Merge pull request #1658 from nspcc-dev/signature_collection/module

core, network: add Notary module

internal/fakechain/fakechain.go

@@ -0,0 +1,438 @@
+package fakechain
+
+import (
+	"errors"
+	"math/big"
+	"sync/atomic"
+
+	"github.com/nspcc-dev/neo-go/pkg/config"
+	"github.com/nspcc-dev/neo-go/pkg/core/block"
+	"github.com/nspcc-dev/neo-go/pkg/core/blockchainer"
+	"github.com/nspcc-dev/neo-go/pkg/core/blockchainer/services"
+	"github.com/nspcc-dev/neo-go/pkg/core/interop"
+	"github.com/nspcc-dev/neo-go/pkg/core/mempool"
+	"github.com/nspcc-dev/neo-go/pkg/core/native"
+	"github.com/nspcc-dev/neo-go/pkg/core/state"
+	"github.com/nspcc-dev/neo-go/pkg/core/transaction"
+	"github.com/nspcc-dev/neo-go/pkg/crypto"
+	"github.com/nspcc-dev/neo-go/pkg/crypto/keys"
+	"github.com/nspcc-dev/neo-go/pkg/smartcontract/trigger"
+	"github.com/nspcc-dev/neo-go/pkg/util"
+	"github.com/nspcc-dev/neo-go/pkg/vm"
+)
+
+// FakeChain implements Blockchainer interface, but does not provide real functionality.
+type FakeChain struct {
+	config.ProtocolConfiguration
+	*mempool.Pool
+	blocksCh                 []chan<- *block.Block
+	Blockheight              uint32
+	PoolTxF                  func(*transaction.Transaction) error
+	poolTxWithData           func(*transaction.Transaction, interface{}, *mempool.Pool) error
+	blocks                   map[util.Uint256]*block.Block
+	hdrHashes                map[uint32]util.Uint256
+	txs                      map[util.Uint256]*transaction.Transaction
+	VerifyWitnessF           func() error
+	MaxVerificationGAS       int64
+	NotaryContractScriptHash util.Uint160
+	NotaryDepositExpiration  uint32
+	PostBlock                []func(blockchainer.Blockchainer, *mempool.Pool, *block.Block)
+	UtilityTokenBalance      *big.Int
+}
+
+// NewFakeChain returns new FakeChain structure.
+func NewFakeChain() *FakeChain {
+	return &FakeChain{
+		Pool:                  mempool.New(10, 0, false),
+		PoolTxF:               func(*transaction.Transaction) error { return nil },
+		poolTxWithData:        func(*transaction.Transaction, interface{}, *mempool.Pool) error { return nil },
+		blocks:                make(map[util.Uint256]*block.Block),
+		hdrHashes:             make(map[uint32]util.Uint256),
+		txs:                   make(map[util.Uint256]*transaction.Transaction),
+		ProtocolConfiguration: config.ProtocolConfiguration{P2PNotaryRequestPayloadPoolSize: 10},
+	}
+}
+
+// PutBlock implements Blockchainer interface.
+func (chain *FakeChain) PutBlock(b *block.Block) {
+	chain.blocks[b.Hash()] = b
+	chain.hdrHashes[b.Index] = b.Hash()
+	atomic.StoreUint32(&chain.Blockheight, b.Index)
+}
+
+// PutHeader implements Blockchainer interface.
+func (chain *FakeChain) PutHeader(b *block.Block) {
+	chain.hdrHashes[b.Index] = b.Hash()
+}
+
+// PutTx implements Blockchainer interface.
+func (chain *FakeChain) PutTx(tx *transaction.Transaction) {
+	chain.txs[tx.Hash()] = tx
+}
+
+// ApplyPolicyToTxSet implements Blockchainer interface.
+func (chain *FakeChain) ApplyPolicyToTxSet([]*transaction.Transaction) []*transaction.Transaction {
+	panic("TODO")
+}
+
+// IsTxStillRelevant implements Blockchainer interface.
+func (chain *FakeChain) IsTxStillRelevant(t *transaction.Transaction, txpool *mempool.Pool, isPartialTx bool) bool {
+	panic("TODO")
+}
+
+// IsExtensibleAllowed implements Blockchainer interface.
+func (*FakeChain) IsExtensibleAllowed(uint160 util.Uint160) bool {
+	return true
+}
+
+// GetNotaryDepositExpiration implements Blockchainer interface.
+func (chain *FakeChain) GetNotaryDepositExpiration(acc util.Uint160) uint32 {
+	if chain.NotaryDepositExpiration != 0 {
+		return chain.NotaryDepositExpiration
+	}
+	panic("TODO")
+}
+
+// GetNotaryContractScriptHash implements Blockchainer interface.
+func (chain *FakeChain) GetNotaryContractScriptHash() util.Uint160 {
+	if !chain.NotaryContractScriptHash.Equals(util.Uint160{}) {
+		return chain.NotaryContractScriptHash
+	}
+	panic("TODO")
+}
+
+// GetNotaryBalance implements Blockchainer interface.
+func (chain *FakeChain) GetNotaryBalance(acc util.Uint160) *big.Int {
+	panic("TODO")
+}
+
+// GetPolicer implements Blockchainer interface.
+func (chain *FakeChain) GetPolicer() blockchainer.Policer {
+	return chain
+}
+
+// GetBaseExecFee implements Policer interface.
+func (chain *FakeChain) GetBaseExecFee() int64 {
+	return interop.DefaultBaseExecFee
+}
+
+// GetStoragePrice implements Policer interface.
+func (chain *FakeChain) GetStoragePrice() int64 {
+	return native.StoragePrice
+}
+
+// GetMaxVerificationGAS implements Policer interface.
+func (chain *FakeChain) GetMaxVerificationGAS() int64 {
+	if chain.MaxVerificationGAS != 0 {
+		return chain.MaxVerificationGAS
+	}
+	panic("TODO")
+}
+
+// PoolTxWithData implements Blockchainer interface.
+func (chain *FakeChain) PoolTxWithData(t *transaction.Transaction, data interface{}, mp *mempool.Pool, feer mempool.Feer, verificationFunction func(bc blockchainer.Blockchainer, t *transaction.Transaction, data interface{}) error) error {
+	return chain.poolTxWithData(t, data, mp)
+}
+
+// RegisterPostBlock implements Blockchainer interface.
+func (chain *FakeChain) RegisterPostBlock(f func(blockchainer.Blockchainer, *mempool.Pool, *block.Block)) {
+	chain.PostBlock = append(chain.PostBlock, f)
+}
+
+// GetConfig implements Blockchainer interface.
+func (chain *FakeChain) GetConfig() config.ProtocolConfiguration {
+	return chain.ProtocolConfiguration
+}
+
+// CalculateClaimable implements Blockchainer interface.
+func (chain *FakeChain) CalculateClaimable(util.Uint160, uint32) (*big.Int, error) {
+	panic("TODO")
+}
+
+// FeePerByte implements Feer interface.
+func (chain *FakeChain) FeePerByte() int64 {
+	panic("TODO")
+}
+
+// P2PSigExtensionsEnabled implements Feer interface.
+func (chain *FakeChain) P2PSigExtensionsEnabled() bool {
+	return true
+}
+
+// GetMaxBlockSystemFee implements Policer interface.
+func (chain *FakeChain) GetMaxBlockSystemFee() int64 {
+	panic("TODO")
+}
+
+// GetMaxBlockSize implements Policer interface.
+func (chain *FakeChain) GetMaxBlockSize() uint32 {
+	panic("TODO")
+}
+
+// AddHeaders implements Blockchainer interface.
+func (chain *FakeChain) AddHeaders(...*block.Header) error {
+	panic("TODO")
+}
+
+// AddBlock implements Blockchainer interface.
+func (chain *FakeChain) AddBlock(block *block.Block) error {
+	if block.Index == atomic.LoadUint32(&chain.Blockheight)+1 {
+		chain.PutBlock(block)
+	}
+	return nil
+}
+
+// AddStateRoot implements Blockchainer interface.
+func (chain *FakeChain) AddStateRoot(r *state.MPTRoot) error {
+	panic("TODO")
+}
+
+// BlockHeight implements Feer interface.
+func (chain *FakeChain) BlockHeight() uint32 {
+	return atomic.LoadUint32(&chain.Blockheight)
+}
+
+// Close implements Blockchainer interface.
+func (chain *FakeChain) Close() {
+	panic("TODO")
+}
+
+// HeaderHeight implements Blockchainer interface.
+func (chain *FakeChain) HeaderHeight() uint32 {
+	return atomic.LoadUint32(&chain.Blockheight)
+}
+
+// GetAppExecResults implements Blockchainer interface.
+func (chain *FakeChain) GetAppExecResults(hash util.Uint256, trig trigger.Type) ([]state.AppExecResult, error) {
+	panic("TODO")
+}
+
+// GetBlock implements Blockchainer interface.
+func (chain *FakeChain) GetBlock(hash util.Uint256) (*block.Block, error) {
+	if b, ok := chain.blocks[hash]; ok {
+		return b, nil
+	}
+	return nil, errors.New("not found")
+}
+
+// GetCommittee implements Blockchainer interface.
+func (chain *FakeChain) GetCommittee() (keys.PublicKeys, error) {
+	panic("TODO")
+}
+
+// GetContractState implements Blockchainer interface.
+func (chain *FakeChain) GetContractState(hash util.Uint160) *state.Contract {
+	panic("TODO")
+}
+
+// GetContractScriptHash implements Blockchainer interface.
+func (chain *FakeChain) GetContractScriptHash(id int32) (util.Uint160, error) {
+	panic("TODO")
+}
+
+// GetNativeContractScriptHash implements Blockchainer interface.
+func (chain *FakeChain) GetNativeContractScriptHash(name string) (util.Uint160, error) {
+	panic("TODO")
+}
+
+// GetHeaderHash implements Blockchainer interface.
+func (chain *FakeChain) GetHeaderHash(n int) util.Uint256 {
+	return chain.hdrHashes[uint32(n)]
+}
+
+// GetHeader implements Blockchainer interface.
+func (chain *FakeChain) GetHeader(hash util.Uint256) (*block.Header, error) {
+	b, err := chain.GetBlock(hash)
+	if err != nil {
+		return nil, err
+	}
+	return b.Header(), nil
+}
+
+// GetNextBlockValidators implements Blockchainer interface.
+func (chain *FakeChain) GetNextBlockValidators() ([]*keys.PublicKey, error) {
+	panic("TODO")
+}
+
+// ForEachNEP17Transfer implements Blockchainer interface.
+func (chain *FakeChain) ForEachNEP17Transfer(util.Uint160, func(*state.NEP17Transfer) (bool, error)) error {
+	panic("TODO")
+}
+
+// GetNEP17Balances implements Blockchainer interface.
+func (chain *FakeChain) GetNEP17Balances(util.Uint160) *state.NEP17Balances {
+	panic("TODO")
+}
+
+// GetValidators implements Blockchainer interface.
+func (chain *FakeChain) GetValidators() ([]*keys.PublicKey, error) {
+	panic("TODO")
+}
+
+// GetStandByCommittee implements Blockchainer interface.
+func (chain *FakeChain) GetStandByCommittee() keys.PublicKeys {
+	panic("TODO")
+}
+
+// GetStandByValidators implements Blockchainer interface.
+func (chain *FakeChain) GetStandByValidators() keys.PublicKeys {
+	panic("TODO")
+}
+
+// GetEnrollments implements Blockchainer interface.
+func (chain *FakeChain) GetEnrollments() ([]state.Validator, error) {
+	panic("TODO")
+}
+
+// GetStateProof implements Blockchainer interface.
+func (chain *FakeChain) GetStateProof(util.Uint256, []byte) ([][]byte, error) {
+	panic("TODO")
+}
+
+// GetStateRoot implements Blockchainer interface.
+func (chain *FakeChain) GetStateRoot(height uint32) (*state.MPTRootState, error) {
+	panic("TODO")
+}
+
+// GetStorageItem implements Blockchainer interface.
+func (chain *FakeChain) GetStorageItem(id int32, key []byte) *state.StorageItem {
+	panic("TODO")
+}
+
+// GetTestVM implements Blockchainer interface.
+func (chain *FakeChain) GetTestVM(t trigger.Type, tx *transaction.Transaction, b *block.Block) *vm.VM {
+	panic("TODO")
+}
+
+// GetStorageItems implements Blockchainer interface.
+func (chain *FakeChain) GetStorageItems(id int32) (map[string]*state.StorageItem, error) {
+	panic("TODO")
+}
+
+// CurrentHeaderHash implements Blockchainer interface.
+func (chain *FakeChain) CurrentHeaderHash() util.Uint256 {
+	return util.Uint256{}
+}
+
+// CurrentBlockHash implements Blockchainer interface.
+func (chain *FakeChain) CurrentBlockHash() util.Uint256 {
+	return util.Uint256{}
+}
+
+// HasBlock implements Blockchainer interface.
+func (chain *FakeChain) HasBlock(h util.Uint256) bool {
+	_, ok := chain.blocks[h]
+	return ok
+}
+
+// HasTransaction implements Blockchainer interface.
+func (chain *FakeChain) HasTransaction(h util.Uint256) bool {
+	_, ok := chain.txs[h]
+	return ok
+}
+
+// GetTransaction implements Blockchainer interface.
+func (chain *FakeChain) GetTransaction(h util.Uint256) (*transaction.Transaction, uint32, error) {
+	if tx, ok := chain.txs[h]; ok {
+		return tx, 1, nil
+	}
+	return nil, 0, errors.New("not found")
+}
+
+// GetMemPool implements Blockchainer interface.
+func (chain *FakeChain) GetMemPool() *mempool.Pool {
+	return chain.Pool
+}
+
+// GetGoverningTokenBalance implements Blockchainer interface.
+func (chain *FakeChain) GetGoverningTokenBalance(acc util.Uint160) (*big.Int, uint32) {
+	panic("TODO")
+}
+
+// GetUtilityTokenBalance implements Feer interface.
+func (chain *FakeChain) GetUtilityTokenBalance(uint160 util.Uint160) *big.Int {
+	if chain.UtilityTokenBalance != nil {
+		return chain.UtilityTokenBalance
+	}
+	panic("TODO")
+}
+
+// ManagementContractHash implements Blockchainer interface.
+func (chain FakeChain) ManagementContractHash() util.Uint160 {
+	panic("TODO")
+}
+
+// PoolTx implements Blockchainer interface.
+func (chain *FakeChain) PoolTx(tx *transaction.Transaction, _ ...*mempool.Pool) error {
+	return chain.PoolTxF(tx)
+}
+
+// SetOracle implements Blockchainer interface.
+func (chain FakeChain) SetOracle(services.Oracle) {
+	panic("TODO")
+}
+
+// SetNotary implements Blockchainer interface.
+func (chain *FakeChain) SetNotary(notary services.Notary) {
+	panic("TODO")
+}
+
+// SubscribeForBlocks implements Blockchainer interface.
+func (chain *FakeChain) SubscribeForBlocks(ch chan<- *block.Block) {
+	chain.blocksCh = append(chain.blocksCh, ch)
+}
+
+// SubscribeForExecutions implements Blockchainer interface.
+func (chain *FakeChain) SubscribeForExecutions(ch chan<- *state.AppExecResult) {
+	panic("TODO")
+}
+
+// SubscribeForNotifications implements Blockchainer interface.
+func (chain *FakeChain) SubscribeForNotifications(ch chan<- *state.NotificationEvent) {
+	panic("TODO")
+}
+
+// SubscribeForTransactions implements Blockchainer interface.
+func (chain *FakeChain) SubscribeForTransactions(ch chan<- *transaction.Transaction) {
+	panic("TODO")
+}
+
+// VerifyTx implements Blockchainer interface.
+func (chain *FakeChain) VerifyTx(*transaction.Transaction) error {
+	panic("TODO")
+}
+
+// VerifyWitness implements Blockchainer interface.
+func (chain *FakeChain) VerifyWitness(util.Uint160, crypto.Verifiable, *transaction.Witness, int64) error {
+	if chain.VerifyWitnessF != nil {
+		return chain.VerifyWitnessF()
+	}
+	panic("TODO")
+}
+
+// UnsubscribeFromBlocks implements Blockchainer interface.
+func (chain *FakeChain) UnsubscribeFromBlocks(ch chan<- *block.Block) {
+	for i, c := range chain.blocksCh {
+		if c == ch {
+			if i < len(chain.blocksCh) {
+				copy(chain.blocksCh[i:], chain.blocksCh[i+1:])
+			}
+			chain.blocksCh = chain.blocksCh[:len(chain.blocksCh)]
+		}
+	}
+}
+
+// UnsubscribeFromExecutions implements Blockchainer interface.
+func (chain *FakeChain) UnsubscribeFromExecutions(ch chan<- *state.AppExecResult) {
+	panic("TODO")
+}
+
+// UnsubscribeFromNotifications implements Blockchainer interface.
+func (chain *FakeChain) UnsubscribeFromNotifications(ch chan<- *state.NotificationEvent) {
+	panic("TODO")
+}
+
+// UnsubscribeFromTransactions implements Blockchainer interface.
+func (chain *FakeChain) UnsubscribeFromTransactions(ch chan<- *transaction.Transaction) {
+	panic("TODO")
+}

pkg/config/notary_config.go

@@ -0,0 +1,7 @@
+package config
+
+// P2PNotary stores configuration for Notary node service.
+type P2PNotary struct {
+	Enabled      bool   `yaml:"Enabled"`
+	UnlockWallet Wallet `yaml:"UnlockWallet"`
+}

pkg/config/protocol_config.go

@@ -20,6 +20,8 @@ type (
 		RemoveUntraceableBlocks bool `yaml:"RemoveUntraceableBlocks"`
 		// MaxTraceableBlocks is the length of the chain accessible to smart contracts.
 		MaxTraceableBlocks uint32 `yaml:"MaxTraceableBlocks"`
+		// P2PNotary stores configuration for P2P notary node service
+		P2PNotary P2PNotary `yaml:"P2PNotary"`
 		// P2PSigExtensions enables additional signature-related logic.
 		P2PSigExtensions bool `yaml:"P2PSigExtensions"`
 		// ReservedAttributes allows to have reserved attributes range for experimental or private purposes.

pkg/consensus/consensus.go

@@ -451,7 +451,7 @@ func (s *service) verifyBlock(b block.Block) bool {
 	}
 
 	var fee int64
-	var pool = mempool.New(len(coreb.Transactions), 0)
+	var pool = mempool.New(len(coreb.Transactions), 0, false)
 	var mainPool = s.Chain.GetMemPool()
 	for _, tx := range coreb.Transactions {
 		var err error

pkg/core/blockchain.go

@@ -177,7 +177,7 @@ func NewBlockchain(s storage.Store, cfg config.ProtocolConfiguration, log *zap.L
 		dao:         dao.NewSimple(s, cfg.Magic, cfg.StateRootInHeader),
 		stopCh:      make(chan struct{}),
 		runToExitCh: make(chan struct{}),
-		memPool:     mempool.New(cfg.MemPoolSize, 0),
+		memPool:     mempool.New(cfg.MemPoolSize, 0, false),
 		sbCommittee: committee,
 		log:         log,
 		events:      make(chan bcEvent),
@@ -201,6 +201,12 @@ func (bc *Blockchain) SetOracle(mod services.Oracle) {
 	bc.contracts.Designate.OracleService.Store(mod)
 }
 
+// SetNotary sets notary module. It doesn't protected by mutex and
+// must be called before `bc.Run()` to avoid data race.
+func (bc *Blockchain) SetNotary(mod services.Notary) {
+	bc.contracts.Designate.NotaryService.Store(mod)
+}
+
 func (bc *Blockchain) init() error {
 	// If we could not find the version in the Store, we know that there is nothing stored.
 	ver, err := bc.dao.GetVersion()
@@ -477,7 +483,7 @@ func (bc *Blockchain) AddBlock(block *block.Block) error {
 		if !block.MerkleRoot.Equals(merkle) {
 			return errors.New("invalid block: MerkleRoot mismatch")
 		}
-		mp = mempool.New(len(block.Transactions), 0)
+		mp = mempool.New(len(block.Transactions), 0, false)
 		for _, tx := range block.Transactions {
 			var err error
 			// Transactions are verified before adding them
@@ -1637,7 +1643,7 @@ func (bc *Blockchain) verifyStateRootWitness(r *state.MPTRoot) error {
 // current blockchain state. Note that this verification is completely isolated
 // from the main node's mempool.
 func (bc *Blockchain) VerifyTx(t *transaction.Transaction) error {
-	var mp = mempool.New(1, 0)
+	var mp = mempool.New(1, 0, false)
 	bc.lock.RLock()
 	defer bc.lock.RUnlock()
 	return bc.verifyAndPoolTx(t, mp, bc)

pkg/core/blockchain_test.go

@@ -449,7 +449,7 @@ func TestVerifyTx(t *testing.T) {
 		require.True(t, errors.Is(err, ErrAlreadyExists))
 	})
 	t.Run("MemPoolOOM", func(t *testing.T) {
-		bc.memPool = mempool.New(1, 0)
+		bc.memPool = mempool.New(1, 0, false)
 		tx1 := bc.newTestTx(h, testScript)
 		tx1.NetworkFee += 10000 // Give it more priority.
 		require.NoError(t, accs[0].SignTx(tx1))
@@ -988,7 +988,7 @@ func TestVerifyTx(t *testing.T) {
 			return tx
 		}
 
-		mp := mempool.New(10, 1)
+		mp := mempool.New(10, 1, false)
 		verificationF := func(bc blockchainer.Blockchainer, tx *transaction.Transaction, data interface{}) error {
 			if data.(int) > 5 {
 				return errors.New("bad data")

pkg/core/blockchainer/blockchainer.go

@@ -65,6 +65,7 @@ type Blockchainer interface {
 	PoolTx(t *transaction.Transaction, pools ...*mempool.Pool) error
 	PoolTxWithData(t *transaction.Transaction, data interface{}, mp *mempool.Pool, feer mempool.Feer, verificationFunction func(bc Blockchainer, t *transaction.Transaction, data interface{}) error) error
 	RegisterPostBlock(f func(Blockchainer, *mempool.Pool, *block.Block))
+	SetNotary(mod services.Notary)
 	SubscribeForBlocks(ch chan<- *block.Block)
 	SubscribeForExecutions(ch chan<- *state.AppExecResult)
 	SubscribeForNotifications(ch chan<- *state.NotificationEvent)

pkg/core/blockchainer/services/notary.go

@@ -0,0 +1,8 @@
+package services
+
+import "github.com/nspcc-dev/neo-go/pkg/crypto/keys"
+
+// Notary is a Notary module interface.
+type Notary interface {
+	UpdateNotaryNodes(pubs keys.PublicKeys)
+}

pkg/core/helper_test.go

@@ -15,6 +15,7 @@ import (
 	"github.com/nspcc-dev/neo-go/internal/testserdes"
 	"github.com/nspcc-dev/neo-go/pkg/config"
 	"github.com/nspcc-dev/neo-go/pkg/core/block"
+	"github.com/nspcc-dev/neo-go/pkg/core/blockchainer"
 	"github.com/nspcc-dev/neo-go/pkg/core/chaindump"
 	"github.com/nspcc-dev/neo-go/pkg/core/fee"
 	"github.com/nspcc-dev/neo-go/pkg/core/native"
@@ -399,6 +400,9 @@ func newNEP17Transfer(sc, from, to util.Uint160, amount int64, additionalArgs ..
 	w := io.NewBufBinWriter()
 	emit.AppCall(w.BinWriter, sc, "transfer", callflag.All, from, to, amount, additionalArgs)
 	emit.Opcodes(w.BinWriter, opcode.ASSERT)
+	if w.Err != nil {
+		panic(fmt.Errorf("failed to create nep17 transfer transaction: %w", w.Err))
+	}
 
 	script := w.Bytes()
 	return transaction.New(testchain.Network(), script, 11000000)
@@ -555,6 +559,14 @@ func invokeContractMethodBy(t *testing.T, chain *Blockchain, signer *wallet.Acco
 	return invokeContractMethodGeneric(chain, sysfee, hash, method, signer, args...)
 }
 
+func transferTokenFromMultisigAccountCheckOK(t *testing.T, chain *Blockchain, to, tokenHash util.Uint160, amount int64, additionalArgs ...interface{}) {
+	transferTx := transferTokenFromMultisigAccount(t, chain, to, tokenHash, amount, additionalArgs...)
+	res, err := chain.GetAppExecResults(transferTx.Hash(), trigger.Application)
+	require.NoError(t, err)
+	require.Equal(t, vm.HaltState, res[0].VMState)
+	require.Equal(t, 0, len(res[0].Stack))
+}
+
 func transferTokenFromMultisigAccount(t *testing.T, chain *Blockchain, to, tokenHash util.Uint160, amount int64, additionalArgs ...interface{}) *transaction.Transaction {
 	transferTx := newNEP17Transfer(tokenHash, testchain.MultisigScriptHash(), to, amount, additionalArgs...)
 	transferTx.SystemFee = 100000000
@@ -580,3 +592,19 @@ func checkBalanceOf(t *testing.T, chain *Blockchain, addr util.Uint160, expected
 	balance := chain.GetNEP17Balances(addr).Trackers[chain.contracts.GAS.ContractID]
 	require.Equal(t, int64(expected), balance.Balance.Int64())
 }
+
+type NotaryFeerStub struct {
+	bc blockchainer.Blockchainer
+}
+
+func (f NotaryFeerStub) FeePerByte() int64 { return f.bc.FeePerByte() }
+func (f NotaryFeerStub) GetUtilityTokenBalance(acc util.Uint160) *big.Int {
+	return f.bc.GetNotaryBalance(acc)
+}
+func (f NotaryFeerStub) BlockHeight() uint32           { return f.bc.BlockHeight() }
+func (f NotaryFeerStub) P2PSigExtensionsEnabled() bool { return f.bc.P2PSigExtensionsEnabled() }
+func NewNotaryFeerStub(bc blockchainer.Blockchainer) NotaryFeerStub {
+	return NotaryFeerStub{
+		bc: bc,
+	}
+}

pkg/core/mempool/mem_pool.go

@@ -10,6 +10,7 @@ import (
 
 	"github.com/nspcc-dev/neo-go/pkg/core/transaction"
 	"github.com/nspcc-dev/neo-go/pkg/util"
+	"go.uber.org/atomic"
 )
 
 var (
@@ -69,6 +70,14 @@ type Pool struct {
 
 	resendThreshold uint32
 	resendFunc      func(*transaction.Transaction, interface{})
+
+	// subscriptions for mempool events
+	subscriptionsEnabled bool
+	subscriptionsOn      atomic.Bool
+	stopCh               chan struct{}
+	events               chan Event
+	subCh                chan chan<- Event // there are no other events in mempool except Event, so no need in generic subscribers type
+	unsubCh              chan chan<- Event
 }
 
 func (p items) Len() int           { return len(p) }
@@ -249,6 +258,13 @@ func (mp *Pool) Add(t *transaction.Transaction, fee Feer, data ...interface{}) e
 			delete(mp.oracleResp, attrs[0].Value.(*transaction.OracleResponse).ID)
 		}
 		mp.verifiedTxes[len(mp.verifiedTxes)-1] = pItem
+		if mp.subscriptionsOn.Load() {
+			mp.events <- Event{
+				Type: TransactionRemoved,
+				Tx:   unlucky.txn,
+				Data: unlucky.data,
+			}
+		}
 	} else {
 		mp.verifiedTxes = append(mp.verifiedTxes, pItem)
 	}
@@ -269,6 +285,14 @@ func (mp *Pool) Add(t *transaction.Transaction, fee Feer, data ...interface{}) e
 
 	updateMempoolMetrics(len(mp.verifiedTxes))
 	mp.lock.Unlock()
+
+	if mp.subscriptionsOn.Load() {
+		mp.events <- Event{
+			Type: TransactionAdded,
+			Tx:   pItem.txn,
+			Data: pItem.data,
+		}
+	}
 	return nil
 }
 
@@ -307,6 +331,13 @@ func (mp *Pool) removeInternal(hash util.Uint256, feer Feer) {
 		if attrs := tx.GetAttributes(transaction.OracleResponseT); len(attrs) != 0 {
 			delete(mp.oracleResp, attrs[0].Value.(*transaction.OracleResponse).ID)
 		}
+		if mp.subscriptionsOn.Load() {
+			mp.events <- Event{
+				Type: TransactionRemoved,
+				Tx:   itm.txn,
+				Data: itm.data,
+			}
+		}
 	}
 	updateMempoolMetrics(len(mp.verifiedTxes))
 }
@@ -325,7 +356,9 @@ func (mp *Pool) RemoveStale(isOK func(*transaction.Transaction) bool, feer Feer)
 		mp.conflicts = make(map[util.Uint256][]util.Uint256)
 	}
 	height := feer.BlockHeight()
-	var staleItems []item
+	var (
+		staleItems []item
+	)
 	for _, itm := range mp.verifiedTxes {
 		if isOK(itm.txn) && mp.checkPolicy(itm.txn, policyChanged) && mp.tryAddSendersFee(itm.txn, feer, true) {
 			newVerifiedTxes = append(newVerifiedTxes, itm)
@@ -348,6 +381,13 @@ func (mp *Pool) RemoveStale(isOK func(*transaction.Transaction) bool, feer Feer)
 			if attrs := itm.txn.GetAttributes(transaction.OracleResponseT); len(attrs) != 0 {
 				delete(mp.oracleResp, attrs[0].Value.(*transaction.OracleResponse).ID)
 			}
+			if mp.subscriptionsOn.Load() {
+				mp.events <- Event{
+					Type: TransactionRemoved,
+					Tx:   itm.txn,
+					Data: itm.data,
+				}
+			}
 		}
 	}
 	if len(staleItems) != 0 {
@@ -377,8 +417,8 @@ func (mp *Pool) checkPolicy(tx *transaction.Transaction, policyChanged bool) boo
 }
 
 // New returns a new Pool struct.
-func New(capacity int, payerIndex int) *Pool {
-	return &Pool{
+func New(capacity int, payerIndex int, enableSubscriptions bool) *Pool {
+	mp := &Pool{
 		verifiedMap:          make(map[util.Uint256]*transaction.Transaction),
 		verifiedTxes:         make([]item, 0, capacity),
 		capacity:             capacity,
@@ -386,7 +426,14 @@ func New(capacity int, payerIndex int) *Pool {
 		fees:                 make(map[util.Uint160]utilityBalanceAndFees),
 		conflicts:            make(map[util.Uint256][]util.Uint256),
 		oracleResp:           make(map[uint64]util.Uint256),
+		subscriptionsEnabled: enableSubscriptions,
+		stopCh:               make(chan struct{}),
+		events:               make(chan Event),
+		subCh:                make(chan chan<- Event),
+		unsubCh:              make(chan chan<- Event),
 	}
+	mp.subscriptionsOn.Store(false)
+	return mp
 }
 
 // SetResendThreshold sets threshold after which transaction will be considered stale

pkg/core/mempool/mem_pool_test.go

@@ -45,7 +45,7 @@ func (fs *FeerStub) P2PSigExtensionsEnabled() bool {
 }
 
 func testMemPoolAddRemoveWithFeer(t *testing.T, fs Feer) {
-	mp := New(10, 0)
+	mp := New(10, 0, false)
 	tx := transaction.New(netmode.UnitTestNet, []byte{byte(opcode.PUSH1)}, 0)
 	tx.Nonce = 0
 	tx.Signers = []transaction.Signer{{Account: util.Uint160{1, 2, 3}}}
@@ -66,7 +66,7 @@ func testMemPoolAddRemoveWithFeer(t *testing.T, fs Feer) {
 }
 
 func TestMemPoolRemoveStale(t *testing.T) {
-	mp := New(5, 0)
+	mp := New(5, 0, false)
 	txs := make([]*transaction.Transaction, 5)
 	for i := range txs {
 		txs[i] = transaction.New(netmode.UnitTestNet, []byte{byte(opcode.PUSH1)}, 0)
@@ -117,7 +117,7 @@ func TestMemPoolAddRemove(t *testing.T) {
 func TestOverCapacity(t *testing.T) {
 	var fs = &FeerStub{balance: 10000000}
 	const mempoolSize = 10
-	mp := New(mempoolSize, 0)
+	mp := New(mempoolSize, 0, false)
 
 	for i := 0; i < mempoolSize; i++ {
 		tx := transaction.New(netmode.UnitTestNet, []byte{byte(opcode.PUSH1)}, 0)
@@ -193,7 +193,7 @@ func TestOverCapacity(t *testing.T) {
 func TestGetVerified(t *testing.T) {
 	var fs = &FeerStub{}
 	const mempoolSize = 10
-	mp := New(mempoolSize, 0)
+	mp := New(mempoolSize, 0, false)
 
 	txes := make([]*transaction.Transaction, 0, mempoolSize)
 	for i := 0; i < mempoolSize; i++ {
@@ -217,7 +217,7 @@ func TestGetVerified(t *testing.T) {
 func TestRemoveStale(t *testing.T) {
 	var fs = &FeerStub{}
 	const mempoolSize = 10
-	mp := New(mempoolSize, 0)
+	mp := New(mempoolSize, 0, false)
 
 	txes1 := make([]*transaction.Transaction, 0, mempoolSize/2)
 	txes2 := make([]*transaction.Transaction, 0, mempoolSize/2)
@@ -250,7 +250,7 @@ func TestRemoveStale(t *testing.T) {
 }
 
 func TestMemPoolFees(t *testing.T) {
-	mp := New(10, 0)
+	mp := New(10, 0, false)
 	fs := &FeerStub{balance: 10000000}
 	sender0 := util.Uint160{1, 2, 3}
 	tx0 := transaction.New(netmode.UnitTestNet, []byte{byte(opcode.PUSH1)}, 0)
@@ -361,7 +361,7 @@ func TestMempoolItemsOrder(t *testing.T) {
 }
 
 func TestMempoolAddRemoveOracleResponse(t *testing.T) {
-	mp := New(3, 0)
+	mp := New(3, 0, false)
 	nonce := uint32(0)
 	fs := &FeerStub{balance: 10000}
 	newTx := func(netFee int64, id uint64) *transaction.Transaction {
@@ -431,7 +431,7 @@ func TestMempoolAddRemoveOracleResponse(t *testing.T) {
 
 func TestMempoolAddRemoveConflicts(t *testing.T) {
 	capacity := 6
-	mp := New(capacity, 0)
+	mp := New(capacity, 0, false)
 	var (
 		fs           = &FeerStub{p2pSigExt: true, balance: 100000}
 		nonce uint32 = 1
@@ -561,7 +561,7 @@ func TestMempoolAddWithDataGetData(t *testing.T) {
 		blockHeight: 5,
 		balance:     100,
 	}
-	mp := New(10, 1)
+	mp := New(10, 1, false)
 	newTx := func(t *testing.T, netFee int64) *transaction.Transaction {
 		tx := transaction.New(netmode.UnitTestNet, []byte{byte(opcode.RET)}, 0)
 		tx.Signers = []transaction.Signer{{}, {}}

pkg/core/mempool/subscriptions.go

@@ -0,0 +1,86 @@
+package mempool
+
+import (
+	"github.com/nspcc-dev/neo-go/pkg/core/transaction"
+)
+
+// EventType represents mempool event type.
+type EventType byte
+
+const (
+	// TransactionAdded marks transaction addition mempool event.
+	TransactionAdded EventType = 0x01
+	// TransactionRemoved marks transaction removal mempool event.
+	TransactionRemoved EventType = 0x02
+)
+
+// Event represents one of mempool events: transaction was added or removed from mempool.
+type Event struct {
+	Type EventType
+	Tx   *transaction.Transaction
+	Data interface{}
+}
+
+// RunSubscriptions runs subscriptions goroutine if mempool subscriptions are enabled.
+// You should manually free the resources by calling StopSubscriptions on mempool shutdown.
+func (mp *Pool) RunSubscriptions() {
+	if !mp.subscriptionsEnabled {
+		panic("subscriptions are disabled")
+	}
+	if !mp.subscriptionsOn.Load() {
+		mp.subscriptionsOn.Store(true)
+		go mp.notificationDispatcher()
+	}
+}
+
+// StopSubscriptions stops mempool events loop.
+func (mp *Pool) StopSubscriptions() {
+	if !mp.subscriptionsEnabled {
+		panic("subscriptions are disabled")
+	}
+	if mp.subscriptionsOn.Load() {
+		mp.subscriptionsOn.Store(false)
+		close(mp.stopCh)
+	}
+}
+
+// SubscribeForTransactions adds given channel to new mempool event broadcasting, so when
+// there is a new transactions added to mempool or an existing transaction removed from
+// mempool you'll receive it via this channel.
+func (mp *Pool) SubscribeForTransactions(ch chan<- Event) {
+	if mp.subscriptionsOn.Load() {
+		mp.subCh <- ch
+	}
+}
+
+// UnsubscribeFromTransactions unsubscribes given channel from new mempool notifications,
+// you can close it afterwards. Passing non-subscribed channel is a no-op.
+func (mp *Pool) UnsubscribeFromTransactions(ch chan<- Event) {
+	if mp.subscriptionsOn.Load() {
+		mp.unsubCh <- ch
+	}
+}
+
+// notificationDispatcher manages subscription to events and broadcasts new events.
+func (mp *Pool) notificationDispatcher() {
+	var (
+		// These are just sets of subscribers, though modelled as maps
+		// for ease of management (not a lot of subscriptions is really
+		// expected, but maps are convenient for adding/deleting elements).
+		txFeed = make(map[chan<- Event]bool)
+	)
+	for {
+		select {
+		case <-mp.stopCh:
+			return
+		case sub := <-mp.subCh:
+			txFeed[sub] = true
+		case unsub := <-mp.unsubCh:
+			delete(txFeed, unsub)
+		case event := <-mp.events:
+			for ch := range txFeed {
+				ch <- event
+			}
+		}
+	}
+}

pkg/core/mempool/subscriptions_test.go

@@ -0,0 +1,98 @@
+package mempool
+
+import (
+	"testing"
+	"time"
+
+	"github.com/nspcc-dev/neo-go/pkg/config/netmode"
+	"github.com/nspcc-dev/neo-go/pkg/core/transaction"
+	"github.com/nspcc-dev/neo-go/pkg/util"
+	"github.com/nspcc-dev/neo-go/pkg/vm/opcode"
+	"github.com/stretchr/testify/require"
+)
+
+func TestSubscriptions(t *testing.T) {
+	t.Run("disabled subscriptions", func(t *testing.T) {
+		mp := New(5, 0, false)
+		require.Panics(t, func() {
+			mp.RunSubscriptions()
+		})
+		require.Panics(t, func() {
+			mp.StopSubscriptions()
+		})
+	})
+
+	t.Run("enabled subscriptions", func(t *testing.T) {
+		fs := &FeerStub{balance: 100}
+		mp := New(2, 0, true)
+		mp.RunSubscriptions()
+		subChan1 := make(chan Event, 3)
+		subChan2 := make(chan Event, 3)
+		mp.SubscribeForTransactions(subChan1)
+		defer mp.StopSubscriptions()
+
+		txs := make([]*transaction.Transaction, 4)
+		for i := range txs {
+			txs[i] = transaction.New(netmode.UnitTestNet, []byte{byte(opcode.PUSH1)}, 0)
+			txs[i].Nonce = uint32(i)
+			txs[i].Signers = []transaction.Signer{{Account: util.Uint160{1, 2, 3}}}
+			txs[i].NetworkFee = int64(i)
+		}
+
+		// add tx
+		require.NoError(t, mp.Add(txs[0], fs))
+		require.Eventually(t, func() bool { return len(subChan1) == 1 }, time.Second, time.Millisecond*100)
+		event := <-subChan1
+		require.Equal(t, Event{Type: TransactionAdded, Tx: txs[0]}, event)
+
+		// severak subscribers
+		mp.SubscribeForTransactions(subChan2)
+		require.NoError(t, mp.Add(txs[1], fs))
+		require.Eventually(t, func() bool { return len(subChan1) == 1 && len(subChan2) == 1 }, time.Second, time.Millisecond*100)
+		event1 := <-subChan1
+		event2 := <-subChan2
+		require.Equal(t, Event{Type: TransactionAdded, Tx: txs[1]}, event1)
+		require.Equal(t, Event{Type: TransactionAdded, Tx: txs[1]}, event2)
+
+		// reach capacity
+		require.NoError(t, mp.Add(txs[2], &FeerStub{}))
+		require.Eventually(t, func() bool { return len(subChan1) == 2 && len(subChan2) == 2 }, time.Second, time.Millisecond*100)
+		event1 = <-subChan1
+		event2 = <-subChan2
+		require.Equal(t, Event{Type: TransactionRemoved, Tx: txs[0]}, event1)
+		require.Equal(t, Event{Type: TransactionRemoved, Tx: txs[0]}, event2)
+		event1 = <-subChan1
+		event2 = <-subChan2
+		require.Equal(t, Event{Type: TransactionAdded, Tx: txs[2]}, event1)
+		require.Equal(t, Event{Type: TransactionAdded, Tx: txs[2]}, event2)
+
+		// remove tx
+		mp.Remove(txs[1].Hash(), fs)
+		require.Eventually(t, func() bool { return len(subChan1) == 1 && len(subChan2) == 1 }, time.Second, time.Millisecond*100)
+		event1 = <-subChan1
+		event2 = <-subChan2
+		require.Equal(t, Event{Type: TransactionRemoved, Tx: txs[1]}, event1)
+		require.Equal(t, Event{Type: TransactionRemoved, Tx: txs[1]}, event2)
+
+		// remove stale
+		mp.RemoveStale(func(tx *transaction.Transaction) bool {
+			if tx.Hash().Equals(txs[2].Hash()) {
+				return false
+			}
+			return true
+		}, fs)
+		require.Eventually(t, func() bool { return len(subChan1) == 1 && len(subChan2) == 1 }, time.Second, time.Millisecond*100)
+		event1 = <-subChan1
+		event2 = <-subChan2
+		require.Equal(t, Event{Type: TransactionRemoved, Tx: txs[2]}, event1)
+		require.Equal(t, Event{Type: TransactionRemoved, Tx: txs[2]}, event2)
+
+		// unsubscribe
+		mp.UnsubscribeFromTransactions(subChan1)
+		require.NoError(t, mp.Add(txs[3], fs))
+		require.Eventually(t, func() bool { return len(subChan2) == 1 }, time.Second, time.Millisecond*100)
+		event2 = <-subChan2
+		require.Equal(t, 0, len(subChan1))
+		require.Equal(t, Event{Type: TransactionAdded, Tx: txs[3]}, event2)
+	})
+}

pkg/core/native/designate.go

@@ -37,6 +37,8 @@ type Designate struct {
 	p2pSigExtensionsEnabled bool
 
 	OracleService atomic.Value
+	// NotaryService represents Notary node module.
+	NotaryService atomic.Value
 }
 
 type roleData struct {
@@ -183,10 +185,15 @@ func (s *Designate) updateCachedRoleData(v *atomic.Value, d dao.DAO, r Role) err
 		addr:   s.hashFromNodes(r, nodeKeys),
 		height: height,
 	})
-	if r == RoleOracle {
+	switch r {
+	case RoleOracle:
 		if orc, _ := s.OracleService.Load().(services.Oracle); orc != nil {
 			orc.UpdateOracleNodes(nodeKeys.Copy())
 		}
+	case RoleP2PNotary:
+		if ntr, _ := s.NotaryService.Load().(services.Notary); ntr != nil {
+			ntr.UpdateNotaryNodes(nodeKeys.Copy())
+		}
 	}
 	return nil
 }

pkg/core/notary_test.go

@@ -0,0 +1,647 @@
+package core
+
+import (
+	"bytes"
+	"errors"
+	"fmt"
+	"math/rand"
+	"path"
+	"sync"
+	"testing"
+	"time"
+
+	"github.com/nspcc-dev/neo-go/internal/testchain"
+	"github.com/nspcc-dev/neo-go/pkg/config"
+	"github.com/nspcc-dev/neo-go/pkg/config/netmode"
+	"github.com/nspcc-dev/neo-go/pkg/core/block"
+	"github.com/nspcc-dev/neo-go/pkg/core/blockchainer"
+	"github.com/nspcc-dev/neo-go/pkg/core/mempool"
+	"github.com/nspcc-dev/neo-go/pkg/core/native"
+	"github.com/nspcc-dev/neo-go/pkg/core/transaction"
+	"github.com/nspcc-dev/neo-go/pkg/crypto/hash"
+	"github.com/nspcc-dev/neo-go/pkg/crypto/keys"
+	"github.com/nspcc-dev/neo-go/pkg/network/payload"
+	"github.com/nspcc-dev/neo-go/pkg/services/notary"
+	"github.com/nspcc-dev/neo-go/pkg/smartcontract"
+	"github.com/nspcc-dev/neo-go/pkg/smartcontract/trigger"
+	"github.com/nspcc-dev/neo-go/pkg/util"
+	"github.com/nspcc-dev/neo-go/pkg/vm/opcode"
+	"github.com/nspcc-dev/neo-go/pkg/wallet"
+	"github.com/stretchr/testify/require"
+	"go.uber.org/zap/zaptest"
+)
+
+const notaryModulePath = "../services/notary/"
+
+func getTestNotary(t *testing.T, bc *Blockchain, walletPath, pass string, onTx func(tx *transaction.Transaction) error) (*wallet.Account, *notary.Notary, *mempool.Pool) {
+	bc.config.P2PNotary = config.P2PNotary{
+		Enabled: true,
+		UnlockWallet: config.Wallet{
+			Path:     path.Join(notaryModulePath, walletPath),
+			Password: pass,
+		},
+	}
+	mp := mempool.New(10, 1, true)
+	ntr, err := notary.NewNotary(bc, mp, zaptest.NewLogger(t), onTx)
+	require.NoError(t, err)
+
+	w, err := wallet.NewWalletFromFile(path.Join(notaryModulePath, walletPath))
+	require.NoError(t, err)
+	require.NoError(t, w.Accounts[0].Decrypt(pass))
+	return w.Accounts[0], ntr, mp
+}
+
+func TestNotary(t *testing.T) {
+	bc := newTestChain(t)
+	defer bc.Close()
+	var (
+		nonce           uint32
+		nvbDiffFallback uint32 = 20
+	)
+
+	mtx := sync.RWMutex{}
+	completedTxes := make(map[util.Uint256]*transaction.Transaction)
+	var unluckies []*payload.P2PNotaryRequest
+	var (
+		finalizeWithError bool
+		choosy            bool
+	)
+	onTransaction := func(tx *transaction.Transaction) error {
+		mtx.Lock()
+		defer mtx.Unlock()
+		if !choosy {
+			if completedTxes[tx.Hash()] != nil {
+				panic("transaction was completed twice")
+			}
+			if finalizeWithError {
+				return errors.New("error while finalizing transaction")
+			}
+			completedTxes[tx.Hash()] = tx
+			return nil
+		}
+		for _, unl := range unluckies {
+			if tx.Hash().Equals(unl.FallbackTransaction.Hash()) {
+				return errors.New("error while finalizing transaction")
+			}
+		}
+		completedTxes[tx.Hash()] = tx
+		return nil
+	}
+
+	acc1, ntr1, mp1 := getTestNotary(t, bc, "./testdata/notary1.json", "one", onTransaction)
+	acc2, _, _ := getTestNotary(t, bc, "./testdata/notary2.json", "two", onTransaction)
+	randomAcc, err := keys.NewPrivateKey()
+	require.NoError(t, err)
+
+	bc.SetNotary(ntr1)
+	bc.RegisterPostBlock(func(bc blockchainer.Blockchainer, pool *mempool.Pool, b *block.Block) {
+		ntr1.PostPersist(bc, pool, b)
+	})
+
+	notaryNodes := keys.PublicKeys{acc1.PrivateKey().PublicKey(), acc2.PrivateKey().PublicKey()}
+	bc.setNodesByRole(t, true, native.RoleP2PNotary, notaryNodes)
+
+	createFallbackTx := func(requester *wallet.Account, mainTx *transaction.Transaction, nvbIncrement ...uint32) *transaction.Transaction {
+		fallback := transaction.New(testchain.Network(), []byte{byte(opcode.RET)}, 2000_0000)
+		fallback.Nonce = nonce
+		nonce++
+		fallback.SystemFee = 1_0000_0000
+		fallback.ValidUntilBlock = bc.BlockHeight() + 50
+		fallback.Signers = []transaction.Signer{
+			{
+				Account: bc.GetNotaryContractScriptHash(),
+				Scopes:  transaction.None,
+			},
+			{
+				Account: requester.PrivateKey().PublicKey().GetScriptHash(),
+				Scopes:  transaction.None,
+			},
+		}
+		nvb := bc.BlockHeight() + nvbDiffFallback
+		if len(nvbIncrement) != 0 {
+			nvb += nvbIncrement[0]
+		}
+		fallback.Attributes = []transaction.Attribute{
+			{
+				Type:  transaction.NotaryAssistedT,
+				Value: &transaction.NotaryAssisted{NKeys: 0},
+			},
+			{
+				Type:  transaction.NotValidBeforeT,
+				Value: &transaction.NotValidBefore{Height: nvb},
+			},
+			{
+				Type:  transaction.ConflictsT,
+				Value: &transaction.Conflicts{Hash: mainTx.Hash()},
+			},
+		}
+		fallback.Scripts = []transaction.Witness{
+			{
+				InvocationScript:   append([]byte{byte(opcode.PUSHDATA1), 64}, make([]byte, 64)...),
+				VerificationScript: []byte{},
+			},
+		}
+		requester.SignTx(fallback)
+		return fallback
+	}
+
+	createStandardRequest := func(requesters []*wallet.Account, NVBincrements ...uint32) []*payload.P2PNotaryRequest {
+		mainTx := *transaction.New(testchain.Network(), []byte{byte(opcode.RET)}, 11000000)
+		mainTx.Nonce = nonce
+		nonce++
+		mainTx.SystemFee = 100000000
+		mainTx.ValidUntilBlock = bc.BlockHeight() + 2*nvbDiffFallback
+		signers := make([]transaction.Signer, len(requesters)+1)
+		for i := range requesters {
+			signers[i] = transaction.Signer{
+				Account: requesters[i].PrivateKey().PublicKey().GetScriptHash(),
+				Scopes:  transaction.None,
+			}
+		}
+		signers[len(signers)-1] = transaction.Signer{
+			Account: bc.GetNotaryContractScriptHash(),
+			Scopes:  transaction.None,
+		}
+		mainTx.Signers = signers
+		mainTx.Attributes = []transaction.Attribute{
+			{
+				Type:  transaction.NotaryAssistedT,
+				Value: &transaction.NotaryAssisted{NKeys: uint8(len(requesters))},
+			},
+		}
+		payloads := make([]*payload.P2PNotaryRequest, len(requesters))
+		for i := range payloads {
+			cp := mainTx
+			main := &cp
+			scripts := make([]transaction.Witness, len(requesters)+1)
+			for j := range requesters {
+				scripts[j].VerificationScript = requesters[j].PrivateKey().PublicKey().GetVerificationScript()
+			}
+			scripts[i].InvocationScript = append([]byte{byte(opcode.PUSHDATA1), 64}, requesters[i].PrivateKey().Sign(main.GetSignedPart())...)
+			main.Scripts = scripts
+			var fallback *transaction.Transaction
+			if len(NVBincrements) == len(requesters) {
+				fallback = createFallbackTx(requesters[i], main, NVBincrements[i])
+			} else {
+				fallback = createFallbackTx(requesters[i], main)
+			}
+			payloads[i] = &payload.P2PNotaryRequest{
+				MainTransaction:     main,
+				FallbackTransaction: fallback,
+				Network:             netmode.UnitTestNet,
+			}
+		}
+		return payloads
+	}
+	createMultisigRequest := func(m int, requesters []*wallet.Account) []*payload.P2PNotaryRequest {
+		mainTx := *transaction.New(testchain.Network(), []byte{byte(opcode.RET)}, 11000000)
+		mainTx.Nonce = nonce
+		nonce++
+		mainTx.SystemFee = 100000000
+		mainTx.ValidUntilBlock = bc.BlockHeight() + 2*nvbDiffFallback
+		pubs := make(keys.PublicKeys, len(requesters))
+		for i, r := range requesters {
+			pubs[i] = r.PrivateKey().PublicKey()
+		}
+		script, err := smartcontract.CreateMultiSigRedeemScript(m, pubs)
+		require.NoError(t, err)
+		mainTx.Signers = []transaction.Signer{
+			{
+				Account: hash.Hash160(script),
+				Scopes:  transaction.None,
+			},
+			{
+				Account: bc.GetNotaryContractScriptHash(),
+				Scopes:  transaction.None,
+			},
+		}
+		mainTx.Attributes = []transaction.Attribute{
+			{
+				Type:  transaction.NotaryAssistedT,
+				Value: &transaction.NotaryAssisted{NKeys: uint8(len(requesters))},
+			},
+		}
+
+		payloads := make([]*payload.P2PNotaryRequest, len(requesters))
+		// we'll collect only m signatures out of n (so only m payloads are needed), but let's create payloads for all requesters (for the next tests)
+		for i := range payloads {
+			cp := mainTx
+			main := &cp
+			main.Scripts = []transaction.Witness{
+				{
+					InvocationScript:   append([]byte{byte(opcode.PUSHDATA1), 64}, requesters[i].PrivateKey().Sign(main.GetSignedPart())...),
+					VerificationScript: script,
+				},
+				{}, // empty Notary witness
+			}
+			fallback := createFallbackTx(requesters[i], main)
+			payloads[i] = &payload.P2PNotaryRequest{
+				MainTransaction:     main,
+				FallbackTransaction: fallback,
+				Network:             netmode.UnitTestNet,
+			}
+		}
+		return payloads
+	}
+	checkSigTx := func(t *testing.T, requests []*payload.P2PNotaryRequest, sentCount int, shouldComplete bool) {
+		nKeys := len(requests)
+		completedTx := completedTxes[requests[0].MainTransaction.Hash()]
+		if sentCount == nKeys && shouldComplete {
+			require.NotNil(t, completedTx, errors.New("main transaction expected to be completed"))
+			require.Equal(t, nKeys+1, len(completedTx.Signers))
+			require.Equal(t, nKeys+1, len(completedTx.Scripts))
+			interopCtx := bc.newInteropContext(trigger.Verification, bc.dao, nil, completedTx)
+			for i, req := range requests {
+				require.Equal(t, req.MainTransaction.Scripts[i], completedTx.Scripts[i])
+				_, err := bc.verifyHashAgainstScript(completedTx.Signers[i].Account, &completedTx.Scripts[i], interopCtx, -1)
+				require.NoError(t, err)
+			}
+			require.Equal(t, transaction.Witness{
+				InvocationScript:   append([]byte{byte(opcode.PUSHDATA1), 64}, acc1.PrivateKey().Sign(requests[0].MainTransaction.GetSignedPart())...),
+				VerificationScript: []byte{},
+			}, completedTx.Scripts[nKeys])
+		} else {
+			require.Nil(t, completedTx, fmt.Errorf("main transaction shouldn't be completed: sent %d out of %d requests", sentCount, nKeys))
+		}
+	}
+	checkMultisigTx := func(t *testing.T, nSigs int, requests []*payload.P2PNotaryRequest, sentCount int, shouldComplete bool) {
+		completedTx := completedTxes[requests[0].MainTransaction.Hash()]
+		if sentCount >= nSigs && shouldComplete {
+			require.NotNil(t, completedTx, errors.New("main transaction expected to be completed"))
+			require.Equal(t, 2, len(completedTx.Signers))
+			require.Equal(t, 2, len(completedTx.Scripts))
+			interopCtx := bc.newInteropContext(trigger.Verification, bc.dao, nil, completedTx)
+			_, err := bc.verifyHashAgainstScript(completedTx.Signers[0].Account, &completedTx.Scripts[0], interopCtx, -1)
+			require.NoError(t, err)
+			require.Equal(t, transaction.Witness{
+				InvocationScript:   append([]byte{byte(opcode.PUSHDATA1), 64}, acc1.PrivateKey().Sign(requests[0].MainTransaction.GetSignedPart())...),
+				VerificationScript: []byte{},
+			}, completedTx.Scripts[1])
+			// check that only nSigs out of nKeys signatures are presented in the invocation script
+			for i, req := range requests[:nSigs] {
+				require.True(t, bytes.Contains(completedTx.Scripts[0].InvocationScript, req.MainTransaction.Scripts[0].InvocationScript), fmt.Errorf("signature from extra request #%d shouldn't be presented in the main tx", i))
+			}
+			// the rest (nKeys-nSigs) out of nKeys shouldn't be presented in the invocation script
+			for i, req := range requests[nSigs:] {
+				require.False(t, bytes.Contains(completedTx.Scripts[0].InvocationScript, req.MainTransaction.Scripts[0].InvocationScript), fmt.Errorf("signature from extra request #%d shouldn't be presented in the main tx", i))
+			}
+		} else {
+			require.Nil(t, completedTx, fmt.Errorf("main transaction shouldn't be completed: sent %d out of %d requests", sentCount, nSigs))
+		}
+	}
+	checkFallbackTxs := func(t *testing.T, requests []*payload.P2PNotaryRequest, shouldComplete bool) {
+		for i, req := range requests {
+			completedTx := completedTxes[req.FallbackTransaction.Hash()]
+			if shouldComplete {
+				require.NotNil(t, completedTx, fmt.Errorf("fallback transaction for request #%d expected to be completed", i))
+				require.Equal(t, 2, len(completedTx.Signers))
+				require.Equal(t, 2, len(completedTx.Scripts))
+				require.Equal(t, transaction.Witness{
+					InvocationScript:   append([]byte{byte(opcode.PUSHDATA1), 64}, acc1.PrivateKey().Sign(req.FallbackTransaction.GetSignedPart())...),
+					VerificationScript: []byte{},
+				}, completedTx.Scripts[0])
+				interopCtx := bc.newInteropContext(trigger.Verification, bc.dao, nil, completedTx)
+				_, err := bc.verifyHashAgainstScript(completedTx.Signers[1].Account, &completedTx.Scripts[1], interopCtx, -1)
+				require.NoError(t, err)
+			} else {
+				require.Nil(t, completedTx, fmt.Errorf("fallback transaction for request #%d shouldn't be completed", i))
+			}
+		}
+	}
+	checkCompleteStandardRequest := func(t *testing.T, nKeys int, shouldComplete bool, nvbIncrements ...uint32) []*payload.P2PNotaryRequest {
+		requesters := make([]*wallet.Account, nKeys)
+		for i := range requesters {
+			requesters[i], _ = wallet.NewAccount()
+		}
+
+		requests := createStandardRequest(requesters, nvbIncrements...)
+		sendOrder := make([]int, nKeys)
+		for i := range sendOrder {
+			sendOrder[i] = i
+		}
+		rand.Shuffle(nKeys, func(i, j int) {
+			sendOrder[j], sendOrder[i] = sendOrder[i], sendOrder[j]
+		})
+		for i := range requests {
+			ntr1.OnNewRequest(requests[sendOrder[i]])
+			checkSigTx(t, requests, i+1, shouldComplete)
+			completedCount := len(completedTxes)
+
+			// check that the same request won't be processed twice
+			ntr1.OnNewRequest(requests[sendOrder[i]])
+			checkSigTx(t, requests, i+1, shouldComplete)
+			require.Equal(t, completedCount, len(completedTxes))
+		}
+		return requests
+	}
+	checkCompleteMultisigRequest := func(t *testing.T, nSigs int, nKeys int, shouldComplete bool) []*payload.P2PNotaryRequest {
+		requesters := make([]*wallet.Account, nKeys)
+		for i := range requesters {
+			requesters[i], _ = wallet.NewAccount()
+		}
+		requests := createMultisigRequest(nSigs, requesters)
+		sendOrder := make([]int, nKeys)
+		for i := range sendOrder {
+			sendOrder[i] = i
+		}
+		rand.Shuffle(nKeys, func(i, j int) {
+			sendOrder[j], sendOrder[i] = sendOrder[i], sendOrder[j]
+		})
+
+		var submittedRequests []*payload.P2PNotaryRequest
+		// sent only nSigs (m out of n) requests - it should be enough to complete min tx
+		for i := 0; i < nSigs; i++ {
+			submittedRequests = append(submittedRequests, requests[sendOrder[i]])
+
+			ntr1.OnNewRequest(requests[sendOrder[i]])
+			checkMultisigTx(t, nSigs, submittedRequests, i+1, shouldComplete)
+
+			// check that the same request won't be processed twice
+			ntr1.OnNewRequest(requests[sendOrder[i]])
+			checkMultisigTx(t, nSigs, submittedRequests, i+1, shouldComplete)
+		}
+
+		// sent the rest (n-m) out of n requests: main tx is already collected, so only fallbacks should be applied
+		completedCount := len(completedTxes)
+		for i := nSigs; i < nKeys; i++ {
+			submittedRequests = append(submittedRequests, requests[sendOrder[i]])
+
+			ntr1.OnNewRequest(requests[sendOrder[i]])
+			checkMultisigTx(t, nSigs, submittedRequests, i+1, shouldComplete)
+			require.Equal(t, completedCount, len(completedTxes))
+		}
+
+		return submittedRequests
+	}
+
+	// OnNewRequest: missing account
+	ntr1.UpdateNotaryNodes(keys.PublicKeys{randomAcc.PublicKey()})
+	r := checkCompleteStandardRequest(t, 1, false)
+	checkFallbackTxs(t, r, false)
+	// set account back for the next tests
+	ntr1.UpdateNotaryNodes(keys.PublicKeys{acc1.PrivateKey().PublicKey()})
+
+	// OnNewRequest: signature request
+	for _, i := range []int{1, 2, 3, 10} {
+		r := checkCompleteStandardRequest(t, i, true)
+		checkFallbackTxs(t, r, false)
+	}
+
+	// OnNewRequest: multisignature request
+	r = checkCompleteMultisigRequest(t, 1, 1, true)
+	checkFallbackTxs(t, r, false)
+	r = checkCompleteMultisigRequest(t, 1, 2, true)
+	checkFallbackTxs(t, r, false)
+	r = checkCompleteMultisigRequest(t, 1, 3, true)
+	checkFallbackTxs(t, r, false)
+	r = checkCompleteMultisigRequest(t, 3, 3, true)
+	checkFallbackTxs(t, r, false)
+	r = checkCompleteMultisigRequest(t, 3, 4, true)
+	checkFallbackTxs(t, r, false)
+	r = checkCompleteMultisigRequest(t, 3, 10, true)
+	checkFallbackTxs(t, r, false)
+
+	// PostPersist: missing account
+	finalizeWithError = true
+	r = checkCompleteStandardRequest(t, 1, false)
+	checkFallbackTxs(t, r, false)
+	finalizeWithError = false
+	ntr1.UpdateNotaryNodes(keys.PublicKeys{randomAcc.PublicKey()})
+	require.NoError(t, bc.AddBlock(bc.newBlock()))
+	checkSigTx(t, r, 1, false)
+	checkFallbackTxs(t, r, false)
+	// set account back for the next tests
+	ntr1.UpdateNotaryNodes(keys.PublicKeys{acc1.PrivateKey().PublicKey()})
+
+	// PostPersist: complete main transaction, signature request
+	finalizeWithError = true
+	requests := checkCompleteStandardRequest(t, 3, false)
+	// check PostPersist with finalisation error
+	finalizeWithError = true
+	require.NoError(t, bc.AddBlock(bc.newBlock()))
+	checkSigTx(t, requests, len(requests), false)
+	// check PostPersist without finalisation error
+	finalizeWithError = false
+	require.NoError(t, bc.AddBlock(bc.newBlock()))
+	checkSigTx(t, requests, len(requests), true)
+
+	// PostPersist: complete main transaction, multisignature account
+	finalizeWithError = true
+	requests = checkCompleteMultisigRequest(t, 3, 4, false)
+	checkFallbackTxs(t, requests, false)
+	// check PostPersist with finalisation error
+	finalizeWithError = true
+	require.NoError(t, bc.AddBlock(bc.newBlock()))
+	checkMultisigTx(t, 3, requests, len(requests), false)
+	checkFallbackTxs(t, requests, false)
+	// check PostPersist without finalisation error
+	finalizeWithError = false
+	require.NoError(t, bc.AddBlock(bc.newBlock()))
+	checkMultisigTx(t, 3, requests, len(requests), true)
+	checkFallbackTxs(t, requests, false)
+
+	// PostPersist: complete fallback, signature request
+	finalizeWithError = true
+	requests = checkCompleteStandardRequest(t, 3, false)
+	checkFallbackTxs(t, requests, false)
+	// make fallbacks valid
+	_, err = bc.genBlocks(int(nvbDiffFallback))
+	require.NoError(t, err)
+	// check PostPersist for valid fallbacks with finalisation error
+	require.NoError(t, bc.AddBlock(bc.newBlock()))
+	checkSigTx(t, requests, len(requests), false)
+	checkFallbackTxs(t, requests, false)
+	// check PostPersist for valid fallbacks without finalisation error
+	finalizeWithError = false
+	require.NoError(t, bc.AddBlock(bc.newBlock()))
+	checkSigTx(t, requests, len(requests), false)
+	checkFallbackTxs(t, requests, true)
+
+	// PostPersist: complete fallback, multisignature request
+	nSigs, nKeys := 3, 5
+	// check OnNewRequest with finalization error
+	finalizeWithError = true
+	requests = checkCompleteMultisigRequest(t, nSigs, nKeys, false)
+	checkFallbackTxs(t, requests, false)
+	// make fallbacks valid
+	_, err = bc.genBlocks(int(nvbDiffFallback))
+	require.NoError(t, err)
+	// check PostPersist for valid fallbacks with finalisation error
+	require.NoError(t, bc.AddBlock(bc.newBlock()))
+	checkMultisigTx(t, nSigs, requests, len(requests), false)
+	checkFallbackTxs(t, requests, false)
+	// check PostPersist for valid fallbacks without finalisation error
+	finalizeWithError = false
+	require.NoError(t, bc.AddBlock(bc.newBlock()))
+	checkMultisigTx(t, nSigs, requests, len(requests), false)
+	checkFallbackTxs(t, requests[:nSigs], true)
+	// the rest of fallbacks should also be applied even if the main tx was already constructed by the moment they were sent
+	checkFallbackTxs(t, requests[nSigs:], true)
+
+	// PostPersist: partial fallbacks completion due to finalisation errors
+	finalizeWithError = true
+	requests = checkCompleteStandardRequest(t, 5, false)
+	checkFallbackTxs(t, requests, false)
+	// make fallbacks valid
+	_, err = bc.genBlocks(int(nvbDiffFallback))
+	require.NoError(t, err)
+	// some of fallbacks should fail finalisation
+	unluckies = []*payload.P2PNotaryRequest{requests[0], requests[4]}
+	lucky := requests[1:4]
+	choosy = true
+	// check PostPersist for lucky fallbacks
+	require.NoError(t, bc.AddBlock(bc.newBlock()))
+	checkSigTx(t, requests, len(requests), false)
+	checkFallbackTxs(t, lucky, true)
+	checkFallbackTxs(t, unluckies, false)
+	// reset finalisation function for unlucky fallbacks to finalise without an error
+	choosy = false
+	finalizeWithError = false
+	// check PostPersist for unlucky fallbacks
+	require.NoError(t, bc.AddBlock(bc.newBlock()))
+	checkSigTx(t, requests, len(requests), false)
+	checkFallbackTxs(t, lucky, true)
+	checkFallbackTxs(t, unluckies, true)
+
+	// PostPersist: different NVBs
+	// check OnNewRequest with finalization error and different NVBs
+	finalizeWithError = true
+	requests = checkCompleteStandardRequest(t, 5, false, 1, 2, 3, 4, 5)
+	checkFallbackTxs(t, requests, false)
+	// generate blocks to reach the most earlier fallback's NVB
+	_, err = bc.genBlocks(int(nvbDiffFallback))
+	require.NoError(t, err)
+	// check PostPersist for valid fallbacks without finalisation error
+	finalizeWithError = false
+	for i := range requests {
+		require.NoError(t, bc.AddBlock(bc.newBlock()))
+		checkSigTx(t, requests, len(requests), false)
+		checkFallbackTxs(t, requests[:i+1], true)
+		checkFallbackTxs(t, requests[i+1:], false)
+	}
+
+	// OnRequestRemoval: missing account
+	// check OnNewRequest with finalization error
+	finalizeWithError = true
+	requests = checkCompleteStandardRequest(t, 4, false)
+	checkFallbackTxs(t, requests, false)
+	// make fallbacks valid and remove one fallback
+	_, err = bc.genBlocks(int(nvbDiffFallback))
+	require.NoError(t, err)
+	ntr1.UpdateNotaryNodes(keys.PublicKeys{randomAcc.PublicKey()})
+	ntr1.OnRequestRemoval(requests[3])
+	// non of the fallbacks should be completed
+	finalizeWithError = false
+	require.NoError(t, bc.AddBlock(bc.newBlock()))
+	checkSigTx(t, requests, len(requests), false)
+	checkFallbackTxs(t, requests, false)
+	// set account back for the next tests
+	ntr1.UpdateNotaryNodes(keys.PublicKeys{acc1.PrivateKey().PublicKey()})
+
+	// OnRequestRemoval: signature request, remove one fallback
+	// check OnNewRequest with finalization error
+	finalizeWithError = true
+	requests = checkCompleteStandardRequest(t, 4, false)
+	checkFallbackTxs(t, requests, false)
+	// make fallbacks valid and remove one fallback
+	_, err = bc.genBlocks(int(nvbDiffFallback))
+	require.NoError(t, err)
+	unlucky := requests[3]
+	ntr1.OnRequestRemoval(unlucky)
+	// rest of the fallbacks should be completed
+	finalizeWithError = false
+	require.NoError(t, bc.AddBlock(bc.newBlock()))
+	checkSigTx(t, requests, len(requests), false)
+	checkFallbackTxs(t, requests[:3], true)
+	require.Nil(t, completedTxes[unlucky.FallbackTransaction.Hash()])
+
+	// OnRequestRemoval: signature request, remove all fallbacks
+	finalizeWithError = true
+	requests = checkCompleteStandardRequest(t, 4, false)
+	// remove all fallbacks
+	_, err = bc.genBlocks(int(nvbDiffFallback))
+	require.NoError(t, err)
+	for i := range requests {
+		ntr1.OnRequestRemoval(requests[i])
+	}
+	// then the whole request should be removed, i.e. there are no completed transactions
+	finalizeWithError = false
+	require.NoError(t, bc.AddBlock(bc.newBlock()))
+	checkSigTx(t, requests, len(requests), false)
+	checkFallbackTxs(t, requests, false)
+
+	// OnRequestRemoval: signature request, remove unexisting fallback
+	ntr1.OnRequestRemoval(requests[0])
+	require.NoError(t, bc.AddBlock(bc.newBlock()))
+	checkSigTx(t, requests, len(requests), false)
+	checkFallbackTxs(t, requests, false)
+
+	// OnRequestRemoval: multisignature request, remove one fallback
+	nSigs, nKeys = 3, 5
+	// check OnNewRequest with finalization error
+	finalizeWithError = true
+	requests = checkCompleteMultisigRequest(t, nSigs, nKeys, false)
+	checkMultisigTx(t, nSigs, requests, len(requests), false)
+	checkFallbackTxs(t, requests, false)
+	// make fallbacks valid and remove the last fallback
+	_, err = bc.genBlocks(int(nvbDiffFallback))
+	require.NoError(t, err)
+	unlucky = requests[nSigs-1]
+	ntr1.OnRequestRemoval(unlucky)
+	// then (m-1) out of n fallbacks should be completed
+	finalizeWithError = false
+	require.NoError(t, bc.AddBlock(bc.newBlock()))
+	checkMultisigTx(t, nSigs, requests, len(requests), false)
+	checkFallbackTxs(t, requests[:nSigs-1], true)
+	require.Nil(t, completedTxes[unlucky.FallbackTransaction.Hash()])
+	//  the rest (n-(m-1)) out of n fallbacks should also be completed even if main tx has been collected by the moment they were sent
+	checkFallbackTxs(t, requests[nSigs:], true)
+
+	// OnRequestRemoval: multisignature request, remove all fallbacks
+	finalizeWithError = true
+	requests = checkCompleteMultisigRequest(t, nSigs, nKeys, false)
+	// make fallbacks valid and then remove all of them
+	_, err = bc.genBlocks(int(nvbDiffFallback))
+	require.NoError(t, err)
+	for i := range requests {
+		ntr1.OnRequestRemoval(requests[i])
+	}
+	// then the whole request should be removed, i.e. there are no completed transactions
+	finalizeWithError = false
+	require.NoError(t, bc.AddBlock(bc.newBlock()))
+	checkMultisigTx(t, nSigs, requests, len(requests), false)
+	checkFallbackTxs(t, requests, false)
+
+	// // OnRequestRemoval: multisignature request, remove unexisting fallbac, i.e. there still shouldn't be any completed transactions after this
+	ntr1.OnRequestRemoval(requests[0])
+	require.NoError(t, bc.AddBlock(bc.newBlock()))
+	checkMultisigTx(t, nSigs, requests, len(requests), false)
+	checkFallbackTxs(t, requests, false)
+
+	// Subscriptions test
+	mp1.RunSubscriptions()
+	go ntr1.Run()
+	defer func() {
+		ntr1.Stop()
+		mp1.StopSubscriptions()
+	}()
+	finalizeWithError = false
+	requester1, _ := wallet.NewAccount()
+	requester2, _ := wallet.NewAccount()
+	amount := int64(100_0000_0000)
+	feer := NewNotaryFeerStub(bc)
+	transferTokenFromMultisigAccountCheckOK(t, bc, bc.GetNotaryContractScriptHash(), bc.contracts.GAS.Hash, amount, requester1.PrivateKey().PublicKey().GetScriptHash(), int64(bc.BlockHeight()+50))
+	checkBalanceOf(t, bc, bc.contracts.Notary.Hash, int(amount))
+	transferTokenFromMultisigAccountCheckOK(t, bc, bc.GetNotaryContractScriptHash(), bc.contracts.GAS.Hash, amount, requester2.PrivateKey().PublicKey().GetScriptHash(), int64(bc.BlockHeight()+50))
+	checkBalanceOf(t, bc, bc.contracts.Notary.Hash, int(2*amount))
+	// create request for 2 standard signatures => main tx should be completed after the second request is added to the pool
+	requests = createStandardRequest([]*wallet.Account{requester1, requester2})
+	require.NoError(t, mp1.Add(requests[0].FallbackTransaction, feer, requests[0]))
+	require.NoError(t, mp1.Add(requests[1].FallbackTransaction, feer, requests[1]))
+	require.Eventually(t, func() bool {
+		mtx.RLock()
+		defer mtx.RUnlock()
+		return completedTxes[requests[0].MainTransaction.Hash()] != nil
+	}, time.Second, time.Millisecond)
+	checkFallbackTxs(t, requests, false)
+}

pkg/network/blockqueue_test.go

@@ -4,13 +4,14 @@ import (
 	"testing"
 	"time"
 
+	"github.com/nspcc-dev/neo-go/internal/fakechain"
 	"github.com/nspcc-dev/neo-go/pkg/core/block"
 	"github.com/stretchr/testify/assert"
 	"go.uber.org/zap/zaptest"
 )
 
 func TestBlockQueue(t *testing.T) {
-	chain := newTestChain()
+	chain := fakechain.NewFakeChain()
 	// notice, it's not yet running
 	bq := newBlockQueue(0, chain, zaptest.NewLogger(t), nil)
 	blocks := make([]*block.Block, 11)

pkg/network/helper_test.go

@@ -1,333 +1,22 @@
 package network
 
 import (
-	"errors"
 	"fmt"
-	"math/big"
 	"net"
 	"sync"
 	"sync/atomic"
 	"testing"
 	"time"
 
-	"github.com/nspcc-dev/neo-go/pkg/config"
+	"github.com/nspcc-dev/neo-go/internal/fakechain"
 	"github.com/nspcc-dev/neo-go/pkg/config/netmode"
-	"github.com/nspcc-dev/neo-go/pkg/core/block"
-	"github.com/nspcc-dev/neo-go/pkg/core/blockchainer"
-	"github.com/nspcc-dev/neo-go/pkg/core/blockchainer/services"
-	"github.com/nspcc-dev/neo-go/pkg/core/interop"
-	"github.com/nspcc-dev/neo-go/pkg/core/mempool"
-	"github.com/nspcc-dev/neo-go/pkg/core/native"
-	"github.com/nspcc-dev/neo-go/pkg/core/state"
-	"github.com/nspcc-dev/neo-go/pkg/core/transaction"
-	"github.com/nspcc-dev/neo-go/pkg/crypto"
-	"github.com/nspcc-dev/neo-go/pkg/crypto/keys"
 	"github.com/nspcc-dev/neo-go/pkg/io"
 	"github.com/nspcc-dev/neo-go/pkg/network/capability"
 	"github.com/nspcc-dev/neo-go/pkg/network/payload"
-	"github.com/nspcc-dev/neo-go/pkg/smartcontract/trigger"
-	"github.com/nspcc-dev/neo-go/pkg/util"
-	"github.com/nspcc-dev/neo-go/pkg/vm"
 	"github.com/stretchr/testify/require"
 	"go.uber.org/zap/zaptest"
 )
 
-type testChain struct {
-	config.ProtocolConfiguration
-	*mempool.Pool
-	blocksCh                 []chan<- *block.Block
-	blockheight              uint32
-	poolTx                   func(*transaction.Transaction) error
-	poolTxWithData           func(*transaction.Transaction, interface{}, *mempool.Pool) error
-	blocks                   map[util.Uint256]*block.Block
-	hdrHashes                map[uint32]util.Uint256
-	txs                      map[util.Uint256]*transaction.Transaction
-	verifyWitnessF           func() error
-	maxVerificationGAS       int64
-	notaryContractScriptHash util.Uint160
-	notaryDepositExpiration  uint32
-	postBlock                []func(blockchainer.Blockchainer, *mempool.Pool, *block.Block)
-	utilityTokenBalance      *big.Int
-}
-
-func newTestChain() *testChain {
-	return &testChain{
-		Pool:                  mempool.New(10, 0),
-		poolTx:                func(*transaction.Transaction) error { return nil },
-		poolTxWithData:        func(*transaction.Transaction, interface{}, *mempool.Pool) error { return nil },
-		blocks:                make(map[util.Uint256]*block.Block),
-		hdrHashes:             make(map[uint32]util.Uint256),
-		txs:                   make(map[util.Uint256]*transaction.Transaction),
-		ProtocolConfiguration: config.ProtocolConfiguration{P2PNotaryRequestPayloadPoolSize: 10},
-	}
-}
-
-func (chain *testChain) putBlock(b *block.Block) {
-	chain.blocks[b.Hash()] = b
-	chain.hdrHashes[b.Index] = b.Hash()
-	atomic.StoreUint32(&chain.blockheight, b.Index)
-}
-func (chain *testChain) putHeader(b *block.Block) {
-	chain.hdrHashes[b.Index] = b.Hash()
-}
-
-func (chain *testChain) putTx(tx *transaction.Transaction) {
-	chain.txs[tx.Hash()] = tx
-}
-
-func (chain *testChain) ApplyPolicyToTxSet([]*transaction.Transaction) []*transaction.Transaction {
-	panic("TODO")
-}
-
-func (chain *testChain) IsTxStillRelevant(t *transaction.Transaction, txpool *mempool.Pool, isPartialTx bool) bool {
-	panic("TODO")
-}
-func (*testChain) IsExtensibleAllowed(uint160 util.Uint160) bool {
-	return true
-}
-
-func (chain *testChain) GetNotaryDepositExpiration(acc util.Uint160) uint32 {
-	if chain.notaryDepositExpiration != 0 {
-		return chain.notaryDepositExpiration
-	}
-	panic("TODO")
-}
-
-func (chain *testChain) GetNotaryContractScriptHash() util.Uint160 {
-	if !chain.notaryContractScriptHash.Equals(util.Uint160{}) {
-		return chain.notaryContractScriptHash
-	}
-	panic("TODO")
-}
-
-func (chain *testChain) GetNotaryBalance(acc util.Uint160) *big.Int {
-	panic("TODO")
-}
-
-func (chain *testChain) GetPolicer() blockchainer.Policer {
-	return chain
-}
-func (chain *testChain) GetBaseExecFee() int64 {
-	return interop.DefaultBaseExecFee
-}
-func (chain *testChain) GetStoragePrice() int64 {
-	return native.StoragePrice
-}
-func (chain *testChain) GetMaxVerificationGAS() int64 {
-	if chain.maxVerificationGAS != 0 {
-		return chain.maxVerificationGAS
-	}
-	panic("TODO")
-}
-
-func (chain *testChain) PoolTxWithData(t *transaction.Transaction, data interface{}, mp *mempool.Pool, feer mempool.Feer, verificationFunction func(bc blockchainer.Blockchainer, t *transaction.Transaction, data interface{}) error) error {
-	return chain.poolTxWithData(t, data, mp)
-}
-
-func (chain *testChain) RegisterPostBlock(f func(blockchainer.Blockchainer, *mempool.Pool, *block.Block)) {
-	chain.postBlock = append(chain.postBlock, f)
-}
-
-func (chain *testChain) GetConfig() config.ProtocolConfiguration {
-	return chain.ProtocolConfiguration
-}
-func (chain *testChain) CalculateClaimable(util.Uint160, uint32) (*big.Int, error) {
-	panic("TODO")
-}
-
-func (chain *testChain) FeePerByte() int64 {
-	panic("TODO")
-}
-
-func (chain *testChain) P2PSigExtensionsEnabled() bool {
-	return true
-}
-
-func (chain *testChain) GetMaxBlockSystemFee() int64 {
-	panic("TODO")
-}
-
-func (chain *testChain) GetMaxBlockSize() uint32 {
-	panic("TODO")
-}
-
-func (chain *testChain) AddHeaders(...*block.Header) error {
-	panic("TODO")
-}
-func (chain *testChain) AddBlock(block *block.Block) error {
-	if block.Index == atomic.LoadUint32(&chain.blockheight)+1 {
-		chain.putBlock(block)
-	}
-	return nil
-}
-func (chain *testChain) AddStateRoot(r *state.MPTRoot) error {
-	panic("TODO")
-}
-func (chain *testChain) BlockHeight() uint32 {
-	return atomic.LoadUint32(&chain.blockheight)
-}
-func (chain *testChain) Close() {
-	panic("TODO")
-}
-func (chain *testChain) HeaderHeight() uint32 {
-	return atomic.LoadUint32(&chain.blockheight)
-}
-func (chain *testChain) GetAppExecResults(hash util.Uint256, trig trigger.Type) ([]state.AppExecResult, error) {
-	panic("TODO")
-}
-func (chain *testChain) GetBlock(hash util.Uint256) (*block.Block, error) {
-	if b, ok := chain.blocks[hash]; ok {
-		return b, nil
-	}
-	return nil, errors.New("not found")
-}
-func (chain *testChain) GetCommittee() (keys.PublicKeys, error) {
-	panic("TODO")
-}
-func (chain *testChain) GetContractState(hash util.Uint160) *state.Contract {
-	panic("TODO")
-}
-func (chain *testChain) GetContractScriptHash(id int32) (util.Uint160, error) {
-	panic("TODO")
-}
-func (chain *testChain) GetNativeContractScriptHash(name string) (util.Uint160, error) {
-	panic("TODO")
-}
-func (chain *testChain) GetHeaderHash(n int) util.Uint256 {
-	return chain.hdrHashes[uint32(n)]
-}
-func (chain *testChain) GetHeader(hash util.Uint256) (*block.Header, error) {
-	b, err := chain.GetBlock(hash)
-	if err != nil {
-		return nil, err
-	}
-	return b.Header(), nil
-}
-
-func (chain *testChain) GetNextBlockValidators() ([]*keys.PublicKey, error) {
-	panic("TODO")
-}
-func (chain *testChain) ForEachNEP17Transfer(util.Uint160, func(*state.NEP17Transfer) (bool, error)) error {
-	panic("TODO")
-}
-func (chain *testChain) GetNEP17Balances(util.Uint160) *state.NEP17Balances {
-	panic("TODO")
-}
-func (chain *testChain) GetValidators() ([]*keys.PublicKey, error) {
-	panic("TODO")
-}
-func (chain *testChain) GetStandByCommittee() keys.PublicKeys {
-	panic("TODO")
-}
-func (chain *testChain) GetStandByValidators() keys.PublicKeys {
-	panic("TODO")
-}
-func (chain *testChain) GetEnrollments() ([]state.Validator, error) {
-	panic("TODO")
-}
-func (chain *testChain) GetStateProof(util.Uint256, []byte) ([][]byte, error) {
-	panic("TODO")
-}
-func (chain *testChain) GetStateRoot(height uint32) (*state.MPTRootState, error) {
-	panic("TODO")
-}
-func (chain *testChain) GetStorageItem(id int32, key []byte) *state.StorageItem {
-	panic("TODO")
-}
-func (chain *testChain) GetTestVM(t trigger.Type, tx *transaction.Transaction, b *block.Block) *vm.VM {
-	panic("TODO")
-}
-func (chain *testChain) GetStorageItems(id int32) (map[string]*state.StorageItem, error) {
-	panic("TODO")
-}
-func (chain *testChain) CurrentHeaderHash() util.Uint256 {
-	return util.Uint256{}
-}
-func (chain *testChain) CurrentBlockHash() util.Uint256 {
-	return util.Uint256{}
-}
-func (chain *testChain) HasBlock(h util.Uint256) bool {
-	_, ok := chain.blocks[h]
-	return ok
-}
-func (chain *testChain) HasTransaction(h util.Uint256) bool {
-	_, ok := chain.txs[h]
-	return ok
-}
-func (chain *testChain) GetTransaction(h util.Uint256) (*transaction.Transaction, uint32, error) {
-	if tx, ok := chain.txs[h]; ok {
-		return tx, 1, nil
-	}
-	return nil, 0, errors.New("not found")
-}
-
-func (chain *testChain) GetMemPool() *mempool.Pool {
-	return chain.Pool
-}
-
-func (chain *testChain) GetGoverningTokenBalance(acc util.Uint160) (*big.Int, uint32) {
-	panic("TODO")
-}
-
-func (chain *testChain) GetUtilityTokenBalance(uint160 util.Uint160) *big.Int {
-	if chain.utilityTokenBalance != nil {
-		return chain.utilityTokenBalance
-	}
-	panic("TODO")
-}
-func (chain testChain) ManagementContractHash() util.Uint160 {
-	panic("TODO")
-}
-
-func (chain *testChain) PoolTx(tx *transaction.Transaction, _ ...*mempool.Pool) error {
-	return chain.poolTx(tx)
-}
-func (chain testChain) SetOracle(services.Oracle) {
-	panic("TODO")
-}
-func (chain *testChain) SubscribeForBlocks(ch chan<- *block.Block) {
-	chain.blocksCh = append(chain.blocksCh, ch)
-}
-func (chain *testChain) SubscribeForExecutions(ch chan<- *state.AppExecResult) {
-	panic("TODO")
-}
-func (chain *testChain) SubscribeForNotifications(ch chan<- *state.NotificationEvent) {
-	panic("TODO")
-}
-func (chain *testChain) SubscribeForTransactions(ch chan<- *transaction.Transaction) {
-	panic("TODO")
-}
-
-func (chain *testChain) VerifyTx(*transaction.Transaction) error {
-	panic("TODO")
-}
-func (chain *testChain) VerifyWitness(util.Uint160, crypto.Verifiable, *transaction.Witness, int64) error {
-	if chain.verifyWitnessF != nil {
-		return chain.verifyWitnessF()
-	}
-	panic("TODO")
-}
-
-func (chain *testChain) UnsubscribeFromBlocks(ch chan<- *block.Block) {
-	for i, c := range chain.blocksCh {
-		if c == ch {
-			if i < len(chain.blocksCh) {
-				copy(chain.blocksCh[i:], chain.blocksCh[i+1:])
-			}
-			chain.blocksCh = chain.blocksCh[:len(chain.blocksCh)]
-		}
-	}
-}
-func (chain *testChain) UnsubscribeFromExecutions(ch chan<- *state.AppExecResult) {
-	panic("TODO")
-}
-func (chain *testChain) UnsubscribeFromNotifications(ch chan<- *state.NotificationEvent) {
-	panic("TODO")
-}
-func (chain *testChain) UnsubscribeFromTransactions(ch chan<- *transaction.Transaction) {
-	panic("TODO")
-}
-
 type testDiscovery struct {
 	sync.Mutex
 	bad          []string
@@ -500,7 +189,7 @@ func (p *localPeer) CanProcessAddr() bool {
 }
 
 func newTestServer(t *testing.T, serverConfig ServerConfig) *Server {
-	s, err := newServerFromConstructors(serverConfig, newTestChain(), zaptest.NewLogger(t),
+	s, err := newServerFromConstructors(serverConfig, fakechain.NewFakeChain(), zaptest.NewLogger(t),
 		newFakeTransp, newFakeConsensus, newTestDiscovery)
 	require.NoError(t, err)
 	return s

pkg/network/server.go

@@ -21,6 +21,7 @@ import (
 	"github.com/nspcc-dev/neo-go/pkg/network/capability"
 	"github.com/nspcc-dev/neo-go/pkg/network/extpool"
 	"github.com/nspcc-dev/neo-go/pkg/network/payload"
+	"github.com/nspcc-dev/neo-go/pkg/services/notary"
 	"github.com/nspcc-dev/neo-go/pkg/services/oracle"
 	"github.com/nspcc-dev/neo-go/pkg/util"
 	"go.uber.org/atomic"
@@ -69,7 +70,8 @@ type (
 		consensus         consensus.Service
 		notaryRequestPool *mempool.Pool
 		extensiblePool    *extpool.Pool
-		NotaryFeer        NotaryFeer
+		notaryFeer        NotaryFeer
+		notaryModule      *notary.Notary
 
 		lock  sync.RWMutex
 		peers map[Peer]bool
@@ -134,13 +136,32 @@ func newServerFromConstructors(config ServerConfig, chain blockchainer.Blockchai
 		transactions:      make(chan *transaction.Transaction, 64),
 	}
 	if chain.P2PSigExtensionsEnabled() {
-		s.NotaryFeer = NewNotaryFeer(chain)
-		s.notaryRequestPool = mempool.New(chain.GetConfig().P2PNotaryRequestPayloadPoolSize, 1)
+		s.notaryFeer = NewNotaryFeer(chain)
+		s.notaryRequestPool = mempool.New(chain.GetConfig().P2PNotaryRequestPayloadPoolSize, 1, chain.GetConfig().P2PNotary.Enabled)
 		chain.RegisterPostBlock(func(bc blockchainer.Blockchainer, txpool *mempool.Pool, _ *block.Block) {
 			s.notaryRequestPool.RemoveStale(func(t *transaction.Transaction) bool {
 				return bc.IsTxStillRelevant(t, txpool, true)
-			}, s.NotaryFeer)
+			}, s.notaryFeer)
 		})
+		if chain.GetConfig().P2PNotary.Enabled {
+			n, err := notary.NewNotary(chain, s.notaryRequestPool, s.log, func(tx *transaction.Transaction) error {
+				r := s.RelayTxn(tx)
+				if r != RelaySucceed {
+					return fmt.Errorf("can't pool notary tx: hash %s, reason: %d", tx.Hash().StringLE(), byte(r))
+				}
+				return nil
+			})
+			if err != nil {
+				return nil, fmt.Errorf("failed to create Notary module: %w", err)
+			}
+			s.notaryModule = n
+			chain.SetNotary(n)
+			chain.RegisterPostBlock(func(bc blockchainer.Blockchainer, pool *mempool.Pool, b *block.Block) {
+				s.notaryModule.PostPersist(bc, pool, b)
+			})
+		}
+	} else if chain.GetConfig().P2PNotary.Enabled {
+		return nil, errors.New("P2PSigExtensions are disabled, but Notary service is enable")
 	}
 	s.bQueue = newBlockQueue(maxBlockBatch, chain, log, func(b *block.Block) {
 		if !s.consensusStarted.Load() {
@@ -235,6 +256,10 @@ func (s *Server) Start(errChan chan error) {
 	if s.oracle != nil {
 		go s.oracle.Run()
 	}
+	if s.notaryModule != nil {
+		s.notaryRequestPool.RunSubscriptions()
+		go s.notaryModule.Run()
+	}
 	go s.relayBlocksLoop()
 	go s.bQueue.run()
 	go s.transport.Accept()
@@ -257,6 +282,10 @@ func (s *Server) Shutdown() {
 	if s.oracle != nil {
 		s.oracle.Shutdown()
 	}
+	if s.notaryModule != nil {
+		s.notaryModule.Stop()
+		s.notaryRequestPool.StopSubscriptions()
+	}
 	close(s.quit)
 }
 
@@ -805,7 +834,7 @@ func (s *Server) handleP2PNotaryRequestCmd(r *payload.P2PNotaryRequest) error {
 
 // verifyAndPoolNotaryRequest verifies NotaryRequest payload and adds it to the payload mempool.
 func (s *Server) verifyAndPoolNotaryRequest(r *payload.P2PNotaryRequest) RelayReason {
-	if err := s.chain.PoolTxWithData(r.FallbackTransaction, r, s.notaryRequestPool, s.NotaryFeer, verifyNotaryRequest); err != nil {
+	if err := s.chain.PoolTxWithData(r.FallbackTransaction, r, s.notaryRequestPool, s.notaryFeer, verifyNotaryRequest); err != nil {
 		switch {
 		case errors.Is(err, core.ErrAlreadyExists):
 			return RelayAlreadyExists
@@ -827,7 +856,8 @@ func verifyNotaryRequest(bc blockchainer.Blockchainer, _ *transaction.Transactio
 	if err := bc.VerifyWitness(payer, r, &r.Witness, bc.GetPolicer().GetMaxVerificationGAS()); err != nil {
 		return fmt.Errorf("bad P2PNotaryRequest payload witness: %w", err)
 	}
-	if r.FallbackTransaction.Sender() != bc.GetNotaryContractScriptHash() {
+	notaryHash := bc.GetNotaryContractScriptHash()
+	if r.FallbackTransaction.Sender() != notaryHash {
 		return errors.New("P2PNotary contract should be a sender of the fallback transaction")
 	}
 	depositExpiration := bc.GetNotaryDepositExpiration(payer)

pkg/network/server_test.go

@@ -9,6 +9,7 @@ import (
 	"testing"
 	"time"
 
+	"github.com/nspcc-dev/neo-go/internal/fakechain"
 	"github.com/nspcc-dev/neo-go/internal/random"
 	"github.com/nspcc-dev/neo-go/pkg/config"
 	"github.com/nspcc-dev/neo-go/pkg/config/netmode"
@@ -47,7 +48,7 @@ func (f *fakeConsensus) OnTransaction(tx *transaction.Transaction)     { f.txs =
 func (f *fakeConsensus) GetPayload(h util.Uint256) *payload.Extensible { panic("implement me") }
 
 func TestNewServer(t *testing.T) {
-	bc := &testChain{}
+	bc := &fakechain.FakeChain{}
 	s, err := newServerFromConstructors(ServerConfig{}, bc, nil, newFakeTransp, newFakeConsensus, newTestDiscovery)
 	require.Error(t, err)
 
@@ -223,7 +224,7 @@ func TestGetBlocksByIndex(t *testing.T) {
 	checkPingRespond(t, 3, 5000, 1+3*payload.MaxHashesCount)
 
 	// Receive some blocks.
-	s.chain.(*testChain).blockheight = 2123
+	s.chain.(*fakechain.FakeChain).Blockheight = 2123
 
 	// Minimum chunk has priority.
 	checkPingRespond(t, 5, 5000, 2124)
@@ -392,7 +393,7 @@ func TestBlock(t *testing.T) {
 	s, shutdown := startTestServer(t)
 	defer shutdown()
 
-	atomic2.StoreUint32(&s.chain.(*testChain).blockheight, 12344)
+	atomic2.StoreUint32(&s.chain.(*fakechain.FakeChain).Blockheight, 12344)
 	require.Equal(t, uint32(12344), s.chain.BlockHeight())
 
 	b := block.New(netmode.UnitTestNet, false)
@@ -405,7 +406,7 @@ func TestConsensus(t *testing.T) {
 	s, shutdown := startTestServer(t)
 	defer shutdown()
 
-	atomic2.StoreUint32(&s.chain.(*testChain).blockheight, 4)
+	atomic2.StoreUint32(&s.chain.(*fakechain.FakeChain).Blockheight, 4)
 	p := newLocalPeer(t, s)
 	p.handshaked = true
 
@@ -417,11 +418,11 @@ func TestConsensus(t *testing.T) {
 		return NewMessage(CMDExtensible, pl)
 	}
 
-	s.chain.(*testChain).verifyWitnessF = func() error { return errors.New("invalid") }
+	s.chain.(*fakechain.FakeChain).VerifyWitnessF = func() error { return errors.New("invalid") }
 	msg := newConsensusMessage(0, s.chain.BlockHeight()+1)
 	require.Error(t, s.handleMessage(p, msg))
 
-	s.chain.(*testChain).verifyWitnessF = func() error { return nil }
+	s.chain.(*fakechain.FakeChain).VerifyWitnessF = func() error { return nil }
 	require.NoError(t, s.handleMessage(p, msg))
 	require.Contains(t, s.consensus.(*fakeConsensus).payloads, msg.Payload.(*payload.Extensible))
 
@@ -471,7 +472,7 @@ func TestTransaction(t *testing.T) {
 	})
 	t.Run("bad", func(t *testing.T) {
 		tx := newDummyTx()
-		s.chain.(*testChain).poolTx = func(*transaction.Transaction) error { return core.ErrInsufficientFunds }
+		s.chain.(*fakechain.FakeChain).PoolTxF = func(*transaction.Transaction) error { return core.ErrInsufficientFunds }
 		s.testHandleMessage(t, nil, CMDTX, tx)
 		for _, ftx := range s.consensus.(*fakeConsensus).txs {
 			require.NotEqual(t, ftx, tx)
@@ -505,19 +506,19 @@ func (s *Server) testHandleGetData(t *testing.T, invType payload.InventoryType,
 func TestGetData(t *testing.T) {
 	s, shutdown := startTestServer(t)
 	defer shutdown()
-	s.chain.(*testChain).utilityTokenBalance = big.NewInt(1000000)
+	s.chain.(*fakechain.FakeChain).UtilityTokenBalance = big.NewInt(1000000)
 
 	t.Run("block", func(t *testing.T) {
 		b := newDummyBlock(2, 0)
 		hs := []util.Uint256{random.Uint256(), b.Hash(), random.Uint256()}
-		s.chain.(*testChain).putBlock(b)
+		s.chain.(*fakechain.FakeChain).PutBlock(b)
 		notFound := []util.Uint256{hs[0], hs[2]}
 		s.testHandleGetData(t, payload.BlockType, hs, notFound, b)
 	})
 	t.Run("transaction", func(t *testing.T) {
 		tx := newDummyTx()
 		hs := []util.Uint256{random.Uint256(), tx.Hash(), random.Uint256()}
-		s.chain.(*testChain).putTx(tx)
+		s.chain.(*fakechain.FakeChain).PutTx(tx)
 		notFound := []util.Uint256{hs[0], hs[2]}
 		s.testHandleGetData(t, payload.TXType, hs, notFound, tx)
 	})
@@ -567,7 +568,7 @@ func initGetBlocksTest(t *testing.T) (*Server, func(), []*block.Block) {
 	var blocks []*block.Block
 	for i := uint32(12); i <= 15; i++ {
 		b := newDummyBlock(i, 3)
-		s.chain.(*testChain).putBlock(b)
+		s.chain.(*fakechain.FakeChain).PutBlock(b)
 		blocks = append(blocks, b)
 	}
 	return s, shutdown, blocks
@@ -633,7 +634,7 @@ func TestGetBlockByIndex(t *testing.T) {
 		s.testHandleMessage(t, p, CMDGetBlockByIndex, &payload.GetBlockByIndex{IndexStart: blocks[0].Index, Count: -1})
 	})
 	t.Run("-1, last header", func(t *testing.T) {
-		s.chain.(*testChain).putHeader(newDummyBlock(16, 2))
+		s.chain.(*fakechain.FakeChain).PutHeader(newDummyBlock(16, 2))
 		actual = nil
 		expected = blocks
 		s.testHandleMessage(t, p, CMDGetBlockByIndex, &payload.GetBlockByIndex{IndexStart: blocks[0].Index, Count: -1})
@@ -683,7 +684,7 @@ func TestGetHeaders(t *testing.T) {
 func TestInv(t *testing.T) {
 	s, shutdown := startTestServer(t)
 	defer shutdown()
-	s.chain.(*testChain).utilityTokenBalance = big.NewInt(10000000)
+	s.chain.(*fakechain.FakeChain).UtilityTokenBalance = big.NewInt(10000000)
 
 	var actual []util.Uint256
 	p := newLocalPeer(t, s)
@@ -696,7 +697,7 @@ func TestInv(t *testing.T) {
 
 	t.Run("blocks", func(t *testing.T) {
 		b := newDummyBlock(10, 3)
-		s.chain.(*testChain).putBlock(b)
+		s.chain.(*fakechain.FakeChain).PutBlock(b)
 		hs := []util.Uint256{random.Uint256(), b.Hash(), random.Uint256()}
 		s.testHandleMessage(t, p, CMDInv, &payload.Inventory{
 			Type:   payload.BlockType,
@@ -706,7 +707,7 @@ func TestInv(t *testing.T) {
 	})
 	t.Run("transaction", func(t *testing.T) {
 		tx := newDummyTx()
-		s.chain.(*testChain).putTx(tx)
+		s.chain.(*fakechain.FakeChain).PutTx(tx)
 		hs := []util.Uint256{random.Uint256(), tx.Hash(), random.Uint256()}
 		s.testHandleMessage(t, p, CMDInv, &payload.Inventory{
 			Type:   payload.TXType,
@@ -716,8 +717,8 @@ func TestInv(t *testing.T) {
 	})
 	t.Run("extensible", func(t *testing.T) {
 		ep := payload.NewExtensible(netmode.UnitTestNet)
-		s.chain.(*testChain).verifyWitnessF = func() error { return nil }
-		ep.ValidBlockEnd = s.chain.(*testChain).BlockHeight() + 1
+		s.chain.(*fakechain.FakeChain).VerifyWitnessF = func() error { return nil }
+		ep.ValidBlockEnd = s.chain.(*fakechain.FakeChain).BlockHeight() + 1
 		ok, err := s.extensiblePool.Add(ep)
 		require.NoError(t, err)
 		require.True(t, ok)
@@ -865,7 +866,7 @@ func TestMemPool(t *testing.T) {
 		}
 	}
 
-	bc := s.chain.(*testChain)
+	bc := s.chain.(*fakechain.FakeChain)
 	expected := make([]util.Uint256, 4)
 	for i := range expected {
 		tx := newDummyTx()
@@ -878,27 +879,27 @@ func TestMemPool(t *testing.T) {
 }
 
 func TestVerifyNotaryRequest(t *testing.T) {
-	bc := newTestChain()
-	bc.maxVerificationGAS = 10
-	bc.notaryContractScriptHash = util.Uint160{1, 2, 3}
+	bc := fakechain.NewFakeChain()
+	bc.MaxVerificationGAS = 10
+	bc.NotaryContractScriptHash = util.Uint160{1, 2, 3}
 	newNotaryRequest := func() *payload.P2PNotaryRequest {
 		return &payload.P2PNotaryRequest{
 			MainTransaction: &transaction.Transaction{Script: []byte{0, 1, 2}},
 			FallbackTransaction: &transaction.Transaction{
 				ValidUntilBlock: 321,
-				Signers:         []transaction.Signer{{Account: bc.notaryContractScriptHash}, {Account: random.Uint160()}},
+				Signers:         []transaction.Signer{{Account: bc.NotaryContractScriptHash}, {Account: random.Uint160()}},
 			},
 			Witness: transaction.Witness{},
 		}
 	}
 
 	t.Run("bad payload witness", func(t *testing.T) {
-		bc.verifyWitnessF = func() error { return errors.New("bad witness") }
+		bc.VerifyWitnessF = func() error { return errors.New("bad witness") }
 		require.Error(t, verifyNotaryRequest(bc, nil, newNotaryRequest()))
 	})
 
 	t.Run("bad fallback sender", func(t *testing.T) {
-		bc.verifyWitnessF = func() error { return nil }
+		bc.VerifyWitnessF = func() error { return nil }
 		r := newNotaryRequest()
 		r.FallbackTransaction.Signers[0] = transaction.Signer{Account: util.Uint160{7, 8, 9}}
 		require.Error(t, verifyNotaryRequest(bc, nil, r))
@@ -906,13 +907,13 @@ func TestVerifyNotaryRequest(t *testing.T) {
 
 	t.Run("expired deposit", func(t *testing.T) {
 		r := newNotaryRequest()
-		bc.notaryDepositExpiration = r.FallbackTransaction.ValidUntilBlock
+		bc.NotaryDepositExpiration = r.FallbackTransaction.ValidUntilBlock
 		require.Error(t, verifyNotaryRequest(bc, nil, r))
 	})
 
 	t.Run("good", func(t *testing.T) {
 		r := newNotaryRequest()
-		bc.notaryDepositExpiration = r.FallbackTransaction.ValidUntilBlock + 1
+		bc.NotaryDepositExpiration = r.FallbackTransaction.ValidUntilBlock + 1
 		require.NoError(t, verifyNotaryRequest(bc, nil, r))
 	})
 }

pkg/services/notary/node.go

@@ -0,0 +1,54 @@
+package notary
+
+import (
+	"github.com/nspcc-dev/neo-go/pkg/crypto/keys"
+	"github.com/nspcc-dev/neo-go/pkg/encoding/address"
+	"github.com/nspcc-dev/neo-go/pkg/util"
+	"github.com/nspcc-dev/neo-go/pkg/wallet"
+	"go.uber.org/zap"
+)
+
+// UpdateNotaryNodes implements Notary interface and updates current notary account.
+func (n *Notary) UpdateNotaryNodes(notaryNodes keys.PublicKeys) {
+	n.accMtx.Lock()
+	defer n.accMtx.Unlock()
+
+	if n.currAccount != nil {
+		for _, node := range notaryNodes {
+			if node.Equal(n.currAccount.PrivateKey().PublicKey()) {
+				return
+			}
+		}
+	}
+
+	var acc *wallet.Account
+	for _, node := range notaryNodes {
+		acc = n.wallet.GetAccount(node.GetScriptHash())
+		if acc != nil {
+			if acc.PrivateKey() != nil {
+				break
+			}
+			err := acc.Decrypt(n.Config.MainCfg.UnlockWallet.Password)
+			if err != nil {
+				n.Config.Log.Warn("can't unlock notary node account",
+					zap.String("address", address.Uint160ToString(acc.Contract.ScriptHash())),
+					zap.Error(err))
+				acc = nil
+			}
+			break
+		}
+	}
+
+	n.currAccount = acc
+	if acc == nil {
+		n.reqMtx.Lock()
+		n.requests = make(map[util.Uint256]*request)
+		n.reqMtx.Unlock()
+	}
+}
+
+func (n *Notary) getAccount() *wallet.Account {
+	n.accMtx.RLock()
+	defer n.accMtx.RUnlock()
+	return n.currAccount
+}

pkg/services/notary/node_test.go

@@ -0,0 +1,71 @@
+package notary
+
+import (
+	"testing"
+
+	"github.com/nspcc-dev/neo-go/internal/fakechain"
+	"github.com/nspcc-dev/neo-go/pkg/config"
+	"github.com/nspcc-dev/neo-go/pkg/core/blockchainer"
+	"github.com/nspcc-dev/neo-go/pkg/core/mempool"
+	"github.com/nspcc-dev/neo-go/pkg/crypto/keys"
+	"github.com/nspcc-dev/neo-go/pkg/wallet"
+	"github.com/stretchr/testify/require"
+	"go.uber.org/zap/zaptest"
+)
+
+func getTestNotary(t *testing.T, bc blockchainer.Blockchainer, walletPath, pass string) (*wallet.Account, *Notary, *mempool.Pool) {
+	bc.(*fakechain.FakeChain).ProtocolConfiguration.P2PNotary = config.P2PNotary{
+		Enabled: true,
+		UnlockWallet: config.Wallet{
+			Path:     walletPath,
+			Password: pass,
+		},
+	}
+	mp := mempool.New(10, 1, true)
+	ntr, err := NewNotary(bc, mp, zaptest.NewLogger(t), nil)
+	require.NoError(t, err)
+
+	w, err := wallet.NewWalletFromFile(walletPath)
+	require.NoError(t, err)
+	require.NoError(t, w.Accounts[0].Decrypt(pass))
+	return w.Accounts[0], ntr, mp
+}
+
+func TestUpdateNotaryNodes(t *testing.T) {
+	bc := fakechain.NewFakeChain()
+	acc, ntr, _ := getTestNotary(t, bc, "./testdata/notary1.json", "one")
+	randomKey, err := keys.NewPrivateKey()
+	require.NoError(t, err)
+	// currAcc is nil before UpdateNotaryNodes call
+	require.Nil(t, ntr.currAccount)
+	// set account for the first time
+	ntr.UpdateNotaryNodes(keys.PublicKeys{acc.PrivateKey().PublicKey()})
+	require.Equal(t, acc, ntr.currAccount)
+
+	t.Run("account is already set", func(t *testing.T) {
+		ntr.UpdateNotaryNodes(keys.PublicKeys{acc.PrivateKey().PublicKey(), randomKey.PublicKey()})
+		require.Equal(t, acc, ntr.currAccount)
+	})
+
+	t.Run("another account from the same wallet", func(t *testing.T) {
+		t.Run("good config password", func(t *testing.T) {
+			w, err := wallet.NewWalletFromFile("./testdata/notary1.json")
+			require.NoError(t, err)
+			require.NoError(t, w.Accounts[1].Decrypt("one"))
+			ntr.UpdateNotaryNodes(keys.PublicKeys{w.Accounts[1].PrivateKey().PublicKey()})
+			require.Equal(t, w.Accounts[1], ntr.currAccount)
+		})
+		t.Run("bad config password", func(t *testing.T) {
+			w, err := wallet.NewWalletFromFile("./testdata/notary1.json")
+			require.NoError(t, err)
+			require.NoError(t, w.Accounts[2].Decrypt("four"))
+			ntr.UpdateNotaryNodes(keys.PublicKeys{w.Accounts[2].PrivateKey().PublicKey()})
+			require.Nil(t, ntr.currAccount)
+		})
+	})
+
+	t.Run("unknown account", func(t *testing.T) {
+		ntr.UpdateNotaryNodes(keys.PublicKeys{randomKey.PublicKey()})
+		require.Nil(t, ntr.currAccount)
+	})
+}

pkg/services/notary/notary.go

@@ -0,0 +1,394 @@
+package notary
+
+import (
+	"bytes"
+	"crypto/elliptic"
+	"encoding/hex"
+	"errors"
+	"fmt"
+	"sync"
+
+	"github.com/nspcc-dev/neo-go/pkg/config"
+	"github.com/nspcc-dev/neo-go/pkg/core/block"
+	"github.com/nspcc-dev/neo-go/pkg/core/blockchainer"
+	"github.com/nspcc-dev/neo-go/pkg/core/mempool"
+	"github.com/nspcc-dev/neo-go/pkg/core/transaction"
+	"github.com/nspcc-dev/neo-go/pkg/crypto/hash"
+	"github.com/nspcc-dev/neo-go/pkg/crypto/keys"
+	"github.com/nspcc-dev/neo-go/pkg/network/payload"
+	"github.com/nspcc-dev/neo-go/pkg/util"
+	"github.com/nspcc-dev/neo-go/pkg/vm"
+	"github.com/nspcc-dev/neo-go/pkg/vm/opcode"
+	"github.com/nspcc-dev/neo-go/pkg/wallet"
+	"go.uber.org/zap"
+)
+
+type (
+	// Notary represents Notary module.
+	Notary struct {
+		Config Config
+
+		// onTransaction is a callback for completed transactions (mains or fallbacks) sending.
+		onTransaction func(tx *transaction.Transaction) error
+
+		// reqMtx protects requests list.
+		reqMtx sync.RWMutex
+		// requests represents the map of main transactions which needs to be completed
+		// with the associated fallback transactions grouped by the main transaction hash
+		requests map[util.Uint256]*request
+
+		// accMtx protects account.
+		accMtx      sync.RWMutex
+		currAccount *wallet.Account
+		wallet      *wallet.Wallet
+
+		mp *mempool.Pool
+		// requests channel
+		reqCh  chan mempool.Event
+		stopCh chan struct{}
+	}
+
+	// Config represents external configuration for Notary module.
+	Config struct {
+		MainCfg config.P2PNotary
+		Chain   blockchainer.Blockchainer
+		Log     *zap.Logger
+	}
+)
+
+// request represents Notary service request.
+type request struct {
+	typ RequestType
+	// isSent indicates whether main transaction was successfully sent to the network.
+	isSent bool
+	main   *transaction.Transaction
+	// minNotValidBefore is the minimum NVB value among fallbacks transactions.
+	// We stop trying to send mainTx to the network if the chain reaches minNotValidBefore height.
+	minNotValidBefore uint32
+	fallbacks         []*transaction.Transaction
+	// nSigs is the number of signatures to be collected.
+	// nSigs == nKeys for standard signature request;
+	// nSigs <= nKeys for multisignature request.
+	// nSigs is 0 when all received requests were invalid, so check request.typ before access to nSigs.
+	nSigs uint8
+	// nSigsCollected is the number of already collected signatures
+	nSigsCollected uint8
+
+	// sigs is a map of partial multisig invocation scripts [opcode.PUSHDATA1+64+signatureBytes] grouped by public keys
+	sigs map[*keys.PublicKey][]byte
+}
+
+// NewNotary returns new Notary module.
+func NewNotary(bc blockchainer.Blockchainer, mp *mempool.Pool, log *zap.Logger, onTransaction func(tx *transaction.Transaction) error) (*Notary, error) {
+	cfg := bc.GetConfig().P2PNotary
+	w := cfg.UnlockWallet
+	wallet, err := wallet.NewWalletFromFile(w.Path)
+	if err != nil {
+		return nil, err
+	}
+
+	haveAccount := false
+	for _, acc := range wallet.Accounts {
+		if err := acc.Decrypt(w.Password); err == nil {
+			haveAccount = true
+			break
+		}
+	}
+	if !haveAccount {
+		return nil, errors.New("no wallet account could be unlocked")
+	}
+
+	return &Notary{
+		requests: make(map[util.Uint256]*request),
+		Config: Config{
+			MainCfg: cfg,
+			Chain:   bc,
+			Log:     log,
+		},
+		wallet:        wallet,
+		onTransaction: onTransaction,
+		mp:            mp,
+		reqCh:         make(chan mempool.Event),
+		stopCh:        make(chan struct{}),
+	}, nil
+}
+
+// Run runs Notary module and should be called in a separate goroutine.
+func (n *Notary) Run() {
+	n.mp.SubscribeForTransactions(n.reqCh)
+	for {
+		select {
+		case <-n.stopCh:
+			n.mp.UnsubscribeFromTransactions(n.reqCh)
+			return
+		case event := <-n.reqCh:
+			if req, ok := event.Data.(*payload.P2PNotaryRequest); ok {
+				switch event.Type {
+				case mempool.TransactionAdded:
+					n.OnNewRequest(req)
+				case mempool.TransactionRemoved:
+					n.OnRequestRemoval(req)
+				}
+			}
+		}
+	}
+}
+
+// Stop shutdowns Notary module.
+func (n *Notary) Stop() {
+	close(n.stopCh)
+}
+
+// OnNewRequest is a callback method which is called after new notary request is added to the notary request pool.
+func (n *Notary) OnNewRequest(payload *payload.P2PNotaryRequest) {
+	if n.getAccount() == nil {
+		return
+	}
+
+	nvbFallback := payload.FallbackTransaction.GetAttributes(transaction.NotValidBeforeT)[0].Value.(*transaction.NotValidBefore).Height
+	nKeys := payload.MainTransaction.GetAttributes(transaction.NotaryAssistedT)[0].Value.(*transaction.NotaryAssisted).NKeys
+	typ, nSigs, pubs, validationErr := n.verifyIncompleteWitnesses(payload.MainTransaction, nKeys)
+	n.reqMtx.Lock()
+	defer n.reqMtx.Unlock()
+	r, exists := n.requests[payload.MainTransaction.Hash()]
+	if exists {
+		for _, fb := range r.fallbacks {
+			if fb.Hash().Equals(payload.FallbackTransaction.Hash()) {
+				return // then we already have processed this request
+			}
+		}
+		if nvbFallback < r.minNotValidBefore {
+			r.minNotValidBefore = nvbFallback
+		}
+		if r.typ == Unknown && validationErr == nil {
+			r.typ = typ
+			r.nSigs = nSigs
+		}
+	} else {
+		r = &request{
+			nSigs:             nSigs,
+			main:              payload.MainTransaction,
+			typ:               typ,
+			minNotValidBefore: nvbFallback,
+		}
+		n.requests[payload.MainTransaction.Hash()] = r
+	}
+	r.fallbacks = append(r.fallbacks, payload.FallbackTransaction)
+	if exists && r.typ != Unknown && r.nSigsCollected >= r.nSigs { // already collected sufficient number of signatures to complete main transaction
+		return
+	}
+	if validationErr == nil {
+	loop:
+		for i, w := range payload.MainTransaction.Scripts {
+			if payload.MainTransaction.Signers[i].Account.Equals(n.Config.Chain.GetNotaryContractScriptHash()) {
+				continue
+			}
+			if len(w.InvocationScript) != 0 && len(w.VerificationScript) != 0 {
+				switch r.typ {
+				case Signature:
+					if !exists {
+						r.nSigsCollected++
+					} else if len(r.main.Scripts[i].InvocationScript) == 0 { // need this check because signature can already be added (consider receiving the same payload multiple times)
+						r.main.Scripts[i] = w
+						r.nSigsCollected++
+					}
+					if r.nSigsCollected == r.nSigs {
+						break loop
+					}
+				case MultiSignature:
+					if r.sigs == nil {
+						r.sigs = make(map[*keys.PublicKey][]byte)
+					}
+
+					hash := r.main.GetSignedHash().BytesBE()
+					for _, pub := range pubs {
+						if r.sigs[pub] != nil {
+							continue // signature for this pub has already been added
+						}
+						if pub.Verify(w.InvocationScript[2:], hash) { // then pub is the owner of the signature
+							r.sigs[pub] = w.InvocationScript
+							r.nSigsCollected++
+							if r.nSigsCollected == r.nSigs {
+								var invScript []byte
+								for j := range pubs {
+									if sig, ok := r.sigs[pubs[j]]; ok {
+										invScript = append(invScript, sig...)
+									}
+								}
+								r.main.Scripts[i].InvocationScript = invScript
+							}
+							break loop
+						}
+					}
+					// pubKey was not found for the signature i.e. signature is bad - we're OK with that, let the fallback TX to be added
+					break loop // only one multisignature is allowed
+				}
+			}
+		}
+	}
+	if r.typ != Unknown && r.nSigsCollected == nSigs && r.minNotValidBefore > n.Config.Chain.BlockHeight() {
+		if err := n.finalize(r.main); err != nil {
+			n.Config.Log.Error("failed to finalize main transaction", zap.Error(err))
+		} else {
+			r.isSent = true
+		}
+	}
+}
+
+// OnRequestRemoval is a callback which is called after fallback transaction is removed
+// from the notary payload pool due to expiration, main tx appliance or any other reason.
+func (n *Notary) OnRequestRemoval(pld *payload.P2PNotaryRequest) {
+	if n.getAccount() == nil {
+		return
+	}
+
+	n.reqMtx.Lock()
+	defer n.reqMtx.Unlock()
+	r, ok := n.requests[pld.MainTransaction.Hash()]
+	if !ok {
+		return
+	}
+	for i, fb := range r.fallbacks {
+		if fb.Hash().Equals(pld.FallbackTransaction.Hash()) {
+			r.fallbacks = append(r.fallbacks[:i], r.fallbacks[i+1:]...)
+			break
+		}
+	}
+	if len(r.fallbacks) == 0 {
+		delete(n.requests, r.main.Hash())
+	}
+}
+
+// PostPersist is a callback which is called after new block is persisted.
+func (n *Notary) PostPersist(bc blockchainer.Blockchainer, pool *mempool.Pool, b *block.Block) {
+	if n.getAccount() == nil {
+		return
+	}
+
+	n.reqMtx.Lock()
+	defer n.reqMtx.Unlock()
+	for h, r := range n.requests {
+		if !r.isSent && r.typ != Unknown && r.nSigs == r.nSigsCollected && r.minNotValidBefore > bc.BlockHeight() {
+			if err := n.finalize(r.main); err != nil {
+				n.Config.Log.Error("failed to finalize main transaction", zap.Error(err))
+			} else {
+				r.isSent = true
+			}
+			continue
+		}
+		if r.minNotValidBefore <= bc.BlockHeight() { // then at least one of the fallbacks can already be sent.
+			newFallbacks := r.fallbacks[:0]
+			for _, fb := range r.fallbacks {
+				if nvb := fb.GetAttributes(transaction.NotValidBeforeT)[0].Value.(*transaction.NotValidBefore).Height; nvb <= bc.BlockHeight() {
+					if err := n.finalize(fb); err != nil {
+						newFallbacks = append(newFallbacks, fb) // wait for the next block to resend them
+					}
+				} else {
+					newFallbacks = append(newFallbacks, fb)
+				}
+			}
+			if len(newFallbacks) == 0 {
+				delete(n.requests, h)
+			} else {
+				r.fallbacks = newFallbacks
+			}
+		}
+	}
+}
+
+// finalize adds missing Notary witnesses to the transaction (main or fallback) and pushes it to the network.
+func (n *Notary) finalize(tx *transaction.Transaction) error {
+	acc := n.getAccount()
+	if acc == nil {
+		panic(errors.New("no available Notary account")) // unreachable code, because all callers of `finalize` check that acc != nil
+	}
+	notaryWitness := transaction.Witness{
+		InvocationScript:   append([]byte{byte(opcode.PUSHDATA1), 64}, acc.PrivateKey().Sign(tx.GetSignedPart())...),
+		VerificationScript: []byte{},
+	}
+	for i, signer := range tx.Signers {
+		if signer.Account == n.Config.Chain.GetNotaryContractScriptHash() {
+			tx.Scripts[i] = notaryWitness
+			break
+		}
+	}
+	return n.onTransaction(tx)
+}
+
+// verifyIncompleteWitnesses checks that tx either doesn't have all witnesses attached (in this case none of them
+// can be multisignature), or it only has a partial multisignature. It returns the request type (sig/multisig), the
+// number of signatures to be collected, sorted public keys (for multisig request only) and an error.
+func (n *Notary) verifyIncompleteWitnesses(tx *transaction.Transaction, nKeys uint8) (RequestType, uint8, keys.PublicKeys, error) {
+	var (
+		typ         RequestType
+		nSigs       int
+		nKeysActual uint8
+		pubsBytes   [][]byte
+		pubs        keys.PublicKeys
+		ok          bool
+	)
+	if len(tx.Signers) < 2 {
+		return Unknown, 0, nil, errors.New("transaction should have at least 2 signers")
+	}
+	if len(tx.Signers) != len(tx.Scripts) {
+		return Unknown, 0, nil, fmt.Errorf("transaction should have %d witnesses attached (completed + dummy)", len(tx.Signers))
+	}
+	if !tx.HasSigner(n.Config.Chain.GetNotaryContractScriptHash()) {
+		return Unknown, 0, nil, fmt.Errorf("P2PNotary contract should be a signer of the transaction")
+	}
+
+	for i, w := range tx.Scripts {
+		// do not check witness for Notary contract -- it will be replaced by proper witness in any case.
+		if tx.Signers[i].Account == n.Config.Chain.GetNotaryContractScriptHash() {
+			continue
+		}
+		if len(w.VerificationScript) == 0 {
+			// then it's a contract verification (can be combined with anything)
+			continue
+		}
+		if !tx.Signers[i].Account.Equals(hash.Hash160(w.VerificationScript)) { // https://github.com/nspcc-dev/neo-go/pull/1658#discussion_r564265987
+			return Unknown, 0, nil, fmt.Errorf("transaction should have valid verification script for signer #%d", i)
+		}
+		if nSigs, pubsBytes, ok = vm.ParseMultiSigContract(w.VerificationScript); ok {
+			if typ == Signature || typ == MultiSignature {
+				return Unknown, 0, nil, fmt.Errorf("bad type of witness #%d: only one multisignature witness is allowed", i)
+			}
+			typ = MultiSignature
+			nKeysActual = uint8(len(pubsBytes))
+			if len(w.InvocationScript) != 66 || !bytes.HasPrefix(w.InvocationScript, []byte{byte(opcode.PUSHDATA1), 64}) {
+				return Unknown, 0, nil, fmt.Errorf("multisignature invocation script should have length = 66 and be of the form [PUSHDATA1, 64, signatureBytes...]")
+			}
+			continue
+		}
+		if vm.IsSignatureContract(w.VerificationScript) {
+			if typ == MultiSignature {
+				return Unknown, 0, nil, fmt.Errorf("bad type of witness #%d: multisignature witness can not be combined with other witnesses", i)
+			}
+			typ = Signature
+			nSigs = int(nKeys)
+			continue
+		}
+		return Unknown, 0, nil, fmt.Errorf("unable to define the type of witness #%d", i)
+	}
+	switch typ {
+	case Signature:
+		if len(tx.Scripts) < int(nKeys+1) {
+			return Unknown, 0, nil, fmt.Errorf("transaction should comtain at least %d witnesses (1 for notary + nKeys)", nKeys+1)
+		}
+	case MultiSignature:
+		if nKeysActual != nKeys {
+			return Unknown, 0, nil, fmt.Errorf("bad m out of n partial multisignature witness: expected n = %d, got n = %d", nKeys, nKeysActual)
+		}
+		pubs = make(keys.PublicKeys, len(pubsBytes))
+		for i, pBytes := range pubsBytes {
+			pub, err := keys.NewPublicKeyFromBytes(pBytes, elliptic.P256())
+			if err != nil {
+				return Unknown, 0, nil, fmt.Errorf("invalid bytes of #%d public key: %s", i, hex.EncodeToString(pBytes))
+			}
+			pubs[i] = pub
+		}
+	default:
+		return Unknown, 0, nil, errors.New("unexpected Notary request type")
+	}
+	return typ, uint8(nSigs), pubs, nil
+}

pkg/services/notary/notary_test.go

@@ -0,0 +1,427 @@
+package notary
+
+import (
+	"testing"
+
+	"github.com/nspcc-dev/neo-go/internal/fakechain"
+	"github.com/nspcc-dev/neo-go/pkg/config"
+	"github.com/nspcc-dev/neo-go/pkg/core/mempool"
+	"github.com/nspcc-dev/neo-go/pkg/core/transaction"
+	"github.com/nspcc-dev/neo-go/pkg/crypto/hash"
+	"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/opcode"
+	"github.com/stretchr/testify/assert"
+	"github.com/stretchr/testify/require"
+	"go.uber.org/zap/zaptest"
+)
+
+func TestWallet(t *testing.T) {
+	bc := fakechain.NewFakeChain()
+
+	t.Run("unexisting wallet", func(t *testing.T) {
+		bc.ProtocolConfiguration.P2PNotary = config.P2PNotary{
+			Enabled: true,
+			UnlockWallet: config.Wallet{
+				Path:     "./testdata/does_not_exists.json",
+				Password: "one",
+			},
+		}
+		_, err := NewNotary(bc, mempool.New(1, 1, true), zaptest.NewLogger(t), nil)
+		require.Error(t, err)
+	})
+
+	t.Run("bad password", func(t *testing.T) {
+		bc.ProtocolConfiguration.P2PNotary = config.P2PNotary{
+			Enabled: true,
+			UnlockWallet: config.Wallet{
+				Path:     "./testdata/notary1.json",
+				Password: "invalid",
+			},
+		}
+		_, err := NewNotary(bc, mempool.New(1, 1, true), zaptest.NewLogger(t), nil)
+		require.Error(t, err)
+	})
+
+	t.Run("good", func(t *testing.T) {
+		bc.ProtocolConfiguration.P2PNotary = config.P2PNotary{
+			Enabled: true,
+			UnlockWallet: config.Wallet{
+				Path:     "./testdata/notary1.json",
+				Password: "one",
+			},
+		}
+		_, err := NewNotary(bc, mempool.New(1, 1, true), zaptest.NewLogger(t), nil)
+		require.NoError(t, err)
+	})
+}
+
+func TestVerifyIncompleteRequest(t *testing.T) {
+	bc := fakechain.NewFakeChain()
+	notaryContractHash := util.Uint160{1, 2, 3}
+	bc.NotaryContractScriptHash = notaryContractHash
+	_, ntr, _ := getTestNotary(t, bc, "./testdata/notary1.json", "one")
+	sig := append([]byte{byte(opcode.PUSHDATA1), 64}, make([]byte, 64)...) // we're not interested in signature correctness
+	acc1, _ := keys.NewPrivateKey()
+	acc2, _ := keys.NewPrivateKey()
+	acc3, _ := keys.NewPrivateKey()
+	sigScript1 := acc1.PublicKey().GetVerificationScript()
+	sigScript2 := acc2.PublicKey().GetVerificationScript()
+	sigScript3 := acc3.PublicKey().GetVerificationScript()
+	multisigScript1, err := smartcontract.CreateMultiSigRedeemScript(1, keys.PublicKeys{acc1.PublicKey(), acc2.PublicKey(), acc3.PublicKey()})
+	require.NoError(t, err)
+	multisigScriptHash1 := hash.Hash160(multisigScript1)
+	multisigScript2, err := smartcontract.CreateMultiSigRedeemScript(2, keys.PublicKeys{acc1.PublicKey(), acc2.PublicKey(), acc3.PublicKey()})
+	require.NoError(t, err)
+	multisigScriptHash2 := hash.Hash160(multisigScript2)
+
+	checkErr := func(t *testing.T, tx *transaction.Transaction, nKeys uint8) {
+		typ, nSigs, pubs, err := ntr.verifyIncompleteWitnesses(tx, nKeys)
+		require.Error(t, err)
+		require.Equal(t, Unknown, typ)
+		require.Equal(t, uint8(0), nSigs)
+		require.Nil(t, pubs)
+	}
+
+	errCases := map[string]struct {
+		tx    *transaction.Transaction
+		nKeys uint8
+	}{
+		"not enough signers": {
+			tx: &transaction.Transaction{
+				Signers: []transaction.Signer{{Account: notaryContractHash}},
+				Scripts: []transaction.Witness{{}},
+			},
+		},
+		"signers count and witnesses count mismatch": {
+			tx: &transaction.Transaction{
+				Signers: []transaction.Signer{{Account: notaryContractHash}, {}},
+				Scripts: []transaction.Witness{{}, {}, {}},
+			},
+		},
+		"missing Notary witness": {
+			tx: &transaction.Transaction{
+				Signers: []transaction.Signer{{Account: acc1.GetScriptHash()}, {Account: acc2.GetScriptHash()}},
+				Scripts: []transaction.Witness{{}, {}},
+			},
+		},
+		"unknown witness type": {
+			tx: &transaction.Transaction{
+				Signers: []transaction.Signer{{Account: acc1.PublicKey().GetScriptHash()}, {Account: notaryContractHash}},
+				Scripts: []transaction.Witness{
+					{},
+					{},
+				},
+			},
+		},
+		"bad verification script": {
+			tx: &transaction.Transaction{
+				Signers: []transaction.Signer{{Account: acc1.PublicKey().GetScriptHash()}, {Account: notaryContractHash}},
+				Scripts: []transaction.Witness{
+					{
+						InvocationScript:   []byte{},
+						VerificationScript: []byte{1, 2, 3},
+					},
+					{},
+				},
+			},
+		},
+		"several multisig witnesses": {
+			tx: &transaction.Transaction{
+				Signers: []transaction.Signer{{Account: multisigScriptHash1}, {Account: multisigScriptHash2}, {Account: notaryContractHash}},
+				Scripts: []transaction.Witness{
+					{
+						InvocationScript:   sig,
+						VerificationScript: multisigScript1,
+					},
+					{
+						InvocationScript:   sig,
+						VerificationScript: multisigScript2,
+					},
+					{},
+				},
+			},
+			nKeys: 2,
+		},
+		"multisig + sig": {
+			tx: &transaction.Transaction{
+				Signers: []transaction.Signer{{Account: multisigScriptHash1}, {Account: acc1.PublicKey().GetScriptHash()}, {Account: notaryContractHash}},
+				Scripts: []transaction.Witness{
+					{
+						InvocationScript:   sig,
+						VerificationScript: multisigScript1,
+					},
+					{
+						InvocationScript:   sig,
+						VerificationScript: sigScript1,
+					},
+					{},
+				},
+			},
+			nKeys: 2,
+		},
+		"sig + multisig": {
+			tx: &transaction.Transaction{
+				Signers: []transaction.Signer{{Account: acc1.PublicKey().GetScriptHash()}, {Account: multisigScriptHash1}, {Account: notaryContractHash}},
+				Scripts: []transaction.Witness{
+					{
+						InvocationScript:   sig,
+						VerificationScript: sigScript1,
+					},
+					{
+						InvocationScript:   sig,
+						VerificationScript: multisigScript1,
+					},
+					{},
+				},
+			},
+			nKeys: 2,
+		},
+		"empty multisig + sig": {
+			tx: &transaction.Transaction{
+				Signers: []transaction.Signer{{Account: multisigScriptHash1}, {Account: acc1.PublicKey().GetScriptHash()}, {Account: notaryContractHash}},
+				Scripts: []transaction.Witness{
+					{
+						InvocationScript:   []byte{},
+						VerificationScript: multisigScript1,
+					},
+					{
+						InvocationScript:   sig,
+						VerificationScript: sigScript1,
+					},
+					{},
+				},
+			},
+			nKeys: 2,
+		},
+		"sig + empty multisig": {
+			tx: &transaction.Transaction{
+				Signers: []transaction.Signer{{Account: acc1.PublicKey().GetScriptHash()}, {Account: multisigScriptHash1}, {Account: notaryContractHash}},
+				Scripts: []transaction.Witness{
+					{
+						InvocationScript:   sig,
+						VerificationScript: sigScript1,
+					},
+					{
+						InvocationScript:   []byte{},
+						VerificationScript: multisigScript1,
+					},
+					{},
+				},
+			},
+			nKeys: 2,
+		},
+		"multisig + empty sig": {
+			tx: &transaction.Transaction{
+				Signers: []transaction.Signer{{Account: multisigScriptHash1}, {Account: acc1.PublicKey().GetScriptHash()}, {Account: notaryContractHash}},
+				Scripts: []transaction.Witness{
+					{
+						InvocationScript:   sig,
+						VerificationScript: multisigScript1,
+					},
+					{
+						InvocationScript:   []byte{},
+						VerificationScript: sigScript1,
+					},
+					{},
+				},
+			},
+			nKeys: 2,
+		},
+		"empty sig + multisig": {
+			tx: &transaction.Transaction{
+				Signers: []transaction.Signer{{Account: acc1.PublicKey().GetScriptHash()}, {Account: multisigScriptHash1}, {Account: notaryContractHash}},
+				Scripts: []transaction.Witness{
+					{
+						InvocationScript:   []byte{},
+						VerificationScript: sigScript1,
+					},
+					{
+						InvocationScript:   sig,
+						VerificationScript: multisigScript1,
+					},
+					{},
+				},
+			},
+			nKeys: 2,
+		},
+		"sig: bad nKeys": {
+			tx: &transaction.Transaction{
+				Signers: []transaction.Signer{{Account: acc1.PublicKey().GetScriptHash()}, {Account: acc2.PublicKey().GetScriptHash()}, {Account: notaryContractHash}},
+				Scripts: []transaction.Witness{
+					{
+						InvocationScript:   sig,
+						VerificationScript: sigScript1,
+					},
+					{
+						InvocationScript:   sig,
+						VerificationScript: sigScript2,
+					},
+					{},
+				},
+			},
+			nKeys: 3,
+		},
+		"multisig: bad witnesses count": {
+			tx: &transaction.Transaction{
+				Signers: []transaction.Signer{{Account: multisigScriptHash1}, {Account: notaryContractHash}},
+				Scripts: []transaction.Witness{
+					{
+						InvocationScript:   sig,
+						VerificationScript: multisigScript1,
+					},
+				},
+			},
+			nKeys: 2,
+		},
+		"multisig: bad nKeys": {
+			tx: &transaction.Transaction{
+				Signers: []transaction.Signer{{Account: multisigScriptHash1}, {Account: notaryContractHash}},
+				Scripts: []transaction.Witness{
+					{
+						InvocationScript:   sig,
+						VerificationScript: multisigScript1,
+					},
+					{},
+				},
+			},
+			nKeys: 2,
+		},
+	}
+
+	for name, errCase := range errCases {
+		t.Run(name, func(t *testing.T) {
+			checkErr(t, errCase.tx, errCase.nKeys)
+		})
+	}
+
+	testCases := map[string]struct {
+		tx            *transaction.Transaction
+		nKeys         uint8
+		expectedType  RequestType
+		expectedNSigs uint8
+		expectedPubs  keys.PublicKeys
+	}{
+		"single sig": {
+			tx: &transaction.Transaction{
+				Signers: []transaction.Signer{{Account: acc1.GetScriptHash()}, {Account: notaryContractHash}},
+				Scripts: []transaction.Witness{
+					{
+						InvocationScript:   sig,
+						VerificationScript: sigScript1,
+					},
+					{},
+				},
+			},
+			nKeys:         1,
+			expectedType:  Signature,
+			expectedNSigs: 1,
+		},
+		"multiple sig": {
+			tx: &transaction.Transaction{
+				Signers: []transaction.Signer{{Account: acc1.GetScriptHash()}, {Account: acc2.GetScriptHash()}, {Account: acc3.GetScriptHash()}, {Account: notaryContractHash}},
+				Scripts: []transaction.Witness{
+					{
+						InvocationScript:   sig,
+						VerificationScript: sigScript1,
+					},
+					{
+						InvocationScript:   []byte{},
+						VerificationScript: []byte{},
+					},
+					{
+						InvocationScript:   sig,
+						VerificationScript: sigScript3,
+					},
+					{},
+				},
+			},
+			nKeys:         3,
+			expectedType:  Signature,
+			expectedNSigs: 3,
+		},
+		"multisig 1 out of 3": {
+			tx: &transaction.Transaction{
+				Signers: []transaction.Signer{{Account: multisigScriptHash1}, {Account: notaryContractHash}},
+				Scripts: []transaction.Witness{
+					{
+						InvocationScript:   sig,
+						VerificationScript: multisigScript1,
+					},
+					{},
+				},
+			},
+			nKeys:         3,
+			expectedType:  MultiSignature,
+			expectedNSigs: 1,
+			expectedPubs:  keys.PublicKeys{acc1.PublicKey(), acc2.PublicKey(), acc3.PublicKey()},
+		},
+		"multisig 2 out of 3": {
+			tx: &transaction.Transaction{
+				Signers: []transaction.Signer{{Account: multisigScriptHash2}, {Account: notaryContractHash}},
+				Scripts: []transaction.Witness{
+					{
+						InvocationScript:   sig,
+						VerificationScript: multisigScript2,
+					},
+					{},
+				},
+			},
+			nKeys:         3,
+			expectedType:  MultiSignature,
+			expectedNSigs: 2,
+			expectedPubs:  keys.PublicKeys{acc1.PublicKey(), acc2.PublicKey(), acc3.PublicKey()},
+		},
+		"empty + multisig": {
+			tx: &transaction.Transaction{
+				Signers: []transaction.Signer{{Account: acc1.PublicKey().GetScriptHash()}, {Account: multisigScriptHash1}, {Account: notaryContractHash}},
+				Scripts: []transaction.Witness{
+					{
+						InvocationScript:   []byte{},
+						VerificationScript: []byte{},
+					},
+					{
+						InvocationScript:   sig,
+						VerificationScript: multisigScript1,
+					},
+					{},
+				},
+			},
+			nKeys:         3,
+			expectedType:  MultiSignature,
+			expectedNSigs: 1,
+			expectedPubs:  keys.PublicKeys{acc1.PublicKey(), acc2.PublicKey(), acc3.PublicKey()},
+		},
+		"multisig + empty": {
+			tx: &transaction.Transaction{
+				Signers: []transaction.Signer{{Account: multisigScriptHash1}, {Account: acc1.PublicKey().GetScriptHash()}, {Account: notaryContractHash}},
+				Scripts: []transaction.Witness{
+					{
+						InvocationScript:   sig,
+						VerificationScript: multisigScript1,
+					},
+					{
+						InvocationScript:   []byte{},
+						VerificationScript: []byte{},
+					},
+					{},
+				},
+			},
+			nKeys:         3,
+			expectedType:  MultiSignature,
+			expectedNSigs: 1,
+			expectedPubs:  keys.PublicKeys{acc1.PublicKey(), acc2.PublicKey(), acc3.PublicKey()},
+		},
+	}
+
+	for name, testCase := range testCases {
+		t.Run(name, func(t *testing.T) {
+			typ, nSigs, pubs, err := ntr.verifyIncompleteWitnesses(testCase.tx, testCase.nKeys)
+			require.NoError(t, err)
+			assert.Equal(t, testCase.expectedType, typ)
+			assert.Equal(t, testCase.expectedNSigs, nSigs)
+			assert.ElementsMatch(t, testCase.expectedPubs, pubs)
+		})
+	}
+}

pkg/services/notary/request_type.go

@@ -0,0 +1,13 @@
+package notary
+
+// RequestType represents the type of Notary request.
+type RequestType byte
+
+const (
+	// Unknown represents unknown request type which means that main tx witnesses are invalid.
+	Unknown RequestType = 0x00
+	// Signature represents standard single signature request type.
+	Signature RequestType = 0x01
+	// MultiSignature represents m out of n multisignature request type.
+	MultiSignature RequestType = 0x02
+)

pkg/services/notary/testdata/notary1.json

@@ -0,0 +1 @@
+{"version":"3.0","accounts":[{"address":"NSbjd7dSePTZ6QpADAuM5722QpBmL5124W","key":"6PYVWTfkNCYvyQhyFLHH5dyRyT6jSi8u8Z8kn122PACfsDWi4QgkGm8FyW","label":"NotaryNode1","contract":{"script":"DCEDm5PmbOfVPmYXTSVW903XnOhhNBTsF9oDlVYusIH/ui0LQZVEDXg=","parameters":[{"name":"parameter0","type":"Signature"}],"deployed":false},"lock":false,"isdefault":false},{"address":"NisSvmSd2Lp28tjr8EqCZB5ahHDvBExo2j","key":"6PYLvgnZNwhiiZPiSCw3B3bHSFwbSXgh3MkGt4gL69MD8Sw7LMnuUgM9KQ","label":"three","contract":{"script":"DCEDHRWEIGXHCwUU2Fc7B0qrYPezXR0sfdEduRExyzIKVC8LQZVEDXg=","parameters":[{"name":"parameter0","type":"Signature"}],"deployed":false},"lock":false,"isdefault":false},{"address":"NRCCdGifyUWKnFotZhcgKpmxhhVJSJb94r","key":"6PYKXkuJ7G6bTj62bjy8fsBLF5okYNdAEBhKPCv8nmcALCtk2yPtBo835p","label":"four","contract":{"script":"DCECmUfs/gqKHd3AdJm5+Ev6zkubV8pP8DZzgu8+t5WdphILQZVEDXg=","parameters":[{"name":"parameter0","type":"Signature"}],"deployed":false},"lock":false,"isdefault":false}],"scrypt":{"n":16384,"r":8,"p":8},"extra":{"Tokens":null}}

pkg/services/notary/testdata/notary2.json

@@ -0,0 +1 @@
+{"version":"3.0","accounts":[{"address":"NfFcJvWcHe8SSS92hNZhyQUJ6cg3pb36Tf","key":"6PYU2QoD52Xt9Z6QmNGUJWn89qUD1W6QqAL4Y8nfTWtTKvmVpQh8wsH6qY","label":"NotaryNode2","contract":{"script":"DCECIcKj0GFdv4b1NZrw9X6zLNLWzmNKAxtw6olIMZxpPRQLQZVEDXg=","parameters":[{"name":"parameter0","type":"Signature"}],"deployed":false},"lock":false,"isdefault":false}],"scrypt":{"n":16384,"r":8,"p":8},"extra":{"Tokens":null}}