From 8f2924d6cfb5beb35a3185144adf05559690c488 Mon Sep 17 00:00:00 2001 From: Pavel Karpy Date: Wed, 25 Aug 2021 14:26:21 +0300 Subject: [PATCH] [#770] pkg/morph/event: Add notary request preparator Add preparator for notary requests. Is parses raw notary requests, checks if it should be handled by Alphabet node. If handling is required, returns `NotaryEvent` that contains information about contract scripthash, method name and arguments of the call. Signed-off-by: Pavel Karpy --- pkg/morph/event/notary_preparator.go | 322 +++++++++++++++++++++++++++ pkg/morph/event/opcodes.go | 21 ++ 2 files changed, 343 insertions(+) create mode 100644 pkg/morph/event/notary_preparator.go create mode 100644 pkg/morph/event/opcodes.go diff --git a/pkg/morph/event/notary_preparator.go b/pkg/morph/event/notary_preparator.go new file mode 100644 index 00000000..f1df8019 --- /dev/null +++ b/pkg/morph/event/notary_preparator.go @@ -0,0 +1,322 @@ +package event + +import ( + "bytes" + "encoding/binary" + "errors" + "fmt" + + "github.com/nspcc-dev/neo-go/pkg/core/interop/interopnames" + "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/smartcontract" + "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/neofs-node/pkg/morph/client" +) + +var ( + errNotContractCall = errors.New("received main tx is not a contract call") + errUnexpectedWitnessAmount = errors.New("received main tx has unexpected amount of witnesses") + errUnexpectedCosignersAmount = errors.New("received main tx has unexpected amount of cosigners") + errIncorrectAlphabetSigner = errors.New("received main tx has incorrect Alphabet signer") + errIncorrectProxyWitnesses = errors.New("received main tx has non-empty Proxy witnesses") + errIncorrectAlphabet = errors.New("received main tx has incorrect Alphabet verification") + errIncorrectNotaryPlaceholder = errors.New("received main tx has incorrect Notary contract placeholder") + errIncorrectAttributesAmount = errors.New("received main tx has incorrect attributes amount") + errIncorrectAttribute = errors.New("received main tx has incorrect attribute") + errUnexpectedOpcode = errors.New("received main tx has unexpected(not PUSHDATA) NeoVM opcodes") + + errIncorrectFBAttributesAmount = errors.New("received fallback tx has incorrect attributes amount") + errIncorrectFBAttributes = errors.New("received fallback tx has incorrect attributes") + + // ErrTXAlreadyHandled is returned if received TX has already been signed. + ErrTXAlreadyHandled = errors.New("received main tx has already been handled") + + // ErrMainTXExpired is returned if received fallback TX is already valid. + ErrMainTXExpired = errors.New("received main tx has expired") +) + +// BlockCounter must return block count of the network +// from which notary requests are received. +type BlockCounter interface { + BlockCount() (res uint32, err error) +} + +// PreparatorPrm groups the required parameters of the Preparator constructor. +type PreparatorPrm struct { + AlphaKeys client.AlphabetKeys + + // BlockCount must return block count of the network + // from which notary requests are received. + BlockCounter BlockCounter +} + +// Preparator implements NotaryPreparator interface. +type Preparator struct { + // contractSysCall contract call in NeoVM + contractSysCall []byte + // dummyInvocationScript is invocation script from TX that is not signed. + dummyInvocationScript []byte + + alphaKeys client.AlphabetKeys + + blockCounter BlockCounter +} + +// notaryPreparator inits and returns NotaryPreparator. +// +// Considered to be used for preparing notary request +// for parsing it by event.Listener. +func notaryPreparator(prm PreparatorPrm) NotaryPreparator { + switch { + case prm.AlphaKeys == nil: + panic("alphabet keys source must not be nil") + case prm.BlockCounter == nil: + panic("block counter must not be nil") + } + + contractSysCall := make([]byte, 4) + binary.LittleEndian.PutUint32(contractSysCall, interopnames.ToID([]byte(interopnames.SystemContractCall))) + + dummyInvocationScript := append([]byte{byte(opcode.PUSHDATA1), 64}, make([]byte, 64)...) + + return Preparator{ + contractSysCall: contractSysCall, + dummyInvocationScript: dummyInvocationScript, + alphaKeys: prm.AlphaKeys, + blockCounter: prm.BlockCounter, + } +} + +// Prepare converts raw notary requests to NotaryEvent. +// +// Returns ErrTXAlreadyHandled if transaction shouldn't be +// parsed and handled. It is not "error case". Every handled +// transaction is expected to be received one more time +// from the Notary service but already signed. This happens +// since every notary call is a new notary request in fact. +func (p Preparator) Prepare(nr *payload.P2PNotaryRequest) (NotaryEvent, error) { + // notary request's main tx is expected to have + // exactly three witnesses: one for proxy contract, + // one for notary's invoker and one is for notary + // contract + if len(nr.MainTransaction.Scripts) != 3 { + return nil, errUnexpectedWitnessAmount + } + + // alphabet node should handle only notary requests + // that have been sent unsigned(by storage nodes) => + // such main TXs should have dummy scripts as an + // invocation script + // + // this check prevents notary flow recursion + if !bytes.Equal(nr.MainTransaction.Scripts[1].InvocationScript, p.dummyInvocationScript) { + return nil, ErrTXAlreadyHandled + } + + currentAlphabet, err := p.alphaKeys() + if err != nil { + return nil, fmt.Errorf("could not fetch Alphabet public keys: %w", err) + } + + err = p.validateCosigners(nr.MainTransaction.Signers, currentAlphabet) + if err != nil { + return nil, err + } + + // validate main TX's notary attribute + err = p.validateAttributes(nr.MainTransaction.Attributes, currentAlphabet) + if err != nil { + return nil, err + } + + // validate main TX's witnesses + err = p.validateWitnesses(nr.MainTransaction.Scripts, currentAlphabet) + if err != nil { + return nil, err + } + + // validate main TX expiration + err = p.validateExpiration(nr.FallbackTransaction) + if err != nil { + return nil, err + } + + var ( + opCode opcode.Opcode + param []byte + ) + + ctx := vm.NewContext(nr.MainTransaction.Script) + ops := make([]Op, 0, 16) // 16 is maximum num of opcodes for calling contracts with 4 args(no arrays of arrays) + + for { + opCode, param, err = ctx.Next() + if err != nil { + return nil, fmt.Errorf("could not get next opcode in script: %w", err) + } + + if opCode == opcode.RET { + break + } + + ops = append(ops, Op{code: opCode, param: param}) + } + + opsLen := len(ops) + + // check if it is tx with contract call + if !bytes.Equal(ops[opsLen-1].param, p.contractSysCall) { + return nil, errNotContractCall + } + + // retrieve contract's script hash + contractHash, err := util.Uint160DecodeBytesBE(ops[opsLen-2].param) + if err != nil { + return nil, fmt.Errorf("could not decode contract hash: %w", err) + } + + // retrieve contract's method + contractMethod := string(ops[opsLen-3].param) + + err = p.validateParameterOpcodes(ops[:opsLen-3]) + if err != nil { + return nil, err + } + + return parsedNotaryEvent{ + hash: contractHash, + notaryType: NotaryTypeFromString(contractMethod), + params: ops[:opsLen-3], + raw: nr, + }, nil +} + +func (p Preparator) validateParameterOpcodes(oo []Op) error { + // check for unexpected NeoVM opcodes + for _, o := range oo { + switch { + // only PUSH(and PACK for arrays) codes are allowed; + // number of params and their content must be checked + // in a notary parser and a notary handler of a + // particular contract + case o.code <= opcode.PUSH16 || o.code == opcode.PACK: + default: + return errUnexpectedOpcode + } + } + + return nil +} + +func (p Preparator) validateExpiration(fbTX *transaction.Transaction) error { + if len(fbTX.Attributes) != 3 { + return errIncorrectFBAttributesAmount + } + + nvbAttrs := fbTX.GetAttributes(transaction.NotValidBeforeT) + if len(nvbAttrs) != 1 { + return errIncorrectFBAttributes + } + + nvb, ok := nvbAttrs[0].Value.(*transaction.NotValidBefore) + if !ok { + return errIncorrectFBAttributes + } + + currBlock, err := p.blockCounter.BlockCount() + if err != nil { + return fmt.Errorf("could not fetch current chain height: %w", err) + } + + if currBlock >= nvb.Height { + return ErrMainTXExpired + } + + return nil +} + +func (p Preparator) validateCosigners(s []transaction.Signer, alphaKeys keys.PublicKeys) error { + if len(s) != 3 { + return errUnexpectedCosignersAmount + } + + alphaVerificationScript, err := smartcontract.CreateMultiSigRedeemScript(len(alphaKeys)*2/3+1, alphaKeys) + if err != nil { + return fmt.Errorf("could not get Alphabet verification script: %w", err) + } + + if !s[1].Account.Equals(hash.Hash160(alphaVerificationScript)) { + return errIncorrectAlphabetSigner + } + + return nil +} + +func (p Preparator) validateWitnesses(w []transaction.Witness, alphaKeys keys.PublicKeys) error { + // the first one(proxy contract) must have empty + // witnesses + if len(w[0].VerificationScript)+len(w[0].InvocationScript) != 0 { + return errIncorrectProxyWitnesses + } + + alphaVerificationScript, err := smartcontract.CreateMultiSigRedeemScript(len(alphaKeys)*2/3+1, alphaKeys) + if err != nil { + return fmt.Errorf("could not get Alphabet verification script: %w", err) + } + + // the second one must be witness of the current + // alphabet multiaccount + if !bytes.Equal(w[1].VerificationScript, alphaVerificationScript) { + return errIncorrectAlphabet + } + + // the third one must be a placeholder for notary + // contract witness + if !bytes.Equal(w[2].InvocationScript, p.dummyInvocationScript) || len(w[2].VerificationScript) != 0 { + return errIncorrectNotaryPlaceholder + } + + return nil +} + +func (p Preparator) validateAttributes(aa []transaction.Attribute, alphaKeys keys.PublicKeys) error { + // main tx must have exactly one attribute + if len(aa) != 1 { + return errIncorrectAttributesAmount + } + + val, ok := aa[0].Value.(*transaction.NotaryAssisted) + if !ok || val.NKeys != uint8(len(alphaKeys)) { + return errIncorrectAttribute + } + + return nil +} + +type parsedNotaryEvent struct { + hash util.Uint160 + notaryType NotaryType + params []Op + raw *payload.P2PNotaryRequest +} + +func (p parsedNotaryEvent) ScriptHash() util.Uint160 { + return p.hash +} + +func (p parsedNotaryEvent) Type() NotaryType { + return p.notaryType +} + +func (p parsedNotaryEvent) Params() []Op { + return p.params +} + +func (p parsedNotaryEvent) Raw() *payload.P2PNotaryRequest { + return p.raw +} diff --git a/pkg/morph/event/opcodes.go b/pkg/morph/event/opcodes.go new file mode 100644 index 00000000..1300e447 --- /dev/null +++ b/pkg/morph/event/opcodes.go @@ -0,0 +1,21 @@ +package event + +import "github.com/nspcc-dev/neo-go/pkg/vm/opcode" + +// Op is wrapper over Neo VM's opcode +// and its parameter. +type Op struct { + code opcode.Opcode + param []byte +} + +// Code returns Neo VM opcode. +func (o Op) Code() opcode.Opcode { + return o.code +} + +// Param returns parameter of wrapped +// Neo VM opcode. +func (o Op) Param() []byte { + return o.param +}