that’s certainly true, but that might by a web server with static content only.

If the server is a real backend, there is even less reasons to use a implicit 
or hybrid. No even a performance gain in comparison to code.

> Am 21.11.2018 um 14:24 schrieb George Fletcher <[email protected]>:
> 
> An SPA has a backend because it has to be loaded from somewhere :)
> 
>> On 11/21/18 3:47 AM, Torsten Lodderstedt wrote:
>> We had a discussion about this topic on Twitter 
>> https://twitter.com/Apl3b/status/1064854507606208513
>> 
>> Outcome is POST requires a backend to receive the request so it’s not a 
>> viable solution for SPAs.
>> 
>>>> Am 20.11.2018 um 23:29 schrieb John Bradley <[email protected]>:
>>>> 
>>>> Post response works OK for server based clients.  I don't think POST works 
>>>> for single page applications.  
>>>> 
>>>> Basically that would be something more like postmessage between two JS 
>>>> apps.  
>>>> 
>>>> Postmessage also has security issues passing a access token and leaking..  
>>>> 
>>>> Perhaps someone more familiar with SPA can comment on POST.  
>>>> 
>>>> John B. 
>>>> 
>>>> 
>>>> 
>>>> On Tue, Nov 20, 2018, 6:40 PM George Fletcher <[email protected] wrote:
>>>> Hi Mike,
>>>> 
>>>> The Form Post Response Mode keeps the access_token out of the URL, but it 
>>>> doesn't prevent the token from traversing through the browser. So a 
>>>> man-in-the-browser attack may be able to intercept the values. It should 
>>>> help with leakage in logs.
>>>> 
>>>> Thanks,
>>>> George
>>>> 
>>>> On 11/20/18 4:00 PM, Mike Jones wrote:
>>>> Next question – doesn’t using the Form Post Response Mode 
>>>> https://openid.net/specs/oauth-v2-form-post-response-mode-1_0.html 
>>>> mitigate the threats you’re describing below John?  If so, I believe the 
>>>> Security Topics draft should say this.
>>>> 
>>>>  
>>>> 
>>>> I believe we owe it to readers to present the complete picture, which is 
>>>> why I believe that describing profiles using ID Tokens and the Form Post 
>>>> Response Mode are in scope.
>>>> 
>>>>  
>>>> 
>>>>                                                        -- Mike
>>>> 
>>>>  
>>>> 
>>>> From: OAuth <[email protected]> On Behalf Of John Bradley
>>>> Sent: Tuesday, November 20, 2018 7:47 AM
>>>> To: [email protected]
>>>> Subject: Re: [OAUTH-WG] OAuth Security Topics -- Recommend authorization 
>>>> code instead of implicit
>>>> 
>>>>  
>>>> 
>>>> Yes the at_hash protects the client from accepting an injected AT. 
>>>> 
>>>> Unfortunately it doesn't do anything to protect against leakage in logs or 
>>>> redirects.
>>>> 
>>>> So without the AT using some sort of POP mechanism it is hard to say 
>>>> sending it in a redirect is a good security practice.
>>>> 
>>>> John B.
>>>> 
>>>> On 11/20/2018 4:35 AM, Torsten Lodderstedt wrote:
>>>> 
>>>> Hi Mike, 
>>>>  
>>>> I agree that OIDC hybrid flows offer additional security over the OAuth 
>>>> implicit grant and are used in the wild. On my slides and in the initial 
>>>> version of the new section, we had included the hybrid OIDC flows because 
>>>> of their known token injection countermeasures.
>>>>  
>>>> I nevertheless feel very uncomfortable to recommend those flows and any 
>>>> flow issuing access tokens in the front channel. In the course of the 
>>>> detailed review of the new text we realized two issues: 
>>>>  
>>>> 1) Since the access token is exposed in the URL, such flows possess a 
>>>> significantly higher risk to leak the access token (e.g. through browser 
>>>> history, open redirection and even referrer headers) than the code grant.
>>>> 2) There is no viable way to sender constrain access tokens issued in the 
>>>> front channel. Given the WG decided to recommend use of sender constraint 
>>>> tokens 
>>>> (https://tools.ietf.org/html/draft-ietf-oauth-security-topics-09#section-2..2),
>>>>  it seems contradictory to recommend response types not supporting such an 
>>>> approach. 
>>>>  
>>>> kind regards,
>>>> Torsten. 
>>>>  
>>>> Am 19.11.2018 um 23:13 schrieb Mike Jones 
>>>> <[email protected]>:
>>>>  
>>>> This description of the situation is an oversimplification..  OpenID 
>>>> Connect secures the implicit flow against token injection attacks by 
>>>> including the at_hash (access token hash) in the ID Token, enabling the 
>>>> client to validate that the access token was created by the issuer in the 
>>>> ID Token (which is also the OAuth Issuer, as described in RFC 8414).  
>>>> (Note that this mitigation was described in 
>>>> draft-ietf-oauth-mix-up-mitigation.)
>>>>  
>>>> Given the prevalence of this known-good solution for securing the implicit 
>>>> flow, I would request that the draft be updated to describe this 
>>>> mitigation.  At the same time, I’m fine with the draft recommending the 
>>>> code flow over the implicit flow when this mitigation is not used.
>>>>  
>>>>                                                                 Thank you,
>>>>                                                                 -- Mike
>>>>  
>>>> From: OAuth <[email protected]> On Behalf Of Hannes Tschofenig
>>>> Sent: Monday, November 19, 2018 2:34 AM
>>>> To: oauth <[email protected]>
>>>> Subject: [OAUTH-WG] OAuth Security Topics -- Recommend authorization code 
>>>> instead of implicit
>>>>  
>>>> Hi all,
>>>>  
>>>> The authors of the OAuth Security Topics draft came to the conclusion that 
>>>> it is not possible to adequately secure the implicit flow against token 
>>>> injection since potential solutions like token binding or JARM are in an 
>>>> early stage of adoption. For this reason, and since CORS allows 
>>>> browser-based apps to send requests to the token endpoint, Torsten 
>>>> suggested to use the authorization code instead of the implicit grant in 
>>>> call cases in his presentation 
>>>> (seehttps://datatracker.ietf.org/meeting/103/materials/slides-103-oauth-sessb-draft-ietf-oauth-security-topics-01).
>>>>  
>>>> A hum in the room at IETF#103 concluded strong support for his 
>>>> recommendations. We would like to confirm the discussion on the list.
>>>>  
>>>> Please provide a response by December 3rd.
>>>>  
>>>> Ciao
>>>> Hannes & Rifaat
>>>>  
>>>> IMPORTANT NOTICE: The contents of this email and any attachments are 
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>>>> 
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