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authorPéter Szilágyi <peterke@gmail.com>2015-05-15 06:40:16 +0800
committerPéter Szilágyi <peterke@gmail.com>2015-05-15 20:01:58 +0800
commitcd2fb0905109828028172c84f9c10f1343647ca6 (patch)
treeede1984738a0d16f338341f7a1bc94e17381a715
parentc1f0d40e34a80f4453a9a54f90e2d4551c3bdb05 (diff)
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eth, eth/downloader: prevent hash repeater attack
-rw-r--r--eth/downloader/downloader.go10
-rw-r--r--eth/downloader/downloader_test.go29
-rw-r--r--eth/downloader/queue.go20
-rw-r--r--eth/sync.go6
4 files changed, 50 insertions, 15 deletions
diff --git a/eth/downloader/downloader.go b/eth/downloader/downloader.go
index 616971f73..3da606aef 100644
--- a/eth/downloader/downloader.go
+++ b/eth/downloader/downloader.go
@@ -27,7 +27,7 @@ var (
errLowTd = errors.New("peer's TD is too low")
ErrBusy = errors.New("busy")
errUnknownPeer = errors.New("peer's unknown or unhealthy")
- errBadPeer = errors.New("action from bad peer ignored")
+ ErrBadPeer = errors.New("action from bad peer ignored")
errNoPeers = errors.New("no peers to keep download active")
ErrPendingQueue = errors.New("pending items in queue")
ErrTimeout = errors.New("timeout")
@@ -266,9 +266,11 @@ out:
break
}
}
- d.queue.Insert(hashPack.hashes)
-
- if !done {
+ // Insert all the new hashes, but only continue if got something useful
+ inserts := d.queue.Insert(hashPack.hashes)
+ if inserts == 0 && !done {
+ return ErrBadPeer
+ } else if !done {
activePeer.getHashes(hash)
continue
}
diff --git a/eth/downloader/downloader_test.go b/eth/downloader/downloader_test.go
index 50fe00d42..1bba3ca51 100644
--- a/eth/downloader/downloader_test.go
+++ b/eth/downloader/downloader_test.go
@@ -336,3 +336,32 @@ func TestNonExistingParentAttack(t *testing.T) {
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(1000, 1)
+ blocks := createBlocksFromHashes(hashes)
+
+ hashes = hashes[:len(hashes)-1]
+
+ // Try and sync with the malicious node
+ tester := newTester(t, hashes, blocks)
+ tester.newPeer("attack", big.NewInt(10000), hashes[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(100 * time.Millisecond):
+ t.Fatalf("synchronisation blocked")
+ case err := <-errc:
+ if err == nil {
+ t.Fatalf("synchronisation succeeded")
+ }
+ }
+}
diff --git a/eth/downloader/queue.go b/eth/downloader/queue.go
index 6ad915757..fdea1f63f 100644
--- a/eth/downloader/queue.go
+++ b/eth/downloader/queue.go
@@ -122,24 +122,26 @@ func (q *queue) Has(hash common.Hash) bool {
return false
}
-// Insert adds a set of hashes for the download queue for scheduling.
-func (q *queue) Insert(hashes []common.Hash) {
+// Insert adds a set of hashes for the download queue for scheduling, returning
+// the number of new hashes encountered.
+func (q *queue) Insert(hashes []common.Hash) int {
q.lock.Lock()
defer q.lock.Unlock()
// Insert all the hashes prioritized in the arrival order
- for i, hash := range hashes {
- index := q.hashCounter + i
-
+ inserts := 0
+ for _, hash := range hashes {
+ // Skip anything we already have
if old, ok := q.hashPool[hash]; ok {
glog.V(logger.Warn).Infof("Hash %x already scheduled at index %v", hash, old)
continue
}
- q.hashPool[hash] = index
- q.hashQueue.Push(hash, float32(index)) // Highest gets schedules first
+ // Update the counters and insert the hash
+ q.hashCounter, inserts = q.hashCounter+1, inserts+1
+ q.hashPool[hash] = q.hashCounter
+ q.hashQueue.Push(hash, float32(q.hashCounter)) // Highest gets schedules first
}
- // Update the hash counter for the next batch of inserts
- q.hashCounter += len(hashes)
+ return inserts
}
// GetHeadBlock retrieves the first block from the cache, or nil if it hasn't
diff --git a/eth/sync.go b/eth/sync.go
index c89f34596..73f6253be 100644
--- a/eth/sync.go
+++ b/eth/sync.go
@@ -101,11 +101,13 @@ func (pm *ProtocolManager) synchronise(peer *peer) {
case downloader.ErrBusy:
glog.V(logger.Debug).Infof("Synchronisation already in progress")
- case downloader.ErrTimeout:
- glog.V(logger.Debug).Infof("Removing peer %v due to sync timeout", peer.id)
+ case downloader.ErrTimeout, downloader.ErrBadPeer:
+ glog.V(logger.Debug).Infof("Removing peer %v: %v", peer.id, err)
pm.removePeer(peer)
+
case downloader.ErrPendingQueue:
glog.V(logger.Debug).Infoln("Synchronisation aborted:", err)
+
default:
glog.V(logger.Warn).Infof("Synchronisation failed: %v", err)
}