proxy: test HTTP and gRPC proxying

proxy/proxy_test.go

@@ -1,58 +1,98 @@
 package proxy_test
 
 import (
+	"bytes"
+	"context"
+	"crypto/ecdsa"
+	"crypto/elliptic"
+	"crypto/rand"
+	"crypto/tls"
+	"crypto/x509"
+	"crypto/x509/pkix"
+	"encoding/pem"
 	"fmt"
 	"io/ioutil"
+	"math/big"
+	"net"
 	"net/http"
+	"os"
+	"path"
 	"strings"
 	"testing"
 	"time"
 
 	"github.com/lightninglabs/kirin/auth"
 	"github.com/lightninglabs/kirin/proxy"
+	proxytest "github.com/lightninglabs/kirin/proxy/testdata"
+	"github.com/lightningnetwork/lnd/macaroons"
+	"google.golang.org/grpc"
+	"google.golang.org/grpc/codes"
+	"google.golang.org/grpc/credentials"
+	"google.golang.org/grpc/status"
+	"gopkg.in/macaroon.v2"
 )
 
 const (
-	testAddr                 = "localhost:10019"
+	testProxyAddr            = "localhost:10019"
 	testHostRegexp           = "^localhost:.*$"
-	testPathRegexp           = "^/grpc/.*$"
+	testPathRegexpHTTP       = "^/http/.*$"
+	testPathRegexpGRPC       = "^/proxy_test.*$"
 	testTargetServiceAddress = "localhost:8082"
 	testHTTPResponseBody     = "HTTP Hello"
 )
 
-func TestProxy(t *testing.T) {
+var (
+	serialNumberLimit = new(big.Int).Lsh(big.NewInt(1), 128)
+	tlsCipherSuites   = []uint16{
+		tls.TLS_ECDHE_ECDSA_WITH_AES_128_CBC_SHA256,
+		tls.TLS_ECDHE_ECDSA_WITH_AES_128_GCM_SHA256,
+		tls.TLS_ECDHE_ECDSA_WITH_AES_256_GCM_SHA384,
+		tls.TLS_ECDHE_ECDSA_WITH_CHACHA20_POLY1305,
+	}
+)
+
+// helloServer is a simple server that implements the GreeterServer interface.
+type helloServer struct{}
+
+// SayHello returns a simple string that also contains a string from the
+// request.
+func (s *helloServer) SayHello(ctx context.Context,
+	req *proxytest.HelloRequest) (*proxytest.HelloReply, error) {
+
+	return &proxytest.HelloReply{
+		Message: fmt.Sprintf("Hello %s", req.Name),
+	}, nil
+}
+
+// TestProxyHTTP tests that the proxy can forward HTTP requests to a backend
+// service and handle LSAT authentication correctly.
+func TestProxyHTTP(t *testing.T) {
 	// Create a list of services to proxy between.
 	services := []*proxy.Service{{
 		Address:    testTargetServiceAddress,
 		HostRegexp: testHostRegexp,
-		PathRegexp: testPathRegexp,
+		PathRegexp: testPathRegexpHTTP,
 		Protocol:   "http",
 	}}
 
-	auth := auth.NewMockAuthenticator()
-	proxy, err := proxy.New(auth, services, "static")
+	mockAuth := auth.NewMockAuthenticator()
+	p, err := proxy.New(mockAuth, services, "static")
 	if err != nil {
 		t.Fatalf("failed to create new proxy: %v", err)
 	}
 
 	// Start server that gives requests to the proxy.
 	server := &http.Server{
-		Addr:    testAddr,
-		Handler: http.HandlerFunc(proxy.ServeHTTP),
+		Addr:    testProxyAddr,
+		Handler: http.HandlerFunc(p.ServeHTTP),
 	}
-
-	go func() {
-		if err := server.ListenAndServe(); err != nil {
-			t.Fatalf("failed to serve to proxy: %v", err)
-		}
-	}()
+	go server.ListenAndServe()
+	defer server.Close()
 
 	// Start the target backend service.
-	go func() {
-		if err := startHTTPHello(); err != nil {
-			t.Fatalf("failed to start backend service: %v", err)
-		}
-	}()
+	backendService := &http.Server{Addr: testTargetServiceAddress}
+	go startBackendHTTP(backendService)
+	defer backendService.Close()
 
 	// Wait for servers to start.
 	time.Sleep(100 * time.Millisecond)
@@ -60,7 +100,7 @@ func TestProxy(t *testing.T) {
 	// Test making a request to the backend service without the
 	// Authorization header set.
 	client := &http.Client{}
-	url := fmt.Sprintf("http://%s/grpc/test", testAddr)
+	url := fmt.Sprintf("http://%s/http/test", testProxyAddr)
 	resp, err := client.Get(url)
 	if err != nil {
 		t.Fatalf("errored making http request: %v", err)
@@ -79,6 +119,9 @@ func TestProxy(t *testing.T) {
 	// Make sure that if the Auth header is set, the client's request is
 	// proxied to the backend service.
 	req, err := http.NewRequest("GET", url, nil)
+	if err != nil {
+		t.Fatalf("error creating request: %v", err)
+	}
 	req.Header.Add("Authorization", "foobar")
 
 	resp, err = client.Do(req)
@@ -103,10 +146,287 @@ func TestProxy(t *testing.T) {
 	}
 }
 
-func startHTTPHello() error {
+// TestProxyHTTP tests that the proxy can forward gRPC requests to a backend
+// service and handle LSAT authentication correctly.
+func TestProxyGRPC(t *testing.T) {
+	// Since gRPC only really works over TLS, we need to generate a
+	// certificate and key pair first.
+	tempDirName, err := ioutil.TempDir("", "proxytest")
+	if err != nil {
+		t.Fatalf("unable to create temp dir: %v", err)
+	}
+	certFile := path.Join(tempDirName, "proxy.cert")
+	keyFile := path.Join(tempDirName, "proxy.key")
+	certPool, creds, cert, err := genCertPair(certFile, keyFile)
+	if err != nil {
+		t.Fatalf("unable to create cert pair: %v", err)
+	}
+
+	// Create a list of services to proxy between.
+	services := []*proxy.Service{{
+		Address:     testTargetServiceAddress,
+		HostRegexp:  testHostRegexp,
+		PathRegexp:  testPathRegexpGRPC,
+		Protocol:    "https",
+		TLSCertPath: certFile,
+	}}
+
+	// Create the proxy server and start serving on TLS.
+	mockAuth := auth.NewMockAuthenticator()
+	p, err := proxy.New(mockAuth, services, "static")
+	if err != nil {
+		t.Fatalf("failed to create new proxy: %v", err)
+	}
+	server := &http.Server{
+		Addr:    testProxyAddr,
+		Handler: http.HandlerFunc(p.ServeHTTP),
+		TLSConfig: &tls.Config{
+			RootCAs:            certPool,
+			InsecureSkipVerify: true,
+		},
+	}
+	go server.ListenAndServeTLS(certFile, keyFile)
+	defer server.Close()
+
+	// Start the target backend service also on TLS.
+	tlsConf := &tls.Config{
+		Certificates: []tls.Certificate{cert},
+		CipherSuites: tlsCipherSuites,
+		MinVersion:   tls.VersionTLS12,
+	}
+	serverOpts := []grpc.ServerOption{
+		grpc.Creds(credentials.NewTLS(tlsConf)),
+	}
+	backendService := grpc.NewServer(serverOpts...)
+	go startBackendGRPC(backendService)
+	defer backendService.Stop()
+
+	// Dial to the proxy now, without any authentication.
+	opts := []grpc.DialOption{grpc.WithTransportCredentials(creds)}
+	conn, err := grpc.Dial(testProxyAddr, opts...)
+	if err != nil {
+		t.Fatalf("unable to connect to RPC server: %v", err)
+	}
+	client := proxytest.NewGreeterClient(conn)
+
+	// Make request without authentication. We expect an error that can
+	// be parsed by gRPC.
+	req := &proxytest.HelloRequest{Name: "foo"}
+	res, err := client.SayHello(
+		context.Background(), req, grpc.WaitForReady(true),
+	)
+	if err == nil {
+		t.Fatalf("expected error to be returned without auth")
+	}
+	statusErr, ok := status.FromError(err)
+	if !ok {
+		t.Fatalf("expected error to be status.Status")
+	}
+	if statusErr.Code() != codes.Internal {
+		t.Fatalf("unexpected code. wanted %d, got %d",
+			codes.Internal, statusErr.Code())
+	}
+	if statusErr.Message() != "payment required" {
+		t.Fatalf("invalid error. expected [%s] got [%s]",
+			"payment required", err.Error())
+	}
+
+	// Dial to the proxy again, this time with a dummy macaroon.
+	dummyMac, err := macaroon.New(
+		[]byte("key"), []byte("id"), "loc", macaroon.LatestVersion,
+	)
+	opts = []grpc.DialOption{
+		grpc.WithTransportCredentials(creds),
+		grpc.WithPerRPCCredentials(macaroons.NewMacaroonCredential(
+			dummyMac,
+		)),
+	}
+	conn, err = grpc.Dial(testProxyAddr, opts...)
+	if err != nil {
+		t.Fatalf("unable to connect to RPC server: %v", err)
+	}
+	client = proxytest.NewGreeterClient(conn)
+
+	// Make the request. This time no error should be returned.
+	req = &proxytest.HelloRequest{Name: "foo"}
+	res, err = client.SayHello(context.Background(), req)
+	if err != nil {
+		t.Fatalf("unable to call service: %v", err)
+	}
+	if res.Message != "Hello foo" {
+		t.Fatalf("unexpected reply, wanted %s, got %s",
+			"Hello foo", res.Message)
+	}
+}
+
+// startBackendHTTP starts the given HTTP server and blocks until the server
+// is shut down.
+func startBackendHTTP(server *http.Server) error {
 	sayHello := func(w http.ResponseWriter, r *http.Request) {
-		w.Write([]byte(testHTTPResponseBody))
+		_, err := w.Write([]byte(testHTTPResponseBody))
+		if err != nil {
+			panic(err)
 		}
-	http.HandleFunc("/", sayHello)
-	return http.ListenAndServe(testTargetServiceAddress, nil)
+	}
+	server.Handler = http.HandlerFunc(sayHello)
+	return server.ListenAndServe()
+}
+
+// startBackendGRPC starts the given RPC server and blocks until the server is
+// shut down.
+func startBackendGRPC(grpcServer *grpc.Server) error {
+	server := helloServer{}
+	proxytest.RegisterGreeterServer(grpcServer, &server)
+	grpcListener, err := net.Listen("tcp", testTargetServiceAddress)
+	if err != nil {
+		return fmt.Errorf("RPC server unable to listen on %s",
+			testTargetServiceAddress)
+
+	}
+	return grpcServer.Serve(grpcListener)
+}
+
+// genCertPair generates a pair of private key and certificate and returns them
+// in different formats needed to spin up test servers and clients.
+func genCertPair(certFile, keyFile string) (*x509.CertPool,
+	credentials.TransportCredentials, tls.Certificate, error) {
+
+	org := "kirin autogenerated cert"
+	cert := tls.Certificate{}
+	now := time.Now()
+	validUntil := now.Add(1 * time.Hour)
+
+	// Generate a serial number that's below the serialNumberLimit.
+	serialNumber, err := rand.Int(rand.Reader, serialNumberLimit)
+	if err != nil {
+		return nil, nil, cert, fmt.Errorf("failed to generate serial "+
+			"number: %s", err)
+	}
+
+	// Collect the host's IP addresses, including loopback, in a slice.
+	ipAddresses := []net.IP{net.ParseIP("127.0.0.1"), net.ParseIP("::1")}
+
+	// addIP appends an IP address only if it isn't already in the slice.
+	addIP := func(ipAddr net.IP) {
+		for _, ip := range ipAddresses {
+			if ip.Equal(ipAddr) {
+				return
+			}
+		}
+		ipAddresses = append(ipAddresses, ipAddr)
+	}
+
+	// Add all the interface IPs that aren't already in the slice.
+	addrs, err := net.InterfaceAddrs()
+	if err != nil {
+		return nil, nil, cert, err
+	}
+	for _, a := range addrs {
+		ipAddr, _, err := net.ParseCIDR(a.String())
+		if err == nil {
+			addIP(ipAddr)
+		}
+	}
+
+	// Collect the host's names into a slice.
+	host, err := os.Hostname()
+	if err != nil {
+		return nil, nil, cert, err
+	}
+	dnsNames := []string{host}
+	if host != "localhost" {
+		dnsNames = append(dnsNames, "localhost")
+	}
+
+	// Generate a private key for the certificate.
+	priv, err := ecdsa.GenerateKey(elliptic.P256(), rand.Reader)
+	if err != nil {
+		return nil, nil, cert, err
+	}
+
+	// Construct the certificate template.
+	template := x509.Certificate{
+		SerialNumber: serialNumber,
+		Subject: pkix.Name{
+			Organization: []string{org},
+			CommonName:   host,
+		},
+		NotBefore: now.Add(-time.Hour * 24),
+		NotAfter:  validUntil,
+
+		KeyUsage: x509.KeyUsageKeyEncipherment |
+			x509.KeyUsageDigitalSignature | x509.KeyUsageCertSign,
+		IsCA:                  true, // so can sign self.
+		BasicConstraintsValid: true,
+
+		DNSNames:    dnsNames,
+		IPAddresses: ipAddresses,
+	}
+
+	derBytes, err := x509.CreateCertificate(
+		rand.Reader, &template, &template, &priv.PublicKey, priv,
+	)
+	if err != nil {
+		return nil, nil, cert, fmt.Errorf("failed to create "+
+			"certificate: %v", err)
+	}
+
+	certBuf := &bytes.Buffer{}
+	err = pem.Encode(
+		certBuf,
+		&pem.Block{Type: "CERTIFICATE",
+			Bytes: derBytes,
+		},
+	)
+	if err != nil {
+		return nil, nil, cert, fmt.Errorf("failed to encode "+
+			"certificate: %v", err)
+	}
+
+	keybytes, err := x509.MarshalECPrivateKey(priv)
+	if err != nil {
+		return nil, nil, cert, fmt.Errorf("unable to encode privkey: "+
+			"%v", err)
+	}
+	keyBuf := &bytes.Buffer{}
+	err = pem.Encode(
+		keyBuf,
+		&pem.Block{
+			Type:  "EC PRIVATE KEY",
+			Bytes: keybytes,
+		},
+	)
+	if err != nil {
+		return nil, nil, cert, fmt.Errorf("failed to encode private "+
+			"key: %v", err)
+	}
+	cert, err = tls.X509KeyPair(certBuf.Bytes(), keyBuf.Bytes())
+	if err != nil {
+		return nil, nil, cert, fmt.Errorf("failed to create key pair: "+
+			"%v", err)
+	}
+
+	// Write cert and key files.
+	if err = ioutil.WriteFile(certFile, certBuf.Bytes(), 0644); err != nil {
+		return nil, nil, cert, fmt.Errorf("unable to write cert file "+
+			"at %v: %v", certFile, err)
+	}
+	if err = ioutil.WriteFile(keyFile, keyBuf.Bytes(), 0600); err != nil {
+		os.Remove(certFile)
+		return nil, nil, cert, fmt.Errorf("unable to write key file "+
+			"at %v: %v", keyFile, err)
+	}
+
+	cp := x509.NewCertPool()
+	if !cp.AppendCertsFromPEM(certBuf.Bytes()) {
+		return nil, nil, cert, fmt.Errorf("credentials: failed to " +
+			"append certificate")
+	}
+
+	creds, err := credentials.NewClientTLSFromFile(certFile, "")
+	if err != nil {
+		return nil, nil, cert, fmt.Errorf("unable to load cert file: "+
+			"%v", err)
+	}
+	return cp, creds, cert, nil
 }

proxy/testdata/gen_protos.sh

@@ -0,0 +1,8 @@
+#!/bin/sh
+
+set -e
+
+protoc -I/usr/local/include -I. \
+       -I$GOPATH/src/github.com/grpc-ecosystem/grpc-gateway/third_party/googleapis \
+       --go_out=plugins=grpc,paths=source_relative:. \
+       hello.proto

proxy/testdata/hello.pb.go

@@ -0,0 +1,194 @@
+// Code generated by protoc-gen-go. DO NOT EDIT.
+// source: hello.proto
+
+package proxy_test
+
+import (
+	context "context"
+	fmt "fmt"
+	proto "github.com/golang/protobuf/proto"
+	grpc "google.golang.org/grpc"
+	math "math"
+)
+
+// Reference imports to suppress errors if they are not otherwise used.
+var _ = proto.Marshal
+var _ = fmt.Errorf
+var _ = math.Inf
+
+// This is a compile-time assertion to ensure that this generated file
+// is compatible with the proto package it is being compiled against.
+// A compilation error at this line likely means your copy of the
+// proto package needs to be updated.
+const _ = proto.ProtoPackageIsVersion3 // please upgrade the proto package
+
+type HelloRequest struct {
+	Name                 string   `protobuf:"bytes,1,opt,name=name,proto3" json:"name,omitempty"`
+	XXX_NoUnkeyedLiteral struct{} `json:"-"`
+	XXX_unrecognized     []byte   `json:"-"`
+	XXX_sizecache        int32    `json:"-"`
+}
+
+func (m *HelloRequest) Reset()         { *m = HelloRequest{} }
+func (m *HelloRequest) String() string { return proto.CompactTextString(m) }
+func (*HelloRequest) ProtoMessage()    {}
+func (*HelloRequest) Descriptor() ([]byte, []int) {
+	return fileDescriptor_61ef911816e0a8ce, []int{0}
+}
+
+func (m *HelloRequest) XXX_Unmarshal(b []byte) error {
+	return xxx_messageInfo_HelloRequest.Unmarshal(m, b)
+}
+func (m *HelloRequest) XXX_Marshal(b []byte, deterministic bool) ([]byte, error) {
+	return xxx_messageInfo_HelloRequest.Marshal(b, m, deterministic)
+}
+func (m *HelloRequest) XXX_Merge(src proto.Message) {
+	xxx_messageInfo_HelloRequest.Merge(m, src)
+}
+func (m *HelloRequest) XXX_Size() int {
+	return xxx_messageInfo_HelloRequest.Size(m)
+}
+func (m *HelloRequest) XXX_DiscardUnknown() {
+	xxx_messageInfo_HelloRequest.DiscardUnknown(m)
+}
+
+var xxx_messageInfo_HelloRequest proto.InternalMessageInfo
+
+func (m *HelloRequest) GetName() string {
+	if m != nil {
+		return m.Name
+	}
+	return ""
+}
+
+type HelloReply struct {
+	Message              string   `protobuf:"bytes,1,opt,name=message,proto3" json:"message,omitempty"`
+	XXX_NoUnkeyedLiteral struct{} `json:"-"`
+	XXX_unrecognized     []byte   `json:"-"`
+	XXX_sizecache        int32    `json:"-"`
+}
+
+func (m *HelloReply) Reset()         { *m = HelloReply{} }
+func (m *HelloReply) String() string { return proto.CompactTextString(m) }
+func (*HelloReply) ProtoMessage()    {}
+func (*HelloReply) Descriptor() ([]byte, []int) {
+	return fileDescriptor_61ef911816e0a8ce, []int{1}
+}
+
+func (m *HelloReply) XXX_Unmarshal(b []byte) error {
+	return xxx_messageInfo_HelloReply.Unmarshal(m, b)
+}
+func (m *HelloReply) XXX_Marshal(b []byte, deterministic bool) ([]byte, error) {
+	return xxx_messageInfo_HelloReply.Marshal(b, m, deterministic)
+}
+func (m *HelloReply) XXX_Merge(src proto.Message) {
+	xxx_messageInfo_HelloReply.Merge(m, src)
+}
+func (m *HelloReply) XXX_Size() int {
+	return xxx_messageInfo_HelloReply.Size(m)
+}
+func (m *HelloReply) XXX_DiscardUnknown() {
+	xxx_messageInfo_HelloReply.DiscardUnknown(m)
+}
+
+var xxx_messageInfo_HelloReply proto.InternalMessageInfo
+
+func (m *HelloReply) GetMessage() string {
+	if m != nil {
+		return m.Message
+	}
+	return ""
+}
+
+func init() {
+	proto.RegisterType((*HelloRequest)(nil), "proxy_test.HelloRequest")
+	proto.RegisterType((*HelloReply)(nil), "proxy_test.HelloReply")
+}
+
+func init() { proto.RegisterFile("hello.proto", fileDescriptor_61ef911816e0a8ce) }
+
+var fileDescriptor_61ef911816e0a8ce = []byte{
+	// 145 bytes of a gzipped FileDescriptorProto
+	0x1f, 0x8b, 0x08, 0x00, 0x00, 0x00, 0x00, 0x00, 0x02, 0xff, 0xe2, 0xe2, 0xce, 0x48, 0xcd, 0xc9,
+	0xc9, 0xd7, 0x2b, 0x28, 0xca, 0x2f, 0xc9, 0x17, 0xe2, 0x2a, 0x28, 0xca, 0xaf, 0xa8, 0x8c, 0x2f,
+	0x49, 0x2d, 0x2e, 0x51, 0x52, 0xe2, 0xe2, 0xf1, 0x00, 0x49, 0x05, 0xa5, 0x16, 0x96, 0xa6, 0x16,
+	0x97, 0x08, 0x09, 0x71, 0xb1, 0xe4, 0x25, 0xe6, 0xa6, 0x4a, 0x30, 0x2a, 0x30, 0x6a, 0x70, 0x06,
+	0x81, 0xd9, 0x4a, 0x6a, 0x5c, 0x5c, 0x50, 0x35, 0x05, 0x39, 0x95, 0x42, 0x12, 0x5c, 0xec, 0xb9,
+	0xa9, 0xc5, 0xc5, 0x89, 0xe9, 0x30, 0x45, 0x30, 0xae, 0x91, 0x27, 0x17, 0xbb, 0x7b, 0x51, 0x6a,
+	0x6a, 0x49, 0x6a, 0x91, 0x90, 0x1d, 0x17, 0x47, 0x70, 0x62, 0x25, 0x58, 0x97, 0x90, 0x84, 0x1e,
+	0xc2, 0x3e, 0x3d, 0x64, 0xcb, 0xa4, 0xc4, 0xb0, 0xc8, 0x14, 0xe4, 0x54, 0x2a, 0x31, 0x24, 0xb1,
+	0x81, 0x5d, 0x6a, 0x0c, 0x08, 0x00, 0x00, 0xff, 0xff, 0xe3, 0x7f, 0xe6, 0xbe, 0xb8, 0x00, 0x00,
+	0x00,
+}
+
+// Reference imports to suppress errors if they are not otherwise used.
+var _ context.Context
+var _ grpc.ClientConn
+
+// This is a compile-time assertion to ensure that this generated file
+// is compatible with the grpc package it is being compiled against.
+const _ = grpc.SupportPackageIsVersion4
+
+// GreeterClient is the client API for Greeter service.
+//
+// For semantics around ctx use and closing/ending streaming RPCs, please refer to https://godoc.org/google.golang.org/grpc#ClientConn.NewStream.
+type GreeterClient interface {
+	SayHello(ctx context.Context, in *HelloRequest, opts ...grpc.CallOption) (*HelloReply, error)
+}
+
+type greeterClient struct {
+	cc *grpc.ClientConn
+}
+
+func NewGreeterClient(cc *grpc.ClientConn) GreeterClient {
+	return &greeterClient{cc}
+}
+
+func (c *greeterClient) SayHello(ctx context.Context, in *HelloRequest, opts ...grpc.CallOption) (*HelloReply, error) {
+	out := new(HelloReply)
+	err := c.cc.Invoke(ctx, "/proxy_test.Greeter/SayHello", in, out, opts...)
+	if err != nil {
+		return nil, err
+	}
+	return out, nil
+}
+
+// GreeterServer is the server API for Greeter service.
+type GreeterServer interface {
+	SayHello(context.Context, *HelloRequest) (*HelloReply, error)
+}
+
+func RegisterGreeterServer(s *grpc.Server, srv GreeterServer) {
+	s.RegisterService(&_Greeter_serviceDesc, srv)
+}
+
+func _Greeter_SayHello_Handler(srv interface{}, ctx context.Context, dec func(interface{}) error, interceptor grpc.UnaryServerInterceptor) (interface{}, error) {
+	in := new(HelloRequest)
+	if err := dec(in); err != nil {
+		return nil, err
+	}
+	if interceptor == nil {
+		return srv.(GreeterServer).SayHello(ctx, in)
+	}
+	info := &grpc.UnaryServerInfo{
+		Server:     srv,
+		FullMethod: "/proxy_test.Greeter/SayHello",
+	}
+	handler := func(ctx context.Context, req interface{}) (interface{}, error) {
+		return srv.(GreeterServer).SayHello(ctx, req.(*HelloRequest))
+	}
+	return interceptor(ctx, in, info, handler)
+}
+
+var _Greeter_serviceDesc = grpc.ServiceDesc{
+	ServiceName: "proxy_test.Greeter",
+	HandlerType: (*GreeterServer)(nil),
+	Methods: []grpc.MethodDesc{
+		{
+			MethodName: "SayHello",
+			Handler:    _Greeter_SayHello_Handler,
+		},
+	},
+	Streams:  []grpc.StreamDesc{},
+	Metadata: "hello.proto",
+}

proxy/testdata/hello.proto

@@ -0,0 +1,15 @@
+syntax = "proto3";
+
+package proxy_test;
+
+service Greeter {
+    rpc SayHello (HelloRequest) returns (HelloReply) {}
+}
+
+message HelloRequest {
+    string name = 1;
+}
+
+message HelloReply {
+    string message = 1;
+}