# Authentication

The `Authentication` class provides a means of authenticating users of the site. It is designed to work out-of-the-box with a simple `User` model, but can be heavily customized.

The `Auth` system is comprised of a single class which is responsible for coordinating incoming requests to your project with known users. It provides the following:

- views for login and logout

- model to store user data (or you can provide your own)

- mechanism for identifying users across requests (uses session storage)

All of these pieces can be customized, but the default out-of-box implementation aims to provide a good starting place.

The auth system is also designed to work closely with the Admin Interface.

## Getting started

In order to provide a method for users to authenticate with your site, instantiate an `Auth` backend for your project:

    from flask import Flask

    from flask_peewee.auth import Auth
    from flask_peewee.db import Database

    app = Flask(__name__)
    db = Database(app)

    # needed for authentication
    auth = Auth(app, db)

Note

`user` is reserverd keyword in Postgres. Pass db_table to Auth to override db table.

## Marking areas of the site as login required

If you want to mark specific areas of your site as requiring auth, you can decorate views using the `Auth.login_required()` decorator:

    @app.route('/private/')
    @auth.login_required
    def private_timeline():
        user = auth.get_logged_in_user()

        # ... display the private timeline for the logged-in user

If the request comes from someone who has not logged-in with the site, they are redirected to the `Auth.login()` view, which allows the user to authenticate. After successfully logging-in, they will be redirected to the page they requested initially.

## Retrieving the current user

Whenever in a request context, the currently logged-in user is available by calling `Auth.get_logged_in_user()`, which will return `None` if the requesting user is not logged in.

The auth system also registers a pre-request hook that stores the currently logged-in user in the special flask variable `g`.

## Accessing the user in the templates

The auth system registers a template context processor which makes the logged-in user available in any template:

    {% if user %}
      <p>Hello {{ user.username }}</p>
    {% else %}
      <p>Please <a href="{{ url_for('auth.login') }}?next={{ request.path }}">log in</a></p>
    {% endif %}

## Using a custom “User” model

It is easy to use your own model for the `User`, though depending on the amount of changes it may be necessary to override methods in both the `Auth` and `Admin` classes.

Unless you want to override the default behavior of the `Auth` class’ mechanism for actually authenticating users (which you may want to do if relying on a 3rd-party for auth) – you will want to be sure your `User` model implements two methods:

- `set_password(password)` – takes a raw password and stores an encrypted version on model

- `check_password(password)` – returns whether or not the supplied password matches the one stored on the model instance

Note

The `BaseUser` mixin provides default implementations of these two methods.

Here’s a simple example of extending the auth system to use a custom user model:

    from flask_peewee.auth import BaseUser # <-- implements set_password and check_password

    app = Flask(__name__)
    db = Database(app)

    # create our custom user model. note that we're mixing in BaseUser in order to
    # use the default auth methods it implements, "set_password" and "check_password"
    class User(db.Model, BaseUser):
        username = CharField()
        password = CharField()
        email = CharField()

        # ... our custom fields ...
        is_superuser = BooleanField()

    # create a modeladmin for it
    class UserAdmin(ModelAdmin):
        columns = ('username', 'email', 'is_superuser',)

        # Make sure the user's password is hashed, after it's been changed in
        # the admin interface. If we don't do this, the password will be saved
        # in clear text inside the database and login will be impossible.
        def save_model(self, instance, form, adding=False):
            orig_password = instance.password

            user = super(UserAdmin, self).save_model(instance, form, adding)

            if orig_password != form.password.data:
                user.set_password(form.password.data)
                user.save()

            return user

    # subclass Auth so we can return our custom classes
    class CustomAuth(Auth):
        def get_user_model(self):
            return User

        def get_model_admin(self):
            return UserAdmin

    # instantiate the auth
    auth = CustomAuth(app, db)

Here’s how you might integrate the custom auth with the admin area of your site:

    # subclass Admin to check for whether the user is a superuser
    class CustomAdmin(Admin):
        def check_user_permission(self, user):
            return user.is_superuser

    # instantiate the admin
    admin = CustomAdmin(app, auth)

    admin.register(User, UserAdmin)
    admin.setup()