fix: set random session secret if not set (ngoduykhanh#417)

Author: ngoduykhanh

main.go

@@ -38,7 +38,7 @@ var (
 	flagSendgridApiKey string
 	flagEmailFrom      string
 	flagEmailFromName  string = "WireGuard UI"
-	flagSessionSecret  string
+	flagSessionSecret  string = util.RandomString(32)
 	flagWgConfTemplate string
 	flagBasePath       string
 )

util/util.go

@@ -9,6 +9,7 @@ import (
 	"io"
 	"io/fs"
 	"io/ioutil"
+	"math/rand"
 	"net"
 	"os"
 	"path"
@@ -529,3 +530,13 @@ func UpdateHashes(db store.IStore) error {
 	clientServerHashes.Client, clientServerHashes.Server = GetCurrentHash(db)
 	return db.SaveHashes(clientServerHashes)
 }
+
+func RandomString(length int) string {
+	var seededRand = rand.New(rand.NewSource(time.Now().UnixNano()))
+	charset := "abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789"
+	b := make([]byte, length)
+	for i := range b {
+		b[i] = charset[seededRand.Intn(len(charset))]
+	}
+	return string(b)
+}