Hi Sergey, 

thanks for your input. 

On Feb 26, 2013, at 2:36 PM, Sergey Beryozkin wrote:

> Hi Hannes
> On 25/02/13 12:46, Hannes Tschofenig wrote:
>> Hi all,
>> 
>> I just submitted an updated version of the 
>> draft-ietf-oauth-v2-http-mac-03.txt.
>> 
> 
> It definitely has more interesting content (about architecture, session keys, 
> etc) - this is really useful IMHO.
> 
> What I'm not really understanding is why a 2-way TLS transport for the 
> session key is not even considered.

Could you explain how this would look like? 

> Instead this uber-complex (in the context of this spec, IMHO) JWT thing is 
> there once again. I appreciate why it may be the case, primarily to do with 
> reusing the work done around JWT and having some common/recommended access 
> token representation, but disallowing a basic bearer token be 'enhanced' with 
> MAC over two-way TLS seems like not ideal at all IMHO.

Note that JWT is used only for the access token encoding. 

> To be honest, I'm not sure why would anyone use JWT+MAC instead of just JWE,

Actually, the authorization server encrypts the access token using JWE and the 
client uses MAC. 
So, using JWT + MAC is actually not possible since the security mechanisms are 
used by different entities: the MAC is used by the client and the access token 
protection is accomplished by the authorization server. 

> in cases when people are really comfortable with doing JWT. I guess we may be 
> talking now about better security characteristics, but this will help a very 
> limited audience as compared to a wider one which can use Bearer+MAC over 
> 2-way TLS, straightforward, very cheap effort to get started.
> 

Ciao
Hannes

> just my 2c
> Thanks, Sergey
> 
>> I would like to point out that this is **discussion input** -- not agreed 
>> content. Anything in the document is subject to change!
>> You also may notice that there are a few questions in the writeup.
>> 
>> I was trying to more specific about some of the design aspects that folks 
>> had proposed during the last few months.
>> I have also re-submitted the draft-tschofenig-oauth-hotk, which includes a 
>> TLS and a JSON-based solution approach.
>> 
>> In general, the open questions still seem to be related to
>> * Key distribution: What should be described in a document? What is 
>> mandatory to implement?
>> * Selective header field protection: This is something that was brought 
>> forward in discussions and I have included a proposal of how this could look 
>> like.
>> * Channel Binding: Functionality is also included to deal with 
>> man-in-the-middle attacks against TLS. There are, however, two types of 
>> channel bindings defined in RFC 5929. Are both needed? If not, which one 
>> should be selected?
>> * Integrity protection and data origin authentication in both directions: 
>> The current writeup allows the protection to be extended to messages beyond 
>> the initial request. This also offers key confirmation by the server and 
>> protection of any responses.
>> 
>> Writing the text I also noticed that I do not quite understand how nested 
>> JWT documents are supposed to look like. For example, how do I encrypt the 
>> mac_key carried inside the JWT plus add a signature of all other fields? 
>> Currently, I have just encrypted the entire payload.
>> 
>> I hope to have some discussions prior to the IETF meeting so that we have a 
>> more fruitful discussion at the face-to-face meeting.
>> 
>> Ciao
>> Hannes
>> 
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