Custom URI Scheme not working in iPhone App for OAuth2

[lokendrasurya]

Description

Hi,
I am trying to implement OAuth2 for my iOS app.
I have defined one urlscheme "lokapp" in my mobile app, and have updated in Redirects in /oauth2/general.
So when I launch my app by adding my custom url scheme in browser "lokapp://", its working as expected and launc my app. Now when I open authUrl it open Authorize page correctly and when I click on Authrize it shows 'Redirect URI is not supported by client'. I am not sure how to fix these. Images for reference

Steps to Reproduce

Register app on discord, add redirect url in dashboard and use same in mobile app and try auth url in mobile app.

Expected Behavior

Url scheme should work and take user back to app.

Current Behavior

User is not getting redirected to app via urlscheme

Screenshots/Videos

Client and System Information

Mobile - iPhone Xs
OS Version - 15.5

[night]

to use protocol urls in redirects you must be using PKCE. you can learn more by reading https://datatracker.ietf.org/doc/html/rfc7636

[Drakyoid]

@night I'm still getting this even with PKCE

@lokendrasurya did you figure it out by any chance?

[irbp]

@Drakyoid, you must include the code_challenge in the generated URL. If no transformation is applied, the code_challenge can be the same as the code_verifier and code_challenge_method can be sent as plain. As a result, your URL should look like this:
https://discord.com/oauth2/authorize?client_id=CLIENT_ID&redirect_uri=lokapp%3A%2F%2F&response_type=code&scope=identify&code_challenge=CODE_CHALLENGE&code_challenge_method=plain

The criteria for generating the code_verifier, as well as how to generate the code_challenge, are included in the specification that @night referred to.