fix: guard nil light client attack signed header

Author: UnbornAztecKing

types/evidence.go

@@ -357,6 +357,10 @@ func (l *LightClientAttackEvidence) ValidateBasic() error {
 		return errors.New("conflicting block is nil")
 	}
 
+	if l.ConflictingBlock.SignedHeader == nil {
+		return errors.New("conflicting block missing signed header")
+	}
+
 	// this check needs to be done before we can run validate basic
 	if l.ConflictingBlock.Header == nil {
 		return errors.New("conflicting block missing header")

types/evidence_test.go

@@ -193,6 +193,7 @@ func TestLightClientAttackEvidenceValidation(t *testing.T) {
 		{"Height is equal to the divergent block", func(ev *LightClientAttackEvidence) {
 			ev.CommonHeight = height
 		}, false},
+		{"Nil conflicting signed header", func(ev *LightClientAttackEvidence) { ev.ConflictingBlock.SignedHeader = nil }, true},
 		{"Nil conflicting header", func(ev *LightClientAttackEvidence) { ev.ConflictingBlock.Header = nil }, true},
 		{"Nil conflicting blocl", func(ev *LightClientAttackEvidence) { ev.ConflictingBlock = nil }, true},
 		{"Nil validator set", func(ev *LightClientAttackEvidence) {
@@ -229,6 +230,26 @@ func TestLightClientAttackEvidenceValidation(t *testing.T) {
 
 }
 
+func TestLightClientAttackEvidenceFromProtoNilConflictingSignedHeader(t *testing.T) {
+	height := int64(5)
+	_, valSet, _ := randVoteSet(height, 1, cmtproto.PrecommitType, 10, 1, false)
+	valsProto, err := valSet.ToProto()
+	require.NoError(t, err)
+
+	evidenceProto := &cmtproto.LightClientAttackEvidence{
+		ConflictingBlock: &cmtproto.LightBlock{
+			ValidatorSet: valsProto,
+		},
+		CommonHeight:     height - 1,
+		TotalVotingPower: valSet.TotalVotingPower(),
+	}
+
+	require.NotPanics(t, func() {
+		_, err = LightClientAttackEvidenceFromProto(evidenceProto)
+	})
+	require.ErrorContains(t, err, "conflicting block missing signed header")
+}
+
 func TestMockEvidenceValidateBasic(t *testing.T) {
 	goodEvidence, err := NewMockDuplicateVoteEvidence(int64(1), time.Now(), "mock-chain-id")
 	require.NoError(t, err)