Re: [OAUTH-WG] Google's use of Implicit Grant Flow

Dominick Baier <dbaier@leastprivilege.com> Fri, 17 February 2017 18:25 UTC

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From: Dominick Baier <dbaier@leastprivilege.com>
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To: Adam Lewis <adam.lewis@motorolasolutions.com>, Jim Manico <jim@manicode.com>
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Subject: Re: [OAUTH-WG] Google's use of Implicit Grant Flow
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Well - first of all that it uses all the recommend validation techniques

- state validation + protection
- nonce validation
- at_hash validation
- identity token validation
- discovery

+ solid and tested JS code

I don’t see extra value for a JS client in things like “signed requests” -
as I said before - at the end of the day the access token will end up in
the browser. Regardless how secure you made the authentication request in
the first place.


-------
Dominick Baier

On 17 February 2017 at 19:06:23, Jim Manico (jim@manicode.com) wrote:

> Given a solid client library for JS, I think implicit flow is OK to use.

If you can, can you dig deeper here? What is it about this particular
library that makes its use of the OAuth 2 implicit flow secure? Signed
messages? Only supports registered clients? Something else?

Aloha, Jim

On 2/17/17 8:02 AM, Dominick Baier wrote:

Given a solid client library for JS, I think implicit flow is OK to use.

But I agree that there are many “home grown” implementation out there that
are not secure - and the necessary JS code to write a good client is not
necessarily the “pit of success”.

You should give this lib a go (it’s also a certified RP):

https://github.com/IdentityModel/oidc-client-js

Many people argue that handling the protocol and crypto pieces in JS is
problematic (and I agree if no proper lib is used for that) - but at then
end of the day the access token will end up in the browser - and a sloppy
developer (e.g. not using CSP) will always write bad code that might lead
to leaking a token.

-------
Dominick Baier

On 17 February 2017 at 18:43:25, Adam Lewis (
adam.lewis@motorolasolutions.com) wrote:

+1000

We are currently going through internal turmoil over the usage of implicit
grant for ua-based apps.  The webapp case is well understood and the WG has
work in progress to define best practices for native apps.  Having one for
ua-based apps would be HUGELY beneficial



On Fri, Feb 17, 2017 at 11:40 AM, Jim Manico <jim@manicode.com>; wrote:

> Thank you to those answering my question on implicit for JS clients.
>
> The responses so far seem to represent what the security world is saying
> about the implicit grant - keep away from it other than for a few OIDC use
> cases.
>
> Does anyone think it would be valuable to author a brief RFC to give clear
> OAuth 2 recommendations for JavaScript client developers?
>
> I mean - the OAuth 2 body of work just needs a few more RFC's, right? :)
>
> Aloha, Jim
>
>
>
> On 2/17/17 6:03 AM, Sebastian.Ebling@telekom.de wrote:
>
> Same for Deutsche Telekom. Our javascript clients also use code flow with
> CORS processing and of course redirect_uri validation.
>
>
>
> Best regards
>
>
>
> Sebastian
>
>
>
> * Von:* OAuth [mailto:oauth-bounces@ietf.org <oauth-bounces@ietf.org>] *Im
> Auftrag von* Bill Burke
> *Gesendet:* Freitag, 17. Februar 2017 00:14
> *An:* oauth@ietf.org
> *Betreff:* Re: [OAUTH-WG] Google's use of Implicit Grant Flow
>
>
>
> For our IDP [1], our javascript library uses the auth code flow, but
> requires a public client, redirect_uri validation, and also does CORS
> checks and processing.  We did not like Implicit Flow because
>
> 1) access tokens would be in the browser history
>
> 2) short lived access tokens (seconds or minutes) would require a browser
> redirect
>
> I'd be really curious to hear other's thoughts though.
>
> [1] http://keycloak.org
> <https://urldefense.proofpoint.com/v2/url?u=http-3A__keycloak.org&d=DwMD-g&c=q3cDpHe1hF8lXU5EFjNM_A&r=hS3A5qzQnW1hxYBhPrxNW10ESeDiiiRwR8H84JHIXTI&m=IfM1P0zp986kOQNk7-NwlgfRZMq5MppK0kISXhIOF_s&s=YExyuyZO5YNpSvS3mEUG5pjKAjRXXVT8Xvk8hIb-Efw&e=>
>
>
>
>
>
>
>
> On 2/16/17 5:44 PM, Jim Manico wrote:
>
> Hello Folks,
>
> I noticed that Google supports the OAuth 2 Implicit flow for third-party
> JavaScript applications.
>
> https://developers.google.com/identity/protocols/OAuth2UserAgent
> <https://urldefense.proofpoint.com/v2/url?u=https-3A__developers.google.com_identity_protocols_OAuth2UserAgent&d=DwMD-g&c=q3cDpHe1hF8lXU5EFjNM_A&r=hS3A5qzQnW1hxYBhPrxNW10ESeDiiiRwR8H84JHIXTI&m=IfM1P0zp986kOQNk7-NwlgfRZMq5MppK0kISXhIOF_s&s=_Mig-zmCt1y9dZpCece1dqby3VmcZVOu2JPcmAwzwKU&e=>
>
> Isn't this generally discouraged from a security POV? *Is there a better
> OAuth 2 flow for third party SPA applications?*
>
> Aloha,
>
> --
>
> Jim Manico
>
> Manicode Security
>
> https://www.manicode.com <https://urldefense.proofpoint.com/v2/url?u=https-3A__www.manicode.com&d=DwMD-g&c=q3cDpHe1hF8lXU5EFjNM_A&r=hS3A5qzQnW1hxYBhPrxNW10ESeDiiiRwR8H84JHIXTI&m=IfM1P0zp986kOQNk7-NwlgfRZMq5MppK0kISXhIOF_s&s=H8pXLA4TE27vW-gz5Sbr9VOUP-KZMmd-gQ-okH4ohMU&e=>
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--
Jim Manico
Manicode Securityhttps://www.manicode.com