package hop import ( "encoding/binary" "fmt" "io" sphinx "github.com/lightningnetwork/lightning-onion" "github.com/lightningnetwork/lnd/lnwire" "github.com/lightningnetwork/lnd/record" "github.com/lightningnetwork/lnd/tlv" ) // PayloadViolation is an enum encapsulating the possible invalid payload // violations that can occur when processing or validating a payload. type PayloadViolation byte const ( // OmittedViolation indicates that a type was expected to be found the // payload but was absent. OmittedViolation PayloadViolation = iota // IncludedViolation indicates that a type was expected to be omitted // from the payload but was present. IncludedViolation // RequiredViolation indicates that an unknown even type was found in // the payload that we could not process. RequiredViolation ) // String returns a human-readable description of the violation as a verb. func (v PayloadViolation) String() string { switch v { case OmittedViolation: return "omitted" case IncludedViolation: return "included" case RequiredViolation: return "required" default: return "unknown violation" } } // ErrInvalidPayload is an error returned when a parsed onion payload either // included or omitted incorrect records for a particular hop type. type ErrInvalidPayload struct { // Type the record's type that cause the violation. Type tlv.Type // Violation is an enum indicating the type of violation detected in // processing Type. Violation PayloadViolation // FinalHop if true, indicates that the violation is for the final hop // in the route (identified by next hop id), otherwise the violation is // for an intermediate hop. FinalHop bool } // Error returns a human-readable description of the invalid payload error. func (e ErrInvalidPayload) Error() string { hopType := "intermediate" if e.FinalHop { hopType = "final" } return fmt.Sprintf("onion payload for %s hop %v record with type %d", hopType, e.Violation, e.Type) } // Payload encapsulates all information delivered to a hop in an onion payload. // A Hop can represent either a TLV or legacy payload. The primary forwarding // instruction can be accessed via ForwardingInfo, and additional records can be // accessed by other member functions. type Payload struct { // FwdInfo holds the basic parameters required for HTLC forwarding, e.g. // amount, cltv, and next hop. FwdInfo ForwardingInfo // MPP holds the info provided in an option_mpp record when parsed from // a TLV onion payload. MPP *record.MPP } // NewLegacyPayload builds a Payload from the amount, cltv, and next hop // parameters provided by leegacy onion payloads. func NewLegacyPayload(f *sphinx.HopData) *Payload { nextHop := binary.BigEndian.Uint64(f.NextAddress[:]) return &Payload{ FwdInfo: ForwardingInfo{ Network: BitcoinNetwork, NextHop: lnwire.NewShortChanIDFromInt(nextHop), AmountToForward: lnwire.MilliSatoshi(f.ForwardAmount), OutgoingCTLV: f.OutgoingCltv, }, } } // NewPayloadFromReader builds a new Hop from the passed io.Reader. The reader // should correspond to the bytes encapsulated in a TLV onion payload. func NewPayloadFromReader(r io.Reader) (*Payload, error) { var ( cid uint64 amt uint64 cltv uint32 mpp = &record.MPP{} ) tlvStream, err := tlv.NewStream( record.NewAmtToFwdRecord(&amt), record.NewLockTimeRecord(&cltv), record.NewNextHopIDRecord(&cid), mpp.Record(), ) if err != nil { return nil, err } parsedTypes, err := tlvStream.DecodeWithParsedTypes(r) if err != nil { // Promote any required type failures into ErrInvalidPayload. if e, required := err.(tlv.ErrUnknownRequiredType); required { // If the parser returned an unknown required type // failure, we'll first check that the payload is // properly formed according to our known set of // constraints. If an error is discovered, this // overrides the required type failure. nextHop := lnwire.NewShortChanIDFromInt(cid) err = ValidateParsedPayloadTypes(parsedTypes, nextHop) if err != nil { return nil, err } // Otherwise the known constraints were applied // successfully, report the invalid type failure // returned by the parser. return nil, ErrInvalidPayload{ Type: tlv.Type(e), Violation: RequiredViolation, FinalHop: nextHop == Exit, } } return nil, err } // Validate whether the sender properly included or omitted tlv records // in accordance with BOLT 04. nextHop := lnwire.NewShortChanIDFromInt(cid) err = ValidateParsedPayloadTypes(parsedTypes, nextHop) if err != nil { return nil, err } // If no MPP field was parsed, set the MPP field on the resulting // payload to nil. if _, ok := parsedTypes[record.MPPOnionType]; !ok { mpp = nil } return &Payload{ FwdInfo: ForwardingInfo{ Network: BitcoinNetwork, NextHop: nextHop, AmountToForward: lnwire.MilliSatoshi(amt), OutgoingCTLV: cltv, }, MPP: mpp, }, nil } // ForwardingInfo returns the basic parameters required for HTLC forwarding, // e.g. amount, cltv, and next hop. func (h *Payload) ForwardingInfo() ForwardingInfo { return h.FwdInfo } // ValidateParsedPayloadTypes checks the types parsed from a hop payload to // ensure that the proper fields are either included or omitted. The finalHop // boolean should be true if the payload was parsed for an exit hop. The // requirements for this method are described in BOLT 04. func ValidateParsedPayloadTypes(parsedTypes tlv.TypeSet, nextHop lnwire.ShortChannelID) error { isFinalHop := nextHop == Exit _, hasAmt := parsedTypes[record.AmtOnionType] _, hasLockTime := parsedTypes[record.LockTimeOnionType] _, hasNextHop := parsedTypes[record.NextHopOnionType] _, hasMPP := parsedTypes[record.MPPOnionType] switch { // All hops must include an amount to forward. case !hasAmt: return ErrInvalidPayload{ Type: record.AmtOnionType, Violation: OmittedViolation, FinalHop: isFinalHop, } // All hops must include a cltv expiry. case !hasLockTime: return ErrInvalidPayload{ Type: record.LockTimeOnionType, Violation: OmittedViolation, FinalHop: isFinalHop, } // The exit hop should omit the next hop id. If nextHop != Exit, the // sender must have included a record, so we don't need to test for its // inclusion at intermediate hops directly. case isFinalHop && hasNextHop: return ErrInvalidPayload{ Type: record.NextHopOnionType, Violation: IncludedViolation, FinalHop: true, } // Intermediate nodes should never receive MPP fields. case !isFinalHop && hasMPP: return ErrInvalidPayload{ Type: record.MPPOnionType, Violation: IncludedViolation, FinalHop: isFinalHop, } } return nil }