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payload.go
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payload.go
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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
// AMP holds the info provided in an option_amp record when parsed from
// a TLV onion payload.
AMP *record.AMP
// customRecords are user-defined records in the custom type range that
// were included in the payload.
customRecords record.CustomSet
}
// 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,
},
customRecords: make(record.CustomSet),
}
}
// 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{}
amp = &record.AMP{}
)
tlvStream, err := tlv.NewStream(
record.NewAmtToFwdRecord(&amt),
record.NewLockTimeRecord(&cltv),
record.NewNextHopIDRecord(&cid),
mpp.Record(),
amp.Record(),
)
if err != nil {
return nil, err
}
parsedTypes, err := tlvStream.DecodeWithParsedTypes(r)
if err != nil {
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
}
// Check for violation of the rules for mandatory fields.
violatingType := getMinRequiredViolation(parsedTypes)
if violatingType != nil {
return nil, ErrInvalidPayload{
Type: *violatingType,
Violation: RequiredViolation,
FinalHop: nextHop == Exit,
}
}
// If no MPP field was parsed, set the MPP field on the resulting
// payload to nil.
if _, ok := parsedTypes[record.MPPOnionType]; !ok {
mpp = nil
}
// If no AMP field was parsed, set the MPP field on the resulting
// payload to nil.
if _, ok := parsedTypes[record.AMPOnionType]; !ok {
amp = nil
}
// Filter out the custom records.
customRecords := NewCustomRecords(parsedTypes)
return &Payload{
FwdInfo: ForwardingInfo{
Network: BitcoinNetwork,
NextHop: nextHop,
AmountToForward: lnwire.MilliSatoshi(amt),
OutgoingCTLV: cltv,
},
MPP: mpp,
AMP: amp,
customRecords: customRecords,
}, 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
}
// NewCustomRecords filters the types parsed from the tlv stream for custom
// records.
func NewCustomRecords(parsedTypes tlv.TypeMap) record.CustomSet {
customRecords := make(record.CustomSet)
for t, parseResult := range parsedTypes {
if parseResult == nil || t < record.CustomTypeStart {
continue
}
customRecords[uint64(t)] = parseResult
}
return customRecords
}
// 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.TypeMap,
nextHop lnwire.ShortChannelID) error {
isFinalHop := nextHop == Exit
_, hasAmt := parsedTypes[record.AmtOnionType]
_, hasLockTime := parsedTypes[record.LockTimeOnionType]
_, hasNextHop := parsedTypes[record.NextHopOnionType]
_, hasMPP := parsedTypes[record.MPPOnionType]
_, hasAMP := parsedTypes[record.AMPOnionType]
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,
}
// Intermediate nodes should never receive AMP fields.
case !isFinalHop && hasAMP:
return ErrInvalidPayload{
Type: record.AMPOnionType,
Violation: IncludedViolation,
FinalHop: isFinalHop,
}
}
return nil
}
// MultiPath returns the record corresponding the option_mpp parsed from the
// onion payload.
func (h *Payload) MultiPath() *record.MPP {
return h.MPP
}
// AMPRecord returns the record corresponding with option_amp parsed from the
// onion payload.
func (h *Payload) AMPRecord() *record.AMP {
return h.AMP
}
// CustomRecords returns the custom tlv type records that were parsed from the
// payload.
func (h *Payload) CustomRecords() record.CustomSet {
return h.customRecords
}
// getMinRequiredViolation checks for unrecognized required (even) fields in the
// standard range and returns the lowest required type. Always returning the
// lowest required type allows a failure message to be deterministic.
func getMinRequiredViolation(set tlv.TypeMap) *tlv.Type {
var (
requiredViolation bool
minRequiredViolationType tlv.Type
)
for t, parseResult := range set {
// If a type is even but not known to us, we cannot process the
// payload. We are required to understand a field that we don't
// support.
//
// We always accept custom fields, because a higher level
// application may understand them.
if parseResult == nil || t%2 != 0 ||
t >= record.CustomTypeStart {
continue
}
if !requiredViolation || t < minRequiredViolationType {
minRequiredViolationType = t
}
requiredViolation = true
}
if requiredViolation {
return &minRequiredViolationType
}
return nil
}