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Merge pull request #1153 from karalabe/downloader-banned-starvation-attack

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eth/downloader: gather and ban hashes from invalid chains
This commit is contained in:
Jeffrey Wilcke 2015-06-09 03:45:41 -07:00
commit 087949227c
6 changed files with 351 additions and 213 deletions
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165
eth/downloader/downloader.go
View File

@ -1,36 +1,33 @@
package downloader
import (
"bytes"
"errors"
"math/rand"
"sync"
"sync/atomic"
"time"
"gopkg.in/fatih/set.v0"
"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"
"github.com/ethereum/go-ethereum/logger"
"github.com/ethereum/go-ethereum/logger/glog"
"gopkg.in/fatih/set.v0"
)
const (
var (
MinHashFetch = 512 // Minimum amount of hashes to not consider a peer stalling
MaxHashFetch = 2048 // Amount of hashes to be fetched per retrieval request
MaxBlockFetch = 128 // Amount of blocks to be fetched per retrieval request
peerCountTimeout = 12 * time.Second // Amount of time it takes for the peer handler to ignore minDesiredPeerCount
hashTTL = 5 * time.Second // Time it takes for a hash request to time out
)
var (
blockSoftTTL = 3 * time.Second // Request completion threshold for increasing or decreasing a peer's bandwidth
blockHardTTL = 3 * blockSoftTTL // Maximum time allowance before a block request is considered expired
crossCheckCycle = time.Second // Period after which to check for expired cross checks
minDesiredPeerCount = 5 // Amount of peers desired to start syncing
maxBannedHashes = 4096 // Number of bannable hashes before phasing old ones out
)
var (
@ -39,6 +36,7 @@ var (
errUnknownPeer = errors.New("peer is unknown or unhealthy")
ErrBadPeer = errors.New("action from bad peer ignored")
ErrStallingPeer = errors.New("peer is stalling")
errBannedHead = errors.New("peer head hash already banned")
errNoPeers = errors.New("no peers to keep download active")
ErrPendingQueue = errors.New("pending items in queue")
ErrTimeout = errors.New("timeout")
@ -75,11 +73,10 @@ type crossCheck struct {
type Downloader struct {
mux *event.TypeMux
mu sync.RWMutex
queue *queue // Scheduler for selecting the hashes to download
peers *peerSet // Set of active peers from which download can proceed
checks map[common.Hash]*crossCheck // Pending cross checks to verify a hash chain
banned *set.SetNonTS // Set of hashes we've received and banned
banned *set.Set // Set of hashes we've received and banned
// Callbacks
hasBlock hashCheckFn
@ -117,7 +114,7 @@ func New(mux *event.TypeMux, hasBlock hashCheckFn, getBlock getBlockFn) *Downloa
blockCh: make(chan blockPack, 1),
}
// Inject all the known bad hashes
downloader.banned = set.NewNonTS()
downloader.banned = set.New()
for hash, _ := range core.BadHashes {
downloader.banned.Add(hash)
}
@ -136,6 +133,12 @@ func (d *Downloader) Synchronising() bool {
// RegisterPeer injects a new download peer into the set of block source to be
// used for fetching hashes and blocks from.
func (d *Downloader) RegisterPeer(id string, head common.Hash, getHashes hashFetcherFn, getBlocks blockFetcherFn) error {
// If the peer wants to send a banned hash, reject
if d.banned.Has(head) {
glog.V(logger.Debug).Infoln("Register rejected, head hash banned:", id)
return errBannedHead
}
// Otherwise try to construct and register the peer
glog.V(logger.Detail).Infoln("Registering peer", id)
if err := d.peers.Register(newPeer(id, head, getHashes, getBlocks)); err != nil {
glog.V(logger.Error).Infoln("Register failed:", err)
@ -165,6 +168,10 @@ func (d *Downloader) Synchronise(id string, hash common.Hash) error {
}
defer atomic.StoreInt32(&d.synchronising, 0)
// If the head hash is banned, terminate immediately
if d.banned.Has(hash) {
return ErrInvalidChain
}
// Post a user notification of the sync (only once per session)
if atomic.CompareAndSwapInt32(&d.notified, 0, 1) {
glog.V(logger.Info).Infoln("Block synchronisation started")
@ -198,6 +205,8 @@ func (d *Downloader) TakeBlocks() []*Block {
return d.queue.TakeBlocks()
}
// Has checks if the downloader knows about a particular hash, meaning that its
// either already downloaded of pending retrieval.
func (d *Downloader) Has(hash common.Hash) bool {
return d.queue.Has(hash)
}
@ -291,9 +300,14 @@ func (d *Downloader) fetchHashes(p *peer, h common.Hash) error {
glog.V(logger.Debug).Infof("Peer (%s) responded with empty hash set", active.id)
return ErrEmptyHashSet
}
for _, hash := range hashPack.hashes {
for index, hash := range hashPack.hashes {
if d.banned.Has(hash) {
glog.V(logger.Debug).Infof("Peer (%s) sent a known invalid chain", active.id)
d.queue.Insert(hashPack.hashes[:index+1])
if err := d.banBlocks(active.id, hash); err != nil {
glog.V(logger.Debug).Infof("Failed to ban batch of blocks: %v", err)
}
return ErrInvalidChain
}
}
@ -334,12 +348,12 @@ func (d *Downloader) fetchHashes(p *peer, h common.Hash) error {
active.getHashes(head)
continue
}
// We're done, allocate the download cache and proceed pulling the blocks
// We're done, prepare the download cache and proceed pulling the blocks
offset := 0
if block := d.getBlock(head); block != nil {
offset = int(block.NumberU64() + 1)
}
d.queue.Alloc(offset)
d.queue.Prepare(offset)
finished = true
case blockPack := <-d.blockCh:
@ -401,21 +415,26 @@ func (d *Downloader) fetchBlocks() error {
glog.V(logger.Debug).Infoln("Downloading", d.queue.Pending(), "block(s)")
start := time.Now()
// default ticker for re-fetching blocks every now and then
// Start a ticker to continue throttled downloads and check for bad peers
ticker := time.NewTicker(20 * time.Millisecond)
defer ticker.Stop()
out:
for {
select {
case <-d.cancelCh:
return errCancelBlockFetch
case <-d.hashCh:
// Out of bounds hashes received, ignore them
case blockPack := <-d.blockCh:
// Short circuit if it's a stale cross check
if len(blockPack.blocks) == 1 {
block := blockPack.blocks[0]
if _, ok := d.checks[block.Hash()]; ok {
delete(d.checks, block.Hash())
continue
break
}
}
// If the peer was previously banned and failed to deliver it's pack
@ -463,34 +482,25 @@ out:
glog.V(logger.Detail).Infof("%s: delivery partially failed: %v", peer, err)
}
}
case <-ticker.C:
// Check for bad peers. Bad peers may indicate a peer not responding
// to a `getBlocks` message. A timeout of 5 seconds is set. Peers
// that badly or poorly behave are removed from the peer set (not banned).
// Bad peers are excluded from the available peer set and therefor won't be
// reused. XXX We could re-introduce peers after X time.
// Short circuit if we lost all our peers
if d.peers.Len() == 0 {
return errNoPeers
}
// Check for block request timeouts and demote the responsible peers
badPeers := d.queue.Expire(blockHardTTL)
for _, pid := range badPeers {
// XXX We could make use of a reputation system here ranking peers
// in their performance
// 1) Time for them to respond;
// 2) Measure their speed;
// 3) Amount and availability.
if peer := d.peers.Peer(pid); peer != nil {
peer.Demote()
glog.V(logger.Detail).Infof("%s: block delivery timeout", peer)
}
}
// After removing bad peers make sure we actually have sufficient peer left to keep downloading
if d.peers.Len() == 0 {
return errNoPeers
}
// If there are unrequested hashes left start fetching
// from the available peers.
// If there are unrequested hashes left start fetching from the available peers
if d.queue.Pending() > 0 {
// Throttle the download if block cache is full and waiting processing
if d.queue.Throttle() {
continue
break
}
// Send a download request to all idle peers, until throttled
idlePeers := d.peers.IdlePeers()
@ -501,7 +511,7 @@ out:
}
// Get a possible chunk. If nil is returned no chunk
// could be returned due to no hashes available.
request := d.queue.Reserve(peer)
request := d.queue.Reserve(peer, peer.Capacity())
if request == nil {
continue
}
@ -531,10 +541,95 @@ out:
}
}
glog.V(logger.Detail).Infoln("Downloaded block(s) in", time.Since(start))
return nil
}
// banBlocks retrieves a batch of blocks from a peer feeding us invalid hashes,
// and bans the head of the retrieved batch.
//
// This method only fetches one single batch as the goal is not ban an entire
// (potentially long) invalid chain - wasting a lot of time in the meanwhile -,
// but rather to gradually build up a blacklist if the peer keeps reconnecting.
func (d *Downloader) banBlocks(peerId string, head common.Hash) error {
glog.V(logger.Debug).Infof("Banning a batch out of %d blocks from %s", d.queue.Pending(), peerId)
// Ask the peer being banned for a batch of blocks from the banning point
peer := d.peers.Peer(peerId)
if peer == nil {
return nil
}
request := d.queue.Reserve(peer, MaxBlockFetch)
if request == nil {
return nil
}
if err := peer.Fetch(request); err != nil {
return err
}
// Wait a bit for the reply to arrive, and ban if done so
timeout := time.After(blockHardTTL)
for {
select {
case <-d.cancelCh:
return errCancelBlockFetch
case <-timeout:
return ErrTimeout
case <-d.hashCh:
// Out of bounds hashes received, ignore them
case blockPack := <-d.blockCh:
blocks := blockPack.blocks
// Short circuit if it's a stale cross check
if len(blocks) == 1 {
block := blocks[0]
if _, ok := d.checks[block.Hash()]; ok {
delete(d.checks, block.Hash())
break
}
}
// Short circuit if it's not from the peer being banned
if blockPack.peerId != peerId {
break
}
// Short circuit if no blocks were returned
if len(blocks) == 0 {
return errors.New("no blocks returned to ban")
}
// Reconstruct the original chain order and ensure we're banning the correct blocks
types.BlockBy(types.Number).Sort(blocks)
if bytes.Compare(blocks[0].Hash().Bytes(), head.Bytes()) != 0 {
return errors.New("head block not the banned one")
}
index := 0
for _, block := range blocks[1:] {
if bytes.Compare(block.ParentHash().Bytes(), blocks[index].Hash().Bytes()) != 0 {
break
}
index++
}
// Ban the head hash and phase out any excess
d.banned.Add(blocks[index].Hash())
for d.banned.Size() > maxBannedHashes {
var evacuate common.Hash
d.banned.Each(func(item interface{}) bool {
// Skip any hard coded bans
if core.BadHashes[item.(common.Hash)] {
return true
}
evacuate = item.(common.Hash)
return false
})
d.banned.Remove(evacuate)
}
glog.V(logger.Debug).Infof("Banned %d blocks from: %s", index+1, peerId)
return nil
}
}
}
// DeliverBlocks injects a new batch of blocks received from a remote node.
// This is usually invoked through the BlocksMsg by the protocol handler.
func (d *Downloader) DeliverBlocks(id string, blocks []*types.Block) error {

355
eth/downloader/downloader_test.go
View File

@ -7,6 +7,7 @@ import (
"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"
)
@ -14,6 +15,7 @@ import (
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) {
@ -21,7 +23,7 @@ func createHashes(start, amount int) (hashes []common.Hash) {
hashes[len(hashes)-1] = knownHash
for i := range hashes[:len(hashes)-1] {
binary.BigEndian.PutUint64(hashes[i][:8], uint64(i+2))
binary.BigEndian.PutUint64(hashes[i][:8], uint64(start+i+2))
}
return
}
@ -56,7 +58,6 @@ type downloadTester struct {
maxHashFetch int // Overrides the maximum number of retrieved hashes
t *testing.T
pcount int
done chan bool
activePeerId string
}
@ -114,12 +115,6 @@ func (dl *downloadTester) syncTake(peerId string, head common.Hash) ([]*Block, e
return took, err
}
func (dl *downloadTester) insertBlocks(blocks types.Blocks) {
for _, block := range blocks {
dl.chain = append(dl.chain, block.Hash())
}
}
func (dl *downloadTester) hasBlock(hash common.Hash) bool {
for _, h := range dl.chain {
if h == hash {
@ -174,158 +169,131 @@ func (dl *downloadTester) getBlocks(id string) func([]common.Hash) error {
}
}
func (dl *downloadTester) newPeer(id string, td *big.Int, hash common.Hash) {
dl.pcount++
dl.downloader.RegisterPeer(id, hash, dl.getHashes, dl.getBlocks(id))
// newPeer registers a new block download source into the syncer.
func (dl *downloadTester) newPeer(id string, td *big.Int, hash common.Hash) error {
return dl.downloader.RegisterPeer(id, hash, dl.getHashes, dl.getBlocks(id))
}
func (dl *downloadTester) badBlocksPeer(id string, td *big.Int, hash common.Hash) {
dl.pcount++
// This bad peer never returns any blocks
dl.downloader.RegisterPeer(id, hash, dl.getHashes, func([]common.Hash) error {
return nil
})
}
func TestDownload(t *testing.T) {
minDesiredPeerCount = 4
blockHardTTL = 1 * time.Second
targetBlocks := 1000
// 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])
tester.newPeer("peer1", big.NewInt(10000), hashes[0])
tester.newPeer("peer2", big.NewInt(0), common.Hash{})
tester.badBlocksPeer("peer3", big.NewInt(0), common.Hash{})
tester.badBlocksPeer("peer4", big.NewInt(0), common.Hash{})
tester.activePeerId = "peer1"
err := tester.sync("peer1", hashes[0])
if err != nil {
t.Error("download error", err)
}
inqueue := len(tester.downloader.queue.blockCache)
if inqueue != targetBlocks {
t.Error("expected", targetBlocks, "have", inqueue)
}
}
func TestMissing(t *testing.T) {
targetBlocks := 1000
hashes := createHashes(0, 1000)
extraHashes := createHashes(1001, 1003)
blocks := createBlocksFromHashes(append(extraHashes, hashes...))
tester := newTester(t, hashes, blocks)
tester.newPeer("peer1", big.NewInt(10000), hashes[len(hashes)-1])
hashes = append(extraHashes, hashes[:len(hashes)-1]...)
tester.newPeer("peer2", big.NewInt(0), common.Hash{})
err := tester.sync("peer1", hashes[0])
if err != nil {
t.Error("download error", err)
}
inqueue := len(tester.downloader.queue.blockCache)
if inqueue != targetBlocks {
t.Error("expected", targetBlocks, "have", inqueue)
}
}
func TestTaking(t *testing.T) {
minDesiredPeerCount = 4
blockHardTTL = 1 * time.Second
targetBlocks := 1000
hashes := createHashes(0, targetBlocks)
blocks := createBlocksFromHashes(hashes)
tester := newTester(t, hashes, blocks)
tester.newPeer("peer1", big.NewInt(10000), hashes[0])
tester.newPeer("peer2", big.NewInt(0), common.Hash{})
tester.badBlocksPeer("peer3", big.NewInt(0), common.Hash{})
tester.badBlocksPeer("peer4", big.NewInt(0), common.Hash{})
err := tester.sync("peer1", hashes[0])
if err != nil {
t.Error("download error", err)
}
bs := tester.downloader.TakeBlocks()
if len(bs) != targetBlocks {
t.Error("retrieved block mismatch: have %v, want %v", len(bs), targetBlocks)
}
}
func TestInactiveDownloader(t *testing.T) {
targetBlocks := 1000
hashes := createHashes(0, targetBlocks)
blocks := createBlocksFromHashSet(createHashSet(hashes))
tester := newTester(t, hashes, nil)
err := tester.downloader.DeliverHashes("bad peer 001", hashes)
if err != errNoSyncActive {
t.Error("expected no sync error, got", err)
}
err = tester.downloader.DeliverBlocks("bad peer 001", blocks)
if err != errNoSyncActive {
t.Error("expected no sync error, got", err)
}
}
func TestCancel(t *testing.T) {
minDesiredPeerCount = 4
blockHardTTL = 1 * time.Second
targetBlocks := 1000
hashes := createHashes(0, targetBlocks)
blocks := createBlocksFromHashes(hashes)
tester := newTester(t, hashes, blocks)
tester.newPeer("peer1", big.NewInt(10000), hashes[0])
err := tester.sync("peer1", hashes[0])
if err != nil {
t.Error("download error", err)
}
if !tester.downloader.Cancel() {
t.Error("cancel operation unsuccessfull")
}
hashSize, blockSize := tester.downloader.queue.Size()
if hashSize > 0 || blockSize > 0 {
t.Error("block (", blockSize, ") or hash (", hashSize, ") not 0")
}
}
func TestThrottling(t *testing.T) {
minDesiredPeerCount = 4
blockHardTTL = 1 * time.Second
targetBlocks := 16 * blockCacheLimit
hashes := createHashes(0, targetBlocks)
blocks := createBlocksFromHashes(hashes)
tester := newTester(t, hashes, blocks)
tester.newPeer("peer1", big.NewInt(10000), hashes[0])
tester.newPeer("peer2", big.NewInt(0), common.Hash{})
tester.badBlocksPeer("peer3", big.NewInt(0), common.Hash{})
tester.badBlocksPeer("peer4", big.NewInt(0), common.Hash{})
// Concurrently download and take the blocks
took, err := tester.syncTake("peer1", hashes[0])
if err != nil {
// 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 len(took) != targetBlocks {
t.Fatalf("downloaded block mismatch: have %v, want %v", len(took), targetBlocks)
if queued := len(tester.downloader.queue.blockPool); 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; {
// Wait a bit for sync to complete
for start := time.Now(); time.Since(start) < 3*time.Second; {
time.Sleep(25 * time.Millisecond)
if len(tester.downloader.queue.blockPool) == blockCacheLimit {
break
}
}
// 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)
}
}
@ -559,3 +527,86 @@ func TestMadeupParentBlockChainAttack(t *testing.T) {
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
}
// Check that after banning an entire chain, bad peers get dropped
if err := tester.newPeer("new attacker", big.NewInt(10000), hashes[0]); err != errBannedHead {
t.Fatalf("peer registration mismatch: have %v, want %v", err, errBannedHead)
}
if peer := tester.downloader.peers.Peer("net attacker"); peer != nil {
t.Fatalf("banned attacker registered: %v", peer)
}
}
// 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) {
// Reduce the test size a bit
MaxBlockFetch = 4
maxBannedHashes = 256
// Construct a banned chain with more chunks than the ban limit
hashes := createHashes(0, maxBannedHashes*MaxBlockFetch)
hashes[len(hashes)-1] = 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 {
// 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)
}
// 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)
}
}
}
}

2
eth/downloader/peer.go
View File

@ -94,7 +94,7 @@ func (p *peer) SetIdle() {
for {
// Calculate the new download bandwidth allowance
prev := atomic.LoadInt32(&p.capacity)
next := int32(math.Max(1, math.Min(MaxBlockFetch, float64(prev)*scale)))
next := int32(math.Max(1, math.Min(float64(MaxBlockFetch), float64(prev)*scale)))
// Try to update the old value
if atomic.CompareAndSwapInt32(&p.capacity, prev, next) {

22
eth/downloader/queue.go
View File

@ -16,7 +16,7 @@ import (
"gopkg.in/karalabe/cookiejar.v2/collections/prque"
)
const (
var (
blockCacheLimit = 8 * MaxBlockFetch // Maximum number of blocks to cache before throttling the download
)
@ -54,6 +54,7 @@ func newQueue() *queue {
hashQueue: prque.New(),
pendPool: make(map[string]*fetchRequest),
blockPool: make(map[common.Hash]int),
blockCache: make([]*Block, blockCacheLimit),
}
}
@ -70,7 +71,7 @@ func (q *queue) Reset() {
q.blockPool = make(map[common.Hash]int)
q.blockOffset = 0
q.blockCache = nil
q.blockCache = make([]*Block, blockCacheLimit)
}
// Size retrieves the number of hashes in the queue, returning separately for
@ -208,7 +209,7 @@ func (q *queue) TakeBlocks() []*Block {
// Reserve reserves a set of hashes for the given peer, skipping any previously
// failed download.
func (q *queue) Reserve(p *peer) *fetchRequest {
func (q *queue) Reserve(p *peer, count int) *fetchRequest {
q.lock.Lock()
defer q.lock.Unlock()
@ -229,8 +230,7 @@ func (q *queue) Reserve(p *peer) *fetchRequest {
send := make(map[common.Hash]int)
skip := make(map[common.Hash]int)
capacity := p.Capacity()
for proc := 0; proc < space && len(send) < capacity && !q.hashQueue.Empty(); proc++ {
for proc := 0; proc < space && len(send) < count && !q.hashQueue.Empty(); proc++ {
hash, priority := q.hashQueue.Pop()
if p.ignored.Has(hash) {
skip[hash.(common.Hash)] = int(priority)
@ -345,20 +345,12 @@ func (q *queue) Deliver(id string, blocks []*types.Block) (err error) {
return nil
}
// Alloc ensures that the block cache is the correct size, given a starting
// offset, and a memory cap.
func (q *queue) Alloc(offset int) {
// Prepare configures the block cache offset to allow accepting inbound blocks.
func (q *queue) Prepare(offset int) {
q.lock.Lock()
defer q.lock.Unlock()
if q.blockOffset < offset {
q.blockOffset = offset
}
size := len(q.hashPool)
if size > blockCacheLimit {
size = blockCacheLimit
}
if len(q.blockCache) < size {
q.blockCache = append(q.blockCache, make([]*Block, size-len(q.blockCache))...)
}
}

4
eth/handler.go
View File

@ -213,8 +213,8 @@ func (self *ProtocolManager) handleMsg(p *peer) error {
return errResp(ErrDecode, "->msg %v: %v", msg, err)
}
if request.Amount > downloader.MaxHashFetch {
request.Amount = downloader.MaxHashFetch
if request.Amount > uint64(downloader.MaxHashFetch) {
request.Amount = uint64(downloader.MaxHashFetch)
}
hashes := self.chainman.GetBlockHashesFromHash(request.Hash, request.Amount)

2
eth/peer.go
View File

@ -102,7 +102,7 @@ func (p *peer) sendTransaction(tx *types.Transaction) error {
func (p *peer) requestHashes(from common.Hash) error {
glog.V(logger.Debug).Infof("[%s] fetching hashes (%d) %x...\n", p.id, downloader.MaxHashFetch, from[:4])
return p2p.Send(p.rw, GetBlockHashesMsg, getBlockHashesMsgData{from, downloader.MaxHashFetch})
return p2p.Send(p.rw, GetBlockHashesMsg, getBlockHashesMsgData{from, uint64(downloader.MaxHashFetch)})
}
func (p *peer) requestBlocks(hashes []common.Hash) error {