[Openid-specs-ab] App2app authorization/authentication

Joseph Heenan joseph at authlete.com
Thu Oct 3 17:21:45 UTC 2019

Hi Nov,

Replies inline:

> On 3 Oct 2019, at 14:15, nov matake <nov at matake.jp> wrote:
> My use-case isn't app2app, but it's making the mobile apps the self-issued IdP for the backend IdP.
> In that case, the first logged-in app registers a public key to the backend IdP server. After that, when following app send AuthZ request to the server, the server returns another AuthZ request to the app itself. Then the app authenticate user via TouchID etc and acts as self-issued IdP against the backend. Receiving self-issued ID Token, backend IdP authenticates the user and issue code.
> If the app can acts as IdP of the backend IdP, you won't need vendor-specific way to issue code.

I'm quite interested in this. Is this chaining of a self-issued iDP to a backend iDP an already defined protocol I can read more about somewhere?

I'm not sure if it would be the most natural way to do it; the first party app (the bank app) is generally also an oauth client of the backend idp, and the approaches I've seen so far for app2app leverage that existing client relationship. Sadly I'm not aware of anyone that's publicly documented how their implementation of the first party app interacts with the iDP to implement the app2app case.

> I think George has another way in his native app SSO draft.

I don't yet fully understand George's draft, but it only works where the apps are from the same company, so it does not help in the general app2app scenario (where the apps are from different companies) as far as I know.



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