wallet: support creating multisig accounts

(*Account).ConvertMultisig() will convert an existing account
into a multisig one.

pkg/wallet/account.go

@@ -1,6 +1,7 @@
 package wallet
 
 import (
+	"bytes"
 	"encoding/hex"
 	"encoding/json"
 	"errors"
@@ -8,6 +9,7 @@ import (
 
 	"github.com/CityOfZion/neo-go/pkg/crypto/hash"
 	"github.com/CityOfZion/neo-go/pkg/crypto/keys"
+	"github.com/CityOfZion/neo-go/pkg/encoding/address"
 	"github.com/CityOfZion/neo-go/pkg/smartcontract"
 	"github.com/CityOfZion/neo-go/pkg/util"
 )
@@ -177,6 +179,34 @@ func NewAccountFromEncryptedWIF(wif string, pass string) (*Account, error) {
 	return a, nil
 }
 
+// ConvertMultisig sets a's contract to multisig contract with m sufficient signatures.
+func (a *Account) ConvertMultisig(m int, pubs []*keys.PublicKey) error {
+	var found bool
+	for i := range pubs {
+		if bytes.Equal(a.publicKey, pubs[i].Bytes()) {
+			found = true
+			break
+		}
+	}
+
+	if !found {
+		return errors.New("own public key was not found among multisig keys")
+	}
+
+	script, err := smartcontract.CreateMultiSigRedeemScript(m, pubs)
+	if err != nil {
+		return err
+	}
+
+	a.Address = address.Uint160ToString(hash.Hash160(script))
+	a.Contract = &Contract{
+		Script:     script,
+		Parameters: getContractParams(m),
+	}
+
+	return nil
+}
+
 // newAccountFromPrivateKey creates a wallet from the given PrivateKey.
 func newAccountFromPrivateKey(p *keys.PrivateKey) *Account {
 	pubKey := p.PublicKey()

pkg/wallet/account_test.go

@@ -6,6 +6,7 @@ import (
 	"testing"
 
 	"github.com/CityOfZion/neo-go/pkg/crypto/hash"
+	"github.com/CityOfZion/neo-go/pkg/crypto/keys"
 	"github.com/CityOfZion/neo-go/pkg/internal/keytestcases"
 	"github.com/stretchr/testify/assert"
 	"github.com/stretchr/testify/require"
@@ -87,6 +88,51 @@ func TestContract_ScriptHash(t *testing.T) {
 	require.Equal(t, hash.Hash160(script), c.ScriptHash())
 }
 
+func TestAccount_ConvertMultisig(t *testing.T) {
+	// test is based on a wallet1_solo.json accounts from neo-local
+	a, err := NewAccountFromEncryptedWIF("6PYLmjBYJ4wQTCEfqvnznGJwZeW9pfUcV5m5oreHxqryUgqKpTRAFt9L8Y", "one")
+	require.NoError(t, err)
+
+	hexs := []string{
+		"02b3622bf4017bdfe317c58aed5f4c753f206b7db896046fa7d774bbc4bf7f8dc2", // <- this is our key
+		"02103a7f7dd016558597f7960d27c516a4394fd968b9e65155eb4b013e4040406e",
+		"02a7bc55fe8684e0119768d104ba30795bdcc86619e864add26156723ed185cd62",
+		"03d90c07df63e690ce77912e10ab51acc944b66860237b608c4f8f8309e71ee699",
+	}
+
+	t.Run("invalid number of signatures", func(t *testing.T) {
+		pubs := convertPubs(t, hexs)
+		require.Error(t, a.ConvertMultisig(0, pubs))
+	})
+
+	t.Run("account key is missing from multisig", func(t *testing.T) {
+		pubs := convertPubs(t, hexs[1:])
+		require.Error(t, a.ConvertMultisig(1, pubs))
+	})
+
+	t.Run("1/1 multisig", func(t *testing.T) {
+		pubs := convertPubs(t, hexs[:1])
+		require.NoError(t, a.ConvertMultisig(1, pubs))
+		require.Equal(t, "AbU69m8WUZJSWanfr1Cy66cpEcsmMcX7BR", a.Address)
+	})
+
+	t.Run("3/4 multisig", func(t *testing.T) {
+		pubs := convertPubs(t, hexs)
+		require.NoError(t, a.ConvertMultisig(3, pubs))
+		require.Equal(t, "AZ81H31DMWzbSnFDLFkzh9vHwaDLayV7fU", a.Address)
+	})
+}
+
+func convertPubs(t *testing.T, hexKeys []string) []*keys.PublicKey {
+	pubs := make([]*keys.PublicKey, len(hexKeys))
+	for i := range pubs {
+		var err error
+		pubs[i], err = keys.NewPublicKeyFromString(hexKeys[i])
+		require.NoError(t, err)
+	}
+	return pubs
+}
+
 func compareFields(t *testing.T, tk keytestcases.Ktype, acc *Account) {
 	if want, have := tk.Address, acc.Address; want != have {
 		t.Fatalf("expected %s got %s", want, have)