flask-security encrypt_password('mypassword') varies every time when i reload the page

Question

I've already configured SECURITY_PASSWORD_SALT and use "bcrypt". But every time i reload the page print encrypt_password('mypassword') will print different values, so i can't verify user input password via verify_password(form.password.data, user.password).

But I can login from flask-security built-in login view

Here is code to demonstrate the strange behavior of encrypt_password:

from flask import Flask, render_template
from flask.ext.sqlalchemy import SQLAlchemy
from flask.ext.security import Security, SQLAlchemyUserDatastore, \
    UserMixin, RoleMixin, login_required
from flask.ext.security.utils import encrypt_password, verify_password

# Create app
app = Flask(__name__)
app.config['DEBUG'] = True
app.config['SECRET_KEY'] = 'super-secret'
app.config['SQLALCHEMY_DATABASE_URI'] = 'sqlite://'

app.config['SECURITY_PASSWORD_HASH'] = 'sha512_crypt'
app.config['SECURITY_PASSWORD_SALT'] = 'fhasdgihwntlgy8f'

# Create database connection object
db = SQLAlchemy(app)

# Define models
roles_users = db.Table('roles_users',
        db.Column('user_id', db.Integer(), db.ForeignKey('user.id')),
        db.Column('role_id', db.Integer(), db.ForeignKey('role.id')))

class Role(db.Model, RoleMixin):
    id = db.Column(db.Integer(), primary_key=True)
    name = db.Column(db.String(80), unique=True)
    description = db.Column(db.String(255))

class User(db.Model, UserMixin):
    id = db.Column(db.Integer, primary_key=True)
    email = db.Column(db.String(255), unique=True)
    password = db.Column(db.String(255))
    active = db.Column(db.Boolean())
    confirmed_at = db.Column(db.DateTime())
    roles = db.relationship('Role', secondary=roles_users,
                            backref=db.backref('users', lazy='dynamic'))

# Setup Flask-Security
user_datastore = SQLAlchemyUserDatastore(db, User, Role)
security = Security(app, user_datastore)

# Create a user to test with
@app.before_first_request
def create_user():
    db.create_all()
    user_datastore.create_user(email='matt@nobien.net', password='password')
    db.session.commit()

# Views
@app.route('/')
#@login_required
def home():
    password = encrypt_password('mypassword')
    print verify_password('mypassword', password)
    return password
#    return render_template('index.html')

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

Answer 1

The fact that encrypt_password() generates a new value is by design. The fact that verify_password() fails is not. It's an already reported bug in Flask-Security.

When you use the login view, a different method, verify_and_update_password() is used instead, which doesn't suffer from the same problem.

The fix is not yet part of a new release. You can fix this issue yourself by applying the change from PR #223; it replaces the verify_password() function in the flask_security/utils.py file with:

def verify_password(password, password_hash):
    """Returns ``True`` if the password matches the supplied hash.

    :param password: A plaintext password to verify
    :param password_hash: The expected hash value of the password (usually form your database)
    """
    if _security.password_hash != 'plaintext':
        password = get_hmac(password)

    return _pwd_context.verify(password, password_hash)

e.g. first hash the password with HMAC+SHA512 before verifying it against the hash, just as the original encrypt_password() does, and not apply encrypt_password() as the current released version does.