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eth, eth/downloader: handle a potential unknown parent attack

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This commit is contained in:
Péter Szilágyi 2015-05-14 15:24:18 +03:00
parent 7cb0e24245
commit a4246c2da6
3 changed files with 112 additions and 31 deletions
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20
eth/downloader/downloader.go
View File

@ -37,6 +37,7 @@ var (
errCancelHashFetch = errors.New("hash fetching cancelled (requested)")
errCancelBlockFetch = errors.New("block downloading cancelled (requested)")
errNoSyncActive = errors.New("no sync active")
ErrUnknownParent = errors.New("block has unknown parent")
)
type hashCheckFn func(common.Hash) bool
@ -142,16 +143,19 @@ func (d *Downloader) Synchronise(id string, hash common.Hash) error {
return d.syncWithPeer(p, hash)
}
// TakeBlocks takes blocks from the queue and yields them to the blockTaker handler
// it's possible it yields no blocks
func (d *Downloader) TakeBlocks() types.Blocks {
// Check that there are blocks available and its parents are known
// TakeBlocks takes blocks from the queue and yields them to the caller.
func (d *Downloader) TakeBlocks() (types.Blocks, error) {
// If the head block is missing, no blocks are ready
head := d.queue.GetHeadBlock()
if head == nil || !d.hasBlock(head.ParentHash()) {
return nil
if head == nil {
return nil, nil
}
// Retrieve a full batch of blocks
return d.queue.TakeBlocks(head)
// If the parent hash of the head is unknown, notify the caller
if !d.hasBlock(head.ParentHash()) {
return nil, ErrUnknownParent
}
// Otherwise retrieve a full batch of blocks
return d.queue.TakeBlocks(head), nil
}
func (d *Downloader) Has(hash common.Hash) bool {

100
eth/downloader/downloader_test.go
View File

@ -10,7 +10,10 @@ import (
"github.com/ethereum/go-ethereum/core/types"
)
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}
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}
)
func createHashes(start, amount int) (hashes []common.Hash) {
hashes = make([]common.Hash, amount+1)
@ -27,7 +30,7 @@ func createBlock(i int, prevHash, hash common.Hash) *types.Block {
header := &types.Header{Number: big.NewInt(int64(i))}
block := types.NewBlockWithHeader(header)
block.HeaderHash = hash
block.ParentHeaderHash = knownHash
block.ParentHeaderHash = prevHash
return block
}
@ -42,9 +45,12 @@ func createBlocksFromHashes(hashes []common.Hash) map[common.Hash]*types.Block {
}
type downloadTester struct {
downloader *Downloader
hashes []common.Hash
blocks map[common.Hash]*types.Block
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
t *testing.T
pcount int
done chan bool
@ -52,7 +58,15 @@ type downloadTester struct {
}
func newTester(t *testing.T, hashes []common.Hash, blocks map[common.Hash]*types.Block) *downloadTester {
tester := &downloadTester{t: t, hashes: hashes, blocks: blocks, done: make(chan bool)}
tester := &downloadTester{
t: t,
hashes: hashes,
blocks: blocks,
chain: []common.Hash{knownHash},
done: make(chan bool),
}
downloader := New(tester.hasBlock, tester.getBlock)
tester.downloader = downloader
@ -64,9 +78,17 @@ func (dl *downloadTester) sync(peerId string, hash common.Hash) error {
return dl.downloader.Synchronise(peerId, hash)
}
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 {
if knownHash == hash {
return true
for _, h := range dl.chain {
if h == hash {
return true
}
}
return false
}
@ -175,10 +197,12 @@ func TestTaking(t *testing.T) {
if err != nil {
t.Error("download error", err)
}
bs1 := tester.downloader.TakeBlocks()
if len(bs1) != 1000 {
t.Error("expected to take 1000, got", len(bs1))
bs, err := tester.downloader.TakeBlocks()
if err != nil {
t.Fatalf("failed to take blocks: %v", err)
}
if len(bs) != targetBlocks {
t.Error("retrieved block mismatch: have %v, want %v", len(bs), targetBlocks)
}
}
@ -248,17 +272,18 @@ func TestThrottling(t *testing.T) {
done := make(chan struct{})
took := []*types.Block{}
go func() {
for {
for running := true; running; {
select {
case <-done:
took = append(took, tester.downloader.TakeBlocks()...)
done <- struct{}{}
return
running = false
default:
took = append(took, tester.downloader.TakeBlocks()...)
time.Sleep(time.Millisecond)
}
// Take a batch of blocks and accumulate
blocks, _ := tester.downloader.TakeBlocks()
took = append(took, blocks...)
}
done <- struct{}{}
}()
// Synchronise the two threads and verify
@ -273,3 +298,44 @@ func TestThrottling(t *testing.T) {
t.Fatalf("downloaded block mismatch: have %v, want %v", len(took), targetBlocks)
}
}
// 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, err := tester.downloader.TakeBlocks()
if err != ErrUnknownParent {
t.Fatalf("take error mismatch: have %v, want %v", err, ErrUnknownParent)
}
if len(bs) != 0 {
t.Error("retrieved block mismatch: have %v, want %v", len(bs), 0)
}
// Cancel the download due to the parent attack
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, err = tester.downloader.TakeBlocks()
if err != nil {
t.Fatalf("failed to retrieve blocks: %v", err)
}
if len(bs) != 1 {
t.Error("retrieved block mismatch: have %v, want %v", len(bs), 1)
}
}

23
eth/sync.go
View File

@ -2,6 +2,7 @@ package eth
import (
"math"
"sync/atomic"
"time"
"github.com/ethereum/go-ethereum/eth/downloader"
@ -14,6 +15,7 @@ import (
func (pm *ProtocolManager) update() {
forceSync := time.Tick(forceSyncCycle)
blockProc := time.Tick(blockProcCycle)
blockProcPend := int32(0)
for {
select {
@ -36,7 +38,14 @@ func (pm *ProtocolManager) update() {
}
case <-blockProc:
// Try to pull some blocks from the downloaded
go pm.processBlocks()
if atomic.CompareAndSwapInt32(&blockProcPend, 0, 1) {
go func() {
if err := pm.processBlocks(); err != nil {
pm.downloader.Cancel()
}
atomic.StoreInt32(&blockProcPend, 0)
}()
}
case <-pm.quitSync:
return
@ -52,8 +61,12 @@ func (pm *ProtocolManager) processBlocks() error {
pm.wg.Add(1)
defer pm.wg.Done()
// Take a batch of blocks (will return nil if a previous batch has not reached the chain yet)
blocks := pm.downloader.TakeBlocks()
// Take a batch of blocks, but abort if there's an invalid head or if the chain's empty
blocks, err := pm.downloader.TakeBlocks()
if err != nil {
glog.V(logger.Warn).Infof("Block processing failed: %v", err)
return err
}
if len(blocks) == 0 {
return nil
}
@ -63,9 +76,7 @@ func (pm *ProtocolManager) processBlocks() error {
max := int(math.Min(float64(len(blocks)), float64(blockProcAmount)))
_, err := pm.chainman.InsertChain(blocks[:max])
if err != nil {
// cancel download process
pm.downloader.Cancel()
glog.V(logger.Warn).Infof("Block insertion failed: %v", err)
return err
}
blocks = blocks[max:]