[2/3] loopd: add macaroon authentication to the loop RPC server

README.md

@@ -333,18 +333,25 @@ pending swaps after a restart.
 Information about pending swaps is stored persistently in the swap database.
 Its location is `~/.loopd/<network>/loop.db`.
 
-## Transport security
+## Authentication and transport security
 
-The gRPC and REST connections of `loopd` are encrypted with TLS the same way
-`lnd` is.
+The gRPC and REST connections of `loopd` are encrypted with TLS and secured with
+macaroon authentication the same way `lnd` is.
 
 If no custom loop directory is set then the TLS certificate is stored in
-`~/.loopd/<network>/tls.cert`.
+`~/.loop/<network>/tls.cert` and the base macaroon in
+`~/.loop/<network>/loop.macaroon`.
 
-The `loop` command will pick up the file automatically on mainnet if no custom
+The `loop` command will pick up these file automatically on mainnet if no custom
 loop directory is used. For other networks it should be sufficient to add the
 `--network` flag to tell the CLI in what sub directory to look for the files.
 
+For more information on macaroons,
+[see the macaroon documentation of lnd.](https://github.com/lightningnetwork/lnd/blob/master/docs/macaroons.md)
+
+**NOTE**: Loop's macaroons are independent from `lnd`'s. The same macaroon
+cannot be used for both `loopd` and `lnd`.
+
 ## Multiple Simultaneous Swaps
 
 It is possible to execute multiple swaps simultaneously. Just keep loopd 

cmd/loop/main.go

@@ -66,9 +66,9 @@ var (
 		Value: loopd.DefaultTLSCertPath,
 	}
 	macaroonPathFlag = cli.StringFlag{
-		Name: "macaroonpath",
-		Usage: "path to macaroon file, only needed if loop runs " +
-			"in the same process as lnd",
+		Name:  "macaroonpath",
+		Usage: "path to macaroon file",
+		Value: loopd.DefaultMacaroonPath,
 	}
 )
 
@@ -171,25 +171,31 @@ func extractPathArgs(ctx *cli.Context) (string, string, error) {
 	}
 
 	// We'll now fetch the loopdir so we can make a decision on how to
-	// properly read the cert. This will either be the default, or will have
-	// been overwritten by the end user.
+	// properly read the macaroons and also the cert. This will either be
+	// the default, or will have been overwritten by the end user.
 	loopDir := lncfg.CleanAndExpandPath(ctx.GlobalString(loopDirFlag.Name))
 	tlsCertPath := lncfg.CleanAndExpandPath(ctx.GlobalString(
 		tlsCertFlag.Name,
 	))
+	macPath := lncfg.CleanAndExpandPath(ctx.GlobalString(
+		macaroonPathFlag.Name,
+	))
 
-	// If a custom lnd directory was set, we'll also check if custom paths
-	// for the TLS cert file were set as well. If not, we'll override their
-	// paths so they can be found within the custom loop directory set. This
-	// allows us to set a custom lnd directory, along with custom paths to
-	// the TLS cert file.
+	// If a custom loop directory was set, we'll also check if custom paths
+	// for the TLS cert and macaroon file were set as well. If not, we'll
+	// override their paths so they can be found within the custom loop
+	// directory set. This allows us to set a custom loop directory, along
+	// with custom paths to the TLS cert and macaroon file.
 	if loopDir != loopd.LoopDirBase || networkStr != loopd.DefaultNetwork {
 		tlsCertPath = filepath.Join(
 			loopDir, networkStr, loopd.DefaultTLSCertFilename,
 		)
+		macPath = filepath.Join(
+			loopDir, networkStr, loopd.DefaultMacaroonFilename,
+		)
 	}
 
-	return tlsCertPath, ctx.GlobalString(macaroonPathFlag.Name), nil
+	return tlsCertPath, macPath, nil
 }
 
 type inLimits struct {
@@ -373,8 +379,15 @@ func logSwap(swap *looprpc.SwapStatus) {
 func getClientConn(address, tlsCertPath, macaroonPath string) (*grpc.ClientConn,
 	error) {
 
+	// We always need to send a macaroon.
+	macOption, err := readMacaroon(macaroonPath)
+	if err != nil {
+		return nil, err
+	}
+
 	opts := []grpc.DialOption{
 		grpc.WithDefaultCallOptions(maxMsgRecvSize),
+		macOption,
 	}
 
 	// TLS cannot be disabled, we'll always have a cert file to read.
@@ -383,15 +396,6 @@ func getClientConn(address, tlsCertPath, macaroonPath string) (*grpc.ClientConn,
 		return nil, err
 	}
 
-	// Macaroons are not yet enabled by default.
-	if macaroonPath != "" {
-		macOption, err := readMacaroon(macaroonPath)
-		if err != nil {
-			return nil, err
-		}
-		opts = append(opts, macOption)
-	}
-
 	opts = append(opts, grpc.WithTransportCredentials(creds))
 
 	conn, err := grpc.Dial(address, opts...)

go.mod

@@ -12,14 +12,18 @@ require (
 	github.com/jessevdk/go-flags v1.4.0
 	github.com/lightninglabs/lndclient v0.11.0-0
 	github.com/lightninglabs/protobuf-hex-display v1.3.3-0.20191212020323-b444784ce75d
-	github.com/lightningnetwork/lnd v0.11.0-beta
+
+	// TODO(guggero): Bump lnd to the final v0.11.1-beta version once it's
+	// released.
+	github.com/lightningnetwork/lnd v0.11.0-beta.rc4.0.20200911014924-bc6e52888763
 	github.com/lightningnetwork/lnd/cert v1.0.3
 	github.com/lightningnetwork/lnd/queue v1.0.4
 	github.com/stretchr/testify v1.5.1
 	github.com/urfave/cli v1.20.0
 	golang.org/x/net v0.0.0-20191002035440-2ec189313ef0
 	google.golang.org/genproto v0.0.0-20190927181202-20e1ac93f88c
 	google.golang.org/grpc v1.24.0
+	gopkg.in/macaroon-bakery.v2 v2.0.1
 	gopkg.in/macaroon.v2 v2.1.0
 )
 

go.sum

@@ -45,6 +45,8 @@ github.com/btcsuite/btcwallet/walletdb v1.3.3 h1:u6e7vRIKBF++cJy+hOHaMGg+88ZTwvp
 github.com/btcsuite/btcwallet/walletdb v1.3.3/go.mod h1:oJDxAEUHVtnmIIBaa22wSBPTVcs6hUp5NKWmI8xDwwU=
 github.com/btcsuite/btcwallet/wtxmgr v1.0.0/go.mod h1:vc4gBprll6BP0UJ+AIGDaySoc7MdAmZf8kelfNb8CFY=
 github.com/btcsuite/btcwallet/wtxmgr v1.2.0 h1:ZUYPsSv8GjF9KK7lboB2OVHF0uYEcHxgrCfFWqPd9NA=
+github.com/btcsuite/btcwallet/wtxmgr v1.2.0 h1:ZUYPsSv8GjF9KK7lboB2OVHF0uYEcHxgrCfFWqPd9NA=
+github.com/btcsuite/btcwallet/wtxmgr v1.2.0/go.mod h1:h8hkcKUE3X7lMPzTUoGnNiw5g7VhGrKEW3KpR2r0VnY=
 github.com/btcsuite/btcwallet/wtxmgr v1.2.0/go.mod h1:h8hkcKUE3X7lMPzTUoGnNiw5g7VhGrKEW3KpR2r0VnY=
 github.com/btcsuite/go-socks v0.0.0-20170105172521-4720035b7bfd h1:R/opQEbFEy9JGkIguV40SvRY1uliPX8ifOvi6ICsFCw=
 github.com/btcsuite/go-socks v0.0.0-20170105172521-4720035b7bfd/go.mod h1:HHNXQzUsZCxOoE+CPiyCTO6x34Zs86zZUiwtpXoGdtg=
@@ -179,14 +181,14 @@ github.com/lightninglabs/protobuf-hex-display v1.3.3-0.20191212020323-b444784ce7
 github.com/lightninglabs/protobuf-hex-display v1.3.3-0.20191212020323-b444784ce75d/go.mod h1:KDb67YMzoh4eudnzClmvs2FbiLG9vxISmLApUkCa4uI=
 github.com/lightningnetwork/lightning-onion v1.0.2-0.20200501022730-3c8c8d0b89ea h1:oCj48NQ8u7Vz+MmzHqt0db6mxcFZo3Ho7M5gCJauY/k=
 github.com/lightningnetwork/lightning-onion v1.0.2-0.20200501022730-3c8c8d0b89ea/go.mod h1:rigfi6Af/KqsF7Za0hOgcyq2PNH4AN70AaMRxcJkff4=
-github.com/lightningnetwork/lnd v0.11.0-beta h1:pUAT7FMHqS+iarNxyRtgj96XKCGAWwmb6ZdiUBy78ts=
 github.com/lightningnetwork/lnd v0.11.0-beta/go.mod h1:CzArvT7NFDLhVyW06+NJWSuWFmE6Ea+AjjA3txUBqTM=
+github.com/lightningnetwork/lnd v0.11.0-beta.rc4.0.20200911014924-bc6e52888763 h1:OUWOTo2BAcsnEaMQIf4gLktU3zGytx6pXrmjUNpZpdg=
+github.com/lightningnetwork/lnd v0.11.0-beta.rc4.0.20200911014924-bc6e52888763/go.mod h1:IvrqVCc5tN2on6E7IHhrwyiM7FCHZ92LphZD+v88LXY=
 github.com/lightningnetwork/lnd/cert v1.0.2/go.mod h1:fmtemlSMf5t4hsQmcprSoOykypAPp+9c+0d0iqTScMo=
 github.com/lightningnetwork/lnd/cert v1.0.3 h1:/K2gjzLgVI8we2IIPKc0ztWTEa85uds5sWXi1K6mOT0=
 github.com/lightningnetwork/lnd/cert v1.0.3/go.mod h1:3MWXVLLPI0Mg0XETm9fT4N9Vyy/8qQLmaM5589bEggM=
 github.com/lightningnetwork/lnd/clock v1.0.1 h1:QQod8+m3KgqHdvVMV+2DRNNZS1GRFir8mHZYA+Z2hFo=
 github.com/lightningnetwork/lnd/clock v1.0.1/go.mod h1:KnQudQ6w0IAMZi1SgvecLZQZ43ra2vpDNj7H/aasemg=
-github.com/lightningnetwork/lnd/queue v1.0.1 h1:jzJKcTy3Nj5lQrooJ3aaw9Lau3I0IwvQR5sqtjdv2R0=
 github.com/lightningnetwork/lnd/queue v1.0.1/go.mod h1:vaQwexir73flPW43Mrm7JOgJHmcEFBWWSl9HlyASoms=
 github.com/lightningnetwork/lnd/queue v1.0.4 h1:8Dq3vxAFSACPy+pKN88oPFhuCpCoAAChPBwa4BJxH4k=
 github.com/lightningnetwork/lnd/queue v1.0.4/go.mod h1:YTkTVZCxz8tAYreH27EO3s8572ODumWrNdYW2E/YKxg=
@@ -246,7 +248,6 @@ github.com/stretchr/objx v0.2.0 h1:Hbg2NidpLE8veEBkEZTL3CvlkUIVzuU9jDplZO54c48=
 github.com/stretchr/objx v0.2.0/go.mod h1:qt09Ya8vawLte6SNmTgCsAVtYtaKzEcn8ATUoHMkEqE=
 github.com/stretchr/testify v1.2.2/go.mod h1:a8OnRcib4nhh0OaRAV+Yts87kKdq0PP7pXfy6kDkUVs=
 github.com/stretchr/testify v1.3.0/go.mod h1:M5WIy9Dh21IEIfnGCwXGc5bZfKNJtfHm1UVUgZn+9EI=
-github.com/stretchr/testify v1.4.0 h1:2E4SXV/wtOkTonXsotYi4li6zVWxYlZuYNCXe9XRJyk=
 github.com/stretchr/testify v1.4.0/go.mod h1:j7eGeouHqKxXV5pUuKE4zz7dFj8WfuZ+81PSLYec5m4=
 github.com/stretchr/testify v1.5.1 h1:nOGnQDM7FYENwehXlg/kFVnos3rEvtKTjRvOWSzb6H4=
 github.com/stretchr/testify v1.5.1/go.mod h1:5W2xD1RspED5o8YsWQXVCued0rvSQ+mT+I5cxcmMvtA=
@@ -259,7 +260,6 @@ github.com/urfave/cli v1.20.0 h1:fDqGv3UG/4jbVl/QkFwEdddtEDjh/5Ov6X+0B/3bPaw=
 github.com/urfave/cli v1.20.0/go.mod h1:70zkFmudgCuE/ngEzBv17Jvp/497gISqfk5gWijbERA=
 github.com/xiang90/probing v0.0.0-20190116061207-43a291ad63a2 h1:eY9dn8+vbi4tKz5Qo6v2eYzo7kUS51QINcR5jNpbZS8=
 github.com/xiang90/probing v0.0.0-20190116061207-43a291ad63a2/go.mod h1:UETIi67q53MR2AWcXfiuqkDkRtnGDLqkBTpCHuJHxtU=
-go.etcd.io/bbolt v1.3.3 h1:MUGmc65QhB3pIlaQ5bB4LwqSj6GIonVJXpZiaKNyaKk=
 go.etcd.io/bbolt v1.3.3/go.mod h1:IbVyRI1SCnLcuJnV2u8VeU0CEYM7e686BmAb1XKL+uU=
 go.etcd.io/bbolt v1.3.5-0.20200615073812-232d8fc87f50 h1:ASw9n1EHMftwnP3Az4XW6e308+gNsrHzmdhd0Olz9Hs=
 go.etcd.io/bbolt v1.3.5-0.20200615073812-232d8fc87f50/go.mod h1:G5EMThwa9y8QZGBClrRx5EY+Yw9kAhnjy3bSjsnlVTQ=

loopd/config.go

@@ -57,6 +57,16 @@ var (
 	DefaultTLSKeyPath = filepath.Join(
 		LoopDirBase, DefaultNetwork, DefaultTLSKeyFilename,
 	)
+
+	// DefaultMacaroonFilename is the default file name for the
+	// autogenerated loop macaroon.
+	DefaultMacaroonFilename = "loop.macaroon"
+
+	// DefaultMacaroonPath is the default full path of the base loop
+	// macaroon.
+	DefaultMacaroonPath = filepath.Join(
+		LoopDirBase, DefaultNetwork, DefaultMacaroonFilename,
+	)
 )
 
 type lndConfig struct {
@@ -82,7 +92,7 @@ type Config struct {
 	RESTListen  string `long:"restlisten" description:"Address to listen on for REST clients"`
 	CORSOrigin  string `long:"corsorigin" description:"The value to send in the Access-Control-Allow-Origin header. Header will be omitted if empty."`
 
-	LoopDir    string `long:"loopdir" description:"The directory for all of loop's data. If set, this option overwrites --datadir, --logdir, --tlscertpath and --tlskeypath."`
+	LoopDir    string `long:"loopdir" description:"The directory for all of loop's data. If set, this option overwrites --datadir, --logdir, --tlscertpath, --tlskeypath and --macaroonpath."`
 	ConfigFile string `long:"configfile" description:"Path to configuration file."`
 	DataDir    string `long:"datadir" description:"Directory for loopdb."`
 
@@ -93,6 +103,8 @@ type Config struct {
 	TLSAutoRefresh     bool     `long:"tlsautorefresh" description:"Re-generate TLS certificate and key if the IPs or domains are changed."`
 	TLSDisableAutofill bool     `long:"tlsdisableautofill" description:"Do not include the interface IPs or the system hostname in TLS certificate, use first --tlsextradomain as Common Name instead, if set."`
 
+	MacaroonPath string `long:"macaroonpath" description:"Path to write the macaroon for loop's RPC and REST services if it doesn't exist."`
+
 	LogDir         string `long:"logdir" description:"Directory to log output."`
 	MaxLogFiles    int    `long:"maxlogfiles" description:"Maximum logfiles to keep (0 for no rotation)."`
 	MaxLogFileSize int    `long:"maxlogfilesize" description:"Maximum logfile size in MB."`
@@ -133,6 +145,7 @@ func DefaultConfig() Config {
 		DebugLevel:      defaultLogLevel,
 		TLSCertPath:     DefaultTLSCertPath,
 		TLSKeyPath:      DefaultTLSKeyPath,
+		MacaroonPath:    DefaultMacaroonPath,
 		MaxLSATCost:     lsat.DefaultMaxCostSats,
 		MaxLSATFee:      lsat.DefaultMaxRoutingFeeSats,
 		LoopOutMaxParts: defaultLoopOutMaxParts,
@@ -193,9 +206,9 @@ func Validate(cfg *Config) error {
 	cfg.DataDir = filepath.Join(cfg.DataDir, cfg.Network)
 	cfg.LogDir = filepath.Join(cfg.LogDir, cfg.Network)
 
-	// We want the TLS files to also be in the "namespaced" sub directory.
-	// Replace the default values with actual values in case the user
-	// specified either loopdir or datadir.
+	// We want the TLS and macaroon files to also be in the "namespaced" sub
+	// directory. Replace the default values with actual values in case the
+	// user specified either loopdir or datadir.
 	if cfg.TLSCertPath == DefaultTLSCertPath {
 		cfg.TLSCertPath = filepath.Join(
 			cfg.DataDir, DefaultTLSCertFilename,
@@ -206,6 +219,11 @@ func Validate(cfg *Config) error {
 			cfg.DataDir, DefaultTLSKeyFilename,
 		)
 	}
+	if cfg.MacaroonPath == DefaultMacaroonPath {
+		cfg.MacaroonPath = filepath.Join(
+			cfg.DataDir, DefaultMacaroonFilename,
+		)
+	}
 
 	// If either of these directories do not exist, create them.
 	if err := os.MkdirAll(cfg.DataDir, os.ModePerm); err != nil {

loopd/daemon.go

@@ -16,7 +16,9 @@ import (
 	"github.com/lightninglabs/loop"
 	"github.com/lightninglabs/loop/looprpc"
 	"github.com/lightningnetwork/lnd/lntypes"
+	"github.com/lightningnetwork/lnd/macaroons"
 	"google.golang.org/grpc"
+	"gopkg.in/macaroon-bakery.v2/bakery"
 )
 
 var (
@@ -79,6 +81,8 @@ type Daemon struct {
 	restServer    *http.Server
 	restListener  net.Listener
 	restCtxCancel func()
+
+	macaroonService *macaroons.Service
 }
 
 // New creates a new instance of the loop client daemon.
@@ -167,13 +171,29 @@ func (d *Daemon) StartAsSubserver(lndGrpc *lndclient.GrpcLndServices) error {
 	return d.initialize()
 }
 
+// ValidateMacaroon extracts the macaroon from the context's gRPC metadata,
+// checks its signature, makes sure all specified permissions for the called
+// method are contained within and finally ensures all caveat conditions are
+// met. A non-nil error is returned if any of the checks fail. This method is
+// needed to enable loopd running as an external subserver in the same process
+// as lnd but still validate its own macaroons.
+func (d *Daemon) ValidateMacaroon(ctx context.Context,
+	requiredPermissions []bakery.Op, fullMethod string) error {
+
+	// Delegate the call to loop's own macaroon validator service.
+	return d.macaroonService.ValidateMacaroon(
+		ctx, requiredPermissions, fullMethod,
+	)
+}
+
 // startWebServers starts the gRPC and REST servers in goroutines.
 func (d *Daemon) startWebServers() error {
 	var err error
 
 	// With our client created, let's now finish setting up and start our
-	// RPC server.
-	serverOpts := []grpc.ServerOption{}
+	// RPC server. First we add the security interceptor to our gRPC server
+	// options that checks the macaroons for validity.
+	serverOpts := d.macaroonInterceptor()
 	d.grpcServer = grpc.NewServer(serverOpts...)
 	looprpc.RegisterSwapClientServer(d.grpcServer, d)
 
@@ -322,6 +342,17 @@ func (d *Daemon) initialize() error {
 	// stop on main context cancel. So we create it early and pass it down.
 	d.mainCtx, d.mainCtxCancel = context.WithCancel(context.Background())
 
+	// Start the macaroon service and let it create its default macaroon in
+	// case it doesn't exist yet.
+	err = d.startMacaroonService()
+	if err != nil {
+		// The client is the only thing we started yet, so if we clean
+		// up its connection now, nothing else needs to be shut down at
+		// this point.
+		clientCleanup()
+		return err
+	}
+
 	// Now finally fully initialize the swap client RPC server instance.
 	d.swapClientServer = swapClientServer{
 		impl:         swapclient,
@@ -336,9 +367,13 @@ func (d *Daemon) initialize() error {
 	// Retrieve all currently existing swaps from the database.
 	swapsList, err := d.impl.FetchSwaps()
 	if err != nil {
-		// The client is the only thing we started yet, so if we clean
-		// up its connection now, nothing else needs to be shut down at
-		// this point.
+		// The client and the macaroon service are the only things we
+		// started yet, so if we clean that up now, nothing else needs
+		// to be shut down at this point.
+		if err := d.stopMacaroonService(); err != nil {
+			log.Errorf("Error shutting down macaroon service: %v",
+				err)
+		}
 		clientCleanup()
 		return err
 	}
@@ -443,6 +478,11 @@ func (d *Daemon) stop() {
 		d.restCtxCancel()
 	}
 
+	err := d.macaroonService.Close()
+	if err != nil {
+		log.Errorf("Error stopping macaroon service: %v", err)
+	}
+
 	// Next, shut down the connections to lnd and the swap server.
 	if d.lnd != nil {
 		d.lnd.Close()