9. Using authentication

9.1. Overview

Google App Engine has a very nice default auth mechanism using google account or google apps account. You can use this capability with extensible manner with AuthenticationMiddleware and kay.auth.backend.GoogleBackend. You can also use username and password information stored in the app engine datastore.

9.2. Helper functions and decorators

There are helper functions in kay.utils module: create_logout_url and create_login_url. These functions are automatically imported into templates’ rendering context. So you can use these functions in your templates just like:

{% if request.user.is_anonymous() %}
  <a href="{{ create_login_url() }}">login</a>
{% else %}
  Hello {{ request.user }}! <a href="{{ create_logout_url() }}">logout</a>
{% endif %}

There are decorators in kay.auth.decorators module: login_required and admin_required. You can decorate any view of yours with these decorators just like:

@login_required
def user_profile(request):
  """ This is a view for detailed information of the user's profile.
  """
  ...
  ...

@admin_required
def manage_users(request):
  """ This is a view for user management.
  """
  ...
  ...

9.3. Using google account authentication

By default, kay.auth.middleware.AuthenticationMiddleware is enabled, and settings.AUTH_USER_BACKEND is set to kay.auth.backend.GoogleBackend. This backend is for authentication using google account or google apps account. If a user logs into your app first time, an information of the user is stored as kay.auth.models.GoogleUser entity (It’s just a default setting, it is also customizable) in the GAE datastore. You can use this middleware and backend combination without using session capability.

To customize user model, you need to define new class extended from kay.auth.models.GoogleUser, add any required properties to it, and set the name of your new class to settings.AUTH_USER_MODEL.

MIDDLEWARE_CLASSES = (
  'kay.auth.middleware.AuthenticationMiddleware',
)
AUTH_USER_BACKEND = 'kay.auth.backend.GoogleBackend'
AUTH_USER_MODEL = 'kay.auth.models.GoogleUser'

9.4. Using datastore authentication

To use this middleware, you need to set kay.auth.middleware.AuthenticationMiddleware to settings.MIDDLEWARE_CLASSES, and also need to set kay.auth.models.DatastoreUser (or a classname that is extended from it) to settings.AUTH_USER_MODEL and kay.auth.backend.DatastoreBackend to settings.AUTH_USER_BACKEND. AuthenticationMiddleware must be placed under SessionMiddleware that is mandatry for this middleware. You also need to add kay.auth to settings.INSTALLED_APPS.

INSTALLED_APPS = (
  'kay.auth',
)
MIDDLEWARE_CLASSES = (
  'kay.sessions.middleware.SessionMiddleware',
  'kay.auth.middleware.AuthenticationMiddleware',
)
AUTH_USER_BACKEND = 'kay.auth.backend.DatastoreBackend'
AUTH_USER_MODEL = 'kay.auth.models.DatastoreUser'

9.5. Creating a new user

kay.auth.create_new_user is a function for creating new user. If there is a user with the same user_name, this function raises kay.auth.DuplicateKeyError. If succeeded, it returns a newly created user object.

from kay.auth import create_new_user
user_name = 'hoge'
password = 'hoge'
new_user = create_new_user(user_name, password, is_admin=is_admin)

You can also use manage.py create_user command like following:

$ python manage.py create_user hoge

This commands will ask you a new password for this user.

9.6. Using datastore authentication on an owned domain

TODO