cerc-io/plugeth
18
0
Fork 1
Code Issues 4 Pull Requests Packages Projects Releases Wiki Activity

Merge pull request #974 from karalabe/downloader-fix-unknown-parent-attack

Browse Source 
eth, eth/downloader: handle a potential unknown parent attack
This commit is contained in:
Jeffrey Wilcke 2015-05-14 08:16:30 -07:00
commit 060a07cf69
4 changed files with 92 additions and 38 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

11
eth/downloader/downloader.go
View File

@ -150,16 +150,9 @@ 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
// TakeBlocks takes blocks from the queue and yields them to the caller.
func (d *Downloader) TakeBlocks() types.Blocks {
// Check that there are blocks available and its parents are known
head := d.queue.GetHeadBlock()
if head == nil || !d.hasBlock(head.ParentHash()) {
return nil
}
// Retrieve a full batch of blocks
return d.queue.TakeBlocks(head)
return d.queue.TakeBlocks()
}
func (d *Downloader) Has(hash common.Hash) bool {

95
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 +197,9 @@ 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 := tester.downloader.TakeBlocks()
if len(bs) != targetBlocks {
t.Error("retrieved block mismatch: have %v, want %v", len(bs), targetBlocks)
}
}
@ -248,17 +269,17 @@ 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
took = append(took, tester.downloader.TakeBlocks()...)
}
done <- struct{}{}
}()
// Synchronise the two threads and verify
@ -273,3 +294,43 @@ 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 := tester.downloader.TakeBlocks()
if len(bs) != 1 {
t.Fatalf("retrieved block mismatch: have %v, want %v", len(bs), 1)
}
if tester.hasBlock(bs[0].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].ParentHash()) {
t.Fatalf("tester doesn't know about the origin hash")
}
}

10
eth/downloader/queue.go
View File

@ -172,17 +172,11 @@ func (q *queue) GetBlock(hash common.Hash) *types.Block {
}
// TakeBlocks retrieves and permanently removes a batch of blocks from the cache.
// The head parameter is required to prevent a race condition where concurrent
// takes may fail parent verifications.
func (q *queue) TakeBlocks(head *types.Block) types.Blocks {
func (q *queue) TakeBlocks() types.Blocks {
q.lock.Lock()
defer q.lock.Unlock()
// Short circuit if the head block's different
if len(q.blockCache) == 0 || q.blockCache[0] != head {
return nil
}
// Otherwise accumulate all available blocks
// Accumulate all available blocks
var blocks types.Blocks
for _, block := range q.blockCache {
if block == nil {

14
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 +38,12 @@ 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() {
pm.processBlocks()
atomic.StoreInt32(&blockProcPend, 0)
}()
}
case <-pm.quitSync:
return
@ -52,7 +59,7 @@ 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)
// Short circuit if no blocks are available for insertion
blocks := pm.downloader.TakeBlocks()
if len(blocks) == 0 {
return nil
@ -63,9 +70,8 @@ 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
glog.V(logger.Warn).Infof("Block insertion failed: %v", err)
pm.downloader.Cancel()
return err
}
blocks = blocks[max:]