Flask-Bcrypt

Flask-Bcrypt is a Flask extension that provides bcrypt hashing utilities for your application.

Due to the recent increased prevalence of powerful hardware, such as modern GPUs, hashes have become increasingly easy to crack. A proactive solution to this is to use a hash that was designed to be “de-optimized”. Bcrypt is such a hashing facility; unlike hashing algorithms such as MD5 and SHA1, which are optimized for speed, bcrypt is intentionally structured to be slow.

For sensitive data that must be protected, such as passwords, bcrypt is an advisable choice.

Installation

Install using pip:

$ pip install Bcrypt-Flask

Note

You need Python Development Headers to install py-bcrypt package, needed as a dependency. If you are on Mac OS or Windows, you probably have it already installed. Otherwise look for python-dev package for Debian-based distributives and for python-devel package for RedHat-based.

Usage

To use the extension simply import the class wrapper and pass the Flask app object back to here. Do so like this:

from flask import Flask
from flask_bcrypt import Bcrypt

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

Two primary hashing methods are now exposed by way of the bcrypt object. In Python 2, use them like so:

pw_hash = bcrypt.generate_password_hash('hunter2')
bcrypt.check_password_hash(pw_hash, 'hunter2') # returns True

In Python 3, you need to use decode(‘utf-8’) on generate_password_hash(), like below:

pw_hash = bcrypt.generate_password_hash(‘hunter2’).decode(‘utf-8’)

API

Configuration

(Flask config)

  • BCRYPT_LOG_ROUNDS: default 12

  • BCRYPT_HASH_PREFIX: default '2b'

  • BCRYPT_HANDLE_LONG_PASSWORDS: default False. By default, the bcrypt algorithm has a maximum password length of 72 bytes and ignores any bytes beyond that. A common workaround is to hash the given password using a cryptographic hash (such as sha256), take its hexdigest to prevent NULL byte problems, and hash the result with bcrypt. If the BCRYPT_HANDLE_LONG_PASSWORDS configuration value is set to True, the workaround described above will be enabled. Warning: do not enable this option on a project that is already using Flask-Bcrypt, or you will break password checking. Warning: if this option is enabled on an existing project, disabling it will break password checking.