Hi

I'm finding the answers from John interesting but I'm failing to understand why refresh tokens are mentioned in scope of identifying the specific client instances.

AFAIK refresh tokens would only go on the wire, assuming they are supported, when a client exchanges a grant for a new access token.
And when the client uses a refresh token grant.

Was it really about a refresh token grant where the incoming client id and refresh token pair can uniquely identify the actual client instance ? That would make sense.

Something else I'd like to clarify.
John mentions a refresh token is created at the authorization grant initialization time. Would it make any difference, as far as the security properties of a grant are concerned, if refresh token was only created at a grant to access token exchange point of time ?

Thanks, Sergey

On 27/06/14 19:21, John Bradley wrote:
Inline

On Jun 27, 2014, at 1:24 PM, Madjid Nakhjiri <m.nakhj...@samsung.com
<mailto:m.nakhj...@samsung.com>> wrote:

Hi John,
Thank you for your reply. Would appreciate if you consider my inline
comments below and respond again!
R,
Madjid
*From:*John Bradley [mailto:ve7...@ve7jtb.com]
*Sent:*Wednesday, June 25, 2014 5:56 PM
*To:*Madjid Nakhjiri
*Cc:*oauth@ietf.org <mailto:oauth@ietf.org>
*Subject:*Re: [OAUTH-WG] refresh tokens and client instances
In 3.3 It is saying that the refresh token is a secret that the
Authorization server has bound to the client_id, that the
Authorization server effectively uses to differentiate between
instances of that client_id.
Madjid>>If I have 10,000s of devices, each with an instance of the
OAUTH client, but they are all using the same client ID, how would the
server know which token to use for what client? unless when I am
creating a token, I also include something that uniquely identifies
each instance? Don’t I have to use SOMETHING that is unique to that
instance (user grant/ID?)?
When the grant is issued you create and store a refresh token which is
effectively the identifier for that instance/grant combination.
When it comes back on a request to the token endpoint you look up the
grants associated with it.   You also hack that the client_id sent in
the request matches to detect errors mostly)

When the refresh token is generated, it can be stored in a table with
the client_id and the information about the grant.   You could also do
it statelesly by creating a signed object as the refresh token.
Madjid>>agreed, but for the signed object to be self-sustained, again
would I not need something beyond a “population” client_ID? Are we
prescriptive what “information about the grant” is?
You would be creating a bearer token as long as the AS signs it you can
put whatever grant grant info you like in it, that is implementation
specific.  It  could be a list of the scopes granted and the subject.
The spec is silent on the exact programming method that the
Authorization server uses.
Madjid>>Are there any other specs in IETF or elsewhere (OASIS, etc?)
that prescribe token calculation (e.g. hash function, parameters, etc)?

You can look at JOSE and JWT for a way to create tokens
http://tools.ietf.org/html/draft-ietf-oauth-json-web-token
In 3.7 Deployment independent describes using the same client_id
across multiple instances of a native client, or multiple instances of
a Java Script client running in a browsers with the same callback uri.
Since the publishing of this RFC we have also developed a spec for
dynamic client registration so it is possible to give every native
client it's own client_id and secret making them confidential clients.
Madjid>>I would need to look at those specs, however, I thought that
the “confidential client” designation has to do with the client
ability to hold secrets and perform a-by-server-acceptable
authentication. Does dynamic client registration affect client’s
ability in that aspect?

Yes it doesn't require the secret to be in the downloaded instance of
the native app.  It can be populated at first run, changing it from
public to confidential.
Confidential is not just for web servers any more.
There is also a middle ground some people take by doing a proof of
possession for code in native applications to prevent the interception
of responses to the client by malicious applications on the device.
https://datatracker.ietf.org/doc/draft-sakimura-oauth-tcse/
John B.
On Jun 25, 2014, at 8:06 PM, Madjid Nakhjiri <m.nakhj...@samsung.com
<mailto:m.nakhj...@samsung.com>> wrote:


Hi all,
I am new to OAUTH list and OAUTH, so apologies if this is very off-topic.
I am evaluating an OAUTH 2.0 implementation that is done based on bare
bone base OAUTH2.0 RFC. From what I understand, many (or some) client
implementations use a “global ID/secret” pair for all instances of the
client.  Looking at RFC 6819 and there seem to be a whole page on this
topic, if I understand it correctly. So questions:
1)Section 3.7 talks about deployment-independent versus deployment
specific client IDs. I am guessing “deployment-independent” refers to
what I called “global”, meaning if I have the same client with the
same client ID installed in many end devices, that is a deployment
independent case, correct?
2)Section 3.3 on refresh token mentions that the token is secret bound
to the client ID and client instance. Could somebody please point me
to where the token generation and binding is described? Also how is
the client instance is identified?
Thanks a lot in advance,
Madjid Nakhjiri
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