Re: [OAUTH-WG] Confusion on Implicit Grant flow

Bill Burke <bburke@redhat.com> Mon, 09 February 2015 20:50 UTC

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Date: Mon, 09 Feb 2015 15:50:15 -0500
From: Bill Burke <bburke@redhat.com>
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Subject: Re: [OAUTH-WG] Confusion on Implicit Grant flow
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If you don't have a client secret, why is Javascript-based auth code 
grant flow more risky?  We also require SSL and valid redirect URI 
patterns to be registered for the application.  The code can only ever 
be sent to specific URLs and can only be used once.  CORS origin 
validation is also an extra step we do to ensure a rogue javascript app 
isn't making any code-to-token requests.

I'm just trying to figure out if we missed anything...

On 2/9/2015 3:16 PM, John Bradley wrote:
> If you don't have a client secret, or are storing the the client secret in the Javascrypt, then you are probably more at risk using code than implicit.
>
> Implicit is risky because running a OAuth client in the browser is risky.  Using code in that case makes it no better, and arguably worse.
>
> Perhaps I don't understand the environment.
>
> John B.
>
>> On Feb 9, 2015, at 5:05 PM, Bill Burke <bburke@redhat.com> wrote:
>>
>> Due to the security risks of implicit Grant flow, our Javascript adapter only supports  Auth Code Grant flow.  Our IDP has an extra step of allowing you to specify a valid CORS origin for an application.  Anybody see any problems with this kind of approach?  Implicit Grant Flow just seemed really risky to even support as a protocol.
>>
>>
>> On 2/6/2015 4:40 PM, Josh Mandel wrote:
>>> Hi Adam,
>>>
>>> I'm not 100% sure what you're envisioning as an alternative to the
>>> implicit flow, but if I'm reading between the lines of your question
>>> correctly, there are two key parts to the answer, because the implicit
>>> flow is designed to accomplish two key goals (vs. the authorization code
>>> grant):
>>>
>>> 1. Shave off one round-trip HTTP request (the step of exchanging a code
>>> for a token)
>>> 2. Avoid unnecessarily leading the token to the client's back-end web server
>>>
>>> Goal 1 is straightforward. For goal 2: OAuth2's implicit flow takes
>>> advantage of the fact that a URL's "#hash" is not sent to the server
>>> with an HTTP request. By embedding the token in a "#hash", it won't
>>> inadvertently appear in server logs, for example. So with the implicit
>>> flow, I can (for example) statically host a browser-based app at Amazon
>>> S3 without having access tokens leak to Amazon. (Of course, if your
>>> threat model includes a compromised server, then bets are off on this
>>> point.)
>>>
>>> Hope this helps,
>>>
>>>    -Josh
>>>
>>>
>>>
>>> On Fri, Feb 6, 2015 at 1:27 PM, Adam Lewis
>>> <Adam.Lewis@motorolasolutions.com
>>> <mailto:Adam.Lewis@motorolasolutions.com>> wrote:
>>>
>>>     Hi,____
>>>
>>>     __ __
>>>
>>>     Having spent most of my time with native apps and web apps, I now am
>>>     looking at use cases where I need to implement a user-agent-based
>>>     app.  The Implicit flow seems to be optimized for this.____
>>>
>>>     __ __
>>>
>>>     To test my understanding, this flow is for a JavaScript client (or
>>>     similar) executing within a web browser.____
>>>
>>>     __ __
>>>
>>>     At step (a) the client directs the UA to the authorization server,
>>>     but the authorization server redirects the UA to a web-hosted client
>>>     resource.  Why?  It says so that the web-hosted client resources can
>>>     push javascript (or other) back into the UA so it can extract the
>>>     access token in the fragment; but some sort of javascript is already
>>>     running in the browser, since it initiated the authorization request
>>>     in the first place.  So why this extra step?  Why not treat the
>>>     javascript client running in the UA like a native app and handle the
>>>     redirect uri?____
>>>
>>>     __ __
>>>
>>>     I know this was well thought out when the spec was written, so
>>>     trying to figure out what I’m missing?____
>>>
>>>     __ __
>>>
>>>     __ __
>>>
>>>     __ __
>>>
>>>     Tx!
>>>     adam____
>>>
>>>
>>>     _______________________________________________
>>>     OAuth mailing list
>>>     OAuth@ietf.org <mailto:OAuth@ietf.org>
>>>     https://www.ietf.org/mailman/listinfo/oauth
>>>
>>>
>>>
>>>
>>> _______________________________________________
>>> OAuth mailing list
>>> OAuth@ietf.org
>>> https://www.ietf.org/mailman/listinfo/oauth
>>>
>>
>> --
>> Bill Burke
>> JBoss, a division of Red Hat
>> http://bill.burkecentral.com
>>
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>

-- 
Bill Burke
JBoss, a division of Red Hat
http://bill.burkecentral.com