chore(types): harden DoubleSignEvidence (de)serialization

Author: CaelRowley

block/internal/syncing/doublesign_branches_test.go

@@ -230,6 +230,24 @@ func TestDoubleSignEvidence_FromProtoInnerHeaderError(t *testing.T) {
 	require.Error(t, dst.FromProto(p))
 }
 
+// FromProto must reject partial-nil sub-messages (one set, one nil) to keep
+// the (FirstHeader, AlternateHeader) pair invariant after deserialization.
+func TestDoubleSignEvidence_FromProtoPartialNilHeader(t *testing.T) {
+	env := newDSTestEnv(t)
+	hdr := env.signHeaderAtHeight(5, 0x01)
+	hdrPB, err := hdr.ToProto()
+	require.NoError(t, err)
+
+	t.Run("alternate nil", func(t *testing.T) {
+		dst := new(types.DoubleSignEvidence)
+		require.Error(t, dst.FromProto(&pb.DoubleSignEvidence{Height: 5, FirstHeader: hdrPB}))
+	})
+	t.Run("first nil", func(t *testing.T) {
+		dst := new(types.DoubleSignEvidence)
+		require.Error(t, dst.FromProto(&pb.DoubleSignEvidence{Height: 5, AlternateHeader: hdrPB}))
+	})
+}
+
 func TestDoubleSignEvidence_UnmarshalBinaryGarbage(t *testing.T) {
 	dst := new(types.DoubleSignEvidence)
 	require.Error(t, dst.UnmarshalBinary([]byte{0xff, 0xff, 0xff, 0xff}))

block/internal/syncing/doublesign_test.go

@@ -465,6 +465,11 @@ func TestDoubleSignEvidence_ValidateBasic(t *testing.T) {
 		e := &types.DoubleSignEvidence{Height: 5, FirstHeader: first, AlternateHeader: first}
 		require.Error(t, e.ValidateBasic())
 	})
+	t.Run("proposer mismatch", func(t *testing.T) {
+		other := env.signHeaderWithOtherProposer(5, 0x02)
+		e := &types.DoubleSignEvidence{Height: 5, FirstHeader: first, AlternateHeader: other}
+		require.ErrorContains(t, e.ValidateBasic(), "different proposers")
+	})
 	t.Run("happy path", func(t *testing.T) {
 		e := &types.DoubleSignEvidence{Height: 5, FirstHeader: first, AlternateHeader: alt}
 		require.NoError(t, e.ValidateBasic())

types/double_sign_evidence.go

@@ -55,6 +55,9 @@ func (e *DoubleSignEvidence) ToProto() (*pb.DoubleSignEvidence, error) {
 	if e == nil {
 		return nil, errors.New("evidence is nil")
 	}
+	if e.FirstHeader == nil || e.AlternateHeader == nil {
+		return nil, errors.New("evidence requires both first and alternate headers")
+	}
 	first, err := e.FirstHeader.ToProto()
 	if err != nil {
 		return nil, fmt.Errorf("marshal first header: %w", err)
@@ -111,7 +114,7 @@ func (e *DoubleSignEvidence) MarshalBinary() ([]byte, error) {
 func (e *DoubleSignEvidence) UnmarshalBinary(data []byte) error {
 	p := new(pb.DoubleSignEvidence)
 	if err := proto.Unmarshal(data, p); err != nil {
-		return err
+		return fmt.Errorf("proto unmarshal double sign evidence: %w", err)
 	}
 	return e.FromProto(p)
 }