Secure Username & Password Login

TL;DR

This guide shows you how to build a secure username and password login system. We’ll cover storing passwords safely, handling logins, and protecting against common attacks.

1. Choosing a Secure Password Storage Method

Never store passwords directly in your database! Use a strong hashing algorithm like bcrypt or Argon2.

• bcrypt: A well-established choice, widely supported.
• Argon2: More modern and generally considered more secure, but may require more setup.

Most programming languages have libraries to help with this.

# Example using Python's bcrypt library

import bcrypt

hashed_password = bcrypt.hashpw(b'your_password', bcrypt.gensalt())
print(hashed_password)

2. Implementing the Login Process

1. User Input: Get the username and password from the user (e.g., via a login form).
2. Retrieve User: Find the user in your database based on their username.
3. Password Verification: Compare the entered password with the stored hashed password using the same hashing algorithm.

   # Example using Python's bcrypt library

   import bcrypt
   
   if bcrypt.checkpw(b'entered_password', stored_hashed_password):
     print("Password matches!")
   else:
     print("Incorrect password.")

4. Session Management: If the password is correct, create a secure session for the user. Do not store the password in the session – only a unique session ID.

3. Protecting Against Common Attacks

1. Brute-Force Attacks: Limit login attempts from a single IP address or username to prevent attackers from guessing passwords repeatedly.
   • Implement rate limiting (e.g., 5 failed attempts in 10 minutes).
   • Consider using CAPTCHAs after multiple failures.
2. SQL Injection: Always use parameterized queries or prepared statements when interacting with your database to prevent attackers from injecting malicious SQL code.

   # Example (Python - using a placeholder)

   import sqlite3
   conn = sqlite3.connect('mydatabase.db')
   c = conn.cursor()
   c.execute("SELECT * FROM users WHERE username = ?", (username,)) # Safe!

3. Cross-Site Scripting (XSS): Sanitize user input to prevent attackers from injecting malicious JavaScript code into your website.
   • Escape HTML characters.
   • Use a Content Security Policy (CSP).
4. Cross-Site Request Forgery (CSRF): Use CSRF tokens to protect against attackers from forging requests on behalf of logged-in users.
   • Generate a unique token for each user session.
   • Include the token in all forms and verify it on submission.

4. Additional Security Measures

• Two-Factor Authentication (2FA): Add an extra layer of security by requiring users to enter a code from their phone or email in addition to their password.
• Password Complexity Requirements: Enforce strong passwords with minimum length, mixed case letters, numbers and symbols.
• Regular Security Audits: Regularly review your code and infrastructure for vulnerabilities.