AD FS 2.0 Authentication and AJAX

Question

I have a web site that is trying to call an MVC controller action on another web site. These sites are both setup as relying party trusts in AD FS 2.0. Everything authenticates and works fine when opening pages in the browser window between the two sites. However, when trying to call a controller action from JavaScript using the jQuery AJAX method it always fails. Here is a code snippet of what I'm trying to do...

$.ajax({
  url: "relyingPartySite/Controller/Action",
  data: { foobar },
  dataType: "json",
  type: "POST",
  async: false,
  cache: false,
  success: function (data) {
    // do something here
  },
  error: function (data, status) {
    alert(status);
  }
});

The issue is that AD FS uses JavaScript to post a hidden html form to the relying party. When tracing with Fiddler I can see it get to the AD FS site and return this html form which should post and redirect to the controller action authenticated. The problem is this form is coming back as the result of the ajax request and obviously going to fail with a parser error since the ajax request expects json from the controller action. It seems like this would be a common scenario, so what is the proper way to communicate with AD FS from AJAX and handle this redirection?

Answer 1

You have two options. More info here.

The first is to share a session cookie between an entry application (one that is HTML based) and your API solutions. You configure both applications to use the same WIF cookie. This only works if both applications are on the same root domain. See the above post or this stackoverflow question.

The other option is to disable the passiveRedirect for AJAX requests (as Gutek's answer). This will return a http status code of 401 which you can handle in Javascript. When you detect the 401, you load a dummy page (or a "Authenticating" dialog which could double as a login dialog if credentials need to be given again) in an iFrame. When the iFrame has completed you then attempt the call again. This time the session cookie will be present on the call and it should succeed.

//Requires Jquery 1.9+
var webAPIHtmlPage = "http://webapi.somedomain/preauth.html"

function authenticate() {
    return $.Deferred(function (d) {
        //Potentially could make this into a little popup layer 
        //that shows we are authenticating, and allows for re-authentication if needed
        var iFrame = $("<iframe></iframe>");
        iFrame.hide();
        iFrame.appendTo("body");
        iFrame.attr('src', webAPIHtmlPage);
        iFrame.load(function () {
            iFrame.remove();
            d.resolve();
        });
    });
};

function makeCall() {
    return $.getJSON(uri)
                .then(function(data) {
                        return $.Deferred(function(d) { d.resolve(data); });
                    },
                    function(error) {
                        if (error.status == 401) {
                            //Authenticating, 
                            //TODO:should add a check to prevnet infinite loop
                            return authenticate().then(function() {
                                //Making the call again
                                return makeCall();

                            });
                        } else {
                            return $.Deferred(function(d) {
                                d.reject(error);
                            });
                        }
                });
}

Answer 2

If you do not want to receive HTML with the link you can handle AuthorizationFailed on WSFederationAuthenticationModule and set RedirectToIdentityProvider to false on Ajax calls only.

for example:

FederatedAuthentication.WSFederationAuthenticationModule.AuthorizationFailed += (sender, e) =>
{
    if (Context.Request.RequestContext.HttpContext.Request.IsAjaxRequest())
    {
        e.RedirectToIdentityProvider = false;
    }
};

This with Authorize attribute will return you status code 401 and if you want to have something different, then you can implement own Authorize attribute and write special code on Ajax Request.