Re: [OAUTH-WG] review comments on draft-ietf-oauth-dyn-reg-11.txt

[Justin Richer <[e-mail]>]

I don't understand which access token is being talked about here -- is 
this the Initial Registration Token? Because you can already do 
everything below. How you get the Initial Registration token is out of 
scope precisely so that the AS can decide what that means. We can add 
language in the lifecycle discussions to bring up the fact that you can 
get this token from an OAuth flow, if you think that'll help clear 
things up.

However, the client doesn't register using the client credential flow at 
all -- it registers using a POST to the registration endpoint, and that 
POST might have an OAuth token attached to it. How the client got that 
OAuth token is, again, out of scope. The client could have done some 
other OAuth flow (any OAuth flow) to get a hold of the token, but how is 
it supposed to get an OAuth token at an AS it hasn't been registered with?

Now, if you're talking about the Registration Access Token, though, that 
makes less sense to me. The client *has* to register first before it can 
get *anything* from the token endpoint. What you're suggesting is that 
all clients be given access to the token endpoint with the client 
credentials flow for the purposes of retrieving the Registration Access 
Token, unless I misread things. You probably don't want the client 
getting other scopes from the token endpoint using the client 
credentials flow, as it'd be an enormous security risk. Thing is, I 
don't think I can implement that level of separation in my app stack, 
and I haven't seen any others that do that. Separating access to 
different endpoints based on OAuth tokens (and the scopes attached) is 
par for the course, though.

Let me run down how it works in our own setup. When a client registers, 
we create a new token (using a TokenServices class) that has a special 
scope, "registration-token". This token is tied to the client_id to 
which it was issued. Clients cannot get tokens with this scope through 
the usual Token Endpoint means, by design. All of the Client 
Configuration Endpoint URLs are protected such that they require access 
from a valid token with the scope "registration-token", and the 
client_id tied to that token MUST match the client_id in the URL. Each 
client is limited to the OAuth flows (grant_types and response_types) 
that it's allowed to call from the token endpoint. All of this is 
specific to our implementation, but I can speak with some authority that 
it's at least implementable this way. This method lets us do public 
clients, confidential clients, public-key clients (that use JWT 
assertions to call the token endpoint), and all different OAuth flows.

If we were to switch things to what you're recommending (using client 
credentials to get the equivalent of the Registration Access Token), I 
would need to issue some form of client credentials to all clients 
(including public clients) and allow all dynamically registered clients 
access to the client_credentials flow at the token endpoint but only if 
they're asking for a registration-token scope, a scope value which 
hasn't been standardized either. I don't think this is even possible in 
my architecture, and it's certainly not desirable.

If we were to switch to having the client credentials used directly on 
the registration endpoint, then you get back into the situation that 
OIDC has already tried, and which failed. I see no reason to try the 
same thing again and expect different results.

I will admit that it was a little strange when I first pulled the 
TokenServices reference into our RegistrationEndpoint class, but doing 
so greatly simplified everything else. I can see the desire to have an 
ideological purity of "all tokens come from the token endpoint", but 
such purity just doesn't help in this case.

  -- Justin

On 05/30/2013 03:31 PM, Phil Hunt wrote:
> For this, I would suggest:
>
> Anonymous, user assisted registration - client registers using the 
> client credential flow but may use an administrator (in the case of 
> web app) or end-user (uid/password) .  Since resource owner would 
> still require separate credential, then the client flow could be used 
> even though we are passing end-user creds. Client obtains access token 
> limited to registering the new entity.
>
> Anonymous unassisted registration (no user present) - the only 
> solution I can come up with is the client self asserted client_id 
> (e.g. UUID) that the token endpoint chooses to accept if scope equals 
> "registration" (or whatever the scope is to be for registration).   
> IMHO this should be avoided.
>
> 3rd Party Assertion - client presents signed assertion in the form of 
> JWT or SAML Bearer assertion and exchanges for an access token. Access 
> is limited to registering a new entity.
>
> The value of the access token being short lived or potentially even 
> single-use (or limited use, like 3 tries), would be to prevent abuse 
> of the registration end-point.
>
> Phil
>
> @independentid
> www.independentid.com <http://www.independentid.com>
> [e-mail] <mailto:[e-mail]>
>
>
>
>
>
> On 2013-05-30, at 11:59 AM, Justin Richer wrote:
>
>> But this still doesn't address clients who don't have a 
>> client_secret. Do they now need one in order to talk to the 
>> registration endpoint? What you're suggesting is that a client use 
>> one set of credentials to get access tokens and another set of 
>> credentials to get registrations. This is certainly no simpler.
>>
>> And this exact functionality was tried, implemented, and rejected as 
>> too complicated by the OpenID Connect community. I don't see why it'd 
>> be any different the second time around.
>>
>> I really don't see any reason to change it.
>>
>>  -- Justin
>>
>> On 05/30/2013 02:56 PM, Phil Hunt wrote:
>>> It's hard to say what the best solution here is regarding 
>>> clarifications until we get clarity on the issue of registration 
>>> access token.
>>>
>>> I don't think using a client credential flow to obtain an access 
>>> token to the registration endpoint is complex. It's the normal flow.
>>>
>>> I concede that you are looking at it as using Client Credential to 
>>> get an access token to get a new Client Credential. But that's not 
>>> really what is happening in terms of protocol here.
>>>
>>> If you take the perspective that the client needs to occasionally 
>>> update registration (e.g. because of a pending credential expiry), 
>>> then it is still simple. You use client credential flow to obtain an 
>>> access token to update registration. Then, from the context of the 
>>> REST API, the client credential is just another piece of JSON data.
>>>
>>> IOW from the REST perspective, it is the registration endpoint that 
>>> is being updated, not the client credential.  The client credential 
>>> is just data in the perspective of REST.
>>>
>>> I think you may be inferring complexity where there really is none.
>>>
>>> Phil
>>>
>>> @independentid
>>> www.independentid.com <http://www.independentid.com/>
>>> [e-mail] <mailto:[e-mail]>
>>>
>>>
>>>
>>>
>>>
>>> On 2013-05-30, at 11:33 AM, Justin Richer wrote:
>>>
>>>> Thanks for clearing up where the confusion was taking place. I had 
>>>> tried to make it clear that these were absolutely standard, opaque 
>>>> OAuth2 bearer tokens and absolutely standard OAuth2-protected 
>>>> endpoints, but if that's not clear that needs to be updated. This 
>>>> is what the text says right now:
>>>>
>>>>     The Client Registration Endpoint MAY accept an Initial Access
>>>>     Token in the form of an OAuth 2.0
>>>>     <http://tools.ietf.org/id/draft-ietf-oauth-dyn-reg-11.html#RFC6749>
>>>>     [RFC6749] access token to limit registration to only previously
>>>>     authorized parties. The method by which the Initial Access
>>>>     Token is obtained by the registrant is generally out-of-band
>>>>     and is out of scope of this specification.
>>>>
>>>>
>>>> And:
>>>>
>>>>     The Client Configuration Endpoint is an OAuth 2.0 protected
>>>>     resource that is provisioned by the server for a specific
>>>>     client to be able to view and update its registered
>>>>     information. The location of this endpoint is communicated to
>>>>     the Client through the registration_client_uri member of the
>>>>     Client Information Response
>>>>     <http://tools.ietf.org/id/draft-ietf-oauth-dyn-reg-11.html#client-info-response>
>>>>     [client-info-response]. The Client MUST use its Registration
>>>>     Access Token in all calls to this endpoint as an OAuth 2.0
>>>>     Bearer Token
>>>>     <http://tools.ietf.org/id/draft-ietf-oauth-dyn-reg-11.html#RFC6750>
>>>>     [RFC6750].
>>>>
>>>>
>>>> Along with the definitions in the introduction:
>>>>
>>>>     Registration Access Token
>>>>         OAuth 2.0 Bearer Token issued by the Authorization Server
>>>>         through the Client Registration Endpoint that is used to
>>>>         authenticate the caller when accessing the Client's
>>>>         registration information at the Client Configuration
>>>>         Endpoint. This Access Token is associated with a particular
>>>>         registered Client.
>>>>     Initial Access Token
>>>>         An OAuth 2.0 Access Token optionally issued by an
>>>>         Authorization Server granting access to its Client
>>>>         Registration Endpoint.
>>>>
>>>>
>>>> I'd welcome any proposed changes to the text to make this clearer.
>>>>
>>>> As to the other suggestion, what you're saying is to use the client 
>>>> credentials to get an access token to get the client credentials 
>>>> ... ? I can see the argument for using the oauth client credentials 
>>>> flow, but I think that's far more complicated than an endpoint 
>>>> saying "here's a token, go use it", personally. Besides, not all 
>>>> clients have credentials at the token endpoint, so it's a bit of a 
>>>> non-starter for a large class of clients.
>>>>
>>>>  -- Justin
>>>>
>>>>
>>>> On 05/30/2013 01:55 PM, Phil Hunt wrote:
>>>>> I see what is happening.
>>>>>
>>>>> I think the reason why I find this spec sooo confusing is that the terms imply new token types when they don't.
>>>>>
>>>>> For example when you say "Registration Access Token" and "Initial Access Token" it implies to me that it is a totally new token type (and in one case it sorta is). When you read the spec (particularly draft 10) it is easy to assume something very different is going on. Hence my push back.
>>>>>
>>>>> It is now clear to me that what you mean to say is *Access Token used for initial access* and *Access Token used for registration*.
>>>>>
>>>>> Why not write the draft to make clear that the registration end point is just a NORMAL OAuth2 Enabled REST endpoint?  That way you can eliminate all of the terminology and lifecycle around access tokens except to say the endpoint is accessed by tokens issued based on the scope "oauth2:registration".
>>>>>
>>>>> That only brings issues with the registration token.  The "Access Token used for registration" seems to have special lifecycle differences.
>>>>> 1.  Issed by reg endpoint as part of successful registration
>>>>> 2.  Has a different lifetime than the client credential (whatever it is).
>>>>>
>>>>> Why not again simplify and follow normal OAuth2 pattern and have the access token issued for registration be *short* lived.  Each time the client wants to either initially register or update its profile it must request a normal access token with scope "oauth2:registration".
>>>>>
>>>>> As for client credential expiry, why not simply require the client to update its registration before it expires?  Why have a long-lived "registration access token" that has to be managed as well?
>>>>>
>>>>> Maybe now I am completely confused?
>>>>>
>>>>> Phil
>>>>>
>>>>> @independentid
>>>>> www.independentid.com
>>>>> [e-mail]
>>>>>
>>>>>
>>>>>
>>>>>
>>>>>
>>>>> On 2013-05-30, at 10:12 AM, Phil Hunt wrote:
>>>>>
>>>>>> The issue is that it has different issuing/lifecycle than normal. E.g. Why is it issued by the registration endpoint?
>>>>>>
>>>>>> Why doesn't the client just request an access token using its client credential for the registration endpoint when it wants to update its profile?
>>>>>>
>>>>>> Phil
>>>>>>
>>>>>> @independentid
>>>>>> www.independentid.com
>>>>>> [e-mail]
>>>>>>
>>>>>>
>>>>>>
>>>>>>
>>>>>>
>>>>>> On 2013-05-30, at 10:08 AM, John Bradley wrote:
>>>>>>
>>>>>>> The reg access token is a OAuth bearer token that is issued as part of the registration response and used to access the new client resource for reads and or updates depending on the permissions.
>>>>>>>
>>>>>>> They are both oauth access tokens.
>>>>>>>
>>>>>>> On 2013-05-30, at 12:02 PM, Phil Hunt<[e-mail]>  wrote:
>>>>>>>
>>>>>>>> Seriously. The new dyn reg draft introduces two new tokens. The initial reg token and the registration access token.
>>>>>>>>
>>>>>>>> As for the latter, the reg access token, my understanding is it has nothing to do with an access token. It is issued *after* registration to allow reg updates.  Right? I know some are confused about this.
>>>>>>>>
>>>>>>>> Phil
>>>>>>>>
>>>>>>>> On 2013-05-30, at 8:52, Phil Hunt<[e-mail]>  wrote:
>>>>>>>>
>>>>>>>>> No different issue. I was concerned about the initial client assertion being passed in as authen cred. It is a signed set of client reg metadata.
>>>>>>>>>
>>>>>>>>> See we are confused. Hence my worry. :-)
>>>>>>>>>
>>>>>>>>> Phil
>>>>>>>>>
>>>>>>>>> On 2013-05-30, at 8:48, John Bradley<[e-mail]>  wrote:
>>>>>>>>>
>>>>>>>>>> I think Phil also had some processing reason why a Token endpoint or RS wouldn't want to tale the authentication as a header, as the processing was easier with them as parameters as they are potentially available to different parts of the stack.   That may have been mostly around RS, but the principal may apply to the token endpoint as well.
>>>>>>>>>>
>>>>>>>>>> On 2013-05-30, at 10:21 AM, Justin Richer<[e-mail]>  wrote:
>>>>>>>>>>
>>>>>>>>>>>>>> "client_secret_post vs client_secret_basic"
>>>>>>>>>>>>>> BASIC and POST are essentially the same just different ways to send the client secret. If an authorization server supports both, both should work for any client. So are both methods treated differently?
>>>>>>>>>>>>> I agree, and this was one of my original arguments for making this field plural (or plural-able), but there hasn't been WG support for that so far.
>>>>>>>>>>>> I'm not arguing to make it plural. I think the authentication method is just "client_secret".
>>>>>>>>>>> That was also an option that was brought up, but in the OIDC WG the counter-argument was (as I recall) that the two are syntactically separate and there's a desire to restrict to a single type, such as disabling client_secret_post. Basically, to make it unambiguous.
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