The djangosecure.middleware.SecurityMiddleware performs six different tasks for you. Each one can be independently enabled or disabled with a setting.
Django 1.4+ provides its own middleware and setting to set the X-Frame-Options header; you can use either this or Django’s, there’s no value in using both.
Clickjacking attacks use layered frames to mislead users into clicking on a different link from the one they think they are clicking on. Fortunately, newer browsers support an X-Frame-Options header that allows you to limit or prevent the display of your pages within a frame. Valid options are “DENY” or “SAMEORIGIN” - the former prevents all framing of your site, and the latter allows only sites within the same domain to frame.
Unless you have a need for frames, your best bet is to set “X-Frame-Options: DENY” – and this is what SecurityMiddleware will do for all responses, if the SECURE_FRAME_DENY setting is True.
If you have a few pages that should be frame-able, you can set the “X-Frame-Options” header on the response to “SAMEORIGIN” in the view; SecurityMiddleware will not override an already-present “X-Frame-Options” header. If you don’t want the “X-Frame-Options” header on this view’s response at all, decorate the view with the frame_deny_exempt decorator:
from djangosecure.decorators import frame_deny_exempt @frame_deny_exempt def my_view(request): # ...
For sites that should only be accessed over HTTPS, you can instruct newer browsers to refuse to connect to your domain name via an insecure connection (for a given period of time) by setting the “Strict-Transport-Security” header. This reduces your exposure to some SSL-stripping man-in-the-middle (MITM) attacks.
SecurityMiddleware will set this header for you on all HTTPS responses if you set the SECURE_HSTS_SECONDS setting to a nonzero integer value.
Additionally, if you set the SECURE_HSTS_INCLUDE_SUBDOMAINS setting to True, SecurityMiddleware will add the includeSubDomains tag to the Strict-Transport-Security header. This is recommended, otherwise your site may still be vulnerable via an insecure connection to a subdomain.
The HSTS policy applies to your entire domain, not just the URL of the response that you set the header on. Therefore, you should only use it if your entire domain is served via HTTPS only.
Browsers properly respecting the HSTS header will refuse to allow users to bypass warnings and connect to a site with an expired, self-signed, or otherwise invalid SSL certificate. If you use HSTS, make sure your certificates are in good shape and stay that way!
If you are deployed behind a load-balancer or reverse-proxy server, and the Strict-Transport-Security header is not being added to your responses, it may be because Django doesn’t realize when it’s on a secure connection; you may need to set the SECURE_PROXY_SSL_HEADER setting.
Some browsers will try to guess the content types of the assets that they fetch, overriding the Content-Type header. While this can help display sites with improperly configured servers, it can also pose a security risk.
To learn more about this header and how the browser treats it, you can read about it on the IE Security Blog.
To prevent the browser from guessing the content type, and force it to always use the type provided in the Content-Type header, you can pass the X-Content-Type-Options: nosniff header. SecurityMiddleware will do this for all responses if the SECURE_CONTENT_TYPE_NOSNIFF setting is True.
The X-XSS-Protection header is used to control the operation of the XSS filter.
To enable the XSS filter in the browser, and force it to always block suspected XSS attacks, you can pass the X-XSS-Protection: 1; mode=block header. SecurityMiddleware will do this for all responses if the SECURE_BROWSER_XSS_FILTER setting is True.
The XSS filter does not prevent XSS attacks on your site, and you should ensure that you are taking all other possible mesaures to prevent XSS attacks. The most obvious of these is validating and sanitizing all input.
If your site offers both HTTP and HTTPS connections, most users will end up with an unsecured connection by default. For best security, you should redirect all HTTP connections to HTTPS.
If you set the SECURE_SSL_REDIRECT setting to True, SecurityMiddleware will permanently (HTTP 301) redirect all HTTP connections to HTTPS.
For performance reasons, it’s preferable to do these redirects outside of Django, in a front-end loadbalancer or reverse-proxy server such as nginx. In some deployment situations this isn’t an option - SECURE_SSL_REDIRECT is intended for those cases.
If the SECURE_SSL_HOST setting has a value, all redirects will be sent to that host instead of the originally-requested host.
If there are a few pages on your site that should be available over HTTP, and not redirected to HTTPS, you can list regular expressions to match those URLs in the SECURE_REDIRECT_EXEMPT setting.
If you are deployed behind a load-balancer or reverse-proxy server, and Django can’t seem to tell when a request actually is already secure, you may need to set the SECURE_PROXY_SSL_HEADER setting.
Django 1.4+ offers the same functionality built-in. The Django setting works identically to this version.
In some deployment scenarios, Django’s request.is_secure() method returns False even on requests that are actually secure, because the HTTPS connection is made to a front-end loadbalancer or reverse-proxy, and the internal proxied connection that Django sees is not HTTPS. Usually in these cases the proxy server provides an alternative header to indicate the secured external connection.
If this is your situation, you can set the SECURE_PROXY_SSL_HEADER setting to a tuple of (“header”, “value”); if “header” is set to “value” in request.META, django-secure will tell Django to consider it a secure request (in other words, request.is_secure() will return True for this request). The “header” should be specified in the format it would be found in request.META (e.g. “HTTP_X_FORWARDED_PROTOCOL”, not “X-Forwarded-Protocol”). For example:
SECURE_PROXY_SSL_HEADER = ("HTTP_X_FORWARDED_PROTOCOL", "https")
If you set this to a header that your proxy allows through from the request unmodified (i.e. a header that can be spoofed), you are allowing an attacker to pretend that any request is secure, even if it is not. Make sure you only use a header that your proxy sets unconditionally, overriding any value from the request.