core: implement System.Callback.CreateFromSyscall interop

Allow to create callbacks from syscalls.

Signed-off-by: Evgenii Stratonikov <evgeniy@nspcc.ru>

pkg/core/interop/callback/callback.go

@@ -25,10 +25,12 @@ func Invoke(ic *interop.Context, v *vm.VM) error {
 		return errors.New("invalid argument count")
 	}
 	cb.LoadContext(v, args)
-	switch cb.(type) {
+	switch t := cb.(type) {
 	case *MethodCallback:
 		id := emit.InteropNameToID([]byte("System.Contract.Call"))
 		return ic.SyscallHandler(v, id)
+	case *SyscallCallback:
+		return ic.SyscallHandler(v, t.desc.ID)
 	default:
 		return nil
 	}

pkg/core/interop/callback/syscall.go

@@ -0,0 +1,39 @@
+package callback
+
+import (
+	"errors"
+
+	"github.com/nspcc-dev/neo-go/pkg/core/interop"
+	"github.com/nspcc-dev/neo-go/pkg/vm"
+	"github.com/nspcc-dev/neo-go/pkg/vm/stackitem"
+)
+
+// SyscallCallback represents callback for a syscall.
+type SyscallCallback struct {
+	desc *interop.Function
+}
+
+var _ Callback = (*SyscallCallback)(nil)
+
+// ArgCount implements Callback interface.
+func (p *SyscallCallback) ArgCount() int {
+	return p.desc.ParamCount
+}
+
+// LoadContext implements Callback interface.
+func (p *SyscallCallback) LoadContext(v *vm.VM, args []stackitem.Item) {
+	for i := len(args) - 1; i >= 0; i-- {
+		v.Estack().PushVal(args[i])
+	}
+}
+
+// CreateFromSyscall creates callback from syscall.
+func CreateFromSyscall(ic *interop.Context, v *vm.VM) error {
+	id := uint32(v.Estack().Pop().BigInt().Int64())
+	f := ic.GetFunction(id)
+	if f == nil {
+		return errors.New("syscall not found")
+	}
+	v.Estack().PushVal(stackitem.NewInterop(&SyscallCallback{f}))
+	return nil
+}

pkg/core/interop/context.go

@@ -65,6 +65,8 @@ type Function struct {
 	ID   uint32
 	Name string
 	Func func(*Context, *vm.VM) error
+	// ParamCount is a number of function parameters.
+	ParamCount int
 	Price      int64
 	// RequiredFlags is a set of flags which must be set during script invocations.
 	// Default value is NoneFlag i.e. no flags are required.

pkg/core/interop_system_test.go

@@ -6,6 +6,7 @@ import (
 
 	"github.com/nspcc-dev/dbft/crypto"
 	"github.com/nspcc-dev/neo-go/pkg/config/netmode"
+	"github.com/nspcc-dev/neo-go/pkg/core/interop"
 	"github.com/nspcc-dev/neo-go/pkg/core/interop/callback"
 	"github.com/nspcc-dev/neo-go/pkg/core/interop/runtime"
 	"github.com/nspcc-dev/neo-go/pkg/core/state"
@@ -837,3 +838,42 @@ func TestMethodCallback(t *testing.T) {
 		require.Equal(t, big.NewInt(42), v.Estack().Pop().Item().Value())
 	})
 }
+func TestSyscallCallback(t *testing.T) {
+	_, ic, bc := createVM(t)
+	defer bc.Close()
+
+	ic.Functions = append(ic.Functions, []interop.Function{
+		{
+			ID: 0x42,
+			Func: func(_ *interop.Context, v *vm.VM) error {
+				a := v.Estack().Pop().BigInt()
+				b := v.Estack().Pop().BigInt()
+				v.Estack().PushVal(new(big.Int).Add(a, b))
+				return nil
+			},
+			ParamCount: 2,
+		},
+	})
+
+	t.Run("Good", func(t *testing.T) {
+		args := stackitem.NewArray([]stackitem.Item{stackitem.Make(12), stackitem.Make(30)})
+		v := loadScript([]byte{byte(opcode.RET)}, args, 0x42)
+		require.NoError(t, callback.CreateFromSyscall(ic, v))
+		require.NoError(t, callback.Invoke(ic, v))
+		require.Equal(t, 1, v.Estack().Len())
+		require.Equal(t, big.NewInt(42), v.Estack().Pop().Item().Value())
+	})
+
+	t.Run("Invalid", func(t *testing.T) {
+		t.Run("InvalidParameterCount", func(t *testing.T) {
+			args := stackitem.NewArray([]stackitem.Item{stackitem.Make(12)})
+			v := loadScript([]byte{byte(opcode.RET)}, args, 0x42)
+			require.NoError(t, callback.CreateFromSyscall(ic, v))
+			require.Error(t, callback.Invoke(ic, v))
+		})
+		t.Run("MissingSyscall", func(t *testing.T) {
+			v := loadScript([]byte{byte(opcode.RET)}, stackitem.NewArray(nil), 0x43)
+			require.Error(t, callback.CreateFromSyscall(ic, v))
+		})
+	})
+}

pkg/core/interops.go

@@ -31,70 +31,86 @@ func SpawnVM(ic *interop.Context) *vm.VM {
 
 // All lists are sorted, keep 'em this way, please.
 var systemInterops = []interop.Function{
-	{Name: "System.Binary.Base64Decode", Func: runtimeDecode, Price: 100000},
+	{Name: "System.Binary.Base64Decode", Func: runtimeDecode, Price: 100000, ParamCount: 1},
-	{Name: "System.Binary.Base64Encode", Func: runtimeEncode, Price: 100000},
+	{Name: "System.Binary.Base64Encode", Func: runtimeEncode, Price: 100000, ParamCount: 1},
-	{Name: "System.Binary.Deserialize", Func: runtimeDeserialize, Price: 500000},
+	{Name: "System.Binary.Deserialize", Func: runtimeDeserialize, Price: 500000, ParamCount: 1},
-	{Name: "System.Binary.Serialize", Func: runtimeSerialize, Price: 100000},
+	{Name: "System.Binary.Serialize", Func: runtimeSerialize, Price: 100000, ParamCount: 1},
-	{Name: "System.Blockchain.GetBlock", Func: bcGetBlock, Price: 2500000, RequiredFlags: smartcontract.AllowStates},
+	{Name: "System.Blockchain.GetBlock", Func: bcGetBlock, Price: 2500000,
-	{Name: "System.Blockchain.GetContract", Func: bcGetContract, Price: 1000000, RequiredFlags: smartcontract.AllowStates},
+		RequiredFlags: smartcontract.AllowStates, ParamCount: 1},
-	{Name: "System.Blockchain.GetHeight", Func: bcGetHeight, Price: 400, RequiredFlags: smartcontract.AllowStates},
+	{Name: "System.Blockchain.GetContract", Func: bcGetContract, Price: 1000000,
-	{Name: "System.Blockchain.GetTransaction", Func: bcGetTransaction, Price: 1000000, RequiredFlags: smartcontract.AllowStates},
+		RequiredFlags: smartcontract.AllowStates, ParamCount: 1},
-	{Name: "System.Blockchain.GetTransactionFromBlock", Func: bcGetTransactionFromBlock, Price: 1000000, RequiredFlags: smartcontract.AllowStates},
+	{Name: "System.Blockchain.GetHeight", Func: bcGetHeight, Price: 400,
-	{Name: "System.Blockchain.GetTransactionHeight", Func: bcGetTransactionHeight, Price: 1000000, RequiredFlags: smartcontract.AllowStates},
-	{Name: "System.Callback.Create", Func: callback.Create, Price: 400},
-	{Name: "System.Callback.CreateFromMethod", Func: callback.CreateFromMethod, Price: 1000000},
-	{Name: "System.Callback.Invoke", Func: callback.Invoke, Price: 1000000},
-	{Name: "System.Contract.Call", Func: contractCall, Price: 1000000, RequiredFlags: smartcontract.AllowCall},
-	{Name: "System.Contract.CallEx", Func: contractCallEx, Price: 1000000, RequiredFlags: smartcontract.AllowCall},
-	{Name: "System.Contract.Create", Func: contractCreate, Price: 0, RequiredFlags: smartcontract.AllowModifyStates},
-	{Name: "System.Contract.CreateStandardAccount", Func: contractCreateStandardAccount, Price: 10000},
-	{Name: "System.Contract.Destroy", Func: contractDestroy, Price: 1000000, RequiredFlags: smartcontract.AllowModifyStates},
-	{Name: "System.Contract.IsStandard", Func: contractIsStandard, Price: 30000},
-	{Name: "System.Contract.GetCallFlags", Func: contractGetCallFlags, Price: 30000},
-	{Name: "System.Contract.Update", Func: contractUpdate, Price: 0, RequiredFlags: smartcontract.AllowModifyStates},
-	{Name: "System.Enumerator.Concat", Func: enumerator.Concat, Price: 400},
-	{Name: "System.Enumerator.Create", Func: enumerator.Create, Price: 400},
-	{Name: "System.Enumerator.Next", Func: enumerator.Next, Price: 1000000},
-	{Name: "System.Enumerator.Value", Func: enumerator.Value, Price: 400},
-	{Name: "System.Iterator.Concat", Func: iterator.Concat, Price: 400},
-	{Name: "System.Iterator.Create", Func: iterator.Create, Price: 400},
-	{Name: "System.Iterator.Key", Func: iterator.Key, Price: 400},
-	{Name: "System.Iterator.Keys", Func: iterator.Keys, Price: 400},
-	{Name: "System.Iterator.Values", Func: iterator.Values, Price: 400},
-	{Name: "System.Json.Deserialize", Func: json.Deserialize, Price: 500000},
-	{Name: "System.Json.Serialize", Func: json.Serialize, Price: 100000},
-	{Name: "System.Runtime.CheckWitness", Func: runtime.CheckWitness, Price: 30000,
 		RequiredFlags: smartcontract.AllowStates},
+	{Name: "System.Blockchain.GetTransaction", Func: bcGetTransaction, Price: 1000000,
+		RequiredFlags: smartcontract.AllowStates, ParamCount: 1},
+	{Name: "System.Blockchain.GetTransactionFromBlock", Func: bcGetTransactionFromBlock, Price: 1000000,
+		RequiredFlags: smartcontract.AllowStates, ParamCount: 2},
+	{Name: "System.Blockchain.GetTransactionHeight", Func: bcGetTransactionHeight, Price: 1000000,
+		RequiredFlags: smartcontract.AllowStates, ParamCount: 1},
+	{Name: "System.Callback.Create", Func: callback.Create, Price: 400, ParamCount: 3},
+	{Name: "System.Callback.CreateFromMethod", Func: callback.CreateFromMethod, Price: 1000000, ParamCount: 2},
+	{Name: "System.Callback.CreateFromSyscall", Func: callback.CreateFromSyscall, Price: 400, ParamCount: 1},
+	{Name: "System.Callback.Invoke", Func: callback.Invoke, Price: 1000000, ParamCount: 2},
+	{Name: "System.Contract.Call", Func: contractCall, Price: 1000000,
+		RequiredFlags: smartcontract.AllowCall, ParamCount: 3},
+	{Name: "System.Contract.CallEx", Func: contractCallEx, Price: 1000000,
+		RequiredFlags: smartcontract.AllowCall, ParamCount: 4},
+	{Name: "System.Contract.Create", Func: contractCreate, Price: 0,
+		RequiredFlags: smartcontract.AllowModifyStates, ParamCount: 2},
+	{Name: "System.Contract.CreateStandardAccount", Func: contractCreateStandardAccount, Price: 10000, ParamCount: 1},
+	{Name: "System.Contract.Destroy", Func: contractDestroy, Price: 1000000, RequiredFlags: smartcontract.AllowModifyStates},
+	{Name: "System.Contract.IsStandard", Func: contractIsStandard, Price: 30000, ParamCount: 1},
+	{Name: "System.Contract.GetCallFlags", Func: contractGetCallFlags, Price: 30000},
+	{Name: "System.Contract.Update", Func: contractUpdate, Price: 0,
+		RequiredFlags: smartcontract.AllowModifyStates, ParamCount: 2},
+	{Name: "System.Enumerator.Concat", Func: enumerator.Concat, Price: 400, ParamCount: 2},
+	{Name: "System.Enumerator.Create", Func: enumerator.Create, Price: 400, ParamCount: 1},
+	{Name: "System.Enumerator.Next", Func: enumerator.Next, Price: 1000000, ParamCount: 1},
+	{Name: "System.Enumerator.Value", Func: enumerator.Value, Price: 400, ParamCount: 1},
+	{Name: "System.Iterator.Concat", Func: iterator.Concat, Price: 400, ParamCount: 2},
+	{Name: "System.Iterator.Create", Func: iterator.Create, Price: 400, ParamCount: 1},
+	{Name: "System.Iterator.Key", Func: iterator.Key, Price: 400, ParamCount: 1},
+	{Name: "System.Iterator.Keys", Func: iterator.Keys, Price: 400, ParamCount: 1},
+	{Name: "System.Iterator.Values", Func: iterator.Values, Price: 400, ParamCount: 1},
+	{Name: "System.Json.Deserialize", Func: json.Deserialize, Price: 500000, ParamCount: 1},
+	{Name: "System.Json.Serialize", Func: json.Serialize, Price: 100000, ParamCount: 1},
+	{Name: "System.Runtime.CheckWitness", Func: runtime.CheckWitness, Price: 30000,
+		RequiredFlags: smartcontract.AllowStates, ParamCount: 1},
 	{Name: "System.Runtime.GasLeft", Func: runtime.GasLeft, Price: 400},
 	{Name: "System.Runtime.GetCallingScriptHash", Func: engineGetCallingScriptHash, Price: 400},
 	{Name: "System.Runtime.GetEntryScriptHash", Func: engineGetEntryScriptHash, Price: 400},
 	{Name: "System.Runtime.GetExecutingScriptHash", Func: engineGetExecutingScriptHash, Price: 400},
 	{Name: "System.Runtime.GetInvocationCounter", Func: runtime.GetInvocationCounter, Price: 400},
-	{Name: "System.Runtime.GetNotifications", Func: runtime.GetNotifications, Price: 10000},
+	{Name: "System.Runtime.GetNotifications", Func: runtime.GetNotifications, Price: 10000, ParamCount: 1},
 	{Name: "System.Runtime.GetScriptContainer", Func: engineGetScriptContainer, Price: 250},
 	{Name: "System.Runtime.GetTime", Func: runtimeGetTime, Price: 250, RequiredFlags: smartcontract.AllowStates},
 	{Name: "System.Runtime.GetTrigger", Func: runtimeGetTrigger, Price: 250},
-	{Name: "System.Runtime.Log", Func: runtimeLog, Price: 1000000, RequiredFlags: smartcontract.AllowNotify},
+	{Name: "System.Runtime.Log", Func: runtimeLog, Price: 1000000, RequiredFlags: smartcontract.AllowNotify, ParamCount: 1},
-	{Name: "System.Runtime.Notify", Func: runtimeNotify, Price: 1000000, RequiredFlags: smartcontract.AllowNotify},
+	{Name: "System.Runtime.Notify", Func: runtimeNotify, Price: 1000000, RequiredFlags: smartcontract.AllowNotify, ParamCount: 2},
 	{Name: "System.Runtime.Platform", Func: runtimePlatform, Price: 250},
-	{Name: "System.Storage.Delete", Func: storageDelete, Price: StoragePrice, RequiredFlags: smartcontract.AllowModifyStates},
+	{Name: "System.Storage.Delete", Func: storageDelete, Price: StoragePrice,
-	{Name: "System.Storage.Find", Func: storageFind, Price: 1000000, RequiredFlags: smartcontract.AllowStates},
+		RequiredFlags: smartcontract.AllowModifyStates, ParamCount: 2},
-	{Name: "System.Storage.Get", Func: storageGet, Price: 1000000, RequiredFlags: smartcontract.AllowStates},
+	{Name: "System.Storage.Find", Func: storageFind, Price: 1000000, RequiredFlags: smartcontract.AllowStates, ParamCount: 2},
+	{Name: "System.Storage.Get", Func: storageGet, Price: 1000000, RequiredFlags: smartcontract.AllowStates, ParamCount: 2},
 	{Name: "System.Storage.GetContext", Func: storageGetContext, Price: 400, RequiredFlags: smartcontract.AllowStates},
 	{Name: "System.Storage.GetReadOnlyContext", Func: storageGetReadOnlyContext, Price: 400, RequiredFlags: smartcontract.AllowStates},
-	{Name: "System.Storage.Put", Func: storagePut, Price: 0, RequiredFlags: smartcontract.AllowModifyStates}, // These don't have static price in C# code.
+	{Name: "System.Storage.Put", Func: storagePut, Price: 0, RequiredFlags: smartcontract.AllowModifyStates,
-	{Name: "System.Storage.PutEx", Func: storagePutEx, Price: 0, RequiredFlags: smartcontract.AllowModifyStates},
+		ParamCount: 3}, // These don't have static price in C# code.
-	{Name: "System.Storage.AsReadOnly", Func: storageContextAsReadOnly, Price: 400, RequiredFlags: smartcontract.AllowStates},
+	{Name: "System.Storage.PutEx", Func: storagePutEx, Price: 0, RequiredFlags: smartcontract.AllowModifyStates, ParamCount: 4},
+	{Name: "System.Storage.AsReadOnly", Func: storageContextAsReadOnly, Price: 400,
+		RequiredFlags: smartcontract.AllowStates, ParamCount: 1},
 }
 
 var neoInterops = []interop.Function{
-	{Name: "Neo.Crypto.VerifyWithECDsaSecp256r1", Func: crypto.ECDSASecp256r1Verify, Price: crypto.ECDSAVerifyPrice},
+	{Name: "Neo.Crypto.VerifyWithECDsaSecp256r1", Func: crypto.ECDSASecp256r1Verify,
-	{Name: "Neo.Crypto.VerifyWithECDsaSecp256k1", Func: crypto.ECDSASecp256k1Verify, Price: crypto.ECDSAVerifyPrice},
+		Price: crypto.ECDSAVerifyPrice, ParamCount: 3},
-	{Name: "Neo.Crypto.CheckMultisigWithECDsaSecp256r1", Func: crypto.ECDSASecp256r1CheckMultisig, Price: 0},
+	{Name: "Neo.Crypto.VerifyWithECDsaSecp256k1", Func: crypto.ECDSASecp256k1Verify,
-	{Name: "Neo.Crypto.CheckMultisigWithECDsaSecp256k1", Func: crypto.ECDSASecp256k1CheckMultisig, Price: 0},
+		Price: crypto.ECDSAVerifyPrice, ParamCount: 3},
-	{Name: "Neo.Crypto.SHA256", Func: crypto.Sha256, Price: 1000000},
+	{Name: "Neo.Crypto.CheckMultisigWithECDsaSecp256r1", Func: crypto.ECDSASecp256r1CheckMultisig, Price: 0, ParamCount: 3},
-	{Name: "Neo.Crypto.RIPEMD160", Func: crypto.RipeMD160, Price: 1000000},
+	{Name: "Neo.Crypto.CheckMultisigWithECDsaSecp256k1", Func: crypto.ECDSASecp256k1CheckMultisig, Price: 0, ParamCount: 3},
-	{Name: "Neo.Native.Call", Func: native.Call, Price: 0},
+	{Name: "Neo.Crypto.SHA256", Func: crypto.Sha256, Price: 1000000, ParamCount: 1},
+	{Name: "Neo.Crypto.RIPEMD160", Func: crypto.RipeMD160, Price: 1000000, ParamCount: 1},
+	{Name: "Neo.Native.Call", Func: native.Call, Price: 0, ParamCount: 1},
 	{Name: "Neo.Native.Deploy", Func: native.Deploy, Price: 0, RequiredFlags: smartcontract.AllowModifyStates},
 }