adlin: Pass SharedSecret in env

pkg/login-validator/cmd/login.go

@@ -16,7 +16,7 @@ import (
 )
 
 var (
-	loginSalt string
+	loginSalt string = "adelina"
 	justLogin bool
 )
 

pkg/login-validator/cmd/main.go

@@ -18,13 +18,17 @@ var tftpDir string
 func main() {
 	var studentsFile string
 
+	if v, exists := os.LookupEnv("ADLIN_SHARED_SECRET"); exists {
+		loginSalt = v
+	}
+
 	flag.BoolVar(&justLogin, "just-login", justLogin, "Don't perform MAC assignation and remote registration")
 
 	var bind = flag.String("bind", ":8081", "Bind port/socket")
 	flag.StringVar(&studentsFile, "students", "./students.csv", "Path to a CSV file containing students list")
 	flag.StringVar(&ARPTable, "arp", ARPTable, "Path to ARP table")
 	flag.StringVar(&tftpDir, "tftpdir", "/var/tftp/", "Path to TFTPd directory")
-	flag.StringVar(&loginSalt, "loginsalt", "adelina", "secret used in login HMAC")
+	flag.StringVar(&loginSalt, "loginsalt", loginSalt, "secret used in login HMAC")
 
 	var auth = flag.String("auth", "none", "Auth method: none, fwd, ldap, krb5")