core: implement Neo.Witness.GetVerificationScript interop

pkg/core/interop_neo.go

@@ -216,6 +216,20 @@ func (ic *interopContext) invocationTxGetScript(v *vm.VM) error {
 	return nil
 }
 
+// witnessGetVerificationScript returns current witness' script.
+func (ic *interopContext) witnessGetVerificationScript(v *vm.VM) error {
+	witInterface := v.Estack().Pop().Value()
+	wit, ok := witInterface.(*transaction.Witness)
+	if !ok {
+		return errors.New("value is not a witness")
+	}
+	// It's important not to share wit.VerificationScript slice with the code running in VM.
+	script := make([]byte, len(wit.VerificationScript))
+	copy(script, wit.VerificationScript)
+	v.Estack().PushVal(script)
+	return nil
+}
+
 // bcGetValidators returns validators.
 func (ic *interopContext) bcGetValidators(v *vm.VM) error {
 	validators := ic.dao.GetValidators()

pkg/core/interop_neo_test.go

@@ -126,6 +126,19 @@ func TestInvocationTxGetScript(t *testing.T) {
 	require.Equal(t, inv.Script, value)
 }
 
+func TestWitnessGetVerificationScript(t *testing.T) {
+	v := vm.New()
+	script := []byte{byte(opcode.PUSHM1), byte(opcode.RET)}
+	witness := transaction.Witness{InvocationScript: nil, VerificationScript: script}
+
+	context := newInteropContext(trigger.Application, newTestChain(t), storage.NewMemoryStore(), nil, nil)
+	v.Estack().PushVal(vm.NewInteropItem(&witness))
+	err := context.witnessGetVerificationScript(v)
+	require.NoError(t, err)
+	value := v.Estack().Pop().Value().([]byte)
+	require.Equal(t, witness.VerificationScript, value)
+}
+
 func TestPopInputFromVM(t *testing.T) {
 	v, tx, _ := createVMAndTX(t)
 	v.Estack().PushVal(vm.NewInteropItem(&tx.Inputs[0]))

pkg/core/interops.go

@@ -175,6 +175,7 @@ var neoInterops = []interopedFunction{
 	{Name: "Neo.Transaction.GetType", Func: (*interopContext).txGetType, Price: 1},
 	{Name: "Neo.Transaction.GetUnspentCoins", Func: (*interopContext).txGetUnspentCoins, Price: 200},
 	{Name: "Neo.Transaction.GetWitnesses", Func: (*interopContext).txGetWitnesses, Price: 200},
+	{Name: "Neo.Witness.GetVerificationScript", Func: (*interopContext).witnessGetVerificationScript, Price: 100},
 	//		{Name: "Neo.Enumerator.Concat", Func: (*interopContext).enumeratorConcat, Price: 1},
 	//		{Name: "Neo.Enumerator.Create", Func: (*interopContext).enumeratorCreate, Price: 1},
 	//		{Name: "Neo.Enumerator.Next", Func: (*interopContext).enumeratorNext, Price: 1},
@@ -187,7 +188,6 @@ var neoInterops = []interopedFunction{
 	{Name: "Neo.Runtime.Deserialize", Func: (*interopContext).runtimeDeserialize, Price: 1},
 	{Name: "Neo.Runtime.Serialize", Func: (*interopContext).runtimeSerialize, Price: 1},
 	//		{Name: "Neo.Storage.Find",                Func: (*interopContext).storageFind, Price: 1},
-	//		{Name: "Neo.Witness.GetVerificationScript", Func: (*interopContext).witnessGetVerificationScript, Price: 100},
 
 	// Aliases.
 	//		{Name: "Neo.Iterator.Next", Func: (*interopContext).enumeratorNext, Price: 1},