Re: [OAUTH-WG] draft-parecki-oauth-browser-based-apps-00

I would also like to see something to that effect. I feel that sometimes
because SPAs use APIs, there's an unchallenged assumption that OAuth also
has to be used with the in-browser code accessing those APIs. Even if the
details are out of scope for this document, some text like the below at
least gives a nod to the possibility of different approaches, which may
ultimately be more secure and easier to mange.
https://tools.ietf.org/html/draft-parecki-oauth-browser-based-apps-00#section-5.1
kinda does this too but I'm a +1 for a little something along the lines of
what is being discussed recently in this thread.

On Mon, Dec 3, 2018 at 7:57 AM Aaron Parecki <aaron@parecki.com> wrote:

> I support adding something to that effect, but would like to make it clear
> that this removes the app from being covered under this BCP. How about:
>
> ---
> Implementations MAY consider moving the authorization code exchange and
> handling of access and refresh tokens to a backend component in order to
> avoid the risks inherent in handling access tokens from a purely browser
> based app. In this case, the backend component can be a confidential client
> and can be secured accordingly.
>
> Security of the connection between code running in the browser and this
> backend component is assumed to utilize browser-level protection
> mechanisms. Details are out of scope of this document.
> ---
>
>
>
>
> On Mon, Dec 3, 2018 at 3:15 AM Torsten Lodderstedt <
> torsten@lodderstedt.net <torsten@lodderstedt..net>> wrote:
>
>> Interesting. Even on this list people felt to see that moving some logic
>> to a backend could solve some of the problems raised. What I want to convey
>> is: the solution to a problem in the OAuth space does not necessarily need
>> to be found on the OAuth protocol level. That’s a best practice in the same
>> way as some OAuth pattern.
>>
>> What I’m suggesting is a statement in the BCP like
>>
>> —
>> Implementations MAY consider to move authorization code exchange and
>> handling of access and refresh tokens to a backend component in order to
>> fulfill their security goals.
>>
>> Security of the connection between code running in the browser and this
>> backend component is assumed to utilize browser-level protection
>> mechanisms. Details are out of scope of this document.
>> —
>>
>> > Am 03.12.2018 um 11:19 schrieb John Bradley <ve7jtb@ve7jtb.com>:
>> >
>> > This is my point.
>> >
>> > From a security perspective we have a server based confidential
>> client..   The fact that it has a angular or other JS UI protected by a
>> cookie seems to not be especially relucent to OAuth.
>> >
>> > Perhaps from the developer point of view they have a JS SPA and the
>> only difference to them is in one case they are including the OAuth client
>> and in the other they are using a server based proxy. So they see it as the
>> same.
>> >
>> > Perhaps it is perspective.
>> >
>> > On Mon, Dec 3, 2018, 12:44 AM Aaron Parecki <aaron@parecki.com wrote:
>> > In this type of deployment, as far as OAuth is concerned, isn't the
>> backend web server a confidential client? Is there even anything unique to
>> this situation as far as OAuth security goes?
>> >
>> > I wouldn't have expected an Angular app that talks to its own server
>> backend that's managing OAuth credentials to fall under the umbrella of
>> this BCP.
>> >
>> > ----
>> > Aaron Parecki
>> > aaronparecki.com
>> >
>> >
>> >
>> > On Sat, Dec 1, 2018 at 11:31 PM Torsten Lodderstedt <
>> torsten@lodderstedt.net> wrote:
>> > the UI is rendered in the frontend, UI control flow is in the
>> frontend.. just a different cut through the web app’s layering
>> >
>> > All Angular apps I have seen so far work that way. And it makes a lot
>> of sense to me. The backend can aggregate and optimize access to the
>> underlying services without the need to fully expose them.
>> >
>> > Am 02.12.2018 um 00:44 schrieb John Bradley <ve7jtb@ve7jtb.com>:
>> >
>> >> How is that different from a regular server client with a web
>> interface if the backed is doing the API calls to the RS?
>> >>
>> >>
>> >>
>> >> On 12/1/2018 12:25 PM, Torsten Lodderstedt wrote:
>> >>> I forgot to mention another (architectural) option: split an
>> application into frontend provided by JS in the browser and a backend,
>> which takes care of the business logic and handles tokens and API access.
>> Replay detection at the interface between SPA and backend can utilize
>> standard web techniques (see OWASP). The backend in turn can use mTLS for
>> sender constraining.
>> >>>
>> >>> Am 01.12.2018 um 15:34 schrieb Torsten Lodderstedt <
>> torsten@lodderstedt.net>:
>> >>>
>> >>>> IMHO the best mechanism at hand currently to cope with token
>> leakage/replay in SPAs is to use refresh tokens (rotating w/ replay
>> detection) and issue short living and privilege restricted access tokens.
>> >>>>
>> >>>> Sender constrained access tokens in SPAs need adoption of token
>> binding or alternative mechanism. mtls could potentially work in
>> deployments with automated cert rollout but browser UX and interplay with
>> fetch needs some work. We potentially must consider to warm up application
>> level PoP mechanisms in conjunction with web crypto. Another path to be
>> evaluated could be web auth.
>> >>>>
>> >>>> Am 01.12.2018 um 10:15 schrieb Hannes Tschofenig <
>> Hannes.Tschofenig@arm.com>:
>> >>>>
>> >>>>> I share the concern Brian has, which is also the conclusion I came
>> up with in my other email sent a few minutes ago.
>> >>>>>
>> >>>>>
>> >>>>>
>> >>>>> From: OAuth <oauth-bounces@ietf.org> On Behalf Of Brian Campbell
>> >>>>> Sent: Friday, November 30, 2018 11:43 PM
>> >>>>> To: Torsten Lodderstedt <torsten@lodderstedt.net>
>> >>>>> Cc: oauth <oauth@ietf.org>
>> >>>>> Subject: Re: [OAUTH-WG] draft-parecki-oauth-browser-based-apps-00
>> >>>>>
>> >>>>>
>> >>>>>
>> >>>>>
>> >>>>>
>> >>>>> On Sat, Nov 17, 2018 at 4:07 AM Torsten Lodderstedt <
>> torsten@lodderstedt.net> wrote:
>> >>>>>
>> >>>>> > Am 15.11.2018 um 23:01 schrieb Brock Allen <brockallen@gmail.com
>> >:
>> >>>>> >
>> >>>>> > So you mean at the resource server ensuring the token was really
>> issued to the client? Isn't that an inherent limitation of all bearer
>> tokens (modulo HTTP token binding, which is still some time off)?
>> >>>>>
>> >>>>> Sure. That’s why the Security BCP recommends use of TLS-based
>> methods for sender constraining access tokens (
>> https://tools.ietf.org/html/draft-ietf-oauth-security-topics-09#section-2..2)
>> Token Binding for OAuth (
>> https://tools.ietf.org/html/draft-ietf-oauth-token-binding-08) as well
>> as Mutual TLS for OAuth (
>> https://tools.ietf.org/html/draft-ietf-oauth-mtls-12) are the options
>> available.
>> >>>>>
>> >>>>>
>> >>>>>
>> >>>>> Unfortunately even when using the token endpoint, for SPA /
>> in-browser client applications, the potential mechanisms for
>> sender/key-constraining access tokens don't work very well or maybe don't
>> work at all. So I don't know that the recommendation is very realistic.
>> >>>>>
>> >>>>>
>> >>>>>
>> >>>>>
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>> --
> ----
> Aaron Parecki
> aaronparecki.com
> @aaronpk <http://twitter.com/aaronpk>
>
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