flask-simple-captcha 4.1.2

Extremely simple, "Good Enough" captcha implemention for flask forms. No server side sessions required.

flask-simple-captcha

CURRENT VERSION: v4.1.2

flask-simple-captcha is a robust CAPTCHA generator class for generating and validating CAPTCHAs. It allows for easy integration into Flask applications.

Features

• Generates CAPTCHAs with customizable length and characters
• Easy integration with Flask applications
• Built-in image rendering and line drawing for added complexity
• Base64 image encoding for easy embedding into HTML
• JWT-based verification for secure CAPTCHA checks
• Successfully submitted CAPTCHAs are stored in-memory to prevent resubmission
• Backwards compatible with 1.0 versions of this package

Prerequisites

• Python 3.7 or higher
• Pillow library for image manipulation

Installation

Import this package directly into your Flask project and make sure to install all dependencies.

How to Use

Configuration

DEFAULT_CONFIG = {
    'SECRET_CAPTCHA_KEY': 'CHANGEME - 40 or 50 character long key here',
    'CAPTCHA_LENGTH': 6,
    'CAPTCHA_DIGITS': False,
    # 'EXPIRE_MINUTES': 10,
    'UNIQUE_SALT_LENGTH': 16,
    # 10 minutes, EXPIRE_SECONDS will take prioritity over EXPIRE_MINUTES
    # if both are set.
    'EXPIRE_SECONDS': 60 * 10,
}

# Normalize jwt expiration time to seconds
if 'EXPIRE_NORMALIZED' not in DEFAULT_CONFIG:
    EXPIRE_NORMALIZED = DEFAULT_CONFIG.get('EXPIRE_SECONDS', 60 * 10)
    DEFAULT_CONFIG['EXPIRE_NORMALIZED'] = EXPIRE_NORMALIZED

Initialization

Add this code snippet at the top of your application:

from flask_simple_captcha import CAPTCHA
SIMPLE_CAPTCHA = CAPTCHA(config=config.CAPTCHA_CONFIG)
app = SIMPLE_CAPTCHA.init_app(app)

Protecting a Route

To add CAPTCHA protection to a route, you can use the following code:

@app.route('/example', methods=['GET','POST'])
def example():
    if request.method == 'GET':
        new_captcha_dict = SIMPLE_CAPTCHA.create()
        render_template('example.html', captcha=new_captcha_dict)
    if request.method == 'POST':
        c_hash = request.form.get('captcha-hash')
        c_text = request.form.get('captcha-text')
        if SIMPLE_CAPTCHA.verify(c_text, c_hash):
            return 'success'
        else:
            return 'failed captcha'

In your HTML template, you need to wrap the CAPTCHA inputs within a form element. The package will only generate the CAPTCHA inputs but not the surrounding form or the submit button.

<!-- your_template.html -->
<form action="/example" method="post">
  {{ captcha_html(captcha)|safe }}
  <input type="submit" value="Submit">
</form>

Debugging

You can run debug_flask_server.py for minimal testing on port 5000. This allows you to test the generated CAPTCHA HTML and submission behavior.

# Might want to use venv
pip3 install -r requirements_dev.txt

python3 debug_flask_server.py

Running Tests

1. Install the development requirements:

pip install -r requirements_dev.txt

2. Run the tests:

python3 tests.py

or

python3 -m unittest tests.py

Contributing

Feel free to open a PR. The project has undergone a recent overhaul to improve the code quality.

License

MIT

Contact: [e-mail]