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eth/fetcher: handle and (crude) test block memory DOS

This commit is contained in:
Péter Szilágyi 2015-06-22 16:49:47 +03:00
parent d36c25bcbc
commit 1989d1491a
2 changed files with 105 additions and 23 deletions
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59
eth/fetcher/fetcher.go
View File

@ -20,7 +20,8 @@ const (
fetchTimeout = 5 * time.Second // Maximum alloted time to return an explicitly requested block
maxUncleDist = 7 // Maximum allowed backward distance from the chain head
maxQueueDist = 32 // Maximum allowed distance from the chain head to queue
announceLimit = 256 // Maximum number of unique blocks a peer may have announced
hashLimit = 256 // Maximum number of unique blocks a peer may have announced
blockLimit = 64 // Maximum number of unique blocks a per may have delivered
)
var (
@ -81,7 +82,8 @@ type Fetcher struct {
// Block cache
queue *prque.Prque // Queue containing the import operations (block number sorted)
queued map[common.Hash]struct{} // Presence set of already queued blocks (to dedup imports)
queues map[string]int // Per peer block counts to prevent memory exhaustion
queued map[common.Hash]*inject // Set of already queued blocks (to dedup imports)
// Callbacks
getBlock blockRetrievalFn // Retrieves a block from the local chain
@ -104,7 +106,8 @@ func New(getBlock blockRetrievalFn, validateBlock blockValidatorFn, broadcastBlo
announced: make(map[common.Hash][]*announce),
fetching: make(map[common.Hash]*announce),
queue: prque.New(),
queued: make(map[common.Hash]struct{}),
queues: make(map[string]int),
queued: make(map[common.Hash]*inject),
getBlock: getBlock,
validateBlock: validateBlock,
broadcastBlock: broadcastBlock,
@ -192,22 +195,24 @@ func (f *Fetcher) loop() {
// Clean up any expired block fetches
for hash, announce := range f.fetching {
if time.Since(announce.time) > fetchTimeout {
f.forgetBlock(hash)
f.forgetHash(hash)
}
}
// Import any queued blocks that could potentially fit
height := f.chainHeight()
for !f.queue.Empty() {
op := f.queue.PopItem().(*inject)
number := op.block.NumberU64()
// If too high up the chain or phase, continue later
number := op.block.NumberU64()
if number > height+1 {
f.queue.Push(op, -float32(op.block.NumberU64()))
break
}
// Otherwise if fresh and still unknown, try and import
if number+maxUncleDist < height || f.getBlock(op.block.Hash()) != nil {
hash := op.block.Hash()
if number+maxUncleDist < height || f.getBlock(hash) != nil {
f.forgetBlock(hash)
continue
}
f.insert(op.origin, op.block)
@ -221,8 +226,8 @@ func (f *Fetcher) loop() {
case notification := <-f.notify:
// A block was announced, make sure the peer isn't DOSing us
count := f.announces[notification.origin] + 1
if count > announceLimit {
glog.V(logger.Debug).Infof("Peer %s: exceeded outstanding announces (%d)", notification.origin, announceLimit)
if count > hashLimit {
glog.V(logger.Debug).Infof("Peer %s: exceeded outstanding announces (%d)", notification.origin, hashLimit)
break
}
// All is well, schedule the announce if block's not yet downloading
@ -241,8 +246,8 @@ func (f *Fetcher) loop() {
case hash := <-f.done:
// A pending import finished, remove all traces of the notification
f.forgetHash(hash)
f.forgetBlock(hash)
delete(f.queued, hash)
case <-fetch.C:
// At least one block's timer ran out, check for needing retrieval
@ -252,7 +257,7 @@ func (f *Fetcher) loop() {
if time.Since(announces[0].time) > arriveTimeout-gatherSlack {
// Pick a random peer to retrieve from, reset all others
announce := announces[rand.Intn(len(announces))]
f.forgetBlock(hash)
f.forgetHash(hash)
// If the block still didn't arrive, queue for fetching
if f.getBlock(hash) == nil {
@ -296,7 +301,7 @@ func (f *Fetcher) loop() {
if f.getBlock(hash) == nil {
explicit = append(explicit, block)
} else {
f.forgetBlock(hash)
f.forgetHash(hash)
}
} else {
download = append(download, block)
@ -339,6 +344,12 @@ func (f *Fetcher) reschedule(fetch *time.Timer) {
func (f *Fetcher) enqueue(peer string, block *types.Block) {
hash := block.Hash()
// Ensure the peer isn't DOSing us
count := f.queues[peer] + 1
if count > blockLimit {
glog.V(logger.Debug).Infof("Peer %s: discarded block #%d [%x], exceeded allowance (%d)", peer, block.NumberU64(), hash.Bytes()[:4], blockLimit)
return
}
// Discard any past or too distant blocks
if dist := int64(block.NumberU64()) - int64(f.chainHeight()); dist < -maxUncleDist || dist > maxQueueDist {
glog.V(logger.Debug).Infof("Peer %s: discarded block #%d [%x], distance %d", peer, block.NumberU64(), hash.Bytes()[:4], dist)
@ -346,8 +357,13 @@ func (f *Fetcher) enqueue(peer string, block *types.Block) {
}
// Schedule the block for future importing
if _, ok := f.queued[hash]; !ok {
f.queued[hash] = struct{}{}
f.queue.Push(&inject{origin: peer, block: block}, -float32(block.NumberU64()))
op := &inject{
origin: peer,
block: block,
}
f.queues[peer] = count
f.queued[hash] = op
f.queue.Push(op, -float32(block.NumberU64()))
if glog.V(logger.Debug) {
glog.Infof("Peer %s: queued block #%d [%x], total %v", peer, block.NumberU64(), hash.Bytes()[:4], f.queue.Size())
@ -389,8 +405,9 @@ func (f *Fetcher) insert(peer string, block *types.Block) {
}()
}
// forgetBlock removes all traces of a block from the fetcher's internal state.
func (f *Fetcher) forgetBlock(hash common.Hash) {
// forgetHash removes all traces of a block announcement from the fetcher's
// internal state.
func (f *Fetcher) forgetHash(hash common.Hash) {
// Remove all pending announces and decrement DOS counters
for _, announce := range f.announced[hash] {
f.announces[announce.origin]--
@ -409,3 +426,15 @@ func (f *Fetcher) forgetBlock(hash common.Hash) {
delete(f.fetching, hash)
}
}
// forgetBlock removes all traces of a queued block frmo the fetcher's internal
// state.
func (f *Fetcher) forgetBlock(hash common.Hash) {
if insert := f.queued[hash]; insert != nil {
f.queues[insert.origin]--
if f.queues[insert.origin] == 0 {
delete(f.queues, insert.origin)
}
delete(f.queued, hash)
}
}

67
eth/fetcher/fetcher_test.go
View File

@ -399,15 +399,15 @@ func TestDistantDiscarding(t *testing.T) {
// Tests that a peer is unable to use unbounded memory with sending infinite
// block announcements to a node, but that even in the face of such an attack,
// the fetcher remains operational.
func TestAnnounceMemoryExhaustionAttack(t *testing.T) {
func TestHashMemoryExhaustionAttack(t *testing.T) {
tester := newTester()
// Create a valid chain and an infinite junk chain
hashes := createHashes(announceLimit+2*maxQueueDist, knownHash)
hashes := createHashes(hashLimit+2*maxQueueDist, knownHash)
blocks := createBlocksFromHashes(hashes)
valid := tester.makeFetcher(blocks)
attack := createHashes(announceLimit+2*maxQueueDist, unknownHash)
attack := createHashes(hashLimit+2*maxQueueDist, unknownHash)
attacker := tester.makeFetcher(nil)
// Feed the tester a huge hashset from the attacker, and a limited from the valid peer
@ -417,8 +417,8 @@ func TestAnnounceMemoryExhaustionAttack(t *testing.T) {
}
tester.fetcher.Notify("attacker", attack[i], time.Now().Add(arriveTimeout/2), attacker)
}
if len(tester.fetcher.announced) != announceLimit+maxQueueDist {
t.Fatalf("queued announce count mismatch: have %d, want %d", len(tester.fetcher.announced), announceLimit+maxQueueDist)
if len(tester.fetcher.announced) != hashLimit+maxQueueDist {
t.Fatalf("queued announce count mismatch: have %d, want %d", len(tester.fetcher.announced), hashLimit+maxQueueDist)
}
// Wait for synchronisation to complete and check success for the valid peer
time.Sleep(2 * arriveTimeout)
@ -431,10 +431,63 @@ func TestAnnounceMemoryExhaustionAttack(t *testing.T) {
tester.fetcher.Notify("valid", hashes[i], time.Now().Add(time.Millisecond), valid)
i--
}
time.Sleep(256 * time.Millisecond)
time.Sleep(500 * time.Millisecond)
}
time.Sleep(256 * time.Millisecond)
time.Sleep(500 * time.Millisecond)
if imported := len(tester.blocks); imported != len(hashes) {
t.Fatalf("fully synchronised block mismatch: have %v, want %v", imported, len(hashes))
}
}
// Tests that blocks sent to the fetcher (either through propagation or via hash
// announces and retrievals) don't pile up indefinitely, exhausting available
// system memory.
func TestBlockMemoryExhaustionAttack(t *testing.T) {
tester := newTester()
// Create a valid chain and a batch of dangling (but in range) blocks
hashes := createHashes(blockLimit, knownHash)
blocks := createBlocksFromHashes(hashes)
attack := make(map[common.Hash]*types.Block)
for i := 0; i < 16; i++ {
hashes := createHashes(maxQueueDist-1, unknownHash)
blocks := createBlocksFromHashes(hashes)
for _, hash := range hashes[:maxQueueDist-2] {
attack[hash] = blocks[hash]
}
}
// Try to feed all the attacker blocks make sure only a limited batch is accepted
for _, block := range attack {
tester.fetcher.Enqueue("attacker", block)
}
time.Sleep(100 * time.Millisecond)
if queued := tester.fetcher.queue.Size(); queued != blockLimit {
t.Fatalf("queued block count mismatch: have %d, want %d", queued, blockLimit)
}
// Queue up a batch of valid blocks, and check that a new peer is allowed to do so
for i := 0; i < maxQueueDist-1; i++ {
tester.fetcher.Enqueue("valid", blocks[hashes[len(hashes)-3-i]])
}
time.Sleep(100 * time.Millisecond)
if queued := tester.fetcher.queue.Size(); queued != blockLimit+maxQueueDist-1 {
t.Fatalf("queued block count mismatch: have %d, want %d", queued, blockLimit+maxQueueDist-1)
}
// Insert the missing piece (and sanity check the import)
tester.fetcher.Enqueue("valid", blocks[hashes[len(hashes)-2]])
time.Sleep(500 * time.Millisecond)
if imported := len(tester.blocks); imported != maxQueueDist+1 {
t.Fatalf("synchronised block mismatch: have %v, want %v", imported, maxQueueDist+1)
}
// Insert the remaining blocks in chunks to ensure clean DOS protection
for i := maxQueueDist; i < len(hashes)-1; i++ {
tester.fetcher.Enqueue("valid", blocks[hashes[len(hashes)-2-i]])
if i%maxQueueDist == 0 {
time.Sleep(500 * time.Millisecond)
}
}
time.Sleep(500 * time.Millisecond)
if imported := len(tester.blocks); imported != len(hashes) {
t.Fatalf("synchronised block mismatch: have %v, want %v", imported, len(hashes))
}
}