Merge pull request #1026 from Roasbeef/link-sig-errors

htlcswitch+lnwallet: ensure the Error is sent to remote peer before d/c, add detailed err for htlc sig rejection

htlcswitch/interfaces.go

@@ -111,8 +111,10 @@ type ChannelLink interface {
 // Peer is an interface which represents the remote lightning node inside our
 // system.
 type Peer interface {
-	// SendMessage sends message to remote peer.
-	SendMessage(lnwire.Message) error
+	// SendMessage sends message to remote peer. The second argument
+	// denotes if the method should block until the message has been sent
+	// to the remote peer.
+	SendMessage(msg lnwire.Message, sync bool) error
 
 	// WipeChannel removes the channel uniquely identified by its channel
 	// point from all indexes associated with the peer.

htlcswitch/link.go

@@ -483,7 +483,7 @@ func (l *channelLink) syncChanStates() error {
 		return fmt.Errorf("unable to generate chan sync message for "+
 			"ChannelPoint(%v)", l.channel.ChannelPoint())
 	}
-	if err := l.cfg.Peer.SendMessage(localChanSyncMsg); err != nil {
+	if err := l.cfg.Peer.SendMessage(localChanSyncMsg, false); err != nil {
 		return fmt.Errorf("Unable to send chan sync message for "+
 			"ChannelPoint(%v)", l.channel.ChannelPoint())
 	}
@@ -525,7 +525,7 @@ func (l *channelLink) syncChanStates() error {
 			fundingLockedMsg := lnwire.NewFundingLocked(
 				l.ChanID(), nextRevocation,
 			)
-			err = l.cfg.Peer.SendMessage(fundingLockedMsg)
+			err = l.cfg.Peer.SendMessage(fundingLockedMsg, false)
 			if err != nil {
 				return fmt.Errorf("unable to re-send "+
 					"FundingLocked: %v", err)
@@ -575,7 +575,7 @@ func (l *channelLink) syncChanStates() error {
 		// immediately so we return to a synchronized state as soon as
 		// possible.
 		for _, msg := range msgsToReSend {
-			l.cfg.Peer.SendMessage(msg)
+			l.cfg.Peer.SendMessage(msg, false)
 		}
 
 	case <-l.quit:
@@ -1058,7 +1058,7 @@ func (l *channelLink) handleDownStreamPkt(pkt *htlcPacket, isReProcess bool) {
 		l.openedCircuits = append(l.openedCircuits, pkt.inKey())
 		l.keystoneBatch = append(l.keystoneBatch, pkt.keystone())
 
-		l.cfg.Peer.SendMessage(htlc)
+		l.cfg.Peer.SendMessage(htlc, false)
 
 	case *lnwire.UpdateFulfillHTLC:
 		// An HTLC we forward to the switch has just settled somewhere
@@ -1090,7 +1090,7 @@ func (l *channelLink) handleDownStreamPkt(pkt *htlcPacket, isReProcess bool) {
 
 		// Then we send the HTLC settle message to the connected peer
 		// so we can continue the propagation of the settle message.
-		l.cfg.Peer.SendMessage(htlc)
+		l.cfg.Peer.SendMessage(htlc, false)
 		isSettle = true
 
 	case *lnwire.UpdateFailHTLC:
@@ -1122,7 +1122,7 @@ func (l *channelLink) handleDownStreamPkt(pkt *htlcPacket, isReProcess bool) {
 
 		// Finally, we send the HTLC message to the peer which
 		// initially created the HTLC.
-		l.cfg.Peer.SendMessage(htlc)
+		l.cfg.Peer.SendMessage(htlc, false)
 		isSettle = true
 	}
 
@@ -1240,11 +1240,22 @@ func (l *channelLink) handleUpstreamMsg(msg lnwire.Message) {
 			// direct error.
 			//
 			// TODO(roasbeef): force close chan
-			if _, ok := err.(*lnwallet.InvalidCommitSigError); ok {
-				l.cfg.Peer.SendMessage(&lnwire.Error{
+			var sendErr bool
+			switch err.(type) {
+			case *lnwallet.InvalidCommitSigError:
+				sendErr = true
+			case *lnwallet.InvalidHtlcSigError:
+				sendErr = true
+			}
+			if sendErr {
+				err := l.cfg.Peer.SendMessage(&lnwire.Error{
 					ChanID: l.ChanID(),
 					Data:   []byte(err.Error()),
-				})
+				}, true)
+				if err != nil {
+					l.errorf("unable to send msg to "+
+						"remote peer: %v", err)
+				}
 			}
 
 			l.fail("ChannelPoint(%v): unable to accept new "+
@@ -1260,7 +1271,7 @@ func (l *channelLink) handleUpstreamMsg(msg lnwire.Message) {
 			log.Errorf("unable to revoke commitment: %v", err)
 			return
 		}
-		l.cfg.Peer.SendMessage(nextRevocation)
+		l.cfg.Peer.SendMessage(nextRevocation, false)
 
 		// Since we just revoked our commitment, we may have a new set
 		// of HTLC's on our commitment, so we'll send them over our
@@ -1288,7 +1299,7 @@ func (l *channelLink) handleUpstreamMsg(msg lnwire.Message) {
 
 		// If both commitment chains are fully synced from our PoV,
 		// then we don't need to reply with a signature as both sides
-		// already have a commitment with the latest accepted l.
+		// already have a commitment with the latest accepted.
 		if l.channel.FullySynced() {
 			return
 		}
@@ -1457,7 +1468,7 @@ func (l *channelLink) updateCommitTx() error {
 		CommitSig: theirCommitSig,
 		HtlcSigs:  htlcSigs,
 	}
-	l.cfg.Peer.SendMessage(commitSig)
+	l.cfg.Peer.SendMessage(commitSig, false)
 
 	// We've just initiated a state transition, attempt to stop the
 	// logCommitTimer. If the timer already ticked, then we'll consume the
@@ -1665,7 +1676,7 @@ func (l *channelLink) updateChannelFee(feePerKw lnwallet.SatPerKWeight) error {
 	// We'll then attempt to send a new UpdateFee message, and also lock it
 	// in immediately by triggering a commitment update.
 	msg := lnwire.NewUpdateFee(l.ChanID(), uint32(feePerKw))
-	if err := l.cfg.Peer.SendMessage(msg); err != nil {
+	if err := l.cfg.Peer.SendMessage(msg, false); err != nil {
 		return err
 	}
 	return l.updateCommitTx()
@@ -2043,7 +2054,7 @@ func (l *channelLink) processRemoteAdds(fwdPkg *channeldb.FwdPkg,
 				ChanID:          l.ChanID(),
 				ID:              pd.HtlcIndex,
 				PaymentPreimage: preimage,
-			})
+			}, false)
 			needUpdate = true
 
 		// There are additional channels left within this route. So
@@ -2364,7 +2375,7 @@ func (l *channelLink) sendHTLCError(htlcIndex uint64, failure lnwire.FailureMess
 		ChanID: l.ChanID(),
 		ID:     htlcIndex,
 		Reason: reason,
-	})
+	}, false)
 }
 
 // sendMalformedHTLCError helper function which sends the malformed HTLC update
@@ -2384,7 +2395,7 @@ func (l *channelLink) sendMalformedHTLCError(htlcIndex uint64,
 		ID:           htlcIndex,
 		ShaOnionBlob: shaOnionBlob,
 		FailureCode:  code,
-	})
+	}, false)
 }
 
 // fail helper function which is used to encapsulate the action necessary for

htlcswitch/link_test.go

@@ -1392,7 +1392,7 @@ type mockPeer struct {
 	quit     chan struct{}
 }
 
-func (m *mockPeer) SendMessage(msg lnwire.Message) error {
+func (m *mockPeer) SendMessage(msg lnwire.Message, sync bool) error {
 	select {
 	case m.sentMsgs <- msg:
 	case <-m.quit:

htlcswitch/mock.go

@@ -447,7 +447,7 @@ func (s *mockServer) intersect(f messageInterceptor) {
 	s.interceptorFuncs = append(s.interceptorFuncs, f)
 }
 
-func (s *mockServer) SendMessage(message lnwire.Message) error {
+func (s *mockServer) SendMessage(message lnwire.Message, sync bool) error {
 
 	select {
 	case s.messages <- message:

lnwallet/channel.go

@@ -1881,8 +1881,9 @@ func NewBreachRetribution(chanState *channeldb.OpenChannel, stateNum uint64,
 	if err != nil {
 		return nil, err
 	}
-	commitmentSecret, commitmentPoint := btcec.PrivKeyFromBytes(btcec.S256(),
-		revocationPreimage[:])
+	commitmentSecret, commitmentPoint := btcec.PrivKeyFromBytes(
+		btcec.S256(), revocationPreimage[:],
+	)
 
 	// With the commitment point generated, we can now generate the four
 	// keys we'll need to reconstruct the commitment state,
@@ -1893,8 +1894,9 @@ func NewBreachRetribution(chanState *channeldb.OpenChannel, stateNum uint64,
 	// number so we can have the proper witness script to sign and include
 	// within the final witness.
 	remoteDelay := uint32(chanState.RemoteChanCfg.CsvDelay)
-	remotePkScript, err := commitScriptToSelf(remoteDelay, keyRing.DelayKey,
-		keyRing.RevocationKey)
+	remotePkScript, err := commitScriptToSelf(
+		remoteDelay, keyRing.DelayKey, keyRing.RevocationKey,
+	)
 	if err != nil {
 		return nil, err
 	}
@@ -1999,10 +2001,10 @@ func NewBreachRetribution(chanState *channeldb.OpenChannel, stateNum uint64,
 				return nil, err
 			}
 
-			// Otherwise, is this was an outgoing HTLC that we sent, then
-			// from the PoV of the remote commitment state, they're the
-			// receiver of this HTLC.
 		} else {
+			// Otherwise, is this was an outgoing HTLC that we
+			// sent, then from the PoV of the remote commitment
+			// state, they're the receiver of this HTLC.
 			htlcScript, err = receiverHTLCScript(
 				htlc.RefundTimeout, keyRing.LocalHtlcKey,
 				keyRing.RemoteHtlcKey, keyRing.RevocationKey,
@@ -2582,9 +2584,11 @@ func genRemoteHtlcSigJobs(keyRing *CommitmentKeyRing,
 			Hash:  txHash,
 			Index: uint32(htlc.remoteOutputIndex),
 		}
-		sigJob.tx, err = createHtlcTimeoutTx(op, outputAmt,
-			htlc.Timeout, uint32(remoteChanCfg.CsvDelay),
-			keyRing.RevocationKey, keyRing.DelayKey)
+		sigJob.tx, err = createHtlcTimeoutTx(
+			op, outputAmt, htlc.Timeout,
+			uint32(remoteChanCfg.CsvDelay),
+			keyRing.RevocationKey, keyRing.DelayKey,
+		)
 		if err != nil {
 			return nil, nil, err
 		}
@@ -2632,9 +2636,10 @@ func genRemoteHtlcSigJobs(keyRing *CommitmentKeyRing,
 			Hash:  txHash,
 			Index: uint32(htlc.remoteOutputIndex),
 		}
-		sigJob.tx, err = createHtlcSuccessTx(op, outputAmt,
-			uint32(remoteChanCfg.CsvDelay), keyRing.RevocationKey,
-			keyRing.DelayKey)
+		sigJob.tx, err = createHtlcSuccessTx(
+			op, outputAmt, uint32(remoteChanCfg.CsvDelay),
+			keyRing.RevocationKey, keyRing.DelayKey,
+		)
 		if err != nil {
 			return nil, nil, err
 		}
@@ -3483,20 +3488,23 @@ func genHtlcSigValidationJobs(localCommitmentView *commitment,
 	i := 0
 	for index := range localCommitmentView.txn.TxOut {
 		var (
-			sigHash func() ([]byte, error)
-			sig     *btcec.Signature
-			err     error
+			htlcIndex uint64
+			sigHash   func() ([]byte, error)
+			sig       *btcec.Signature
+			err       error
 		)
 
 		outputIndex := int32(index)
 		switch {
 
-		// If this output index is found within the incoming HTLC index,
-		// then this means that we need to generate an HTLC success
-		// transaction in order to validate the signature.
+		// If this output index is found within the incoming HTLC
+		// index, then this means that we need to generate an HTLC
+		// success transaction in order to validate the signature.
 		case localCommitmentView.incomingHTLCIndex[outputIndex] != nil:
 			htlc := localCommitmentView.incomingHTLCIndex[outputIndex]
 
+			htlcIndex = htlc.HtlcIndex
+
 			sigHash = func() ([]byte, error) {
 				op := wire.OutPoint{
 					Hash:  txHash,
@@ -3547,6 +3555,8 @@ func genHtlcSigValidationJobs(localCommitmentView *commitment,
 		case localCommitmentView.outgoingHTLCIndex[outputIndex] != nil:
 			htlc := localCommitmentView.outgoingHTLCIndex[outputIndex]
 
+			htlcIndex = htlc.HtlcIndex
+
 			sigHash = func() ([]byte, error) {
 				op := wire.OutPoint{
 					Hash:  txHash,
@@ -3598,9 +3608,10 @@ func genHtlcSigValidationJobs(localCommitmentView *commitment,
 		}
 
 		verifyJobs = append(verifyJobs, verifyJob{
-			pubKey:  keyRing.RemoteHtlcKey,
-			sig:     sig,
-			sigHash: sigHash,
+			htlcIndex: htlcIndex,
+			pubKey:    keyRing.RemoteHtlcKey,
+			sig:       sig,
+			sigHash:   sigHash,
 		})
 
 		i++
@@ -3617,7 +3628,7 @@ func genHtlcSigValidationJobs(localCommitmentView *commitment,
 }
 
 // InvalidCommitSigError is a struct that implements the error interface to
-// report a failure to validation a commitment signature for a remote peer.
+// report a failure to validate a commitment signature for a remote peer.
 // We'll use the items in this struct to generate a rich error message for the
 // remote peer when we receive an invalid signature from it. Doing so can
 // greatly aide in debugging cross implementation issues.
@@ -3635,7 +3646,7 @@ type InvalidCommitSigError struct {
 // caused an invalid commitment signature.
 func (i *InvalidCommitSigError) Error() string {
 	return fmt.Sprintf("rejected commitment: commit_height=%v, "+
-		"invalid_sig=%x, commit_tx=%x, sig_hash=%x", i.commitHeight,
+		"invalid_commit_sig=%x, commit_tx=%x, sig_hash=%x", i.commitHeight,
 		i.commitSig[:], i.commitTx, i.sigHash[:])
 }
 
@@ -3643,6 +3654,35 @@ func (i *InvalidCommitSigError) Error() string {
 // error interface.
 var _ error = (*InvalidCommitSigError)(nil)
 
+// InvalidCommitSigError is a struc that implements the error interface to
+// report a failure to validate an htlc signature from a remote peer. We'll use
+// the items in this struct to generate a rich error message for the remote
+// peer when we receive an invalid signature from it. Doing so can greatly aide
+// in debugging across implementation issues.
+type InvalidHtlcSigError struct {
+	commitHeight uint64
+
+	htlcSig []byte
+
+	htlcIndex uint64
+
+	sigHash []byte
+
+	commitTx []byte
+}
+
+// Error returns a detailed error string including the exact transaction that
+// caused an invalid htlc signature.
+func (i *InvalidHtlcSigError) Error() string {
+	return fmt.Sprintf("rejected commitment: commit_height=%v, "+
+		"invalid_htlc_sig=%x, commit_tx=%x, sig_hash=%x", i.commitHeight,
+		i.htlcSig, i.commitTx, i.sigHash[:])
+}
+
+// A compile time flag to ensure that InvalidCommitSigError implements the
+// error interface.
+var _ error = (*InvalidCommitSigError)(nil)
+
 // ReceiveNewCommitment process a signature for a new commitment state sent by
 // the remote party. This method should be called in response to the
 // remote party initiating a new change, or when the remote party sends a
@@ -3772,10 +3812,30 @@ func (lc *LightningChannel) ReceiveNewCommitment(commitSig lnwire.Sig,
 		// In the case that a single signature is invalid, we'll exit
 		// early and cancel all the outstanding verification jobs.
 		select {
-		case err := <-verifyResps:
-			if err != nil {
+		case htlcErr := <-verifyResps:
+			if htlcErr != nil {
 				close(cancelChan)
-				return fmt.Errorf("invalid htlc signature: %v", err)
+
+				sig, err := lnwire.NewSigFromSignature(
+					htlcErr.sig,
+				)
+				if err != nil {
+					return err
+				}
+				sigHash, err := htlcErr.sigHash()
+				if err != nil {
+					return err
+				}
+
+				var txBytes bytes.Buffer
+				localCommitTx.Serialize(&txBytes)
+				return &InvalidHtlcSigError{
+					commitHeight: nextHeight,
+					htlcSig:      sig.ToSignatureBytes(),
+					htlcIndex:    htlcErr.htlcIndex,
+					sigHash:      sigHash,
+					commitTx:     txBytes.Bytes(),
+				}
 			}
 		case <-lc.quit:
 			return fmt.Errorf("channel shutting down")

lnwallet/sigpool.go

@@ -41,6 +41,10 @@ type verifyJob struct {
 	// passed signature is known to have signed.
 	sigHash func() ([]byte, error)
 
+	// htlcIndex is the index of the HTLC from the PoV of the remote
+	// party's update log.
+	htlcIndex uint64
+
 	// cancel is a channel that should be closed if the caller wishes to
 	// cancel all pending verification jobs part of a single batch. This
 	// channel is to be closed in the case that a single signature in a
@@ -52,7 +56,16 @@ type verifyJob struct {
 	// is to be sent over. In the see that the signature is valid, a nil
 	// error will be passed. Otherwise, a concrete error detailing the
 	// issue will be passed.
-	errResp chan error
+	errResp chan *htlcIndexErr
+}
+
+// verifyJobErr is a special type of error that also includes a pointer to the
+// original validation job. Ths error message allows us to craft more detailed
+// errors at upper layers.
+type htlcIndexErr struct {
+	error
+
+	*verifyJob
 }
 
 // signJob is a job sent to the sigPool to generate a valid signature according
@@ -69,7 +82,8 @@ type signJob struct {
 	// proper sighash for the input to be signed.
 	tx *wire.MsgTx
 
-	// outputIndex...
+	// outputIndex is the output index of the HTLC on the commitment
+	// transaction being signed.
 	outputIndex int32
 
 	// cancel is a channel that should be closed if the caller wishes to
@@ -216,7 +230,10 @@ func (s *sigPool) poolWorker() {
 			sigHash, err := verifyMsg.sigHash()
 			if err != nil {
 				select {
-				case verifyMsg.errResp <- err:
+				case verifyMsg.errResp <- &htlcIndexErr{
+					error:     err,
+					verifyJob: &verifyMsg,
+				}:
 					continue
 				case <-verifyMsg.cancel:
 					continue
@@ -229,7 +246,10 @@ func (s *sigPool) poolWorker() {
 				err := fmt.Errorf("invalid signature "+
 					"sighash: %x, sig: %x", sigHash, rawSig.Serialize())
 				select {
-				case verifyMsg.errResp <- err:
+				case verifyMsg.errResp <- &htlcIndexErr{
+					error:     err,
+					verifyJob: &verifyMsg,
+				}:
 				case <-verifyMsg.cancel:
 				case <-s.quit:
 					return
@@ -272,9 +292,9 @@ func (s *sigPool) SubmitSignBatch(signJobs []signJob) {
 // allows the caller to cancel all pending jobs in the case that they wish to
 // bail early.
 func (s *sigPool) SubmitVerifyBatch(verifyJobs []verifyJob,
-	cancelChan chan struct{}) <-chan error {
+	cancelChan chan struct{}) <-chan *htlcIndexErr {
 
-	errChan := make(chan error, len(verifyJobs))
+	errChan := make(chan *htlcIndexErr, len(verifyJobs))
 
 	for _, job := range verifyJobs {
 		job.cancel = cancelChan

peer.go

@@ -1874,10 +1874,23 @@ func (p *peer) sendInitMsg() error {
 	return p.writeMessage(msg)
 }
 
-// SendMessage queues a message for sending to the target peer.
-func (p *peer) SendMessage(msg lnwire.Message) error {
-	p.queueMsg(msg, nil)
-	return nil
+// SendMessage sends message to remote peer. The second argument denotes if the
+// method should block until the message has been sent to the remote peer.
+func (p *peer) SendMessage(msg lnwire.Message, sync bool) error {
+	if !sync {
+		p.queueMsg(msg, nil)
+		return nil
+	}
+
+	errChan := make(chan error, 1)
+	p.queueMsg(msg, errChan)
+
+	select {
+	case err := <-errChan:
+		return err
+	case <-p.quit:
+		return fmt.Errorf("peer shutting down")
+	}
 }
 
 // PubKey returns the pubkey of the peer in compressed serialized format.