Re: [OAUTH-WG] OAuth 2.1 - require PKCE?

Aaron Parecki <aaron@parecki.com> Wed, 06 May 2020 19:23 UTC

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From: Aaron Parecki <aaron@parecki.com>
Date: Wed, 6 May 2020 12:23:08 -0700
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To: Steinar Noem <steinar@udelt.no>
Cc: Phillip Hunt <phil.hunt@independentid.com>, Mike Jones <Michael.Jones=40microsoft.com@dmarc.ietf.org>, "oauth@ietf.org" <oauth@ietf.org>
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Subject: Re: [OAUTH-WG] OAuth 2.1 - require PKCE?
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Yes, and also, many of those providers very likely already support PKCE
already. Skimming through that list of certified OPs, I recognize many
names there from providers that I know support PKCE.

On Wed, May 6, 2020 at 12:18 PM Steinar Noem <steinar@udelt.no> wrote:

> So, wouldn't a MUST just mean that we would have some OPs that are 2.1
> compliant and some that aren't?
>
> ons. 6. mai 2020 kl. 21:12 skrev Phillip Hunt <phil.hunt@independentid.com
> >:
>
>> Mike,
>>
>> The point of 2.1 is to raise the security bar.
>>
>> Yes it adds new MUST requirements.
>>
>> But what about OIDC would break other than required implementation of
>> PKCE to support 2.1?
>>
>> Eg Would additional signaling be required to facilitate interoperability
>> and migration between versions? Would that be an oauth issue or an OIDC one?
>>
>> Phil
>>
>> On May 6, 2020, at 11:56 AM, Aaron Parecki <aaron@parecki.com> wrote:
>>
>> 
>> > In particular, authorization servers shouldn’t be required to support
>> PKCE when they already support the OpenID Connect nonce.
>>
>> The Security BCP already requires that ASs support PKCE:
>> https://tools.ietf.org/html/draft-ietf-oauth-security-topics-15#section-2.1.1 Are
>> you suggesting that the Security BCP change that requirement as well? If
>> so, that's a discussion that needs to be had ASAP. If not, then that's an
>> implicit statement that it's okay for OpenID Connect implementations to not
>> be best-practice OAuth implementations. And if that's the case, then I also
>> think it's acceptable that they are not complete OAuth 2.1 implementations
>> either.
>>
>>
>>
>>
>>
>>
>> On Wed, May 6, 2020 at 11:21 AM Mike Jones <Michael.Jones=
>> 40microsoft.com@dmarc.ietf.org> wrote:
>>
>>> The disadvantage of requiring PKCE for OpenID Connect implementations is
>>> that you’re trying to add a normative requirement that’s not required of
>>> OpenID Connect deployments today, which would bifurcate the ecosystem.
>>> There are hundreds of implementations (including the 141 certified ones at
>>> https://openid.net/certification/), none of which have ever been
>>> required to support PKCE.  Therefore, most don’t.
>>>
>>>
>>>
>>> Per feedback already provided, I believe that OAuth 2.1 should align
>>> with the guidance already in the draft Security BCP, requiring EITHER the
>>> use of PKCE or the OpenID Connect nonce.  Trying to retroactively impose
>>> unnecessary requirements on existing deployments is unlikely to succeed and
>>> will significantly reduce the relevance of the OAuth 2.1 effort.
>>>
>>>
>>>
>>> In particular, authorization servers shouldn’t be required to support
>>> PKCE when they already support the OpenID Connect nonce.  And clients
>>> shouldn’t reject responses from servers that don’t support PKCE when they
>>> do contain the OpenID Connect nonce.  Doing so would unnecessarily break
>>> things and create confusion in the marketplace.
>>>
>>>
>>>
>>>                                                           -- Mike
>>>
>>>
>>>
>>> *From:* OAuth <oauth-bounces@ietf.org> *On Behalf Of * Dick Hardt
>>> *Sent:* Wednesday, May 6, 2020 10:48 AM
>>> *To:* oauth@ietf.org
>>> *Subject:* [OAUTH-WG] OAuth 2.1 - require PKCE?
>>>
>>>
>>>
>>> Hello!
>>>
>>>
>>>
>>> We would like to have PKCE be a MUST in OAuth 2.1 code flows. This is
>>> best practice for OAuth 2.0. It is not common in OpenID Connect servers as
>>> the nonce solves some of the issues that PKCE protects against. We think
>>> that most OpenID Connect implementations also support OAuth 2.0, and
>>> hence have support for PKCE if following best practices.
>>>
>>>
>>>
>>> The advantages or requiring PKCE are:
>>>
>>>
>>>
>>> - a simpler programming model across all OAuth applications and profiles
>>> as they all use PKCE
>>>
>>>
>>>
>>> - reduced attack surface when using  S256 as a fingerprint of the
>>> verifier is sent through the browser instead of the clear text value
>>>
>>>
>>>
>>> - enforcement by AS not client - makes it easier to handle for client
>>> developers and AS can ensure the check is conducted
>>>
>>>
>>>
>>> What are disadvantages besides the potential impact to OpenID Connect
>>> deployments? How significant is that impact?
>>>
>>>
>>>
>>> Dick, Aaron, and Torsten
>>>
>>>
>>>
>>> ᐧ
>>> _______________________________________________
>>> OAuth mailing list
>>> OAuth@ietf.org
>>> https://www.ietf.org/mailman/listinfo/oauth
>>>
>> _______________________________________________
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>>
>
>
> --
> Vennlig hilsen
>
> Steinar Noem
> Partner Udelt AS
> Systemutvikler
>
> | steinar@udelt.no | hei@udelt.no  | +47 955 21 620 | www.udelt.no |
>