Golang : Get login name from environment and prompt for password

Problem:

You want to write a Golang script(short program for administrating server, etc) that grab the current user's login name, but prompt for a password rather than hardcoding it into the script.

When the user enter the password, it should not have echo or masking(i.e replace the typed characters with *). Once the password has been accepted, the script will compare the password with the retrieved password from database. If the password matched, it will let it pass and perform futher operation. If not, abort.

Discussion:

It is important to prompt the login user for password again whenever the user was about to execute a script that could cause potential damage from wrong usage. Why? Security risk. The real logged in user might have walked away from his/her desktop to somewhere else leaving the terminal open for someone else to use. Such as executing some potential harmful commands. Prompting password again will minimize the security risk. For additional layer on security, you might want to conside implementing 2 Factor Authentication as well.

Solution:

Retrieve the logged-in username from the environment variable with os.Getenv() function. Prompt for password with github.com/howeyc/gopass package.

Here you go!

 package main

 import (
 "fmt"
 "log"
 "github.com/howeyc/gopass"
 "os"
 )

 func authService(username, password string) bool {
 // this where you want to bcrypt the password
 // first before comparing with value retrieved
 // from database or other sources base on the given username

 // -- this will be application specific

 // for the sake of this tutorial, we just
 // put the password as abc123 ( don't use this in production!!)
 // REMEMBER, do not hardcode the password in your script!

 var retrievedPassword string

 if username != "" {
 retrievedPassword = "abc123"
 }

 if password == retrievedPassword {
 return true
 } else {
 return false
 }

 }

 func main() {
 // get login user name
 // from environment variables

 loginUser := os.Getenv("USER")

 if loginUser == "" {
 log.Fatalf("Unable to get username from environment variable.\n")
 }

 // get user to enter their password
 // without echo or mask

 fmt.Printf("Enter your password to execute this script: ")
 passwordFromUser, err := gopass.GetPasswd() // no echo - silent

 if err != nil {
 log.Printf("Get password error %v\n", err)
 }

 authentication := authService(loginUser, string(passwordFromUser))

 fmt.Println("Authenticated ? : ", authentication)

 }

Sample output:

(enter wrong password)

Enter your password to execute this script:

Authenticated ? : false

(enter right password)

Enter your password to execute this script:

Authenticated ? : true

Happy coding!

References:

https://www.socketloop.com/tutorials/golang-set-get-and-list-environment-variables

https://www.socketloop.com/tutorials/golang-get-password-from-console-input-without-echo-or-masked

https://www.socketloop.com/tutorials/golang-check-if-password-length-meet-the-requirement