Fix V-DOGE-VUL-007 (#40)

* Fix crash when faulty node send nil gossip transaction to peer

* Add unit test

* Fix lint error of nlreturn

* More accurate test cases of addGossipTx

txpool/txpool.go

@@ -677,7 +677,19 @@ func (p *TxPool) addGossipTx(obj interface{}) {
 		return
 	}
 
-	raw := obj.(*proto.Txn) // nolint:forcetypeassert
+	raw, ok := obj.(*proto.Txn)
+	if !ok {
+		p.logger.Warn("gossip tx(%+v) is not a transaction", obj)
+
+		return
+	}
+
+	if raw.Raw == nil || len(raw.Raw.Value) == 0 {
+		p.logger.Info("gossip tx raw data is empty")
+
+		return
+	}
+
 	tx := new(types.Transaction)
 
 	// decode tx

txpool/txpool_test.go

@@ -15,6 +15,7 @@ import (
 	"github.com/golang/protobuf/ptypes/any"
 	"github.com/hashicorp/go-hclog"
 	"github.com/stretchr/testify/assert"
+	"google.golang.org/protobuf/types/known/anypb"
 )
 
 const (
@@ -390,6 +391,40 @@ func TestDropKnownGossipTx(t *testing.T) {
 	assert.Equal(t, uint64(1), pool.accounts.get(addr1).enqueued.length())
 }
 
+func TestAddGossipTx_ShouldNotCrash(t *testing.T) {
+	pool, err := newTestPool()
+	assert.NoError(t, err)
+	pool.SetSigner(&mockSigner{})
+
+	assert.NotPanics(t, func() {
+		// type assertion
+		pool.addGossipTx(&types.Block{Header: &types.Header{Number: 10}})
+	})
+
+	assert.Nil(t, pool.accounts.get(addr1), "addr in txpool should be nil")
+
+	assert.NotPanics(t, func() {
+		pool.addGossipTx(createNilRawTxn())
+		pool.addGossipTx(createNilRawDataTxn())
+	})
+
+	assert.Nil(t, pool.accounts.get(addr1), "addr in txpool should be nil")
+}
+
+func createNilRawTxn() *proto.Txn {
+	return &proto.Txn{
+		Raw: nil,
+	}
+}
+
+func createNilRawDataTxn() *proto.Txn {
+	return &proto.Txn{
+		Raw: &anypb.Any{
+			Value: nil,
+		},
+	}
+}
+
 func TestAddHandler(t *testing.T) {
 	t.Run("enqueue new tx with higher nonce", func(t *testing.T) {
 		pool, err := newTestPool()