Hi Roman, Thanks again for sticking with me through this one with and associated registry updates with token exchange as well as my temporarily overlooking some needed changes.
-04 is now up <https://tools.ietf.org/html/draft-ietf-oauth-resource-indicators-04> and this time I think I've actually addressed all your comments. On Mon, Jul 22, 2019 at 7:11 AM Roman Danyliw <r...@cert.org> wrote: > Hi Brian! > > > > *From:* Brian Campbell [mailto:bcampb...@pingidentity.com] > *Sent:* Monday, July 22, 2019 8:37 AM > *To:* Roman Danyliw <r...@cert.org> > *Cc:* oauth@ietf.org > *Subject:* Re: [OAUTH-WG] AD Review: > draft-ietf-oauth-resource-indicators-02 > > > > Yes, sorry about that. I realized this yesterday and as tried to write > quickly from from my phone just before my flight took off for Montreal > <https://mailarchive.ietf.org/arch/msg/oauth/2ss3hDa0xPQxaWiW6txj9W-vpqo>, > I'd gotten distracted with the question of what to do with the > registrations and lost track of this fork of the thread. There are indeed > a couple of outstanding bits that need to be addressed in a -04. > > > > I'll change adapt to downscope. > > > Regarding your unanswered questions from below - partially quoted here for > reference: > > > > 'If the initial request was notionally a scope of “all the houses on the > block”, but the server knew that this request was too broad and down-scoped > to “only the corner house”, wouldn’t this actually be worse for privacy?' > -> the idea there is privacy in terms of limiting what one service > potentially leans about other services the user is using. In the houses on > the block case you mentioned, the downscoping prevents the corner house > from learning that the user also accesses the other houses on the block. > > 'I also don’t follow how reducing the scope impacts confidential data.' -> > to be honest, this particular text came as a suggestion from another WG > member on review of an earlier version of the document. So I struggle a bit > to defend/explain it but I think the idea is that in some cases a scope > value itself might contain sensitive data like an account number or > transaction identifier (e.g. something like "acct:123456789" or > "tx:987654321"). This is somewhat uncommon in practice today but does > happen in some situations. The same principal of limiting the scopes > revealed across different services applies here too but with arguably worse > consequences due to the sensitive data within the scope value. It's the > same concept though and I think the mention of confidential data and scope > here in the document is more likely cause confusion than it is to help > anything. As such, I'm proposing to change that sentence as follows to > remove the confidential bit and somewhat better describe the cross-service > scope revealing issue. > > > > "This further improves privacy as scope values give an indication of > what services the resource > owner uses and downscoping a token to only that which is needed for > a particular service can > > limit the extent to which such information is revealed across > different services." > > > > [Roman] Thanks for the explanation relative to my analogy. I agree that > the proposed text above is a lot clearer and it addresses my concern. > > > > Roman > > > > > > On Sun, Jul 21, 2019 at 4:53 PM Roman Danyliw <r...@cert.org> wrote: > > Hi Brian! > > > > Thanks for the update in -03. The item below is the only thing that > remains outstanding. > > > > Thanks, > > Roman > > > > > > *From:* Roman Danyliw > *Sent:* Wednesday, July 17, 2019 6:05 PM > *To:* Brian Campbell <bcampb...@pingidentity.com> > *Cc:* oauth@ietf.org > *Subject:* RE: [OAUTH-WG] AD Review: > draft-ietf-oauth-resource-indicators-02 > > > > > > *From:* Brian Campbell [mailto:bcampb...@pingidentity.com > <bcampb...@pingidentity.com>] > *Sent:* Wednesday, July 17, 2019 4:35 PM > *To:* Roman Danyliw <r...@cert.org> > *Cc:* oauth@ietf.org > *Subject:* Re: [OAUTH-WG] AD Review: > draft-ietf-oauth-resource-indicators-02 > > > > [snip] > > > > (2) Section 2.2. in the sentence "To the extent possible, when issuing > access tokens, the authorization server should adapt the scope value > associated with an access token to the value the respective resource is > able to process and needs to know": > > -- is this language suggesting that the authorization server is modifying > the scope value based on the resource it sees? I'm trying to understand > what "adapt" means, especially in relation to the improved security and > privacy the subsequent sentence suggests. > > > > Perhaps "adapt" wasn't the best choice of word but it's meant to say that > an authorization server with sufficient understanding of what scopes are > applicable to what resources (which won't always be the case or even > possible but sometimes) could limit the scope associated with an access > token (downscoping really) to only the scope that is applicable to the > resource. > > > > Some of the examples (figures 2 - 6) attempt to show, among other things, > a hypothetical case of how this might go down. > > > > In Figure 2 the initial authorization request that's approved has scope of > calendar & contacts and resources https://contacts.example.com/ & > https://cal.example.com/ > > > > A subsequent access token request (Figure 3) has resource > https://cal.example.com/ and the issued access token scope (Figure 4) is > "adapted" to that resource to be only calendar > > > > Another subsequent access token request (Figure 5) has resource > https://contacts.example.com/ and the issued access token scope (Figure > 6) is downscoped based on that resource to be only contacts > > > > Would it be easier to understand if the word "downscope" was used rather > than "adapt"? > > > > [Roman] Using “downscope” does work for me. It captures that the server > is going to reduce the scope (and certainly not expand it). > > > > > -- (Depending on the above) Is there a security consideration here for the > server relative to confidential scope values and how they might be modified? > > > > I'm not sure, to be honest. Downscopping when possible and to the extent > possible is usually a good idea (least privilege and all that) but I think > maybe I'm missing your point/question. > > > > [Roman] Yes, least privilege was part of it and I think the text above > gets at it. However, the other part is the relationship with the next > sentence in the paragraph, “This further improves privacy as scope values > give an indication of what services the resource owner uses and it improves > security as scope values may contain confidential data”. If the initial > request was notionally a scope of “all the houses on the block”, but the > server knew that this request was too broad and down-scoped to “only the > corner house”, wouldn’t this actually be worse for privacy? I also don’t > follow how reducing the scope impacts confidential data. > > > > > > > *CONFIDENTIALITY NOTICE: This email may contain confidential and > privileged material for the sole use of the intended recipient(s). Any > review, use, distribution or disclosure by others is strictly prohibited. > If you have received this communication in error, please notify the sender > immediately by e-mail and delete the message and any file attachments from > your computer. Thank you.* > -- _CONFIDENTIALITY NOTICE: This email may contain confidential and privileged material for the sole use of the intended recipient(s). Any review, use, distribution or disclosure by others is strictly prohibited. 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