One of the things I do not like about a MTI key transport mechanism if we put it in the token is that there will be some systems that already have a per user secret provisioned and we'll be forcing data duplication. If if the encrypted token already includes any random component that could easily be used as part of the signing key. So I feel like this will fatten up the token, potentially a lot.
If we don't put it in the token this problem is WAY harder. ________________________________ From: Hannes Tschofenig <hannes.tschofe...@gmx.net> To: Antonio Sanso <asa...@adobe.com> Cc: Hannes Tschofenig <hannes.tschofe...@gmx.net>; William Mills <wmills_92...@yahoo.com>; IETF oauth WG <oauth@ietf.org> Sent: Tuesday, February 12, 2013 3:06 AM Subject: Re: [OAUTH-WG] Minutes from the OAuth Design Team Conference Call - 11th February 2013 The transport of the session key from the authorization server is described in Section 5.1 and is called "mac_key". The mechanism to transport the session key from the authorization server to the resource server is not yet described in the document. This has historical reasons: OAuth 1.0 did not separate the authorization server from the resource server in the way OAuth 2.0 does. Ciao Hannes On Feb 12, 2013, at 12:28 PM, Antonio Sanso wrote: > Hi Hannes, > > how this session key "differs" from the key described in the current draft > [0]? > > Thanks and regards > > Antonio > > [0] http://tools.ietf.org/html/draft-ietf-oauth-v2-http-mac-02 > > On Feb 12, 2013, at 10:44 AM, Hannes Tschofenig wrote: > >> Hi Bill, >> >> On Feb 12, 2013, at 11:27 AM, William Mills wrote: >> >>> Is key distribution how AS and PR share keys for token >>> encryption/decryption or specifically about the keys for the HOK tokens? >>> >> In order for the client to compute the keyed message digest it needs to have >> the session key. This session key is sent from the authorization server to >> the client and everyone on the call agreed that this has to be standardized. >> >> The resource server who receives the message from the client also needs to >> have the session key to verify the message. How the resource server obtains >> this session key was subject for some discussion on the call. I presented >> three different ways of how the resource server is able to obtain that key. >> We have to decide on one mandatory-to-implement mechanism. The open issue is >> which one? >> >>> For the MAC token spec, I don't actually care whether we use JSON or now, >>> but I'm in full agreement that we do NOT duplicate any HTTP info into the >>> JSON. Just signatures of that stuff. >>> >> I believe the folks on the call also agreed with you on that aspect that the >> content of the HTTP message should not be replicated in the JSON payload >> itself. >> >> Ciao >> Hannes >> >>> From: Hannes Tschofenig <hannes.tschofe...@gmx.net> >>> To: IETF oauth WG <oauth@ietf.org> >>> Sent: Tuesday, February 12, 2013 1:10 AM >>> Subject: [OAUTH-WG] Minutes from the OAuth Design Team Conference Call - >>> 11th February 2013 >>> >>> Here are my notes. >>> >>> Participants: >>> >>> * John Bradley >>> * Derek Atkins >>> * Phil Hunt >>> * Prateek Mishra >>> * Hannes Tschofenig >>> * Mike Jones >>> * Antonio Sanso >>> * Justin Richer >>> >>> Notes: >>> >>> My slides are available here: >>> http://www.tschofenig.priv.at/OAuth2-Security-11Feb2013.ppt >>> >>> Slide #2 summarizes earlier discussions during the conference calls. >>> >>> -- HTTP vs. JSON >>> >>> Phil noted that he does not like to use the MAC Token draft as a starting >>> point because it does not re-use any of the work done in the JOSE working >>> group and in particular all the libraries that are available today. He >>> mentioned that earlier attempts to write the MAC Token code lead to >>> problems for implementers. >>> >>> Justin responded that he does not agree with using JSON as a transport >>> mechanism since this would replicate a SOAP style. >>> >>> Phil noted that he wants to send JSON but the signature shall be computed >>> over the HTTP header field. >>> >>> -- Flexibility for the keyed message digest computation >>> >>> From earlier discussion it was clear that the conference call participants >>> wanted more flexibility regarding the keyed message digest computation. For >>> this purpose Hannes presented the DKIM based approach, which allows >>> selective header fields to be included in the digest. This is shown in >>> slide #4. >>> >>> After some discussion the conference call participants thought that this >>> would meet their needs. Further investigations would still be useful to >>> determine the degree of failed HMAC calculations due to HTTP proxies >>> modifying the content. >>> >>> -- Key Distribution >>> >>> Hannes presented the open issue regarding the choice of key distribution. >>> Slides #6-#8 present three techniques and Hannes asked for feedback >>> regarding the preferred style. Justin and others didn't see the need to >>> decide on one mechanism - they wanted to keep the choice open. Derek >>> indicated that this will not be an acceptable approach. Since the resource >>> server and the authorization server may, in the OAuth 2.0 framework, be >>> entities produced by different vendors there is an interoperability need. >>> Justin responded that he disagrees and that the resource server needs to >>> understand the access token and referred to the recent draft submission for >>> the token introspection endpoint. Derek indicated that the resource server >>> has to understand the content of the access token and the token >>> introspection endpoint just pushes the problem around: the resource server >>> has to send the access token to the authorization server and then the >>> resource server gets the result back (which he then >> a >>> gain needs to understand) in order to make a meaningful authorization >>> decision. >>> >>> Everyone agreed that the client must receive the session key from the >>> authorization server and that this approach has to be standardized. It was >>> also agreed that this is a common approach among all three key distribution >>> mechanisms. >>> >>> Hannes asked the participants to think about their preference. >>> >>> The questions regarding key naming and the indication for the intended >>> resource server the client wants to talk to have been postponed. >>> >>> Ciao >>> Hannes >>> >>> >>> _______________________________________________ >>> OAuth mailing list >>> OAuth@ietf.org >>> https://www.ietf.org/mailman/listinfo/oauth >>> >>> >> >> _______________________________________________ >> OAuth mailing list >> OAuth@ietf.org >> https://www.ietf.org/mailman/listinfo/oauth >
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