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
|
package downloader
import (
"encoding/binary"
"errors"
"fmt"
"math/big"
"sync/atomic"
"testing"
"time"
"github.com/ethereum/go-ethereum/common"
"github.com/ethereum/go-ethereum/core"
"github.com/ethereum/go-ethereum/core/types"
"github.com/ethereum/go-ethereum/event"
)
var (
knownHash = common.Hash{1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1}
unknownHash = common.Hash{2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2}
bannedHash = common.Hash{3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3}
genesis = createBlock(1, common.Hash{}, knownHash)
)
// idCounter is used by the createHashes method the generate deterministic but unique hashes
var idCounter = int64(2) // #1 is the genesis block
// createHashes generates a batch of hashes rooted at a specific point in the chain.
func createHashes(amount int, root common.Hash) (hashes []common.Hash) {
hashes = make([]common.Hash, amount+1)
hashes[len(hashes)-1] = root
for i := 0; i < len(hashes)-1; i++ {
binary.BigEndian.PutUint64(hashes[i][:8], uint64(idCounter))
idCounter++
}
return
}
// createBlock assembles a new block at the given chain height.
func createBlock(i int, parent, hash common.Hash) *types.Block {
header := &types.Header{Number: big.NewInt(int64(i))}
block := types.NewBlockWithHeader(header)
block.HeaderHash = hash
block.ParentHeaderHash = parent
return block
}
// copyBlock makes a deep copy of a block suitable for local modifications.
func copyBlock(block *types.Block) *types.Block {
return createBlock(int(block.Number().Int64()), block.ParentHeaderHash, block.HeaderHash)
}
func createBlocksFromHashes(hashes []common.Hash) map[common.Hash]*types.Block {
blocks := make(map[common.Hash]*types.Block)
for i := 0; i < len(hashes); i++ {
parent := knownHash
if i < len(hashes)-1 {
parent = hashes[i+1]
}
blocks[hashes[i]] = createBlock(len(hashes)-i, parent, hashes[i])
}
return blocks
}
type downloadTester struct {
downloader *Downloader
ownHashes []common.Hash // Hash chain belonging to the tester
ownBlocks map[common.Hash]*types.Block // Blocks belonging to the tester
peerHashes map[string][]common.Hash // Hash chain belonging to different test peers
peerBlocks map[string]map[common.Hash]*types.Block // Blocks belonging to different test peers
maxHashFetch int // Overrides the maximum number of retrieved hashes
}
func newTester() *downloadTester {
tester := &downloadTester{
ownHashes: []common.Hash{knownHash},
ownBlocks: map[common.Hash]*types.Block{knownHash: genesis},
peerHashes: make(map[string][]common.Hash),
peerBlocks: make(map[string]map[common.Hash]*types.Block),
}
var mux event.TypeMux
downloader := New(&mux, tester.hasBlock, tester.getBlock, tester.insertChain, tester.dropPeer)
tester.downloader = downloader
return tester
}
// sync starts synchronizing with a remote peer, blocking until it completes.
func (dl *downloadTester) sync(id string) error {
err := dl.downloader.synchronise(id, dl.peerHashes[id][0])
for atomic.LoadInt32(&dl.downloader.processing) == 1 {
time.Sleep(time.Millisecond)
}
return err
}
// hasBlock checks if a block is pres ent in the testers canonical chain.
func (dl *downloadTester) hasBlock(hash common.Hash) bool {
return dl.getBlock(hash) != nil
}
// getBlock retrieves a block from the testers canonical chain.
func (dl *downloadTester) getBlock(hash common.Hash) *types.Block {
return dl.ownBlocks[hash]
}
// insertChain injects a new batch of blocks into the simulated chain.
func (dl *downloadTester) insertChain(blocks types.Blocks) (int, error) {
for i, block := range blocks {
if _, ok := dl.ownBlocks[block.ParentHash()]; !ok {
return i, errors.New("unknown parent")
}
dl.ownHashes = append(dl.ownHashes, block.Hash())
dl.ownBlocks[block.Hash()] = block
}
return len(blocks), nil
}
// newPeer registers a new block download source into the downloader.
func (dl *downloadTester) newPeer(id string, hashes []common.Hash, blocks map[common.Hash]*types.Block) error {
return dl.newSlowPeer(id, hashes, blocks, 0)
}
// newSlowPeer registers a new block download source into the downloader, with a
// specific delay time on processing the network packets sent to it, simulating
// potentially slow network IO.
func (dl *downloadTester) newSlowPeer(id string, hashes []common.Hash, blocks map[common.Hash]*types.Block, delay time.Duration) error {
err := dl.downloader.RegisterPeer(id, hashes[0], dl.peerGetHashesFn(id, delay), dl.peerGetBlocksFn(id, delay))
if err == nil {
// Assign the owned hashes and blocks to the peer (deep copy)
dl.peerHashes[id] = make([]common.Hash, len(hashes))
copy(dl.peerHashes[id], hashes)
dl.peerBlocks[id] = make(map[common.Hash]*types.Block)
for hash, block := range blocks {
dl.peerBlocks[id][hash] = copyBlock(block)
}
}
return err
}
// dropPeer simulates a hard peer removal from the connection pool.
func (dl *downloadTester) dropPeer(id string) {
delete(dl.peerHashes, id)
delete(dl.peerBlocks, id)
dl.downloader.UnregisterPeer(id)
}
// peerGetBlocksFn constructs a getHashes function associated with a particular
// peer in the download tester. The returned function can be used to retrieve
// batches of hashes from the particularly requested peer.
func (dl *downloadTester) peerGetHashesFn(id string, delay time.Duration) func(head common.Hash) error {
return func(head common.Hash) error {
time.Sleep(delay)
limit := MaxHashFetch
if dl.maxHashFetch > 0 {
limit = dl.maxHashFetch
}
// Gather the next batch of hashes
hashes := dl.peerHashes[id]
result := make([]common.Hash, 0, limit)
for i, hash := range hashes {
if hash == head {
i++
for len(result) < cap(result) && i < len(hashes) {
result = append(result, hashes[i])
i++
}
break
}
}
// Delay delivery a bit to allow attacks to unfold
go func() {
time.Sleep(time.Millisecond)
dl.downloader.DeliverHashes(id, result)
}()
return nil
}
}
// peerGetBlocksFn constructs a getBlocks function associated with a particular
// peer in the download tester. The returned function can be used to retrieve
// batches of blocks from the particularly requested peer.
func (dl *downloadTester) peerGetBlocksFn(id string, delay time.Duration) func([]common.Hash) error {
return func(hashes []common.Hash) error {
time.Sleep(delay)
blocks := dl.peerBlocks[id]
result := make([]*types.Block, 0, len(hashes))
for _, hash := range hashes {
if block, ok := blocks[hash]; ok {
result = append(result, block)
}
}
go dl.downloader.DeliverBlocks(id, result)
return nil
}
}
// Tests that simple synchronization, without throttling from a good peer works.
func TestSynchronisation(t *testing.T) {
// Create a small enough block chain to download and the tester
targetBlocks := blockCacheLimit - 15
hashes := createHashes(targetBlocks, knownHash)
blocks := createBlocksFromHashes(hashes)
tester := newTester()
tester.newPeer("peer", hashes, blocks)
// Synchronise with the peer and make sure all blocks were retrieved
if err := tester.sync("peer"); err != nil {
t.Fatalf("failed to synchronise blocks: %v", err)
}
if imported := len(tester.ownBlocks); imported != targetBlocks+1 {
t.Fatalf("synchronised block mismatch: have %v, want %v", imported, targetBlocks+1)
}
}
// Tests that an inactive downloader will not accept incoming hashes and blocks.
func TestInactiveDownloader(t *testing.T) {
tester := newTester()
// Check that neither hashes nor blocks are accepted
if err := tester.downloader.DeliverHashes("bad peer", []common.Hash{}); err != errNoSyncActive {
t.Errorf("error mismatch: have %v, want %v", err, errNoSyncActive)
}
if err := tester.downloader.DeliverBlocks("bad peer", []*types.Block{}); err != errNoSyncActive {
t.Errorf("error mismatch: have %v, want %v", err, errNoSyncActive)
}
}
// Tests that a canceled download wipes all previously accumulated state.
func TestCancel(t *testing.T) {
// Create a small enough block chain to download and the tester
targetBlocks := blockCacheLimit - 15
hashes := createHashes(targetBlocks, knownHash)
blocks := createBlocksFromHashes(hashes)
tester := newTester()
tester.newPeer("peer", hashes, blocks)
// Make sure canceling works with a pristine downloader
tester.downloader.Cancel()
hashCount, blockCount := tester.downloader.queue.Size()
if hashCount > 0 || blockCount > 0 {
t.Errorf("block or hash count mismatch: %d hashes, %d blocks, want 0", hashCount, blockCount)
}
// Synchronise with the peer, but cancel afterwards
if err := tester.sync("peer"); err != nil {
t.Fatalf("failed to synchronise blocks: %v", err)
}
tester.downloader.Cancel()
hashCount, blockCount = tester.downloader.queue.Size()
if hashCount > 0 || blockCount > 0 {
t.Errorf("block or hash count mismatch: %d hashes, %d blocks, want 0", hashCount, blockCount)
}
}
// Tests that if a large batch of blocks are being downloaded, it is throttled
// until the cached blocks are retrieved.
func TestThrottling(t *testing.T) {
// Create a long block chain to download and the tester
targetBlocks := 8 * blockCacheLimit
hashes := createHashes(targetBlocks, knownHash)
blocks := createBlocksFromHashes(hashes)
tester := newTester()
tester.newPeer("peer", hashes, blocks)
// Wrap the importer to allow stepping
done := make(chan int)
tester.downloader.insertChain = func(blocks types.Blocks) (int, error) {
n, err := tester.insertChain(blocks)
done <- n
return n, err
}
// Start a synchronisation concurrently
errc := make(chan error)
go func() {
errc <- tester.sync("peer")
}()
// Iteratively take some blocks, always checking the retrieval count
for len(tester.ownBlocks) < targetBlocks+1 {
// Wait a bit for sync to throttle itself
var cached int
for start := time.Now(); time.Since(start) < 3*time.Second; {
time.Sleep(25 * time.Millisecond)
cached = len(tester.downloader.queue.blockPool)
if cached == blockCacheLimit || len(tester.ownBlocks)+cached == targetBlocks+1 {
break
}
}
// Make sure we filled up the cache, then exhaust it
time.Sleep(25 * time.Millisecond) // give it a chance to screw up
if cached != blockCacheLimit && len(tester.ownBlocks)+cached < targetBlocks+1 {
t.Fatalf("block count mismatch: have %v, want %v", cached, blockCacheLimit)
}
<-done // finish previous blocking import
for cached > maxBlockProcess {
cached -= <-done
}
time.Sleep(25 * time.Millisecond) // yield to the insertion
}
<-done // finish the last blocking import
// Check that we haven't pulled more blocks than available
if len(tester.ownBlocks) > targetBlocks+1 {
t.Fatalf("target block count mismatch: have %v, want %v", len(tester.ownBlocks), targetBlocks+1)
}
if err := <-errc; err != nil {
t.Fatalf("block synchronization failed: %v", err)
}
}
// Tests that synchronisation from multiple peers works as intended (multi thread sanity test).
func TestMultiSynchronisation(t *testing.T) {
// Create various peers with various parts of the chain
targetPeers := 16
targetBlocks := targetPeers*blockCacheLimit - 15
hashes := createHashes(targetBlocks, knownHash)
blocks := createBlocksFromHashes(hashes)
tester := newTester()
for i := 0; i < targetPeers; i++ {
id := fmt.Sprintf("peer #%d", i)
tester.newPeer(id, hashes[i*blockCacheLimit:], blocks)
}
// Synchronise with the middle peer and make sure half of the blocks were retrieved
id := fmt.Sprintf("peer #%d", targetPeers/2)
if err := tester.sync(id); err != nil {
t.Fatalf("failed to synchronise blocks: %v", err)
}
if imported := len(tester.ownBlocks); imported != len(tester.peerHashes[id]) {
t.Fatalf("synchronised block mismatch: have %v, want %v", imported, len(tester.peerHashes[id]))
}
// Synchronise with the best peer and make sure everything is retrieved
if err := tester.sync("peer #0"); err != nil {
t.Fatalf("failed to synchronise blocks: %v", err)
}
if imported := len(tester.ownBlocks); imported != targetBlocks+1 {
t.Fatalf("synchronised block mismatch: have %v, want %v", imported, targetBlocks+1)
}
}
// Tests that synchronising with a peer who's very slow at network IO does not
// stall the other peers in the system.
func TestSlowSynchronisation(t *testing.T) {
tester := newTester()
// Create a batch of blocks, with a slow and a full speed peer
targetCycles := 2
targetBlocks := targetCycles*blockCacheLimit - 15
targetIODelay := 500 * time.Millisecond
hashes := createHashes(targetBlocks, knownHash)
blocks := createBlocksFromHashes(hashes)
tester.newSlowPeer("fast", hashes, blocks, 0)
tester.newSlowPeer("slow", hashes, blocks, targetIODelay)
// Try to sync with the peers (pull hashes from fast)
start := time.Now()
if err := tester.sync("fast"); err != nil {
t.Fatalf("failed to synchronise blocks: %v", err)
}
if imported := len(tester.ownBlocks); imported != targetBlocks+1 {
t.Fatalf("synchronised block mismatch: have %v, want %v", imported, targetBlocks+1)
}
// Check that the slow peer got hit at most once per block-cache-size import
limit := time.Duration(targetCycles+1) * targetIODelay
if delay := time.Since(start); delay >= limit {
t.Fatalf("synchronisation exceeded delay limit: have %v, want %v", delay, limit)
}
}
// Tests that if a peer returns an invalid chain with a block pointing to a non-
// existing parent, it is correctly detected and handled.
func TestNonExistingParentAttack(t *testing.T) {
tester := newTester()
// Forge a single-link chain with a forged header
hashes := createHashes(1, knownHash)
blocks := createBlocksFromHashes(hashes)
tester.newPeer("valid", hashes, blocks)
hashes = createHashes(1, knownHash)
blocks = createBlocksFromHashes(hashes)
blocks[hashes[0]].ParentHeaderHash = unknownHash
tester.newPeer("attack", hashes, blocks)
// Try and sync with the malicious node and check that it fails
if err := tester.sync("attack"); err == nil {
t.Fatalf("block synchronization succeeded")
}
if tester.hasBlock(hashes[0]) {
t.Fatalf("tester accepted unknown-parent block: %v", blocks[hashes[0]])
}
// Try to synchronize with the valid chain and make sure it succeeds
if err := tester.sync("valid"); err != nil {
t.Fatalf("failed to synchronise blocks: %v", err)
}
if !tester.hasBlock(tester.peerHashes["valid"][0]) {
t.Fatalf("tester didn't accept known-parent block: %v", tester.peerBlocks["valid"][hashes[0]])
}
}
// Tests that if a malicious peers keeps sending us repeating hashes, we don't
// loop indefinitely.
func TestRepeatingHashAttack(t *testing.T) { // TODO: Is this thing valid??
tester := newTester()
// Create a valid chain, but drop the last link
hashes := createHashes(blockCacheLimit, knownHash)
blocks := createBlocksFromHashes(hashes)
tester.newPeer("valid", hashes, blocks)
tester.newPeer("attack", hashes[:len(hashes)-1], blocks)
// Try and sync with the malicious node
errc := make(chan error)
go func() {
errc <- tester.sync("attack")
}()
// Make sure that syncing returns and does so with a failure
select {
case <-time.After(time.Second):
t.Fatalf("synchronisation blocked")
case err := <-errc:
if err == nil {
t.Fatalf("synchronisation succeeded")
}
}
// Ensure that a valid chain can still pass sync
if err := tester.sync("valid"); err != nil {
t.Fatalf("failed to synchronise blocks: %v", err)
}
}
// Tests that if a malicious peers returns a non-existent block hash, it should
// eventually time out and the sync reattempted.
func TestNonExistingBlockAttack(t *testing.T) {
tester := newTester()
// Create a valid chain, but forge the last link
hashes := createHashes(blockCacheLimit, knownHash)
blocks := createBlocksFromHashes(hashes)
tester.newPeer("valid", hashes, blocks)
hashes[len(hashes)/2] = unknownHash
tester.newPeer("attack", hashes, blocks)
// Try and sync with the malicious node and check that it fails
if err := tester.sync("attack"); err != errPeersUnavailable {
t.Fatalf("synchronisation error mismatch: have %v, want %v", err, errPeersUnavailable)
}
// Ensure that a valid chain can still pass sync
if err := tester.sync("valid"); err != nil {
t.Fatalf("failed to synchronise blocks: %v", err)
}
}
// Tests that if a malicious peer is returning hashes in a weird order, that the
// sync throttler doesn't choke on them waiting for the valid blocks.
func TestInvalidHashOrderAttack(t *testing.T) {
tester := newTester()
// Create a valid long chain, but reverse some hashes within
hashes := createHashes(4*blockCacheLimit, knownHash)
blocks := createBlocksFromHashes(hashes)
tester.newPeer("valid", hashes, blocks)
chunk1 := make([]common.Hash, blockCacheLimit)
chunk2 := make([]common.Hash, blockCacheLimit)
copy(chunk1, hashes[blockCacheLimit:2*blockCacheLimit])
copy(chunk2, hashes[2*blockCacheLimit:3*blockCacheLimit])
copy(hashes[2*blockCacheLimit:], chunk1)
copy(hashes[blockCacheLimit:], chunk2)
tester.newPeer("attack", hashes, blocks)
// Try and sync with the malicious node and check that it fails
if err := tester.sync("attack"); err != errInvalidChain {
t.Fatalf("synchronisation error mismatch: have %v, want %v", err, errInvalidChain)
}
// Ensure that a valid chain can still pass sync
if err := tester.sync("valid"); err != nil {
t.Fatalf("failed to synchronise blocks: %v", err)
}
}
// Tests that if a malicious peer makes up a random hash chain and tries to push
// indefinitely, it actually gets caught with it.
func TestMadeupHashChainAttack(t *testing.T) {
tester := newTester()
blockSoftTTL = 100 * time.Millisecond
crossCheckCycle = 25 * time.Millisecond
// Create a long chain of hashes without backing blocks
hashes := createHashes(4*blockCacheLimit, knownHash)
blocks := createBlocksFromHashes(hashes)
tester.newPeer("valid", hashes, blocks)
tester.newPeer("attack", createHashes(1024*blockCacheLimit, knownHash), nil)
// Try and sync with the malicious node and check that it fails
if err := tester.sync("attack"); err != errCrossCheckFailed {
t.Fatalf("synchronisation error mismatch: have %v, want %v", err, errCrossCheckFailed)
}
// Ensure that a valid chain can still pass sync
if err := tester.sync("valid"); err != nil {
t.Fatalf("failed to synchronise blocks: %v", err)
}
}
// Tests that if a malicious peer makes up a random hash chain, and tries to push
// indefinitely, one hash at a time, it actually gets caught with it. The reason
// this is separate from the classical made up chain attack is that sending hashes
// one by one prevents reliable block/parent verification.
func TestMadeupHashChainDrippingAttack(t *testing.T) {
// Create a random chain of hashes to drip
hashes := createHashes(16*blockCacheLimit, knownHash)
tester := newTester()
// Try and sync with the attacker, one hash at a time
tester.maxHashFetch = 1
tester.newPeer("attack", hashes, nil)
if err := tester.sync("attack"); err != errStallingPeer {
t.Fatalf("synchronisation error mismatch: have %v, want %v", err, errStallingPeer)
}
}
// Tests that if a malicious peer makes up a random block chain, and tried to
// push indefinitely, it actually gets caught with it.
func TestMadeupBlockChainAttack(t *testing.T) {
defaultBlockTTL := blockSoftTTL
defaultCrossCheckCycle := crossCheckCycle
blockSoftTTL = 100 * time.Millisecond
crossCheckCycle = 25 * time.Millisecond
// Create a long chain of blocks and simulate an invalid chain by dropping every second
hashes := createHashes(16*blockCacheLimit, knownHash)
blocks := createBlocksFromHashes(hashes)
gapped := make([]common.Hash, len(hashes)/2)
for i := 0; i < len(gapped); i++ {
gapped[i] = hashes[2*i]
}
// Try and sync with the malicious node and check that it fails
tester := newTester()
tester.newPeer("attack", gapped, blocks)
if err := tester.sync("attack"); err != errCrossCheckFailed {
t.Fatalf("synchronisation error mismatch: have %v, want %v", err, errCrossCheckFailed)
}
// Ensure that a valid chain can still pass sync
blockSoftTTL = defaultBlockTTL
crossCheckCycle = defaultCrossCheckCycle
tester.newPeer("valid", hashes, blocks)
if err := tester.sync("valid"); err != nil {
t.Fatalf("failed to synchronise blocks: %v", err)
}
}
// Advanced form of the above forged blockchain attack, where not only does the
// attacker make up a valid hashes for random blocks, but also forges the block
// parents to point to existing hashes.
func TestMadeupParentBlockChainAttack(t *testing.T) {
tester := newTester()
defaultBlockTTL := blockSoftTTL
defaultCrossCheckCycle := crossCheckCycle
blockSoftTTL = 100 * time.Millisecond
crossCheckCycle = 25 * time.Millisecond
// Create a long chain of blocks and simulate an invalid chain by dropping every second
hashes := createHashes(16*blockCacheLimit, knownHash)
blocks := createBlocksFromHashes(hashes)
tester.newPeer("valid", hashes, blocks)
for _, block := range blocks {
block.ParentHeaderHash = knownHash // Simulate pointing to already known hash
}
tester.newPeer("attack", hashes, blocks)
// Try and sync with the malicious node and check that it fails
if err := tester.sync("attack"); err != errCrossCheckFailed {
t.Fatalf("synchronisation error mismatch: have %v, want %v", err, errCrossCheckFailed)
}
// Ensure that a valid chain can still pass sync
blockSoftTTL = defaultBlockTTL
crossCheckCycle = defaultCrossCheckCycle
if err := tester.sync("valid"); err != nil {
t.Fatalf("failed to synchronise blocks: %v", err)
}
}
// Tests that if one/multiple malicious peers try to feed a banned blockchain to
// the downloader, it will not keep refetching the same chain indefinitely, but
// gradually block pieces of it, until it's head is also blocked.
func TestBannedChainStarvationAttack(t *testing.T) {
// Create the tester and ban the selected hash
tester := newTester()
tester.downloader.banned.Add(bannedHash)
// Construct a valid chain, for it and ban the fork
hashes := createHashes(8*blockCacheLimit, knownHash)
blocks := createBlocksFromHashes(hashes)
tester.newPeer("valid", hashes, blocks)
fork := len(hashes)/2 - 23
hashes = append(createHashes(4*blockCacheLimit, bannedHash), hashes[fork:]...)
blocks = createBlocksFromHashes(hashes)
tester.newPeer("attack", hashes, blocks)
// Iteratively try to sync, and verify that the banned hash list grows until
// the head of the invalid chain is blocked too.
for banned := tester.downloader.banned.Size(); ; {
// Try to sync with the attacker, check hash chain failure
if err := tester.sync("attack"); err != errInvalidChain {
if tester.downloader.banned.Has(hashes[0]) && err == errBannedHead {
break
}
t.Fatalf("synchronisation error mismatch: have %v, want %v", err, errInvalidChain)
}
// Check that the ban list grew with at least 1 new item, or all banned
bans := tester.downloader.banned.Size()
if bans < banned+1 {
t.Fatalf("ban count mismatch: have %v, want %v+", bans, banned+1)
}
banned = bans
}
// Check that after banning an entire chain, bad peers get dropped
if err := tester.newPeer("new attacker", hashes, blocks); err != errBannedHead {
t.Fatalf("peer registration mismatch: have %v, want %v", err, errBannedHead)
}
if peer := tester.downloader.peers.Peer("new attacker"); peer != nil {
t.Fatalf("banned attacker registered: %v", peer)
}
// Ensure that a valid chain can still pass sync
if err := tester.sync("valid"); err != nil {
t.Fatalf("failed to synchronise blocks: %v", err)
}
}
// Tests that if a peer sends excessively many/large invalid chains that are
// gradually banned, it will have an upper limit on the consumed memory and also
// the origin bad hashes will not be evacuated.
func TestBannedChainMemoryExhaustionAttack(t *testing.T) {
// Create the tester and ban the selected hash
tester := newTester()
tester.downloader.banned.Add(bannedHash)
// Reduce the test size a bit
defaultMaxBlockFetch := MaxBlockFetch
defaultMaxBannedHashes := maxBannedHashes
MaxBlockFetch = 4
maxBannedHashes = 256
// Construct a banned chain with more chunks than the ban limit
hashes := createHashes(8*blockCacheLimit, knownHash)
blocks := createBlocksFromHashes(hashes)
tester.newPeer("valid", hashes, blocks)
fork := len(hashes)/2 - 23
hashes = append(createHashes(maxBannedHashes*MaxBlockFetch, bannedHash), hashes[fork:]...)
blocks = createBlocksFromHashes(hashes)
tester.newPeer("attack", hashes, blocks)
// Iteratively try to sync, and verify that the banned hash list grows until
// the head of the invalid chain is blocked too.
for {
// Try to sync with the attacker, check hash chain failure
if err := tester.sync("attack"); err != errInvalidChain {
t.Fatalf("synchronisation error mismatch: have %v, want %v", err, errInvalidChain)
}
// Short circuit if the entire chain was banned
if tester.downloader.banned.Has(hashes[0]) {
break
}
// Otherwise ensure we never exceed the memory allowance and the hard coded bans are untouched
if bans := tester.downloader.banned.Size(); bans > maxBannedHashes {
t.Fatalf("ban cap exceeded: have %v, want max %v", bans, maxBannedHashes)
}
for hash, _ := range core.BadHashes {
if !tester.downloader.banned.Has(hash) {
t.Fatalf("hard coded ban evacuated: %x", hash)
}
}
}
// Ensure that a valid chain can still pass sync
MaxBlockFetch = defaultMaxBlockFetch
maxBannedHashes = defaultMaxBannedHashes
if err := tester.sync("valid"); err != nil {
t.Fatalf("failed to synchronise blocks: %v", err)
}
}
// Tests that misbehaving peers are disconnected, whilst behaving ones are not.
func TestHashAttackerDropping(t *testing.T) {
// Define the disconnection requirement for individual hash fetch errors
tests := []struct {
result error
drop bool
}{
{nil, false}, // Sync succeeded, all is well
{errBusy, false}, // Sync is already in progress, no problem
{errUnknownPeer, false}, // Peer is unknown, was already dropped, don't double drop
{errBadPeer, true}, // Peer was deemed bad for some reason, drop it
{errStallingPeer, true}, // Peer was detected to be stalling, drop it
{errBannedHead, true}, // Peer's head hash is a known bad hash, drop it
{errNoPeers, false}, // No peers to download from, soft race, no issue
{errPendingQueue, false}, // There are blocks still cached, wait to exhaust, no issue
{errTimeout, true}, // No hashes received in due time, drop the peer
{errEmptyHashSet, true}, // No hashes were returned as a response, drop as it's a dead end
{errPeersUnavailable, true}, // Nobody had the advertised blocks, drop the advertiser
{errInvalidChain, true}, // Hash chain was detected as invalid, definitely drop
{errCrossCheckFailed, true}, // Hash-origin failed to pass a block cross check, drop
{errCancelHashFetch, false}, // Synchronisation was canceled, origin may be innocent, don't drop
{errCancelBlockFetch, false}, // Synchronisation was canceled, origin may be innocent, don't drop
{errCancelChainImport, false}, // Synchronisation was canceled, origin may be innocent, don't drop
}
// Run the tests and check disconnection status
tester := newTester()
for i, tt := range tests {
// Register a new peer and ensure it's presence
id := fmt.Sprintf("test %d", i)
if err := tester.newPeer(id, []common.Hash{knownHash}, nil); err != nil {
t.Fatalf("test %d: failed to register new peer: %v", i, err)
}
if _, ok := tester.peerHashes[id]; !ok {
t.Fatalf("test %d: registered peer not found", i)
}
// Simulate a synchronisation and check the required result
tester.downloader.synchroniseMock = func(string, common.Hash) error { return tt.result }
tester.downloader.Synchronise(id, knownHash)
if _, ok := tester.peerHashes[id]; !ok != tt.drop {
t.Errorf("test %d: peer drop mismatch for %v: have %v, want %v", i, tt.result, !ok, tt.drop)
}
}
}
// Tests that feeding bad blocks will result in a peer drop.
func TestBlockAttackerDropping(t *testing.T) {
// Define the disconnection requirement for individual block import errors
tests := []struct {
failure bool
drop bool
}{{true, true}, {false, false}}
// Run the tests and check disconnection status
tester := newTester()
for i, tt := range tests {
// Register a new peer and ensure it's presence
id := fmt.Sprintf("test %d", i)
if err := tester.newPeer(id, []common.Hash{common.Hash{}}, nil); err != nil {
t.Fatalf("test %d: failed to register new peer: %v", i, err)
}
if _, ok := tester.peerHashes[id]; !ok {
t.Fatalf("test %d: registered peer not found", i)
}
// Assemble a good or bad block, depending of the test
raw := createBlock(1, knownHash, common.Hash{})
if tt.failure {
raw = createBlock(1, unknownHash, common.Hash{})
}
block := &Block{OriginPeer: id, RawBlock: raw}
// Simulate block processing and check the result
tester.downloader.queue.blockCache[0] = block
tester.downloader.process()
if _, ok := tester.peerHashes[id]; !ok != tt.drop {
t.Errorf("test %d: peer drop mismatch for %v: have %v, want %v", i, tt.failure, !ok, tt.drop)
}
}
}
|