logger.Debug("Verify newHeader against trustedHeader",
"trustedHeight", trustedHeader.Height,
"trustedHash", hash2str(trustedHeader.Hash()),
"newHeight", interimHeader.Height,
"newHash", hash2str(interimHeader.Hash()))
err = VerifyAdjacent(c.chainID, trustedHeader, interimHeader, interimVals,
c.trustingPeriod, now, c.maxClockDrift)
if err != nil {
err = fmt.Errorf("verify adjacent from #%d to #%d failed: %w",
trustedHeader.Height, interimHeader.Height, err)
switch errors.Unwrap(err).(type) {
case ErrInvalidHeader:
c.logger.Error("primary sent invalid header -> replacing", "err", err)
replaceErr := c.replacePrimaryProvider()
if replaceErr != nil {
c.logger.Error("Can't replace primary", "err", replaceErr)
return err // return original error
}
// attempt to verify header again
height--
continue
default:
return err
}
}
// 3) Update trustedHeader
trustedHeader = interimHeader
}
return nil
}
// see VerifyHeader
// Bisection finds the middle header between a trusted and new header, reiterating the action until it
// verifies a header. A cache of headers requested by the primary is kept such that when a
// verification is made, and the light client tries again to verify the new header in the middle,
// the light client does not need to ask for all the same headers again.
func (c *Client) bisection(
initiallyTrustedHeader *types.SignedHeader,
initiallyTrustedVals *types.ValidatorSet,
newHeader *types.SignedHeader,
newVals *types.ValidatorSet,
now time.Time) error {
type headerSet struct {
sh *types.SignedHeader
valSet *types.ValidatorSet
}
var (
headerCache = []headerSet{{newHeader, newVals}}
depth = 0
trustedHeader = initiallyTrustedHeader
trustedVals = initiallyTrustedVals
)
for {
c.logger.Debug("Verify newHeader against trustedHeader",
"trustedHeight", trustedHeader.Height,
"trustedHash", hash2str(trustedHeader.Hash()),
"newHeight", headerCache[depth].sh.Height,
"newHash", hash2str(headerCache[depth].sh.Hash()))
err := Verify(c.chainID, trustedHeader, trustedVals, headerCache[depth].sh, headerCache[depth].valSet,
c.trustingPeriod, now, c.maxClockDrift, c.trustLevel)
switch err.(type) {
case nil:
// Have we verified the last header
if depth == 0 {
return nil
}
// If not, update the lower bound to the previous upper bound
trustedHeader, trustedVals = headerCache[depth].sh, headerCache[depth].valSet
// Remove the untrusted header at the lower bound in the header cache - it's no longer useful
headerCache = headerCache[:depth]
// Reset the cache depth so that we start from the upper bound again
depth = 0
case ErrNewValSetCantBeTrusted:
// do add another header to the end of the cache
if depth == len(headerCache)-1 {
pivotHeight := trustedHeader.Height + (headerCache[depth].sh.Height-trustedHeader.
Height)*bisectionNumerator/bisectionDenominator
interimHeader, interimVals, err := c.fetchHeaderAndValsAtHeight(pivotHeight)
if err != nil {
return err
}
headerCache = append(headerCache, headerSet{interimHeader, interimVals})
}
depth++
case ErrInvalidHeader:
c.logger.Error("primary sent invalid header -> replacing", "err", err)
replaceErr := c.replacePrimaryProvider()
if replaceErr != nil {
c.logger.Error("Can't replace primary", "err", replaceErr)
// return original error
return fmt.Errorf("verify non adjacent from #%d to #%d failed: %w",
trustedHeader.Height, headerCache[depth].sh.Height, err)
}
// attempt to verify the header again
continue
default:
return fmt.Errorf("verify non adjacent from #%d to #%d failed: %w",
trustedHeader.Height, headerCache[depth].sh.Height, err)
}
}
}
// LastTrustedHeight returns a last trusted height. -1 and nil are returned if
// there are no trusted headers.
//
// Safe for concurrent use by multiple goroutines.
func (c *Client) LastTrustedHeight() (int64, error) {
return c.trustedStore.LastSignedHeaderHeight()
}
// FirstTrustedHeight returns a first trusted height. -1 and nil are returned if
// there are no trusted headers.
//
// Safe for concurrent use by multiple goroutines.
func (c *Client) FirstTrustedHeight() (int64, error) {
return c.trustedStore.FirstSignedHeaderHeight()
}
// ChainID returns the chain ID the light client was configured with.
//
// Safe for concurrent use by multiple goroutines.
func (c *Client) ChainID() string {
return c.chainID
}
// Primary returns the primary provider.
//
// NOTE: provider may be not safe for concurrent access.
func (c *Client) Primary() provider.Provider {
c.providerMutex.Lock()
defer c.providerMutex.Unlock()
return c.primary
}
// Witnesses returns the witness providers.
//
// NOTE: providers may be not safe for concurrent access.
func (c *Client) Witnesses() []provider.Provider {
c.providerMutex.Lock()
defer c.providerMutex.Unlock()
return c.witnesses
}
// Cleanup removes all the data (headers and validator sets) stored. Note: the
// client must be stopped at this point.
func (c *Client) Cleanup() error {
c.logger.Info("Removing all the data")
c.latestTrustedHeader = nil
c.latestTrustedVals = nil
return c.trustedStore.Prune(0)
}
// cleanupAfter deletes all headers & validator sets after +height+. It also
// resets latestTrustedHeader to the latest header.
func (c *Client) cleanupAfter(height int64) error {
prevHeight := c.latestTrustedHeader.Height
for {
h, err := c.trustedStore.SignedHeaderBefore(prevHeight)
if err == store.ErrSignedHeaderNotFound || (h != nil && h.Height <= height) {
break
} else if err != nil {
return fmt.Errorf("failed to get header before %d: %w", prevHeight, err)
}
err = c.trustedStore.DeleteSignedHeaderAndValidatorSet(h.Height)
if err != nil {
c.logger.Error("can't remove a trusted header & validator set", "err", err,
"height", h.Height)
}
prevHeight = h.Height
}
c.latestTrustedHeader = nil
c.latestTrustedVals = nil
err := c.restoreTrustedHeaderAndVals()
if err != nil {
return err
}
return nil
}
func (c *Client) updateTrustedHeaderAndVals(h *types.SignedHeader, vals *types.ValidatorSet) error {
if !bytes.Equal(h.ValidatorsHash, vals.Hash()) {
return fmt.Errorf("expected validator's hash %X, but got %X", h.ValidatorsHash, vals.Hash())
}
if err := c.trustedStore.SaveSignedHeaderAndValidatorSet(h, vals); err != nil {
return fmt.Errorf("failed to save trusted header: %w", err)
}
if c.pruningSize > 0 {
if err := c.trustedStore.Prune(c.pruningSize); err != nil {
return fmt.Errorf("prune: %w", err)
}
}
if c.latestTrustedHeader == nil || h.Height > c.latestTrustedHeader.Height {
c.latestTrustedHeader = h
c.latestTrustedVals = vals
}
return nil
}
// fetch header and validators for the given height (0 - latest) from primary
// provider.
func (c *Client) fetchHeaderAndValsAtHeight(height int64) (*types.SignedHeader, *types.ValidatorSet, error) {
h, err := c.signedHeaderFromPrimary(height)
if err != nil {
return nil, nil, fmt.Errorf("failed to obtain the header #%d: %w", height, err)
}
vals, err := c.validatorSetFromPrimary(height)
if err != nil {
return nil, nil, fmt.Errorf("failed to obtain the vals #%d: %w", height, err)
}
return h, vals, nil
}
// backwards verification (see VerifyHeaderBackwards func in the spec) verifies
// headers before a trusted header. If a sent header is invalid the primary is
// replaced with another provider and the operation is repeated.
func (c *Client) backwards(
initiallyTrustedHeader *types.SignedHeader,
newHeader *types.SignedHeader,
now time.Time) error {
if HeaderExpired(initiallyTrustedHeader, c.trustingPeriod, now) {
c.logger.Error("Header Expired")
return ErrOldHeaderExpired{initiallyTrustedHeader.Time.Add(c.trustingPeriod), now}
}
var (
trustedHeader = initiallyTrustedHeader
interimHeader *types.SignedHeader
err error
)
for trustedHeader.Height > newHeader.Height {
interimHeader, err = c.signedHeaderFromPrimary(trustedHeader.Height - 1)
if err != nil {
return fmt.Errorf("failed to obtain the header at height #%d: %w", trustedHeader.Height-1, err)
}
c.logger.Debug("Verify newHeader against trustedHeader",
"trustedHeight", trustedHeader.Height,
"trustedHash", hash2str(trustedHeader.Hash()),
"newHeight", interimHeader.Height,
"newHash", hash2str(interimHeader.Hash()))
if err := VerifyBackwards(c.chainID, interimHeader, trustedHeader); err != nil {
c.logger.Error("primary sent invalid header -> replacing", "err", err)
if replaceErr := c.replacePrimaryProvider(); replaceErr != nil {
c.logger.Error("Can't replace primary", "err", replaceErr)
// return original error
return fmt.Errorf("verify backwards from %d to %d failed: %w",
trustedHeader.Height, interimHeader.Height, err)
}
}
trustedHeader = interimHeader
}
// Initially trusted header might have expired at this point.
if HeaderExpired(initiallyTrustedHeader, c.trustingPeriod, now) {
return ErrOldHeaderExpired{initiallyTrustedHeader.Time.Add(c.trustingPeriod), now}
}
return nil
}
// compare header with all witnesses provided.
func (c *Client) compareNewHeaderWithWitnesses(h *types.SignedHeader) error {
c.providerMutex.Lock()
defer c.providerMutex.Unlock()
// 1. Make sure AT LEAST ONE witness returns the same header.
headerMatched := false
witnessesToRemove := make([]int, 0)
for attempt := uint16(1); attempt <= c.maxRetryAttempts; attempt++ {
if len(c.witnesses) == 0 {
return errNoWitnesses{}
}
for i, witness := range c.witnesses {
altH, err := witness.SignedHeader(h.Height)
if err != nil {
c.logger.Error("Failed to get a header from witness", "height", h.Height, "witness", witness)
continue
}
if err = altH.ValidateBasic(c.chainID); err != nil {
c.logger.Error("Witness sent us incorrect header", "err", err, "witness", witness)
witnessesToRemove = append(witnessesToRemove, i)
continue
}
if !bytes.Equal(h.Hash(), altH.Hash()) {
if err = c.latestTrustedVals.VerifyCommitLightTrusting(c.chainID, altH.Commit.BlockID,
altH.Height, altH.Commit, c.trustLevel); err != nil {
c.logger.Error("Witness sent us incorrect header", "err", err, "witness", witness)
witnessesToRemove = append(witnessesToRemove, i)
continue
}
// TODO: send the diverged headers to primary && all witnesses
return fmt.Errorf(
"header hash %X does not match one %X from the witness %v",
h.Hash(), altH.Hash(), witness)
}
headerMatched = true
}
for _, idx := range witnessesToRemove {
c.removeWitness(idx)
}
witnessesToRemove = make([]int, 0)
if headerMatched {
return nil
}
// 2. Otherwise, sleep
time.Sleep(backoffTimeout(attempt))
}
return errors.New("awaiting response from all witnesses exceeded dropout time")
}
// NOTE: requires a providerMutex locked.
func (c *Client) removeWitness(idx int) {
switch len(c.witnesses) {
case 0:
panic(fmt.Sprintf("wanted to remove %d element from empty witnesses slice", idx))
case 1:
c.witnesses = make([]provider.Provider, 0)
default:
c.witnesses[idx] = c.witnesses[len(c.witnesses)-1]
c.witnesses = c.witnesses[:len(c.witnesses)-1]
}