challenger: move challenger logic to its own package

The new package contains a new interface (`Challenger`) that any
new challenger must implement.

Because aperture uses the new interface instead of using directly the
`LndChallenger` struct I added the `Stop()` method to the
`mint.Challenger`. Instead of also adding the `Start()` method the constructor
returns a Challenger already "started".

aperture.go

@@ -21,6 +21,7 @@ import (
 	flags "github.com/jessevdk/go-flags"
 	"github.com/lightninglabs/aperture/aperturedb"
 	"github.com/lightninglabs/aperture/auth"
+	"github.com/lightninglabs/aperture/challenger"
 	"github.com/lightninglabs/aperture/mint"
 	"github.com/lightninglabs/aperture/proxy"
 	"github.com/lightninglabs/lightning-node-connect/hashmailrpc"
@@ -76,6 +77,10 @@ const (
 	// hashMailRESTPrefix is the prefix a REST request URI has when it is
 	// meant for the hashmailrpc server to be handled.
 	hashMailRESTPrefix = "/v1/lightning-node-connect/hashmail"
+
+	// invoiceMacaroonName is the name of the invoice macaroon belonging
+	// to the target lnd node.
+	invoiceMacaroonName = "invoice.macaroon"
 )
 
 var (
@@ -163,7 +168,7 @@ type Aperture struct {
 
 	etcdClient    *clientv3.Client
 	db            *sql.DB
-	challenger    *LndChallenger
+	challenger    challenger.Challenger
 	httpsServer   *http.Server
 	torHTTPServer *http.Server
 	proxy         *proxy.Proxy
@@ -284,37 +289,32 @@ func (a *Aperture) Start(errChan chan error) error {
 
 	log.Infof("Using %v as database backend", a.cfg.DatabaseBackend)
 
-	// Create our challenger that uses our backing lnd node to create
-	// invoices and check their settlement status.
-	genInvoiceReq := func(price int64) (*lnrpc.Invoice, error) {
-		return &lnrpc.Invoice{
-			Memo:  "LSAT",
-			Value: price,
-		}, nil
-	}
-
 	if !a.cfg.Authenticator.Disable {
+		genInvoiceReq := func(price int64) (*lnrpc.Invoice, error) {
+			return &lnrpc.Invoice{
+				Memo:  "LSAT",
+				Value: price,
+			}, nil
+		}
+
 		authCfg := a.cfg.Authenticator
 		client, err := lndclient.NewBasicClient(
-			authCfg.LndHost, authCfg.TLSPath, authCfg.MacDir,
-			authCfg.Network, lndclient.MacFilename(
+			authCfg.LndHost, authCfg.TLSPath,
+			authCfg.MacDir, authCfg.Network,
+			lndclient.MacFilename(
 				invoiceMacaroonName,
 			),
 		)
 		if err != nil {
 			return err
 		}
-
-		a.challenger, err = NewLndChallenger(
-			client, genInvoiceReq, context.Background, errChan,
+		a.challenger, err = challenger.NewLndChallenger(
+			client, genInvoiceReq, context.Background,
+			errChan,
 		)
 		if err != nil {
 			return err
 		}
-		err = a.challenger.Start()
-		if err != nil {
-			return err
-		}
 	}
 
 	// Create the proxy and connect it to lnd.
@@ -750,7 +750,7 @@ func initTorListener(cfg *Config, store tor.OnionStore) (*tor.Controller,
 }
 
 // createProxy creates the proxy with all the services it needs.
-func createProxy(cfg *Config, challenger *LndChallenger,
+func createProxy(cfg *Config, challenger challenger.Challenger,
 	store mint.SecretStore) (*proxy.Proxy, func(), error) {
 
 	minter := mint.New(&mint.Config{

challenger/interface.go

@@ -0,0 +1,38 @@
+package challenger
+
+import (
+	"context"
+
+	"github.com/lightninglabs/aperture/auth"
+	"github.com/lightninglabs/aperture/mint"
+	"github.com/lightningnetwork/lnd/lnrpc"
+	"google.golang.org/grpc"
+)
+
+// InvoiceRequestGenerator is a function type that returns a new request for the
+// lnrpc.AddInvoice call.
+type InvoiceRequestGenerator func(price int64) (*lnrpc.Invoice, error)
+
+// InvoiceClient is an interface that only implements part of a full lnd client,
+// namely the part around the invoices we need for the challenger to work.
+type InvoiceClient interface {
+	// ListInvoices returns a paginated list of all invoices known to lnd.
+	ListInvoices(ctx context.Context, in *lnrpc.ListInvoiceRequest,
+		opts ...grpc.CallOption) (*lnrpc.ListInvoiceResponse, error)
+
+	// SubscribeInvoices subscribes to updates on invoices.
+	SubscribeInvoices(ctx context.Context, in *lnrpc.InvoiceSubscription,
+		opts ...grpc.CallOption) (
+		lnrpc.Lightning_SubscribeInvoicesClient, error)
+
+	// AddInvoice adds a new invoice to lnd.
+	AddInvoice(ctx context.Context, in *lnrpc.Invoice,
+		opts ...grpc.CallOption) (*lnrpc.AddInvoiceResponse, error)
+}
+
+// Challenger is an interface that combines the mint.Challenger and the
+// auth.InvoiceChecker interfaces.
+type Challenger interface {
+	mint.Challenger
+	auth.InvoiceChecker
+}

challenger/lnd.go

@@ -1,4 +1,4 @@
-package aperture
+package challenger
 
 import (
 	"context"
@@ -9,34 +9,10 @@ import (
 	"sync"
 	"time"
 
-	"github.com/lightninglabs/aperture/auth"
-	"github.com/lightninglabs/aperture/mint"
 	"github.com/lightningnetwork/lnd/lnrpc"
 	"github.com/lightningnetwork/lnd/lntypes"
-	"google.golang.org/grpc"
 )
 
-// InvoiceRequestGenerator is a function type that returns a new request for the
-// lnrpc.AddInvoice call.
-type InvoiceRequestGenerator func(price int64) (*lnrpc.Invoice, error)
-
-// InvoiceClient is an interface that only implements part of a full lnd client,
-// namely the part around the invoices we need for the challenger to work.
-type InvoiceClient interface {
-	// ListInvoices returns a paginated list of all invoices known to lnd.
-	ListInvoices(ctx context.Context, in *lnrpc.ListInvoiceRequest,
-		opts ...grpc.CallOption) (*lnrpc.ListInvoiceResponse, error)
-
-	// SubscribeInvoices subscribes to updates on invoices.
-	SubscribeInvoices(ctx context.Context, in *lnrpc.InvoiceSubscription,
-		opts ...grpc.CallOption) (
-		lnrpc.Lightning_SubscribeInvoicesClient, error)
-
-	// AddInvoice adds a new invoice to lnd.
-	AddInvoice(ctx context.Context, in *lnrpc.Invoice,
-		opts ...grpc.CallOption) (*lnrpc.AddInvoiceResponse, error)
-}
-
 // LndChallenger is a challenger that uses an lnd backend to create new LSAT
 // payment challenges.
 type LndChallenger struct {
@@ -55,16 +31,9 @@ type LndChallenger struct {
 	wg   sync.WaitGroup
 }
 
-// A compile time flag to ensure the LndChallenger satisfies the
-// mint.Challenger and auth.InvoiceChecker interface.
-var _ mint.Challenger = (*LndChallenger)(nil)
-var _ auth.InvoiceChecker = (*LndChallenger)(nil)
-
-const (
-	// invoiceMacaroonName is the name of the invoice macaroon belonging
-	// to the target lnd node.
-	invoiceMacaroonName = "invoice.macaroon"
-)
+// A compile time flag to ensure the LndChallenger satisfies the Challenger
+// interface.
+var _ Challenger = (*LndChallenger)(nil)
 
 // NewLndChallenger creates a new challenger that uses the given connection to
 // an lnd backend to create payment challenges.
@@ -84,7 +53,7 @@ func NewLndChallenger(client InvoiceClient,
 	}
 
 	invoicesMtx := &sync.Mutex{}
-	return &LndChallenger{
+	challenger := &LndChallenger{
 		client:        client,
 		clientCtx:     ctxFunc,
 		genInvoiceReq: genInvoiceReq,
@@ -93,7 +62,14 @@ func NewLndChallenger(client InvoiceClient,
 		invoicesCond:  sync.NewCond(invoicesMtx),
 		quit:          make(chan struct{}),
 		errChan:       errChan,
-	}, nil
+	}
+
+	err := challenger.Start()
+	if err != nil {
+		return nil, fmt.Errorf("unable to start challenger: %w", err)
+	}
+
+	return challenger, nil
 }
 
 // Start starts the challenger's main work which is to keep track of all
@@ -263,7 +239,9 @@ func (l *LndChallenger) Stop() {
 // request (invoice) and the corresponding payment hash.
 //
 // NOTE: This is part of the mint.Challenger interface.
-func (l *LndChallenger) NewChallenge(price int64) (string, lntypes.Hash, error) {
+func (l *LndChallenger) NewChallenge(price int64) (string, lntypes.Hash,
+	error) {
+
 	// Obtain a new invoice from lnd first. We need to know the payment hash
 	// so we can add it as a caveat to the macaroon.
 	invoice, err := l.genInvoiceReq(price)

challenger/lnd_test.go

@@ -1,4 +1,4 @@
-package aperture
+package challenger
 
 import (
 	"context"

challenger/log.go

@@ -0,0 +1,26 @@
+package challenger
+
+import (
+	"github.com/btcsuite/btclog"
+	"github.com/lightningnetwork/lnd/build"
+)
+
+// Subsystem defines the sub system name of this package.
+const Subsystem = "CHLL"
+
+// log is a logger that is initialized with no output filters.  This
+// means the package will not perform any logging by default until the caller
+// requests it.
+var log btclog.Logger
+
+// The default amount of logging is none.
+func init() {
+	UseLogger(build.NewSubLogger(Subsystem, nil))
+}
+
+// UseLogger uses a specified Logger to output package logging info.
+// This should be used in preference to SetLogWriter if the caller is also
+// using btclog.
+func UseLogger(logger btclog.Logger) {
+	log = logger
+}

mint/mint.go

@@ -29,6 +29,9 @@ type Challenger interface {
 	// to avoid having to decode the payment request in order to retrieve
 	// its payment hash.
 	NewChallenge(price int64) (string, lntypes.Hash, error)
+
+	// Stop shuts down the challenger.
+	Stop()
 }
 
 // SecretStore is the store responsible for storing LSAT secrets. These secrets
@@ -36,12 +39,14 @@ type Challenger interface {
 type SecretStore interface {
 	// NewSecret creates a new cryptographically random secret which is
 	// keyed by the given hash.
-	NewSecret(context.Context, [sha256.Size]byte) ([lsat.SecretSize]byte, error)
+	NewSecret(context.Context, [sha256.Size]byte) ([lsat.SecretSize]byte,
+		error)
 
 	// GetSecret returns the cryptographically random secret that
 	// corresponds to the given hash. If there is no secret, then
 	// ErrSecretNotFound is returned.
-	GetSecret(context.Context, [sha256.Size]byte) ([lsat.SecretSize]byte, error)
+	GetSecret(context.Context, [sha256.Size]byte) ([lsat.SecretSize]byte,
+		error)
 
 	// RevokeSecret removes the cryptographically random secret that
 	// corresponds to the given hash. This acts as a NOP if the secret does
@@ -55,16 +60,19 @@ type ServiceLimiter interface {
 	// ServiceCapabilities returns the capabilities caveats for each
 	// service. This determines which capabilities of each service can be
 	// accessed.
-	ServiceCapabilities(context.Context, ...lsat.Service) ([]lsat.Caveat, error)
+	ServiceCapabilities(context.Context, ...lsat.Service) ([]lsat.Caveat,
+		error)
 
 	// ServiceConstraints returns the constraints for each service. This
 	// enforces additional constraints on a particular service/service
 	// capability.
-	ServiceConstraints(context.Context, ...lsat.Service) ([]lsat.Caveat, error)
+	ServiceConstraints(context.Context, ...lsat.Service) ([]lsat.Caveat,
+		error)
 
 	// ServiceTimeouts returns the timeout caveat for each service. This
 	// will determine if and when service access can expire.
-	ServiceTimeouts(context.Context, ...lsat.Service) ([]lsat.Caveat, error)
+	ServiceTimeouts(context.Context, ...lsat.Service) ([]lsat.Caveat,
+		error)
 }
 
 // Config packages all of the required dependencies to instantiate a new LSAT
@@ -245,7 +253,9 @@ type VerificationParams struct {
 }
 
 // VerifyLSAT attempts to verify an LSAT with the given parameters.
-func (m *Mint) VerifyLSAT(ctx context.Context, params *VerificationParams) error {
+func (m *Mint) VerifyLSAT(ctx context.Context,
+	params *VerificationParams) error {
+
 	// We'll first perform a quick check to determine if a valid preimage
 	// was provided.
 	id, err := lsat.DecodeIdentifier(bytes.NewReader(params.Macaroon.Id()))

mint/mock_test.go

@@ -26,7 +26,17 @@ func newMockChallenger() *mockChallenger {
 	return &mockChallenger{}
 }
 
-func (d *mockChallenger) NewChallenge(price int64) (string, lntypes.Hash, error) {
+func (d *mockChallenger) Start() error {
+	return nil
+}
+
+func (d *mockChallenger) Stop() {
+	// Nothing to do here.
+}
+
+func (d *mockChallenger) NewChallenge(price int64) (string, lntypes.Hash,
+	error) {
+
 	return testPayReq, testHash, nil
 }