fix(beacon): guard against nil finality fields and recover request panics

.github/workflows/golangci-lint.yaml

@@ -9,7 +9,7 @@ on:
 permissions:
   contents: read
   # Optional: allow read access to pull request. Use with `only-new-issues` option.
-  # pull-requests: read
+  pull-requests: read
 jobs:
   golangci:
     name: lint
@@ -32,7 +32,7 @@ jobs:
           # args: --issues-exit-code=0
 
           # Optional: show only new issues if it's a pull request. The default value is `false`.
-          # only-new-issues: true
+          only-new-issues: true
 
           # Optional: if set to true then the all caching functionality will be complete disabled,
           #           takes precedence over all other caching options.

pkg/beacon/checkpoints/majority/majority.go

@@ -18,12 +18,28 @@ func New() *Decider {
 }
 
 func (m *Decider) Decide(checkpoints []*v1.Finality) (*v1.Finality, error) {
+	// Checkpoints with missing fields can't be keyed and don't count towards
+	// the majority threshold, matching how upstreams that fail to return
+	// finality at all are treated.
+	valid := make([]*v1.Finality, 0, len(checkpoints))
+
+	for _, checkpoint := range checkpoints {
+		if checkpoint == nil ||
+			checkpoint.Finalized == nil ||
+			checkpoint.Justified == nil ||
+			checkpoint.PreviousJustified == nil {
+			continue
+		}
+
+		valid = append(valid, checkpoint)
+	}
+
 	common := make(map[string]struct {
 		Finality *v1.Finality
 		Count    int
-	})
+	}, len(valid))
 
-	for _, checkpoint := range checkpoints {
+	for _, checkpoint := range valid {
 		key := eth.RootAsString(checkpoint.Finalized.Root) + "-" +
 			eth.RootAsString(checkpoint.Justified.Root) + "-" +
 			eth.RootAsString(checkpoint.PreviousJustified.Root)
@@ -46,7 +62,7 @@ func (m *Decider) Decide(checkpoints []*v1.Finality) (*v1.Finality, error) {
 	}
 
 	for _, v := range common {
-		if v.Count > len(checkpoints)/2 {
+		if v.Count > len(valid)/2 {
 			return v.Finality, nil
 		}
 	}

pkg/beacon/checkpoints/majority/majority_test.go

@@ -88,3 +88,48 @@ func TestSplitMajority(t *testing.T) {
 		t.Errorf("Expected %v, got %v", ErrNoMajorityFound, err)
 	}
 }
+
+func TestNilFinalityIgnored(t *testing.T) {
+	payload := []*v1.Finality{
+		nil,
+		finalityA,
+		finalityA,
+		nil,
+	}
+
+	finality, err := majority.Decide(payload)
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	if finality.Finalized.Root != finalityA.Finalized.Root {
+		t.Errorf("Expected %v, got %v", finalityA, finality)
+	}
+}
+
+func TestNilCheckpointFieldsIgnored(t *testing.T) {
+	payload := []*v1.Finality{
+		{Finalized: nil, Justified: checkpointB, PreviousJustified: checkpointB},
+		{Finalized: checkpointA, Justified: nil, PreviousJustified: checkpointB},
+		{Finalized: checkpointA, Justified: checkpointB, PreviousJustified: nil},
+		finalityA,
+	}
+
+	finality, err := majority.Decide(payload)
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	if finality.Finalized.Root != finalityA.Finalized.Root {
+		t.Errorf("Expected %v, got %v", finalityA, finality)
+	}
+}
+
+func TestAllNilNoMajority(t *testing.T) {
+	payload := []*v1.Finality{nil, nil}
+
+	_, err := majority.Decide(payload)
+	if err != ErrNoMajorityFound {
+		t.Errorf("Expected %v, got %v", ErrNoMajorityFound, err)
+	}
+}

pkg/beacon/default.go

@@ -485,6 +485,15 @@ func (d *Default) checkFinality(ctx context.Context) error {
 			continue
 		}
 
+		if finality == nil ||
+			finality.Finalized == nil ||
+			finality.Justified == nil ||
+			finality.PreviousJustified == nil {
+			d.log.Infof("Node %s returned incomplete finality", node.Config.Name)
+
+			continue
+		}
+
 		aggFinality = append(aggFinality, finality)
 	}
 

pkg/checkpointz/checkpointz.go

@@ -60,6 +60,17 @@ func (s *Server) Start(ctx context.Context) error {
 
 	router := httprouter.New()
 
+	router.PanicHandler = func(w http.ResponseWriter, r *http.Request, rcv any) {
+		s.log.
+			WithField("panic", rcv).
+			WithField("path", r.URL.Path).
+			Error("Recovered from panic while handling request")
+
+		if err := api.WriteErrorResponse(w, "internal server error", http.StatusInternalServerError); err != nil {
+			s.log.WithError(err).Error("Failed to write panic error response")
+		}
+	}
+
 	if err := s.http.Register(ctx, router); err != nil {
 		return err
 	}