If the challenge is based on distributed authorization server configurations, how would they handle PKCE? I imagine that managing the state for PKCE is not less challenging than managing authorization codes on the server side, preventing reuse of them. With that in mind I am not sure if I follow the given argument. I would prefer to keep MUST as it is today.
On Wed, 13 Oct 2021 at 13:37, Aaron Parecki <aa...@parecki.com> wrote: > HTTPS, because if that's broken then the rest of OAuth falls apart too. > > On Wed, Oct 13, 2021 at 1:36 PM Warren Parad <wpa...@rhosys.ch> wrote: > >> I feel like I'm missing something, what stops just plain old network >> sniffing and replying the whole encrypted payload to the AS and getting >> back a valid token? >> >> Warren Parad >> >> Founder, CTO >> Secure your user data with IAM authorization as a service. Implement >> Authress <https://authress.io/>. >> >> >> On Wed, Oct 13, 2021 at 10:33 PM Aaron Parecki <aa...@parecki.com> wrote: >> >>> Aside from the "plain" method, the PKCE code verifier never leaves the >>> client until it's sent along with the authorization code in the POST >>> request to the token endpoint. The only place it can leak at that point is >>> if the authorization server itself leaks it. If you have things leaking >>> from the authorization server log, you likely have much bigger problems >>> than authorization code replays. >>> >>> Keep in mind that even with the proposed change to drop the requirement >>> of authorization codes being one time use, authorization servers are free >>> to enforce this still if they want. Authorization code lifetimes are still >>> expected to be short lived as well. >>> >>> Aaron >>> >>> >>> On Wed, Oct 13, 2021 at 1:25 PM Pieter Kasselman < >>> pieter.kassel...@microsoft.com> wrote: >>> >>>> Aaron, I was curious what prevents an attacker from presenting an >>>> Authorization Code and a PKCE Code Verifier for a second time if the one >>>> time use requirement is removed. Is there another countermeasure in PKCE >>>> that would prevent it? For example, an attacker may obtain the >>>> Authorization Code and the Code Verifier from a log and replay it. >>>> >>>> >>>> >>>> Cheers >>>> >>>> >>>> >>>> Pieter >>>> >>>> >>>> >>>> *From:* OAuth <oauth-boun...@ietf.org> *On Behalf Of *Aaron Parecki >>>> *Sent:* Wednesday 13 October 2021 18:40 >>>> *To:* Warren Parad <wparad=40rhosys...@dmarc.ietf.org> >>>> *Cc:* Mike Jones <Michael.Jones=40microsoft....@dmarc.ietf.org>; >>>> oauth@ietf.org >>>> *Subject:* [EXTERNAL] Re: [OAUTH-WG] Authorization code reuse and >>>> OAuth 2.1 >>>> >>>> >>>> >>>> Warren, I didn't see you on the interim call, so you might be missing >>>> some context. >>>> >>>> >>>> >>>> The issue that was discussed is that using PKCE already provides all >>>> the security benefit that is gained by enforcing single-use authorization >>>> codes. Therefore, requiring that they are single-use isn't necessary as it >>>> doesn't provide any additional benefit. >>>> >>>> >>>> >>>> If anyone can think of a possible attack by allowing authorization >>>> codes to be reused *even with a valid PKCE code verifier* then that would >>>> warrant keeping this requirement. >>>> >>>> >>>> >>>> --- >>>> >>>> Aaron Parecki >>>> >>>> >>>> >>>> >>>> >>>> On Wed, Oct 13, 2021 at 10:27 AM Warren Parad <wparad= >>>> 40rhosys...@dmarc.ietf.org> wrote: >>>> >>>> Isn't it better for it to be worded as we want it to be, with the >>>> implication being that of course it might be difficult to do that, but that >>>> AS devs will think long and hard about sometimes not denying the request? >>>> Even with MUST, some AS will still allow reuse of auth codes. Isn't that >>>> better than flat out saying: *sure, there's a valid reason* >>>> >>>> >>>> >>>> In other words, how do we think about RFCs? Do they exist to be >>>> followed to the letter or not at all? Or do they exist to stipulate this is >>>> the way, but acknowledge that not everyone will build a solution that holds >>>> them as law. >>>> >>>> >>>> >>>> Let's look at *SHOULD* >>>> >>>> This word, or the adjective "RECOMMENDED", mean that there may exist >>>> valid reasons in particular circumstances to ignore a particular item, but >>>> the full implications must be understood and carefully weighed before >>>> choosing a different course. >>>> >>>> >>>> >>>> I think *recommended* here is not sufficient nor are there valid >>>> reasons. "It's too hard" isn't really a valid reason. Isn't it better in >>>> this case for an AS to not be compliant with the RFC, than it is to relax >>>> this to SHOULD and have lots of AS thinking reusing auth codes is a viable >>>> solution, "because they are a special snowflake where SHOULD should apply". >>>> >>>> >>>> >>>> Are we setting the standard or instead attempting to sustain a number >>>> of "AS that are in compliance with the RFC"? >>>> >>>> >>>> >>>> *Warren Parad* >>>> >>>> Founder, CTO >>>> >>>> Secure your user data with IAM authorization as a service. Implement >>>> Authress >>>> <https://nam06.safelinks.protection.outlook.com/?url=https%3A%2F%2Fauthress.io%2F&data=04%7C01%7Cpieter.kasselman%40microsoft.com%7C64289cdc8a4743659b3108d98e70a5d1%7C72f988bf86f141af91ab2d7cd011db47%7C1%7C0%7C637697436788333255%7CUnknown%7CTWFpbGZsb3d8eyJWIjoiMC4wLjAwMDAiLCJQIjoiV2luMzIiLCJBTiI6Ik1haWwiLCJXVCI6Mn0%3D%7C1000&sdata=lw%2BH1z1Ut9kr6S%2F4aVsPmcErAcZx0eK2WV78OlEl2dU%3D&reserved=0> >>>> . >>>> >>>> >>>> >>>> >>>> >>>> On Wed, Oct 13, 2021 at 7:17 PM Mike Jones <Michael.Jones= >>>> 40microsoft....@dmarc.ietf.org> wrote: >>>> >>>> During today’s call, it was asked whether we should drop the OAuth 2.0 >>>> language that: >>>> >>>> The client MUST NOT use the authorization code >>>> >>>> more than once. If an authorization code is used more than >>>> >>>> once, the authorization server MUST deny the request and SHOULD >>>> >>>> revoke (when possible) all tokens previously issued based on >>>> >>>> that authorization code.” >>>> >>>> >>>> >>>> The rationale given was that enforcing one-time use is impractical in >>>> distributed authorization server deployments. >>>> >>>> >>>> >>>> Thinking about this some more, at most, we should relax this to: >>>> >>>> The client MUST NOT use the authorization code >>>> >>>> more than once. If an authorization code is used more than >>>> >>>> once, the authorization server SHOULD deny the request and >>>> SHOULD >>>> >>>> revoke (when possible) all tokens previously issued based on >>>> >>>> that authorization code.” >>>> >>>> >>>> >>>> In short, it should remain illegal for the client to try to reuse the >>>> authorization code. We can relax the MUST to SHOULD in the server >>>> requirements in recognition of the difficulty of enforcing the MUST. >>>> >>>> >>>> >>>> Code reuse is part of some attack scenarios. We must not sanction it. >>>> >>>> >>>> >>>> -- Mike >>>> >>>> >>>> >>>> _______________________________________________ >>>> OAuth mailing list >>>> OAuth@ietf.org >>>> https://www.ietf.org/mailman/listinfo/oauth >>>> <https://nam06.safelinks.protection.outlook.com/?url=https%3A%2F%2Fwww.ietf.org%2Fmailman%2Flistinfo%2Foauth&data=04%7C01%7Cpieter.kasselman%40microsoft.com%7C64289cdc8a4743659b3108d98e70a5d1%7C72f988bf86f141af91ab2d7cd011db47%7C1%7C0%7C637697436788343208%7CUnknown%7CTWFpbGZsb3d8eyJWIjoiMC4wLjAwMDAiLCJQIjoiV2luMzIiLCJBTiI6Ik1haWwiLCJXVCI6Mn0%3D%7C1000&sdata=ySJjihVbfLJJ85RtjNzEIMSPwe7kLZB8RKT8Ky3fYiA%3D&reserved=0> >>>> >>>> _______________________________________________ >>>> OAuth mailing list >>>> OAuth@ietf.org >>>> https://www.ietf.org/mailman/listinfo/oauth >>>> <https://nam06.safelinks.protection.outlook.com/?url=https%3A%2F%2Fwww.ietf.org%2Fmailman%2Flistinfo%2Foauth&data=04%7C01%7Cpieter.kasselman%40microsoft.com%7C64289cdc8a4743659b3108d98e70a5d1%7C72f988bf86f141af91ab2d7cd011db47%7C1%7C0%7C637697436788343208%7CUnknown%7CTWFpbGZsb3d8eyJWIjoiMC4wLjAwMDAiLCJQIjoiV2luMzIiLCJBTiI6Ik1haWwiLCJXVCI6Mn0%3D%7C1000&sdata=ySJjihVbfLJJ85RtjNzEIMSPwe7kLZB8RKT8Ky3fYiA%3D&reserved=0> >>>> >>>> _______________________________________________ > OAuth mailing list > OAuth@ietf.org > https://www.ietf.org/mailman/listinfo/oauth >
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