I'm not sure how to word it exactly but I think Dick has landed on what we ultimately want this to say. Basically that the "request_uri" is intended to be used only once, the client MUST not use it more than once, and that the AS should also treat it as one-time use but may make reasonable accommodations to more gracefully handle redundant authorization requests due to browser reload or similar.
On Sun, Aug 30, 2020 at 4:48 PM Dick Hardt <dick.ha...@gmail.com> wrote: > I don't have the context of the text to respond to the exact wording, but > I think we can state that the client MUST use the "request_uri" only once, > and then explain that the AS may receive duplicate requests if the browser > is reloaded. > > > On Sat, Aug 29, 2020 at 4:24 AM Torsten Lodderstedt < > tors...@lodderstedt.net> wrote: > >> You are making a good point here. The reason we added the one time use >> constraint was the fact the client will include parameters supposed to be >> used only once, e.g. the PKCE code_challenge. For a traditional >> authorisation request, we would recommend the client to use a per >> transaction (== one time use) code_challenge, but PKCE does not require the >> AS to enforce it. Mapping this to PAR means, we SHOULD recommend the client >> to use the request_uri only once but not require the AS to enforce it. >> >> Would the following text work for you? >> >> Since parts of the request content, e.g. the "code_challenge" >> parameter value, is unique to a certain authorization request, >> the client SHOULD use the "request_uri" only once. >> >> I also would move this text to section 4. >> >> > On 27. Aug 2020, at 18:11, Dick Hardt <dick.ha...@gmail.com> wrote: >> > >> > That is not correct. >> > >> > The authorization code one-time-use is directly between the client and >> the AS. The client has a number of mechanisms to ensure it only presents >> the authorization code to the AS once, such as a session that was set when >> the user started at the client. >> > >> > In contrast, in a redirect from the client to the AS, the client loses >> control on how many times the user-agent loads the URL at the AS. >> Additionally, there is unlikely to be an active browser session at the AS, >> so the AS can not easily differentiate between a URL load from the same >> user, or different users. If one-time-use, one of them MUST fail. If the >> two requests happen to be from the same user (because of a reload, which >> the user did because the AS was slow to respond), there is no way for the >> AS to know which of the requests is the one that is current in front of the >> user. While the AS can internally ensure processing of the request once, >> one-time-use would dictate that it provides a failure message to one of the >> requests. >> > >> > /Dick >> > >> > >> > ᐧ >> > >> > On Thu, Aug 27, 2020 at 7:17 AM Justin Richer <jric...@mit.edu> wrote: >> > We already have this same property with authorization codes, and it’s >> managed today reasonably well (in my opinion). If you submit the same >> request URI twice in the same browser (the refresh you’re talking about), >> it shouldn’t start two separate authorization requests, but it would be >> reasonable to detect that the same session attached to the same request URI >> value showed up twice and continue the session as appropriate. >> > >> > None of this is in conflict with “one time use”, in my view, since >> you’re actively detecting the session and source of the value. >> > >> > — Justin >> > >> >> On Aug 26, 2020, at 6:16 PM, Dick Hardt <dick.ha...@gmail.com> wrote: >> >> >> >> I think one-time use may be overly restrictive, and I don't think it >> is the property that we actually want. >> >> >> >> Give the request URI is in a redirect from the browser, there is a >> good chance of a race condition where the same browser request is made more >> than once, for example, while the browser is loading the authorization URL >> at the AS, the user could refresh the page causing the authorization URL to >> be reloaded. Would the reload count as a second use? One could argue it >> either way. >> >> >> >> What I think we want from what I understand, is the request URI MUST >> be unique so that there is no confusion on which request is being >> referenced. >> >> >> >> I did not see anything about the expiry time of the request URI (but I >> did not look super hard). If that is not there, then I think the request >> URI MUST expire in a "short" period of time. >> >> >> >> >> >> >> >> ᐧ >> >> >> >> On Wed, Aug 26, 2020 at 1:45 PM Brian Campbell <bcampbell= >> 40pingidentity....@dmarc.ietf.org> wrote: >> >> Thanks Justin. Just a couple more responses to responses inline below >> (but with lots of content that needs no further discussion removed). >> >> >> >> A TL;DR for the WG is that I'd like to get some wider feedback on the >> question of changing the one-time-use condition on the request_uri from a >> SHOULD to a MUST. >> >> >> >> On Tue, Aug 25, 2020 at 4:57 PM Justin Richer <jric...@mit.edu> wrote: >> >> Hi Brian, just a couple responses inline where it seemed fitting. >> Thanks for going through everything! >> >> — Justin >> >> >> >>> On Aug 25, 2020, at 6:01 PM, Brian Campbell < >> bcampb...@pingidentity.com> wrote: >> >>> >> >>> Thanks for the review and comments Justin. Replies (or attempts >> thereat) are inline below. >> >>> >> >>> >> >>> On Wed, Aug 19, 2020 at 2:06 PM Justin Richer <jric...@mit.edu> >> wrote: >> >>> I’ve done a full read through of the PAR specification, and here are >> my notes on it. >> >>> >> >>> >> >>> ¶2: Of necessity, this spec mixes parameters in the authorization >> endpoint and token endpoint registries into a single request. Is there any >> danger of conflict between them? The registry holds them in one list but >> they could possibly have different semantics in both places.. >> >>> >> >>> I think that technically such danger does exist but that it's highly >> unlikely in practice. Especially because the only token endpoint parameters >> that are relevant to PAR are those that deal with client authentication >> (currently client_secret, client_assertion, and client_assertion_type). I'm >> also not sure what can reasonably be done about it given the way the >> registries are. I guess PAR could update the registration for those three >> (client_secret, client_assertion, and client_assertion_type) to also >> indicate authorization request as a usage location with some commentary >> that it's only for avoiding name collisions. And offer some guidance about >> doing the same for any future client auth methods being defined. But >> honestly I'm not sure what, if anything, to do here? >> >>> >> >>> And yes it is super unfortunate that client auth and protocol >> parameters got mixed together in the HTTP body. I didn't cause that >> situation but I've certainly contributed to it and for that I apologize. >> >> >> >> I think the only perfect solution is to go back in time and fix the >> registries with based on the last decade of knowledge in using them. :P >> >> >> >> For this, I think maybe being very prescriptive about the fact that >> the only parameters from the token endpoint that are allowed here are those >> used for client authentication and that when they show up, they’re >> interpreted as in the token endpoint request not the authorization endpoint >> request. Does that work? >> >> >> >> I think so, yes.. And will work on incorporating some text towards >> that end. >> >> >> >> >> >> >> >>> I don’t see why a request URI with unguessable values isn’t a >> MUST for one-time-use, is there a reason? >> >>> >> >>> The reason AFAIK was to not be overly prescriptive and allow for >> eventually consistent or not atomic storage of the data by not strictly >> requiring the AS to enforce one-time-use. Do you think that's too loose or >> could be worded/explained differently or better? >> >> >> >> I do think it’s too loose and it should be a MUST, and the methods for >> enforcing that “MUST” are going to vary based on the deployments and >> implementations out there. >> >> >> >> >> >> I'd be okay with making it a MUST but think maybe it'd be good to hear >> from a few more people in the WG before committing to that change. >> >> >> >> Can I ask some folks to weigh in on this one? 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