From a90cc66f3c9635ce93b8df3fd8dcd6418063f97e Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?P=C3=A9ter=20Szil=C3=A1gyi?= <peterke@gmail.com>
Date: Mon, 13 Jan 2020 14:23:54 +0200
Subject: [PATCH] eth: check propagated block malformation on receiption

---
 eth/handler.go      |  8 ++++++
 eth/handler_test.go | 62 +++++++++++++++++++++++++++++++++++++++++++++
 2 files changed, 70 insertions(+)

diff --git a/eth/handler.go b/eth/handler.go
index d2355a876..e18fa6124 100644
--- a/eth/handler.go
+++ b/eth/handler.go
@@ -687,6 +687,14 @@ func (pm *ProtocolManager) handleMsg(p *peer) error {
 		if err := msg.Decode(&request); err != nil {
 			return errResp(ErrDecode, "%v: %v", msg, err)
 		}
+		if hash := types.CalcUncleHash(request.Block.Uncles()); hash != request.Block.UncleHash() {
+			log.Warn("Propagated block has invalid uncles", "have", hash, "exp", request.Block.UncleHash())
+			break // TODO(karalabe): return error eventually, but wait a few releases
+		}
+		if hash := types.DeriveSha(request.Block.Transactions()); hash != request.Block.TxHash() {
+			log.Warn("Propagated block has invalid body", "have", hash, "exp", request.Block.TxHash())
+			break // TODO(karalabe): return error eventually, but wait a few releases
+		}
 		if err := request.sanityCheck(); err != nil {
 			return err
 		}
diff --git a/eth/handler_test.go b/eth/handler_test.go
index 05ddca3ef..893bfffa4 100644
--- a/eth/handler_test.go
+++ b/eth/handler_test.go
@@ -634,3 +634,65 @@ outer:
 		t.Errorf("block broadcast to %d peers, expected %d", receivedCount, broadcastExpected)
 	}
 }
+
+// Tests that a propagated malformed block (uncles or transactions don't match
+// with the hashes in the header) gets discarded and not broadcast forward.
+func TestBroadcastMalformedBlock(t *testing.T) {
+	// Create a live node to test propagation with
+	var (
+		engine  = ethash.NewFaker()
+		db      = rawdb.NewMemoryDatabase()
+		config  = &params.ChainConfig{}
+		gspec   = &core.Genesis{Config: config}
+		genesis = gspec.MustCommit(db)
+	)
+	blockchain, err := core.NewBlockChain(db, nil, config, engine, vm.Config{}, nil)
+	if err != nil {
+		t.Fatalf("failed to create new blockchain: %v", err)
+	}
+	pm, err := NewProtocolManager(config, nil, downloader.FullSync, DefaultConfig.NetworkId, new(event.TypeMux), new(testTxPool), engine, blockchain, db, 1, nil)
+	if err != nil {
+		t.Fatalf("failed to start test protocol manager: %v", err)
+	}
+	pm.Start(2)
+	defer pm.Stop()
+
+	// Create two peers, one to send the malformed block with and one to check
+	// propagation
+	source, _ := newTestPeer("source", eth63, pm, true)
+	defer source.close()
+
+	sink, _ := newTestPeer("sink", eth63, pm, true)
+	defer sink.close()
+
+	// Create various combinations of malformed blocks
+	chain, _ := core.GenerateChain(gspec.Config, genesis, ethash.NewFaker(), db, 1, func(i int, gen *core.BlockGen) {})
+
+	malformedUncles := chain[0].Header()
+	malformedUncles.UncleHash[0]++
+	malformedTransactions := chain[0].Header()
+	malformedTransactions.TxHash[0]++
+	malformedEverything := chain[0].Header()
+	malformedEverything.UncleHash[0]++
+	malformedEverything.TxHash[0]++
+
+	// Keep listening to broadcasts and notify if any arrives
+	notify := make(chan struct{})
+	go func() {
+		if _, err := sink.app.ReadMsg(); err == nil {
+			notify <- struct{}{}
+		}
+	}()
+	// Try to broadcast all malformations and ensure they all get discarded
+	for _, header := range []*types.Header{malformedUncles, malformedTransactions, malformedEverything} {
+		block := types.NewBlockWithHeader(header).WithBody(chain[0].Transactions(), chain[0].Uncles())
+		if err := p2p.Send(source.app, NewBlockMsg, []interface{}{block, big.NewInt(131136)}); err != nil {
+			t.Fatalf("failed to broadcast block: %v", err)
+		}
+		select {
+		case <-notify:
+			t.Fatalf("malformed block forwarded")
+		case <-time.After(100 * time.Millisecond):
+		}
+	}
+}