[#74] processing: Add processing contract

Processing contract deployed in main chain and processes
multi signature invocations of NeoFS contract by
verifying multi signature and paying for it.

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

Makefile

@@ -10,7 +10,7 @@ sidechain: alphabet morph
 
 alphabet_sc = alphabet
 morph_sc = audit balance container neofsid netmap proxy reputation
-mainnet_sc = neofs
+mainnet_sc = neofs processing
 
 define sc_template
 $(2)$(1)/$(1)_contract.nef: $(2)$(1)/$(1)_contract.go

processing/config.yml

@@ -0,0 +1,2 @@
+name: "NeoFS Multi Signature Processing"
+safemethods: ["verify", "version"]

processing/processing_contract.go

@@ -0,0 +1,69 @@
+package processingcontract
+
+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/native/gas"
+	"github.com/nspcc-dev/neo-go/pkg/interop/native/management"
+	"github.com/nspcc-dev/neo-go/pkg/interop/runtime"
+	"github.com/nspcc-dev/neo-go/pkg/interop/storage"
+	"github.com/nspcc-dev/neofs-contract/common"
+)
+
+const (
+	version = 1
+
+	neofsContractKey = "neofsScriptHash"
+
+	multiaddrMethod = "alphabetAddress"
+)
+
+func OnNEP17Payment(from interop.Hash160, amount int, data interface{}) {
+	caller := runtime.GetCallingScriptHash()
+	if !common.BytesEqual(caller, []byte(gas.Hash)) {
+		panic("onNEP17Payment: processing contract accepts GAS only")
+	}
+}
+
+func Init(owner, addrNeoFS interop.Hash160) {
+	ctx := storage.GetContext()
+
+	if !common.HasUpdateAccess(ctx) {
+		panic("only owner can reinitialize contract")
+	}
+
+	if len(addrNeoFS) != 20 {
+		panic("init: incorrect length of contract script hash")
+	}
+
+	storage.Put(ctx, common.OwnerKey, owner)
+	storage.Put(ctx, neofsContractKey, addrNeoFS)
+
+	runtime.Log("processing contract initialized")
+}
+
+func Migrate(script []byte, manifest []byte) bool {
+	ctx := storage.GetReadOnlyContext()
+
+	if !common.HasUpdateAccess(ctx) {
+		runtime.Log("only owner can update contract")
+		return false
+	}
+
+	management.Update(script, manifest)
+	runtime.Log("processing contract updated")
+
+	return true
+}
+
+func Verify() bool {
+	ctx := storage.GetContext()
+	neofsContractAddr := storage.Get(ctx, neofsContractKey).(interop.Hash160)
+	multiaddr := contract.Call(neofsContractAddr, multiaddrMethod, contract.ReadOnly).(interop.Hash160)
+
+	return runtime.CheckWitness(multiaddr)
+}
+
+func Version() int {
+	return version
+}