[Openid-specs-fapi] The reasons behind requiring PKCE for confidential clients?

Torsten Lodderstedt torsten at lodderstedt.net
Fri Aug 25 09:15:49 UTC 2017

Hi Nat,

just guessing - the new OAuth security BCP recommends use of PKCE for detecting/preventing code injection attacks. That might be the reason for adding the requirement to the FAPI profile.

I know the hybrid flow („code id_token“) is an alternative countermeasure in the OIDC space. So my question is: will FAPI allow use of pure authz code flow? Then recommending PKCE for code injection makes a lot of sense.

best regards,

> Am 24.08.2017 um 19:43 schrieb Nat Sakimura via Openid-specs-fapi <openid-specs-fapi at lists.openid.net>:
> Hi.
> Current text reads like it is requiring PKCE support even for the confidential client.
> Do you remember the reason for it? Or is it just an editorial error?
> John may have mentioned a potential attack that PKCE could help but I do not quite remember the details....
> If it is an error, then we should fix it for the final.
> Best,
> -- 
> Nat Sakimura
> Research Fellow, Nomura Research Institute
> Chairman of the Board, OpenID Foundation
> _______________________________________________
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> Openid-specs-fapi at lists.openid.net
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