Pre-Deployment Checklist: Django Web Security

You already know web security is important to keeping hackers and cyber-thieves from accessing sensitive information. So, in this post we are going to check Django security vulnerabilities and how to fix them.

Deployment Checklist

First thing first, check your security vulnerabilities by following command:

manage.py check --deploy

You can see some descriptions which provide information about your Django web application vulnerabilities. Try to google these security issues and fix them before production.

The Mozilla Observatory

If you already deployed you application then use Observatory by Mozilla site to scan the security status of your site. The site also includes third-party scanners which test other security aspects of your site.

Here is the example of scan:

Cross site request forgery (CSRF) protection

In a web application, basically the webforms take input from the user and send them to server-side components to process them. The server-side components generally expose the service as a

POST

PUT

DELETE

methods for accepting the data over HTTP. Django has built-in security against most forms of CSRF threats, as long as you have allowed and used it if necessary.

As stated in the documentation, be very careful when marking views with the csrf_exempt decorator, unless it is absolutely necessary.

If someone has access (through an man-in-the-middle attack or xss) to your csrftoken cookie, then this is a vulnerability.

The CSRF protection cannot protect against man-in-the-middle attacks, so use HTTPS with HTTP Strict Transport Security (We will discuss it in post later).

Once you’ve set up HTTPS, add these lines in your settings.py:

CSRF_COOKIE_SECURE = True #to avoid transmitting the CSRF cookie over HTTP accidentally.
SESSION_COOKIE_SECURE = True #to avoid transmitting the session cookie over HTTP accidentally.

Cross-site Scripting (XSS)

A Cross-site Scripting (XSS) allows an attacker to inject a script into the content of a website or app. When a user visits the infected page the script will execute in the victim’s browser. This allows attackers to steal private information like cookies, account information, etc.

X-XSS-Protection: 1; mode=block enables XSS filtering. Rather than sanitizing the page, the browser will prevent rendering of the page if an attack is detected.

To enable it in Django, make sure django.middleware.security.SecurityMiddleware is present in middleware's list and add following lines in your settings.py:

SECURE_BROWSER_XSS_FILTER = True
SECURE_CONTENT_TYPE_NOSNIFF = True

Django Admin Security

One of the most important thing is to make Django administration secure. Before you deploy your application you must change admin/ path to something only you know. Otherwise, someone can easily type /admin in url and access to adminsitrator login page.

#urls.py

from django.contrib import admin
from django.urls import path

urlpatterns = [
    path('admin/', admin.site.urls) # change admin something different

You can create fake admin login page using django-admin-honeypot and it will notify you if someone try attempt unauthorized access.

SSL Redirect

Add following line to your settings.py to force Django redirect all non-HTTPS requests to HTTPS.

SECURE_SSL_REDIRECT = True

Content Security Policy (CSP)

If your Django application is large, contains a lot of third-party code, and has a lot of inline scripts and styles scattered all over the project, then you should add CSP to your site.

For more information about CSP visit An Introduction to Content Security Policy

Django does not have a built-in method for creating a CSP header, so you can install Mozilla’s django-csp module and use your browser's console to track the security violations in your code.

Once you installed django-csp, add following lines to your settings.py.

# Content Security Policy
CSP_DEFAULT_SRC = ("'none'", )
CSP_STYLE_SRC = ("'self'", )
CSP_SCRIPT_SRC = ("'self'", )
CSP_IMG_SRC = ("'self'", )
CSP_FONT_SRC = ("'self'", )

So, basically, your all inline scripts and styles will not be allowed anymore. All scripts and styles must be loaded from a resource. You can add ‘unsafe-inline’ to your script and style CSP headers, however, it negates the whole policy.

Its really important to clean your code from all these inline styles and scripts. However, some external resources such as Google Tag Manager or Google Analytics should be allowed in your CSP policy. To achieve that update your code like this:

#Content Security Policy
CSP_DEFAULT_SRC = ("'none'", )
CSP_STYLE_SRC = ("'self'", "fonts.googleapis.com", "'sha256-/3kWSXHts8LrwfemLzY9W0tOv5I4eLIhrf0pT8cU0WI='")
CSP_SCRIPT_SRC = ("'self'", "ajax.googleapis.com", "www.googletagmanager.com", "www.google-analytics.com")
CSP_IMG_SRC = ("'self'", "data:", "www.googletagmanager.com", "www.google-analytics.com")
CSP_FONT_SRC = ("'self'", "fonts.gstatic.com")
CSP_CONNECT_SRC = ("'self'", )
CSP_OBJECT_SRC = ("'none'", )
CSP_BASE_URI = ("'none'", )
CSP_FRAME_ANCESTORS = ("'none'", )
CSP_FORM_ACTION = ("'self'", )
CSP_INCLUDE_NONCE_IN = ('script-src',)

Fore more information take a look django-csp documentation.

Note that this configuration depends on which external resources you are using so please first read the documentation and then apply changes to your site.

HTTP Strict Transport Security

When this policy is set, browsers will refuse to connect to your site for the given time period if you’re not properly serving HTTPS resources, or if your certificate expires.

Add the following lines to your settings.py:

SECURE_HSTS_SECONDS = 86400  # 1 day
SECURE_HSTS_INCLUDE_SUBDOMAINS = True
SECURE_HSTS_PRELOAD = True

Extra Security Tools from Nikita Sobolev

Use django-axes or similar to block brute-force requests
Use Feature-Policy header to switch on only things you really need in user's browser
Use Referrer-Policy header to prevent sensitive information from leaking into other resources
Use safety to make sure your dependencies are secure and do not contain any known vulnerabilitiesUse wemake-python-styleguide to check for your source code to be secure

I recommend to use wemake-django-template. It is a new project boilerplate focused on security and code quality. It has everything from the list. And even several more advanced features!

Mission Accomplished!

Now your app is almost secure. Additionally you can scan your open ports by using nmap and try to google how to fix these open ports.

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