Python bcrypt package on Heroku gives AttributeError: 'module' object has no attribute 'ffi'
<p>I'm having a problem using bcrypt with my Flask application on Heroku. When I deploy to Heroku and go to the login route I get 500 Internal server error.  It works correctly locally.  How do I get the bcrypt package working on Heroku?</p>

<pre><code>ERROR in app: Exception on /login [POST]
Traceback (most recent call last):
  File "/app/.heroku/python/lib/python2.7/site-packages/flask/app.py", line 1639, in full_dispatch_request
    rv = self.dispatch_request()
  File "/app/.heroku/python/lib/python2.7/site-packages/flask/app.py", line 1625, in dispatch_request
    return self.view_functions[rule.endpoint](**req.view_args)
  File "/app/.heroku/python/lib/python2.7/site-packages/flask_restful/__init__.py", line 477, in wrapper
    resp = resource(*args, **kwargs)
  File "/app/.heroku/python/lib/python2.7/site-packages/flask/views.py", line 84, in view
    return self.dispatch_request(*args, **kwargs)
  File "/app/.heroku/python/lib/python2.7/site-packages/flask_restful/__init__.py", line 587, in dispatch_request
    resp = meth(*args, **kwargs)
  File "/app/app.py", line 196, in post
    elif bcrypt.check_password_hash(user.password, password):
  File "/app/.heroku/python/lib/python2.7/site-packages/flask_bcrypt.py", line 193, in check_password_hash
    return safe_str_cmp(bcrypt.hashpw(password, pw_hash), pw_hash)
  File "/app/.heroku/python/lib/python2.7/site-packages/bcrypt/__init__.py", line 82, in hashpw
    hashed = _bcrypt.ffi.new("char[]", 128)
AttributeError: 'module' object has no attribute 'ffi'
</code></pre>

<p>I encountered a similar issue. Here is a copy of the last part of my stack trace: </p>

<pre><code>  self.password = User.hashed_password(password) 
File "/app/application/models.py", line 16, in hashed_password 
File "/app/.heroku/python/lib/python3.5/site-packages/flask_bcrypt.py", line 163, in generate_password_hash 
File "/app/.heroku/python/lib/python3.5/site-packages/bcrypt/__init__.py", line 50, in gensalt 
  output = _bcrypt.ffi.new("unsigned char[]", 30) 
AttributeError: module 'bcrypt._bcrypt' has no attribute 'ffi' 
</code></pre>

<p>I'm wondering if this issue is particular to Heroku. I was using some existing Flask boilerplate. But this issue with Bcrypt has also happened to me in previous projects when using a (different) boilerplate Flask project on Heroku.</p>

<p><strong>Possible Solution 1</strong></p>

<p>Play around with different dependency combinations. In one case, the issue went away when I included <code>cryptography</code> in my <code>requirements.txt</code>. But as Jean Silva had mentioned in this thread, it is possible that dependencies could be in conflict. So you might want to play with different combinations until something works.</p>

<p><strong>Possible Solution 2</strong></p>

<p>If using Flask, try having the <code>werkzeug.security</code> package/module to hash / check hashes as opposed to using the <code>bcrypt</code> package directly. In example below in my <code>models.py</code>, commenting out such lines and adding new ones solved the issue for me.</p>

<pre><code># from index import db, bcrypt
from index import db
from werkzeug.security import generate_password_hash, check_password_hash


class User(db.Model):
    id = db.Column(db.Integer(), primary_key=True)
    email = db.Column(db.String(255), unique=True)
    password = db.Column(db.String(255))

    def __init__(self, email, password):
        self.email = email
        self.active = True
        self.password = User.hashed_password(password)

    @staticmethod
    def hashed_password(password):
        # return bcrypt.generate_password_hash(password)
        return generate_password_hash(password)

    @staticmethod
    def get_user_with_email_and_password(email, password):
        user = User.query.filter_by(email=email).first()
        # if user and bcrypt.check_password_hash(user.password, password):
        if user and check_password_hash(user.password, password):
            return user
        else:
            return None
</code></pre>

python heroku flask bcrypt