django-permission

Author: Alisue <[email protected]>
Supported python versions: Python 2.6, 2.7, 3.2, 3.3, 3.4
Supported django versions: Django 1.2 - 1.6 and 1.7 rc1

An enhanced permission library which enables a logic-based permission system to handle complex permissions in Django.

It is developed based on the authentication backend system introduced in Django 1.2. This library does support Django 1.2 and higher.

Documentation

http://django-permission.readthedocs.org/en/latest/

Installation

Use pip like:

$ pip install django-permission

Usage

Configuration

Add permission to the INSTALLED_APPS in your settings module

INSTALLED_APPS = (
    # ...
    'permission',
)

Add our extra authorization/authentication backend

AUTHENTICATION_BACKENDS = (
    'django.contrib.auth.backends.ModelBackend', # default
    'permission.backends.PermissionBackend',
)

Follow the instructions below to apply logical permissions to django models

Autodiscovery

This is a new feature, added in django-permission 0.6.0, and the behavior was changed in django-permission 0.6.3. Like django's admin package, django-permission automatically discovers the perms.py in your application directory by running ``permission.autodiscover()``. Additionally, if the perms.py module has a PERMISSION_LOGICS variable, django-permission automatically run the following functions to apply the permission logics.

for model, permission_logic_instance in PERMISSION_LOGICS:
    if isinstance(model, str):
        model = get_model(*model.split(".", 1))
    add_permission_logic(model, permission_logic_instance)

Quick tutorial

Add import permission; permission.autodiscover() to your urls.py like:

from django.conf.urls import patterns, include, url
from django.contrib import admin

admin.autodiscover()
# add this line
import permission; permission.autodiscover()

urlpatterns = patterns('',
    url(r'^admin/', include(admin.site.urls)),
    # ...
)

Write perms.py in your application directory like:

from permission.logics import AuthorPermissionLogic
from permission.logics import CollaboratorsPermissionLogic

PERMISSION_LOGICS = (
    ('your_app.Article', AuthorPermissionLogic()),
    ('your_app.Article', CollaboratorsPermissionLogic()),
)

You can specify a different module or variable name, with PERMISSION_AUTODISCOVER_MODULE_NAME or PERMISSION_AUTODISCOVER_VARIABLE_NAME respectively.

Apply permission logic

Let's assume you wrote an article model which has an author attribute to store the creator of the article, and you want to give that author full control permissions (e.g. add, change and delete permissions).

What you need to do is just applying permission.logics.AuthorPermissionLogic to the Article model like

from django.db import models
from django.contrib.auth.models import User


class Article(models.Model):
    title = models.CharField('title', max_length=120)
    body = models.TextField('body')
    author = models.ForeignKey(User)

    # this is just required for easy explanation
    class Meta:
        app_label='permission'

# apply AuthorPermissionLogic
from permission import add_permission_logic
from permission.logics import AuthorPermissionLogic
add_permission_logic(Article, AuthorPermissionLogic())

Note

From django-permission version 0.8.0, you can specify related object with field__name attribute like django queryset lookup. See the working example below:

from django.db import models
from django.contrib.auth.models import User


class Article(models.Model):
    title = models.CharField('title', max_length=120)
    body = models.TextField('body')
    project = models.ForeignKey('permission.Project')

    # this is just required for easy explanation
    class Meta:
        app_label='permission'

class Project(models.Model):
    title = models.CharField('title', max_length=120)
    body = models.TextField('body')
    author = models.ForeignKey(User)

    # this is just required for easy explanation
    class Meta:
        app_label='permission'

# apply AuthorPermissionLogic to Article
from permission import add_permission_logic
from permission.logics import AuthorPermissionLogic
add_permission_logic(Article, AuthorPermissionLogic(
    field_name='project__author',
))

That's it. Now the following codes will work as expected

user1 = User.objects.create_user(
    username='john',
    email='[email protected]',
    password='password',
)
user2 = User.objects.create_user(
    username='alice',
    email='[email protected]',
    password='password',
)

art1 = Article.objects.create(
    title="Article 1",
    body="foobar hogehoge",
    author=user1
)
art2 = Article.objects.create(
    title="Article 2",
    body="foobar hogehoge",
    author=user2
)

# You have to apply 'permission.add_article' to users manually because it
# is not an object permission.
from permission.utils.permissions import perm_to_permission
user1.user_permissions.add(perm_to_permission('permission.add_article'))

assert user1.has_perm('permission.add_article') == True
assert user1.has_perm('permission.change_article') == False
assert user1.has_perm('permission.change_article', art1) == True
assert user1.has_perm('permission.change_article', art2) == False

assert user2.has_perm('permission.add_article') == False
assert user2.has_perm('permission.delete_article') == False
assert user2.has_perm('permission.delete_article', art1) == False
assert user2.has_perm('permission.delete_article', art2) == True

#
# You may also be interested in django signals to apply 'add' permissions to the
# newly created users.
# https://docs.djangoproject.com/en/dev/ref/signals/#django.db.models.signals.post_save
#
from django.db.models.signals.post_save
from django.dispatch import receiver
from permission.utils.permissions import perm_to_permission

@receiver(post_save, sender=User)
def apply_permissions_to_new_user(sender, instance, created, **kwargs):
    if not created:
        return
    #
    # permissions you want to apply to the newly created user
    # YOU SHOULD NOT APPLY PERMISSIONS EXCEPT PERMISSIONS FOR 'ADD'
    # in this way, the applied permissions are not object permission so
    # if you apply 'permission.change_article' then the user can change
    # any article object.
    #
    permissions = [
        'permission.add_article',
    ]
    for permission in permissions:
        # apply permission
        # perm_to_permission is a utility to convert string permission
        # to permission instance.
        instance.user_permissions.add(perm_to_permission(permission))

See http://django-permission.readthedocs.org/en/latest/_modules/permission/logics/author.html#AuthorPermissionLogic to learn how this logic works.

Now, assume you add collaborators attribute to store collaborators of the article and you want to give them a change permission.

What you need to do is quite simple. Apply permission.logics.CollaboratorsPermissionLogic to the Article model as follows

from django.db import models
from django.contrib.auth.models import User


class Article(models.Model):
    title = models.CharField('title', max_length=120)
    body = models.TextField('body')
    author = models.ForeignKey(User)
    collaborators = models.ManyToManyField(User)

    # this is just required for easy explanation
    class Meta:
        app_label='permission'

# apply AuthorPermissionLogic and CollaboratorsPermissionLogic
from permission import add_permission_logic
from permission.logics import AuthorPermissionLogic
from permission.logics import CollaboratorsPermissionLogic
add_permission_logic(Article, AuthorPermissionLogic())
add_permission_logic(Article, CollaboratorsPermissionLogic(
    field_name='collaborators',
    any_permission=False,
    change_permission=True,
    delete_permission=False,
))

Note

From django-permission version 0.8.0, you can specify related object with field_name attribute like django queryset lookup. See the working example below:

from django.db import models
from django.contrib.auth.models import User


class Article(models.Model):
    title = models.CharField('title', max_length=120)
    body = models.TextField('body')
    project = models.ForeignKey('permission.Project')

    # this is just required for easy explanation
    class Meta:
        app_label='permission'

class Project(models.Model):
    title = models.CharField('title', max_length=120)
    body = models.TextField('body')
    collaborators = models.ManyToManyField(User)

    # this is just required for easy explanation
    class Meta:
        app_label='permission'

# apply AuthorPermissionLogic to Article
from permission import add_permission_logic
from permission.logics import CollaboratorsPermissionLogic
add_permission_logic(Article, CollaboratorsPermissionLogic(
    field_name='project__collaborators',
))

That's it. Now the following codes will work as expected

user1 = User.objects.create_user(
    username='john',
    email='[email protected]',
    password='password',
)
user2 = User.objects.create_user(
    username='alice',
    email='[email protected]',
    password='password',
)

art1 = Article.objects.create(
    title="Article 1",
    body="foobar hogehoge",
    author=user1
)
art1.collaborators.add(user2)

assert user1.has_perm('permission.change_article') == False
assert user1.has_perm('permission.change_article', art1) == True
assert user1.has_perm('permission.delete_article', art1) == True

assert user2.has_perm('permission.change_article') == False
assert user2.has_perm('permission.change_article', art1) == True
assert user2.has_perm('permission.delete_article', art1) == False

See http://django-permission.readthedocs.org/en/latest/_modules/permission/logics/collaborators.html#CollaboratorsPermissionLogic to learn how this logic works.

There are StaffPermissionLogic and GroupInPermissionLogic for is_staff` or ``group based permission logic as well.

Customize permission logic

Your own permission logic class must be a subclass of permission.logics.PermissionLogic and must override has_perm(user_obj, perm, obj=None) method which return boolean value.

Class, method, or function decorator

Like Django's permission_required but it can be used for object permissions and as a class, method, or function decorator. Also, you don't need to specify a object to this decorator for object permission. This decorator automatically determined the object from request (so you cannnot use this decorator for non view class/method/function but you anyway use user.has_perm in that case).

>>> from permission.decorators import permission_required
>>> # As class decorator
>>> @permission_required('auth.change_user')
>>> class UpdateAuthUserView(UpdateView):
...     pass
>>> # As method decorator
>>> class UpdateAuthUserView(UpdateView):
...     @permission_required('auth.change_user')
...     def dispatch(self, request, *args, **kwargs):
...         pass
>>> # As function decorator
>>> @permission_required('auth.change_user')
>>> def update_auth_user(request, *args, **kwargs):
...     pass

Override the builtin `if` template tag

django-permission overrides the builtin if tag, adding two operators to handle permissions in templates. You can write a permission test by using has keyword, and a target object with of as below.

{% if user has 'blogs.add_article' %}
    <p>This user have 'blogs.add_article' permission</p>
{% elif user has 'blog.change_article' of object %}
    <p>This user have 'blogs.change_article' permission of {{object}}</p>
{% endif %}

{# If you set 'PERMISSION_REPLACE_BUILTIN_IF = False' in settings #}
{% permission user has 'blogs.add_article' %}
    <p>This user have 'blogs.add_article' permission</p>
{% elpermission user has 'blog.change_article' of object %}
    <p>This user have 'blogs.change_article' permission of {{object}}</p>
{% endpermission %}

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