User Permissions in Django

User Objects

In Django, user objects are the core of the authentication system and represent the people interacting with the site. They are used to enable features such as restricting access, registering user profiles, and associating content with creators. By default, Django comes with a built-in user model that is defined in the django.contrib.auth.models module. This model includes fields for storing basic user information, such as a username, password, email address, and first and last names.

Creating Users

The `create_user() helper function is a built-in function provided by Django's authentication framework that makes it easy to create new user objects. This function takes several arguments, including a required username, email, and password argument, and an optional first_name and last_name argument.

Creating Superusers

The createsuperuser command is a management command that is included with Django, a popular web framework for building web applications using the Python programming language. It is used to create a new superuser, which is a user account with administrative privileges.

You will be prompted to enter a username, email address, and password for the new superuser account. Once you have entered this information, the command will create the new superuser and add them to the database.

Please note that the command creates only one superuser at a time. If you want to create multiple superusers, you will need to run the command multiple times.

Changing Passwords

In Django, you can use the change password management command to change the password for a specific user. This command is included with Django, and it can be run from the command line to change a user's password. To use the command, navigate to the root directory of your Django project in the command line and enter the following command:

Authenticating Users

Django includes built-in authentication views and forms that make it easy to handle user authentication in a web application. The authentication process in Django involves checking a user's credentials (such as their username and password) against the information stored in the database. Django's authentication views and forms are located in the django.contrib.auth package. The most commonly used views for authentication are the login, logout, and password_change views.

Permissions and Authorization

Permissions and authorization are important aspects of user management in Django. Permissions are used to control access to specific resources or actions within an application, and authorization is the process of checking whether a user has the necessary permissions to access a resource or perform an action. The ModelAdmin class in Django provides methods for setting permissions on a per-object basis, in addition to the default permissions set on the model as a whole. By overriding these methods in a custom ModelAdmin class, you can specify custom logic for determining whether a user has permission to view, add, change, or delete a specific object instance. This allows for fine-grained control over permissions and can be useful in situations where the standard model-level permissions are not sufficient.

Default permissions

When django.contrib.auth is included in the INSTALLED_APPS setting, it automatically creates four default permissions for each model defined in your installed applications:

• add: Allows a user to create new instances of a model.
• change: Allows a user to update existing instances of a model.
• delete: Allows a user to delete existing instances of a model.
• view: Allows a user to view existing instances of a model.

These permissions are created when you run the command "python manage.py makemigrations" and are stored in the database. These permissions can be assigned to a user or group via Django's built-in admin interface or programmatically.

Groups

The Group model provided by django.contrib.auth is a way to organize users into groups and assign permissions or other labels to those groups. Each group can have any number of users associated with it, and a user can belong to multiple groups. When a user is added to a group, they automatically inherit the permissions that have been granted to that group. This is one of the key features of the Group model and allows you to easily manage permissions for multiple users at once. For example, if you have a group named "blog editors" and you have granted the permission "can_edit_blog_page" to that group, any user that belongs to that group will have the ability to edit the blog page.

Programmatically Creating Permissions

In addition to creating custom permissions within a model's Meta class, you can also create permissions directly using the Permission model provided by Django's auth app. For example, you can create the can_edit permission for a BlogPost model in firstapp:

In the above code get_for_model() method is used to retrieve the ContentType object for the BlogPost model. Then we create a new Permission object using the create() method, passing in the following arguments:

• codename: A unique string identifier for the permission, used internally by Django.
• name: A human-readable name for the permission, which will be displayed in the Django admin interface.
• content_type: The ContentType object for the model the permission applies to. Once the permission is created, you can assign it to a user or group using the user_permissions or permissions attribute of the User or Group model respectively.

Permission Caching

Django includes a built-in caching mechanism for permissions, which can improve the performance of your application by reducing the number of database queries required to check a user's permissions. When a user's permissions are first checked, they are cached in the user's session. Subsequent permission checks for the same user will use the cached permissions, rather than querying the database again. This can greatly improve the performance of your application, especially if you have a large number of users or a large number of permission checks being performed.

Proxy Models

Proxy models in Django are used to create a new model that shares the same database table as an existing model (referred to as the "concrete" model), but with potentially different behavior or options. When creating permissions for proxy models, Django uses the content type of the proxy model itself rather than the content type of the concrete model it subclasses. It can be used to add or override methods or fields of the parent model, without changing the original model or its data. To create a proxy model, use the django.db.models.base.Model class and set the Meta.proxy attribute to True.

Authentication in Web Requests

Django provides built-in authentication views and forms that can handle authentication for web requests. Django uses sessions and middleware to handle authentication in web requests. The django.contrib.sessions.middleware.SessionMiddleware is responsible for handling sessions in Django. This middleware adds a session object to each request, which can be used to store and retrieve data specific to a particular user. This middleware populates the request object with a user attribute, which represents the current user. If the user is logged in, the user attribute is set to an instance of the User model, otherwise, it is set to an instance of the AnonymousUser class. This middleware ensures that the user remains logged in as long as their session is active, even if they close their browser or leave the website. For example, we can use is_authenticated for the authentication of a user:

How to log a user in

There are several ways to log a user in Django. One way is to use the django.contrib.auth.login() function. This function takes a request object and a user object as its arguments and sets the user as the current user for the session. The user object should be an instance of the User model or a custom user model.

How to log a user out

In Django, you can log a user out by using the logout() function from the Django. contrib.auth module. Here is an example of how to use this function in a view:

• The logout_view function is a view that handles the logout process.
• The logout() function is called with the request object as its argument.
• This function performs the necessary steps to log the user out, such as clearing the user's session and cookies.
• The redirect() function is used to redirect the user to the home page after they have been logged out.

Limiting access to logged-in users

There are many ways to limit access to logged-in users one of the wat is to limit access to certain views or pages to only logged-in users is to check the request.user.is_authenticated attribute in the view function and redirecting the user to the login page if they are not authenticated. Here's an example of how you can do this:

You can also limit access to certain views or pages to only logged-in users by using the user_passes_test() or user_passes_test() decorators from the django.contrib.auth.decorators module. Here's an example of how you can use the user_passes_test() decorator to make sure the user has an email in the desired domain and if not, redirects to the login page::

Redirecting unauthorized requests in class-based views

In Django, there is a built-in class called AccessMixin that you can use to limit access to certain views or pages to only logged-in users. This class is located in the django.contrib.auth.mixins module.The AccessMixin class provides an easy way to handle access restrictions in class-based views. It can be used to configure the behavior of a view when access is denied. The AccessMixin class has an attribute called raise_exception which can be set to True or False. If raise_exception is set to True, then an HttpResponseForbidden will be returned to the user when they try to access a view they do not have permission to. If raise_exception is set to False, then the user will be redirected to the login page.

Authentication Views

Django includes several built-in views for handling user authentication, including login, logout, and password management views. These views are located in the django.contrib.auth.views module and can be easily included in your Django project's URL configuration. One of the easiest ways to include the built-in authentication views in your Django project is to include the provided URLconf in django.contrib.auth.urls in your own URLconf. This is done by using the include() function in your urls.py file, like so:

This above url include the following URL patterns:

Helper functions

In Django, helper functions are small, reusable pieces of code that perform specific tasks and can be called from various parts of your application. They are typically stored in a separate file and imported into the views or models where they are needed. redirect_to_login() is a function in Django's built-in django. contrib.auth module that allows you to redirect a user to the login page and then redirect them back to the original page after a successful login.

Built-in forms

Django provides several built-in forms that can be used for handling user input and validation, such as:

• AuthenticationForm: This form is used for handling user login. It includes fields for username and password, and it validates that the provided credentials are correct.
• UserCreationForm: This form is used for creating new user accounts. It includes fields for username, email, password1, and password2, and it validates that the provided data is in the correct format and that the passwords match.
• PasswordChangeForm: This form is used for handling password change requests. It includes fields for the old password, new password1, and new password2 and it validates that the provided data is in the correct format and that the new passwords match.
• PasswordResetForm: This form is used for handling password reset requests. It includes a field for email and it validates that the provided email is associated with an existing user account.

Authentication data in templates

In Django, the user's authentication status and other relevant data can be accessed in templates using the built-in user variable. The user variable is an instance of the django.contrib.auth.models.User class, and it is automatically available in all templates. You can use the user variable to check if a user is authenticated and display different content based on their authentication status. For example:

Managing users in the admin

The Django admin interface provides a convenient way to manage users, groups, and permissions when both django.contrib.admin and django.contrib.auth is installed. You can easily create, edit, and delete users, assign them to groups, and assign permissions to users or groups. The admin interface also keeps a log of user actions and changes made to models within the admin, making it easy to track changes and revert them if needed. It's a powerful tool for managing users and permissions, but it's important to remember to only grant access to authorized users.

Creating users

In Django, the built-in admin interface allows you to manage users easily. To create a new user, go to the admin page and navigate to the "Users" section. Once there, you can click on the "Add User" button to create a new user. You can also edit or delete existing users by clicking on the corresponding buttons. You can customize the user model by creating a custom user model and then registering it in the admin.py file. You can also use the UserAdmin class to customize the fields that are displayed in the admin interface and to add custom actions that can be performed on users.

Changing passwords

Changing passwords is an important aspect of maintaining the security of your accounts. In Django, User passwords are not displayed (or kept in the database) in the admin. You can change the password of the user via the command line by using python manage.py changepassword username command.