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Flask Simple Login - Login Extension for Flask

Project description

|Travis| |PyPI| |PyPI| |PyPI| |Flask|

Login Extension for Flask

There are good and recommended options to deal with web authentication &
authorization in Flask.

**I recommend you to use:**

- `Flask-Login <>`__
- `Flask-Security <>`__
- `Flask-Principal <>`__

Those extensions are really complete and **production ready**!

So why **Flask Simple Login**?

However sometimes you need something **simple** for that small project
or for prototyping.

Flask Simple Login

What it provides:

- Login and Logout forms and pages
- Function to check if user is logged-in
- Decorator for views
- Easy and customizable ``login_checker``
- Basic-Auth for API endpoints

What it does not provide:

- [STRIKEOUT:Database Integration]
- [STRIKEOUT:Password management]
- [STRIKEOUT:API authentication with Token or JWT]
- [STRIKEOUT:Role or user based access control]

of course you can easily implement all above by your own.

Hot it works

First install it from
`PyPI <>`__.

``pip install flask_simplelogin``

.. code:: python

from flask import Flask
from flask_simplelogin import SimpleLogin

app = Flask(__name__)

**That's it!**

Now you have ``/login`` and ``/logout`` routes in your application.

The username defaults to ``admin`` and the password defaults to
``secret`` (yeah that's not clever, let's see how to change it)

.. figure:: /login_screen.png
:alt: Login Screen

Login Screen


Simple way

.. code:: python

from flask import Flask
from flask_simplelogin import SimpleLogin

app = Flask(__name__)
app.config['SECRET_KEY'] = 'something-secret'
app.config['SIMPLELOGIN_USERNAME'] = 'chuck'
app.config['SIMPLELOGIN_PASSWORD'] = 'norris'


That works, but is not so clever, lets use env vars.

.. code:: bash


then ``SimpleLogin`` will read those env vars automatically.

.. code:: python

from flask import Flask
from flask_simplelogin import SimpleLogin

app = Flask(__name__)
app.config['SECRET_KEY'] = 'something-secret'

But what if you have more users and more complex auth logic? **write a
custom login checker**

Using a custom login checker

.. code:: python

from flask import Flask
from flask_simplelogin import SimpleLogin

app = Flask(__name__)
app.config['SECRET_KEY'] = 'something-secret'

def only_chuck_norris_can_login(user):
""":param user: dict {'username': 'foo', 'password': 'bar'}"""
if user.get('username') == 'chuck' and user.get('password') == 'norris':
return True # <--- Allowed
return False # <--- Denied

SimpleLogin(app, login_checker=only_chuck_norris_can_login)

Checking if user is logged in

.. code:: python

from flask_simplelogin import is_logged_in

if is_logged_in():
# do things if anyone is logged in

if is_logged_in('admin'):
# do things only if admin is logged in

Protecting your views

.. code:: python

from flask_simplelogin import login_required

@login_required # < --- simple decorator
def foo():
return 'secret'

@login_required(username='mary') # < --- accepts a list of names
def bar():
return "Mary's secret"

@app.route('/api', methods=['POST'])
@login_required(basic=True) # < --- Basic HTTP Auth for API
def api():
# curl -XPOST localhost:5000/api -H "Authorization: Basic Y2h1Y2s6bm9ycmlz" -H "Content-Type: application/json"
# Basic-Auth takes base64 encripted username:password
return jsonify(data='You are logged in with basic auth')

class ProtectedView(MethodView): # < --- Class Based Views
decorators = [login_required]
def get(self):
return "only loged in users can see this"

Protecting Flask Admin views

.. code:: python

from import ModelView
from flask_simplelogin import is_logged_in

class AdminView(ModelView)
def is_accessible(self):
return is_logged_in('admin')

Customizing templates

There are only one template to customize and it is called ``login.html``

Example is:

.. code:: html

{% extends 'base.html' %}
{% block title %}Login{% endblock %}
{% block messages %}
{%if form.errors %}
<ul class="alert alert-danger">
{% for field, errors in form.errors.items() %}
<li>{{field}} {% for error in errors %}{{ error }}{% endfor %}</li>
{% endfor %}
{% endif %}
{% endblock %}

{% block page_body %}
<form action="{{ url_for('simplelogin.login', next=request.args.get('next', '/')) }}" method="post">
<div class="form-group">
{{ form.csrf_token }}
{{form.username.label}}<div class="form-control">{{ form.username }}</div><br>
{{form.password.label}}<div class="form-control"> {{ form.password }}</div><br>
<input type="submit" value="Send">
{% endblock %}

Take a look at the `example
app <>`__.

And you can customize it in anyway you want and need, it receives a
``form`` in context and it is a ``WTF form`` the submit should be done
to ``request.path`` which is the same ``/login`` view.

You can also use ``{% if is_logged_in %}`` in your template if needed.

Custom validators

Pass ``must`` argument to ``login_required`` decorator, it can be a
``function`` or a list of ``functions`` if function returns ``None``
means **No** error and validator passed. if function returns an
``"Error message"`` means validator did not passed.

.. code:: python

def be_admin(username):
"""Validator to check if user has admin role"""
user_data = my_users.get(username)
if not user_data or 'admin' not in user_data.get('roles', []):
return "User does not have admin role"

def have_approval(username):
"""Validator: all users approved so return None"""

@login_required(must=[be_admin, have_approval])
def protected():
return render_template('secret.html')

Take a look at the `example
app <>`__.


- Flask-WTF and WTForms
- ``SECRET_KEY`` set in your ``app.config``


Do you need Access Control? you can easily mix ``flask_simplelogin`` with ``flask_allows``
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ ``pip install flask_allows``

.. code:: python

from flask import Flask, g
from flask_simplelogin import SimpleLogin
from flask_allows import Allows

app = Flask(__name__)
app.config['SECRET_KEY'] = 'something-secret'

def is_staff(ident, request):
return ident.permlevel == 'staff'

def only_chuck_norris_can_login(user):
if user.get('username') == 'chuck' and user.get('password') == 'norris':
# Bind the logged in user data to the `g` global object
g.user.username = user['username']
g.user.permlevel = 'staff' # set user permission level
return True # Allowed
return False # Denied

# init allows
allows = Allows(identity_loader=lambda: g.user)

# init SimpleLogin
SimpleLogin(app, login_checker=only_chuck_norris_can_login)

# a view which requires a logged in user to be member of the staff group
def a_view():
return "staff only can see this"

Need JSON Web Token (JWT)?

Take a look at
`Flask-JWT-Simple <>`__ and
of course you can mix SimpleLogin + JWT Simple

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