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

[David Waite <[e-mail]>]

Agreed, if the BCP is meant to describe javascript behavior for best practices as respect to being an OAuth client, I’m unsure what would belong in this document for javascript which is instead interacting over non-standard mechanisms with an OAuth client. 

Instead, it would be generalized browser javascript security practices. It would be sure to overlap with some of the recommendations made to a client managing OAuth in the browser, but such a spec wouldn’t be under the umbrella of the OAuth WG - would it? We would be talking about general non-OAuth browser security practices around important cookies.

If (as Hans proposed) there was a mechanism for javascript to get access tokens to interact with protected resources in lieu of the client, there could be BCP around managing that (which would likely also overlap with a genuine javascript-in-browser client), but unfortunately there aren’t technical specs to support that sort of architecture yet.

-DW

> On Dec 2, 2018, at 4:43 PM, Aaron Parecki <[e-mail]> 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 <http://aaronparecki.com/>
> 
> 
> 
> On Sat, Dec 1, 2018 at 11:31 PM Torsten Lodderstedt <[e-mail] <mailto:[e-mail]>> 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 <[e-mail] <mailto:[e-mail]>>:
> 
>> 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 <[e-mail] <mailto:[e-mail]>>:
>>> 
>>>> 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 <[e-mail] <mailto:[e-mail]>>:
>>>> 
>>>>> 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 <[e-mail] <mailto:[e-mail]>> On Behalf Of Brian Campbell
>>>>> Sent: Friday, November 30, 2018 11:43 PM
>>>>> To: Torsten Lodderstedt <[e-mail] <mailto:[e-mail]>>
>>>>> Cc: oauth <[e-mail] <mailto:[e-mail]>>
>>>>> Subject: Re: [OAUTH-WG] draft-parecki-oauth-browser-based-apps-00
>>>>> 
>>>>>  
>>>>> 
>>>>>  
>>>>> 
>>>>> On Sat, Nov 17, 2018 at 4:07 AM Torsten Lodderstedt <[e-mail] <mailto:[e-mail]>> wrote:
>>>>> 
>>>>> > Am 15.11.2018 um 23:01 schrieb Brock Allen <[e-mail] <mailto:[e-mail]>>:
>>>>> > 
>>>>> > 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 <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 <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 <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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