Merge pull request #706 from nspcc-dev/feature/transfer

cli: implement transfer from multisig accounts

cli/wallet/multisig.go

@@ -0,0 +1,135 @@
+package wallet
+
+import (
+	"encoding/json"
+	"fmt"
+	"io/ioutil"
+
+	"github.com/nspcc-dev/neo-go/pkg/core/transaction"
+	"github.com/nspcc-dev/neo-go/pkg/encoding/address"
+	"github.com/nspcc-dev/neo-go/pkg/rpc/client"
+	"github.com/nspcc-dev/neo-go/pkg/smartcontract/context"
+	"github.com/urfave/cli"
+)
+
+func newMultisigCommands() []cli.Command {
+	return []cli.Command{
+		{
+			Name:      "sign",
+			Usage:     "sign a transaction",
+			UsageText: "multisig sign --path <path> --addr <addr> --in <file.in> --out <file.out>",
+			Action:    signMultisig,
+			Flags: []cli.Flag{
+				walletPathFlag,
+				rpcFlag,
+				timeoutFlag,
+				outFlag,
+				inFlag,
+				cli.StringFlag{
+					Name:  "addr",
+					Usage: "Address to use",
+				},
+			},
+		},
+	}
+}
+
+func signMultisig(ctx *cli.Context) error {
+	wall, err := openWallet(ctx.String("path"))
+	if err != nil {
+		return cli.NewExitError(err, 1)
+	}
+	defer wall.Close()
+
+	c, err := readParameterContext(ctx.String("in"))
+	if err != nil {
+		return cli.NewExitError(err, 1)
+	}
+	addr := ctx.String("addr")
+	sh, err := address.StringToUint160(addr)
+	if err != nil {
+		return cli.NewExitError(fmt.Errorf("invalid address: %v", err), 1)
+	}
+	acc := wall.GetAccount(sh)
+	if acc == nil {
+		return cli.NewExitError(fmt.Errorf("can't find account for the address: %s", addr), 1)
+	}
+
+	tx, ok := c.Verifiable.(*transaction.Transaction)
+	if !ok {
+		return cli.NewExitError("verifiable item is not a transaction", 1)
+	}
+	printTxInfo(tx)
+	fmt.Println("Enter password to unlock wallet and sign the transaction")
+	pass, err := readPassword("Password > ")
+	if err != nil {
+		return cli.NewExitError(err, 1)
+	} else if err := acc.Decrypt(pass); err != nil {
+		return cli.NewExitError(fmt.Errorf("can't unlock an account: %v", err), 1)
+	}
+
+	priv := acc.PrivateKey()
+	sign := priv.Sign(tx.GetSignedPart())
+	if err := c.AddSignature(acc.Contract, priv.PublicKey(), sign); err != nil {
+		return cli.NewExitError(fmt.Errorf("can't add signature: %v", err), 1)
+	} else if err := writeParameterContext(c, ctx.String("out")); err != nil {
+		return cli.NewExitError(err, 1)
+	}
+	if endpoint := ctx.String("rpc"); endpoint != "" {
+		w, err := c.GetWitness(acc.Contract)
+		if err != nil {
+			return cli.NewExitError(err, 1)
+		}
+		tx.Scripts = append(tx.Scripts, *w)
+
+		gctx, cancel := getGoContext(ctx)
+		defer cancel()
+
+		c, err := client.New(gctx, ctx.String("rpc"), client.Options{})
+		if err != nil {
+			return cli.NewExitError(err, 1)
+		} else if err := c.SendRawTransaction(tx); err != nil {
+			return cli.NewExitError(err, 1)
+		}
+	}
+
+	fmt.Println(tx.Hash().StringLE())
+	return nil
+}
+
+func readParameterContext(filename string) (*context.ParameterContext, error) {
+	data, err := ioutil.ReadFile(filename)
+	if err != nil {
+		return nil, fmt.Errorf("can't read input file: %v", err)
+	}
+
+	c := new(context.ParameterContext)
+	if err := json.Unmarshal(data, c); err != nil {
+		return nil, fmt.Errorf("can't parse transaction: %v", err)
+	}
+	return c, nil
+}
+
+func writeParameterContext(c *context.ParameterContext, filename string) error {
+	if data, err := json.Marshal(c); err != nil {
+		return fmt.Errorf("can't marshal transaction: %v", err)
+	} else if err := ioutil.WriteFile(filename, data, 0644); err != nil {
+		return fmt.Errorf("can't write transaction to file: %v", err)
+	}
+	return nil
+}
+
+func printTxInfo(t *transaction.Transaction) {
+	fmt.Printf("Hash: %s\n", t.Hash().StringLE())
+	for i := range t.Inputs {
+		fmt.Printf("Input%02d: [%2d] %s\n", i, t.Inputs[i].PrevIndex, t.Inputs[i].PrevHash.StringLE())
+	}
+	for i := range t.Outputs {
+		fmt.Printf("Output%02d:\n", i)
+		fmt.Printf("\tAssetID   : %s\n", t.Outputs[i].AssetID.StringLE())
+		fmt.Printf("\tAmount    : %s\n", t.Outputs[i].Amount.String())
+		h := t.Outputs[i].ScriptHash
+		fmt.Printf("\tScriptHash: %s\n", t.Outputs[i].ScriptHash.StringLE())
+		fmt.Printf("\tToAddr    : %s\n", address.Uint160ToString(h))
+	}
+}

cli/wallet/wallet.go

@@ -3,8 +3,10 @@ package wallet
 import (
 	"bufio"
 	"context"
+	"encoding/json"
 	"errors"
 	"fmt"
+	"io/ioutil"
 	"os"
 	"strings"
 	"syscall"
@@ -15,6 +17,7 @@ import (
 	"github.com/nspcc-dev/neo-go/pkg/encoding/address"
 	"github.com/nspcc-dev/neo-go/pkg/rpc/client"
 	"github.com/nspcc-dev/neo-go/pkg/rpc/request"
+	context2 "github.com/nspcc-dev/neo-go/pkg/smartcontract/context"
 	"github.com/nspcc-dev/neo-go/pkg/util"
 	"github.com/nspcc-dev/neo-go/pkg/wallet"
 	"github.com/urfave/cli"
@@ -47,6 +50,14 @@ var (
 		Name:  "timeout, t",
 		Usage: "Timeout for the operation",
 	}
+	outFlag = cli.StringFlag{
+		Name:  "out",
+		Usage: "file to put JSON transaction to",
+	}
+	inFlag = cli.StringFlag{
+		Name:  "in",
+		Usage: "file with JSON transaction",
+	}
 )
 
 // NewCommands returns 'wallet' command.
@@ -144,12 +155,13 @@ func NewCommands() []cli.Command {
 				Name:  "transfer",
 				Usage: "transfer NEO/GAS",
 				UsageText: "transfer --path <path> --from <addr> --to <addr>" +
-					" --amount <amount> --asset [NEO|GAS|<hex-id>]",
+					" --amount <amount> --asset [NEO|GAS|<hex-id>] [--out <path>]",
 				Action: transferAsset,
 				Flags: []cli.Flag{
 					walletPathFlag,
 					rpcFlag,
 					timeoutFlag,
+					outFlag,
 					cli.StringFlag{
 						Name:  "from",
 						Usage: "Address to send an asset from",
@@ -168,6 +180,11 @@ func NewCommands() []cli.Command {
 					},
 				},
 			},
+			{
+				Name:        "multisig",
+				Usage:       "work with multisig address",
+				Subcommands: newMultisigCommands(),
+			},
 		},
 	}}
 }
@@ -416,7 +433,6 @@ func transferAsset(ctx *cli.Context) error {
 	}
 
 	tx := transaction.NewContractTX()
-	tx.Data = new(transaction.ContractTX)
 	if err := request.AddInputsAndUnspentsToTx(tx, from, asset, amount, c); err != nil {
 		return cli.NewExitError(err, 1)
 	}
@@ -432,9 +448,23 @@ func transferAsset(ctx *cli.Context) error {
 		Position:   1,
 	})
 
-	_ = acc.SignTx(tx)
-	if err := c.SendRawTransaction(tx); err != nil {
-		return cli.NewExitError(err, 1)
+	if outFile := ctx.String("out"); outFile != "" {
+		priv := acc.PrivateKey()
+		pub := priv.PublicKey()
+		sign := priv.Sign(tx.GetSignedPart())
+		c := context2.NewParameterContext("Neo.Core.ContractTransaction", tx)
+		if err := c.AddSignature(acc.Contract, pub, sign); err != nil {
+			return cli.NewExitError(fmt.Errorf("can't add signature: %v", err), 1)
+		} else if data, err := json.Marshal(c); err != nil {
+			return cli.NewExitError(fmt.Errorf("can't marshal tx to JSON: %v", err), 1)
+		} else if err := ioutil.WriteFile(outFile, data, 0644); err != nil {
+			return cli.NewExitError(fmt.Errorf("can't write tx to file: %v", err), 1)
+		}
+	} else {
+		_ = acc.SignTx(tx)
+		if err := c.SendRawTransaction(tx); err != nil {
+			return cli.NewExitError(err, 1)
+		}
 	}
 
 	fmt.Println(tx.Hash().StringLE())

pkg/core/transaction/output.go

@@ -24,6 +24,13 @@ type Output struct {
 	Position int `json:"n"`
 }
 
+type outputAux struct {
+	AssetID    util.Uint256 `json:"asset"`
+	Amount     util.Fixed8  `json:"value"`
+	ScriptHash string       `json:"address"`
+	Position   int          `json:"n"`
+}
+
 // NewOutput returns a new transaction output.
 func NewOutput(assetID util.Uint256, amount util.Fixed8, scriptHash util.Uint160) *Output {
 	return &Output{
@@ -56,3 +63,20 @@ func (out *Output) MarshalJSON() ([]byte, error) {
 		"n":       out.Position,
 	})
 }
+
+// UnmarshalJSON implements json.Unmarshaler interface.
+func (out *Output) UnmarshalJSON(data []byte) error {
+	var outAux outputAux
+	err := json.Unmarshal(data, &outAux)
+	if err != nil {
+		return err
+	}
+	out.ScriptHash, err = address.StringToUint160(outAux.ScriptHash)
+	if err != nil {
+		return err
+	}
+	out.Amount = outAux.Amount
+	out.AssetID = outAux.AssetID
+	out.Position = outAux.Position
+	return nil
+}

pkg/core/transaction/transaction.go

@@ -158,7 +158,8 @@ func (t *Transaction) EncodeBinary(bw *io.BinWriter) {
 // encodeHashableFields encodes the fields that are not used for
 // signing the transaction, which are all fields except the scripts.
 func (t *Transaction) encodeHashableFields(bw *io.BinWriter) {
-	if t.Data == nil {
+	noData := t.Type == ContractType
+	if t.Data == nil && !noData {
 		bw.Err = errors.New("transaction has no data")
 		return
 	}
@@ -166,7 +167,9 @@ func (t *Transaction) encodeHashableFields(bw *io.BinWriter) {
 	bw.WriteB(byte(t.Version))
 
 	// Underlying TXer.
-	t.Data.EncodeBinary(bw)
+	if !noData {
+		t.Data.EncodeBinary(bw)
+	}
 
 	// Attributes
 	bw.WriteArray(t.Attributes)

pkg/core/transaction/transaction_test.go

@@ -2,6 +2,7 @@ package transaction
 
 import (
 	"encoding/hex"
+	"encoding/json"
 	"testing"
 
 	"github.com/nspcc-dev/neo-go/pkg/encoding/address"
@@ -175,3 +176,23 @@ func TestEncodingTXWithNoData(t *testing.T) {
 	tx.EncodeBinary(buf.BinWriter)
 	require.Error(t, buf.Err)
 }
+
+func TestMarshalUnmarshalJSON(t *testing.T) {
+	tx := NewContractTX()
+	tx.Outputs = []Output{{
+		AssetID:    util.Uint256{1, 2, 3, 4},
+		Amount:     567,
+		ScriptHash: util.Uint160{7, 8, 9, 10},
+		Position:   13,
+	}}
+	tx.Scripts = []Witness{{
+		InvocationScript:   []byte{5, 3, 1},
+		VerificationScript: []byte{2, 4, 6},
+	}}
+	data, err := json.Marshal(tx)
+	require.NoError(t, err)
+
+	txNew := new(Transaction)
+	require.NoError(t, json.Unmarshal(data, txNew))
+	require.Equal(t, tx, txNew)
+}

pkg/core/transaction/witness.go

@@ -28,7 +28,7 @@ func (w *Witness) EncodeBinary(bw *io.BinWriter) {
 }
 
 // MarshalJSON implements the json marshaller interface.
-func (w *Witness) MarshalJSON() ([]byte, error) {
+func (w Witness) MarshalJSON() ([]byte, error) {
 	data := map[string]string{
 		"invocation":   hex.EncodeToString(w.InvocationScript),
 		"verification": hex.EncodeToString(w.VerificationScript),
@@ -37,6 +37,20 @@ func (w *Witness) MarshalJSON() ([]byte, error) {
 	return json.Marshal(data)
 }
 
+// UnmarshalJSON implements json.Unmarshaler interface.
+func (w *Witness) UnmarshalJSON(data []byte) error {
+	m := map[string]string{}
+	err := json.Unmarshal(data, &m)
+	if err != nil {
+		return err
+	}
+	if w.InvocationScript, err = hex.DecodeString(m["invocation"]); err != nil {
+		return err
+	}
+	w.VerificationScript, err = hex.DecodeString(m["verification"])
+	return err
+}
+
 // ScriptHash returns the hash of the VerificationScript.
 func (w Witness) ScriptHash() util.Uint160 {
 	return hash.Hash160(w.VerificationScript)

pkg/smartcontract/context/context.go

@@ -0,0 +1,207 @@
+package context
+
+import (
+	"bytes"
+	"encoding/hex"
+	"encoding/json"
+	"errors"
+	"fmt"
+	"sort"
+	"strings"
+
+	"github.com/nspcc-dev/neo-go/pkg/core/transaction"
+	"github.com/nspcc-dev/neo-go/pkg/crypto/keys"
+	"github.com/nspcc-dev/neo-go/pkg/io"
+	"github.com/nspcc-dev/neo-go/pkg/smartcontract"
+	"github.com/nspcc-dev/neo-go/pkg/util"
+	"github.com/nspcc-dev/neo-go/pkg/vm"
+	"github.com/nspcc-dev/neo-go/pkg/vm/emit"
+	"github.com/nspcc-dev/neo-go/pkg/wallet"
+)
+
+// ParameterContext represents smartcontract parameter's context.
+type ParameterContext struct {
+	// Type is a type of a verifiable item.
+	Type string
+	// Verifiable is an object which can be (de-)serialized.
+	Verifiable io.Serializable
+	// Items is a map from script hashes to context items.
+	Items map[util.Uint160]*Item
+}
+
+type paramContext struct {
+	Type  string                     `json:"type"`
+	Hex   string                     `json:"hex"`
+	Items map[string]json.RawMessage `json:"items"`
+}
+
+type sigWithIndex struct {
+	index int
+	sig   []byte
+}
+
+// NewParameterContext returns ParameterContext with the specified type and item to sign.
+func NewParameterContext(typ string, verif io.Serializable) *ParameterContext {
+	return &ParameterContext{
+		Type:       typ,
+		Verifiable: verif,
+		Items:      make(map[util.Uint160]*Item),
+	}
+}
+
+// GetWitness returns invocation and verification scripts for the specified contract.
+func (c *ParameterContext) GetWitness(ctr *wallet.Contract) (*transaction.Witness, error) {
+	item := c.getItemForContract(ctr)
+	bw := io.NewBufBinWriter()
+	for i := range item.Parameters {
+		if item.Parameters[i].Type != smartcontract.SignatureType {
+			return nil, errors.New("only signature parameters are supported")
+		} else if item.Parameters[i].Value == nil {
+			return nil, errors.New("nil parameter")
+		}
+		emit.Bytes(bw.BinWriter, item.Parameters[i].Value.([]byte))
+	}
+	return &transaction.Witness{
+		InvocationScript:   bw.Bytes(),
+		VerificationScript: ctr.Script,
+	}, nil
+}
+
+// AddSignature adds a signature for the specified contract and public key.
+func (c *ParameterContext) AddSignature(ctr *wallet.Contract, pub *keys.PublicKey, sig []byte) error {
+	item := c.getItemForContract(ctr)
+	if pubs, ok := vm.ParseMultiSigContract(ctr.Script); ok {
+		if item.GetSignature(pub) != nil {
+			return errors.New("signature is already added")
+		}
+		pubBytes := pub.Bytes()
+		var contained bool
+		for i := range pubs {
+			if bytes.Equal(pubBytes, pubs[i]) {
+				contained = true
+				break
+			}
+		}
+		if !contained {
+			return errors.New("public key is not present in script")
+		}
+		item.AddSignature(pub, sig)
+		if len(item.Signatures) == len(ctr.Parameters) {
+			indexMap := map[string]int{}
+			for i := range pubs {
+				indexMap[hex.EncodeToString(pubs[i])] = i
+			}
+			sigs := make([]sigWithIndex, 0, len(item.Signatures))
+			for pub, sig := range item.Signatures {
+				sigs = append(sigs, sigWithIndex{index: indexMap[pub], sig: sig})
+			}
+			sort.Slice(sigs, func(i, j int) bool {
+				return sigs[i].index < sigs[j].index
+			})
+			for i := range sigs {
+				item.Parameters[i] = smartcontract.Parameter{
+					Type:  smartcontract.SignatureType,
+					Value: sigs[i].sig,
+				}
+			}
+		}
+		return nil
+	}
+
+	index := -1
+	for i := range ctr.Parameters {
+		if ctr.Parameters[i].Type == smartcontract.SignatureType {
+			if index >= 0 {
+				return errors.New("multiple signature parameters in non-multisig contract")
+			}
+			index = i
+		}
+	}
+	if index == -1 {
+		return errors.New("missing signature parameter")
+	}
+	item.Parameters[index].Value = sig
+	return nil
+}
+
+func (c *ParameterContext) getItemForContract(ctr *wallet.Contract) *Item {
+	h := ctr.ScriptHash()
+	if item, ok := c.Items[h]; ok {
+		return item
+	}
+	params := make([]smartcontract.Parameter, len(ctr.Parameters))
+	for i := range params {
+		params[i].Type = ctr.Parameters[i].Type
+	}
+	item := &Item{
+		Script:     h,
+		Parameters: params,
+		Signatures: make(map[string][]byte),
+	}
+	c.Items[h] = item
+	return item
+}
+
+// MarshalJSON implements json.Marshaler interface.
+func (c ParameterContext) MarshalJSON() ([]byte, error) {
+	bw := io.NewBufBinWriter()
+	c.Verifiable.EncodeBinary(bw.BinWriter)
+	if bw.Err != nil {
+		return nil, bw.Err
+	}
+	items := make(map[string]json.RawMessage, len(c.Items))
+	for u := range c.Items {
+		data, err := json.Marshal(c.Items[u])
+		if err != nil {
+			return nil, err
+		}
+		items["0x"+u.StringBE()] = data
+	}
+	pc := &paramContext{
+		Type:  c.Type,
+		Hex:   hex.EncodeToString(bw.Bytes()),
+		Items: items,
+	}
+	return json.Marshal(pc)
+}
+
+// UnmarshalJSON implements json.Unmarshaler interface.
+func (c *ParameterContext) UnmarshalJSON(data []byte) error {
+	pc := new(paramContext)
+	if err := json.Unmarshal(data, pc); err != nil {
+		return err
+	}
+	data, err := hex.DecodeString(pc.Hex)
+	if err != nil {
+		return err
+	}
+
+	var verif io.Serializable
+	switch pc.Type {
+	case "Neo.Core.ContractTransaction":
+		verif = new(transaction.Transaction)
+	default:
+		return fmt.Errorf("unsupported type: %s", c.Type)
+	}
+	br := io.NewBinReaderFromBuf(data)
+	verif.DecodeBinary(br)
+	if br.Err != nil {
+		return br.Err
+	}
+	items := make(map[util.Uint160]*Item, len(pc.Items))
+	for h := range pc.Items {
+		u, err := util.Uint160DecodeStringBE(strings.TrimPrefix(h, "0x"))
+		if err != nil {
+			return err
+		}
+		item := new(Item)
+		if err := json.Unmarshal(pc.Items[h], item); err != nil {
+			return err
+		}
+		items[u] = item
+	}
+	c.Type = pc.Type
+	c.Verifiable = verif
+	c.Items = items
+	return nil
+}

pkg/smartcontract/context/context_test.go

@@ -0,0 +1,183 @@
+package context
+
+import (
+	"encoding/hex"
+	"encoding/json"
+	"testing"
+
+	"github.com/nspcc-dev/neo-go/pkg/core/transaction"
+	"github.com/nspcc-dev/neo-go/pkg/crypto/keys"
+	"github.com/nspcc-dev/neo-go/pkg/smartcontract"
+	"github.com/nspcc-dev/neo-go/pkg/util"
+	"github.com/nspcc-dev/neo-go/pkg/vm"
+	"github.com/nspcc-dev/neo-go/pkg/wallet"
+	"github.com/stretchr/testify/require"
+)
+
+func TestParameterContext_AddSignatureSimpleContract(t *testing.T) {
+	tx := getContractTx()
+	priv, err := keys.NewPrivateKey()
+	require.NoError(t, err)
+	pub := priv.PublicKey()
+	sig := priv.Sign(tx.GetSignedPart())
+
+	t.Run("invalid contract", func(t *testing.T) {
+		c := NewParameterContext("Neo.Core.ContractTransaction", tx)
+		ctr := &wallet.Contract{
+			Script: pub.GetVerificationScript(),
+			Parameters: []wallet.ContractParam{
+				newParam(smartcontract.SignatureType, "parameter0"),
+				newParam(smartcontract.SignatureType, "parameter1"),
+			},
+		}
+		require.Error(t, c.AddSignature(ctr, pub, sig))
+		if item := c.Items[ctr.ScriptHash()]; item != nil {
+			require.Nil(t, item.Parameters[0].Value)
+		}
+
+		ctr.Parameters = ctr.Parameters[:0]
+		require.Error(t, c.AddSignature(ctr, pub, sig))
+		if item := c.Items[ctr.ScriptHash()]; item != nil {
+			require.Nil(t, item.Parameters[0].Value)
+		}
+	})
+
+	c := NewParameterContext("Neo.Core.ContractTransaction", tx)
+	ctr := &wallet.Contract{
+		Script:     pub.GetVerificationScript(),
+		Parameters: []wallet.ContractParam{newParam(smartcontract.SignatureType, "parameter0")},
+	}
+	require.NoError(t, c.AddSignature(ctr, pub, sig))
+	item := c.Items[ctr.ScriptHash()]
+	require.NotNil(t, item)
+	require.Equal(t, sig, item.Parameters[0].Value)
+
+	t.Run("GetWitness", func(t *testing.T) {
+		w, err := c.GetWitness(ctr)
+		require.NoError(t, err)
+		v := vm.New()
+		v.SetCheckedHash(tx.VerificationHash().BytesBE())
+		v.LoadScript(w.VerificationScript)
+		v.LoadScript(w.InvocationScript)
+		require.NoError(t, v.Run())
+		require.Equal(t, 1, v.Estack().Len())
+		require.Equal(t, true, v.Estack().Pop().Value())
+	})
+}
+
+func TestParameterContext_AddSignatureMultisig(t *testing.T) {
+	tx := getContractTx()
+	c := NewParameterContext("Neo.Core.ContractTransaction", tx)
+	privs, pubs := getPrivateKeys(t, 4)
+	pubsCopy := make(keys.PublicKeys, len(pubs))
+	copy(pubsCopy, pubs)
+	script, err := smartcontract.CreateMultiSigRedeemScript(3, pubsCopy)
+	require.NoError(t, err)
+
+	ctr := &wallet.Contract{
+		Script: script,
+		Parameters: []wallet.ContractParam{
+			newParam(smartcontract.SignatureType, "parameter0"),
+			newParam(smartcontract.SignatureType, "parameter1"),
+			newParam(smartcontract.SignatureType, "parameter2"),
+		},
+	}
+	data := tx.GetSignedPart()
+	priv, err := keys.NewPrivateKey()
+	require.NoError(t, err)
+	sig := priv.Sign(data)
+	require.Error(t, c.AddSignature(ctr, priv.PublicKey(), sig))
+
+	indices := []int{2, 3, 0} // random order
+	for _, i := range indices {
+		sig := privs[i].Sign(data)
+		require.NoError(t, c.AddSignature(ctr, pubs[i], sig))
+		require.Error(t, c.AddSignature(ctr, pubs[i], sig))
+
+		item := c.Items[ctr.ScriptHash()]
+		require.NotNil(t, item)
+		require.Equal(t, sig, item.GetSignature(pubs[i]))
+	}
+
+	t.Run("GetWitness", func(t *testing.T) {
+		w, err := c.GetWitness(ctr)
+		require.NoError(t, err)
+		v := vm.New()
+		v.SetCheckedHash(tx.VerificationHash().BytesBE())
+		v.LoadScript(w.VerificationScript)
+		v.LoadScript(w.InvocationScript)
+		require.NoError(t, v.Run())
+		require.Equal(t, 1, v.Estack().Len())
+		require.Equal(t, true, v.Estack().Pop().Value())
+	})
+}
+
+func TestParameterContext_MarshalJSON(t *testing.T) {
+	priv, err := keys.NewPrivateKey()
+	require.NoError(t, err)
+
+	tx := getContractTx()
+	data := tx.GetSignedPart()
+	sign := priv.Sign(data)
+
+	expected := &ParameterContext{
+		Type:       "Neo.Core.ContractTransaction",
+		Verifiable: tx,
+		Items: map[util.Uint160]*Item{
+			priv.GetScriptHash(): {
+				Script: priv.GetScriptHash(),
+				Parameters: []smartcontract.Parameter{{
+					Type:  smartcontract.SignatureType,
+					Value: sign,
+				}},
+				Signatures: map[string][]byte{
+					hex.EncodeToString(priv.PublicKey().Bytes()): sign,
+				},
+			},
+		},
+	}
+
+	data, err = json.Marshal(expected)
+	require.NoError(t, err)
+
+	actual := new(ParameterContext)
+	require.NoError(t, json.Unmarshal(data, actual))
+	require.Equal(t, expected, actual)
+}
+
+func getPrivateKeys(t *testing.T, n int) ([]*keys.PrivateKey, []*keys.PublicKey) {
+	privs := make([]*keys.PrivateKey, n)
+	pubs := make([]*keys.PublicKey, n)
+	for i := range privs {
+		var err error
+		privs[i], err = keys.NewPrivateKey()
+		require.NoError(t, err)
+		pubs[i] = privs[i].PublicKey()
+	}
+	return privs, pubs
+}
+
+func newParam(typ smartcontract.ParamType, name string) wallet.ContractParam {
+	return wallet.ContractParam{
+		Name: name,
+		Type: typ,
+	}
+}
+
+func getContractTx() *transaction.Transaction {
+	tx := transaction.NewContractTX()
+	tx.AddInput(&transaction.Input{
+		PrevHash:  util.Uint256{1, 2, 3, 4},
+		PrevIndex: 5,
+	})
+	tx.AddOutput(&transaction.Output{
+		AssetID:    util.Uint256{7, 8, 9},
+		Amount:     10,
+		ScriptHash: util.Uint160{11, 12},
+	})
+	tx.Data = new(transaction.ContractTX)
+	tx.Attributes = make([]transaction.Attribute, 0)
+	tx.Scripts = make([]transaction.Witness, 0)
+	tx.Hash()
+	return tx
+}

pkg/smartcontract/context/item.go

@@ -0,0 +1,75 @@
+package context
+
+import (
+	"encoding/hex"
+	"encoding/json"
+
+	"github.com/nspcc-dev/neo-go/pkg/crypto/keys"
+	"github.com/nspcc-dev/neo-go/pkg/smartcontract"
+	"github.com/nspcc-dev/neo-go/pkg/util"
+)
+
+// Item represents a transaction context item.
+type Item struct {
+	Script     util.Uint160
+	Parameters []smartcontract.Parameter
+	Signatures map[string][]byte
+}
+
+type itemAux struct {
+	Script     util.Uint160              `json:"script"`
+	Parameters []smartcontract.Parameter `json:"parameters"`
+	Signatures map[string]string         `json:"signatures"`
+}
+
+// GetSignature returns signature for pub if present.
+func (it *Item) GetSignature(pub *keys.PublicKey) []byte {
+	return it.Signatures[hex.EncodeToString(pub.Bytes())]
+}
+
+// AddSignature adds a signature for pub.
+func (it *Item) AddSignature(pub *keys.PublicKey, sig []byte) {
+	pubHex := hex.EncodeToString(pub.Bytes())
+	it.Signatures[pubHex] = sig
+}
+
+// MarshalJSON implements json.Marshaler interface.
+func (it Item) MarshalJSON() ([]byte, error) {
+	ci := itemAux{
+		Script:     it.Script,
+		Parameters: it.Parameters,
+		Signatures: make(map[string]string, len(it.Signatures)),
+	}
+
+	for key, sig := range it.Signatures {
+		ci.Signatures[key] = hex.EncodeToString(sig)
+	}
+
+	return json.Marshal(ci)
+}
+
+// UnmarshalJSON implements json.Unmarshaler interface.
+func (it *Item) UnmarshalJSON(data []byte) error {
+	ci := new(itemAux)
+	if err := json.Unmarshal(data, ci); err != nil {
+		return err
+	}
+
+	sigs := make(map[string][]byte, len(ci.Signatures))
+	for keyHex, sigHex := range ci.Signatures {
+		_, err := keys.NewPublicKeyFromString(keyHex)
+		if err != nil {
+			return err
+		}
+		sig, err := hex.DecodeString(sigHex)
+		if err != nil {
+			return err
+		}
+		sigs[keyHex] = sig
+	}
+
+	it.Signatures = sigs
+	it.Script = ci.Script
+	it.Parameters = ci.Parameters
+	return nil
+}

pkg/smartcontract/context/item_test.go

@@ -0,0 +1,74 @@
+package context
+
+import (
+	"encoding/hex"
+	"encoding/json"
+	"io"
+	"math/rand"
+	"testing"
+	"time"
+
+	"github.com/nspcc-dev/neo-go/pkg/smartcontract"
+
+	"github.com/nspcc-dev/neo-go/pkg/crypto/keys"
+	"github.com/nspcc-dev/neo-go/pkg/util"
+	"github.com/stretchr/testify/assert"
+	"github.com/stretchr/testify/require"
+)
+
+func TestContextItem_AddSignature(t *testing.T) {
+	item := &Item{Signatures: make(map[string][]byte)}
+
+	priv1, err := keys.NewPrivateKey()
+	require.NoError(t, err)
+
+	pub1 := priv1.PublicKey()
+	sig1 := []byte{1, 2, 3}
+	item.AddSignature(pub1, sig1)
+	require.Equal(t, sig1, item.GetSignature(pub1))
+
+	priv2, err := keys.NewPrivateKey()
+	require.NoError(t, err)
+
+	pub2 := priv2.PublicKey()
+	sig2 := []byte{5, 6, 7}
+	item.AddSignature(pub2, sig2)
+	require.Equal(t, sig2, item.GetSignature(pub2))
+	require.Equal(t, sig1, item.GetSignature(pub1))
+}
+
+func TestContextItem_MarshalJSON(t *testing.T) {
+	priv1, err := keys.NewPrivateKey()
+	require.NoError(t, err)
+
+	priv2, err := keys.NewPrivateKey()
+	require.NoError(t, err)
+
+	expected := &Item{
+		Script: util.Uint160{1, 2, 3},
+		Parameters: []smartcontract.Parameter{{
+			Type:  smartcontract.SignatureType,
+			Value: getRandomSlice(t, 64),
+		}},
+		Signatures: map[string][]byte{
+			hex.EncodeToString(priv1.PublicKey().Bytes()): getRandomSlice(t, 64),
+			hex.EncodeToString(priv2.PublicKey().Bytes()): getRandomSlice(t, 64),
+		},
+	}
+
+	data, err := json.Marshal(expected)
+	require.NoError(t, err)
+
+	actual := new(Item)
+	require.NoError(t, json.Unmarshal(data, actual))
+	assert.Equal(t, expected, actual)
+}
+
+func getRandomSlice(t *testing.T, n int) []byte {
+	src := rand.NewSource(time.Now().UnixNano())
+	r := rand.New(src)
+	data := make([]byte, n)
+	_, err := io.ReadFull(r, data)
+	require.NoError(t, err)
+	return data
+}

pkg/smartcontract/parameter.go

@@ -137,7 +137,7 @@ func (p *Parameter) UnmarshalJSON(data []byte) (err error) {
 			return
 		}
 		p.Value = boolean
-	case ByteArrayType, PublicKeyType:
+	case ByteArrayType, PublicKeyType, SignatureType:
 		if err = json.Unmarshal(r.Value, &s); err != nil {
 			return
 		}

pkg/vm/contract_checks.go

@@ -31,49 +31,58 @@ func getNumOfThingsFromInstr(instr opcode.Opcode, param []byte) (int, bool) {
 // IsMultiSigContract checks whether the passed script is a multi-signature
 // contract.
 func IsMultiSigContract(script []byte) bool {
+	_, ok := ParseMultiSigContract(script)
+	return ok
+}
+
+// ParseMultiSigContract returns list of public keys from the verification
+// script of the contract.
+func ParseMultiSigContract(script []byte) ([][]byte, bool) {
 	var nsigs, nkeys int
 
 	ctx := NewContext(script)
 	instr, param, err := ctx.Next()
 	if err != nil {
-		return false
+		return nil, false
 	}
 	nsigs, ok := getNumOfThingsFromInstr(instr, param)
 	if !ok {
-		return false
+		return nil, false
 	}
+	var pubs [][]byte
 	for {
 		instr, param, err = ctx.Next()
 		if err != nil {
-			return false
+			return nil, false
 		}
 		if instr != opcode.PUSHBYTES33 {
 			break
 		}
+		pubs = append(pubs, param)
 		nkeys++
 		if nkeys > MaxArraySize {
-			return false
+			return nil, false
 		}
 	}
 	if nkeys < nsigs {
-		return false
+		return nil, false
 	}
 	nkeys2, ok := getNumOfThingsFromInstr(instr, param)
 	if !ok {
-		return false
+		return nil, false
 	}
 	if nkeys2 != nkeys {
-		return false
+		return nil, false
 	}
 	instr, _, err = ctx.Next()
 	if err != nil || instr != opcode.CHECKMULTISIG {
-		return false
+		return nil, false
 	}
 	instr, _, err = ctx.Next()
 	if err != nil || instr != opcode.RET || ctx.ip != len(script) {
-		return false
+		return nil, false
 	}
-	return true
+	return pubs, true
 }
 
 // IsSignatureContract checks whether the passed script is a signature check

pkg/wallet/account.go

@@ -56,7 +56,7 @@ type Contract struct {
 	Script []byte `json:"script"`
 
 	// A list of parameters used deploying this contract.
-	Parameters []contractParam `json:"parameters"`
+	Parameters []ContractParam `json:"parameters"`
 
 	// Indicates whether the contract has been deployed to the blockchain.
 	Deployed bool `json:"deployed"`
@@ -68,13 +68,15 @@ type contract struct {
 	Script string `json:"script"`
 
 	// A list of parameters used deploying this contract.
-	Parameters []contractParam `json:"parameters"`
+	Parameters []ContractParam `json:"parameters"`
 
 	// Indicates whether the contract has been deployed to the blockchain.
 	Deployed bool `json:"deployed"`
 }
 
-type contractParam struct {
+// ContractParam is a descriptor of a contract parameter
+// containing type and optional name.
+type ContractParam struct {
 	Name string                  `json:"name"`
 	Type smartcontract.ParamType `json:"type"`
 }
@@ -252,8 +254,8 @@ func newAccountFromPrivateKey(p *keys.PrivateKey) *Account {
 	return a
 }
 
-func getContractParams(n int) []contractParam {
-	params := make([]contractParam, n)
+func getContractParams(n int) []ContractParam {
+	params := make([]ContractParam, n)
 	for i := range params {
 		params[i].Name = fmt.Sprintf("parameter%d", i)
 		params[i].Type = smartcontract.SignatureType