flask-simple-captcha 4.1.1

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

flask-simple-captcha

CURRENT VERSION: v4.1.0

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

The CAPTCHA class can be configured with the following options:

DEFAULT_CONFIG = {
    'SECRET_CAPTCHA_KEY': 'CHANGEME - 40 or 50 character long key here',
    'METHOD': 'pbkdf2:sha256:100',
    '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,
}

Then later:

# normalize jwt expiration time to seconds
if 'EXPIRE_NORMALIZED' not in DEFAULT_CONFIG:
    if 'EXPIRE_MINUTES' in DEFAULT_CONFIG and 'EXPIRE_SECONDS' not in DEFAULT_CONFIG:
        EXPIRE_NORMALIZED = DEFAULT_CONFIG['EXPIRE_MINUTES'] * 60
    else:
        EXPIRE_NORMALIZED = DEFAULT_CONFIG['EXPIRE_SECONDS']

    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, use the following code:

@app.route('/example', methods=['GET','POST'])
def example():
    if request.method == 'GET':
        captcha = SIMPLE_CAPTCHA.create()
        render_template('example.html', captcha=captcha)
    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, include the following:

<!-- your_template.html -->
<div class="captcha-container">{{ captcha_html|safe }}</div>

License

MIT

---

Running Tests

1. Install the development requirements:

pip install -r requirements_dev.txt

2. Run the tests:

python3 tests.py

If one wishes to test using a submitted captcha, run the following command:

python3 debug_flask_server

Contributing

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

License

MIT

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