Re: [OAUTH-WG] Pete Resnick's No Objection on draft-ietf-oauth-assertions-17: (with COMMENT)
Thanks for your review and feedback, Pete. Replies are inline below... On Tue, Oct 14, 2014 at 2:42 PM, Pete Resnick presn...@qti.qualcomm.com wrote: Pete Resnick has entered the following ballot position for draft-ietf-oauth-assertions-17: No Objection When responding, please keep the subject line intact and reply to all email addresses included in the To and CC lines. (Feel free to cut this introductory paragraph, however.) Please refer to http://www.ietf.org/iesg/statement/discuss-criteria.html for more information about IESG DISCUSS and COMMENT positions. The document, along with other ballot positions, can be found here: http://datatracker.ietf.org/doc/draft-ietf-oauth-assertions/ -- COMMENT: -- 3 - Assertions used in the protocol exchanges defined by this specification MUST always be protected against tampering using a digital signature or a keyed message digest applied by the issuer. Why is that? Aren't you using assertions over a protected channel (as required by the spec) and therefore not need to sign the assertions? Indeed, why would a self-issued Bearer Assertion need to be signed at all? Does that even make sense? Yes, assertions are sent over a protected channel, which does provide integrity protection for the transport form client to AS and also gives server authentication. But it doesn't provide client authentication, which is kind of the point of the Client Authentication part of this draft. And for authorization the signing or MACing is what authenticates the issuer of the assertion - sometimes the issuer is the client but often the issuer will be a 3rd party system. I do agree with you in one specific case that, if the client is trusted to be the assertion issuer and the client is properly authenticated, then an unsigned assertion could be reasonably used as an authorization grant. But it's a fairly rare and very specific case. And one that can be accommodated in other ways. So it's not worth introducing the complexity and potential security problems that having the signature be option would bring. 4.1 - grant_type REQUIRED. The format of the assertion as defined by the authorization server. The value MUST be an absolute URI. That MUST is unnecessary. It's just definitional from 6749, 4.5 (which, as it happens, doesn't use 2119 language for this). s/MUST/will Makes sense. assertion REQUIRED. The assertion being used as an authorization grant. Specific serialization of the assertion is defined by profile documents. The serialization MUST be encoded for transport within HTTP forms. It is RECOMMENDED that base64url be used. The MUST seems weird here. Are you saying that the profile could not possibly have a serialization for an assertion that did not require further encoding? But the RECOMMENDED seems downright wrong: Either an implementer *needs* to know the encoding independently of the profile, and therefore this needs to be a MUST, or the profile is going to describe the encoding, which could be base64url or could be something else, and the implementation will do whatever the profile says. If you really want to say something here, I suggest replacing the last two sentences with: If the assertion is going to be transported within HTTP forms, the profile document needs to describe what (if any) encoding will be needed to do so. The base64url encoding is widely implemented and therefore suggested. In reading it again, I agree with you that it's weird and not appropriate here. In fact the JWT profile itself does not require any further encoding. Barring any objection, I suggest that the last two sentences just be removed. So it would just be, assertion REQUIRED. The assertion being used as an authorization grant. Specific serialization of the assertion is defined by profile documents. scope [...] As such, the requested scope MUST be equal or lesser than the scope originally granted to the authorized accessor. s/MUST/will (unless you explain whether it's the server or the client that's supposed to be obeying that MUST, and for what reason) They are both supposed to obey it - the client shouldn't ask for more and the server will reject the request, if it does. Is will more appropriate than MUST here? Or maybe a non 2119 should? If the scope parameter and/or value are omitted, the scope MUST be treated as equal to the scope originally granted to the authorized accessor. The Authorization Server MUST limit the scope of the issued access token to be equal or lesser than the scope originally granted to the authorized accessor. In the first sentence, is this
Re: [OAUTH-WG] Pete Resnick's No Objection on draft-ietf-oauth-assertions-17: (with COMMENT)
Assertions used in the protocol exchanges defined by this specification MUST always be protected against tampering using a digital signature or a keyed message digest applied by the issuer. Why is that? Aren't you using assertions over a protected channel (as required by the spec) and therefore not need to sign the assertions? Indeed, why would a self-issued Bearer Assertion need to be signed at all? Does that even make sense? Yes, assertions are sent over a protected channel, which does provide integrity protection for the transport form client to AS and also gives server authentication. But it doesn't provide client authentication, which is kind of the point of the Client Authentication part of this draft. And for authorization the signing or MACing is what authenticates the issuer of the assertion - sometimes the issuer is the client but often the issuer will be a 3rd party system. I do agree with you in one specific case that, if the client is trusted to be the assertion issuer and the client is properly authenticated, then an unsigned assertion could be reasonably used as an authorization grant. But it's a fairly rare and very specific case. And one that can be accommodated in other ways. So it's not worth introducing the complexity and potential security problems that having the signature be option would bring. In other words, the assertion must be protected against tampering *by the party that presents the assertion*. That is a significant point, and you should say it. Barry ___ OAuth mailing list OAuth@ietf.org https://www.ietf.org/mailman/listinfo/oauth
Re: [OAUTH-WG] Pete Resnick's No Objection on draft-ietf-oauth-assertions-17: (with COMMENT)
Fair point. I'll add some text saying that in the next revision. On Wed, Oct 15, 2014 at 5:18 PM, Barry Leiba barryle...@computer.org wrote: Assertions used in the protocol exchanges defined by this specification MUST always be protected against tampering using a digital signature or a keyed message digest applied by the issuer. Why is that? Aren't you using assertions over a protected channel (as required by the spec) and therefore not need to sign the assertions? Indeed, why would a self-issued Bearer Assertion need to be signed at all? Does that even make sense? Yes, assertions are sent over a protected channel, which does provide integrity protection for the transport form client to AS and also gives server authentication. But it doesn't provide client authentication, which is kind of the point of the Client Authentication part of this draft. And for authorization the signing or MACing is what authenticates the issuer of the assertion - sometimes the issuer is the client but often the issuer will be a 3rd party system. I do agree with you in one specific case that, if the client is trusted to be the assertion issuer and the client is properly authenticated, then an unsigned assertion could be reasonably used as an authorization grant. But it's a fairly rare and very specific case. And one that can be accommodated in other ways. So it's not worth introducing the complexity and potential security problems that having the signature be option would bring. In other words, the assertion must be protected against tampering *by the party that presents the assertion*. That is a significant point, and you should say it. Barry ___ OAuth mailing list OAuth@ietf.org https://www.ietf.org/mailman/listinfo/oauth
Re: [OAUTH-WG] Pete Resnick's No Objection on draft-ietf-oauth-assertions-17: (with COMMENT)
On 10/15/14 6:06 PM, Brian Campbell wrote: Thanks for your review and feedback, Pete. Replies are inline below... Thanks for addressing the comments, including Barry's followup. Just on the questions: On Tue, Oct 14, 2014 at 2:42 PM, Pete Resnick presn...@qti.qualcomm.com mailto:presn...@qti.qualcomm.com wrote: scope [...] As such, the requested scope MUST be equal or lesser than the scope originally granted to the authorized accessor. s/MUST/will (unless you explain whether it's the server or the client that's supposed to be obeying that MUST, and for what reason) They are both supposed to obey it - the client shouldn't ask for more and the server will reject the request, if it does. Is will more appropriate than MUST here? Or maybe a non 2119 should? Ah, so you're saying that a client could conceivably (either purposely or accidentally) try to sneak through a larger scope than it should, and the client MUST NOT do that, and the server MUST reject if it gets one. OK, that makes sense. (I do tend to like active MUSTs -- the foo MUST do X or the bar MUST NOT do Y -- but this is probably OK as is.) Here and throughout: s/non-normative example/example (As far as I know, there are no other kinds in IETF documents.) I thought I picked that language up from some other draft or RFC but I'm now not sure where it came from and can't easily find other examples of the same thing. So I am happy to remove the non-normative throughout, if it is already understood and/or not customary to say so. Yeah, we've seen other RFCs with such language. I've whined about it in the past. Some authors roll their eyes at me. You are welcome to roll your eyes if you like, but I find such text silly. :-) Thanks for the rest of the planned changes. Looks good. pr -- Pete Resnickhttp://www.qualcomm.com/~presnick/ Qualcomm Technologies, Inc. - +1 (858)651-4478 ___ OAuth mailing list OAuth@ietf.org https://www.ietf.org/mailman/listinfo/oauth
