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

Steinar Noem <steinar@udelt.no> Wed, 06 May 2020 19:18 UTC

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From: Steinar Noem <steinar@udelt.no>
Date: Wed, 6 May 2020 21:18:28 +0200
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To: Phillip Hunt <phil.hunt@independentid.com>
Cc: Aaron Parecki <aaron@parecki.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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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>om>:

> 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

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