Merge pull request #145 from guggero/stream-interceptor

lsat: add stream interceptor

lsat/interceptor.go

@@ -89,6 +89,15 @@ func NewInterceptor(lnd *lndclient.LndServices, store Store,
 	}
 }
 
+// interceptContext is a struct that contains all information about a call that
+// is intercepted by the interceptor.
+type interceptContext struct {
+	mainCtx  context.Context
+	opts     []grpc.CallOption
+	metadata *metadata.MD
+	token    *Token
+}
+
 // UnaryInterceptor is an interceptor method that can be used directly by gRPC
 // for unary calls. If the store contains a token, it is attached as credentials
 // to every call before patching it through. The response error is also
@@ -105,21 +114,100 @@ func (i *Interceptor) UnaryInterceptor(ctx context.Context, method string,
 	i.lock.Lock()
 	defer i.lock.Unlock()
 
-	addLsatCredentials := func(token *Token) error {
+	// Create the context that we'll use to initiate the real request. This
-		macaroon, err := token.PaidMacaroon()
+	// contains the means to extract response headers and possibly also an
+	// auth token, if we already have paid for one.
+	iCtx, err := i.newInterceptContext(ctx, opts)
 	if err != nil {
 		return err
 	}
-		opts = append(opts, grpc.PerRPCCredentials(
+
-			macaroons.NewMacaroonCredential(macaroon),
+	// Try executing the call now. If anything goes wrong, we only handle
-		))
+	// the LSAT error message that comes in the form of a gRPC status error.
-		return nil
+	rpcCtx, cancel := context.WithTimeout(ctx, i.callTimeout)
+	defer cancel()
+	err = invoker(rpcCtx, method, req, reply, cc, iCtx.opts...)
+	if !isPaymentRequired(err) {
+		return err
+	}
+
+	// Find out if we need to pay for a new token or perhaps resume
+	// a previously aborted payment.
+	err = i.handlePayment(iCtx)
+	if err != nil {
+		return err
+	}
+
+	// Execute the same request again, now with the LSAT
+	// token added as an RPC credential.
+	rpcCtx2, cancel2 := context.WithTimeout(ctx, i.callTimeout)
+	defer cancel2()
+	return invoker(rpcCtx2, method, req, reply, cc, iCtx.opts...)
+}
+
+// StreamInterceptor is an interceptor method that can be used directly by gRPC
+// for streaming calls. If the store contains a token, it is attached as
+// credentials to every stream establishment call before patching it through.
+// The response error is also intercepted for every initial stream initiation.
+// If there is an error returned and it is indicating a payment challenge, a
+// token is acquired and paid for automatically. The original request is then
+// repeated back to the server, now with the new token attached.
+func (i *Interceptor) StreamInterceptor(ctx context.Context,
+	desc *grpc.StreamDesc, cc *grpc.ClientConn, method string,
+	streamer grpc.Streamer, opts ...grpc.CallOption) (grpc.ClientStream,
+	error) {
+
+	// To avoid paying for a token twice if two parallel requests are
+	// happening, we require an exclusive lock here.
+	i.lock.Lock()
+	defer i.lock.Unlock()
+
+	// Create the context that we'll use to initiate the real request. This
+	// contains the means to extract response headers and possibly also an
+	// auth token, if we already have paid for one.
+	iCtx, err := i.newInterceptContext(ctx, opts)
+	if err != nil {
+		return nil, err
+	}
+
+	// Try establishing the stream now. If anything goes wrong, we only
+	// handle the LSAT error message that comes in the form of a gRPC status
+	// error. The context of a stream will be used for the whole lifetime of
+	// it, so we can't really clamp down on the initial call with a timeout.
+	stream, err := streamer(ctx, desc, cc, method, iCtx.opts...)
+	if !isPaymentRequired(err) {
+		return stream, err
+	}
+
+	// Find out if we need to pay for a new token or perhaps resume
+	// a previously aborted payment.
+	err = i.handlePayment(iCtx)
+	if err != nil {
+		return nil, err
+	}
+
+	// Execute the same request again, now with the LSAT token added
+	// as an RPC credential.
+	return streamer(ctx, desc, cc, method, iCtx.opts...)
+}
+
+// newInterceptContext creates the initial intercept context that can capture
+// metadata from the server and sends the local token to the server if one
+// already exists.
+func (i *Interceptor) newInterceptContext(ctx context.Context,
+	opts []grpc.CallOption) (*interceptContext, error) {
+
+	iCtx := &interceptContext{
+		mainCtx:  ctx,
+		opts:     opts,
+		metadata: &metadata.MD{},
 	}
 
 	// Let's see if the store already contains a token and what state it
 	// might be in. If a previous call was aborted, we might have a pending
 	// token that needs to be handled separately.
-	token, err := i.store.CurrentToken()
+	var err error
+	iCtx.token, err = i.store.CurrentToken()
 	switch {
 	// If there is no token yet, nothing to do at this point.
 	case err == ErrNoToken:
@@ -127,16 +215,18 @@ func (i *Interceptor) UnaryInterceptor(ctx context.Context, method string,
 	// Some other error happened that we have to surface.
 	case err != nil:
 		log.Errorf("Failed to get token from store: %v", err)
-		return fmt.Errorf("getting token from store failed: %v", err)
+		return nil, fmt.Errorf("getting token from store failed: %v",
+			err)
 
 	// Only if we have a paid token append it. We don't resume a pending
 	// payment just yet, since we don't even know if a token is required for
 	// this call. We also never send a pending payment to the server since
 	// we know it's not valid.
-	case !token.isPending():
+	case !iCtx.token.isPending():
-		if err = addLsatCredentials(token); err != nil {
+		if err = i.addLsatCredentials(iCtx); err != nil {
 			log.Errorf("Adding macaroon to request failed: %v", err)
-			return fmt.Errorf("adding macaroon failed: %v", err)
+			return nil, fmt.Errorf("adding macaroon failed: %v",
+				err)
 		}
 	}
 
@@ -145,60 +235,59 @@ func (i *Interceptor) UnaryInterceptor(ctx context.Context, method string,
 	// option. We execute the request and inspect the error. If it's the
 	// LSAT specific payment required error, we might execute the same
 	// method again later with the paid LSAT token.
-	trailerMetadata := &metadata.MD{}
+	iCtx.opts = append(iCtx.opts, grpc.Trailer(iCtx.metadata))
-	opts = append(opts, grpc.Trailer(trailerMetadata))
+	return iCtx, nil
-	rpcCtx, cancel := context.WithTimeout(ctx, i.callTimeout)
-	defer cancel()
-	err = invoker(rpcCtx, method, req, reply, cc, opts...)
-
-	// Only handle the LSAT error message that comes in the form of
-	// a gRPC status error.
-	if isPaymentRequired(err) {
-		paidToken, err := i.handlePayment(ctx, token, trailerMetadata)
-		if err != nil {
-			return err
-		}
-		if err = addLsatCredentials(paidToken); err != nil {
-			log.Errorf("Adding macaroon to request failed: %v", err)
-			return fmt.Errorf("adding macaroon failed: %v", err)
-		}
-
-		// Execute the same request again, now with the LSAT
-		// token added as an RPC credential.
-		rpcCtx2, cancel2 := context.WithTimeout(ctx, i.callTimeout)
-		defer cancel2()
-		return invoker(rpcCtx2, method, req, reply, cc, opts...)
-	}
-	return err
 }
 
 // handlePayment tries to obtain a valid token by either tracking the payment
 // status of a pending token or paying for a new one.
-func (i *Interceptor) handlePayment(ctx context.Context, token *Token,
+func (i *Interceptor) handlePayment(iCtx *interceptContext) error {
-	md *metadata.MD) (*Token, error) {
-
 	switch {
 	// Resume/track a pending payment if it was interrupted for some reason.
-	case token != nil && token.isPending():
+	case iCtx.token != nil && iCtx.token.isPending():
 		log.Infof("Payment of LSAT token is required, resuming/" +
 			"tracking previous payment from pending LSAT token")
-		err := i.trackPayment(ctx, token)
+		err := i.trackPayment(iCtx.mainCtx, iCtx.token)
 		if err != nil {
-			return nil, err
+			return err
 		}
-		return token, nil
 
 	// We don't have a token yet, try to get a new one.
-	case token == nil:
+	case iCtx.token == nil:
 		// We don't have a token yet, get a new one.
 		log.Infof("Payment of LSAT token is required, paying invoice")
-		return i.payLsatToken(ctx, md)
+		var err error
+		iCtx.token, err = i.payLsatToken(iCtx.mainCtx, iCtx.metadata)
+		if err != nil {
+			return err
+		}
 
 	// We have a token and it's valid, nothing more to do here.
 	default:
 		log.Debugf("Found valid LSAT token to add to request")
-		return token, nil
 	}
+
+	if err := i.addLsatCredentials(iCtx); err != nil {
+		log.Errorf("Adding macaroon to request failed: %v", err)
+		return fmt.Errorf("adding macaroon failed: %v", err)
+	}
+	return nil
+}
+
+// addLsatCredentials adds an LSAT token to the given intercept context.
+func (i *Interceptor) addLsatCredentials(iCtx *interceptContext) error {
+	if iCtx.token == nil {
+		return fmt.Errorf("cannot add nil token to context")
+	}
+
+	macaroon, err := iCtx.token.PaidMacaroon()
+	if err != nil {
+		return err
+	}
+	iCtx.opts = append(iCtx.opts, grpc.PerRPCCredentials(
+		macaroons.NewMacaroonCredential(macaroon),
+	))
+	return nil
 }
 
 // payLsatToken reads the payment challenge from the response metadata and tries

lsat/interceptor_test.go

@@ -19,6 +19,21 @@ import (
 	"gopkg.in/macaroon.v2"
 )
 
+type interceptTestCase struct {
+	name                string
+	initialPreimage     *lntypes.Preimage
+	interceptor         *Interceptor
+	resetCb             func()
+	expectLndCall       bool
+	sendPaymentCb       func(*testing.T, test.PaymentChannelMessage)
+	trackPaymentCb      func(*testing.T, test.TrackPaymentMessage)
+	expectToken         bool
+	expectInterceptErr  string
+	expectBackendCalls  int
+	expectMacaroonCall1 bool
+	expectMacaroonCall2 bool
+}
+
 type mockStore struct {
 	token *Token
 }
@@ -39,12 +54,7 @@ func (s *mockStore) StoreToken(token *Token) error {
 	return nil
 }
 
-// TestInterceptor tests that the interceptor can handle LSAT protocol responses
+var (
-// and pay the token.
-func TestInterceptor(t *testing.T) {
-	t.Parallel()
-
-	var (
 	lnd         = test.NewMockLnd()
 	store       = &mockStore{}
 	testTimeout = 5 * time.Second
@@ -52,53 +62,21 @@ func TestInterceptor(t *testing.T) {
 		&lnd.LndServices, store, testTimeout,
 		DefaultMaxCostSats, DefaultMaxRoutingFeeSats,
 	)
-		testMac      = makeMac(t)
+	testMac         = makeMac()
-		testMacBytes = serializeMac(t, testMac)
+	testMacBytes    = serializeMac(testMac)
 	testMacHex      = hex.EncodeToString(testMacBytes)
 	paidPreimage    = lntypes.Preimage{1, 2, 3, 4, 5}
-		paidToken    = &Token{
-			Preimage: paidPreimage,
-			baseMac:  testMac,
-		}
-		pendingToken = &Token{
-			Preimage: zeroPreimage,
-			baseMac:  testMac,
-		}
-		backendWg       sync.WaitGroup
 	backendErr      error
 	backendAuth     = ""
 	callMD          map[string]string
 	numBackendCalls = 0
-	)
+	overallWg       sync.WaitGroup
+	backendWg       sync.WaitGroup
 
-	ctx, cancel := context.WithTimeout(context.Background(), testTimeout)
+	testCases = []interceptTestCase{
-	defer cancel()
-
-	// resetBackend is used by the test cases to define the behaviour of the
-	// simulated backend and reset its starting conditions.
-	resetBackend := func(expectedErr error, expectedAuth string) {
-		backendErr = expectedErr
-		backendAuth = expectedAuth
-		callMD = nil
-	}
-
-	testCases := []struct {
-		name                string
-		initialToken        *Token
-		interceptor         *Interceptor
-		resetCb             func()
-		expectLndCall       bool
-		sendPaymentCb       func(msg test.PaymentChannelMessage)
-		trackPaymentCb      func(msg test.TrackPaymentMessage)
-		expectToken         bool
-		expectInterceptErr  string
-		expectBackendCalls  int
-		expectMacaroonCall1 bool
-		expectMacaroonCall2 bool
-	}{
 		{
 			name:                "no auth required happy path",
-			initialToken:        nil,
+			initialPreimage:     nil,
 			interceptor:         interceptor,
 			resetCb:             func() { resetBackend(nil, "") },
 			expectLndCall:       false,
@@ -109,7 +87,7 @@ func TestInterceptor(t *testing.T) {
 		},
 		{
 			name:            "auth required, no token yet",
-			initialToken: nil,
+			initialPreimage: nil,
 			interceptor:     interceptor,
 			resetCb: func() {
 				resetBackend(
@@ -120,7 +98,9 @@ func TestInterceptor(t *testing.T) {
 				)
 			},
 			expectLndCall: true,
-			sendPaymentCb: func(msg test.PaymentChannelMessage) {
+			sendPaymentCb: func(t *testing.T,
+				msg test.PaymentChannelMessage) {
+
 				if len(callMD) != 0 {
 					t.Fatalf("unexpected call metadata: "+
 						"%v", callMD)
@@ -134,7 +114,9 @@ func TestInterceptor(t *testing.T) {
 					PaidFee:  345,
 				}
 			},
-			trackPaymentCb: func(msg test.TrackPaymentMessage) {
+			trackPaymentCb: func(t *testing.T,
+				msg test.TrackPaymentMessage) {
+
 				t.Fatal("didn't expect call to trackPayment")
 			},
 			expectToken:         true,
@@ -144,7 +126,7 @@ func TestInterceptor(t *testing.T) {
 		},
 		{
 			name:                "auth required, has token",
-			initialToken:        paidToken,
+			initialPreimage:     &paidPreimage,
 			interceptor:         interceptor,
 			resetCb:             func() { resetBackend(nil, "") },
 			expectLndCall:       false,
@@ -155,7 +137,7 @@ func TestInterceptor(t *testing.T) {
 		},
 		{
 			name:            "auth required, has pending token",
-			initialToken: pendingToken,
+			initialPreimage: &zeroPreimage,
 			interceptor:     interceptor,
 			resetCb: func() {
 				resetBackend(
@@ -166,10 +148,14 @@ func TestInterceptor(t *testing.T) {
 				)
 			},
 			expectLndCall: true,
-			sendPaymentCb: func(msg test.PaymentChannelMessage) {
+			sendPaymentCb: func(t *testing.T,
+				msg test.PaymentChannelMessage) {
+
 				t.Fatal("didn't expect call to sendPayment")
 			},
-			trackPaymentCb: func(msg test.TrackPaymentMessage) {
+			trackPaymentCb: func(t *testing.T,
+				msg test.TrackPaymentMessage) {
+
 				// The next call to the "backend" shouldn't
 				// return an error.
 				resetBackend(nil, "")
@@ -186,7 +172,7 @@ func TestInterceptor(t *testing.T) {
 		},
 		{
 			name:            "auth required, no token yet, cost limit",
-			initialToken: nil,
+			initialPreimage: nil,
 			interceptor: NewInterceptor(
 				&lnd.LndServices, store, testTimeout,
 				100, DefaultMaxRoutingFeeSats,
@@ -209,15 +195,20 @@ func TestInterceptor(t *testing.T) {
 			expectMacaroonCall2: false,
 		},
 	}
+)
 
-	// The invoker is a simple function that simulates the actual call to
+// resetBackend is used by the test cases to define the behaviour of the
-	// the server. We can track if it's been called and we can dictate what
+// simulated backend and reset its starting conditions.
-	// error it should return.
+func resetBackend(expectedErr error, expectedAuth string) {
-	invoker := func(_ context.Context, _ string, _ interface{},
+	backendErr = expectedErr
-		_ interface{}, _ *grpc.ClientConn,
+	backendAuth = expectedAuth
-		opts ...grpc.CallOption) error {
+	callMD = nil
+}
 
-		defer backendWg.Done()
+// The invoker is a simple function that simulates the actual call to
+// the server. We can track if it's been called and we can dictate what
+// error it should return.
+func invoker(opts []grpc.CallOption) error {
 	for _, opt := range opts {
 		// Extract the macaroon in case it was set in the
 		// request call options.
@@ -238,28 +229,84 @@ func TestInterceptor(t *testing.T) {
 	}
 	numBackendCalls++
 	return backendErr
+}
+
+// TestUnaryInterceptor tests that the interceptor can handle LSAT protocol
+// responses for unary calls and pay the token.
+func TestUnaryInterceptor(t *testing.T) {
+	ctx, cancel := context.WithTimeout(context.Background(), testTimeout)
+	defer cancel()
+
+	unaryInvoker := func(_ context.Context, _ string,
+		_ interface{}, _ interface{}, _ *grpc.ClientConn,
+		opts ...grpc.CallOption) error {
+
+		defer backendWg.Done()
+		return invoker(opts)
 	}
 
 	// Run through the test cases.
 	for _, tc := range testCases {
+		tc := tc
+		intercept := func() error {
+			return tc.interceptor.UnaryInterceptor(
+				ctx, "", nil, nil, nil, unaryInvoker, nil,
+			)
+		}
+		t.Run(tc.name, func(t *testing.T) {
+			testInterceptor(t, tc, intercept)
+		})
+	}
+}
+
+// TestStreamInterceptor tests that the interceptor can handle LSAT protocol
+// responses in streams and pay the token.
+func TestStreamInterceptor(t *testing.T) {
+	ctx, cancel := context.WithTimeout(context.Background(), testTimeout)
+	defer cancel()
+
+	streamInvoker := func(_ context.Context,
+		_ *grpc.StreamDesc, _ *grpc.ClientConn,
+		_ string, opts ...grpc.CallOption) (
+		grpc.ClientStream, error) { // nolint: unparam
+
+		defer backendWg.Done()
+		return nil, invoker(opts)
+	}
+
+	// Run through the test cases.
+	for _, tc := range testCases {
+		tc := tc
+		intercept := func() error {
+			_, err := tc.interceptor.StreamInterceptor(
+				ctx, nil, nil, "", streamInvoker,
+			)
+			return err
+		}
+		t.Run(tc.name, func(t *testing.T) {
+			testInterceptor(t, tc, intercept)
+		})
+	}
+}
+
+func testInterceptor(t *testing.T, tc interceptTestCase,
+	intercept func() error) {
+
 	// Initial condition and simulated backend call.
-		store.token = tc.initialToken
+	store.token = makeToken(tc.initialPreimage)
 	tc.resetCb()
 	numBackendCalls = 0
-		var overallWg sync.WaitGroup
 	backendWg.Add(1)
 	overallWg.Add(1)
 	go func() {
-			err := tc.interceptor.UnaryInterceptor(
+		defer overallWg.Done()
-				ctx, "", nil, nil, nil, invoker, nil,
+		err := intercept()
-			)
 		if err != nil && tc.expectInterceptErr != "" &&
 			err.Error() != tc.expectInterceptErr {
 			panic(fmt.Errorf("unexpected error '%s', "+
 				"expected '%s'", err.Error(),
 				tc.expectInterceptErr))
 		}
-			overallWg.Done()
 	}()
 
 	backendWg.Wait()
@@ -286,10 +333,10 @@ func TestInterceptor(t *testing.T) {
 	if tc.expectLndCall {
 		select {
 		case payment := <-lnd.SendPaymentChannel:
-				tc.sendPaymentCb(payment)
+			tc.sendPaymentCb(t, payment)
 
 		case track := <-lnd.TrackPaymentChannel:
-				tc.trackPaymentCb(track)
+			tc.trackPaymentCb(t, track)
 
 		case <-time.After(testTimeout):
 			t.Fatalf("[%s]: no payment request received",
@@ -299,7 +346,6 @@ func TestInterceptor(t *testing.T) {
 	backendWg.Wait()
 	overallWg.Wait()
 
-		// Interpret result/expectations.
 	if tc.expectToken {
 		if _, err := store.CurrentToken(); err != nil {
 			t.Fatalf("[%s] expected store to contain token",
@@ -327,26 +373,33 @@ func TestInterceptor(t *testing.T) {
 			"expected times", numBackendCalls,
 			tc.expectBackendCalls)
 	}
+}
+
+func makeToken(preimage *lntypes.Preimage) *Token {
+	if preimage == nil {
+		return nil
+	}
+	return &Token{
+		Preimage: *preimage,
+		baseMac:  testMac,
 	}
 }
 
-func makeMac(t *testing.T) *macaroon.Macaroon {
+func makeMac() *macaroon.Macaroon {
 	dummyMac, err := macaroon.New(
 		[]byte("aabbccddeeff00112233445566778899"), []byte("AA=="),
 		"LSAT", macaroon.LatestVersion,
 	)
 	if err != nil {
-		t.Fatalf("unable to create macaroon: %v", err)
+		panic(fmt.Errorf("unable to create macaroon: %v", err))
-		return nil
 	}
 	return dummyMac
 }
 
-func serializeMac(t *testing.T, mac *macaroon.Macaroon) []byte {
+func serializeMac(mac *macaroon.Macaroon) []byte {
 	macBytes, err := mac.MarshalBinary()
 	if err != nil {
-		t.Fatalf("unable to serialize macaroon: %v", err)
+		panic(fmt.Errorf("unable to serialize macaroon: %v", err))
-		return nil
 	}
 	return macBytes
 }

lsat/store_test.go

@@ -23,11 +23,11 @@ func TestFileStore(t *testing.T) {
 		paidPreimage = lntypes.Preimage{1, 2, 3, 4, 5}
 		paidToken    = &Token{
 			Preimage: paidPreimage,
-			baseMac:  makeMac(t),
+			baseMac:  makeMac(),
 		}
 		pendingToken = &Token{
 			Preimage: zeroPreimage,
-			baseMac:  makeMac(t),
+			baseMac:  makeMac(),
 		}
 	)