snapshot of https://github.com/grpc/grpc-go.git (master, 2026-09-15; blobs > 131072B omitted)

security/advancedtls/examples/credential_reloading_from_files/README.md

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+# Credential Reloading From Files
+
+Credential reloading is a feature supported in the advancedtls library.
+A very common way to achieve this is to reload from files.
+
+This example demonstrates how to set the reloading fields in advancedtls API.
+Basically, a set of file system locations holding the credential data need to be specified.
+Once the credential data needs to be updated, users just change the credential data in the file system, and gRPC will pick up the changes automatically.
+
+A couple of things to note:
+ 1. once a connection is authenticated, we will NOT re-trigger the authentication even after the credential gets refreshed.
+ 2. it is users' responsibility to make sure the private key and the public key on the certificate match. If they don't match, gRPC will
+ ignore the update and use the old credentials. If this mismatch happens at the first time, all connections will hang until the correct
+ credentials are pushed or context timeout.
+
+## Try it
+In directory `security/advancedtls/examples`:
+
+```
+go run server/main.go
+```
+
+```
+go run client/main.go
+```

security/advancedtls/examples/credential_reloading_from_files/client/main.go

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+/*
+ *
+ * Copyright 2020 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.
+ *
+ */
+
+// The client demonstrates how to use the credential reloading feature in
+// advancedtls to make a mTLS connection to the server.
+package main
+
+import (
+	"context"
+	"flag"
+	"log"
+	"time"
+
+	"google.golang.org/grpc"
+	"google.golang.org/grpc/credentials/tls/certprovider/pemfile"
+	pb "google.golang.org/grpc/examples/helloworld/helloworld"
+	"google.golang.org/grpc/security/advancedtls"
+	"google.golang.org/grpc/security/advancedtls/testdata"
+)
+
+var address = "localhost:50051"
+
+const (
+	// Default timeout for normal connections.
+	defaultTimeout = 2 * time.Second
+	// Intervals that set to monitor the credential updates.
+	credRefreshingInterval = 500 * time.Millisecond
+)
+
+func main() {
+	tmpKeyFile := flag.String("key", "", "temporary key file path")
+	tmpCertFile := flag.String("cert", "", "temporary cert file path")
+	flag.Parse()
+
+	if tmpKeyFile == nil || *tmpKeyFile == "" {
+		log.Fatalf("tmpKeyFile is nil or empty.")
+	}
+	if tmpCertFile == nil || *tmpCertFile == "" {
+		log.Fatalf("tmpCertFile is nil or empty.")
+	}
+
+	// Initialize credential struct using reloading API.
+	identityOptions := pemfile.Options{
+		CertFile:        *tmpCertFile,
+		KeyFile:         *tmpKeyFile,
+		RefreshDuration: credRefreshingInterval,
+	}
+	identityProvider, err := pemfile.NewProvider(identityOptions)
+	if err != nil {
+		log.Fatalf("pemfile.NewProvider(%v) failed: %v", identityOptions, err)
+	}
+	rootOptions := pemfile.Options{
+		RootFile:        testdata.Path("client_trust_cert_1.pem"),
+		RefreshDuration: credRefreshingInterval,
+	}
+	rootProvider, err := pemfile.NewProvider(rootOptions)
+	if err != nil {
+		log.Fatalf("pemfile.NewProvider(%v) failed: %v", rootOptions, err)
+	}
+	options := &advancedtls.Options{
+		IdentityOptions: advancedtls.IdentityCertificateOptions{
+			IdentityProvider: identityProvider,
+		},
+		AdditionalPeerVerification: func(*advancedtls.HandshakeVerificationInfo) (*advancedtls.PostHandshakeVerificationResults, error) {
+			return &advancedtls.PostHandshakeVerificationResults{}, nil
+		},
+		RootOptions: advancedtls.RootCertificateOptions{
+			RootProvider: rootProvider,
+		},
+		VerificationType: advancedtls.CertVerification,
+	}
+	clientTLSCreds, err := advancedtls.NewClientCreds(options)
+	if err != nil {
+		log.Fatalf("advancedtls.NewClientCreds(%v) failed: %v", options, err)
+	}
+
+	// Make a connection using the credentials.
+	conn, err := grpc.NewClient(address, grpc.WithTransportCredentials(clientTLSCreds))
+	if err != nil {
+		log.Fatalf("grpc.NewClient to %s failed: %v", address, err)
+	}
+	client := pb.NewGreeterClient(conn)
+
+	// Send the requests every 0.5s. The credential is expected to be changed in
+	// the bash script. We don't cancel the context nor call conn.Close() here,
+	// since the bash script is expected to close the client goroutine.
+	for {
+		ctx, cancel := context.WithTimeout(context.Background(), defaultTimeout)
+		_, err = client.SayHello(ctx, &pb.HelloRequest{Name: "gRPC"}, grpc.WaitForReady(true))
+		if err != nil {
+			log.Fatalf("client.SayHello failed: %v", err)
+		}
+		cancel()
+		time.Sleep(500 * time.Millisecond)
+	}
+}

security/advancedtls/examples/credential_reloading_from_files/server/main.go

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+/*
+ *
+ * Copyright 2020 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.
+ *
+ */
+
+// The server demonstrates how to use the credential reloading feature in
+// advancedtls to serve mTLS connections from the client.
+package main
+
+import (
+	"context"
+	"flag"
+	"fmt"
+	"log"
+	"net"
+	"time"
+
+	"google.golang.org/grpc"
+	"google.golang.org/grpc/credentials/tls/certprovider/pemfile"
+	"google.golang.org/grpc/keepalive"
+	"google.golang.org/grpc/security/advancedtls"
+	"google.golang.org/grpc/security/advancedtls/testdata"
+
+	pb "google.golang.org/grpc/examples/helloworld/helloworld"
+)
+
+var port = ":50051"
+
+// Intervals that set to monitor the credential updates.
+const credRefreshingInterval = 1 * time.Minute
+
+type greeterServer struct {
+	pb.UnimplementedGreeterServer
+}
+
+// sayHello is a simple implementation of the pb.GreeterServer SayHello method.
+func (greeterServer) SayHello(_ context.Context, in *pb.HelloRequest) (*pb.HelloReply, error) {
+	return &pb.HelloReply{Message: "Hello " + in.Name}, nil
+}
+
+func main() {
+	flag.Parse()
+	fmt.Printf("server starting on port %s...\n", port)
+
+	identityOptions := pemfile.Options{
+		CertFile:        testdata.Path("server_cert_1.pem"),
+		KeyFile:         testdata.Path("server_key_1.pem"),
+		RefreshDuration: credRefreshingInterval,
+	}
+	identityProvider, err := pemfile.NewProvider(identityOptions)
+	if err != nil {
+		log.Fatalf("pemfile.NewProvider(%v) failed: %v", identityOptions, err)
+	}
+	defer identityProvider.Close()
+	rootOptions := pemfile.Options{
+		RootFile:        testdata.Path("server_trust_cert_1.pem"),
+		RefreshDuration: credRefreshingInterval,
+	}
+	rootProvider, err := pemfile.NewProvider(rootOptions)
+	if err != nil {
+		log.Fatalf("pemfile.NewProvider(%v) failed: %v", rootOptions, err)
+	}
+	defer rootProvider.Close()
+
+	// Start a server and create a client using advancedtls API with Provider.
+	options := &advancedtls.Options{
+		IdentityOptions: advancedtls.IdentityCertificateOptions{
+			IdentityProvider: identityProvider,
+		},
+		RootOptions: advancedtls.RootCertificateOptions{
+			RootProvider: rootProvider,
+		},
+		RequireClientCert: true,
+		AdditionalPeerVerification: func(params *advancedtls.HandshakeVerificationInfo) (*advancedtls.PostHandshakeVerificationResults, error) {
+			// This message is to show the certificate under the hood is actually reloaded.
+			fmt.Printf("Client common name: %s.\n", params.Leaf.Subject.CommonName)
+			return &advancedtls.PostHandshakeVerificationResults{}, nil
+		},
+		VerificationType: advancedtls.CertVerification,
+	}
+	serverTLSCreds, err := advancedtls.NewServerCreds(options)
+	if err != nil {
+		log.Fatalf("advancedtls.NewServerCreds(%v) failed: %v", options, err)
+	}
+	s := grpc.NewServer(grpc.Creds(serverTLSCreds), grpc.KeepaliveParams(keepalive.ServerParameters{
+		// Set the max connection time to be 0.5 s to force the client to
+		// re-establish the connection, and hence re-invoke the verification
+		// callback.
+		MaxConnectionAge: 500 * time.Millisecond,
+	}))
+	lis, err := net.Listen("tcp", port)
+	if err != nil {
+		log.Fatalf("failed to listen: %v", err)
+	}
+	pb.RegisterGreeterServer(s, greeterServer{})
+	if err := s.Serve(lis); err != nil {
+		log.Fatalf("failed to serve: %v", err)
+	}
+}