Permissions

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

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='john@test.com',
    password='password',
)
user2 = User.objects.create_user(
    username='alice',
    email='alice@test.com',
    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
)

# Grant the `permission.add_article` permission for user1.
# Use the `perm_to_permission` utility to convert the permission-string to a `Permission` object instance.
from permission.utils.permissions import perm_to_permission
user1.user_permissions.add(perm_to_permission('permission.add_article'))

# `add_article` is granted by user permissions
assert user1.has_perm('permission.add_article') == True
assert user2.has_perm('permission.add_article') == False

# `change_article` is not granted by user permissions
assert user1.has_perm('permission.change_article') == False
assert user2.has_perm('permission.change_article') == False

# `change_article` is granted by `AuthorPermissionLogic`
assert user1.has_perm('permission.change_article', art1) == True
# `change_article` is not granted by `AuthorPermissionLogic`
assert user1.has_perm('permission.change_article', art2) == False

# `delete_article` is not granted by user permissions
assert user1.has_perm('permission.delete_article') == False
assert user2.has_perm('permission.delete_article') == False

# `delete_article` is granted by `AuthorPermissionLogic`
assert user1.has_perm('permission.delete_article', art1) == True
# `delete_article` is not granted by `AuthorPermissionLogic`
assert user1.has_perm('permission.delete_article', art2) == False

# `delete_article` is not granted by `AuthorPermissionLogic`
assert user2.has_perm('permission.delete_article', art1) == False
# `delete_article` is granted by `AuthorPermissionLogic`
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 permission.logics.author.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

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='john@test.com',
    password='password',
)
user2 = User.objects.create_user(
    username='alice',
    email='alice@test.com',
    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 permission.logics.collaborators.CollaboratorsPermissionLogic to learn how this logic works.

There are permission.logics.staff.StaffPermissionLogic and permission.logics.groupinGroupInPermissionLogic 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.base.PermissionLogic and must override has_perm(user_obj, perm, obj=None) method which return boolean value.