Introduction

In this tutorial, our goal is to learn how to hash passwords securely in your Flask application using Flask-Bcrypt. Hashing passwords is a fundamental practice in web development for storing passwords securely.

By the end of this tutorial, you will have learned:
- Basic concepts of hashing and its importance for security
- How to use Flask-Bcrypt in your Flask application
- Best practices for password management

This tutorial assumes you have basic familiarity with Python and Flask. If you are completely new to Flask, I recommend that you first familiarize yourself with its basics.

Step-by-Step Guide

Hashing is the process of converting a given key into another value. A hash function is used to generate the new value, and it is nearly impossible to derive the original key from the hashed value. This makes it highly useful for storing passwords securely.

Flask-Bcrypt is a Flask extension that provides bcrypt hashing utilities for your application. Bcrypt is a powerful, adaptive password hashing algorithm that is particularly resistant to rainbow table attacks.

Here's a step-by-step guide to using Flask-Bcrypt:

1. Install Flask-Bcrypt: You can install Flask-Bcrypt via pip with the following command: pip install flask-bcrypt.

2. Initialize Flask-Bcrypt: In your main application file, import and initialize Flask-Bcrypt. Here's an example:

   ```python
   from flask import Flask
   from flask_bcrypt import Bcrypt

   app = Flask(name)
   bcrypt = Bcrypt(app)
   ```

3. Hash a Password: To hash a password, you use the generate_password_hash method. For example:

   python hashed_password = bcrypt.generate_password_hash('mysecretpassword').decode('utf-8')

4. Check a Password Against a Hash: To check a password, use the check_password_hash method. For example:

   python password_check = bcrypt.check_password_hash(hashed_password, 'mysecretpassword') # Returns True if the password is correct

Code Examples

Here's a full example of a Flask app that uses Flask-Bcrypt for password hashing.

from flask import Flask, request
from flask_bcrypt import Bcrypt

app = Flask(__name__)
bcrypt = Bcrypt(app)

@app.route('/register', methods=['POST'])
def register():
    password = request.form.get('password')
    hashed_password = bcrypt.generate_password_hash(password).decode('utf-8')
    # Here, save the hashed_password to your database
    return 'User registered.'

@app.route('/login', methods=['POST'])
def login():
    password = request.form.get('password')
    # Fetch the hashed_password from your database
    hashed_password = ''
    if bcrypt.check_password_hash(hashed_password, password):
        return 'Login successful.'
    else:
        return 'Login failed.'

if __name__ == '__main__':
    app.run(debug=True)

In the above example, we've created two routes: /register and /login. In the register route, we hash the password and (hypothetically) save it to a database. In the login route, we check the provided password against the stored hash.

Summary

In this tutorial, we learned about password hashing and its importance in securely storing passwords. We learned how to use Flask-Bcrypt to hash passwords and check passwords against a hash.

Next steps for learning could include how to actually save these hashed passwords to a database, how to manage user sessions, and how to use Flask-Login for user authentication.

Practice Exercises

1. Exercise: Create a Flask app that uses Flask-Bcrypt to hash passwords. Have the app include routes for registration and login, and print the hashed password to the console when a user registers.

2. Exercise: Expand on the above app. Instead of printing the hashed password to the console, save it to a file. Then, when the user tries to log in, check the password against the stored hash.

3. Exercise: Further expand on the app. Instead of saving the hashed password to a file, save it to a SQLite database using Flask-SQLAlchemy. Include a route for viewing all registered users and their hashed passwords.

Solutions

The solutions to these exercises are beyond the scope of this tutorial, but I encourage you to try them out and search for tutorials on how to use Flask-SQLAlchemy and manage databases in Flask. These exercises will give you practical experience in using Flask-Bcrypt and managing user data.