Add dynamic mtls samples (#349)

README.md

@@ -30,6 +30,8 @@ Each sample demonstrates one feature of the SDK, together with tests.
 - [**Basic mTLS hello world**](./helloworldmtls): Simple example of a
   Workflow Definition and an Activity Definition using mTLS like Temporal Cloud.
 
+- [**Dynamic mTLS hello world**](./dynamicmtls): Simple example showing how to refresh mTLS credentials. This allows for credentials to be refreshed without restarting the worker.
+
 ### API demonstrations
 
 - **Async activity completion**: Example of

dynamicmtls/README.md

@@ -0,0 +1,19 @@
+This sample shows how to connect a client to Temporal using mtls where the certificates are dynamically loaded. This allows the credentials to be replaced without restarting the worker. 
+
+### Steps to run this sample:
+1) Configure a [Temporal Server](https://github.com/temporalio/samples-go/tree/main/#how-to-use) (such as Temporal Cloud) with mTLS.
+
+2) Run the following command to start the worker
+```
+go run ./dynamicmtls/worker -target-host my.namespace.tmprl.cloud:7233 -namespace my.namespace -client-cert path/to/cert.pem -client-key path/to/key.pem
+```
+3) Run the following command to start the example
+```
+go run ./dynamicmtls/starter -target-host my.namespace.tmprl.cloud:7233 -namespace my.namespace -client-cert path/to/cert.pem -client-key path/to/key.pem
+```
+
+Note:
+
+If the server uses self-signed certificates and does not have the SAN set to the actual host, pass one of the following two options when starting the worker or the example above:
+1. `-server-name` and provide the common name contained in the self-signed server certificate
+2. `-insecure-skip-verify` which disables certificate and host name validation

dynamicmtls/dynamicmtls.go

@@ -0,0 +1,63 @@
+package dynamicmtls
+
+import (
+	"crypto/tls"
+	"crypto/x509"
+	"flag"
+	"fmt"
+	"os"
+
+	"go.temporal.io/sdk/client"
+)
+
+// ParseClientOptionFlags parses the given arguments into client options. In
+// some cases a failure will be returned as an error, in others the process may
+// exit with help info.
+func ParseClientOptionFlags(args []string) (client.Options, error) {
+	// Parse args
+	set := flag.NewFlagSet("hello-world-mtls", flag.ExitOnError)
+	targetHost := set.String("target-host", "localhost:7233", "Host:port for the server")
+	namespace := set.String("namespace", "default", "Namespace for the server")
+	serverRootCACert := set.String("server-root-ca-cert", "", "Optional path to root server CA cert")
+	clientCert := set.String("client-cert", "", "Required path to client cert, will be dynamically loaded when server requests a certificate")
+	clientKey := set.String("client-key", "", "Required path to client key, will be dynamically loaded when server requests a certificate")
+	serverName := set.String("server-name", "", "Server name to use for verifying the server's certificate")
+	insecureSkipVerify := set.Bool("insecure-skip-verify", false, "Skip verification of the server's certificate and host name")
+	if err := set.Parse(args); err != nil {
+		return client.Options{}, fmt.Errorf("failed parsing args: %w", err)
+	} else if *clientCert == "" || *clientKey == "" {
+		return client.Options{}, fmt.Errorf("-client-cert and -client-key are required")
+	}
+
+	// Load server CA if given
+	var serverCAPool *x509.CertPool
+	if *serverRootCACert != "" {
+		serverCAPool = x509.NewCertPool()
+		b, err := os.ReadFile(*serverRootCACert)
+		if err != nil {
+			return client.Options{}, fmt.Errorf("failed reading server CA: %w", err)
+		} else if !serverCAPool.AppendCertsFromPEM(b) {
+			return client.Options{}, fmt.Errorf("server CA PEM file invalid")
+		}
+	}
+
+	return client.Options{
+		HostPort:  *targetHost,
+		Namespace: *namespace,
+		ConnectionOptions: client.ConnectionOptions{
+			TLS: &tls.Config{
+				GetClientCertificate: func(*tls.CertificateRequestInfo) (*tls.Certificate, error) {
+					cert, err := tls.LoadX509KeyPair(*clientCert, *clientKey)
+					if err != nil {
+						return nil, fmt.Errorf("failed loading client cert and key: %w", err)
+					}
+					return &cert, nil
+
+				},
+				RootCAs:            serverCAPool,
+				ServerName:         *serverName,
+				InsecureSkipVerify: *insecureSkipVerify,
+			},
+		},
+	}, nil
+}

dynamicmtls/starter/main.go

@@ -0,0 +1,44 @@
+package main
+
+import (
+	"context"
+	"log"
+	"os"
+
+	"github.com/temporalio/samples-go/dynamicmtls"
+	"github.com/temporalio/samples-go/helloworld"
+	"go.temporal.io/sdk/client"
+)
+
+func main() {
+	// The client is a heavyweight object that should be created once per process.
+	clientOptions, err := dynamicmtls.ParseClientOptionFlags(os.Args[1:])
+	if err != nil {
+		log.Fatalf("Invalid arguments: %v", err)
+	}
+	c, err := client.Dial(clientOptions)
+	if err != nil {
+		log.Fatalln("Unable to create client", err)
+	}
+	defer c.Close()
+
+	workflowOptions := client.StartWorkflowOptions{
+		ID:        "hello_world_workflowID",
+		TaskQueue: "hello-world-mtls",
+	}
+
+	we, err := c.ExecuteWorkflow(context.Background(), workflowOptions, helloworld.Workflow, "Temporal")
+	if err != nil {
+		log.Fatalln("Unable to execute workflow", err)
+	}
+
+	log.Println("Started workflow", "WorkflowID", we.GetID(), "RunID", we.GetRunID())
+
+	// Synchronously wait for the workflow completion.
+	var result string
+	err = we.Get(context.Background(), &result)
+	if err != nil {
+		log.Fatalln("Unable get workflow result", err)
+	}
+	log.Println("Workflow result:", result)
+}

dynamicmtls/worker/main.go

@@ -0,0 +1,34 @@
+package main
+
+import (
+	"log"
+	"os"
+
+	"github.com/temporalio/samples-go/dynamicmtls"
+	"github.com/temporalio/samples-go/helloworld"
+	"go.temporal.io/sdk/client"
+	"go.temporal.io/sdk/worker"
+)
+
+func main() {
+	// The client and worker are heavyweight objects that should be created once per process.
+	clientOptions, err := dynamicmtls.ParseClientOptionFlags(os.Args[1:])
+	if err != nil {
+		log.Fatalf("Invalid arguments: %v", err)
+	}
+	c, err := client.Dial(clientOptions)
+	if err != nil {
+		log.Fatalln("Unable to create client", err)
+	}
+	defer c.Close()
+
+	w := worker.New(c, "hello-world-mtls", worker.Options{})
+
+	w.RegisterWorkflow(helloworld.Workflow)
+	w.RegisterActivity(helloworld.Activity)
+
+	err = w.Run(worker.InterruptCh())
+	if err != nil {
+		log.Fatalln("Unable to start worker", err)
+	}
+}