Merge pull request #988 from karalabe/fix-downloader-vulnerabilities

Fix downloader vulnerabilities

1 files changed, 205 insertions, 45 deletions

diff --git a/eth/downloader/downloader_test.go b/eth/downloader/downloader_test.go
index 50fe00d42..d55664314 100644
--- a/eth/downloader/downloader_test.go
+++ b/eth/downloader/downloader_test.go
@@ -23,25 +23,26 @@ func createHashes(start, amount int) (hashes []common.Hash) {
 	for i := range hashes[:len(hashes)-1] {
 		binary.BigEndian.PutUint64(hashes[i][:8], uint64(i+2))
 	}
-
 	return
 }
 
-func createBlock(i int, prevHash, hash common.Hash) *types.Block {
+func createBlock(i int, parent, hash common.Hash) *types.Block {
 	header := &types.Header{Number: big.NewInt(int64(i))}
 	block := types.NewBlockWithHeader(header)
 	block.HeaderHash = hash
-	block.ParentHeaderHash = prevHash
+	block.ParentHeaderHash = parent
 	return block
 }
 
 func createBlocksFromHashes(hashes []common.Hash) map[common.Hash]*types.Block {
 	blocks := make(map[common.Hash]*types.Block)
-
-	for i, hash := range hashes {
-		blocks[hash] = createBlock(len(hashes)-i, knownHash, hash)
+	for i := 0; i < len(hashes); i++ {
+		parent := knownHash
+		if i < len(hashes)-1 {
+			parent = hashes[i+1]
+		}
+		blocks[hashes[i]] = createBlock(len(hashes)-i, parent, hashes[i])
 	}
-
 	return blocks
 }
 
@@ -75,9 +76,40 @@ func newTester(t *testing.T, hashes []common.Hash, blocks map[common.Hash]*types
 	return tester
 }
 
-func (dl *downloadTester) sync(peerId string, hash common.Hash) error {
+// sync is a simple wrapper around the downloader to start synchronisation and
+// block until it returns
+func (dl *downloadTester) sync(peerId string, head common.Hash) error {
 	dl.activePeerId = peerId
-	return dl.downloader.Synchronise(peerId, hash)
+	return dl.downloader.Synchronise(peerId, head)
+}
+
+// syncTake is starts synchronising with a remote peer, but concurrently it also
+// starts fetching blocks that the downloader retrieved. IT blocks until both go
+// routines terminate.
+func (dl *downloadTester) syncTake(peerId string, head common.Hash) (types.Blocks, error) {
+	// Start a block collector to take blocks as they become available
+	done := make(chan struct{})
+	took := []*types.Block{}
+	go func() {
+		for running := true; running; {
+			select {
+			case <-done:
+				running = false
+			default:
+				time.Sleep(time.Millisecond)
+			}
+			// Take a batch of blocks and accumulate
+			took = append(took, dl.downloader.TakeBlocks()...)
+		}
+		done <- struct{}{}
+	}()
+	// Start the downloading, sync the taker and return
+	err := dl.sync(peerId, head)
+
+	done <- struct{}{}
+	<-done
+
+	return took, err
 }
 
 func (dl *downloadTester) insertBlocks(blocks types.Blocks) {
@@ -99,18 +131,37 @@ func (dl *downloadTester) getBlock(hash common.Hash) *types.Block {
 	return dl.blocks[knownHash]
 }
 
-func (dl *downloadTester) getHashes(hash common.Hash) error {
-	dl.downloader.DeliverHashes(dl.activePeerId, dl.hashes)
+// getHashes retrieves a batch of hashes for reconstructing the chain.
+func (dl *downloadTester) getHashes(head common.Hash) error {
+	// Gather the next batch of hashes
+	hashes := make([]common.Hash, 0, maxHashFetch)
+	for i, hash := range dl.hashes {
+		if hash == head {
+			i++
+			for len(hashes) < cap(hashes) && i < len(dl.hashes) {
+				hashes = append(hashes, dl.hashes[i])
+				i++
+			}
+			break
+		}
+	}
+	// Delay delivery a bit to allow attacks to unfold
+	id := dl.activePeerId
+	go func() {
+		time.Sleep(time.Millisecond)
+		dl.downloader.DeliverHashes(id, hashes)
+	}()
 	return nil
 }
 
 func (dl *downloadTester) getBlocks(id string) func([]common.Hash) error {
 	return func(hashes []common.Hash) error {
-		blocks := make([]*types.Block, len(hashes))
-		for i, hash := range hashes {
-			blocks[i] = dl.blocks[hash]
+		blocks := make([]*types.Block, 0, len(hashes))
+		for _, hash := range hashes {
+			if block, ok := dl.blocks[hash]; ok {
+				blocks = append(blocks, block)
+			}
 		}
-
 		go dl.downloader.DeliverBlocks(id, blocks)
 
 		return nil
@@ -134,7 +185,7 @@ func (dl *downloadTester) badBlocksPeer(id string, td *big.Int, hash common.Hash
 
 func TestDownload(t *testing.T) {
 	minDesiredPeerCount = 4
-	blockTtl = 1 * time.Second
+	blockTTL = 1 * time.Second
 
 	targetBlocks := 1000
 	hashes := createHashes(0, targetBlocks)
@@ -183,7 +234,7 @@ func TestMissing(t *testing.T) {
 
 func TestTaking(t *testing.T) {
 	minDesiredPeerCount = 4
-	blockTtl = 1 * time.Second
+	blockTTL = 1 * time.Second
 
 	targetBlocks := 1000
 	hashes := createHashes(0, targetBlocks)
@@ -224,7 +275,7 @@ func TestInactiveDownloader(t *testing.T) {
 
 func TestCancel(t *testing.T) {
 	minDesiredPeerCount = 4
-	blockTtl = 1 * time.Second
+	blockTTL = 1 * time.Second
 
 	targetBlocks := 1000
 	hashes := createHashes(0, targetBlocks)
@@ -250,7 +301,7 @@ func TestCancel(t *testing.T) {
 
 func TestThrottling(t *testing.T) {
 	minDesiredPeerCount = 4
-	blockTtl = 1 * time.Second
+	blockTTL = 1 * time.Second
 
 	targetBlocks := 16 * blockCacheLimit
 	hashes := createHashes(0, targetBlocks)
@@ -263,32 +314,7 @@ func TestThrottling(t *testing.T) {
 	tester.badBlocksPeer("peer4", big.NewInt(0), common.Hash{})
 
 	// Concurrently download and take the blocks
-	errc := make(chan error, 1)
-	go func() {
-		errc <- tester.sync("peer1", hashes[0])
-	}()
-
-	done := make(chan struct{})
-	took := []*types.Block{}
-	go func() {
-		for running := true; running; {
-			select {
-			case <-done:
-				running = false
-			default:
-				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
-	err := <-errc
-	done <- struct{}{}
-	<-done
-
+	took, err := tester.syncTake("peer1", hashes[0])
 	if err != nil {
 		t.Fatalf("failed to synchronise blocks: %v", err)
 	}
@@ -336,3 +362,137 @@ 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(0, blockCacheLimit)
+	blocks := createBlocksFromHashes(hashes)
+	forged := hashes[:len(hashes)-1]
+
+	// Try and sync with the malicious node
+	tester := newTester(t, forged, blocks)
+	tester.newPeer("attack", big.NewInt(10000), forged[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")
+		}
+	}
+	// Ensure that a valid chain can still pass sync
+	tester.hashes = hashes
+	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)
+	}
+}
+
+// Tests that if a malicious peers returns a non-existent block hash, it should
+// eventually time out and the sync reattempted.
+func TestNonExistingBlockAttack(t *testing.T) {
+	// Create a valid chain, but forge the last link
+	hashes := createHashes(0, blockCacheLimit)
+	blocks := createBlocksFromHashes(hashes)
+	origin := hashes[len(hashes)/2]
+
+	hashes[len(hashes)/2] = 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 != errPeersUnavailable {
+		t.Fatalf("synchronisation error mismatch: have %v, want %v", err, errPeersUnavailable)
+	}
+	// Ensure that a valid chain can still pass sync
+	hashes[len(hashes)/2] = origin
+	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)
+	}
+}
+
+// Tests that if a malicious peer is returning hashes in a weird order, that the
+// sync throttler doesn't choke on them waiting for the valid blocks.
+func TestInvalidHashOrderAttack(t *testing.T) {
+	// Create a valid long chain, but reverse some hashes within
+	hashes := createHashes(0, 4*blockCacheLimit)
+	blocks := createBlocksFromHashes(hashes)
+
+	chunk1 := make([]common.Hash, blockCacheLimit)
+	chunk2 := make([]common.Hash, blockCacheLimit)
+	copy(chunk1, hashes[blockCacheLimit:2*blockCacheLimit])
+	copy(chunk2, hashes[2*blockCacheLimit:3*blockCacheLimit])
+
+	reverse := make([]common.Hash, len(hashes))
+	copy(reverse, hashes)
+	copy(reverse[2*blockCacheLimit:], chunk1)
+	copy(reverse[blockCacheLimit:], chunk2)
+
+	// Try and sync with the malicious node and check that it fails
+	tester := newTester(t, reverse, blocks)
+	tester.newPeer("attack", big.NewInt(10000), reverse[0])
+	if _, err := tester.syncTake("attack", reverse[0]); err != ErrInvalidChain {
+		t.Fatalf("synchronisation error mismatch: have %v, want %v", err, ErrInvalidChain)
+	}
+	// Ensure that a valid chain can still pass sync
+	tester.hashes = hashes
+	tester.newPeer("valid", big.NewInt(20000), hashes[0])
+	if _, err := tester.syncTake("valid", hashes[0]); err != nil {
+		t.Fatalf("failed to synchronise blocks: %v", err)
+	}
+}
+
+// Tests that if a malicious peer makes up a random hash chain and tries to push
+// indefinitely, it actually gets caught with it.
+func TestMadeupHashChainAttack(t *testing.T) {
+	blockTTL = 100 * time.Millisecond
+	crossCheckCycle = 25 * time.Millisecond
+
+	// Create a long chain of hashes without backing blocks
+	hashes := createHashes(0, 1024*blockCacheLimit)
+
+	// Try and sync with the malicious node and check that it fails
+	tester := newTester(t, hashes, nil)
+	tester.newPeer("attack", big.NewInt(10000), hashes[0])
+	if _, err := tester.syncTake("attack", hashes[0]); err != ErrCrossCheckFailed {
+		t.Fatalf("synchronisation error mismatch: have %v, want %v", err, ErrCrossCheckFailed)
+	}
+}
+
+// Tests that if a malicious peer makes up a random block chain, and tried to
+// push indefinitely, it actually gets caught with it.
+func TestMadeupBlockChainAttack(t *testing.T) {
+	blockTTL = 100 * time.Millisecond
+	crossCheckCycle = 25 * time.Millisecond
+
+	// Create a long chain of blocks and simulate an invalid chain by dropping every second
+	hashes := createHashes(0, 32*blockCacheLimit)
+	blocks := createBlocksFromHashes(hashes)
+
+	gapped := make([]common.Hash, len(hashes)/2)
+	for i := 0; i < len(gapped); i++ {
+		gapped[i] = hashes[2*i]
+	}
+	// Try and sync with the malicious node and check that it fails
+	tester := newTester(t, gapped, blocks)
+	tester.newPeer("attack", big.NewInt(10000), gapped[0])
+	if _, err := tester.syncTake("attack", gapped[0]); err != ErrCrossCheckFailed {
+		t.Fatalf("synchronisation error mismatch: have %v, want %v", err, ErrCrossCheckFailed)
+	}
+	// Ensure that a valid chain can still pass sync
+	tester.hashes = hashes
+	tester.newPeer("valid", big.NewInt(20000), hashes[0])
+	if _, err := tester.syncTake("valid", hashes[0]); err != nil {
+		t.Fatalf("failed to synchronise blocks: %v", err)
+	}
+}