lnd.xprv/zpay32/decode.go

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package zpay32
import (
"bytes"
"encoding/binary"
"errors"
"fmt"
"strings"
"time"
"github.com/btcsuite/btcd/btcec"
"github.com/btcsuite/btcd/chaincfg"
"github.com/btcsuite/btcd/chaincfg/chainhash"
"github.com/btcsuite/btcutil"
"github.com/btcsuite/btcutil/bech32"
"github.com/lightningnetwork/lnd/lnwire"
)
// Decode parses the provided encoded invoice and returns a decoded Invoice if
// it is valid by BOLT-0011 and matches the provided active network.
func Decode(invoice string, net *chaincfg.Params) (*Invoice, error) {
decodedInvoice := Invoice{}
// Before bech32 decoding the invoice, make sure that it is not too large.
// This is done as an anti-DoS measure since bech32 decoding is expensive.
if len(invoice) > maxInvoiceLength {
return nil, ErrInvoiceTooLarge
}
// Decode the invoice using the modified bech32 decoder.
hrp, data, err := decodeBech32(invoice)
if err != nil {
return nil, err
}
// We expect the human-readable part to at least have ln + one char
// encoding the network.
if len(hrp) < 3 {
return nil, fmt.Errorf("hrp too short")
}
// First two characters of HRP should be "ln".
if hrp[:2] != "ln" {
return nil, fmt.Errorf("prefix should be \"ln\"")
}
// The next characters should be a valid prefix for a segwit BIP173
// address that match the active network.
if !strings.HasPrefix(hrp[2:], net.Bech32HRPSegwit) {
return nil, fmt.Errorf(
"invoice not for current active network '%s'", net.Name)
}
decodedInvoice.Net = net
// Optionally, if there's anything left of the HRP after ln + the segwit
// prefix, we try to decode this as the payment amount.
var netPrefixLength = len(net.Bech32HRPSegwit) + 2
if len(hrp) > netPrefixLength {
amount, err := decodeAmount(hrp[netPrefixLength:])
if err != nil {
return nil, err
}
decodedInvoice.MilliSat = &amount
}
// Everything except the last 520 bits of the data encodes the invoice's
// timestamp and tagged fields.
if len(data) < signatureBase32Len {
return nil, errors.New("short invoice")
}
invoiceData := data[:len(data)-signatureBase32Len]
// Parse the timestamp and tagged fields, and fill the Invoice struct.
if err := parseData(&decodedInvoice, invoiceData, net); err != nil {
return nil, err
}
// The last 520 bits (104 groups) make up the signature.
sigBase32 := data[len(data)-signatureBase32Len:]
sigBase256, err := bech32.ConvertBits(sigBase32, 5, 8, true)
if err != nil {
return nil, err
}
var sig lnwire.Sig
copy(sig[:], sigBase256[:64])
recoveryID := sigBase256[64]
// The signature is over the hrp + the data the invoice, encoded in
// base 256.
taggedDataBytes, err := bech32.ConvertBits(invoiceData, 5, 8, true)
if err != nil {
return nil, err
}
toSign := append([]byte(hrp), taggedDataBytes...)
// We expect the signature to be over the single SHA-256 hash of that
// data.
hash := chainhash.HashB(toSign)
// If the destination pubkey was provided as a tagged field, use that
// to verify the signature, if not do public key recovery.
if decodedInvoice.Destination != nil {
signature, err := sig.ToSignature()
if err != nil {
return nil, fmt.Errorf("unable to deserialize "+
"signature: %v", err)
}
if !signature.Verify(hash, decodedInvoice.Destination) {
return nil, fmt.Errorf("invalid invoice signature")
}
} else {
headerByte := recoveryID + 27 + 4
compactSign := append([]byte{headerByte}, sig[:]...)
pubkey, _, err := btcec.RecoverCompact(btcec.S256(),
compactSign, hash)
if err != nil {
return nil, err
}
decodedInvoice.Destination = pubkey
}
// If no feature vector was decoded, populate an empty one.
if decodedInvoice.Features == nil {
decodedInvoice.Features = lnwire.NewFeatureVector(
nil, lnwire.Features,
)
}
// Now that we have created the invoice, make sure it has the required
// fields set.
if err := validateInvoice(&decodedInvoice); err != nil {
return nil, err
}
return &decodedInvoice, nil
}
// parseData parses the data part of the invoice. It expects base32 data
// returned from the bech32.Decode method, except signature.
func parseData(invoice *Invoice, data []byte, net *chaincfg.Params) error {
// It must contain the timestamp, encoded using 35 bits (7 groups).
if len(data) < timestampBase32Len {
return fmt.Errorf("data too short: %d", len(data))
}
t, err := parseTimestamp(data[:timestampBase32Len])
if err != nil {
return err
}
invoice.Timestamp = time.Unix(int64(t), 0)
// The rest are tagged parts.
tagData := data[7:]
return parseTaggedFields(invoice, tagData, net)
}
// parseTimestamp converts a 35-bit timestamp (encoded in base32) to uint64.
func parseTimestamp(data []byte) (uint64, error) {
if len(data) != timestampBase32Len {
return 0, fmt.Errorf("timestamp must be 35 bits, was %d",
len(data)*5)
}
return base32ToUint64(data)
}
// parseTaggedFields takes the base32 encoded tagged fields of the invoice, and
// fills the Invoice struct accordingly.
func parseTaggedFields(invoice *Invoice, fields []byte, net *chaincfg.Params) error {
index := 0
for len(fields)-index > 0 {
// If there are less than 3 groups to read, there cannot be more
// interesting information, as we need the type (1 group) and
// length (2 groups).
//
// This means the last tagged field is broken.
if len(fields)-index < 3 {
return ErrBrokenTaggedField
}
typ := fields[index]
dataLength, err := parseFieldDataLength(fields[index+1 : index+3])
if err != nil {
return err
}
// If we don't have enough field data left to read this length,
// return error.
if len(fields) < index+3+int(dataLength) {
return ErrInvalidFieldLength
}
base32Data := fields[index+3 : index+3+int(dataLength)]
// Advance the index in preparation for the next iteration.
index += 3 + int(dataLength)
switch typ {
case fieldTypeP:
if invoice.PaymentHash != nil {
// We skip the field if we have already seen a
// supported one.
continue
}
invoice.PaymentHash, err = parse32Bytes(base32Data)
case fieldTypeS:
if invoice.PaymentAddr != nil {
// We skip the field if we have already seen a
// supported one.
continue
}
invoice.PaymentAddr, err = parse32Bytes(base32Data)
case fieldTypeD:
if invoice.Description != nil {
// We skip the field if we have already seen a
// supported one.
continue
}
invoice.Description, err = parseDescription(base32Data)
case fieldTypeN:
if invoice.Destination != nil {
// We skip the field if we have already seen a
// supported one.
continue
}
invoice.Destination, err = parseDestination(base32Data)
case fieldTypeH:
if invoice.DescriptionHash != nil {
// We skip the field if we have already seen a
// supported one.
continue
}
invoice.DescriptionHash, err = parse32Bytes(base32Data)
case fieldTypeX:
if invoice.expiry != nil {
// We skip the field if we have already seen a
// supported one.
continue
}
invoice.expiry, err = parseExpiry(base32Data)
case fieldTypeC:
if invoice.minFinalCLTVExpiry != nil {
// We skip the field if we have already seen a
// supported one.
continue
}
invoice.minFinalCLTVExpiry, err = parseMinFinalCLTVExpiry(base32Data)
case fieldTypeF:
if invoice.FallbackAddr != nil {
// We skip the field if we have already seen a
// supported one.
continue
}
invoice.FallbackAddr, err = parseFallbackAddr(base32Data, net)
case fieldTypeR:
// An `r` field can be included in an invoice multiple
// times, so we won't skip it if we have already seen
// one.
routeHint, err := parseRouteHint(base32Data)
if err != nil {
return err
}
invoice.RouteHints = append(invoice.RouteHints, routeHint)
case fieldType9:
if invoice.Features != nil {
// We skip the field if we have already seen a
// supported one.
continue
}
invoice.Features, err = parseFeatures(base32Data)
default:
// Ignore unknown type.
}
// Check if there was an error from parsing any of the tagged
// fields and return it.
if err != nil {
return err
}
}
return nil
}
// parseFieldDataLength converts the two byte slice into a uint16.
func parseFieldDataLength(data []byte) (uint16, error) {
if len(data) != 2 {
return 0, fmt.Errorf("data length must be 2 bytes, was %d",
len(data))
}
return uint16(data[0])<<5 | uint16(data[1]), nil
}
// parse32Bytes converts a 256-bit value (encoded in base32) to *[32]byte. This
// can be used for payment hashes, description hashes, payment addresses, etc.
func parse32Bytes(data []byte) (*[32]byte, error) {
var paymentHash [32]byte
// As BOLT-11 states, a reader must skip over the 32-byte fields if
// it does not have a length of 52, so avoid returning an error.
if len(data) != hashBase32Len {
return nil, nil
}
hash, err := bech32.ConvertBits(data, 5, 8, false)
if err != nil {
return nil, err
}
copy(paymentHash[:], hash)
return &paymentHash, nil
}
// parseDescription converts the data (encoded in base32) into a string to use
// as the description.
func parseDescription(data []byte) (*string, error) {
base256Data, err := bech32.ConvertBits(data, 5, 8, false)
if err != nil {
return nil, err
}
description := string(base256Data)
return &description, nil
}
// parseDestination converts the data (encoded in base32) into a 33-byte public
// key of the payee node.
func parseDestination(data []byte) (*btcec.PublicKey, error) {
// As BOLT-11 states, a reader must skip over the destination field
// if it does not have a length of 53, so avoid returning an error.
if len(data) != pubKeyBase32Len {
return nil, nil
}
base256Data, err := bech32.ConvertBits(data, 5, 8, false)
if err != nil {
return nil, err
}
return btcec.ParsePubKey(base256Data, btcec.S256())
}
// parseExpiry converts the data (encoded in base32) into the expiry time.
func parseExpiry(data []byte) (*time.Duration, error) {
expiry, err := base32ToUint64(data)
if err != nil {
return nil, err
}
duration := time.Duration(expiry) * time.Second
return &duration, nil
}
// parseMinFinalCLTVExpiry converts the data (encoded in base32) into a uint64
// to use as the minFinalCLTVExpiry.
func parseMinFinalCLTVExpiry(data []byte) (*uint64, error) {
expiry, err := base32ToUint64(data)
if err != nil {
return nil, err
}
return &expiry, nil
}
// parseFallbackAddr converts the data (encoded in base32) into a fallback
// on-chain address.
func parseFallbackAddr(data []byte, net *chaincfg.Params) (btcutil.Address, error) {
// Checks if the data is empty or contains a version without an address.
if len(data) < 2 {
return nil, fmt.Errorf("empty fallback address field")
}
var addr btcutil.Address
version := data[0]
switch version {
case 0:
witness, err := bech32.ConvertBits(data[1:], 5, 8, false)
if err != nil {
return nil, err
}
switch len(witness) {
case 20:
addr, err = btcutil.NewAddressWitnessPubKeyHash(witness, net)
case 32:
addr, err = btcutil.NewAddressWitnessScriptHash(witness, net)
default:
return nil, fmt.Errorf("unknown witness program length %d",
len(witness))
}
if err != nil {
return nil, err
}
case 17:
pubKeyHash, err := bech32.ConvertBits(data[1:], 5, 8, false)
if err != nil {
return nil, err
}
addr, err = btcutil.NewAddressPubKeyHash(pubKeyHash, net)
if err != nil {
return nil, err
}
case 18:
scriptHash, err := bech32.ConvertBits(data[1:], 5, 8, false)
if err != nil {
return nil, err
}
addr, err = btcutil.NewAddressScriptHashFromHash(scriptHash, net)
if err != nil {
return nil, err
}
default:
// Ignore unknown version.
}
return addr, nil
}
// parseRouteHint converts the data (encoded in base32) into an array containing
// one or more routing hop hints that represent a single route hint.
func parseRouteHint(data []byte) ([]HopHint, error) {
base256Data, err := bech32.ConvertBits(data, 5, 8, false)
if err != nil {
return nil, err
}
// Check that base256Data is a multiple of hopHintLen.
if len(base256Data)%hopHintLen != 0 {
return nil, fmt.Errorf("expected length multiple of %d bytes, "+
"got %d", hopHintLen, len(base256Data))
}
var routeHint []HopHint
for len(base256Data) > 0 {
hopHint := HopHint{}
hopHint.NodeID, err = btcec.ParsePubKey(base256Data[:33], btcec.S256())
if err != nil {
return nil, err
}
hopHint.ChannelID = binary.BigEndian.Uint64(base256Data[33:41])
hopHint.FeeBaseMSat = binary.BigEndian.Uint32(base256Data[41:45])
hopHint.FeeProportionalMillionths = binary.BigEndian.Uint32(base256Data[45:49])
hopHint.CLTVExpiryDelta = binary.BigEndian.Uint16(base256Data[49:51])
routeHint = append(routeHint, hopHint)
base256Data = base256Data[51:]
}
return routeHint, nil
}
// parseFeatures decodes any feature bits directly from the base32
// representation.
func parseFeatures(data []byte) (*lnwire.FeatureVector, error) {
rawFeatures := lnwire.NewRawFeatureVector()
err := rawFeatures.DecodeBase32(bytes.NewReader(data), len(data))
if err != nil {
return nil, err
}
return lnwire.NewFeatureVector(rawFeatures, lnwire.Features), nil
}
// base32ToUint64 converts a base32 encoded number to uint64.
func base32ToUint64(data []byte) (uint64, error) {
// Maximum that fits in uint64 is ceil(64 / 5) = 12 groups.
if len(data) > 13 {
return 0, fmt.Errorf("cannot parse data of length %d as uint64",
len(data))
}
val := uint64(0)
for i := 0; i < len(data); i++ {
val = val<<5 | uint64(data[i])
}
return val, nil
}