Merge pull request #650 from nspcc-dev/handle-bad-notifications

Handle bad notifications

pkg/core/interop_system.go

@@ -343,7 +343,17 @@ func (ic *interopContext) runtimeCheckWitness(v *vm.VM) error {
 func (ic *interopContext) runtimeNotify(v *vm.VM) error {
 	// It can be just about anything.
 	e := v.Estack().Pop()
-	ne := state.NotificationEvent{ScriptHash: getContextScriptHash(v, 0), Item: e.Item()}
+	item := e.Item()
+	// But it has to be serializable, otherwise we either have some broken
+	// (recursive) structure inside or an interop item that can't be used
+	// outside of the interop subsystem anyway. I'd probably fail transactions
+	// that emit such broken notifications, but that might break compatibility
+	// with testnet/mainnet, so we're replacing these with error messages.
+	_, err := vm.SerializeItem(item)
+	if err != nil {
+		item = vm.NewByteArrayItem([]byte(fmt.Sprintf("bad notification: %v", err)))
+	}
+	ne := state.NotificationEvent{ScriptHash: getContextScriptHash(v, 0), Item: item}
 	ic.notifications = append(ic.notifications, ne)
 	return nil
 }

pkg/vm/interop.go

@@ -93,7 +93,7 @@ func runtimeNotify(vm *VM) error {
 // RuntimeSerialize handles syscalls System.Runtime.Serialize and Neo.Runtime.Serialize.
 func RuntimeSerialize(vm *VM) error {
 	item := vm.Estack().Pop()
-	data, err := serializeItem(item.value)
+	data, err := SerializeItem(item.value)
 	if err != nil {
 		return err
 	} else if len(data) > MaxItemSize {
@@ -109,7 +109,7 @@ func RuntimeSerialize(vm *VM) error {
 func RuntimeDeserialize(vm *VM) error {
 	data := vm.Estack().Pop().Bytes()
 
-	item, err := deserializeItem(data)
+	item, err := DeserializeItem(data)
 	if err != nil {
 		return err
 	}

pkg/vm/serialization.go

@@ -17,7 +17,8 @@ const (
 	mapT       stackItemType = 0x82
 )
 
-func serializeItem(item StackItem) ([]byte, error) {
+// SerializeItem encodes given StackItem into the byte slice.
+func SerializeItem(item StackItem) ([]byte, error) {
 	w := io.NewBufBinWriter()
 	EncodeBinaryStackItem(item, w.BinWriter)
 	if w.Err != nil {
@@ -35,7 +36,7 @@ func EncodeBinaryStackItem(item StackItem, w *io.BinWriter) {
 
 func serializeItemTo(item StackItem, w *io.BinWriter, seen map[StackItem]bool) {
 	if seen[item] {
-		w.Err = errors.New("recursive structures are not supported")
+		w.Err = errors.New("recursive structures can't be serialized")
 		return
 	}
 
@@ -50,7 +51,7 @@ func serializeItemTo(item StackItem, w *io.BinWriter, seen map[StackItem]bool) {
 		w.WriteBytes([]byte{byte(integerT)})
 		w.WriteVarBytes(IntToBytes(t.value))
 	case *InteropItem:
-		w.Err = errors.New("not supported")
+		w.Err = errors.New("interop item can't be serialized")
 	case *ArrayItem, *StructItem:
 		seen[item] = true
 
@@ -78,7 +79,8 @@ func serializeItemTo(item StackItem, w *io.BinWriter, seen map[StackItem]bool) {
 	}
 }
 
-func deserializeItem(data []byte) (StackItem, error) {
+// DeserializeItem decodes StackItem from the given byte slice.
+func DeserializeItem(data []byte) (StackItem, error) {
 	r := io.NewBinReaderFromBuf(data)
 	item := DecodeBinaryStackItem(r)
 	if r.Err != nil {

pkg/vm/vm_test.go

@@ -653,7 +653,7 @@ func TestDeserializeUnknown(t *testing.T) {
 	prog := append(getSyscallProg("Neo.Runtime.Deserialize"), byte(opcode.RET))
 	vm := load(prog)
 
-	data, err := serializeItem(NewBigIntegerItem(123))
+	data, err := SerializeItem(NewBigIntegerItem(123))
 	require.NoError(t, err)
 
 	data[0] = 0xFF