Merge pull request #6716 from Crypt-iQ/zeroconfacceptor

multi: add zeroconfacceptor to default reject incoming channels

chanacceptor/chainedacceptor.go

@@ -23,6 +23,8 @@ func NewChainedAcceptor() *ChainedAcceptor {
 }
 
 // AddAcceptor adds a ChannelAcceptor to this ChainedAcceptor.
+//
+// NOTE: Part of the MultiplexAcceptor interface.
 func (c *ChainedAcceptor) AddAcceptor(acceptor ChannelAcceptor) uint64 {
 	id := atomic.AddUint64(&c.acceptorID, 1)
 
@@ -36,12 +38,22 @@ func (c *ChainedAcceptor) AddAcceptor(acceptor ChannelAcceptor) uint64 {
 
 // RemoveAcceptor removes a ChannelAcceptor from this ChainedAcceptor given
 // an ID.
+//
+// NOTE: Part of the MultiplexAcceptor interface.
 func (c *ChainedAcceptor) RemoveAcceptor(id uint64) {
 	c.acceptorsMtx.Lock()
 	delete(c.acceptors, id)
 	c.acceptorsMtx.Unlock()
 }
 
+// numAcceptors returns the number of acceptors contained in the
+// ChainedAcceptor.
+func (c *ChainedAcceptor) numAcceptors() int {
+	c.acceptorsMtx.RLock()
+	defer c.acceptorsMtx.RUnlock()
+	return len(c.acceptors)
+}
+
 // Accept evaluates the results of all ChannelAcceptors in the acceptors map
 // and returns the conjunction of all these predicates.
 //
@@ -91,5 +103,5 @@ func (c *ChainedAcceptor) Accept(req *ChannelAcceptRequest) *ChannelAcceptRespon
 }
 
 // A compile-time constraint to ensure ChainedAcceptor implements the
-// ChannelAcceptor interface.
-var _ ChannelAcceptor = (*ChainedAcceptor)(nil)
+// MultiplexAcceptor interface.
+var _ MultiplexAcceptor = (*ChainedAcceptor)(nil)

chanacceptor/interface.go

@@ -118,3 +118,16 @@ func (c *ChannelAcceptResponse) RejectChannel() bool {
 type ChannelAcceptor interface {
 	Accept(req *ChannelAcceptRequest) *ChannelAcceptResponse
 }
+
+// MultiplexAcceptor is an interface that abstracts the ability of a
+// ChannelAcceptor to contain sub-ChannelAcceptors.
+type MultiplexAcceptor interface {
+	// Embed the ChannelAcceptor.
+	ChannelAcceptor
+
+	// AddAcceptor nests a ChannelAcceptor inside the MultiplexAcceptor.
+	AddAcceptor(acceptor ChannelAcceptor) uint64
+
+	// Remove a sub-ChannelAcceptor.
+	RemoveAcceptor(id uint64)
+}

chanacceptor/rpcacceptor.go

@@ -258,20 +258,73 @@ func (r *RPCAcceptor) sendAcceptRequests(errChan chan error,
 			pendingChanID := req.OpenChanMsg.PendingChannelID
 
 			// Map the channel commitment type to its RPC
-			// counterpart.
-			var commitmentType lnrpc.CommitmentType
+			// counterpart. Also determine whether the zero-conf or
+			// scid-alias channel types are set.
+			var (
+				commitmentType lnrpc.CommitmentType
+				wantsZeroConf  bool
+				wantsScidAlias bool
+			)
+
 			if req.OpenChanMsg.ChannelType != nil {
 				channelFeatures := lnwire.RawFeatureVector(
 					*req.OpenChanMsg.ChannelType,
 				)
 				switch {
 				case channelFeatures.OnlyContains(
+					lnwire.ZeroConfRequired,
+					lnwire.ScidAliasRequired,
 					lnwire.ScriptEnforcedLeaseRequired,
 					lnwire.AnchorsZeroFeeHtlcTxRequired,
 					lnwire.StaticRemoteKeyRequired,
 				):
 					commitmentType = lnrpc.CommitmentType_SCRIPT_ENFORCED_LEASE
 
+				case channelFeatures.OnlyContains(
+					lnwire.ZeroConfRequired,
+					lnwire.ScriptEnforcedLeaseRequired,
+					lnwire.AnchorsZeroFeeHtlcTxRequired,
+					lnwire.StaticRemoteKeyRequired,
+				):
+					commitmentType = lnrpc.CommitmentType_SCRIPT_ENFORCED_LEASE
+
+				case channelFeatures.OnlyContains(
+					lnwire.ScidAliasRequired,
+					lnwire.ScriptEnforcedLeaseRequired,
+					lnwire.AnchorsZeroFeeHtlcTxRequired,
+					lnwire.StaticRemoteKeyRequired,
+				):
+					commitmentType = lnrpc.CommitmentType_SCRIPT_ENFORCED_LEASE
+
+				case channelFeatures.OnlyContains(
+					lnwire.ScriptEnforcedLeaseRequired,
+					lnwire.AnchorsZeroFeeHtlcTxRequired,
+					lnwire.StaticRemoteKeyRequired,
+				):
+					commitmentType = lnrpc.CommitmentType_SCRIPT_ENFORCED_LEASE
+
+				case channelFeatures.OnlyContains(
+					lnwire.ZeroConfRequired,
+					lnwire.ScidAliasRequired,
+					lnwire.AnchorsZeroFeeHtlcTxRequired,
+					lnwire.StaticRemoteKeyRequired,
+				):
+					commitmentType = lnrpc.CommitmentType_ANCHORS
+
+				case channelFeatures.OnlyContains(
+					lnwire.ZeroConfRequired,
+					lnwire.AnchorsZeroFeeHtlcTxRequired,
+					lnwire.StaticRemoteKeyRequired,
+				):
+					commitmentType = lnrpc.CommitmentType_ANCHORS
+
+				case channelFeatures.OnlyContains(
+					lnwire.ScidAliasRequired,
+					lnwire.AnchorsZeroFeeHtlcTxRequired,
+					lnwire.StaticRemoteKeyRequired,
+				):
+					commitmentType = lnrpc.CommitmentType_ANCHORS
+
 				case channelFeatures.OnlyContains(
 					lnwire.AnchorsZeroFeeHtlcTxRequired,
 					lnwire.StaticRemoteKeyRequired,
@@ -291,6 +344,20 @@ func (r *RPCAcceptor) sendAcceptRequests(errChan chan error,
 						"in channel acceptor request: %v",
 						req.OpenChanMsg.ChannelType)
 				}
+
+				if channelFeatures.IsSet(
+					lnwire.ZeroConfRequired,
+				) {
+
+					wantsZeroConf = true
+				}
+
+				if channelFeatures.IsSet(
+					lnwire.ScidAliasRequired,
+				) {
+
+					wantsScidAlias = true
+				}
 			}
 
 			acceptRequests[pendingChanID] = newRequest
@@ -311,6 +378,8 @@ func (r *RPCAcceptor) sendAcceptRequests(errChan chan error,
 				MaxAcceptedHtlcs: uint32(req.OpenChanMsg.MaxAcceptedHTLCs),
 				ChannelFlags:     uint32(req.OpenChanMsg.ChannelFlags),
 				CommitmentType:   commitmentType,
+				WantsZeroConf:    wantsZeroConf,
+				WantsScidAlias:   wantsScidAlias,
 			}
 
 			if err := r.send(chanAcceptReq); err != nil {

chanacceptor/zeroconfacceptor.go

@@ -0,0 +1,68 @@
+package chanacceptor
+
+import "github.com/lightningnetwork/lnd/lnwire"
+
+// ZeroConfAcceptor wraps a regular ChainedAcceptor. If no acceptors are in the
+// ChainedAcceptor, then Accept will reject all channel open requests. This
+// should only be enabled when the zero-conf feature bit is set and is used to
+// protect users from a malicious counter-party double-spending the zero-conf
+// funding tx.
+type ZeroConfAcceptor struct {
+	chainedAcceptor *ChainedAcceptor
+}
+
+// NewZeroConfAcceptor initializes a ZeroConfAcceptor.
+func NewZeroConfAcceptor() *ZeroConfAcceptor {
+	return &ZeroConfAcceptor{
+		chainedAcceptor: NewChainedAcceptor(),
+	}
+}
+
+// AddAcceptor adds a sub-ChannelAcceptor to the internal ChainedAcceptor.
+func (z *ZeroConfAcceptor) AddAcceptor(acceptor ChannelAcceptor) uint64 {
+	return z.chainedAcceptor.AddAcceptor(acceptor)
+}
+
+// RemoveAcceptor removes a sub-ChannelAcceptor from the internal
+// ChainedAcceptor.
+func (z *ZeroConfAcceptor) RemoveAcceptor(id uint64) {
+	z.chainedAcceptor.RemoveAcceptor(id)
+}
+
+// Accept will deny the channel open request if the internal ChainedAcceptor is
+// empty. If the internal ChainedAcceptor has any acceptors, then Accept will
+// instead be called on it.
+//
+// NOTE: Part of the ChannelAcceptor interface.
+func (z *ZeroConfAcceptor) Accept(
+	req *ChannelAcceptRequest) *ChannelAcceptResponse {
+
+	// Alias for less verbosity.
+	channelType := req.OpenChanMsg.ChannelType
+
+	// Check if the channel type sets the zero-conf bit.
+	var zeroConfSet bool
+
+	if channelType != nil {
+		channelFeatures := lnwire.RawFeatureVector(*channelType)
+		zeroConfSet = channelFeatures.IsSet(lnwire.ZeroConfRequired)
+	}
+
+	// If there are no acceptors and the counter-party is requesting a zero
+	// conf channel, reject the attempt.
+	if z.chainedAcceptor.numAcceptors() == 0 && zeroConfSet {
+		// Deny the channel open request.
+		rejectChannel := NewChannelAcceptResponse(
+			false, nil, nil, 0, 0, 0, 0, 0, 0, false,
+		)
+		return rejectChannel
+	}
+
+	// Otherwise, the ChainedAcceptor has sub-acceptors, so call Accept on
+	// it.
+	return z.chainedAcceptor.Accept(req)
+}
+
+// A compile-time constraint to ensure ZeroConfAcceptor implements the
+// MultiplexAcceptor interface.
+var _ MultiplexAcceptor = (*ZeroConfAcceptor)(nil)

chanacceptor/zeroconfacceptor_test.go

@@ -0,0 +1,83 @@
+package chanacceptor
+
+import (
+	"testing"
+
+	"github.com/lightningnetwork/lnd/lnwire"
+	"github.com/stretchr/testify/require"
+)
+
+// dummyAcceptor is a ChannelAcceptor that will never return a failure.
+type dummyAcceptor struct{}
+
+func (d *dummyAcceptor) Accept(
+	req *ChannelAcceptRequest) *ChannelAcceptResponse {
+
+	return &ChannelAcceptResponse{}
+}
+
+// TestZeroConfAcceptorNormal verifies that the ZeroConfAcceptor will let
+// requests go through for non-zero-conf channels if there are no
+// sub-acceptors.
+func TestZeroConfAcceptorNormal(t *testing.T) {
+	t.Parallel()
+
+	// Create the zero-conf acceptor.
+	zeroAcceptor := NewZeroConfAcceptor()
+
+	// Assert that calling Accept won't return a failure.
+	req := &ChannelAcceptRequest{
+		OpenChanMsg: &lnwire.OpenChannel{},
+	}
+	resp := zeroAcceptor.Accept(req)
+	require.False(t, resp.RejectChannel())
+
+	// Add a dummyAcceptor to the zero-conf acceptor. Assert that Accept
+	// does not return a failure.
+	dummy := &dummyAcceptor{}
+	dummyID := zeroAcceptor.AddAcceptor(dummy)
+	resp = zeroAcceptor.Accept(req)
+	require.False(t, resp.RejectChannel())
+
+	// Remove the dummyAcceptor from the zero-conf acceptor and assert that
+	// Accept doesn't return a failure.
+	zeroAcceptor.RemoveAcceptor(dummyID)
+	resp = zeroAcceptor.Accept(req)
+	require.False(t, resp.RejectChannel())
+}
+
+// TestZeroConfAcceptorZC verifies that the ZeroConfAcceptor will fail
+// zero-conf channel opens unless a sub-acceptor exists.
+func TestZeroConfAcceptorZC(t *testing.T) {
+	t.Parallel()
+
+	// Create the zero-conf acceptor.
+	zeroAcceptor := NewZeroConfAcceptor()
+
+	channelType := new(lnwire.ChannelType)
+	*channelType = lnwire.ChannelType(*lnwire.NewRawFeatureVector(
+		lnwire.ZeroConfRequired,
+	))
+
+	// Assert that calling Accept results in failure.
+	req := &ChannelAcceptRequest{
+		OpenChanMsg: &lnwire.OpenChannel{
+			ChannelType: channelType,
+		},
+	}
+	resp := zeroAcceptor.Accept(req)
+	require.True(t, resp.RejectChannel())
+
+	// Add a dummyAcceptor to the zero-conf acceptor. Assert that Accept
+	// does not return a failure.
+	dummy := &dummyAcceptor{}
+	dummyID := zeroAcceptor.AddAcceptor(dummy)
+	resp = zeroAcceptor.Accept(req)
+	require.False(t, resp.RejectChannel())
+
+	// Remove the dummyAcceptor from the zero-conf acceptor and assert that
+	// Accept returns a failure.
+	zeroAcceptor.RemoveAcceptor(dummyID)
+	resp = zeroAcceptor.Accept(req)
+	require.True(t, resp.RejectChannel())
+}

docs/release-notes/release-notes-0.15.1.md

@@ -13,6 +13,9 @@
   information. A new `listaliases` API has also been added that returns a data dump of all
   existing alias info.](https://github.com/lightningnetwork/lnd/pull/6734)
 
+* [Adds a `ZeroConfAcceptor` that rejects any zero-conf channel opens unless an RPC `ChannelAcceptor` is
+  active. This is a safety measure to avoid funds loss.](https://github.com/lightningnetwork/lnd/pull/6716)
+
 ## Build system
 
 * [Add the release build directory to the `.gitignore` file to avoid the release

funding/manager.go

@@ -1369,6 +1369,18 @@ func (f *Manager) handleFundingOpen(peer lnpeer.Peer,
 		zeroConf = featureVec.IsSet(lnwire.ZeroConfRequired)
 		scid = featureVec.IsSet(lnwire.ScidAliasRequired)
 
+		// If the zero-conf channel type was negotiated, ensure that
+		// the acceptor allows it.
+		if zeroConf && !acceptorResp.ZeroConf {
+			// Fail the funding flow.
+			flowErr := fmt.Errorf("channel acceptor blocked " +
+				"zero-conf channel negotiation")
+			f.failFundingFlow(
+				peer, msg.PendingChannelID, flowErr,
+			)
+			return
+		}
+
 		// If the zero-conf channel type wasn't negotiated and the
 		// fundee still wants a zero-conf channel, perform more checks.
 		// Require that both sides have the scid-alias feature bit set.

funding/manager_test.go

@@ -25,7 +25,7 @@ import (
 	"github.com/btcsuite/btcd/wire"
 	"github.com/lightningnetwork/lnd/chainntnfs"
 	"github.com/lightningnetwork/lnd/chainreg"
-	"github.com/lightningnetwork/lnd/chanacceptor"
+	acpt "github.com/lightningnetwork/lnd/chanacceptor"
 	"github.com/lightningnetwork/lnd/channeldb"
 	"github.com/lightningnetwork/lnd/channelnotifier"
 	"github.com/lightningnetwork/lnd/discovery"
@@ -222,6 +222,19 @@ func (m *mockChanEvent) NotifyPendingOpenChannelEvent(outpoint wire.OutPoint,
 	}
 }
 
+// mockZeroConfAcceptor always accepts the channel open request for zero-conf
+// channels. It will set the ZeroConf bool in the ChannelAcceptResponse. This
+// is needed to properly unit test the zero-conf logic in the funding manager.
+type mockZeroConfAcceptor struct{}
+
+func (m *mockZeroConfAcceptor) Accept(
+	req *acpt.ChannelAcceptRequest) *acpt.ChannelAcceptResponse {
+
+	return &acpt.ChannelAcceptResponse{
+		ZeroConf: true,
+	}
+}
+
 type newChannelMsg struct {
 	channel *channeldb.OpenChannel
 	err     chan error
@@ -400,7 +413,7 @@ func createTestFundingManager(t *testing.T, privKey *btcec.PrivateKey,
 
 	var chanIDSeed [32]byte
 
-	chainedAcceptor := chanacceptor.NewChainedAcceptor()
+	chainedAcceptor := acpt.NewChainedAcceptor()
 
 	fundingCfg := Config{
 		IDKey:        privKey.PubKey(),
@@ -556,7 +569,7 @@ func recreateAliceFundingManager(t *testing.T, alice *testNode) {
 
 	oldCfg := alice.fundingMgr.cfg
 
-	chainedAcceptor := chanacceptor.NewChainedAcceptor()
+	chainedAcceptor := acpt.NewChainedAcceptor()
 
 	f, err := NewFundingManager(Config{
 		IDKey:        oldCfg.IDKey,
@@ -3760,6 +3773,11 @@ func TestFundingManagerZeroConf(t *testing.T) {
 		*lnwire.NewRawFeatureVector(channelTypeBits...),
 	)
 
+	// Create a default-accept channelacceptor so that the test passes and
+	// we don't have to use any goroutines.
+	mockAcceptor := &mockZeroConfAcceptor{}
+	bob.fundingMgr.cfg.OpenChannelPredicate = mockAcceptor
+
 	// Call fundChannel with the zero-conf ChannelType.
 	fundingTx := fundChannel(
 		t, alice, bob, fundingAmt, pushAmt, false, 1, updateChan, true,

lnd.go

@@ -496,15 +496,22 @@ func Main(cfg *Config, lisCfg ListenerCfg, implCfg *ImplementationCfg,
 		}
 	}
 
-	// Initialize the ChainedAcceptor.
-	chainedAcceptor := chanacceptor.NewChainedAcceptor()
+	// Initialize the MultiplexAcceptor. If lnd was started with the
+	// zero-conf feature bit, then this will be a ZeroConfAcceptor.
+	// Otherwise, this will be a ChainedAcceptor.
+	var multiAcceptor chanacceptor.MultiplexAcceptor
+	if cfg.ProtocolOptions.ZeroConf() {
+		multiAcceptor = chanacceptor.NewZeroConfAcceptor()
+	} else {
+		multiAcceptor = chanacceptor.NewChainedAcceptor()
+	}
 
 	// Set up the core server which will listen for incoming peer
 	// connections.
 	server, err := newServer(
 		cfg, cfg.Listeners, dbs, activeChainControl, &idKeyDesc,
 		activeChainControl.Cfg.WalletUnlockParams.ChansToRestore,
-		chainedAcceptor, torController,
+		multiAcceptor, torController,
 	)
 	if err != nil {
 		return mkErr("unable to create server: %v", err)
@@ -534,7 +541,7 @@ func Main(cfg *Config, lisCfg ListenerCfg, implCfg *ImplementationCfg,
 	// start the RPC server.
 	err = rpcServer.addDeps(
 		server, interceptorChain.MacaroonService(), cfg.SubRPCServers,
-		atplManager, server.invoices, tower, chainedAcceptor,
+		atplManager, server.invoices, tower, multiAcceptor,
 	)
 	if err != nil {
 		return mkErr("unable to add deps to RPC server: %v", err)

lnrpc/lightning.proto

@@ -926,6 +926,14 @@ message ChannelAcceptRequest {
 
     // The commitment type the initiator wishes to use for the proposed channel.
     CommitmentType commitment_type = 14;
+
+    // Whether the initiator wants to open a zero-conf channel via the channel
+    // type.
+    bool wants_zero_conf = 15;
+
+    // Whether the initiator wants to use the scid-alias channel type. This is
+    // separate from the feature bit.
+    bool wants_scid_alias = 16;
 }
 
 message ChannelAcceptResponse {

lnrpc/lightning.swagger.json

@@ -3423,6 +3423,14 @@
         "commitment_type": {
           "$ref": "#/definitions/lnrpcCommitmentType",
           "description": "The commitment type the initiator wishes to use for the proposed channel."
+        },
+        "wants_zero_conf": {
+          "type": "boolean",
+          "description": "Whether the initiator wants to open a zero-conf channel via the channel\ntype."
+        },
+        "wants_scid_alias": {
+          "type": "boolean",
+          "description": "Whether the initiator wants to use the scid-alias channel type. This is\nseparate from the feature bit."
         }
       }
     },

lntest/itest/lnd_channel_backup_test.go

@@ -1063,6 +1063,18 @@ func testChanRestoreScenario(t *harnessTest, net *lntest.NetworkHarness,
 		)
 
 	default:
+		// If we are testing zero-conf channels, setup a
+		// ChannelAcceptor for the fundee.
+		var cancel context.CancelFunc
+		if testCase.zeroConf {
+			// Setup a ChannelAcceptor.
+			var ctxc context.Context
+			ctxc, cancel = context.WithCancel(ctxb)
+			acceptStream, err := to.ChannelAcceptor(ctxc)
+			require.NoError(t.t, err)
+			go acceptChannel(t, true, acceptStream)
+		}
+
 		var fundingShim *lnrpc.FundingShim
 		if testCase.commitmentType == lnrpc.CommitmentType_SCRIPT_ENFORCED_LEASE {
 			_, minerHeight, err := net.Miner.Client.GetBestBlock()
@@ -1085,6 +1097,11 @@ func testChanRestoreScenario(t *harnessTest, net *lntest.NetworkHarness,
 			t, net, from, to, params,
 		)
 
+		// Remove the ChannelAcceptor.
+		if testCase.zeroConf {
+			cancel()
+		}
+
 		// Wait for both sides to see the opened channel.
 		err = dave.WaitForNetworkChannelOpen(chanPoint)
 		if err != nil {

lntest/itest/lnd_multi-hop_test.go

@@ -265,6 +265,23 @@ func createThreeHopNetwork(t *harnessTest, net *lntest.NetworkHarness,
 			net, t, alice, bob, chanAmt, thawHeight, true,
 		)
 	}
+
+	// If a zero-conf channel is being opened, the nodes are signalling the
+	// zero-conf feature bit. Setup a ChannelAcceptor for the fundee.
+	ctxb := context.Background()
+
+	var (
+		cancel context.CancelFunc
+		ctxc   context.Context
+	)
+
+	if zeroConf {
+		ctxc, cancel = context.WithCancel(ctxb)
+		acceptStream, err := bob.ChannelAcceptor(ctxc)
+		require.NoError(t.t, err)
+		go acceptChannel(t, true, acceptStream)
+	}
+
 	aliceChanPoint := openChannelAndAssert(
 		t, net, alice, bob,
 		lntest.OpenChannelParams{
@@ -275,6 +292,11 @@ func createThreeHopNetwork(t *harnessTest, net *lntest.NetworkHarness,
 		},
 	)
 
+	// Remove the ChannelAcceptor for Bob.
+	if zeroConf {
+		cancel()
+	}
+
 	err := alice.WaitForNetworkChannelOpen(aliceChanPoint)
 	if err != nil {
 		t.Fatalf("alice didn't report channel: %v", err)
@@ -320,6 +342,16 @@ func createThreeHopNetwork(t *harnessTest, net *lntest.NetworkHarness,
 			net, t, bob, carol, chanAmt, thawHeight, true,
 		)
 	}
+
+	// Setup a ChannelAcceptor for Carol if a zero-conf channel open is
+	// being attempted.
+	if zeroConf {
+		ctxc, cancel = context.WithCancel(ctxb)
+		acceptStream, err := carol.ChannelAcceptor(ctxc)
+		require.NoError(t.t, err)
+		go acceptChannel(t, true, acceptStream)
+	}
+
 	bobChanPoint := openChannelAndAssert(
 		t, net, bob, carol,
 		lntest.OpenChannelParams{
@@ -329,6 +361,12 @@ func createThreeHopNetwork(t *harnessTest, net *lntest.NetworkHarness,
 			ZeroConf:       zeroConf,
 		},
 	)
+
+	// Remove the ChannelAcceptor for Carol.
+	if zeroConf {
+		cancel()
+	}
+
 	err = bob.WaitForNetworkChannelOpen(bobChanPoint)
 	if err != nil {
 		t.Fatalf("alice didn't report channel: %v", err)

lntest/itest/lnd_zero_conf_test.go

@@ -19,6 +19,8 @@ import (
 // testZeroConfChannelOpen tests that opening a zero-conf channel works and
 // sending payments also works.
 func testZeroConfChannelOpen(net *lntest.NetworkHarness, t *harnessTest) {
+	ctxb := context.Background()
+
 	// Since option-scid-alias is opt-in, the provided harness nodes will
 	// not have the feature bit set. Also need to set anchors as those are
 	// default-off in itests.
@@ -44,7 +46,6 @@ func testZeroConfChannelOpen(net *lntest.NetworkHarness, t *harnessTest) {
 	)
 
 	// Wait for both Bob and Carol to view the channel as active.
-	ctxb := context.Background()
 	err := net.Bob.WaitForNetworkChannelOpen(fundingPoint)
 	require.NoError(t.t, err, "bob didn't report channel")
 	err = carol.WaitForNetworkChannelOpen(fundingPoint)
@@ -60,6 +61,12 @@ func testZeroConfChannelOpen(net *lntest.NetworkHarness, t *harnessTest) {
 	// Ensure that both Carol and Dave are connected.
 	net.EnsureConnected(t.t, carol, dave)
 
+	// Setup a ChannelAcceptor for Dave.
+	ctxc, cancel := context.WithCancel(ctxb)
+	acceptStream, err := dave.ChannelAcceptor(ctxc)
+	require.NoError(t.t, err)
+	go acceptChannel(t, true, acceptStream)
+
 	// Open a private zero-conf anchors channel of 1M satoshis.
 	params := lntest.OpenChannelParams{
 		Amt:            chanAmt,
@@ -69,6 +76,9 @@ func testZeroConfChannelOpen(net *lntest.NetworkHarness, t *harnessTest) {
 	}
 	chanOpenUpdate := openChannelStream(t, net, carol, dave, params)
 
+	// Remove the ChannelAcceptor.
+	cancel()
+
 	// We should receive the OpenStatusUpdate_ChanOpen update without
 	// having to mine any blocks.
 	fundingPoint2, err := net.WaitForChannelOpen(chanOpenUpdate)
@@ -153,10 +163,19 @@ func testZeroConfChannelOpen(net *lntest.NetworkHarness, t *harnessTest) {
 	// Give Eve some coins to fund the channel.
 	net.SendCoins(t.t, btcutil.SatoshiPerBitcoin, eve)
 
+	// Setup a ChannelAcceptor.
+	ctxc, cancel = context.WithCancel(ctxb)
+	acceptStream, err = carol.ChannelAcceptor(ctxc)
+	require.NoError(t.t, err)
+	go acceptChannel(t, true, acceptStream)
+
 	// We'll open a public zero-conf anchors channel of 1M satoshis.
 	params.Private = false
 	chanOpenUpdate2 := openChannelStream(t, net, eve, carol, params)
 
+	// Remove the ChannelAcceptor.
+	cancel()
+
 	// Wait to receive the OpenStatusUpdate_ChanOpen update.
 	fundingPoint3, err := net.WaitForChannelOpen(chanOpenUpdate2)
 	require.NoError(t.t, err, "error while waiting for channel open")
@@ -581,6 +600,12 @@ func testPrivateUpdateAlias(net *lntest.NetworkHarness, t *harnessTest,
 	err = dave.WaitForNetworkChannelOpen(fundingPoint)
 	require.NoError(t.t, err, "dave didn't report channel")
 
+	// Setup a ChannelAcceptor for Dave.
+	ctxc, cancel := context.WithCancel(ctxb)
+	acceptStream, err := dave.ChannelAcceptor(ctxc)
+	require.NoError(t.t, err)
+	go acceptChannel(t, zeroConf, acceptStream)
+
 	// Open a private channel, optionally specifying a channel-type.
 	params := lntest.OpenChannelParams{
 		Amt:            chanAmt,
@@ -592,6 +617,9 @@ func testPrivateUpdateAlias(net *lntest.NetworkHarness, t *harnessTest,
 	}
 	chanOpenUpdate := openChannelStream(t, net, carol, dave, params)
 
+	// Remove the ChannelAcceptor.
+	cancel()
+
 	if !zeroConf {
 		// If this is not a zero-conf channel, mine a single block to
 		// confirm the channel.

lntest/itest/utils.go

@@ -493,3 +493,21 @@ func getOutputIndex(t *harnessTest, miner *lntest.HarnessMiner,
 
 	return p2trOutputIndex
 }
+
+// acceptChannel is used to accept a single channel that comes across. This
+// should be run in a goroutine and is used to test nodes with the zero-conf
+// feature bit.
+func acceptChannel(t *harnessTest, zeroConf bool,
+	stream lnrpc.Lightning_ChannelAcceptorClient) {
+
+	req, err := stream.Recv()
+	require.NoError(t.t, err)
+
+	resp := &lnrpc.ChannelAcceptResponse{
+		Accept:        true,
+		PendingChanId: req.PendingChanId,
+		ZeroConf:      zeroConf,
+	}
+	err = stream.Send(resp)
+	require.NoError(t.t, err)
+}

rpcserver.go

@@ -612,7 +612,7 @@ type rpcServer struct {
 
 	// chanPredicate is used in the bidirectional ChannelAcceptor streaming
 	// method.
-	chanPredicate *chanacceptor.ChainedAcceptor
+	chanPredicate chanacceptor.MultiplexAcceptor
 
 	quit chan struct{}
 
@@ -676,7 +676,7 @@ func newRPCServer(cfg *Config, interceptorChain *rpcperms.InterceptorChain,
 func (r *rpcServer) addDeps(s *server, macService *macaroons.Service,
 	subServerCgs *subRPCServerConfigs, atpl *autopilot.Manager,
 	invoiceRegistry *invoices.InvoiceRegistry, tower *watchtower.Standalone,
-	chanPredicate *chanacceptor.ChainedAcceptor) error {
+	chanPredicate chanacceptor.MultiplexAcceptor) error {
 
 	// Set up router rpc backend.
 	selfNode, err := s.graphDB.SourceNode()