lndclient: expose SignMessage RPC

lndclient/signer_client.go

@@ -6,6 +6,7 @@ import (
 	"github.com/btcsuite/btcd/wire"
 	"github.com/lightninglabs/loop/swap"
 	"github.com/lightningnetwork/lnd/input"
+	"github.com/lightningnetwork/lnd/keychain"
 	"github.com/lightningnetwork/lnd/lnrpc/signrpc"
 	"google.golang.org/grpc"
 )
@@ -14,6 +15,11 @@ import (
 type SignerClient interface {
 	SignOutputRaw(ctx context.Context, tx *wire.MsgTx,
 		signDescriptors []*input.SignDescriptor) ([][]byte, error)
+
+	// SignMessage signs a message with the key specified in the key
+	// locator. The returned signature is fixed-size LN wire format encoded.
+	SignMessage(ctx context.Context, msg []byte,
+		locator keychain.KeyLocator) ([]byte, error)
 }
 
 type signerClient struct {
@@ -93,3 +99,28 @@ func (s *signerClient) SignOutputRaw(ctx context.Context, tx *wire.MsgTx,
 
 	return resp.RawSigs, nil
 }
+
+// SignMessage signs a message with the key specified in the key locator. The
+// returned signature is fixed-size LN wire format encoded.
+func (s *signerClient) SignMessage(ctx context.Context, msg []byte,
+	locator keychain.KeyLocator) ([]byte, error) {
+
+	rpcCtx, cancel := context.WithTimeout(ctx, rpcTimeout)
+	defer cancel()
+
+	rpcIn := &signrpc.SignMessageReq{
+		Msg: msg,
+		KeyLoc: &signrpc.KeyLocator{
+			KeyFamily: int32(locator.Family),
+			KeyIndex:  int32(locator.Index),
+		},
+	}
+
+	rpcCtx = s.signerMac.WithMacaroonAuth(rpcCtx)
+	resp, err := s.client.SignMessage(rpcCtx, rpcIn)
+	if err != nil {
+		return nil, err
+	}
+
+	return resp.Signature, nil
+}

test/lnd_services_mock.go

@@ -18,6 +18,7 @@ var (
 	testStartingHeight = int32(600)
 	testNodePubkey     = "03f5374b16f0b1f1b49101de1b9d89e0b460bc57ce9c2f9" +
 		"132b73dfc76d3704daa"
+	testSignature = []byte{55, 66, 77, 88, 99}
 )
 
 // NewMockLnd returns a new instance of LndMockServices that can be used in unit
@@ -59,6 +60,7 @@ func NewMockLnd() *LndMockServices {
 		epochChannel:       make(chan int32),
 		Height:             testStartingHeight,
 		NodePubkey:         testNodePubkey,
+		Signature:          testSignature,
 	}
 
 	lightningClient.lnd = &lnd
@@ -66,6 +68,7 @@ func NewMockLnd() *LndMockServices {
 	walletKit.lnd = &lnd
 	invoices.lnd = &lnd
 	router.lnd = &lnd
+	signer.lnd = &lnd
 
 	lnd.WaitForFinished = func() {
 		chainNotifier.WaitForFinished()
@@ -127,6 +130,7 @@ type LndMockServices struct {
 
 	Height     int32
 	NodePubkey string
+	Signature  []byte
 
 	WaitForFinished func()
 

test/signer_mock.go

@@ -5,9 +5,11 @@ import (
 
 	"github.com/btcsuite/btcd/wire"
 	"github.com/lightningnetwork/lnd/input"
+	"github.com/lightningnetwork/lnd/keychain"
 )
 
 type mockSigner struct {
+	lnd *LndMockServices
 }
 
 func (s *mockSigner) SignOutputRaw(ctx context.Context, tx *wire.MsgTx,
@@ -17,3 +19,9 @@ func (s *mockSigner) SignOutputRaw(ctx context.Context, tx *wire.MsgTx,
 
 	return rawSigs, nil
 }
+
+func (s *mockSigner) SignMessage(ctx context.Context, msg []byte,
+	locator keychain.KeyLocator) ([]byte, error) {
+
+	return s.lnd.Signature, nil
+}