funding: only send know errors across wire

This commit changes the failFundingFlow to accept an error, which will
only be sent to the remote the peer if it is among the
ReservationErrors or ErrorCode. This is done to ensure we don't send
errors that contain information we don't want to leak.

fundingmanager.go

@@ -689,21 +689,40 @@ func (f *fundingManager) CancelPeerReservations(nodePub [33]byte) {
 }
 
 // failFundingFlow will fail the active funding flow with the target peer,
-// identified by its unique temporary channel ID. This method is send an error
+// identified by its unique temporary channel ID. This method will send an
-// to the remote peer, and also remove the reservation from our set of pending
+// error to the remote peer, and also remove the reservation from our set of
-// reservations.
+// pending reservations.
 //
 // TODO(roasbeef): if peer disconnects, and haven't yet broadcast funding
 // transaction, then all reservations should be cleared.
 func (f *fundingManager) failFundingFlow(peer *btcec.PublicKey,
-	tempChanID [32]byte, msg []byte) {
+	tempChanID [32]byte, fundingErr error) {
+
+	// We only send the exact error if it is part of out whitelisted set of
+	// errors (lnwire.ErrorCode or lnwallet.ReservationError).
+	var msg lnwire.ErrorData
+	switch e := fundingErr.(type) {
+
+	// Let the actual error message be sent to the remote.
+	case lnwallet.ReservationError:
+		msg = lnwire.ErrorData(e.Error())
+
+	// Send the status code.
+	case lnwire.ErrorCode:
+		msg = lnwire.ErrorData{byte(e)}
+
+	// We just send a generic error.
+	default:
+		msg = lnwire.ErrorData("funding failed due to internal error")
+	}
 
 	errMsg := &lnwire.Error{
 		ChanID: tempChanID,
 		Data:   msg,
 	}
 
-	fndgLog.Errorf("Failing funding flow: %v", spew.Sdump(errMsg))
+	fndgLog.Errorf("Failing funding flow: %v (%v)", fundingErr,
+		spew.Sdump(errMsg))
 
 	if _, err := f.cancelReservationCtx(peer, tempChanID); err != nil {
 		fndgLog.Errorf("unable to cancel reservation: %v", err)
@@ -819,8 +838,7 @@ func (f *fundingManager) handleFundingOpen(fmsg *fundingOpenMsg) {
 	if len(f.activeReservations[peerIDKey]) >= cfg.MaxPendingChannels {
 		f.failFundingFlow(
 			fmsg.peerAddress.IdentityKey, fmsg.msg.PendingChannelID,
-			lnwire.ErrorData{byte(lnwire.ErrMaxPendingChannels)},
+			lnwire.ErrMaxPendingChannels)
-		)
 		return
 	}
 
@@ -834,8 +852,7 @@ func (f *fundingManager) handleFundingOpen(fmsg *fundingOpenMsg) {
 		}
 		f.failFundingFlow(
 			fmsg.peerAddress.IdentityKey, fmsg.msg.PendingChannelID,
-			lnwire.ErrorData{byte(lnwire.ErrSynchronizingChain)},
+			lnwire.ErrSynchronizingChain)
-		)
 		return
 	}
 
@@ -844,8 +861,7 @@ func (f *fundingManager) handleFundingOpen(fmsg *fundingOpenMsg) {
 	if msg.FundingAmount > maxFundingAmount {
 		f.failFundingFlow(
 			fmsg.peerAddress.IdentityKey, fmsg.msg.PendingChannelID,
-			lnwire.ErrorData{byte(lnwire.ErrChanTooLarge)},
+			lnwire.ErrChanTooLarge)
-		)
 		return
 	}
 
@@ -871,7 +887,7 @@ func (f *fundingManager) handleFundingOpen(fmsg *fundingOpenMsg) {
 	if err != nil {
 		fndgLog.Errorf("Unable to initialize reservation: %v", err)
 		f.failFundingFlow(fmsg.peerAddress.IdentityKey,
-			msg.PendingChannelID, []byte(err.Error()))
+			msg.PendingChannelID, err)
 		return
 	}
 
@@ -890,10 +906,9 @@ func (f *fundingManager) handleFundingOpen(fmsg *fundingOpenMsg) {
 		msg.MaxValueInFlight, msg.HtlcMinimum, msg.ChannelReserve,
 	)
 	if err != nil {
-		f.failFundingFlow(
+		fndgLog.Errorf("Unaccaptable channel constraints: %v", err)
-			fmsg.peerAddress.IdentityKey, fmsg.msg.PendingChannelID,
+		f.failFundingFlow(fmsg.peerAddress.IdentityKey,
-			[]byte(fmt.Sprintf("Unacceptable channel "+
+			fmsg.msg.PendingChannelID, err,
-				"constraints: %v", err)),
 		)
 		return
 	}
@@ -951,9 +966,8 @@ func (f *fundingManager) handleFundingOpen(fmsg *fundingOpenMsg) {
 	err = reservation.ProcessSingleContribution(remoteContribution)
 	if err != nil {
 		fndgLog.Errorf("unable to add contribution reservation: %v", err)
-		// TODO(roasbeef): verify only sending sane info over
 		f.failFundingFlow(fmsg.peerAddress.IdentityKey,
-			msg.PendingChannelID, []byte(err.Error()))
+			msg.PendingChannelID, err)
 		return
 	}
 
@@ -985,7 +999,7 @@ func (f *fundingManager) handleFundingOpen(fmsg *fundingOpenMsg) {
 	if err != nil {
 		fndgLog.Errorf("unable to send funding response to peer: %v", err)
 		f.failFundingFlow(fmsg.peerAddress.IdentityKey,
-			msg.PendingChannelID, []byte(err.Error()))
+			msg.PendingChannelID, err)
 		return
 	}
 }
@@ -1028,11 +1042,9 @@ func (f *fundingManager) handleFundingAccept(fmsg *fundingAcceptMsg) {
 		msg.MaxValueInFlight, msg.HtlcMinimum, msg.ChannelReserve,
 	)
 	if err != nil {
-		f.failFundingFlow(
+		fndgLog.Warnf("Unacceptable channel constraints: %v", err)
-			fmsg.peerAddress.IdentityKey, fmsg.msg.PendingChannelID,
+		f.failFundingFlow(fmsg.peerAddress.IdentityKey,
-			[]byte(fmt.Sprintf("Unacceptable channel "+
+			fmsg.msg.PendingChannelID, err)
-				"constraints: %v", err)),
-		)
 		return
 	}
 
@@ -1070,7 +1082,7 @@ func (f *fundingManager) handleFundingAccept(fmsg *fundingAcceptMsg) {
 		fndgLog.Errorf("Unable to process contribution from %v: %v",
 			fmsg.peerAddress.IdentityKey, err)
 		f.failFundingFlow(fmsg.peerAddress.IdentityKey,
-			msg.PendingChannelID, []byte(err.Error()))
+			msg.PendingChannelID, err)
 		resCtx.err <- err
 		return
 	}
@@ -1115,7 +1127,7 @@ func (f *fundingManager) handleFundingAccept(fmsg *fundingAcceptMsg) {
 	if err != nil {
 		fndgLog.Errorf("Unable to parse signature: %v", err)
 		f.failFundingFlow(fmsg.peerAddress.IdentityKey,
-			msg.PendingChannelID, []byte(err.Error()))
+			msg.PendingChannelID, err)
 		resCtx.err <- err
 		return
 	}
@@ -1123,7 +1135,7 @@ func (f *fundingManager) handleFundingAccept(fmsg *fundingAcceptMsg) {
 	if err != nil {
 		fndgLog.Errorf("Unable to send funding complete message: %v", err)
 		f.failFundingFlow(fmsg.peerAddress.IdentityKey,
-			msg.PendingChannelID, []byte(err.Error()))
+			msg.PendingChannelID, err)
 		resCtx.err <- err
 		return
 	}
@@ -1177,7 +1189,7 @@ func (f *fundingManager) handleFundingCreated(fmsg *fundingCreatedMsg) {
 		// TODO(roasbeef): better error logging: peerID, channelID, etc.
 		fndgLog.Errorf("unable to complete single reservation: %v", err)
 		f.failFundingFlow(fmsg.peerAddress.IdentityKey,
-			pendingChanID, []byte(err.Error()))
+			pendingChanID, err)
 		return
 	}
 
@@ -1218,7 +1230,7 @@ func (f *fundingManager) handleFundingCreated(fmsg *fundingCreatedMsg) {
 	if err != nil {
 		fndgLog.Errorf("unable to parse signature: %v", err)
 		f.failFundingFlow(fmsg.peerAddress.IdentityKey,
-			pendingChanID, []byte(err.Error()))
+			pendingChanID, err)
 		deleteFromDatabase()
 		return
 	}
@@ -1230,7 +1242,7 @@ func (f *fundingManager) handleFundingCreated(fmsg *fundingCreatedMsg) {
 	if err := f.cfg.SendToPeer(peerKey, fundingSigned); err != nil {
 		fndgLog.Errorf("unable to send FundingSigned message: %v", err)
 		f.failFundingFlow(fmsg.peerAddress.IdentityKey,
-			pendingChanID, []byte(err.Error()))
+			pendingChanID, err)
 		deleteFromDatabase()
 		return
 	}
@@ -1332,11 +1344,12 @@ func (f *fundingManager) handleFundingSigned(fmsg *fundingSignedMsg) {
 	delete(f.signedReservations, fmsg.msg.ChanID)
 	f.resMtx.Unlock()
 	if !ok {
-		err := fmt.Sprintf("Unable to find signed reservation for "+
+		err := fmt.Errorf("Unable to find signed reservation for "+
 			"chan_id=%x", fmsg.msg.ChanID)
-		fndgLog.Warnf(err)
+		fndgLog.Warnf(err.Error())
+		// TODO: add ErrChanNotFound?
 		f.failFundingFlow(fmsg.peerAddress.IdentityKey,
-			pendingChanID, []byte(err))
+			pendingChanID, err)
 		return
 	}
 
@@ -1346,8 +1359,9 @@ func (f *fundingManager) handleFundingSigned(fmsg *fundingSignedMsg) {
 	if err != nil {
 		fndgLog.Warnf("Unable to find reservation (peerID:%v, chanID:%x)",
 			peerKey, pendingChanID[:])
+		// TODO: add ErrChanNotFound?
 		f.failFundingFlow(fmsg.peerAddress.IdentityKey,
-			pendingChanID, []byte(err.Error()))
+			pendingChanID, err)
 		return
 	}
 
@@ -1369,7 +1383,7 @@ func (f *fundingManager) handleFundingSigned(fmsg *fundingSignedMsg) {
 		fndgLog.Errorf("Unable to complete reservation sign complete: %v", err)
 		resCtx.err <- err
 		f.failFundingFlow(fmsg.peerAddress.IdentityKey,
-			pendingChanID, []byte(err.Error()))
+			pendingChanID, err)
 		return
 	}