Thanks for chiming in Dima.

Do you reckon it's a good idea to define a code_challenge_method client reg parameter in the OAuth 2.1 spec?

To enable 2.0 -> 2.1 transitions and also give people a concrete and standard compliant way to implement the "REQUIRED or RECOMMENDED" in the OAuth 2.1 spec for code_challenge.

Another spec that deals with PKCE is the OAuth BCP, but to me that's not a optimal place to define a new parameter.


Vladimir Dzhuvinov


On 08/10/2022 04:31, Dima Postnikov wrote:
Hi Vladimir,

Similar issue exists in CDR (Australian Open Banking). PAR and PKCE was added as mandatory to FAPI 1 Advanced profile.

There was a transition period when AS had to support both (potentially).

Also if the same AS is used outside of CDR, this dual support would continue for some implementations.

I don't think this was solved, so your client registration parameter makes sense.



On Wed, Oct 5, 2022 at 5:43 PM Vladimir Dzhuvinov <vladi...@connect2id.com> wrote:

    Has anyone faced the issue how an AS can handle a mix of OAuth 2.0
    and
    2.1 clients regarding PKCE enforcement?

    The new OAuth 2.1 spec makes PKCE required, which is a good security
    measure and fine for an AS where all clients are ready to comply with
    the upgrade. In practice however, it's common for AS deployments
    to have
    a mix of legacy 2.0 and 2.1 clients, and at present OAuth doesn't
    have a
    standard client registration parameter, e.g.
    code_challenge_method, to
    lock a client into using PKCE.

    https://datatracker.ietf.org/doc/html/draft-ietf-oauth-v2-1-02#section-4.1.1

    RFC 8414 defined the code_challenge_methods_supported metadata for
    servers. It would be useful if deployments had a corresponding
    parameter
    for the clients.

    https://www.rfc-editor.org/rfc/rfc8414

    ~ Vladimir

-- Vladimir Dzhuvinov

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