Re: [OAUTH-WG] New OAuth for Browser-Based Apps draft -02

[Brian Campbell <[e-mail]>]

On Mon, Jul 22, 2019 at 7:31 AM Torsten Lodderstedt <[e-mail]>
wrote:

>
> 2) Regarding architectures: I think this BCP should focus on
> recommendations for securely implementing OAuth in the different potential
> architecture. I don’t think we should get into the business of recommending
> and assessing other solutions (e.g. section 6.1.). Just to give you an
> example: Section 6.1. states
>
> "OAuth and OpenID Connect provide very little benefit in this deployment
> scenario, so it is recommended to reconsider whether you need OAuth or
> OpenID Connect at all in this case.”
>
> Really? What experiences is this statement based on? In my experience,
> sharing the same domain == host name tells you nothing about the overall
> architecture of a certain deployment. There may be several reasons why
> OAuth could be good choice in such a scenario, e.g. security considerations
> (since your common domain is just a proxy server encapsulating a whole
> universe of systems) or even modularity as an architecture principle.
>
> I suggest to remove section c. and to rephrase the second paragraph of the
> abstract.
>

I believe the experiences that the statement is based on are the
predominant practice over the course of much of the history of the web of
using a cookie to maintain an authenticated HTTP session in web
applications. When the script of the browser-based application is served
from a domain that can share cookies with the domain of the API, then
cookies can still be used to authorize requests (even if those requests are
API calls rather than full page HTTP request/response). And I do believe
that's likely a better decision in a lot of such cases.

That authenticated HTTP session may be establish from a username/password
form submission, FIDO/WebAuthn, or whatever.  Even as a result of an OpenID
Connect flow. Or even SAML for that matter. But the the requests after that
are authorized by the cookie.

I think there's a tendency to assume because SPA style apps make API calls,
they simply must use OAuth. Because API implies OAuth in the minds of many
(which is a sign of its success). But OAuth isn't necessarily the only
thing that can be used for API authorization. Cookies work too. I
think/hope that's what Section 6.1. is getting at - providing some
potential guidance that OAuth might not necessarily be the right choice in
those cases where a common domain allows for a cookie. Perhaps the text in
that section could be phased in a different or better way, but I think its
useful to have some mention of in this document.

Although taking out "and OpenID Connect" from the sentence quoted above
might be more appropriate and alleviate some confusion.

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