Skip to main content

AOL OpenAuth and Atom Publishing Protocol

I'm looking to see how best to implement Atom-compatibleauthentication for AOL's OpenAuth service. The service provides ways for users to authenticate themselves and togrant permissions to services to do things such as read buddy lists onbehalf of a user.  These permissions are encapsulated in a portabletoken which can be passed around.  The primary use cases for thisinvolve pure web based AJAX applications, so making this something thata generic application can deal with isn't fully specified.

So, here are my thoughts.  Let's say the client has a token stringwhich encapsulates authentication and authorization.  They need to sendthis along with an Atom Publishing Protocol (APP) request. 

Windows Live and GData both implement custom RFC 2617 WWW-Authenticate:headerschemes.  Unfortunately they don't follow exactly the same pattern,or I'd just copy it.  But using RFC 2617 is clearly the right approachif the server can support it.  So here's a proposal:

If a client has an OpenAuth token, it sends an Authorization: header. The format looks like this:
Authorization: OpenAuth token="..."
where ... contains the base64-encoded token data (an opaque string,essentially).

When there is a problem, or the Authorization: header is missing, a401 response is returned with a WWW-Authenticate: header.
401 Need user consent
WWW-Authenticate: OpenAuth realm="RealmString",fault="NeedConsent",url=""
where the status code contains a human readable message, and theWWW-Authenticate header contains the precise fault code -- NeedToken,NeedConsent, ExpiredToken.  If present, the urlparameter gives the URL of an HTML page which can be presented to theend user to login or grant permissions.  For example it can point to alogin page if the fault is NeedToken.  A client would then need to dothe following in response:
  1. Append a "&succUrl=..." parameter to the url, telling theOpenAuth service where to go when the user successfully logs in orgrants permission. 
  2. Open a web browser or browser widget control with the givencomposed URL, and present to the user.
  3. Be prepared to handle an invocation of the succUrl with anappended token parameter, giving a new token to use for subsequentrequests.
Note that the succUrl can be a javascript: URL, or a custom scheme(e.g., aim:) if your destination client is not a web browser.  Or itcould be pointing to a local web server(http://localhost:1080/openauthcallback.cgi) or perhaps other schemesto get the token from point A to point B.  Whatever method is chosen,eventually the client will receive an OpenAuth token that it can use totry (or re-try) the Atom request.

As a wrinkle, to enhance autodiscovery, perhaps we should allow an"Authorization: OpenAuth" header with no token on any request(including HEAD).  The server could then respond with a 401 andfault="NeedToken", telling the client what URL to use for loginauthentication.  The interesting thing about this is that the protocolis then truly not tied to any particular authentication service --anyone who implements this fairly simple protocol with opaque tokenscan then play with anyone else.  The whole thing could be built on topof OpenID, for example. 

Perhaps this doesn't quite work.  I notice that the Flickr APIs don'tdo this, and instead have non-browsers establish a session with aclient-generated unique key ("frob").  But this requires that users endup looking at a browser screen that tells them to return to theirapplication to re-try the request.  Which the above scheme couldcertainly do as well, by making the succUrl point at such a page.  Sois there a reason why Flickr doesn't redirect?  There's likely a gapingsecurity hole here that I'm just missing.

Popular posts from this blog

Personal Web Discovery (aka Webfinger)

There's a particular discovery problem for open and distributed protocols such as OpenID, OAuth, Portable Contacts, Activity Streams, and OpenSocial.  It seems like a trivial problem, but it's one of the stumbling blocks that slows mass adoption.  We need to fix it.  So first, I'm going to name it:

The Personal Web Discovery Problem:  Given a person, how do I find out what services that person uses?
This does sound trivial, doesn't it?  And it is easy as long as you're service-centric; if you're building on top of social network X, there is no discovery problem, or at least only a trivial one that can be solved with proprietary APIs.  But what if you want to build on top of X,Y, and Z?  Well, you write code to make the user log in to each one so you can call those proprietary APIs... which means the user has to tell you their identity (and probably password) on each one... and the user has already clicked the Back button because this is complicated and annoying.

The problem with creation date metadata in PDF documents

Last night Rachel Maddow talked about an apparently fake NSA document "leaked" to her organization.  There's a lot of info there, I suggest you listen to the whole thing:

There's a lot to unpack there but it looks like somebody tried to fool MSNBC into running with a fake accusation based on faked NSA documents, apparently based on cloning the document the Intercept published back on 6/5/2017, which to all appearances was itself a real NSA document in PDF form.

I think the main thrust of this story is chilling and really important to get straight -- some person or persons unknown is sending forged PDFs to news organization(s), apparently trying to get them to run stories based on forged documents.  And I completely agree with Maddow that she was right to send up a "signal flare" to all the news organizations to look out for forgeries.  Really, really, really import…
Twister is interesting.  It's a decentralized "microblogging" system based on putting together existing protocols:  Bitcoin, distributed hash tables, and Bittorrent.  The most interesting part for me is using Bitcoin for user registration and spam control.  Federated systems handle this with federated trust, which is at least conceptually simple.  The Twister/Bitcoin mechanism looks intriguing though I don't know enough about Bitcoin to really comment.  Need to read further.