examples/features/encryption/mTLS/client/main.go

/*
 *
 * Copyright 2022 gRPC authors.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 *
 */

// Binary client is an example client which connects to the server using mTLS.
package main

import (
	"context"
	"crypto/tls"
	"crypto/x509"
	"flag"
	"fmt"
	"log"
	"os"
	"time"

	"google.golang.org/grpc"
	"google.golang.org/grpc/credentials"
	"google.golang.org/grpc/examples/data"
	ecpb "google.golang.org/grpc/examples/features/proto/echo"
)

var addr = flag.String("addr", "localhost:50051", "the address to connect to")

func callUnaryEcho(client ecpb.EchoClient, message string) {
	ctx, cancel := context.WithTimeout(context.Background(), 10*time.Second)
	defer cancel()
	resp, err := client.UnaryEcho(ctx, &ecpb.EchoRequest{Message: message})
	if err != nil {
		log.Fatalf("client.UnaryEcho(_) = _, %v: ", err)
	}
	fmt.Println("UnaryEcho: ", resp.Message)
}

func main() {
	flag.Parse()

	cert, err := tls.LoadX509KeyPair(data.Path("x509/client_cert.pem"), data.Path("x509/client_key.pem"))
	if err != nil {
		log.Fatalf("failed to load client cert: %v", err)
	}

	ca := x509.NewCertPool()
	caFilePath := data.Path("x509/ca_cert.pem")
	caBytes, err := os.ReadFile(caFilePath)
	if err != nil {
		log.Fatalf("failed to read ca cert %q: %v", caFilePath, err)
	}
	if ok := ca.AppendCertsFromPEM(caBytes); !ok {
		log.Fatalf("failed to parse %q", caFilePath)
	}

	tlsConfig := &tls.Config{
		ServerName:   "x.test.example.com",
		Certificates: []tls.Certificate{cert},
		RootCAs:      ca,
	}

	conn, err := grpc.NewClient(*addr, grpc.WithTransportCredentials(credentials.NewTLS(tlsConfig)))
	if err != nil {
		log.Fatalf("did not connect: %v", err)
	}
	defer conn.Close()

	callUnaryEcho(ecpb.NewEchoClient(conn), "hello world")
}