django: csrftoken COOKIE vs. csrfmiddlewaretoken HTML Form value

Question

Trying to learn about security. Curious about why in django when submitting a form (a POST), there are 2 separate \"elements\" that contain the same csrf token value:

Answer 1

The cookie is there for AJAX support. Quoting the Django docs:

While the above method can be used for AJAX POST requests, it has some inconveniences: you have to remember to pass the CSRF token in as POST data with every POST request. For this reason, there is an alternative method: on each XMLHttpRequest, set a custom X-CSRFToken header to the value of the CSRF token. This is often easier, because many javascript frameworks provide hooks that allow headers to be set on every request. In jQuery, you can use the ajaxSend event as follows:

$('html').ajaxSend(function(event, xhr, settings) {
    function getCookie(name) {
        var cookieValue = null;
        if (document.cookie && document.cookie != '') {
            var cookies = document.cookie.split(';');
            for (var i = 0; i < cookies.length; i++) {
                var cookie = jQuery.trim(cookies[i]);
                // Does this cookie string begin with the name we want?
                if (cookie.substring(0, name.length + 1) == (name + '=')) {
                    cookieValue = decodeURIComponent(cookie.substring(name.length + 1));
                    break;
                }
            }
        }
        return cookieValue;
    }
    if (!(/^http:.*/.test(settings.url) || /^https:.*/.test(settings.url))) {
        // Only send the token to relative URLs i.e. locally.
        xhr.setRequestHeader("X-CSRFToken", getCookie('csrftoken'));
    }
});

Adding this to a javascript file that is included on your site will ensure that AJAX POST requests that are made via jQuery will not be caught by the CSRF protection.