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Area

oidc

Describe the bug

Based on OAuth2.1 Client Secret, when an Identity Provider has Client authentication as Client secret sent as basic auth basic authentication encoding must be : based64_encode(url_encode(client_id) + ":" + url_encode(client_secret)).

Keycloak need to respect it and send the basic authenticator encoding based on OAuth 2.1

Version

26.3.5

Regression

[ ] The issue is a regression

Expected behavior

Basic authentication encoding is : based64_encode(url_encode(client_id) + ":" + url_encode(client_secret)).

Actual behavior

Basic authentication encoding is : based64_encode(client_id + ":" +client_secret).

How to Reproduce?

Create an OIDC Identity Provider with Basic Authenticator and client_id including colon (fe https://www.keycloak.org/). Observe the basic authentication that Keycloak sends.
When you will try to login, authentication will be failed due to wrong client credentials.
Keycloak client will try to authenticate with client_id = 'https'

Anything else?

No response