49c601e62a
As a preliminary step to isolating zpay32 in migrations 01-11, we'll split out the encoding and decoding logic into separate files. Migration 11 only requires invoice decoding, so this prevents us from needing to copy in the encoding logic that would otherwise be unused.
345 lines
9.2 KiB
Go
345 lines
9.2 KiB
Go
package zpay32
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import (
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"bytes"
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"encoding/binary"
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"fmt"
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"github.com/btcsuite/btcd/chaincfg/chainhash"
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"github.com/btcsuite/btcutil"
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"github.com/btcsuite/btcutil/bech32"
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"github.com/lightningnetwork/lnd/lnwire"
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)
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// Encode takes the given MessageSigner and returns a string encoding this
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// invoice signed by the node key of the signer.
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func (invoice *Invoice) Encode(signer MessageSigner) (string, error) {
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// First check that this invoice is valid before starting the encoding.
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if err := validateInvoice(invoice); err != nil {
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return "", err
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}
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// The buffer will encoded the invoice data using 5-bit groups (base32).
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var bufferBase32 bytes.Buffer
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// The timestamp will be encoded using 35 bits, in base32.
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timestampBase32 := uint64ToBase32(uint64(invoice.Timestamp.Unix()))
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// The timestamp must be exactly 35 bits, which means 7 groups. If it
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// can fit into fewer groups we add leading zero groups, if it is too
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// big we fail early, as there is not possible to encode it.
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if len(timestampBase32) > timestampBase32Len {
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return "", fmt.Errorf("timestamp too big: %d",
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invoice.Timestamp.Unix())
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}
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// Add zero bytes to the first timestampBase32Len-len(timestampBase32)
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// groups, then add the non-zero groups.
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zeroes := make([]byte, timestampBase32Len-len(timestampBase32),
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timestampBase32Len-len(timestampBase32))
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_, err := bufferBase32.Write(zeroes)
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if err != nil {
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return "", fmt.Errorf("unable to write to buffer: %v", err)
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}
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_, err = bufferBase32.Write(timestampBase32)
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if err != nil {
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return "", fmt.Errorf("unable to write to buffer: %v", err)
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}
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// We now write the tagged fields to the buffer, which will fill the
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// rest of the data part before the signature.
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if err := writeTaggedFields(&bufferBase32, invoice); err != nil {
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return "", err
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}
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// The human-readable part (hrp) is "ln" + net hrp + optional amount.
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hrp := "ln" + invoice.Net.Bech32HRPSegwit
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if invoice.MilliSat != nil {
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// Encode the amount using the fewest possible characters.
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am, err := encodeAmount(*invoice.MilliSat)
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if err != nil {
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return "", err
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}
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hrp += am
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}
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// The signature is over the single SHA-256 hash of the hrp + the
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// tagged fields encoded in base256.
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taggedFieldsBytes, err := bech32.ConvertBits(bufferBase32.Bytes(), 5, 8, true)
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if err != nil {
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return "", err
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}
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toSign := append([]byte(hrp), taggedFieldsBytes...)
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hash := chainhash.HashB(toSign)
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// We use compact signature format, and also encoded the recovery ID
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// such that a reader of the invoice can recover our pubkey from the
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// signature.
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sign, err := signer.SignCompact(hash)
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if err != nil {
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return "", err
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}
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// From the header byte we can extract the recovery ID, and the last 64
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// bytes encode the signature.
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recoveryID := sign[0] - 27 - 4
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var sig lnwire.Sig
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copy(sig[:], sign[1:])
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// If the pubkey field was explicitly set, it must be set to the pubkey
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// used to create the signature.
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if invoice.Destination != nil {
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signature, err := sig.ToSignature()
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if err != nil {
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return "", fmt.Errorf("unable to deserialize "+
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"signature: %v", err)
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}
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valid := signature.Verify(hash, invoice.Destination)
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if !valid {
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return "", fmt.Errorf("signature does not match " +
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"provided pubkey")
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}
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}
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// Convert the signature to base32 before writing it to the buffer.
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signBase32, err := bech32.ConvertBits(append(sig[:], recoveryID), 8, 5, true)
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if err != nil {
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return "", err
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}
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bufferBase32.Write(signBase32)
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// Now we can create the bech32 encoded string from the base32 buffer.
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b32, err := bech32.Encode(hrp, bufferBase32.Bytes())
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if err != nil {
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return "", err
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}
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// Before returning, check that the bech32 encoded string is not greater
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// than our largest supported invoice size.
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if len(b32) > maxInvoiceLength {
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return "", ErrInvoiceTooLarge
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}
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return b32, nil
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}
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// writeTaggedFields writes the non-nil tagged fields of the Invoice to the
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// base32 buffer.
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func writeTaggedFields(bufferBase32 *bytes.Buffer, invoice *Invoice) error {
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if invoice.PaymentHash != nil {
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err := writeBytes32(bufferBase32, fieldTypeP, *invoice.PaymentHash)
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if err != nil {
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return err
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}
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}
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if invoice.Description != nil {
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base32, err := bech32.ConvertBits([]byte(*invoice.Description),
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8, 5, true)
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if err != nil {
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return err
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}
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err = writeTaggedField(bufferBase32, fieldTypeD, base32)
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if err != nil {
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return err
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}
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}
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if invoice.DescriptionHash != nil {
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err := writeBytes32(
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bufferBase32, fieldTypeH, *invoice.DescriptionHash,
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)
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if err != nil {
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return err
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}
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}
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if invoice.minFinalCLTVExpiry != nil {
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finalDelta := uint64ToBase32(uint64(*invoice.minFinalCLTVExpiry))
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err := writeTaggedField(bufferBase32, fieldTypeC, finalDelta)
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if err != nil {
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return err
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}
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}
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if invoice.expiry != nil {
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seconds := invoice.expiry.Seconds()
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expiry := uint64ToBase32(uint64(seconds))
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err := writeTaggedField(bufferBase32, fieldTypeX, expiry)
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if err != nil {
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return err
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}
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}
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if invoice.FallbackAddr != nil {
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var version byte
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switch addr := invoice.FallbackAddr.(type) {
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case *btcutil.AddressPubKeyHash:
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version = 17
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case *btcutil.AddressScriptHash:
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version = 18
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case *btcutil.AddressWitnessPubKeyHash:
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version = addr.WitnessVersion()
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case *btcutil.AddressWitnessScriptHash:
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version = addr.WitnessVersion()
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default:
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return fmt.Errorf("unknown fallback address type")
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}
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base32Addr, err := bech32.ConvertBits(
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invoice.FallbackAddr.ScriptAddress(), 8, 5, true)
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if err != nil {
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return err
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}
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err = writeTaggedField(bufferBase32, fieldTypeF,
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append([]byte{version}, base32Addr...))
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if err != nil {
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return err
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}
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}
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for _, routeHint := range invoice.RouteHints {
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// Each hop hint is encoded using 51 bytes, so we'll make to
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// sure to allocate enough space for the whole route hint.
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routeHintBase256 := make([]byte, 0, hopHintLen*len(routeHint))
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for _, hopHint := range routeHint {
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hopHintBase256 := make([]byte, hopHintLen)
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copy(hopHintBase256[:33], hopHint.NodeID.SerializeCompressed())
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binary.BigEndian.PutUint64(
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hopHintBase256[33:41], hopHint.ChannelID,
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)
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binary.BigEndian.PutUint32(
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hopHintBase256[41:45], hopHint.FeeBaseMSat,
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)
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binary.BigEndian.PutUint32(
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hopHintBase256[45:49], hopHint.FeeProportionalMillionths,
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)
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binary.BigEndian.PutUint16(
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hopHintBase256[49:51], hopHint.CLTVExpiryDelta,
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)
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routeHintBase256 = append(routeHintBase256, hopHintBase256...)
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}
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routeHintBase32, err := bech32.ConvertBits(
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routeHintBase256, 8, 5, true,
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)
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if err != nil {
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return err
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}
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err = writeTaggedField(bufferBase32, fieldTypeR, routeHintBase32)
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if err != nil {
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return err
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}
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}
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if invoice.Destination != nil {
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// Convert 33 byte pubkey to 53 5-bit groups.
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pubKeyBase32, err := bech32.ConvertBits(
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invoice.Destination.SerializeCompressed(), 8, 5, true)
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if err != nil {
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return err
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}
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if len(pubKeyBase32) != pubKeyBase32Len {
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return fmt.Errorf("invalid pubkey length: %d",
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len(invoice.Destination.SerializeCompressed()))
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}
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err = writeTaggedField(bufferBase32, fieldTypeN, pubKeyBase32)
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if err != nil {
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return err
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}
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}
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if invoice.PaymentAddr != nil {
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err := writeBytes32(
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bufferBase32, fieldTypeS, *invoice.PaymentAddr,
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)
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if err != nil {
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return err
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}
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}
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if invoice.Features.SerializeSize32() > 0 {
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var b bytes.Buffer
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err := invoice.Features.RawFeatureVector.EncodeBase32(&b)
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if err != nil {
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return err
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}
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err = writeTaggedField(bufferBase32, fieldType9, b.Bytes())
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if err != nil {
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return err
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}
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}
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return nil
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}
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// writeBytes32 encodes a 32-byte array as base32 and writes it to bufferBase32
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// under the passed fieldType.
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func writeBytes32(bufferBase32 *bytes.Buffer, fieldType byte, b [32]byte) error {
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// Convert 32 byte hash to 52 5-bit groups.
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base32, err := bech32.ConvertBits(b[:], 8, 5, true)
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if err != nil {
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return err
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}
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return writeTaggedField(bufferBase32, fieldType, base32)
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}
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// writeTaggedField takes the type of a tagged data field, and the data of
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// the tagged field (encoded in base32), and writes the type, length and data
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// to the buffer.
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func writeTaggedField(bufferBase32 *bytes.Buffer, dataType byte, data []byte) error {
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// Length must be exactly 10 bits, so add leading zero groups if
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// needed.
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lenBase32 := uint64ToBase32(uint64(len(data)))
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for len(lenBase32) < 2 {
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lenBase32 = append([]byte{0}, lenBase32...)
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}
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if len(lenBase32) != 2 {
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return fmt.Errorf("data length too big to fit within 10 bits: %d",
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len(data))
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}
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err := bufferBase32.WriteByte(dataType)
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if err != nil {
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return fmt.Errorf("unable to write to buffer: %v", err)
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}
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_, err = bufferBase32.Write(lenBase32)
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if err != nil {
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return fmt.Errorf("unable to write to buffer: %v", err)
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}
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_, err = bufferBase32.Write(data)
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if err != nil {
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return fmt.Errorf("unable to write to buffer: %v", err)
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}
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return nil
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}
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// uint64ToBase32 converts a uint64 to a base32 encoded integer encoded using
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// as few 5-bit groups as possible.
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func uint64ToBase32(num uint64) []byte {
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// Return at least one group.
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if num == 0 {
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return []byte{0}
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}
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// To fit an uint64, we need at most is ceil(64 / 5) = 13 groups.
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arr := make([]byte, 13)
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i := 13
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for num > 0 {
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i--
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arr[i] = byte(num & uint64(31)) // 0b11111 in binary
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num = num >> 5
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}
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// We only return non-zero leading groups.
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return arr[i:]
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}
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