fix sbft primary crashing a correct replica

A replica getting a checkpoint that does not match its preprepare should
not kill itself, as primary could be Byzantine.

Added a test case failing before which is fixed now.

Change-Id: I04deb5b063d3ccba14c0fbf21522b02cb600ad1c
Signed-off-by: Marko Vukolic <mvu@zurich.ibm.com>

orderer/sbft/simplebft/checkpoint.go

@@ -88,9 +88,10 @@ func (s *SBFT) handleCheckpoint(c *Checkpoint, src uint64) {
 	c = s.cur.checkpoint[replicas[0]]
 
 	if !reflect.DeepEqual(c.Digest, s.cur.subject.Digest) {
-		log.Fatalf("replica %d: weak checkpoint %x does not match our state %x",
-			s.id, c.Digest, s.cur.subject.Digest)
-		// NOT REACHED
+		log.Warningf("replica %d: weak checkpoint %x does not match our state %x --- primary %d of view %d is probably Byzantine, sending view change",
+			s.id, c.Digest, s.cur.subject.Digest, s.primaryID(), s.view)
+		s.sendViewChange()
+		return
 	}
 
 	// ignore null requests

orderer/sbft/simplebft/simplebft_test.go

@@ -266,6 +266,55 @@ func TestByzPrimary(t *testing.T) {
 	}
 }
 
+func TestByzPrimaryBullyingSingleReplica(t *testing.T) {
+	skipInShortMode(t)
+	N := uint64(10)
+	sys := newTestSystem(N)
+	var repls []*SBFT
+	var adapters []*testSystemAdapter
+	for i := uint64(0); i < N; i++ {
+		a := sys.NewAdapter(i)
+		s, err := New(i, &Config{N: N, F: 1, BatchDurationNsec: 2000000000, BatchSizeBytes: 1, RequestTimeoutNsec: 20000000000}, a)
+		if err != nil {
+			t.Fatal(err)
+		}
+		repls = append(repls, s)
+		adapters = append(adapters, a)
+	}
+
+	r1 := []byte{1, 2, 3}
+	r2 := []byte{5, 6, 7}
+
+	// change preprepare to 1
+	sys.filterFn = func(e testElem) (testElem, bool) {
+		if msg, ok := e.ev.(*testMsgEvent); ok {
+			if pp := msg.msg.GetPreprepare(); pp != nil && msg.src == 0 && msg.dst == 1 {
+				pp := *pp
+				batch := *pp.Batch
+				batch.Payloads = [][]byte{r2}
+				pp.Batch = &batch
+				h := merkleHashData(batch.Payloads)
+				bh := &BatchHeader{}
+				proto.Unmarshal(pp.Batch.Header, bh)
+				bh.DataHash = h
+				bhraw, _ := proto.Marshal(bh)
+				pp.Batch.Header = bhraw
+				msg.msg = &Msg{&Msg_Preprepare{&pp}}
+			}
+		}
+		return e, true
+	}
+
+	connectAll(sys)
+	repls[0].Request(r1)
+	sys.Run()
+	for _, a := range adapters {
+		if a.id != 1 && len(a.batches) != 1 {
+			t.Fatal("expected execution of 1 batch at all except replica 1")
+		}
+	}
+}
+
 func TestViewChange(t *testing.T) {
 	skipInShortMode(t)
 	N := uint64(4)