[Openid-specs-ab] Hybird flow refresh tokens with javascript clients

Brock Allen brockallen at gmail.com
Mon Jul 30 01:19:35 UTC 2018

Suresh --

Can you elaborate on your scenarios where a SPA (client-side browser based application) would need to maintain access tokens longer than the user's browser session?

I'm very curious. Thanks.


On 7/29/2018 6:38:29 PM, SureshAtt via Openid-specs-ab <openid-specs-ab at lists.openid.net> wrote:
Hello Nat and David,

Thanks a lot for your replies. As David mentioned there is already a need for SPA to get longer access to user resources and I have seen different project solves this problem in different ways (ex: using iframes). This led me to think if hybrid flow was desinged to handle this issue as well using refresh tokens, but now I am clear it is not. 

Thanks & regards,
Suresh Attanayake

On Sun, Jul 29, 2018 at 7:39 AM Nat Sakimura <sakimura at gmail.com [mailto:sakimura at gmail.com]> wrote:


I made a reply with too much haste as I was about to go out then but the point is this: 

As 10.4 of RFC6749 states: 

The authorization server MUST maintain the binding between a refresh token and the client to whom it was issued.

The most common and safe way of achieve it is to have
the client authenticate to the authorization server.
Thus, the client has to be a confidential client,
i.e., the client that can keep the confidentiality of its key so that
it can use a sender constrained tokens)

(Note: RFC6749 does not define confidential client.
Public client is defined slightly better but it still is sloppy like
native applications are public client -- well, what if they did a dynamic registration
to get a per-client secret? IMHO, these should be fixed.)

So, getting back to Suresh's question, it is the intent of the authors not to allow the Javascript 
clients on a web browser to get refresh token. If the client is effectively a confidential client 
e.g., by using Token Binding, then, it in principle should be able to make use of a 
Token Bound refresh token, although, it kinds of infringes on RFC6749. 
I suppose the OAuth Token Binding spec should update that bit. 


Nat Sakimura

On Sun, Jul 29, 2018 at 12:36 PM David Waite <david at alkaline-solutions.com [mailto:david at alkaline-solutions.com]> wrote:

> On Jul 28, 2018, at 6:32 PM, Nat Sakimura via Openid-specs-ab <openid-specs-ab at lists.openid.net [mailto:openid-specs-ab at lists.openid.net]> wrote:

> A public client cannot get refresh token.
> Assuming that you mean "a client working within a browser using JavaScript" by "a JavaScript Client" since it is a public client, it cannot get a refresh token.

I’m not familiar with this restriction, my understanding is that it is valid and in fact not uncommon for public clients to get and use refresh tokens. RFC 6749 for example does not state such a restriction, and even language around differing behavior with confidential clients vs public clients:

   "Because refresh tokens are typically long-lasting credentials used to
   request additional access tokens, the refresh token is bound to the
   client to which it was issued.  If the client type is confidential or
   the client was issued client credentials (or assigned other
   authentication requirements), the client MUST authenticate with the
   authorization server as described in Section 3.2.1”

There are quite legitimate reasons for public clients to have refresh tokens, and quite a few mobile apps which already are using refresh tokens.

With SPA clients for instance, it allows you to extend access without hidden Iframe tricks (and thus could be a workaround to ITP 2.0 blocking state access on XHR / frames / non-interactive redirects, and such forms of cross-domain access causing IDPs to be flagged as trackers)



Nat Sakimura (=nat)
Chairman, OpenID Foundation
http://nat.sakimura.org/ [http://nat.sakimura.org/]


Suresh Attanayake

Blog : http://sureshatt.blogspot.com/ [http://sureshatt.blogspot.com/] 
Web : http://www.ssoarcade.com/ [http://www.ssoarcade.com/]
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