[#74] neofs: Check alphabet multi signature and don't use ballots

Ballots are inefficient to collect invocations of contract methods.
Instead contract can check multi signature collected outside of the
contract, e.g. with notary service.

Signed-off-by: Alex Vanin <alexey@nspcc.ru>

neofs/neofs_contract.go

@@ -36,7 +36,6 @@ import (
 	"github.com/nspcc-dev/neo-go/pkg/interop"
 	"github.com/nspcc-dev/neo-go/pkg/interop/contract"
 	"github.com/nspcc-dev/neo-go/pkg/interop/iterator"
-	"github.com/nspcc-dev/neo-go/pkg/interop/native/crypto"
 	"github.com/nspcc-dev/neo-go/pkg/interop/native/gas"
 	"github.com/nspcc-dev/neo-go/pkg/interop/native/management"
 	"github.com/nspcc-dev/neo-go/pkg/interop/native/std"
@@ -98,7 +97,6 @@ func Init(owner interop.PublicKey, args []interop.PublicKey) bool {
 
 	// initialize all storage slices
 	common.SetSerialized(ctx, alphabetKey, irList)
-	common.InitVote(ctx)
 	common.SetSerialized(ctx, candidatesKey, []common.IRNode{})
 
 	storage.Put(ctx, common.OwnerKey, owner)
@@ -145,22 +143,9 @@ func InnerRingCandidates() []common.IRNode {
 func InnerRingCandidateRemove(key interop.PublicKey) bool {
 	ctx := storage.GetContext()
 
-	if !runtime.CheckWitness(key) {
+	multiaddr := AlphabetAddress()
-		alphabet := getNodes(ctx, alphabetKey)
+	if !runtime.CheckWitness(key) && !runtime.CheckWitness(multiaddr) {
-		threshold := len(alphabet)*2/3 + 1
+		panic("irCandidateRemove: this method must be invoked by candidate or alphabet")
-
-		nodeKey := common.InnerRingInvoker(alphabet)
-		if len(nodeKey) == 0 {
-			panic("irCandidateRemove: invoked by non alphabet node")
-		}
-
-		id := append(key, []byte("delete")...)
-		hashID := crypto.Sha256(id)
-
-		n := common.Vote(ctx, hashID, nodeKey)
-		if n < threshold {
-			return true
-		}
 	}
 
 	nodes := []common.IRNode{} // it is explicit declaration of empty slice, not nil
@@ -185,7 +170,7 @@ func InnerRingCandidateAdd(key interop.PublicKey) bool {
 	ctx := storage.GetContext()
 
 	if !runtime.CheckWitness(key) {
-		panic("irCandidateAdd: you should be the owner of the public key")
+		panic("irCandidateAdd: this method must be invoked by candidate")
 	}
 
 	c := common.IRNode{PublicKey: key}
@@ -287,31 +272,21 @@ func Withdraw(user []byte, amount int) bool {
 // Cheque sends gas assets back to the user if they were successfully
 // locked in NeoFS balance contract.
 func Cheque(id []byte, user interop.Hash160, amount int, lockAcc []byte) bool {
-	ctx := storage.GetContext()
+	multiaddr := AlphabetAddress()
-	alphabet := getNodes(ctx, alphabetKey)
+	if !runtime.CheckWitness(multiaddr) {
-	threshold := len(alphabet)*2/3 + 1
+		panic("cheque: this method must be invoked by alphabet")
-
-	hashID := crypto.Sha256(id)
-
-	key := common.InnerRingInvoker(alphabet)
-	if len(key) == 0 {
-		panic("cheque: invoked by non alphabet node")
 	}
 
-	n := common.Vote(ctx, hashID, key)
+	from := runtime.GetExecutingScriptHash()
-	if n >= threshold {
-		common.RemoveVotes(ctx, hashID)
-		from := runtime.GetExecutingScriptHash()
 
-		transferred := gas.Transfer(from, user, amount, nil)
+	transferred := gas.Transfer(from, user, amount, nil)
-		if !transferred {
+	if !transferred {
-			panic("cheque: failed to transfer funds, aborting")
+		panic("cheque: failed to transfer funds, aborting")
-		}
-
-		runtime.Log("cheque: funds have been transferred")
-		runtime.Notify("Cheque", id, user, amount, lockAcc)
 	}
 
+	runtime.Log("cheque: funds have been transferred")
+	runtime.Notify("Cheque", id, user, amount, lockAcc)
+
 	return true
 }
 
@@ -360,12 +335,9 @@ func AlphabetUpdate(chequeID []byte, args []interop.PublicKey) bool {
 		panic("alphabetUpdate: bad arguments")
 	}
 
-	alphabet := getNodes(ctx, alphabetKey)
+	multiaddr := AlphabetAddress()
-	threshold := len(alphabet)*2/3 + 1
+	if !runtime.CheckWitness(multiaddr) {
-
+		panic("alphabetUpdate: this method must be invoked by alphabet")
-	key := common.InnerRingInvoker(alphabet)
-	if len(key) == 0 {
-		panic("innerRingUpdate: invoked by non alphabet node")
 	}
 
 	newAlphabet := []common.IRNode{}
@@ -381,17 +353,10 @@ func AlphabetUpdate(chequeID []byte, args []interop.PublicKey) bool {
 		})
 	}
 
-	hashID := crypto.Sha256(chequeID)
+	common.SetSerialized(ctx, alphabetKey, newAlphabet)
 
-	n := common.Vote(ctx, hashID, key)
+	runtime.Notify("AlphabetUpdate", chequeID, newAlphabet)
-	if n >= threshold {
+	runtime.Log("alphabetUpdate: alphabet list has been updated")
-		common.RemoveVotes(ctx, hashID)
-
-		common.SetSerialized(ctx, alphabetKey, newAlphabet)
-
-		runtime.Notify("AlphabetUpdate", chequeID, newAlphabet)
-		runtime.Log("alphabetUpdate: alphabet list has been updated")
-	}
 
 	return true
 }
@@ -406,27 +371,15 @@ func Config(key []byte) interface{} {
 func SetConfig(id, key, val []byte) bool {
 	ctx := storage.GetContext()
 
-	// check if it is alphabet invocation
+	multiaddr := AlphabetAddress()
-	alphabet := getNodes(ctx, alphabetKey)
+	if !runtime.CheckWitness(multiaddr) {
-	threshold := len(alphabet)*2/3 + 1
+		panic("setConfig: this method must be invoked by alphabet")
-
-	nodeKey := common.InnerRingInvoker(alphabet)
-	if len(nodeKey) == 0 {
-		panic("setConfig: invoked by non alphabet node")
 	}
 
-	// vote for new configuration value
+	setConfig(ctx, key, val)
-	hashID := crypto.Sha256(id)
 
-	n := common.Vote(ctx, hashID, nodeKey)
+	runtime.Notify("SetConfig", id, key, val)
-	if n >= threshold {
+	runtime.Log("setConfig: configuration has been updated")
-		common.RemoveVotes(ctx, hashID)
-
-		setConfig(ctx, key, val)
-
-		runtime.Notify("SetConfig", id, key, val)
-		runtime.Log("setConfig: configuration has been updated")
-	}
 
 	return true
 }