[Openid-specs-ab] Response types clarification

Justin Richer jricher at mitre.org
Tue Feb 21 22:07:05 UTC 2012

On not being OpenID: I would say that if you're not getting an ID Token 
back, you're not doing OpenID Connect, you're just doing OAuth2. If you 
happen to be doing OAuth2 against something that has a User Info 
Endpoint, that's fine, but it's not binding you to the user's session. 
It's definitely the right thing to avoid mucking about with OAuth2 
wherever possible.

But the question being addressed below was "how do I know when to 
include the ID Token?", and I think it should break down as follows 
(assuming user grants access and all else is validated):

- if the request to the token endpoint includes the scope 'openid', 
throw the id token into the JSON response
- if the request to the authorization endpoint is for type 'token' and 
the scope includes 'openid', throw the id token into the fragment
- if the request to the authorization endpoint is for type 'code 
id_token' and the scope includes 'openid', throw the id token into the 
fragment along with the code (again, avoids the query parameter leakage 
issue brought up before)
- if the request to the authorization endpoint is for type 'code token' 
and the scope includes 'openid', throw the id token and the access token 
into the fragment along with the code

What I'm saying is that #3 above is an odd special case that could be 
subsumed by #4 above. This all gets rid of the need for the id_token 
response type entirely. Apart from being a breaking change, I don't see 
how this doesn't cover the use cases described below.

  -- Justin

On 02/21/2012 04:48 PM, John Bradley wrote:
> On 2012-02-21, at 5:41 PM, Justin Richer wrote:
>> John, thanks for the background. This leaves me with a major question 
>> though:
>>> That was the way we originally had it.   Later on people thought that using the OAuth multi-response type was more OAuth friendly.
>>> Originally if you had the scope openid:
>>> 1 response_type=code   both code and id_token were query encoded in the response
>> Maybe I'm missing something, but in the "code" flow, you don't get 
>> back an id_token in that response. You get back a code, and that code 
>> can be exchanged for an access token and an id_token, since you asked 
>> for something that includes the "openid" scope. From Standard, 
>> section 2.2.1:
>> code
>>     When supplied as the value for the response_type parameter, a
>>     successful response MUST include an Authorization Code as defined
>>     in the OAuth 2.0 specification. Both successful and error
>>     responses MUST be added as parameters to the query component of
>>     the response. All tokens are returned from the Token Endpoint.
>>     Authorization Servers MUST support this response_type. 
>> So the whole issue of query-encoding the id_token isn't even an 
>> option here. It *is* an option if you're asking for something akin to 
>> "code id_token", but that wasn't on the table. In the current spec, 
>> those are both defined as fragment encoded anyway.
> Having id_token returned in the front channel was one of the early 
> must haves from the major IdP.   Given that in the early days we 
> returned id_token query encoded in the front channel and from the 
> token endpoint.
> It looked like a hack.   There was no way to change the semantics of 
> code.   With the multi token response type change around draft 19 of 
> OAuth I think,  Google and Facebook decided that was the best way to 
> indicate the response_type, rather than overloading the semantics of 
> scopes.
> Currently if you ask for code it is defined in the OAuth 2 core spec 
> and you get code back just as you would expect, the same goes for 
> token.  We avoided reinterpreting the OAuth spec as much as possible.
> The permissible way to ask for multiple tokens is the return type and 
> that is what we are currently doing.
>>> 2 response_type=token  both access_token and id_token were fragment encoded.
>>> There was no way to just get code or access_token, and no way to get just id_token.
>> The former, yes, there is: just don't include the "openid" scope. The 
>> latter, no. But if you ask for a token with just the "openid" scope 
>> and don't ask for any other permissions, the server *could* give you 
>> a null or empty or otherwise useless access token there, if it wanted 
>> to. I agree that if this is a real and viable use case, then it 
>> should be a separate kind of response_type, but I'm not seeing that 
>> right now.
> The thing is that if you don't include the openid scope you are not 
> doing openid Connect and our spec has nothing to say in the matter.   
> So removing the openid scope so that the IdP can't tell if it is a 
> connect request or some other OAuth request is not a real option.
> The only thing I might change at this point on response_type if I had 
> a do over would be to use underscores rather than spaces to reduce 
> confusion.   Other than that I don't think we have a problem.
> In reality a client will only use a single response type appropriate 
> for it.   They are not dynamically changing these things.   If you 
> want code as a query parameter just ask for 'code' all the options are 
> available to the clients without confusing it with the scopes.
>>> It was simpler I will give you that.
>>> It is a bit different from adding id_token to the token endpoint in that there is no OAuth mechanism for controlling the response from the endpoint.  I suppose the alternative would have been to add an extra parameter to the token endpoint request to say if you wanted a id_token.
>> No, again, that's what the scope already handles. If we didn't have a 
>> standardized scope value, then I'd agree with this.
> Again if you remove the openid scope it is not openid.  That is the 
> scope that asks for the user_info endpoint and the user_id.
> John
>>  -- Justin
>>>>> - just using "token" instead of all combinations of id_token and token ?
>>>>> The response type "token" could cause the OP to return both the id_token and the access token in the fragment, which is similar to the response of the tokens endpoint. I know this would return tokens the client is potentially not interested in. But this seems to be accepptable for the code response type.
>>>> I actually rather like this approach. It keeps the question of whether or not you want OpenID confined to the value of the 'scope' field (that is, presence of an 'openid' value in there), and it makes serialization of the ID Token just a part of the access token output, like the code flow with the token endpoint. Of course we still have to profile how it gets encoded, but it's ultimately another field in the token output.
>>>> -- Justin
>>>>> Am 20.02.2012 20:44, schrieb John Bradley:
>>>>>> Response types are single values.   (I am starting to hate Erin's compromise)
>>>>>> The response types are documented in:http://openid.bitbucket.org/oauth-v2-multiple-response-types-1_0.html
>>>>>> The response types "code id_token",  "id_token token", and "code id_token token"  MUST return a id_token and the response SHOULD be fragment encoded.
>>>>>> Now you are asking yourself why is that SHOULD be fragment encoded as opposed to MUST be fragment encoded.
>>>>>> The reason for that is that the response_type registration is leaving wiggle room to use the same response type with post message as well.
>>>>>> For that to work the client would need to register a JS Origin and DOM Channel Names(or pick a fixed strings).  We did stub in post message configuration parameters, but removed them due to there not being a OAuth spec yet.
>>>>>> Probably more than the yes you were looking for, but the history provides some perspective.
>>>>>> John B.
>>>>>> On 2012-02-20, at 3:52 PM, Torsten Lodderstedt wrote:
>>>>>>> Hi John,
>>>>>>> thanks for the clarification.
>>>>>>> So all response types containing the string value "id_token" cause the authorization server to directly return a id_token (along with all other parameters) to the client via fragment?
>>>>>>> regards,
>>>>>>> Torsten.
>>>>>>> Am 20.02.2012 19:48, schrieb John Bradley:
>>>>>>>> Inline
>>>>>>>> On 2012-02-20, at 3:30 PM, Torsten Lodderstedt wrote:
>>>>>>>>> Hi all,
>>>>>>>>> I'm trying to catch up with the Implementors Draft and need some advice from the group.
>>>>>>>>> Is it correct that "code" is the only response type, which is delivered to the client via URI query parameter? For all other response types, the response parameters are encoded within the URI fragment.
>>>>>>>> Yes
>>>>>>>>> Furthermore, is the client always issued an access token _and_ an id_token for scope "openid" and response type "code"?
>>>>>>>> The response from the Authorization server is code as was asked for.
>>>>>>>> The Token endpoint includes id_token in it's response as an extra parameter.
>>>>>>>> So strictly speaking Yes id_token is always issued if the scope is 'openid'  (scope is a single value with spaces, so don't say includes) and the response_type is code.
>>>>>>>> However the response type is code and only code.
>>>>>>>> The id_token is only returned if code is exchanged at the token endpoint for and access_token and id_token.
>>>>>>>> So I suppose you could avoid getting id_token by not exchanging code, but I don't think anyone is going to think that is a good idea.
>>>>>>>> The problem is that response)type only controls what comes back from the Authorization endpoint, and not the token endpoint.
>>>>>>>> The only option we found was overloading a scope to change the behaviour of the token endpoint to return the extra value.
>>>>>>>> The token endpoint response is direct, so size is not a big issue.  It was simpler to always return it from that endpoint than create a complicated way of asking for it from the token endpoint.
>>>>>>>> Worst case the response is a bit bigger, but the client ignores the extra parameter.
>>>>>>>> John B.
>>>>>>>>> thanks in advance,
>>>>>>>>> Torsten.
>>>>>>>>> _______________________________________________
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>>>>>>>>> Openid-specs-ab at lists.openid.net
>>>>>>>>> http://lists.openid.net/mailman/listinfo/openid-specs-ab
>>>>> _______________________________________________
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