Pete FreitagAjax Same Origin Policy No More with Firefox 3.5
By Pete Freitag
Firefox 3.5 now allows you to make AJAX Requests, or more correctly XMLHttpRequests cross domain (in other words foo.com can make XHR requests to bar.com). When I heard about this, my first is that they would use the cross-domain.xml file that Flash has supported for years to achieve this. They took a different approach, and use a HTTP header instead, which I think makes more sense.
So how does it work...
When you make a request using the XMLHttpRequest object it sends an Origin header (this is new, I wrote a blog entry about the Origin header as well) which contains the domain of the requesting page. The HTTP Response can send a HTTP header: Access-Control-Allow-Origin: * which means that any domain can access this page. You could also send a response header like this: Access-Control-Allow-Origin: http://example.com which only allows the example.com as an origin. The Access-Control-Allow-Origin header should contain a comma separated list of acceptable domains or a *.
For POST requests, and requests that want to read response headers a HTTP OPTIONS request is made first, that sends headers such as # Access-Control-Request-Method: POST in the request.
You can read more about this feature here
Ajax Same Origin Policy No More with Firefox 3.5 was first published on June 30, 2009.
If you like reading about ajax, firefox, xmlhttprequest, javascript, or http then you might also like:
- AJAX on IE - back to the IFRAME
- Firefox 3.5 Introduces Origin Header, Security Features
- AJAX Presentation Outline
- Cross Domain Data Theft using CSS
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e:g xhrObject.setRequestHeader("Origin","foo.com")
Using custom request and response headers seems sketchy - with the addition of response headers controlling cacheability of permissions it feels like a separate resource (like cross-domain.xml) would have had more reuse of existing functionality & may have been easier to set up for sites that just want to let their data services be 'public'.
I do like the discussion of using http authentication, that also seems like an easy way for data services to be public.
2. For Pre-Flighted requests an OPTIONS request is sent to the server and it responds with headers that indicate who and what is allowed.
CF should handle this so some security checks on referer and requested methods can be returned. But how do you get IIS to pass an OPTIONS method request to CF?
I can't get that to work either, and I've tried all the verb settings in IE and CF is mapped to respond to all-verbs, but no dice...
From firefox I can't access the contents of jsp file on the server due to cross-domain issue. Should I set the header in the jsp file and access the contents as I am doing now... kindly suggest.. I am struggling to solve this problem for long...