update signal gRpc, enable TLS and add keepalive params (#62)

* chore: update signal gRpc
* chore: add Signal keep alive params and policy
* feature: add signal TLS support
* refactor: move signal Dockerfile to the corresponding folder
Co-authored-by: braginini <m.bragin@wiretrustee.com>

cmd/root.go

@@ -1,11 +1,16 @@
 package cmd
 
 import (
+	"crypto/tls"
 	"fmt"
 	log "github.com/sirupsen/logrus"
 	"github.com/spf13/cobra"
+	"golang.org/x/crypto/acme/autocert"
+	"google.golang.org/grpc/credentials"
+	"net/http"
 	"os"
 	"os/signal"
+	"path/filepath"
 	"runtime"
 )
 
@@ -74,3 +79,31 @@ func InitLog(logLevel string) {
 	}
 	log.SetLevel(level)
 }
+
+func enableLetsEncrypt(datadir string, letsencryptDomain string) credentials.TransportCredentials {
+	certDir := filepath.Join(datadir, "letsencrypt")
+
+	if _, err := os.Stat(certDir); os.IsNotExist(err) {
+		err = os.MkdirAll(certDir, os.ModeDir)
+		if err != nil {
+			log.Fatalf("failed creating Let's encrypt certdir: %s: %v", certDir, err)
+		}
+	}
+
+	log.Infof("running with Let's encrypt with domain %s. Cert will be stored in %s", letsencryptDomain, certDir)
+
+	certManager := autocert.Manager{
+		Prompt:     autocert.AcceptTOS,
+		Cache:      autocert.DirCache(certDir),
+		HostPolicy: autocert.HostWhitelist(letsencryptDomain),
+	}
+
+	// listener to handle Let's encrypt certificate challenge
+	go func() {
+		if err := http.Serve(certManager.Listener(), certManager.HTTPHandler(nil)); err != nil {
+			log.Fatalf("failed to serve letsencrypt handler: %v", err)
+		}
+	}()
+
+	return credentials.NewTLS(&tls.Config{GetCertificate: certManager.GetCertificate})
+}