Lorenzo Lorenzo - 3 months ago 15
Ajax Question

jQuery Ajax calls and the Html.AntiForgeryToken()

I have implemented in my app the mitigation to CSRF attacks following the informations that I have read on some blog post around the internet. In particular these post have been the driver of my implementation



Basically those articles and recommendations says that to prevent the CSRF attack anybody should implement the following code:

1) Add the
[ValidateAntiForgeryToken]
on every action that accept the POST Http verb

[HttpPost]
[ValidateAntiForgeryToken]
public ActionResult SomeAction( SomeModel model ) {
}


2) Add the
<%= Html.AntiForgeryToken() %>
helper inside forms that submits data to the server

<div style="text-align:right; padding: 8px;">
<%= Html.AntiForgeryToken() %>
<input type="submit" id="btnSave" value="Save" />
</div>


Anyway in some parts of my app I am doing Ajax POSTs with jQuery to the server without having any form at all. This happens for example where I am letting the user to click on an image to do a specific action.

Suppose I have a table with a list of activities. I have an image on a column of the table that says "Mark activity as completed" and when the user click on that activity I am doing the Ajax POST as in the following sample:

$("a.markAsDone").click(function (event) {
event.preventDefault();
$.ajax({
type: "post",
dataType: "html",
url: $(this).attr("rel"),
data: {},
success: function (response) {
// ....
}
});
});


How can I use the
<%= Html.AntiForgeryToken() %>
in these cases? Should I include the helper call inside the data parameter of the Ajax call?

Sorry for the long post and thanks very much for helping out

EDIT:

As per jayrdub answer I have used in the following way

$("a.markAsDone").click(function (event) {
event.preventDefault();
$.ajax({
type: "post",
dataType: "html",
url: $(this).attr("rel"),
data: {
AddAntiForgeryToken({}),
id: parseInt($(this).attr("title"))
},
success: function (response) {
// ....
}
});
});

Answer

I use a simple js function like this

AddAntiForgeryToken = function(data) {
    data.__RequestVerificationToken = $('#__AjaxAntiForgeryForm input[name=__RequestVerificationToken]').val();
    return data;
};

Since every form on a page will have the same value for the token, just put something like this in your top-most master page

<%-- used for ajax in AddAntiForgeryToken() --%>
<form id="__AjaxAntiForgeryForm" action="#" method="post"><%= Html.AntiForgeryToken()%></form>  

Then in your ajax call do (edited to match your second example)

$.ajax({
    type: "post",
    dataType: "html",
    url: $(this).attr("rel"),
    data: AddAntiForgeryToken({ id: parseInt($(this).attr("title")) }),
    success: function (response) {
        // ....
    }
});
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