lnd.xprv/lnwallet/wallet.go
eugene 6d04f11f94
lnwallet+funding: sanitize upfront_shutdown_script
Otherwise, we would get non-standard txn's and fail to broadcast
them when cooperatively closing a channel. This wouldn't affect
funds security as no HTLCs would be active to steal. This is just
a safety measure as we should only generate standard txn's.
2021-06-11 10:46:21 -04:00

2180 lines
71 KiB
Go

package lnwallet
import (
"bytes"
"crypto/sha256"
"errors"
"fmt"
"math"
"net"
"sync"
"sync/atomic"
"github.com/btcsuite/btcd/blockchain"
"github.com/btcsuite/btcd/btcec"
"github.com/btcsuite/btcd/chaincfg"
"github.com/btcsuite/btcd/chaincfg/chainhash"
"github.com/btcsuite/btcd/txscript"
"github.com/btcsuite/btcd/wire"
"github.com/btcsuite/btcutil"
"github.com/btcsuite/btcutil/psbt"
"github.com/btcsuite/btcutil/txsort"
"github.com/davecgh/go-spew/spew"
"github.com/lightningnetwork/lnd/channeldb"
"github.com/lightningnetwork/lnd/input"
"github.com/lightningnetwork/lnd/keychain"
"github.com/lightningnetwork/lnd/lnwallet/chainfee"
"github.com/lightningnetwork/lnd/lnwallet/chanfunding"
"github.com/lightningnetwork/lnd/lnwallet/chanvalidate"
"github.com/lightningnetwork/lnd/lnwire"
"github.com/lightningnetwork/lnd/shachain"
)
const (
// The size of the buffered queue of requests to the wallet from the
// outside word.
msgBufferSize = 100
// anchorChanReservedValue is the amount we'll keep around in the
// wallet in case we have to fee bump anchor channels on force close.
// TODO(halseth): update constant to target a specific commit size at
// set fee rate.
anchorChanReservedValue = btcutil.Amount(10_000)
// maxAnchorChanReservedValue is the maximum value we'll reserve for
// anchor channel fee bumping. We cap it at 10 times the per-channel
// amount such that nodes with a high number of channels don't have to
// keep around a very large amount for the unlikely scenario that they
// all close at the same time.
maxAnchorChanReservedValue = 10 * anchorChanReservedValue
)
var (
// ErrPsbtFundingRequired is the error that is returned during the
// contribution handling process if the process should be paused for
// the construction of a PSBT outside of lnd's wallet.
ErrPsbtFundingRequired = errors.New("PSBT funding required")
// ErrReservedValueInvalidated is returned if we try to publish a
// transaction that would take the walletbalance below what we require
// to keep around to fee bump our open anchor channels.
ErrReservedValueInvalidated = errors.New("reserved wallet balance " +
"invalidated")
)
// PsbtFundingRequired is a type that implements the error interface and
// contains the information needed to construct a PSBT.
type PsbtFundingRequired struct {
// Intent is the pending PSBT funding intent that needs to be funded
// if the wrapping error is returned.
Intent *chanfunding.PsbtIntent
}
// Error returns the underlying error.
//
// NOTE: This method is part of the error interface.
func (p *PsbtFundingRequired) Error() string {
return ErrPsbtFundingRequired.Error()
}
// InitFundingReserveMsg is the first message sent to initiate the workflow
// required to open a payment channel with a remote peer. The initial required
// parameters are configurable across channels. These parameters are to be
// chosen depending on the fee climate within the network, and time value of
// funds to be locked up within the channel. Upon success a ChannelReservation
// will be created in order to track the lifetime of this pending channel.
// Outputs selected will be 'locked', making them unavailable, for any other
// pending reservations. Therefore, all channels in reservation limbo will be
// periodically timed out after an idle period in order to avoid "exhaustion"
// attacks.
type InitFundingReserveMsg struct {
// ChainHash denotes that chain to be used to ultimately open the
// target channel.
ChainHash *chainhash.Hash
// PendingChanID is the pending channel ID for this funding flow as
// used in the wire protocol.
PendingChanID [32]byte
// NodeID is the ID of the remote node we would like to open a channel
// with.
NodeID *btcec.PublicKey
// NodeAddr is the address port that we used to either establish or
// accept the connection which led to the negotiation of this funding
// workflow.
NodeAddr net.Addr
// SubtractFees should be set if we intend to spend exactly
// LocalFundingAmt when opening the channel, subtracting the fees from
// the funding output. This can be used for instance to use all our
// remaining funds to open the channel, since it will take fees into
// account.
SubtractFees bool
// LocalFundingAmt is the amount of funds requested from us for this
// channel.
LocalFundingAmt btcutil.Amount
// RemoteFundingAmnt is the amount of funds the remote will contribute
// to this channel.
RemoteFundingAmt btcutil.Amount
// CommitFeePerKw is the starting accepted satoshis/Kw fee for the set
// of initial commitment transactions. In order to ensure timely
// confirmation, it is recommended that this fee should be generous,
// paying some multiple of the accepted base fee rate of the network.
CommitFeePerKw chainfee.SatPerKWeight
// FundingFeePerKw is the fee rate in sat/kw to use for the initial
// funding transaction.
FundingFeePerKw chainfee.SatPerKWeight
// PushMSat is the number of milli-satoshis that should be pushed over
// the responder as part of the initial channel creation.
PushMSat lnwire.MilliSatoshi
// Flags are the channel flags specified by the initiator in the
// open_channel message.
Flags lnwire.FundingFlag
// MinConfs indicates the minimum number of confirmations that each
// output selected to fund the channel should satisfy.
MinConfs int32
// CommitType indicates what type of commitment type the channel should
// be using, like tweakless or anchors.
CommitType CommitmentType
// ChanFunder is an optional channel funder that allows the caller to
// control exactly how the channel funding is carried out. If not
// specified, then the default chanfunding.WalletAssembler will be
// used.
ChanFunder chanfunding.Assembler
// err is a channel in which all errors will be sent across. Will be
// nil if this initial set is successful.
//
// NOTE: In order to avoid deadlocks, this channel MUST be buffered.
err chan error
// resp is channel in which a ChannelReservation with our contributions
// filled in will be sent across this channel in the case of a
// successfully reservation initiation. In the case of an error, this
// will read a nil pointer.
//
// NOTE: In order to avoid deadlocks, this channel MUST be buffered.
resp chan *ChannelReservation
}
// fundingReserveCancelMsg is a message reserved for cancelling an existing
// channel reservation identified by its reservation ID. Cancelling a reservation
// frees its locked outputs up, for inclusion within further reservations.
type fundingReserveCancelMsg struct {
pendingFundingID uint64
// NOTE: In order to avoid deadlocks, this channel MUST be buffered.
err chan error // Buffered
}
// addContributionMsg represents a message executing the second phase of the
// channel reservation workflow. This message carries the counterparty's
// "contribution" to the payment channel. In the case that this message is
// processed without generating any errors, then channel reservation will then
// be able to construct the funding tx, both commitment transactions, and
// finally generate signatures for all our inputs to the funding transaction,
// and for the remote node's version of the commitment transaction.
type addContributionMsg struct {
pendingFundingID uint64
// TODO(roasbeef): Should also carry SPV proofs in we're in SPV mode
contribution *ChannelContribution
// NOTE: In order to avoid deadlocks, this channel MUST be buffered.
err chan error
}
// continueContributionMsg represents a message that signals that the
// interrupted funding process involving a PSBT can now be continued because the
// finalized transaction is now available.
type continueContributionMsg struct {
pendingFundingID uint64
// NOTE: In order to avoid deadlocks, this channel MUST be buffered.
err chan error
}
// addSingleContributionMsg represents a message executing the second phase of
// a single funder channel reservation workflow. This messages carries the
// counterparty's "contribution" to the payment channel. As this message is
// sent when on the responding side to a single funder workflow, no further
// action apart from storing the provided contribution is carried out.
type addSingleContributionMsg struct {
pendingFundingID uint64
contribution *ChannelContribution
// NOTE: In order to avoid deadlocks, this channel MUST be buffered.
err chan error
}
// addCounterPartySigsMsg represents the final message required to complete,
// and 'open' a payment channel. This message carries the counterparty's
// signatures for each of their inputs to the funding transaction, and also a
// signature allowing us to spend our version of the commitment transaction.
// If we're able to verify all the signatures are valid, the funding transaction
// will be broadcast to the network. After the funding transaction gains a
// configurable number of confirmations, the channel is officially considered
// 'open'.
type addCounterPartySigsMsg struct {
pendingFundingID uint64
// Should be order of sorted inputs that are theirs. Sorting is done
// in accordance to BIP-69:
// https://github.com/bitcoin/bips/blob/master/bip-0069.mediawiki.
theirFundingInputScripts []*input.Script
// This should be 1/2 of the signatures needed to successfully spend our
// version of the commitment transaction.
theirCommitmentSig input.Signature
// This channel is used to return the completed channel after the wallet
// has completed all of its stages in the funding process.
completeChan chan *channeldb.OpenChannel
// NOTE: In order to avoid deadlocks, this channel MUST be buffered.
err chan error
}
// addSingleFunderSigsMsg represents the next-to-last message required to
// complete a single-funder channel workflow. Once the initiator is able to
// construct the funding transaction, they send both the outpoint and a
// signature for our version of the commitment transaction. Once this message
// is processed we (the responder) are able to construct both commitment
// transactions, signing the remote party's version.
type addSingleFunderSigsMsg struct {
pendingFundingID uint64
// fundingOutpoint is the outpoint of the completed funding
// transaction as assembled by the workflow initiator.
fundingOutpoint *wire.OutPoint
// theirCommitmentSig are the 1/2 of the signatures needed to
// successfully spend our version of the commitment transaction.
theirCommitmentSig input.Signature
// This channel is used to return the completed channel after the wallet
// has completed all of its stages in the funding process.
completeChan chan *channeldb.OpenChannel
// NOTE: In order to avoid deadlocks, this channel MUST be buffered.
err chan error
}
// LightningWallet is a domain specific, yet general Bitcoin wallet capable of
// executing workflow required to interact with the Lightning Network. It is
// domain specific in the sense that it understands all the fancy scripts used
// within the Lightning Network, channel lifetimes, etc. However, it embeds a
// general purpose Bitcoin wallet within it. Therefore, it is also able to
// serve as a regular Bitcoin wallet which uses HD keys. The wallet is highly
// concurrent internally. All communication, and requests towards the wallet
// are dispatched as messages over channels, ensuring thread safety across all
// operations. Interaction has been designed independent of any peer-to-peer
// communication protocol, allowing the wallet to be self-contained and
// embeddable within future projects interacting with the Lightning Network.
//
// NOTE: At the moment the wallet requires a btcd full node, as it's dependent
// on btcd's websockets notifications as event triggers during the lifetime of a
// channel. However, once the chainntnfs package is complete, the wallet will
// be compatible with multiple RPC/notification services such as Electrum,
// Bitcoin Core + ZeroMQ, etc. Eventually, the wallet won't require a full-node
// at all, as SPV support is integrated into btcwallet.
type LightningWallet struct {
started int32 // To be used atomically.
shutdown int32 // To be used atomically.
nextFundingID uint64 // To be used atomically.
// Cfg is the configuration struct that will be used by the wallet to
// access the necessary interfaces and default it needs to carry on its
// duties.
Cfg Config
// WalletController is the core wallet, all non Lightning Network
// specific interaction is proxied to the internal wallet.
WalletController
// SecretKeyRing is the interface we'll use to derive any keys related
// to our purpose within the network including: multi-sig keys, node
// keys, revocation keys, etc.
keychain.SecretKeyRing
// This mutex MUST be held when performing coin selection in order to
// avoid inadvertently creating multiple funding transaction which
// double spend inputs across each other.
coinSelectMtx sync.RWMutex
// All messages to the wallet are to be sent across this channel.
msgChan chan interface{}
// Incomplete payment channels are stored in the map below. An intent
// to create a payment channel is tracked as a "reservation" within
// limbo. Once the final signatures have been exchanged, a reservation
// is removed from limbo. Each reservation is tracked by a unique
// monotonically integer. All requests concerning the channel MUST
// carry a valid, active funding ID.
fundingLimbo map[uint64]*ChannelReservation
// reservationIDs maps a pending channel ID to the reservation ID used
// as key in the fundingLimbo map. Used to easily look up a channel
// reservation given a pending channel ID.
reservationIDs map[[32]byte]uint64
limboMtx sync.RWMutex
// lockedOutPoints is a set of the currently locked outpoint. This
// information is kept in order to provide an easy way to unlock all
// the currently locked outpoints.
lockedOutPoints map[wire.OutPoint]struct{}
// fundingIntents houses all the "interception" registered by a caller
// using the RegisterFundingIntent method.
intentMtx sync.RWMutex
fundingIntents map[[32]byte]chanfunding.Intent
quit chan struct{}
wg sync.WaitGroup
// TODO(roasbeef): handle wallet lock/unlock
}
// NewLightningWallet creates/opens and initializes a LightningWallet instance.
// If the wallet has never been created (according to the passed dataDir), first-time
// setup is executed.
func NewLightningWallet(Cfg Config) (*LightningWallet, error) {
return &LightningWallet{
Cfg: Cfg,
SecretKeyRing: Cfg.SecretKeyRing,
WalletController: Cfg.WalletController,
msgChan: make(chan interface{}, msgBufferSize),
nextFundingID: 0,
fundingLimbo: make(map[uint64]*ChannelReservation),
reservationIDs: make(map[[32]byte]uint64),
lockedOutPoints: make(map[wire.OutPoint]struct{}),
fundingIntents: make(map[[32]byte]chanfunding.Intent),
quit: make(chan struct{}),
}, nil
}
// Startup establishes a connection to the RPC source, and spins up all
// goroutines required to handle incoming messages.
func (l *LightningWallet) Startup() error {
// Already started?
if atomic.AddInt32(&l.started, 1) != 1 {
return nil
}
// Start the underlying wallet controller.
if err := l.Start(); err != nil {
return err
}
l.wg.Add(1)
// TODO(roasbeef): multiple request handlers?
go l.requestHandler()
return nil
}
// Shutdown gracefully stops the wallet, and all active goroutines.
func (l *LightningWallet) Shutdown() error {
if atomic.AddInt32(&l.shutdown, 1) != 1 {
return nil
}
// Signal the underlying wallet controller to shutdown, waiting until
// all active goroutines have been shutdown.
if err := l.Stop(); err != nil {
return err
}
close(l.quit)
l.wg.Wait()
return nil
}
// ConfirmedBalance returns the current confirmed balance of a wallet account.
// This methods wraps the internal WalletController method so we're able to
// properly hold the coin select mutex while we compute the balance.
func (l *LightningWallet) ConfirmedBalance(confs int32,
account string) (btcutil.Amount, error) {
l.coinSelectMtx.Lock()
defer l.coinSelectMtx.Unlock()
return l.WalletController.ConfirmedBalance(confs, account)
}
// ListUnspentWitnessFromDefaultAccount returns all unspent outputs from the
// default wallet account which are version 0 witness programs. The 'minConfs'
// and 'maxConfs' parameters indicate the minimum and maximum number of
// confirmations an output needs in order to be returned by this method. Passing
// -1 as 'minConfs' indicates that even unconfirmed outputs should be returned.
// Using MaxInt32 as 'maxConfs' implies returning all outputs with at least
// 'minConfs'.
//
// NOTE: This method requires the global coin selection lock to be held.
func (l *LightningWallet) ListUnspentWitnessFromDefaultAccount(
minConfs, maxConfs int32) ([]*Utxo, error) {
return l.WalletController.ListUnspentWitness(
minConfs, maxConfs, DefaultAccountName,
)
}
// LockedOutpoints returns a list of all currently locked outpoint.
func (l *LightningWallet) LockedOutpoints() []*wire.OutPoint {
outPoints := make([]*wire.OutPoint, 0, len(l.lockedOutPoints))
for outPoint := range l.lockedOutPoints {
outPoint := outPoint
outPoints = append(outPoints, &outPoint)
}
return outPoints
}
// ResetReservations reset the volatile wallet state which tracks all currently
// active reservations.
func (l *LightningWallet) ResetReservations() {
l.nextFundingID = 0
l.fundingLimbo = make(map[uint64]*ChannelReservation)
l.reservationIDs = make(map[[32]byte]uint64)
for outpoint := range l.lockedOutPoints {
l.UnlockOutpoint(outpoint)
}
l.lockedOutPoints = make(map[wire.OutPoint]struct{})
}
// ActiveReservations returns a slice of all the currently active
// (non-canceled) reservations.
func (l *LightningWallet) ActiveReservations() []*ChannelReservation {
reservations := make([]*ChannelReservation, 0, len(l.fundingLimbo))
for _, reservation := range l.fundingLimbo {
reservations = append(reservations, reservation)
}
return reservations
}
// requestHandler is the primary goroutine(s) responsible for handling, and
// dispatching replies to all messages.
func (l *LightningWallet) requestHandler() {
defer l.wg.Done()
out:
for {
select {
case m := <-l.msgChan:
switch msg := m.(type) {
case *InitFundingReserveMsg:
l.handleFundingReserveRequest(msg)
case *fundingReserveCancelMsg:
l.handleFundingCancelRequest(msg)
case *addSingleContributionMsg:
l.handleSingleContribution(msg)
case *addContributionMsg:
l.handleContributionMsg(msg)
case *continueContributionMsg:
l.handleChanPointReady(msg)
case *addSingleFunderSigsMsg:
l.handleSingleFunderSigs(msg)
case *addCounterPartySigsMsg:
l.handleFundingCounterPartySigs(msg)
}
case <-l.quit:
// TODO: do some clean up
break out
}
}
}
// InitChannelReservation kicks off the 3-step workflow required to successfully
// open a payment channel with a remote node. As part of the funding
// reservation, the inputs selected for the funding transaction are 'locked'.
// This ensures that multiple channel reservations aren't double spending the
// same inputs in the funding transaction. If reservation initialization is
// successful, a ChannelReservation containing our completed contribution is
// returned. Our contribution contains all the items necessary to allow the
// counterparty to build the funding transaction, and both versions of the
// commitment transaction. Otherwise, an error occurred and a nil pointer along
// with an error are returned.
//
// Once a ChannelReservation has been obtained, two additional steps must be
// processed before a payment channel can be considered 'open'. The second step
// validates, and processes the counterparty's channel contribution. The third,
// and final step verifies all signatures for the inputs of the funding
// transaction, and that the signature we record for our version of the
// commitment transaction is valid.
func (l *LightningWallet) InitChannelReservation(
req *InitFundingReserveMsg) (*ChannelReservation, error) {
req.resp = make(chan *ChannelReservation, 1)
req.err = make(chan error, 1)
select {
case l.msgChan <- req:
case <-l.quit:
return nil, errors.New("wallet shutting down")
}
return <-req.resp, <-req.err
}
// RegisterFundingIntent allows a caller to signal to the wallet that if a
// pending channel ID of expectedID is found, then it can skip constructing a
// new chanfunding.Assembler, and instead use the specified chanfunding.Intent.
// As an example, this lets some of the parameters for funding transaction to
// be negotiated outside the regular funding protocol.
func (l *LightningWallet) RegisterFundingIntent(expectedID [32]byte,
shimIntent chanfunding.Intent) error {
l.intentMtx.Lock()
defer l.intentMtx.Unlock()
if _, ok := l.fundingIntents[expectedID]; ok {
return fmt.Errorf("pendingChanID(%x) already has intent "+
"registered", expectedID[:])
}
l.fundingIntents[expectedID] = shimIntent
return nil
}
// PsbtFundingVerify looks up a previously registered funding intent by its
// pending channel ID and tries to advance the state machine by verifying the
// passed PSBT.
func (l *LightningWallet) PsbtFundingVerify(pendingChanID [32]byte,
packet *psbt.Packet) error {
l.intentMtx.Lock()
defer l.intentMtx.Unlock()
intent, ok := l.fundingIntents[pendingChanID]
if !ok {
return fmt.Errorf("no funding intent found for "+
"pendingChannelID(%x)", pendingChanID[:])
}
psbtIntent, ok := intent.(*chanfunding.PsbtIntent)
if !ok {
return fmt.Errorf("incompatible funding intent")
}
err := psbtIntent.Verify(packet)
if err != nil {
return fmt.Errorf("error verifying PSBT: %v", err)
}
// Get the channel reservation for that corresponds to this pending
// channel ID.
l.limboMtx.Lock()
pid, ok := l.reservationIDs[pendingChanID]
if !ok {
l.limboMtx.Unlock()
return fmt.Errorf("no channel reservation found for "+
"pendingChannelID(%x)", pendingChanID[:])
}
pendingReservation, ok := l.fundingLimbo[pid]
l.limboMtx.Unlock()
if !ok {
return fmt.Errorf("no channel reservation found for "+
"reservation ID %v", pid)
}
// Now the the PSBT has been verified, we can again check whether the
// value reserved for anchor fee bumping is respected.
numAnchors, err := l.currentNumAnchorChans()
if err != nil {
return err
}
// If this commit type is an anchor channel we add that to our counter,
// but only if we are contributing funds to the channel. This is done
// to still allow incoming channels even though we have no UTXOs
// available, as in bootstrapping phases. We only count public
// channels.
isPublic := pendingReservation.partialState.ChannelFlags&lnwire.FFAnnounceChannel != 0
if pendingReservation.partialState.ChanType.HasAnchors() &&
intent.LocalFundingAmt() > 0 && isPublic {
numAnchors++
}
// We check the reserve value again, this should already have been
// checked for regular FullIntents, but now the PSBT intent is also
// populated.
return l.WithCoinSelectLock(func() error {
_, err := l.CheckReservedValue(
intent.Inputs(), intent.Outputs(), numAnchors,
)
return err
})
}
// PsbtFundingFinalize looks up a previously registered funding intent by its
// pending channel ID and tries to advance the state machine by finalizing the
// passed PSBT.
func (l *LightningWallet) PsbtFundingFinalize(pid [32]byte, packet *psbt.Packet,
rawTx *wire.MsgTx) error {
l.intentMtx.Lock()
defer l.intentMtx.Unlock()
intent, ok := l.fundingIntents[pid]
if !ok {
return fmt.Errorf("no funding intent found for "+
"pendingChannelID(%x)", pid[:])
}
psbtIntent, ok := intent.(*chanfunding.PsbtIntent)
if !ok {
return fmt.Errorf("incompatible funding intent")
}
// Either the PSBT or the raw TX must be set.
switch {
case packet != nil && rawTx == nil:
err := psbtIntent.Finalize(packet)
if err != nil {
return fmt.Errorf("error finalizing PSBT: %v", err)
}
case rawTx != nil && packet == nil:
err := psbtIntent.FinalizeRawTX(rawTx)
if err != nil {
return fmt.Errorf("error finalizing raw TX: %v", err)
}
default:
return fmt.Errorf("either a PSBT or raw TX must be specified")
}
return nil
}
// CancelFundingIntent allows a caller to cancel a previously registered
// funding intent. If no intent was found, then an error will be returned.
func (l *LightningWallet) CancelFundingIntent(pid [32]byte) error {
l.intentMtx.Lock()
defer l.intentMtx.Unlock()
intent, ok := l.fundingIntents[pid]
if !ok {
return fmt.Errorf("no funding intent found for "+
"pendingChannelID(%x)", pid[:])
}
// Give the intent a chance to clean up after itself, removing coin
// locks or similar reserved resources.
intent.Cancel()
delete(l.fundingIntents, pid)
return nil
}
// handleFundingReserveRequest processes a message intending to create, and
// validate a funding reservation request.
func (l *LightningWallet) handleFundingReserveRequest(req *InitFundingReserveMsg) {
// It isn't possible to create a channel with zero funds committed.
if req.LocalFundingAmt+req.RemoteFundingAmt == 0 {
err := ErrZeroCapacity()
req.err <- err
req.resp <- nil
return
}
// If the funding request is for a different chain than the one the
// wallet is aware of, then we'll reject the request.
if !bytes.Equal(l.Cfg.NetParams.GenesisHash[:], req.ChainHash[:]) {
err := ErrChainMismatch(
l.Cfg.NetParams.GenesisHash, req.ChainHash,
)
req.err <- err
req.resp <- nil
return
}
// If no chanFunder was provided, then we'll assume the default
// assembler, which is backed by the wallet's internal coin selection.
if req.ChanFunder == nil {
cfg := chanfunding.WalletConfig{
CoinSource: &CoinSource{l},
CoinSelectLocker: l,
CoinLocker: l,
Signer: l.Cfg.Signer,
DustLimit: DefaultDustLimit(),
}
req.ChanFunder = chanfunding.NewWalletAssembler(cfg)
}
localFundingAmt := req.LocalFundingAmt
remoteFundingAmt := req.RemoteFundingAmt
var (
fundingIntent chanfunding.Intent
err error
)
// If we've just received an inbound funding request that we have a
// registered shim intent to, then we'll obtain the backing intent now.
// In this case, we're doing a special funding workflow that allows
// more advanced constructions such as channel factories to be
// instantiated.
l.intentMtx.Lock()
fundingIntent, ok := l.fundingIntents[req.PendingChanID]
l.intentMtx.Unlock()
// Otherwise, this is a normal funding flow, so we'll use the chan
// funder in the attached request to provision the inputs/outputs
// that'll ultimately be used to construct the funding transaction.
if !ok {
// Coin selection is done on the basis of sat/kw, so we'll use
// the fee rate passed in to perform coin selection.
var err error
fundingReq := &chanfunding.Request{
RemoteAmt: req.RemoteFundingAmt,
LocalAmt: req.LocalFundingAmt,
MinConfs: req.MinConfs,
SubtractFees: req.SubtractFees,
FeeRate: req.FundingFeePerKw,
ChangeAddr: func() (btcutil.Address, error) {
return l.NewAddress(
WitnessPubKey, true, DefaultAccountName,
)
},
}
fundingIntent, err = req.ChanFunder.ProvisionChannel(
fundingReq,
)
if err != nil {
req.err <- err
req.resp <- nil
return
}
// Register the funding intent now in case we need to access it
// again later, as it's the case for the PSBT state machine for
// example.
err = l.RegisterFundingIntent(req.PendingChanID, fundingIntent)
if err != nil {
req.err <- err
req.resp <- nil
return
}
localFundingAmt = fundingIntent.LocalFundingAmt()
remoteFundingAmt = fundingIntent.RemoteFundingAmt()
}
// At this point there _has_ to be a funding intent, otherwise something
// went really wrong.
if fundingIntent == nil {
req.err <- fmt.Errorf("no funding intent present")
req.resp <- nil
return
}
// If this is a shim intent, then it may be attempting to use an
// existing set of keys for the funding workflow. In this case, we'll
// make a simple wrapper keychain.KeyRing that will proxy certain
// derivation calls to future callers.
var (
keyRing keychain.KeyRing = l.SecretKeyRing
thawHeight uint32
)
if shimIntent, ok := fundingIntent.(*chanfunding.ShimIntent); ok {
keyRing = &shimKeyRing{
KeyRing: keyRing,
ShimIntent: shimIntent,
}
// As this was a registered shim intent, we'll obtain the thaw
// height of the intent, if present at all. If this is
// non-zero, then we'll mark this as the proper channel type.
thawHeight = shimIntent.ThawHeight()
}
// Now that we have a funding intent, we'll check whether funding a
// channel using it would violate our reserved value for anchor channel
// fee bumping. We first get our current number of anchor channels.
numAnchors, err := l.currentNumAnchorChans()
if err != nil {
fundingIntent.Cancel()
req.err <- err
req.resp <- nil
return
}
// If this commit type is an anchor channel we add that to our counter,
// but only if we are contributing funds to the channel. This is done
// to still allow incoming channels even though we have no UTXOs
// available, as in bootstrapping phases. We only count public
// channels.
isPublic := req.Flags&lnwire.FFAnnounceChannel != 0
if req.CommitType == CommitmentTypeAnchorsZeroFeeHtlcTx &&
fundingIntent.LocalFundingAmt() > 0 && isPublic {
numAnchors++
}
// Check the reserved value using the inputs and outputs given by the
// intent. Not that for the PSBT intent type we don't yet have the
// funding tx ready, so this will always pass. We'll do another check
// when the PSBT has been verified.
err = l.WithCoinSelectLock(func() error {
_, err := l.CheckReservedValue(
fundingIntent.Inputs(), fundingIntent.Outputs(),
numAnchors,
)
return err
})
if err != nil {
fundingIntent.Cancel()
req.err <- err
req.resp <- nil
return
}
// The total channel capacity will be the size of the funding output we
// created plus the remote contribution.
capacity := localFundingAmt + remoteFundingAmt
id := atomic.AddUint64(&l.nextFundingID, 1)
reservation, err := NewChannelReservation(
capacity, localFundingAmt, req.CommitFeePerKw, l, id,
req.PushMSat, l.Cfg.NetParams.GenesisHash, req.Flags,
req.CommitType, req.ChanFunder, req.PendingChanID,
thawHeight,
)
if err != nil {
fundingIntent.Cancel()
req.err <- err
req.resp <- nil
return
}
err = l.initOurContribution(
reservation, fundingIntent, req.NodeAddr, req.NodeID, keyRing,
)
if err != nil {
fundingIntent.Cancel()
req.err <- err
req.resp <- nil
return
}
// Create a limbo and record entry for this newly pending funding
// request.
l.limboMtx.Lock()
l.fundingLimbo[id] = reservation
l.reservationIDs[req.PendingChanID] = id
l.limboMtx.Unlock()
// Funding reservation request successfully handled. The funding inputs
// will be marked as unavailable until the reservation is either
// completed, or canceled.
req.resp <- reservation
req.err <- nil
}
// currentNumAnchorChans returns the current number of non-private anchor
// channels the wallet should be ready to fee bump if needed.
func (l *LightningWallet) currentNumAnchorChans() (int, error) {
// Count all anchor channels that are open or pending
// open, or waiting close.
chans, err := l.Cfg.Database.FetchAllChannels()
if err != nil {
return 0, err
}
var numAnchors int
cntChannel := func(c *channeldb.OpenChannel) {
// We skip private channels, as we assume they won't be used
// for routing.
if c.ChannelFlags&lnwire.FFAnnounceChannel == 0 {
return
}
// Count anchor channels.
if c.ChanType.HasAnchors() {
numAnchors++
}
}
for _, c := range chans {
cntChannel(c)
}
// We also count pending close channels.
pendingClosed, err := l.Cfg.Database.FetchClosedChannels(
true,
)
if err != nil {
return 0, err
}
for _, c := range pendingClosed {
c, err := l.Cfg.Database.FetchHistoricalChannel(
&c.ChanPoint,
)
if err != nil {
// We don't have a guarantee that all channels re found
// in the historical channels bucket, so we continue.
walletLog.Warnf("Unable to fetch historical "+
"channel: %v", err)
continue
}
cntChannel(c)
}
return numAnchors, nil
}
// CheckReservedValue checks whether publishing a transaction with the given
// inputs and outputs would violate the value we reserve in the wallet for
// bumping the fee of anchor channels. The numAnchorChans argument should be
// set the the number of open anchor channels controlled by the wallet after
// the transaction has been published.
//
// If the reserved value is violated, the returned error will be
// ErrReservedValueInvalidated. The method will also return the current
// reserved value, both in case of success and in case of
// ErrReservedValueInvalidated.
//
// NOTE: This method should only be run with the CoinSelectLock held.
func (l *LightningWallet) CheckReservedValue(in []wire.OutPoint,
out []*wire.TxOut, numAnchorChans int) (btcutil.Amount, error) {
// Get all unspent coins in the wallet. We only care about those part of
// the wallet's default account as we know we can readily sign for those
// at any time.
witnessOutputs, err := l.ListUnspentWitnessFromDefaultAccount(
0, math.MaxInt32,
)
if err != nil {
return 0, err
}
ourInput := make(map[wire.OutPoint]struct{})
for _, op := range in {
ourInput[op] = struct{}{}
}
// When crafting a transaction with inputs from the wallet, these coins
// will usually be locked in the process, and not be returned when
// listing unspents. In this case they have already been deducted from
// the wallet balance. In case they haven't been properly locked, we
// check whether they are still listed among our unspents and deduct
// them.
var walletBalance btcutil.Amount
for _, in := range witnessOutputs {
// Spending an unlocked wallet UTXO, don't add it to the
// balance.
if _, ok := ourInput[in.OutPoint]; ok {
continue
}
walletBalance += in.Value
}
// Now we go through the outputs of the transaction, if any of the
// outputs are paying into the wallet (likely a change output), we add
// it to our final balance.
for _, txOut := range out {
_, addrs, _, err := txscript.ExtractPkScriptAddrs(
txOut.PkScript, &l.Cfg.NetParams,
)
if err != nil {
// Non-standard outputs can safely be skipped because
// they're not supported by the wallet.
continue
}
for _, addr := range addrs {
if !l.IsOurAddress(addr) {
continue
}
walletBalance += btcutil.Amount(txOut.Value)
// We break since we don't want to double count the output.
break
}
}
// We reserve a given amount for each anchor channel.
reserved := btcutil.Amount(numAnchorChans) * anchorChanReservedValue
if reserved > maxAnchorChanReservedValue {
reserved = maxAnchorChanReservedValue
}
if walletBalance < reserved {
walletLog.Debugf("Reserved value=%v above final "+
"walletbalance=%v with %d anchor channels open",
reserved, walletBalance, numAnchorChans)
return reserved, ErrReservedValueInvalidated
}
return reserved, nil
}
// CheckReservedValueTx calls CheckReservedValue with the inputs and outputs
// from the given tx, with the number of anchor channels currently open in the
// database.
//
// NOTE: This method should only be run with the CoinSelectLock held.
func (l *LightningWallet) CheckReservedValueTx(tx *wire.MsgTx) (btcutil.Amount,
error) {
numAnchors, err := l.currentNumAnchorChans()
if err != nil {
return 0, err
}
var inputs []wire.OutPoint
for _, txIn := range tx.TxIn {
inputs = append(inputs, txIn.PreviousOutPoint)
}
return l.CheckReservedValue(inputs, tx.TxOut, numAnchors)
}
// initOurContribution initializes the given ChannelReservation with our coins
// and change reserved for the channel, and derives the keys to use for this
// channel.
func (l *LightningWallet) initOurContribution(reservation *ChannelReservation,
fundingIntent chanfunding.Intent, nodeAddr net.Addr,
nodeID *btcec.PublicKey, keyRing keychain.KeyRing) error {
// Grab the mutex on the ChannelReservation to ensure thread-safety
reservation.Lock()
defer reservation.Unlock()
// At this point, if we have a funding intent, we'll use it to populate
// the existing reservation state entries for our coin selection.
if fundingIntent != nil {
if intent, ok := fundingIntent.(*chanfunding.FullIntent); ok {
for _, coin := range intent.InputCoins {
reservation.ourContribution.Inputs = append(
reservation.ourContribution.Inputs,
&wire.TxIn{
PreviousOutPoint: coin.OutPoint,
},
)
}
reservation.ourContribution.ChangeOutputs = intent.ChangeOutputs
}
reservation.fundingIntent = fundingIntent
}
reservation.nodeAddr = nodeAddr
reservation.partialState.IdentityPub = nodeID
var err error
reservation.ourContribution.MultiSigKey, err = keyRing.DeriveNextKey(
keychain.KeyFamilyMultiSig,
)
if err != nil {
return err
}
reservation.ourContribution.RevocationBasePoint, err = keyRing.DeriveNextKey(
keychain.KeyFamilyRevocationBase,
)
if err != nil {
return err
}
reservation.ourContribution.HtlcBasePoint, err = keyRing.DeriveNextKey(
keychain.KeyFamilyHtlcBase,
)
if err != nil {
return err
}
reservation.ourContribution.PaymentBasePoint, err = keyRing.DeriveNextKey(
keychain.KeyFamilyPaymentBase,
)
if err != nil {
return err
}
reservation.ourContribution.DelayBasePoint, err = keyRing.DeriveNextKey(
keychain.KeyFamilyDelayBase,
)
if err != nil {
return err
}
// With the above keys created, we'll also need to initialize our
// revocation tree state, and from that generate the per-commitment point.
producer, err := l.nextRevocationProducer(reservation, keyRing)
if err != nil {
return err
}
firstPreimage, err := producer.AtIndex(0)
if err != nil {
return err
}
reservation.ourContribution.FirstCommitmentPoint = input.ComputeCommitmentPoint(
firstPreimage[:],
)
reservation.partialState.RevocationProducer = producer
reservation.ourContribution.ChannelConstraints = l.Cfg.DefaultConstraints
return nil
}
// handleFundingReserveCancel cancels an existing channel reservation. As part
// of the cancellation, outputs previously selected as inputs for the funding
// transaction via coin selection are freed allowing future reservations to
// include them.
func (l *LightningWallet) handleFundingCancelRequest(req *fundingReserveCancelMsg) {
// TODO(roasbeef): holding lock too long
l.limboMtx.Lock()
defer l.limboMtx.Unlock()
pendingReservation, ok := l.fundingLimbo[req.pendingFundingID]
if !ok {
// TODO(roasbeef): make new error, "unknown funding state" or something
req.err <- fmt.Errorf("attempted to cancel non-existent funding state")
return
}
// Grab the mutex on the ChannelReservation to ensure thread-safety
pendingReservation.Lock()
defer pendingReservation.Unlock()
// Mark all previously locked outpoints as useable for future funding
// requests.
for _, unusedInput := range pendingReservation.ourContribution.Inputs {
delete(l.lockedOutPoints, unusedInput.PreviousOutPoint)
l.UnlockOutpoint(unusedInput.PreviousOutPoint)
}
// TODO(roasbeef): is it even worth it to keep track of unused keys?
// TODO(roasbeef): Is it possible to mark the unused change also as
// available?
delete(l.fundingLimbo, req.pendingFundingID)
pid := pendingReservation.pendingChanID
delete(l.reservationIDs, pid)
l.intentMtx.Lock()
if intent, ok := l.fundingIntents[pid]; ok {
intent.Cancel()
delete(l.fundingIntents, pendingReservation.pendingChanID)
}
l.intentMtx.Unlock()
req.err <- nil
}
// CreateCommitmentTxns is a helper function that creates the initial
// commitment transaction for both parties. This function is used during the
// initial funding workflow as both sides must generate a signature for the
// remote party's commitment transaction, and verify the signature for their
// version of the commitment transaction.
func CreateCommitmentTxns(localBalance, remoteBalance btcutil.Amount,
ourChanCfg, theirChanCfg *channeldb.ChannelConfig,
localCommitPoint, remoteCommitPoint *btcec.PublicKey,
fundingTxIn wire.TxIn, chanType channeldb.ChannelType) (
*wire.MsgTx, *wire.MsgTx, error) {
localCommitmentKeys := DeriveCommitmentKeys(
localCommitPoint, true, chanType, ourChanCfg, theirChanCfg,
)
remoteCommitmentKeys := DeriveCommitmentKeys(
remoteCommitPoint, false, chanType, ourChanCfg, theirChanCfg,
)
ourCommitTx, err := CreateCommitTx(
chanType, fundingTxIn, localCommitmentKeys, ourChanCfg,
theirChanCfg, localBalance, remoteBalance, 0,
)
if err != nil {
return nil, nil, err
}
otxn := btcutil.NewTx(ourCommitTx)
if err := blockchain.CheckTransactionSanity(otxn); err != nil {
return nil, nil, err
}
theirCommitTx, err := CreateCommitTx(
chanType, fundingTxIn, remoteCommitmentKeys, theirChanCfg,
ourChanCfg, remoteBalance, localBalance, 0,
)
if err != nil {
return nil, nil, err
}
ttxn := btcutil.NewTx(theirCommitTx)
if err := blockchain.CheckTransactionSanity(ttxn); err != nil {
return nil, nil, err
}
return ourCommitTx, theirCommitTx, nil
}
// handleContributionMsg processes the second workflow step for the lifetime of
// a channel reservation. Upon completion, the reservation will carry a
// completed funding transaction (minus the counterparty's input signatures),
// both versions of the commitment transaction, and our signature for their
// version of the commitment transaction.
func (l *LightningWallet) handleContributionMsg(req *addContributionMsg) {
l.limboMtx.Lock()
pendingReservation, ok := l.fundingLimbo[req.pendingFundingID]
l.limboMtx.Unlock()
if !ok {
req.err <- fmt.Errorf("attempted to update non-existent funding state")
return
}
// Grab the mutex on the ChannelReservation to ensure thread-safety
pendingReservation.Lock()
defer pendingReservation.Unlock()
// If UpfrontShutdownScript is set, validate that it is a valid script.
shutdown := req.contribution.UpfrontShutdown
if len(shutdown) > 0 {
// Validate the shutdown script.
if !validateUpfrontShutdown(shutdown, &l.Cfg.NetParams) {
req.err <- fmt.Errorf("invalid shutdown script")
return
}
}
// Some temporary variables to cut down on the resolution verbosity.
pendingReservation.theirContribution = req.contribution
theirContribution := req.contribution
ourContribution := pendingReservation.ourContribution
var (
chanPoint *wire.OutPoint
err error
)
// At this point, we can now construct our channel point. Depending on
// which type of intent we obtained from our chanfunding.Assembler,
// we'll carry out a distinct set of steps.
switch fundingIntent := pendingReservation.fundingIntent.(type) {
// The transaction was created outside of the wallet and might already
// be published. Nothing left to do other than using the correct
// outpoint.
case *chanfunding.ShimIntent:
chanPoint, err = fundingIntent.ChanPoint()
if err != nil {
req.err <- fmt.Errorf("unable to obtain chan point: %v", err)
return
}
pendingReservation.partialState.FundingOutpoint = *chanPoint
// The user has signaled that they want to use a PSBT to construct the
// funding transaction. Because we now have the multisig keys from both
// parties, we can create the multisig script that needs to be funded
// and then pause the process until the user supplies the PSBT
// containing the eventual funding transaction.
case *chanfunding.PsbtIntent:
if fundingIntent.PendingPsbt != nil {
req.err <- fmt.Errorf("PSBT funding already in" +
"progress")
return
}
// Now that we know our contribution, we can bind both the local
// and remote key which will be needed to calculate the multisig
// funding output in a next step.
pendingChanID := pendingReservation.pendingChanID
walletLog.Debugf("Advancing PSBT funding flow for "+
"pending_id(%x), binding keys local_key=%v, "+
"remote_key=%x", pendingChanID,
&ourContribution.MultiSigKey,
theirContribution.MultiSigKey.PubKey.SerializeCompressed())
fundingIntent.BindKeys(
&ourContribution.MultiSigKey,
theirContribution.MultiSigKey.PubKey,
)
// Exit early because we can't continue the funding flow yet.
req.err <- &PsbtFundingRequired{
Intent: fundingIntent,
}
return
case *chanfunding.FullIntent:
// Now that we know their public key, we can bind theirs as
// well as ours to the funding intent.
fundingIntent.BindKeys(
&pendingReservation.ourContribution.MultiSigKey,
theirContribution.MultiSigKey.PubKey,
)
// With our keys bound, we can now construct+sign the final
// funding transaction and also obtain the chanPoint that
// creates the channel.
fundingTx, err := fundingIntent.CompileFundingTx(
theirContribution.Inputs,
theirContribution.ChangeOutputs,
)
if err != nil {
req.err <- fmt.Errorf("unable to construct funding "+
"tx: %v", err)
return
}
chanPoint, err = fundingIntent.ChanPoint()
if err != nil {
req.err <- fmt.Errorf("unable to obtain chan "+
"point: %v", err)
return
}
// Finally, we'll populate the relevant information in our
// pendingReservation so the rest of the funding flow can
// continue as normal.
pendingReservation.fundingTx = fundingTx
pendingReservation.partialState.FundingOutpoint = *chanPoint
pendingReservation.ourFundingInputScripts = make(
[]*input.Script, 0, len(ourContribution.Inputs),
)
for _, txIn := range fundingTx.TxIn {
_, err := l.FetchInputInfo(&txIn.PreviousOutPoint)
if err != nil {
continue
}
pendingReservation.ourFundingInputScripts = append(
pendingReservation.ourFundingInputScripts,
&input.Script{
Witness: txIn.Witness,
SigScript: txIn.SignatureScript,
},
)
}
walletLog.Debugf("Funding tx for ChannelPoint(%v) "+
"generated: %v", chanPoint, spew.Sdump(fundingTx))
}
// If we landed here and didn't exit early, it means we already have
// the channel point ready. We can jump directly to the next step.
l.handleChanPointReady(&continueContributionMsg{
pendingFundingID: req.pendingFundingID,
err: req.err,
})
}
// handleChanPointReady continues the funding process once the channel point
// is known and the funding transaction can be completed.
func (l *LightningWallet) handleChanPointReady(req *continueContributionMsg) {
l.limboMtx.Lock()
pendingReservation, ok := l.fundingLimbo[req.pendingFundingID]
l.limboMtx.Unlock()
if !ok {
req.err <- fmt.Errorf("attempted to update non-existent " +
"funding state")
return
}
ourContribution := pendingReservation.ourContribution
theirContribution := pendingReservation.theirContribution
chanPoint := pendingReservation.partialState.FundingOutpoint
// If we're in the PSBT funding flow, we now should have everything that
// is needed to construct and publish the full funding transaction.
intent := pendingReservation.fundingIntent
if psbtIntent, ok := intent.(*chanfunding.PsbtIntent); ok {
// With our keys bound, we can now construct+sign the final
// funding transaction and also obtain the chanPoint that
// creates the channel.
fundingTx, err := psbtIntent.CompileFundingTx()
if err != nil {
req.err <- fmt.Errorf("unable to construct funding "+
"tx: %v", err)
return
}
chanPointPtr, err := psbtIntent.ChanPoint()
if err != nil {
req.err <- fmt.Errorf("unable to obtain chan "+
"point: %v", err)
return
}
// Finally, we'll populate the relevant information in our
// pendingReservation so the rest of the funding flow can
// continue as normal.
pendingReservation.fundingTx = fundingTx
pendingReservation.partialState.FundingOutpoint = *chanPointPtr
chanPoint = *chanPointPtr
pendingReservation.ourFundingInputScripts = make(
[]*input.Script, 0, len(ourContribution.Inputs),
)
for _, txIn := range fundingTx.TxIn {
pendingReservation.ourFundingInputScripts = append(
pendingReservation.ourFundingInputScripts,
&input.Script{
Witness: txIn.Witness,
SigScript: txIn.SignatureScript,
},
)
}
}
// Initialize an empty sha-chain for them, tracking the current pending
// revocation hash (we don't yet know the preimage so we can't add it
// to the chain).
s := shachain.NewRevocationStore()
pendingReservation.partialState.RevocationStore = s
// Store their current commitment point. We'll need this after the
// first state transition in order to verify the authenticity of the
// revocation.
chanState := pendingReservation.partialState
chanState.RemoteCurrentRevocation = theirContribution.FirstCommitmentPoint
// Create the txin to our commitment transaction; required to construct
// the commitment transactions.
fundingTxIn := wire.TxIn{
PreviousOutPoint: chanPoint,
}
// With the funding tx complete, create both commitment transactions.
localBalance := pendingReservation.partialState.LocalCommitment.LocalBalance.ToSatoshis()
remoteBalance := pendingReservation.partialState.LocalCommitment.RemoteBalance.ToSatoshis()
ourCommitTx, theirCommitTx, err := CreateCommitmentTxns(
localBalance, remoteBalance, ourContribution.ChannelConfig,
theirContribution.ChannelConfig,
ourContribution.FirstCommitmentPoint,
theirContribution.FirstCommitmentPoint, fundingTxIn,
pendingReservation.partialState.ChanType,
)
if err != nil {
req.err <- err
return
}
// With both commitment transactions constructed, generate the state
// obfuscator then use it to encode the current state number within
// both commitment transactions.
var stateObfuscator [StateHintSize]byte
if chanState.ChanType.IsSingleFunder() {
stateObfuscator = DeriveStateHintObfuscator(
ourContribution.PaymentBasePoint.PubKey,
theirContribution.PaymentBasePoint.PubKey,
)
} else {
ourSer := ourContribution.PaymentBasePoint.PubKey.SerializeCompressed()
theirSer := theirContribution.PaymentBasePoint.PubKey.SerializeCompressed()
switch bytes.Compare(ourSer, theirSer) {
case -1:
stateObfuscator = DeriveStateHintObfuscator(
ourContribution.PaymentBasePoint.PubKey,
theirContribution.PaymentBasePoint.PubKey,
)
default:
stateObfuscator = DeriveStateHintObfuscator(
theirContribution.PaymentBasePoint.PubKey,
ourContribution.PaymentBasePoint.PubKey,
)
}
}
err = initStateHints(ourCommitTx, theirCommitTx, stateObfuscator)
if err != nil {
req.err <- err
return
}
// Sort both transactions according to the agreed upon canonical
// ordering. This lets us skip sending the entire transaction over,
// instead we'll just send signatures.
txsort.InPlaceSort(ourCommitTx)
txsort.InPlaceSort(theirCommitTx)
walletLog.Debugf("Local commit tx for ChannelPoint(%v): %v",
chanPoint, spew.Sdump(ourCommitTx))
walletLog.Debugf("Remote commit tx for ChannelPoint(%v): %v",
chanPoint, spew.Sdump(theirCommitTx))
// Record newly available information within the open channel state.
chanState.FundingOutpoint = chanPoint
chanState.LocalCommitment.CommitTx = ourCommitTx
chanState.RemoteCommitment.CommitTx = theirCommitTx
// Next, we'll obtain the funding witness script, and the funding
// output itself so we can generate a valid signature for the remote
// party.
fundingIntent := pendingReservation.fundingIntent
fundingWitnessScript, fundingOutput, err := fundingIntent.FundingOutput()
if err != nil {
req.err <- fmt.Errorf("unable to obtain funding output")
return
}
// Generate a signature for their version of the initial commitment
// transaction.
ourKey := ourContribution.MultiSigKey
signDesc := input.SignDescriptor{
WitnessScript: fundingWitnessScript,
KeyDesc: ourKey,
Output: fundingOutput,
HashType: txscript.SigHashAll,
SigHashes: txscript.NewTxSigHashes(theirCommitTx),
InputIndex: 0,
}
sigTheirCommit, err := l.Cfg.Signer.SignOutputRaw(theirCommitTx, &signDesc)
if err != nil {
req.err <- err
return
}
pendingReservation.ourCommitmentSig = sigTheirCommit
req.err <- nil
}
// handleSingleContribution is called as the second step to a single funder
// workflow to which we are the responder. It simply saves the remote peer's
// contribution to the channel, as solely the remote peer will contribute any
// funds to the channel.
func (l *LightningWallet) handleSingleContribution(req *addSingleContributionMsg) {
l.limboMtx.Lock()
pendingReservation, ok := l.fundingLimbo[req.pendingFundingID]
l.limboMtx.Unlock()
if !ok {
req.err <- fmt.Errorf("attempted to update non-existent funding state")
return
}
// Grab the mutex on the channelReservation to ensure thread-safety.
pendingReservation.Lock()
defer pendingReservation.Unlock()
// TODO(roasbeef): verify sanity of remote party's parameters, fail if
// disagree
// Validate that the remote's UpfrontShutdownScript is a valid script
// if it's set.
shutdown := req.contribution.UpfrontShutdown
if len(shutdown) > 0 {
// Validate the shutdown script.
if !validateUpfrontShutdown(shutdown, &l.Cfg.NetParams) {
req.err <- fmt.Errorf("invalid shutdown script")
return
}
}
// Simply record the counterparty's contribution into the pending
// reservation data as they'll be solely funding the channel entirely.
pendingReservation.theirContribution = req.contribution
theirContribution := pendingReservation.theirContribution
chanState := pendingReservation.partialState
// Initialize an empty sha-chain for them, tracking the current pending
// revocation hash (we don't yet know the preimage so we can't add it
// to the chain).
remotePreimageStore := shachain.NewRevocationStore()
chanState.RevocationStore = remotePreimageStore
// Now that we've received their first commitment point, we'll store it
// within the channel state so we can sync it to disk once the funding
// process is complete.
chanState.RemoteCurrentRevocation = theirContribution.FirstCommitmentPoint
req.err <- nil
}
// verifyFundingInputs attempts to verify all remote inputs to the funding
// transaction.
func (l *LightningWallet) verifyFundingInputs(fundingTx *wire.MsgTx,
remoteInputScripts []*input.Script) error {
sigIndex := 0
fundingHashCache := txscript.NewTxSigHashes(fundingTx)
inputScripts := remoteInputScripts
for i, txin := range fundingTx.TxIn {
if len(inputScripts) != 0 && len(txin.Witness) == 0 {
// Attach the input scripts so we can verify it below.
txin.Witness = inputScripts[sigIndex].Witness
txin.SignatureScript = inputScripts[sigIndex].SigScript
// Fetch the alleged previous output along with the
// pkscript referenced by this input.
//
// TODO(roasbeef): when dual funder pass actual
// height-hint
//
// TODO(roasbeef): this fails for neutrino always as it
// treats the height hint as an exact birthday of the
// utxo rather than a lower bound
pkScript, err := txscript.ComputePkScript(
txin.SignatureScript, txin.Witness,
)
if err != nil {
return fmt.Errorf("cannot create script: %v", err)
}
output, err := l.Cfg.ChainIO.GetUtxo(
&txin.PreviousOutPoint,
pkScript.Script(), 0, l.quit,
)
if output == nil {
return fmt.Errorf("input to funding tx does "+
"not exist: %v", err)
}
// Ensure that the witness+sigScript combo is valid.
vm, err := txscript.NewEngine(
output.PkScript, fundingTx, i,
txscript.StandardVerifyFlags, nil,
fundingHashCache, output.Value,
)
if err != nil {
return fmt.Errorf("cannot create script "+
"engine: %s", err)
}
if err = vm.Execute(); err != nil {
return fmt.Errorf("cannot validate "+
"transaction: %s", err)
}
sigIndex++
}
}
return nil
}
// handleFundingCounterPartySigs is the final step in the channel reservation
// workflow. During this step, we validate *all* the received signatures for
// inputs to the funding transaction. If any of these are invalid, we bail,
// and forcibly cancel this funding request. Additionally, we ensure that the
// signature we received from the counterparty for our version of the commitment
// transaction allows us to spend from the funding output with the addition of
// our signature.
func (l *LightningWallet) handleFundingCounterPartySigs(msg *addCounterPartySigsMsg) {
l.limboMtx.RLock()
res, ok := l.fundingLimbo[msg.pendingFundingID]
l.limboMtx.RUnlock()
if !ok {
msg.err <- fmt.Errorf("attempted to update non-existent funding state")
return
}
// Grab the mutex on the ChannelReservation to ensure thread-safety
res.Lock()
defer res.Unlock()
// Now we can complete the funding transaction by adding their
// signatures to their inputs.
res.theirFundingInputScripts = msg.theirFundingInputScripts
inputScripts := msg.theirFundingInputScripts
// Only if we have the final funding transaction do we need to verify
// the final set of inputs. Otherwise, it may be the case that the
// channel was funded via an external wallet.
fundingTx := res.fundingTx
if res.partialState.ChanType.HasFundingTx() {
err := l.verifyFundingInputs(fundingTx, inputScripts)
if err != nil {
msg.err <- err
msg.completeChan <- nil
return
}
}
// At this point, we can also record and verify their signature for our
// commitment transaction.
res.theirCommitmentSig = msg.theirCommitmentSig
commitTx := res.partialState.LocalCommitment.CommitTx
ourKey := res.ourContribution.MultiSigKey
theirKey := res.theirContribution.MultiSigKey
// Re-generate both the witnessScript and p2sh output. We sign the
// witnessScript script, but include the p2sh output as the subscript
// for verification.
witnessScript, _, err := input.GenFundingPkScript(
ourKey.PubKey.SerializeCompressed(),
theirKey.PubKey.SerializeCompressed(),
int64(res.partialState.Capacity),
)
if err != nil {
msg.err <- err
msg.completeChan <- nil
return
}
// Next, create the spending scriptSig, and then verify that the script
// is complete, allowing us to spend from the funding transaction.
channelValue := int64(res.partialState.Capacity)
hashCache := txscript.NewTxSigHashes(commitTx)
sigHash, err := txscript.CalcWitnessSigHash(
witnessScript, hashCache, txscript.SigHashAll, commitTx,
0, channelValue,
)
if err != nil {
msg.err <- err
msg.completeChan <- nil
return
}
// Verify that we've received a valid signature from the remote party
// for our version of the commitment transaction.
if !msg.theirCommitmentSig.Verify(sigHash, theirKey.PubKey) {
msg.err <- fmt.Errorf("counterparty's commitment signature is invalid")
msg.completeChan <- nil
return
}
theirCommitSigBytes := msg.theirCommitmentSig.Serialize()
res.partialState.LocalCommitment.CommitSig = theirCommitSigBytes
// Funding complete, this entry can be removed from limbo.
l.limboMtx.Lock()
delete(l.fundingLimbo, res.reservationID)
delete(l.reservationIDs, res.pendingChanID)
l.limboMtx.Unlock()
l.intentMtx.Lock()
delete(l.fundingIntents, res.pendingChanID)
l.intentMtx.Unlock()
// As we're about to broadcast the funding transaction, we'll take note
// of the current height for record keeping purposes.
//
// TODO(roasbeef): this info can also be piped into light client's
// basic fee estimation?
_, bestHeight, err := l.Cfg.ChainIO.GetBestBlock()
if err != nil {
msg.err <- err
msg.completeChan <- nil
return
}
// As we've completed the funding process, we'll no convert the
// contribution structs into their underlying channel config objects to
// he stored within the database.
res.partialState.LocalChanCfg = res.ourContribution.toChanConfig()
res.partialState.RemoteChanCfg = res.theirContribution.toChanConfig()
// We'll also record the finalized funding txn, which will allow us to
// rebroadcast on startup in case we fail.
res.partialState.FundingTxn = fundingTx
// Set optional upfront shutdown scripts on the channel state so that they
// are persisted. These values may be nil.
res.partialState.LocalShutdownScript =
res.ourContribution.UpfrontShutdown
res.partialState.RemoteShutdownScript =
res.theirContribution.UpfrontShutdown
res.partialState.RevocationKeyLocator = res.nextRevocationKeyLoc
// Add the complete funding transaction to the DB, in its open bucket
// which will be used for the lifetime of this channel.
nodeAddr := res.nodeAddr
err = res.partialState.SyncPending(nodeAddr, uint32(bestHeight))
if err != nil {
msg.err <- err
msg.completeChan <- nil
return
}
msg.completeChan <- res.partialState
msg.err <- nil
}
// handleSingleFunderSigs is called once the remote peer who initiated the
// single funder workflow has assembled the funding transaction, and generated
// a signature for our version of the commitment transaction. This method
// progresses the workflow by generating a signature for the remote peer's
// version of the commitment transaction.
func (l *LightningWallet) handleSingleFunderSigs(req *addSingleFunderSigsMsg) {
l.limboMtx.RLock()
pendingReservation, ok := l.fundingLimbo[req.pendingFundingID]
l.limboMtx.RUnlock()
if !ok {
req.err <- fmt.Errorf("attempted to update non-existent funding state")
req.completeChan <- nil
return
}
// Grab the mutex on the ChannelReservation to ensure thread-safety
pendingReservation.Lock()
defer pendingReservation.Unlock()
chanState := pendingReservation.partialState
chanState.FundingOutpoint = *req.fundingOutpoint
fundingTxIn := wire.NewTxIn(req.fundingOutpoint, nil, nil)
// Now that we have the funding outpoint, we can generate both versions
// of the commitment transaction, and generate a signature for the
// remote node's commitment transactions.
localBalance := pendingReservation.partialState.LocalCommitment.LocalBalance.ToSatoshis()
remoteBalance := pendingReservation.partialState.LocalCommitment.RemoteBalance.ToSatoshis()
ourCommitTx, theirCommitTx, err := CreateCommitmentTxns(
localBalance, remoteBalance,
pendingReservation.ourContribution.ChannelConfig,
pendingReservation.theirContribution.ChannelConfig,
pendingReservation.ourContribution.FirstCommitmentPoint,
pendingReservation.theirContribution.FirstCommitmentPoint,
*fundingTxIn, pendingReservation.partialState.ChanType,
)
if err != nil {
req.err <- err
req.completeChan <- nil
return
}
// With both commitment transactions constructed, we can now use the
// generator state obfuscator to encode the current state number within
// both commitment transactions.
stateObfuscator := DeriveStateHintObfuscator(
pendingReservation.theirContribution.PaymentBasePoint.PubKey,
pendingReservation.ourContribution.PaymentBasePoint.PubKey,
)
err = initStateHints(ourCommitTx, theirCommitTx, stateObfuscator)
if err != nil {
req.err <- err
req.completeChan <- nil
return
}
// Sort both transactions according to the agreed upon canonical
// ordering. This ensures that both parties sign the same sighash
// without further synchronization.
txsort.InPlaceSort(ourCommitTx)
txsort.InPlaceSort(theirCommitTx)
chanState.LocalCommitment.CommitTx = ourCommitTx
chanState.RemoteCommitment.CommitTx = theirCommitTx
walletLog.Debugf("Local commit tx for ChannelPoint(%v): %v",
req.fundingOutpoint, spew.Sdump(ourCommitTx))
walletLog.Debugf("Remote commit tx for ChannelPoint(%v): %v",
req.fundingOutpoint, spew.Sdump(theirCommitTx))
channelValue := int64(pendingReservation.partialState.Capacity)
hashCache := txscript.NewTxSigHashes(ourCommitTx)
theirKey := pendingReservation.theirContribution.MultiSigKey
ourKey := pendingReservation.ourContribution.MultiSigKey
witnessScript, _, err := input.GenFundingPkScript(
ourKey.PubKey.SerializeCompressed(),
theirKey.PubKey.SerializeCompressed(), channelValue,
)
if err != nil {
req.err <- err
req.completeChan <- nil
return
}
sigHash, err := txscript.CalcWitnessSigHash(
witnessScript, hashCache, txscript.SigHashAll, ourCommitTx, 0,
channelValue,
)
if err != nil {
req.err <- err
req.completeChan <- nil
return
}
// Verify that we've received a valid signature from the remote party
// for our version of the commitment transaction.
if !req.theirCommitmentSig.Verify(sigHash, theirKey.PubKey) {
req.err <- fmt.Errorf("counterparty's commitment signature " +
"is invalid")
req.completeChan <- nil
return
}
theirCommitSigBytes := req.theirCommitmentSig.Serialize()
chanState.LocalCommitment.CommitSig = theirCommitSigBytes
// With their signature for our version of the commitment transactions
// verified, we can now generate a signature for their version,
// allowing the funding transaction to be safely broadcast.
p2wsh, err := input.WitnessScriptHash(witnessScript)
if err != nil {
req.err <- err
req.completeChan <- nil
return
}
signDesc := input.SignDescriptor{
WitnessScript: witnessScript,
KeyDesc: ourKey,
Output: &wire.TxOut{
PkScript: p2wsh,
Value: channelValue,
},
HashType: txscript.SigHashAll,
SigHashes: txscript.NewTxSigHashes(theirCommitTx),
InputIndex: 0,
}
sigTheirCommit, err := l.Cfg.Signer.SignOutputRaw(theirCommitTx, &signDesc)
if err != nil {
req.err <- err
req.completeChan <- nil
return
}
pendingReservation.ourCommitmentSig = sigTheirCommit
_, bestHeight, err := l.Cfg.ChainIO.GetBestBlock()
if err != nil {
req.err <- err
req.completeChan <- nil
return
}
// Set optional upfront shutdown scripts on the channel state so that they
// are persisted. These values may be nil.
chanState.LocalShutdownScript =
pendingReservation.ourContribution.UpfrontShutdown
chanState.RemoteShutdownScript =
pendingReservation.theirContribution.UpfrontShutdown
// Add the complete funding transaction to the DB, in it's open bucket
// which will be used for the lifetime of this channel.
chanState.LocalChanCfg = pendingReservation.ourContribution.toChanConfig()
chanState.RemoteChanCfg = pendingReservation.theirContribution.toChanConfig()
chanState.RevocationKeyLocator = pendingReservation.nextRevocationKeyLoc
err = chanState.SyncPending(pendingReservation.nodeAddr, uint32(bestHeight))
if err != nil {
req.err <- err
req.completeChan <- nil
return
}
req.completeChan <- chanState
req.err <- nil
l.limboMtx.Lock()
delete(l.fundingLimbo, req.pendingFundingID)
l.limboMtx.Unlock()
l.intentMtx.Lock()
delete(l.fundingIntents, pendingReservation.pendingChanID)
l.intentMtx.Unlock()
}
// WithCoinSelectLock will execute the passed function closure in a
// synchronized manner preventing any coin selection operations from proceeding
// while the closure is executing. This can be seen as the ability to execute a
// function closure under an exclusive coin selection lock.
func (l *LightningWallet) WithCoinSelectLock(f func() error) error {
l.coinSelectMtx.Lock()
defer l.coinSelectMtx.Unlock()
return f()
}
// DeriveStateHintObfuscator derives the bytes to be used for obfuscating the
// state hints from the root to be used for a new channel. The obfuscator is
// generated via the following computation:
//
// * sha256(initiatorKey || responderKey)[26:]
// * where both keys are the multi-sig keys of the respective parties
//
// The first 6 bytes of the resulting hash are used as the state hint.
func DeriveStateHintObfuscator(key1, key2 *btcec.PublicKey) [StateHintSize]byte {
h := sha256.New()
h.Write(key1.SerializeCompressed())
h.Write(key2.SerializeCompressed())
sha := h.Sum(nil)
var obfuscator [StateHintSize]byte
copy(obfuscator[:], sha[26:])
return obfuscator
}
// initStateHints properly sets the obfuscated state hints on both commitment
// transactions using the passed obfuscator.
func initStateHints(commit1, commit2 *wire.MsgTx,
obfuscator [StateHintSize]byte) error {
if err := SetStateNumHint(commit1, 0, obfuscator); err != nil {
return err
}
if err := SetStateNumHint(commit2, 0, obfuscator); err != nil {
return err
}
return nil
}
// ValidateChannel will attempt to fully validate a newly mined channel, given
// its funding transaction and existing channel state. If this method returns
// an error, then the mined channel is invalid, and shouldn't be used.
func (l *LightningWallet) ValidateChannel(channelState *channeldb.OpenChannel,
fundingTx *wire.MsgTx) error {
// First, we'll obtain a fully signed commitment transaction so we can
// pass into it on the chanvalidate package for verification.
channel, err := NewLightningChannel(l.Cfg.Signer, channelState, nil)
if err != nil {
return err
}
signedCommitTx, err := channel.getSignedCommitTx()
if err != nil {
return err
}
// We'll also need the multi-sig witness script itself so the
// chanvalidate package can check it for correctness against the
// funding transaction, and also commitment validity.
localKey := channelState.LocalChanCfg.MultiSigKey.PubKey
remoteKey := channelState.RemoteChanCfg.MultiSigKey.PubKey
witnessScript, err := input.GenMultiSigScript(
localKey.SerializeCompressed(),
remoteKey.SerializeCompressed(),
)
if err != nil {
return err
}
pkScript, err := input.WitnessScriptHash(witnessScript)
if err != nil {
return err
}
// Finally, we'll pass in all the necessary context needed to fully
// validate that this channel is indeed what we expect, and can be
// used.
_, err = chanvalidate.Validate(&chanvalidate.Context{
Locator: &chanvalidate.OutPointChanLocator{
ChanPoint: channelState.FundingOutpoint,
},
MultiSigPkScript: pkScript,
FundingTx: fundingTx,
CommitCtx: &chanvalidate.CommitmentContext{
Value: channel.Capacity,
FullySignedCommitTx: signedCommitTx,
},
})
if err != nil {
return err
}
return nil
}
// CoinSource is a wrapper around the wallet that implements the
// chanfunding.CoinSource interface.
type CoinSource struct {
wallet *LightningWallet
}
// NewCoinSource creates a new instance of the CoinSource wrapper struct.
func NewCoinSource(w *LightningWallet) *CoinSource {
return &CoinSource{wallet: w}
}
// ListCoins returns all UTXOs from the source that have between
// minConfs and maxConfs number of confirmations.
func (c *CoinSource) ListCoins(minConfs int32,
maxConfs int32) ([]chanfunding.Coin, error) {
utxos, err := c.wallet.ListUnspentWitnessFromDefaultAccount(
minConfs, maxConfs,
)
if err != nil {
return nil, err
}
var coins []chanfunding.Coin
for _, utxo := range utxos {
coins = append(coins, chanfunding.Coin{
TxOut: wire.TxOut{
Value: int64(utxo.Value),
PkScript: utxo.PkScript,
},
OutPoint: utxo.OutPoint,
})
}
return coins, nil
}
// CoinFromOutPoint attempts to locate details pertaining to a coin based on
// its outpoint. If the coin isn't under the control of the backing CoinSource,
// then an error should be returned.
func (c *CoinSource) CoinFromOutPoint(op wire.OutPoint) (*chanfunding.Coin, error) {
inputInfo, err := c.wallet.FetchInputInfo(&op)
if err != nil {
return nil, err
}
return &chanfunding.Coin{
TxOut: wire.TxOut{
Value: int64(inputInfo.Value),
PkScript: inputInfo.PkScript,
},
OutPoint: inputInfo.OutPoint,
}, nil
}
// shimKeyRing is a wrapper struct that's used to provide the proper multi-sig
// key for an initiated external funding flow.
type shimKeyRing struct {
keychain.KeyRing
*chanfunding.ShimIntent
}
// DeriveNextKey intercepts the normal DeriveNextKey call to a keychain.KeyRing
// instance, and supplies the multi-sig key specified by the ShimIntent. This
// allows us to transparently insert new keys into the existing funding flow,
// as these keys may not come from the wallet itself.
func (s *shimKeyRing) DeriveNextKey(keyFam keychain.KeyFamily) (keychain.KeyDescriptor, error) {
if keyFam != keychain.KeyFamilyMultiSig {
return s.KeyRing.DeriveNextKey(keyFam)
}
fundingKeys, err := s.ShimIntent.MultiSigKeys()
if err != nil {
return keychain.KeyDescriptor{}, err
}
return *fundingKeys.LocalKey, nil
}
// validateUpfrontShutdown checks whether the provided upfront_shutdown_script
// is of a valid type that we accept.
func validateUpfrontShutdown(shutdown lnwire.DeliveryAddress,
params *chaincfg.Params) bool {
// We don't need to worry about a large UpfrontShutdownScript since it
// was already checked in lnwire when decoding from the wire.
scriptClass, _, _, _ := txscript.ExtractPkScriptAddrs(shutdown, params)
switch scriptClass {
case txscript.PubKeyHashTy,
txscript.WitnessV0PubKeyHashTy,
txscript.ScriptHashTy,
txscript.WitnessV0ScriptHashTy:
// The above four types are permitted according to BOLT#02.
// Everything else is disallowed.
return true
default:
return false
}
}