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invoice_creator.go
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/
invoice_creator.go
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package lnmux
import (
"encoding/binary"
"time"
"github.com/bottlepay/lnmux/common"
"github.com/bottlepay/lnmux/types"
"github.com/btcsuite/btcd/btcec/v2"
"github.com/btcsuite/btcd/chaincfg"
"github.com/lightningnetwork/lnd/feature"
"github.com/lightningnetwork/lnd/keychain"
"github.com/lightningnetwork/lnd/lntypes"
"github.com/lightningnetwork/lnd/lnwire"
"github.com/lightningnetwork/lnd/netann"
"github.com/lightningnetwork/lnd/zpay32"
)
var byteOrder = binary.BigEndian
// virtualChannelFromNode deterministically derives a short channel id for
// multiplexer for a node pubkey.
func virtualChannelFromNode(key common.PubKey) uint64 {
var b [8]byte
// Take the final bytes of the key.
copy(b[:], key[common.PubKeySize-8:])
// Force the high bit to make sure there are no collisions with real
// channels.
b[0] |= 1 << 7
return byteOrder.Uint64(b[:])
}
type InvoiceCreatorConfig struct {
KeyRing keychain.SecretKeyRing
GwPubKeys []common.PubKey
ActiveNetParams *chaincfg.Params
// RoutingPolicy is the policy that is used for the hop hints.
RoutingPolicy RoutingPolicy
}
type InvoiceCreator struct {
keyRing keychain.SecretKeyRing
gwPubKeys []*btcec.PublicKey
activeNetParams *chaincfg.Params
idKeyDesc keychain.KeyDescriptor
routingPolicy RoutingPolicy
}
func NewInvoiceCreator(cfg *InvoiceCreatorConfig) (*InvoiceCreator, error) {
idKeyDesc, err := cfg.KeyRing.DeriveKey(
keychain.KeyLocator{
Family: keychain.KeyFamilyNodeKey,
Index: 0,
},
)
if err != nil {
return nil, err
}
var parsedPubKeys []*btcec.PublicKey
for _, pubKey := range cfg.GwPubKeys {
parsedPubKey, err := btcec.ParsePubKey(pubKey[:])
if err != nil {
return nil, err
}
parsedPubKeys = append(parsedPubKeys, parsedPubKey)
}
return &InvoiceCreator{
gwPubKeys: parsedPubKeys,
activeNetParams: cfg.ActiveNetParams,
keyRing: cfg.KeyRing,
idKeyDesc: idKeyDesc,
routingPolicy: cfg.RoutingPolicy,
}, nil
}
func (c *InvoiceCreator) NodePubKeys() []*btcec.PublicKey {
return c.gwPubKeys
}
func (c *InvoiceCreator) Network() *chaincfg.Params {
return c.activeNetParams
}
func (c *InvoiceCreator) PubKey() *btcec.PublicKey {
key, err := c.keyRing.DeriveKey(keychain.KeyLocator{})
if err != nil {
panic(err)
}
return key.PubKey
}
// TODO: Add description hash.
func (c *InvoiceCreator) Create(amtMSat int64, expiry time.Duration,
memo string, descHash *lntypes.Hash, cltvDelta uint64) (
*Invoice, lntypes.Preimage, error) {
creationDate := time.Now()
// Get features.
featureMgr, err := feature.NewManager(feature.Config{})
if err != nil {
return nil, lntypes.Preimage{}, err
}
nodeKeySigner := keychain.NewPubKeyMessageSigner(
c.idKeyDesc.PubKey, c.idKeyDesc.KeyLocator, c.keyRing,
)
nodeSigner := netann.NewNodeSigner(nodeKeySigner)
privKey, err := c.keyRing.DerivePrivKey(c.idKeyDesc)
if err != nil {
return nil, lntypes.Preimage{}, err
}
expiryTime := creationDate.Add(expiry)
paymentAddr, preimage, err := encodeStatelessData(
privKey.Serialize(), amtMSat, expiryTime,
)
if err != nil {
return nil, lntypes.Preimage{}, err
}
paymentHash := preimage.Hash()
// TODO: Optionally we could encrypt the payment metadata here, just like
// rust-lightning does:
// https://github.com/lightningdevkit/rust-lightning/blob/a600eee87c96ee8865402e86bb1865011bf2d2de/lightning/src/ln/inbound_payment.rs#L166
//
// Background:
// https://github.com/lightningdevkit/rust-lightning/issues/1171#issuecomment-1162817360
// We also create an encoded payment request which allows the
// caller to compactly send the invoice to the payer. We'll create a
// list of options to be added to the encoded payment request. For now
// we only support the required fields description/description_hash,
// expiry, fallback address, and the amount field.
var options []func(*zpay32.Invoice)
// We only include the amount in the invoice if it is greater than 0.
// By not including the amount, we enable the creation of invoices that
// allow the payee to specify the amount of satoshis they wish to send.
if amtMSat > 0 {
options = append(options,
zpay32.Amount(lnwire.MilliSatoshi(amtMSat)),
)
}
options = append(options, zpay32.Expiry(expiry))
// Use the memo field as the description if it's not empty.
// Otherwise, we could have the error "both description and description hash set" in zpay32.NewInvoice
// even if `memo` is empty.
// If 'descHash' is nil, we need to add an empty description to the invoice.
// Otherwise, zpay32.NewInvoice will return the error 'neither description nor description hash set'.
if len(memo) > 0 || descHash == nil {
options = append(options, zpay32.Description(memo))
}
if descHash != nil {
options = append(options, zpay32.DescriptionHash(*descHash))
}
options = append(options, zpay32.CLTVExpiry(cltvDelta))
// Add virtual hop hints.
for _, gwPubKey := range c.gwPubKeys {
pubKey := common.NewPubKeyFromKey(gwPubKey)
virtualChannel := virtualChannelFromNode(pubKey)
hopHint := zpay32.HopHint{
NodeID: gwPubKey,
ChannelID: virtualChannel,
FeeBaseMSat: uint32(c.routingPolicy.FeeBaseMsat),
FeeProportionalMillionths: uint32(c.routingPolicy.FeeRatePpm),
CLTVExpiryDelta: uint16(c.routingPolicy.CltvDelta),
}
options = append(options, zpay32.RouteHint([]zpay32.HopHint{hopHint}))
}
// Set our desired invoice features and add them to our list of options.
invoiceFeatures := featureMgr.Get(feature.SetInvoice)
options = append(options, zpay32.Features(invoiceFeatures))
// Set the payment address.
options = append(options, zpay32.PaymentAddr(paymentAddr))
// Create and encode the payment request as a bech32 (zpay32) string.
payReq, err := zpay32.NewInvoice(
c.activeNetParams, paymentHash, creationDate, options...,
)
if err != nil {
return nil, lntypes.Preimage{}, err
}
payReqString, err := payReq.Encode(zpay32.MessageSigner{
SignCompact: func(msg []byte) ([]byte, error) {
return nodeSigner.SignMessageCompact(msg, false)
},
})
if err != nil {
return nil, lntypes.Preimage{}, err
}
newInvoice := &Invoice{
CreationDate: creationDate,
PaymentRequest: payReqString,
InvoiceCreationData: types.InvoiceCreationData{
Value: lnwire.MilliSatoshi(amtMSat),
PaymentPreimage: preimage,
PaymentAddr: paymentAddr,
},
}
return newInvoice, preimage, nil
}