What about non-http return uri's, or client-localhost, such as 

  someapp://app/?code=foo

  http://localhost:87345/?code=foo

HTTPS makes sense when you're talking between two web servers, but it
seems to fall apart otherwise. I think SHOULD is appropriate here.

 -- Justin


On Fri, 2011-03-25 at 16:03 -0400, Eran Hammer-Lahav wrote:
> Unless someone has an objection, I'll make the change from SHOULD to MUST.
> 
> EHL
> 
> > -----Original Message-----
> > From: Phil Hunt [mailto:phil.h...@oracle.com]
> > Sent: Friday, March 25, 2011 12:42 PM
> > To: Eran Hammer-Lahav
> > Cc: OAuth WG; Chuck & Mara Mortimore
> > Subject: Re: [OAUTH-WG] WGLC on draft-ietf-oauth-v2-13.txt
> > 
> > Regarding the message: http://www.ietf.org/mail-
> > archive/web/oauth/current/msg05762.html  (sorry I somehow lost the
> > message in my email).
> > 
> > This issue is theft of the authorization code during the redirect.
> > Authenticating the client is an important feature and goes a long way, but 
> > it is
> > not sufficient since in many cases, the client_id/client_secret will likely 
> > be
> > hard coded and relatively easy to deduce (e.g. mobile client apps).  Of 
> > course
> > a strong client authentication won't have this issue. This makes many
> > consumer situations very susceptible to an attack where the authorization
> > code is intercepted.
> > 
> > For more information look at the SAML Artifact issues in section 6.5
> > (specifically stolen artifact, replay, etc) of this document: 
> > http://docs.oasis-
> > open.org/security/saml/v2.0/saml-sec-consider-2.0-os.pdf
> > 
> > There are a number of remediations suggested (small lifetime, single use),
> > but the foundational one is confidentiality of the exchange (TLS). Hence the
> > recommendation that the return of an authorization code be kept secure
> > with a MUST for TLS.
> > 
> > Phil
> > phil.h...@oracle.com
> > 
> > 
> > 
> > 
> > On 2011-03-24, at 7:22 PM, Chuck Mortimore wrote:
> > 
> > >
> > > On Mar 24, 2011, at 6:36 PM, "Eran Hammer-Lahav"
> > <e...@hueniverse.com> wrote:
> > >
> > >>
> > >>> -----Original Message-----
> > >>> From: oauth-boun...@ietf.org [mailto:oauth-boun...@ietf.org] On
> > >>> Behalf Of Chuck Mortimore
> > >>> Sent: Monday, March 14, 2011 6:10 PM
> > >>
> > >>> 1) I'd vote for dropping the following from 1.4.2.   In turn I'd 
> > >>> discuss some
> > of
> > >>> the security considerations, such as difficulty of protecting a
> > >>> client_secret in almost all use-cases of this profile.
> > >>>
> > >>>    "Implicit grants improve the responsiveness and efficiency of some
> > >>>   clients (such as a client implemented as an in-browser application)
> > >>>   since it reduces the number of round trips required to obtain an
> > >>>   access token."
> > >>
> > >> Why drop it? What about it isn't accurate?
> > >
> > > It's accurate, but my opinion is it sends the wrong message.   It's 
> > > clearly the
> > less secure of the response types.  By positioning it as the most performant
> > people may find that attractive and make the wrong security decision.
> > >
> > >
> > >>
> > >>> 2) Section 2.1, we should MUST TLS even for Authorization Code.
> > >>
> > >> Why? What's the attack vector?
> > >
> > > See Phils comment on past experience with artifact bindings.  Spec should
> > default for security always on, and let deployments that don't want to use
> > HTTPs simply be non-conformant.
> > >
> > >>
> > >>> 3) Section 4.1.3 - not clear to me why redirect_uri is REQUIRED
> > >>> since in 4.1.1 it's "REQUIRED unless"
> > >>
> > >> The client should always confirm where the code was sent to. It can omit
> > the redirection is one was provided but should tell the server where it went
> > to. This is more consistent on the verification side, but if the original 
> > flow
> > designers want to chime in (Dick, Brian, etc.?), I'm open to change this.
> > >>
> > >>> 4) Section 4.2.2 - when did we drop refresh_token?     I assume this 
> > >>> goes
> > >>> back to disagreement on how best to handle native clients. I'd
> > >>> prefer it to simply reference 5.1 and leave what is issued up to the
> > >>> security profile of the particular deployment as to what is issued.
> > >>
> > >> -08 June 2010.
> > >>
> > >> This has been decided for a long time. I'm not eager to change it.
> > >
> > > Thanks - I can live with it.  Unfortunately we still seem to be 
> > > fragmenting on
> > the native client approach.   Good topic for IIW I suspect
> > >
> > > -cmort
> > >
> > >>
> > >> EHL
> > >>
> > >>
> > > _______________________________________________
> > > OAuth mailing list
> > > OAuth@ietf.org
> > > https://www.ietf.org/mailman/listinfo/oauth
> 
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