package downloader
import (
"encoding/binary"
"math/big"
"testing"
"time"
"github.com/ethereum/go-ethereum/common"
"github.com/ethereum/go-ethereum/core/types"
"github.com/ethereum/go-ethereum/event"
)
var (
knownHash = common.Hash{1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0}
unknownHash = common.Hash{9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9}
bannedHash = common.Hash{5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5}
)
func createHashes(start, amount int) (hashes []common.Hash) {
hashes = make([]common.Hash, amount+1)
hashes[len(hashes)-1] = knownHash
for i := range hashes[:len(hashes)-1] {
binary.BigEndian.PutUint64(hashes[i][:8], uint64(start+i+2))
}
return
}
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
}
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
hashes []common.Hash // Chain of hashes simulating
blocks map[common.Hash]*types.Block // Blocks associated with the hashes
chain []common.Hash // Block-chain being constructed
maxHashFetch int // Overrides the maximum number of retrieved hashes
t *testing.T
done chan bool
activePeerId string
}
func newTester(t *testing.T, hashes []common.Hash, blocks map[common.Hash]*types.Block) *downloadTester {
tester := &downloadTester{
t: t,
hashes: hashes,
blocks: blocks,
chain: []common.Hash{knownHash},
done: make(chan bool),
}
var mux event.TypeMux
downloader := New(&mux, tester.hasBlock, tester.getBlock)
tester.downloader = downloader
return tester
}
// sync is a simple wrapper around the downloader to start synchronisation and
// block until it returns
func (dl *downloadTester) sync(peerId string, head common.Hash) error {
dl.activePeerId = peerId
return dl.downloader.Synchronise(peerId, head)
}
// syncTake is starts synchronising with a remote peer, but concurrently it also
// starts fetching blocks that the downloader retrieved. IT blocks until both go
// routines terminate.
func (dl *downloadTester) syncTake(peerId string, head common.Hash) ([]*Block, error) {
// Start a block collector to take blocks as they become available
done := make(chan struct{})
took := []*Block{}
go func() {
for running := true; running; {
select {
case <-done:
running = false
default:
time.Sleep(time.Millisecond)
}
// Take a batch of blocks and accumulate
took = append(took, dl.downloader.TakeBlocks()...)
}
done <- struct{}{}
}()
// Start the downloading, sync the taker and return
err := dl.sync(peerId, head)
done <- struct{}{}
<-done
return took, err
}
func (dl *downloadTester) hasBlock(hash common.Hash) bool {
for _, h := range dl.chain {
if h == hash {
return true
}
}
return false
}
func (dl *downloadTester) getBlock(hash common.Hash) *types.Block {
return dl.blocks[knownHash]
}
// getHashes retrieves a batch of hashes for reconstructing the chain.
func (dl *downloadTester) getHashes(head common.Hash) error {
limit := MaxHashFetch
if dl.maxHashFetch > 0 {
limit = dl.maxHashFetch
}
// Gather the next batch of hashes
hashes := make([]common.Hash, 0, limit)
for i, hash := range dl.hashes {
if hash == head {
i++
for len(hashes) < cap(hashes) && i < len(dl.hashes) {
hashes = append(hashes, dl.hashes[i])
i++
}
break
}
}
// Delay delivery a bit to allow attacks to unfold
id := dl.activePeerId
go func() {
time.Sleep(time.Millisecond)
dl.downloader.DeliverHashes(id, hashes)
}()
return nil
}
func (dl *downloadTester) getBlocks(id string) func([]common.Hash) error {
return func(hashes []common.Hash) error {
blocks := make([]*types.Block, 0, len(hashes))
for _, hash := range hashes {
if block, ok := dl.blocks[hash]; ok {
blocks = append(blocks, block)
}
}
go dl.downloader.DeliverBlocks(id, blocks)
return nil
}
}
func (dl *downloadTester) newPeer(id string, td *big.Int, hash common.Hash) {
dl.downloader.RegisterPeer(id, hash, dl.getHashes, dl.getBlocks(id))
}
// 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(0, targetBlocks)
blocks := createBlocksFromHashes(hashes)
tester := newTester(t, hashes, blocks)
tester.newPeer("peer", big.NewInt(10000), hashes[0])
// Synchronise with the peer and make sure all blocks were retrieved
if err := tester.sync("peer", hashes[0]); err != nil {
t.Fatalf("failed to synchronise blocks: %v", err)
}
if queued := len(tester.downloader.queue.blockCache); queued != targetBlocks {
t.Fatalf("synchronised block mismatch: have %v, want %v", queued, targetBlocks)
}
}
// Tests that the synchronized blocks can be correctly retrieved.
func TestBlockTaking(t *testing.T) {
// Create a small enough block chain to download and the tester
targetBlocks := blockCacheLimit - 15
hashes := createHashes(0, targetBlocks)
blocks := createBlocksFromHashes(hashes)
tester := newTester(t, hashes, blocks)
tester.newPeer("peer", big.NewInt(10000), hashes[0])
// Synchronise with the peer and test block retrieval
if err := tester.sync("peer", hashes[0]); err != nil {
t.Fatalf("failed to synchronise blocks: %v", err)
}
if took := tester.downloader.TakeBlocks(); len(took) != targetBlocks {
t.Fatalf("took block mismatch: have %v, want %v", len(took), targetBlocks)
}
}
// Tests that an inactive downloader will not accept incoming hashes and blocks.
func TestInactiveDownloader(t *testing.T) {
// Create a small enough block chain to download and the tester
targetBlocks := blockCacheLimit - 15
hashes := createHashes(0, targetBlocks)
blocks := createBlocksFromHashSet(createHashSet(hashes))
tester := newTester(t, nil, nil)
// Check that neither hashes nor blocks are accepted
if err := tester.downloader.DeliverHashes("bad peer", hashes); err != errNoSyncActive {
t.Errorf("error mismatch: have %v, want %v", err, errNoSyncActive)
}
if err := tester.downloader.DeliverBlocks("bad peer", blocks); 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(0, targetBlocks)
blocks := createBlocksFromHashes(hashes)
tester := newTester(t, hashes, blocks)
tester.newPeer("peer", big.NewInt(10000), hashes[0])
// Synchronise with the peer, but cancel afterwards
if err := tester.sync("peer", hashes[0]); err != nil {
t.Fatalf("failed to synchronise blocks: %v", err)
}
if !tester.downloader.Cancel() {
t.Fatalf("cancel operation failed")
}
// Make sure the queue reports empty and no blocks can be taken
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)
}
if took := tester.downloader.TakeBlocks(); len(took) != 0 {
t.Errorf("taken blocks mismatch: have %d, want %d", len(took), 0)
}
}
// 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(0, targetBlocks)
blocks := createBlocksFromHashes(hashes)
tester := newTester(t, hashes, blocks)
tester.newPeer("peer", big.NewInt(10000), hashes[0])
// Start a synchronisation concurrently
errc := make(chan error)
go func() {
errc <- tester.sync("peer", hashes[0])
}()
// Iteratively take some blocks, always checking the retrieval count
for total := 0; total < targetBlocks; {
// Sleep a bit for sync to complete
time.Sleep(500 * time.Millisecond)
// Fetch the next batch of blocks
took := tester.downloader.TakeBlocks()
if len(took) != blockCacheLimit {
t.Fatalf("block count mismatch: have %v, want %v", len(took), blockCacheLimit)
}
total += len(took)
if total > targetBlocks {
t.Fatalf("target block count mismatch: have %v, want %v", total, targetBlocks)
}
}
if err := <-errc; err != nil {
t.Fatalf("block synchronization failed: %v", err)
}
}
// 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) {
// Forge a single-link chain with a forged header
hashes := createHashes(0, 1)
blocks := createBlocksFromHashes(hashes)
forged := blocks[hashes[0]]
forged.ParentHeaderHash = unknownHash
// Try and sync with the malicious node and check that it fails
tester := newTester(t, hashes, blocks)
tester.newPeer("attack", big.NewInt(10000), hashes[0])
if err := tester.sync("attack", hashes[0]); err != nil {
t.Fatalf("failed to synchronise blocks: %v", err)
}
bs := tester.downloader.TakeBlocks()
if len(bs) != 1 {
t.Fatalf("retrieved block mismatch: have %v, want %v", len(bs), 1)
}
if tester.hasBlock(bs[0].RawBlock.ParentHash()) {
t.Fatalf("tester knows about the unknown hash")
}
tester.downloader.Cancel()
// Reconstruct a valid chain, and try to synchronize with it
forged.ParentHeaderHash = knownHash
tester.newPeer("valid", big.NewInt(20000), hashes[0])
if err := tester.sync("valid", hashes[0]); err != nil {
t.Fatalf("failed to synchronise blocks: %v", err)
}
bs = tester.downloader.TakeBlocks()
if len(bs) != 1 {
t.Fatalf("retrieved block mismatch: have %v, want %v", len(bs), 1)
}
if !tester.hasBlock(bs[0].RawBlock.ParentHash()) {
t.Fatalf("tester doesn't know about the origin hash")
}
}
// Tests that if a malicious peers keeps sending us repeating hashes, we don't
// loop indefinitely.
func TestRepeatingHashAttack(t *testing.T) {
// Create a valid chain, but drop the last link
hashes := createHashes(0, blockCacheLimit)
blocks := createBlocksFromHashes(hashes)
forged := hashes[:len(hashes)-1]
// Try and sync with the malicious node
tester := newTester(t, forged, blocks)
tester.newPeer("attack", big.NewInt(10000), forged[0])
errc := make(chan error)
go func() {
errc <- tester.sync("attack", hashes[0])
}()
// 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
tester.hashes = hashes
tester.newPeer("valid", big.NewInt(20000), hashes[0])
if err := tester.sync("valid", hashes[0]); 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) {
// Create a valid chain, but forge the last link
hashes := createHashes(0, blockCacheLimit)
blocks := createBlocksFromHashes(hashes)
origin := hashes[len(hashes)/2]
hashes[len(hashes)/2] = unknownHash
// Try and sync with the malicious node and check that it fails
tester := newTester(t, hashes, blocks)
tester.newPeer("attack", big.NewInt(10000), hashes[0])
if err := tester.sync("attack", hashes[0]); err != errPeersUnavailable {
t.Fatalf("synchronisation error mismatch: have %v, want %v", err, errPeersUnavailable)
}
// Ensure that a valid chain can still pass sync
hashes[len(hashes)/2] = origin
tester.newPeer("valid", big.NewInt(20000), hashes[0])
if err := tester.sync("valid", hashes[0]); 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) {
// Create a valid long chain, but reverse some hashes within
hashes := createHashes(0, 4*blockCacheLimit)
blocks := createBlocksFromHashes(hashes)
chunk1 := make([]common.Hash, blockCacheLimit)
chunk2 := make([]common.Hash, blockCacheLimit)
copy(chunk1, hashes[blockCacheLimit:2*blockCacheLimit])
copy(chunk2, hashes[2*blockCacheLimit:3*blockCacheLimit])
reverse := make([]common.Hash, len(hashes))
copy(reverse, hashes)
copy(reverse[2*blockCacheLimit:], chunk1)
copy(reverse[blockCacheLimit:], chunk2)
// Try and sync with the malicious node and check that it fails
tester := newTester(t, reverse, blocks)
tester.newPeer("attack", big.NewInt(10000), reverse[0])
if _, err := tester.syncTake("attack", reverse[0]); err != ErrInvalidChain {
t.Fatalf("synchronisation error mismatch: have %v, want %v", err, ErrInvalidChain)
}
// Ensure that a valid chain can still pass sync
tester.hashes = hashes
tester.newPeer("valid", big.NewInt(20000), hashes[0])
if _, err := tester.syncTake("valid", hashes[0]); 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) {
blockSoftTTL = 100 * time.Millisecond
crossCheckCycle = 25 * time.Millisecond
// Create a long chain of hashes without backing blocks
hashes := createHashes(0, 1024*blockCacheLimit)
// Try and sync with the malicious node and check that it fails
tester := newTester(t, hashes, nil)
tester.newPeer("attack", big.NewInt(10000), hashes[0])
if _, err := tester.syncTake("attack", hashes[0]); err != ErrCrossCheckFailed {
t.Fatalf("synchronisation error mismatch: have %v, want %v", err, ErrCrossCheckFailed)
}
}
// 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(0, 16*blockCacheLimit)
tester := newTester(t, hashes, nil)
// Try and sync with the attacker, one hash at a time
tester.maxHashFetch = 1
tester.newPeer("attack", big.NewInt(10000), hashes[0])
if _, err := tester.syncTake("attack", hashes[0]); 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(0, 16*blockCacheLimit)
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(t, gapped, blocks)
tester.newPeer("attack", big.NewInt(10000), gapped[0])
if _, err := tester.syncTake("attack", gapped[0]); 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.hashes = hashes
tester.newPeer("valid", big.NewInt(20000), hashes[0])
if _, err := tester.syncTake("valid", hashes[0]); 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) {
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(0, 16*blockCacheLimit)
blocks := createBlocksFromHashes(hashes)
forges := createBlocksFromHashes(hashes)
for hash, block := range forges {
block.ParentHeaderHash = hash // Simulate pointing to already known hash
}
// Try and sync with the malicious node and check that it fails
tester := newTester(t, hashes, forges)
tester.newPeer("attack", big.NewInt(10000), hashes[0])
if _, err := tester.syncTake("attack", hashes[0]); 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.blocks = blocks
tester.newPeer("valid", big.NewInt(20000), hashes[0])
if _, err := tester.syncTake("valid", hashes[0]); 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) {
// Construct a valid chain, but ban one of the hashes in it
hashes := createHashes(0, 8*blockCacheLimit)
hashes[len(hashes)/2+23] = bannedHash // weird index to have non multiple of ban chunk size
blocks := createBlocksFromHashes(hashes)
// Create the tester and ban the selected hash
tester := newTester(t, hashes, blocks)
tester.downloader.banned.Add(bannedHash)
// Iteratively try to sync, and verify that the banned hash list grows until
// the head of the invalid chain is blocked too.
tester.newPeer("attack", big.NewInt(10000), hashes[0])
for banned := tester.downloader.banned.Size(); ; {
// Try to sync with the attacker, check hash chain failure
if _, err := tester.syncTake("attack", hashes[0]); err != ErrInvalidChain {
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 {
if tester.downloader.banned.Has(hashes[0]) {
break
}
t.Fatalf("ban count mismatch: have %v, want %v+", bans, banned+1)
}
banned = bans
}
}
