Building a Basic Password Cracker with Python

A fun and practical guide to the basics of the pwd and crypt libraries.

Introduction

In the vast digital landscape, Unix or Linux systems often play a major role in our infrastructure. With admin permission over one of these devices, you could easily find yourself with the capability to wreak some serious havoc. On systems like these, the gatekeeper between you and complete control is often just a password. In this tutorial, we’ll explore how to crack those passwords using Python.

Prerequisites

Before we dive into the code, let’s cover the basics. We’ll be using two Python libraries: pwd and crypt. If you’re not familiar with them, don’t worry—I’ll explain everything step by step.

The pwd Library

The pwd library provides access to the Unix password database. It allows us to retrieve user information, including encrypted passwords. We’ll use it to simulate a login scenario.

Simulating a Login

import pwd
import crypt
import getpass

def login():
    username = input('Enter your username: ')
    try:
        user_info = pwd.getpwnam(username)
        crypted_passwd = user_info.sp_pwdp
        if crypted_passwd == 'x' or crypted_passwd == '*'…