Adding tls support for akms-ckms client and server

Description

Related Issue

Motivation and Context

How Has This Been Tested?

Screenshots (if appropriate):

Types of changes

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to change)

Checklist:

• My code follows the code style of this project.
• My change requires a change to the documentation.
• I have updated the documentation accordingly.
• I have read the CONTRIBUTING document.
• I have added tests to cover my changes.
• All new and existing tests passed.

akms-simulator/akms-simulator.go

 package main
 
 import (
+	"crypto/tls"
+	"crypto/x509"
 	"encoding/json"
+	"flag"
 	"io"
-	"log"
 	"net/http"
 	"os"
 
@@ -26,11 +28,53 @@ type KSAKey struct {
 }
 
 func main() {
+	tlsCAFile := flag.String("ca", "", "Path to CA certificate file")
+	tlsCertFile := flag.String("cert", "", "Path to certificate file")
+	tlsKeyFile := flag.String("key", "", "Path to key file")
+	flag.Parse()
+
 	logrus.Info("Starting AKMS Simulator...")
 
-	http.HandleFunc("/api/v1/keys/push_ksa_key", handlePushKsaKey)
-	http.HandleFunc("/debug/get_log_file", getLogFile)
-	log.Fatal(http.ListenAndServe(":4444", nil))
+	router := http.NewServeMux()
+
+	router.HandleFunc("/api/v1/keys/push_ksa_key", handlePushKsaKey)
+	router.HandleFunc("/debug/get_log_file", getLogFile)
+
+	server := &http.Server{
+		Addr:    ":4444",
+		Handler: router,
+	}
+
+	if *tlsCAFile != "" && *tlsCertFile != "" && *tlsKeyFile != "" {
+		logrus.Info("TLS enabled")
+		cp := x509.NewCertPool()
+		b, err := os.ReadFile(*tlsCAFile)
+		if err != nil {
+			logrus.Fatalf("Error reading CA file: %s", err)
+		}
+
+		if !cp.AppendCertsFromPEM(b) {
+			logrus.Fatalf("Error appending certs from PEM")
+		}
+
+		cert, err := tls.LoadX509KeyPair(*tlsCertFile, *tlsKeyFile)
+		if err != nil {
+			logrus.Fatalf("Error loading X509 key pair: %s", err)
+		}
+
+		tlsConfig := &tls.Config{
+			MinVersion:   tls.VersionTLS13,
+			ClientCAs:    cp,
+			Certificates: []tls.Certificate{cert},
+			ClientAuth:   tls.RequireAndVerifyClientCert,
+		}
+
+		server.TLSConfig = tlsConfig
+
+		logrus.Fatal(server.ListenAndServeTLS("", ""))
+	} else {
+		logrus.Fatal(server.ListenAndServe())
+	}
 }
 
 func getLogFile(w http.ResponseWriter, r *http.Request) {