package native import ( "encoding/binary" "errors" "fmt" "math" "math/big" "strings" "sync/atomic" "github.com/nspcc-dev/neo-go/pkg/core/blockchainer/services" "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/native/nativenames" "github.com/nspcc-dev/neo-go/pkg/core/native/noderoles" "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/encoding/bigint" "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/util/slice" "github.com/nspcc-dev/neo-go/pkg/vm/emit" "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 oracleScript []byte // Module is an oracle module capable of talking with the external world. Module atomic.Value // newRequests contains new requests created during the current block. newRequests map[uint64]*state.OracleRequest } type OracleCache struct { requestPrice int64 } const ( oracleContractID = -9 maxURLLength = 256 maxFilterLength = 128 maxCallbackLength = 32 maxUserDataLength = 512 // maxRequestsCount is the maximum number of requests per URL. maxRequestsCount = 256 // DefaultOracleRequestPrice is the default amount GAS needed for an oracle request. DefaultOracleRequestPrice = 5000_0000 // MinimumResponseGas is the minimum response fee permitted for a request. MinimumResponseGas = 10_000_000 ) var ( prefixRequestPrice = []byte{5} 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") ErrLowResponseGas = errors.New("not enough gas for response") ErrNotEnoughGas = errors.New("gas limit exceeded") ErrRequestNotFound = errors.New("oracle request not found") ErrResponseNotFound = errors.New("oracle response not found") ) var ( _ interop.Contract = (*Oracle)(nil) _ dao.NativeContractCache = (*OracleCache)(nil) ) // Copy implements NativeContractCache interface. func (c *OracleCache) Copy() dao.NativeContractCache { cp := &OracleCache{} copyOracleCache(c, cp) return cp } func copyOracleCache(src, dst *OracleCache) { *dst = *src } func newOracle() *Oracle { o := &Oracle{ContractMD: *interop.NewContractMD(nativenames.Oracle, oracleContractID)} defer o.UpdateHash() o.oracleScript = CreateOracleResponseScript(o.Hash) 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, 0, callflag.States|callflag.AllowNotify) o.AddMethod(md, desc) desc = newDescriptor("finish", smartcontract.VoidType) md = newMethodAndPrice(o.finish, 0, callflag.States|callflag.AllowCall|callflag.AllowNotify) o.AddMethod(md, desc) desc = newDescriptor("verify", smartcontract.BoolType) md = newMethodAndPrice(o.verify, 1<<15, 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)) desc = newDescriptor("getPrice", smartcontract.IntegerType) md = newMethodAndPrice(o.getPrice, 1<<15, callflag.ReadStates) o.AddMethod(md, desc) desc = newDescriptor("setPrice", smartcontract.VoidType, manifest.NewParameter("price", smartcontract.IntegerType)) md = newMethodAndPrice(o.setPrice, 1<<15, callflag.States) o.AddMethod(md, desc) return o } // GetOracleResponseScript returns a script for the transaction with an oracle response. func (o *Oracle) GetOracleResponseScript() []byte { return slice.Copy(o.oracleScript) } // OnPersist implements the Contract interface. func (o *Oracle) OnPersist(ic *interop.Context) error { var err error if o.newRequests == nil { o.newRequests, err = o.getRequests(ic.DAO) } return err } // PostPersist represents `postPersist` method. func (o *Oracle) PostPersist(ic *interop.Context) error { p := o.getPriceInternal(ic.DAO) var nodes keys.PublicKeys var reward []big.Int single := big.NewInt(p) var removedIDs []uint64 orc, _ := o.Module.Load().(services.Oracle) for _, tx := range ic.Block.Transactions { resp := getResponse(tx) if resp == nil { continue } reqKey := makeRequestKey(resp.ID) req := new(state.OracleRequest) if err := o.getConvertibleFromDAO(ic.DAO, reqKey, req); err != nil { continue } ic.DAO.DeleteStorageItem(o.ID, reqKey) if orc != nil { removedIDs = append(removedIDs, resp.ID) } idKey := makeIDListKey(req.URL) idList := new(IDList) if err := o.getConvertibleFromDAO(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 { ic.DAO.DeleteStorageItem(o.ID, idKey) } else { err = putConvertibleToDAO(o.ID, ic.DAO, idKey, idList) } 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) } if len(removedIDs) != 0 && orc != nil { orc.RemoveRequests(removedIDs) } return o.updateCache(ic.DAO) } // Metadata returns contract metadata. func (o *Oracle) Metadata() *interop.ContractMD { return &o.ContractMD } // Initialize initializes an Oracle contract. func (o *Oracle) Initialize(ic *interop.Context) error { setIntWithKey(o.ID, ic.DAO, prefixRequestID, 0) setIntWithKey(o.ID, ic.DAO, prefixRequestPrice, DefaultOracleRequestPrice) cache := &OracleCache{ requestPrice: int64(DefaultOracleRequestPrice), } ic.DAO.SetCache(o.ID, cache) return nil } func (o *Oracle) InitializeCache(d *dao.Simple) { cache := &OracleCache{} cache.requestPrice = getIntWithKey(o.ID, d, prefixRequestPrice) d.SetCache(o.ID, cache) } 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 an 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.AddNotification(o.Hash, "OracleResponse", stackitem.NewArray([]stackitem.Item{ stackitem.Make(resp.ID), stackitem.Make(req.OriginalTxID.BytesBE()), })) origTx, _, err := ic.DAO.GetTransaction(req.OriginalTxID) if err != nil { return ErrRequestNotFound } ic.UseSigners(origTx.Signers) defer ic.UseSigners(nil) userData, err := stackitem.Deserialize(req.UserData) if err != nil { return err } args := []stackitem.Item{ stackitem.Make(req.URL), 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 !ic.VM.AddGas(o.getPriceInternal(ic.DAO)) { panic("insufficient gas") } if err := o.RequestInternal(ic, url, filter, cb, userData, gas); err != nil { panic(err) } return stackitem.Null{} } // RequestInternal processes an 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.IsInt64() { return ErrBigArgument } if gas.Int64() < MinimumResponseGas { return ErrLowResponseGas } 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.ID, prefixRequestID) itemID := bigint.FromBytes(si) id := itemID.Uint64() itemID.Add(itemID, intOne) ic.DAO.PutBigInt(o.ID, prefixRequestID, itemID) // Should be executed from the contract. _, err := ic.GetContract(ic.VM.GetCallingScriptHash()) if err != nil { return err } data, err := ic.DAO.GetItemCtx().Serialize(userData, false) if err != nil { return err } if len(data) > maxUserDataLength { return ErrBigArgument } data = slice.Copy(data) // Serialization context will be used in PutRequestInternal again. var filterNotif stackitem.Item if filter != nil { filterNotif = stackitem.Make(*filter) } else { filterNotif = stackitem.Null{} } ic.AddNotification(o.Hash, "OracleRequest", 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 the oracle request with the specified id to d. func (o *Oracle) PutRequestInternal(id uint64, req *state.OracleRequest, d *dao.Simple) error { reqKey := makeRequestKey(id) if err := putConvertibleToDAO(o.ID, d, reqKey, req); err != nil { return err } o.newRequests[id] = req // Add request ID to the id list. lst := new(IDList) key := makeIDListKey(req.URL) if err := o.getConvertibleFromDAO(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) return putConvertibleToDAO(o.ID, d, key, lst) } // GetScriptHash returns script hash of oracle nodes. func (o *Oracle) GetScriptHash(d *dao.Simple) (util.Uint160, error) { return o.Desig.GetLastDesignatedHash(d, noderoles.Oracle) } // GetOracleNodes returns public keys of oracle nodes. func (o *Oracle) GetOracleNodes(d *dao.Simple) (keys.PublicKeys, error) { nodes, _, err := o.Desig.GetDesignatedByRole(d, noderoles.Oracle, math.MaxUint32) return nodes, err } // GetRequestInternal returns the request by ID and key under which it is stored. func (o *Oracle) GetRequestInternal(d *dao.Simple, id uint64) (*state.OracleRequest, error) { key := makeRequestKey(id) req := new(state.OracleRequest) return req, o.getConvertibleFromDAO(d, key, req) } // GetIDListInternal returns the request by ID and key under which it is stored. func (o *Oracle) GetIDListInternal(d *dao.Simple, url string) (*IDList, error) { key := makeIDListKey(url) idList := new(IDList) return idList, o.getConvertibleFromDAO(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) getPrice(ic *interop.Context, _ []stackitem.Item) stackitem.Item { return stackitem.NewBigInteger(big.NewInt(o.getPriceInternal(ic.DAO))) } func (o *Oracle) getPriceInternal(d *dao.Simple) int64 { cache := d.GetROCache(o.ID).(*OracleCache) return cache.requestPrice } func (o *Oracle) setPrice(ic *interop.Context, args []stackitem.Item) stackitem.Item { price := toBigInt(args[0]) if price.Sign() <= 0 || !price.IsInt64() { panic("invalid register price") } if !o.NEO.checkCommittee(ic) { panic("invalid committee signature") } setIntWithKey(o.ID, ic.DAO, prefixRequestPrice, price.Int64()) cache := ic.DAO.GetRWCache(o.ID).(*OracleCache) cache.requestPrice = price.Int64() return stackitem.Null{} } func (o *Oracle) getOriginalTxID(d *dao.Simple, 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() } // getRequests returns all requests which have not been finished yet. func (o *Oracle) getRequests(d *dao.Simple) (map[uint64]*state.OracleRequest, error) { var reqs = make(map[uint64]*state.OracleRequest) var err error d.Seek(o.ID, storage.SeekRange{Prefix: prefixRequest}, func(k, v []byte) bool { if len(k) != 8 { err = errors.New("invalid request ID") return false } req := new(state.OracleRequest) err = stackitem.DeserializeConvertible(v, req) if err != nil { return false } id := binary.BigEndian.Uint64(k) reqs[id] = req return true }) if err != nil { return nil, err } return reqs, nil } func makeRequestKey(id uint64) []byte { k := make([]byte, 9) k[0] = prefixRequest[0] binary.BigEndian.PutUint64(k[1:], id) return k } func makeIDListKey(url string) []byte { return append(prefixIDList, hash.Hash160([]byte(url)).BytesBE()...) } func (o *Oracle) getConvertibleFromDAO(d *dao.Simple, key []byte, item stackitem.Convertible) error { return getConvertibleFromDAO(o.ID, d, key, item) } // updateCache updates cached Oracle values if they've been changed. func (o *Oracle) updateCache(d *dao.Simple) error { orc, _ := o.Module.Load().(services.Oracle) if orc == nil { return nil } reqs := o.newRequests o.newRequests = make(map[uint64]*state.OracleRequest) for id := range reqs { key := makeRequestKey(id) if si := d.GetStorageItem(o.ID, key); si == nil { // tx has failed delete(reqs, id) } } orc.AddRequests(reqs) return nil } // CreateOracleResponseScript returns a script that is used to create the native Oracle // response. func CreateOracleResponseScript(nativeOracleHash util.Uint160) []byte { w := io.NewBufBinWriter() emit.AppCall(w.BinWriter, nativeOracleHash, "finish", callflag.All) if w.Err != nil { panic(fmt.Errorf("failed to create Oracle response script: %w", w.Err)) } return w.Bytes() }