package native import ( "encoding/binary" "errors" "fmt" "math" "math/big" "strings" "github.com/nspcc-dev/neo-go/pkg/core/dao" "github.com/nspcc-dev/neo-go/pkg/core/interop" "github.com/nspcc-dev/neo-go/pkg/core/interop/contract" "github.com/nspcc-dev/neo-go/pkg/core/interop/interopnames" "github.com/nspcc-dev/neo-go/pkg/core/native/nativenames" "github.com/nspcc-dev/neo-go/pkg/core/state" "github.com/nspcc-dev/neo-go/pkg/core/storage" "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/io" "github.com/nspcc-dev/neo-go/pkg/smartcontract" "github.com/nspcc-dev/neo-go/pkg/smartcontract/callflag" "github.com/nspcc-dev/neo-go/pkg/smartcontract/manifest" "github.com/nspcc-dev/neo-go/pkg/util" "github.com/nspcc-dev/neo-go/pkg/vm/emit" "github.com/nspcc-dev/neo-go/pkg/vm/opcode" "github.com/nspcc-dev/neo-go/pkg/vm/stackitem" ) // Oracle represents Oracle native contract. type Oracle struct { interop.ContractMD GAS *GAS NEO *NEO Desig *Designate } const ( oracleContractID = -6 maxURLLength = 256 maxFilterLength = 128 maxCallbackLength = 32 maxUserDataLength = 512 // maxRequestsCount is the maximum number of requests per URL maxRequestsCount = 256 oracleRequestPrice = 5000_0000 ) var oracleScript []byte func init() { _, h := state.CreateNativeContractHash(oracleContractID) w := io.NewBufBinWriter() emit.Int(w.BinWriter, 0) emit.Opcodes(w.BinWriter, opcode.NEWARRAY) emit.Int(w.BinWriter, int64(callflag.All)) emit.String(w.BinWriter, "finish") emit.Bytes(w.BinWriter, h.BytesBE()) emit.Syscall(w.BinWriter, interopnames.SystemContractCall) oracleScript = w.Bytes() } var ( prefixIDList = []byte{6} prefixRequest = []byte{7} prefixRequestID = []byte{9} ) // Various validation errors. var ( ErrBigArgument = errors.New("some of the arguments are invalid") ErrInvalidWitness = errors.New("witness check failed") ErrNotEnoughGas = errors.New("gas limit exceeded") ErrRequestNotFound = errors.New("oracle request not found") ErrResponseNotFound = errors.New("oracle response not found") ) // GetOracleResponseScript returns script for transaction with oracle response. func GetOracleResponseScript() []byte { b := make([]byte, len(oracleScript)) copy(b, oracleScript) return b } func newOracle() *Oracle { o := &Oracle{ContractMD: *interop.NewContractMD(nativenames.Oracle, oracleContractID)} desc := newDescriptor("request", smartcontract.VoidType, manifest.NewParameter("url", smartcontract.StringType), manifest.NewParameter("filter", smartcontract.StringType), manifest.NewParameter("callback", smartcontract.StringType), manifest.NewParameter("userData", smartcontract.AnyType), manifest.NewParameter("gasForResponse", smartcontract.IntegerType)) md := newMethodAndPrice(o.request, oracleRequestPrice, callflag.WriteStates|callflag.AllowNotify) o.AddMethod(md, desc) desc = newDescriptor("finish", smartcontract.VoidType) md = newMethodAndPrice(o.finish, 0, callflag.WriteStates|callflag.AllowCall|callflag.AllowNotify) o.AddMethod(md, desc) desc = newDescriptor("verify", smartcontract.BoolType) md = newMethodAndPrice(o.verify, 100_0000, callflag.NoneFlag) o.AddMethod(md, desc) o.AddEvent("OracleRequest", manifest.NewParameter("Id", smartcontract.IntegerType), manifest.NewParameter("RequestContract", smartcontract.Hash160Type), manifest.NewParameter("Url", smartcontract.StringType), manifest.NewParameter("Filter", smartcontract.StringType)) o.AddEvent("OracleResponse", manifest.NewParameter("Id", smartcontract.IntegerType), manifest.NewParameter("OriginalTx", smartcontract.Hash256Type)) return o } // OnPersist implements Contract interface. func (o *Oracle) OnPersist(ic *interop.Context) error { return nil } // PostPersist represents `postPersist` method. func (o *Oracle) PostPersist(ic *interop.Context) error { var nodes keys.PublicKeys var reward []big.Int single := new(big.Int).SetUint64(oracleRequestPrice) for _, tx := range ic.Block.Transactions { resp := getResponse(tx) if resp == nil { continue } reqKey := makeRequestKey(resp.ID) req := new(state.OracleRequest) if err := o.getSerializableFromDAO(ic.DAO, reqKey, req); err != nil { continue } if err := ic.DAO.DeleteStorageItem(o.ContractID, reqKey); err != nil { return err } idKey := makeIDListKey(req.URL) idList := new(IDList) if err := o.getSerializableFromDAO(ic.DAO, idKey, idList); err != nil { return err } if !idList.Remove(resp.ID) { return errors.New("response ID wasn't found") } var err error if len(*idList) == 0 { err = ic.DAO.DeleteStorageItem(o.ContractID, idKey) } else { si := &state.StorageItem{Value: idList.Bytes()} err = ic.DAO.PutStorageItem(o.ContractID, idKey, si) } if err != nil { return err } if nodes == nil { nodes, err = o.GetOracleNodes(ic.DAO) if err != nil { return err } reward = make([]big.Int, len(nodes)) } if len(reward) > 0 { index := resp.ID % uint64(len(nodes)) reward[index].Add(&reward[index], single) } } for i := range reward { o.GAS.mint(ic, nodes[i].GetScriptHash(), &reward[i], false) } return nil } // Metadata returns contract metadata. func (o *Oracle) Metadata() *interop.ContractMD { return &o.ContractMD } // Initialize initializes Oracle contract. func (o *Oracle) Initialize(ic *interop.Context) error { si := &state.StorageItem{Value: make([]byte, 8)} // uint64(0) LE return ic.DAO.PutStorageItem(o.ContractID, prefixRequestID, si) } func getResponse(tx *transaction.Transaction) *transaction.OracleResponse { for i := range tx.Attributes { if tx.Attributes[i].Type == transaction.OracleResponseT { return tx.Attributes[i].Value.(*transaction.OracleResponse) } } return nil } func (o *Oracle) finish(ic *interop.Context, _ []stackitem.Item) stackitem.Item { err := o.FinishInternal(ic) if err != nil { panic(err) } return stackitem.Null{} } // FinishInternal processes oracle response. func (o *Oracle) FinishInternal(ic *interop.Context) error { resp := getResponse(ic.Tx) if resp == nil { return ErrResponseNotFound } req, err := o.GetRequestInternal(ic.DAO, resp.ID) if err != nil { return ErrRequestNotFound } ic.Notifications = append(ic.Notifications, state.NotificationEvent{ ScriptHash: o.Hash, Name: "OracleResponse", Item: stackitem.NewArray([]stackitem.Item{ stackitem.Make(resp.ID), stackitem.Make(req.OriginalTxID.BytesBE()), }), }) r := io.NewBinReaderFromBuf(req.UserData) userData := stackitem.DecodeBinaryStackItem(r) args := []stackitem.Item{ stackitem.Make(req.URL), stackitem.Make(userData), stackitem.Make(resp.Code), stackitem.Make(resp.Result), } cs, err := ic.GetContract(req.CallbackContract) if err != nil { return err } return contract.CallFromNative(ic, o.Hash, cs, req.CallbackMethod, args, false) } func (o *Oracle) request(ic *interop.Context, args []stackitem.Item) stackitem.Item { url, err := stackitem.ToString(args[0]) if err != nil { panic(err) } var filter *string _, ok := args[1].(stackitem.Null) if !ok { // Check UTF-8 validity. str, err := stackitem.ToString(args[1]) if err != nil { panic(err) } filter = &str } cb, err := stackitem.ToString(args[2]) if err != nil { panic(err) } userData := args[3] gas, err := args[4].TryInteger() if err != nil { panic(err) } if err := o.RequestInternal(ic, url, filter, cb, userData, gas); err != nil { panic(err) } return stackitem.Null{} } // RequestInternal processes oracle request. func (o *Oracle) RequestInternal(ic *interop.Context, url string, filter *string, cb string, userData stackitem.Item, gas *big.Int) error { if len(url) > maxURLLength || (filter != nil && len(*filter) > maxFilterLength) || len(cb) > maxCallbackLength || gas.Uint64() < 1000_0000 { return ErrBigArgument } if strings.HasPrefix(cb, "_") { return errors.New("disallowed callback method (starts with '_')") } if !ic.VM.AddGas(gas.Int64()) { return ErrNotEnoughGas } callingHash := ic.VM.GetCallingScriptHash() o.GAS.mint(ic, o.Hash, gas, false) si := ic.DAO.GetStorageItem(o.ContractID, prefixRequestID) id := binary.LittleEndian.Uint64(si.Value) + 1 binary.LittleEndian.PutUint64(si.Value, id) if err := ic.DAO.PutStorageItem(o.ContractID, prefixRequestID, si); err != nil { return err } // Should be executed from contract. _, err := ic.GetContract(ic.VM.GetCallingScriptHash()) if err != nil { return err } w := io.NewBufBinWriter() stackitem.EncodeBinaryStackItem(userData, w.BinWriter) if w.Err != nil { return w.Err } data := w.Bytes() if len(data) > maxUserDataLength { return ErrBigArgument } var filterNotif stackitem.Item if filter != nil { filterNotif = stackitem.Make(*filter) } else { filterNotif = stackitem.Null{} } ic.Notifications = append(ic.Notifications, state.NotificationEvent{ ScriptHash: o.Hash, Name: "OracleRequest", Item: stackitem.NewArray([]stackitem.Item{ stackitem.Make(id), stackitem.Make(ic.VM.GetCallingScriptHash().BytesBE()), stackitem.Make(url), filterNotif, }), }) req := &state.OracleRequest{ OriginalTxID: o.getOriginalTxID(ic.DAO, ic.Tx), GasForResponse: gas.Uint64(), URL: url, Filter: filter, CallbackContract: callingHash, CallbackMethod: cb, UserData: data, } return o.PutRequestInternal(id, req, ic.DAO) } // PutRequestInternal puts oracle request with the specified id to d. func (o *Oracle) PutRequestInternal(id uint64, req *state.OracleRequest, d dao.DAO) error { reqItem := &state.StorageItem{Value: req.Bytes()} reqKey := makeRequestKey(id) if err := d.PutStorageItem(o.ContractID, reqKey, reqItem); err != nil { return err } // Add request ID to the id list. lst := new(IDList) key := makeIDListKey(req.URL) if err := o.getSerializableFromDAO(d, key, lst); err != nil && !errors.Is(err, storage.ErrKeyNotFound) { return err } if len(*lst) >= maxRequestsCount { return fmt.Errorf("there are too many pending requests for %s url", req.URL) } *lst = append(*lst, id) si := &state.StorageItem{Value: lst.Bytes()} return d.PutStorageItem(o.ContractID, key, si) } // GetScriptHash returns script hash or oracle nodes. func (o *Oracle) GetScriptHash(d dao.DAO) (util.Uint160, error) { return o.Desig.getLastDesignatedHash(d, RoleOracle) } // GetOracleNodes returns public keys of oracle nodes. func (o *Oracle) GetOracleNodes(d dao.DAO) (keys.PublicKeys, error) { nodes, _, err := o.Desig.GetDesignatedByRole(d, RoleOracle, math.MaxUint32) return nodes, err } // GetRequestInternal returns request by ID and key under which it is stored. func (o *Oracle) GetRequestInternal(d dao.DAO, id uint64) (*state.OracleRequest, error) { key := makeRequestKey(id) req := new(state.OracleRequest) return req, o.getSerializableFromDAO(d, key, req) } // GetIDListInternal returns request by ID and key under which it is stored. func (o *Oracle) GetIDListInternal(d dao.DAO, url string) (*IDList, error) { key := makeIDListKey(url) idList := new(IDList) return idList, o.getSerializableFromDAO(d, key, idList) } func (o *Oracle) verify(ic *interop.Context, _ []stackitem.Item) stackitem.Item { return stackitem.NewBool(ic.Tx.HasAttribute(transaction.OracleResponseT)) } func (o *Oracle) getOriginalTxID(d dao.DAO, tx *transaction.Transaction) util.Uint256 { for i := range tx.Attributes { if tx.Attributes[i].Type == transaction.OracleResponseT { id := tx.Attributes[i].Value.(*transaction.OracleResponse).ID req, _ := o.GetRequestInternal(d, id) return req.OriginalTxID } } return tx.Hash() } func makeRequestKey(id uint64) []byte { k := make([]byte, 9) k[0] = prefixRequest[0] binary.LittleEndian.PutUint64(k[1:], id) return k } func makeIDListKey(url string) []byte { return append(prefixIDList, hash.Hash160([]byte(url)).BytesBE()...) } func (o *Oracle) getSerializableFromDAO(d dao.DAO, key []byte, item io.Serializable) error { return getSerializableFromDAO(o.ContractID, d, key, item) }