Hi Luke,

I have to confess that I was not aware of technique of passing parameters after the fragment to take advantage of browser caching, until you blogged about it. Since then, we've noticed that developers have been doing this, and in fact, we fixed the same bug on our OAuth service just last week.

We will update our OP to support return_to URLs with a fragment. I'll let you know when it's fixed.

Thanks
Allen



Luke Shepard wrote:
Hi-

I've noticed an ambiguity with the way URLs are handled that exists in the current spec. I'm hoping we can resolve it for OpenID 2.1.

When we move the OpenID transaction into a popup window, we need a way for the popup to communicate back with the parent. The way to do this is to set a return_to URL that, when loaded, reads the parameters and communicates with the parent window somehow.

Here's a description of a technique:
http://www.sociallipstick.com/2009/02/04/how-to-accept-openid-in-a-popup-without-leaving-the-page/

A simple way to do this is to have a simple receiver. The response will append query parameters:

http://open.lukeshepard.com/openid_receiver.php?openid.ns=......

However, there is a small performance problem with this approach. The user will see a blank-looking popup for a moment while the server processes the OpenID arguments. An optimization is to put up a simple, cacheable static HTML file that chucks the OpenID params back to the parent frame. The parent can then provide some visual feedback to the user while it sends the OpenID parameters off for processing. This results in a snappier experience.

If the static HTML file has no parameters and sends out long-lived cache headers, then the response won't even trigger a server load, and the whole process can appear faster to the user. In this case, the response would look like this:

http://open.lukeshepard.com/openid_receiver.html#openid.ns=......

Note that the hash appears instead of a question-mark. That tells the browser that it doesn't need to load an extra file, and it can save perhaps a quarter or half second of latency for the user on average.

Okay, so the point is that different OpenID providers currently interpret the hash differently. I think we should explicitly define a behavior that makes sense and accomodates the above suggestion. Here's how they currently behave.

When given a return_to of http://open.lukeshepard.com/openid_receiver.html?query#hash

Google: http://open.lukeshepard.com/openid_receiver.html?query#hash?openid.ns=.... Yahoo: http://open.lukeshepard.com/openid_receiver.html?query#hash?openid.ns=.... MySpaceID: http://open.lukeshepard.com/openid_receiver.html?query&openid.ns=....#hash <http://open.lukeshepard.com/openid_receiver.html?query&openid.ns=....#hash>
MyOpenID: fails outright - "invalid return_to"

By the URL spec, Myspace is technically correct and Google/Yahoo are wrong. But the "correct" way doesn't allow the performance optimization listed above. I'd like to see a way to accommodate the hash url.

One crude way to do it would be to have the caller specify that they want the return_to args simply appended instead of integrated into the URL- perhaps an argument like openid.append_return_to_params=true. But that sounds hackish and I'd love to hear feedback on a better way to do this.

Also, let me know if this is the wrong list or whatever.

thanks,
- Luke
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